Table of Contents
Executive Summary
List of Tables
List of Figures
Acronyms, Abbreviations, and Units of Measure
1.0 Introduction
1.1 Previous Activities
1.2 Guidance Documents
2.0 Identification of Exposure Pathways and Potentially Exposed
Populations
3.0 Constituents of Potential Concern
3.1 Data Sets
3.1.1 Surface Soil
3.1.2 Groundwater
3.1.3 Surface Water
3.1.4 Sediment
3.1.5 Fish Tissue
3.1.6 Deer Tissue
3.1.7 Data QA/QC and Validation
3.2 Screening Procedures
3.3 Identification of COPCs
4.0 Exposure Assessment
4.1 Definition of Terms
4.2 Exposure Point Concentrations
4.3 Quantification of Exposure
4.3.1 Current Conditions
4.3.2 Future Conditions
4.4 Exposure Equations and Parameters
4.4.1 Inhalation of Airborne Dusts and Particulates
4.4.2 Incidental Ingestion of Soil
4.4.3 Dermal Contact with Soil
4.4.4 Ingestion of Groundwater
4.4.5 Dermal Contact with Groundwater
4.4.6 Inhalation of Groundwater
4.4.7 Incidental Ingestion of Surface Water
4.4.8 Dermal Contact with Surface Water
4.4.9 Incidental Ingestion of Sediment
4.4.10 Dermal Contact with Sediment
4.4.11 Ingestion of locally Caught Fish
4.4.12 Radionuclide Exposure
5.0 Toxicity Assessment
6.0 Risk Characterization
6.1 Non-Cancer health Hazards
6.1.1 Groundwater
6.1.2 Soil
6.1.3 Fish
6.1.4 Surface Water
6.1.5 Sediment
6.2 Non-Radiological Cancer Risks
6.2.1 Groundwater
6.2.2 Soil
6.2.3 Fish
6.2.4 Surface Water
6.2.5 Sediment
6.3 Total non-radiological Cancer Risks and Health Hazards
6.3.1 Off-Site Resident Recreational Anglers
6.3.2 Off-Site Recreational Anglers
6.3.3 Off-Site Residents
6.3.4 On-Site Trespassers
6.3.5 Future On-Site Resident Recreational Anglers
6.3.6 Future On-site Recreational Anglers
6.3.7 Future On-Site Residents
6.4 Radiological Risk Assessment
6.4.1 Ingestion of Surface Water
6.4.2 Deer Meat Consumption
6.4.3 Fish Consumption
6.4.4 Ingestion of Groundwater
6.4.5 Ingestion of Soil
6.4.6 Ingestion of Sediment
6.4.7 Inhalation of Airborne Dust and Particulates
6.4.8 External Gamma Radiation
6.4.9 Total Radiological Dose and Risk Assessment
6.7 Uncertainty
6.7.1 Analytical Data
6.7.2 Exposure Point Concentrations
6.7.3 Exposure Factors
6.7.4 Uncertainties in Toxicity Assessment
7.0 Summary and Recommendations
8.0 References
Appendix A - Risk Assessment Protocols for Operable Unit V Human Health Risk
Assessment
Appendix B - RESRAD Output
Executive Summary
This risk assessment evaluates the potential human health risks to people that may now, or at some time in the future, be exposed to various contaminants that have been identified in the upstream areas of the Peconic River as a result of past operations at the U.S. Department of Energy’s Brookhaven National Laboratory. The assessment, which considers potential exposures for a reasonably maximally exposed individual under each of several scenarios, concludes that a human health risk from these contaminants may exist now and in the future if no action were to be taken. It is important to note that there are several uncertainties identified within the assessment that have a significant impact on the results of the calculations and should therefore be considered in determining any future actions.
The scenarios evaluated include the future resident living near the Peconic River, current off-site residents housed along the Peconic River, current residents and non-residents who are recreational anglers and hunters, and current on-site trespassers. Subsets of these scenarios include adult exposures, older child exposures and young child exposures as appropriate. This risk assessment augments prior risk assessments that have been completed with regard to the Peconic River. These areas are commonly referred to as Operable Unit V and the related documents are available in the Administrative Record.
The risks evaluated in this assessment are of two types. The first is a total cancer risk from all contaminants considered. The acceptable level of risk based upon the United States Environmental Protection Agency (EPA) is an excess risk of cancer that is not more than one in ten thousand to one in one million greater than that of the general population. The second type of risk is a non-cancer risk from the various contaminants through various pathways. This is measured through the use of a hazard quotient that is derived primarily through the use of EPA guidance documents. Additionally, for radionuclide exposure, a dose assessment that estimates the total radiological exposure is presented. Regulatory guidance addressing radionuclide contamination is often expressed in terms of annual dose. In using the guidance provided by the EPA, as well as input from other regulatory agencies such as the New York State Department of Environmental Conservation, the risk values calculated in this report represent a conservative estimate of risk for a reasonably maximally exposed individual.
This risk assessment proved to be particularly challenging because of the uncertainties that became evident as the assessment process was employed. In developing data sets for estimating risk, several difficulties were encountered where conservative assumptions in the absence of data were required or where reasonable assumptions could not be made leaving potential data gaps. The number and significance of the uncertainties associated with this risk assessment demanded that a broad spectrum of exposure scenarios be included. Incorporating a number of scenarios representing various populations created a range of risk estimates for consideration in determining the most appropriate remedial actions to be taken. Given the uncertainties, and the conservatism built into this assessment, the estimated risk for average individuals is likely to be much less than that calculated in this assessment.
This risk assessment will best be used as a tool to evaluate the risk under various scenarios, coupled with an objective measure (such as analysis of fish tissue contaminant concentration) to evaluate the success of remedial actions while minimizing ancillary damage to the wetlands and the surrounding ecosystem. Examples of the uncertainties incorporated into this risk assessment follow.
Among the pathways with the greatest risk, the most significant uncertainties revolve around fish, the influential contributor to the risk calculations for human health in the upstream Peconic River. There is an absence of data on actual fish consumption rates for fishing populations in the upstream portions of the Peconic River. This data gap results from a number of factual observations about the portion of the river upstream of Schultz Road. Over the past 35 years, the river upstream of Schultz Road has been dry in a cyclic fashion; often the river does not contain sufficient water for significant periods of time to support fish populations. Recent flow data indicate that this area was essentially dry about 30 to 40 percent of the time. Consequently, fishing in this area can only be sporadic at best. However, it is likely that portions of upstream sections of the river will carry water during the early portion of the summer months, which is typically a peak fishing period. During the periods in which the fish population can be sustained, particularly upstream on the BNL site, the fish are often much smaller than an edible or legal keeping size for fishermen.
Two additional studies are recommended and underway to reduce the uncertainty concerning the Peconic River water level variability and the impact of water level on the fish consumption pathway. The first study is an evaluation of historic Peconic River water levels in the upstream section of the river and a prediction of the range and frequency of future water levels. The second evaluation is a characterization of the fish habitat between the BNL Sewage Treatment Plant and Schultz Road and a prediction of potential fish biomass at low, mid, and high water levels. The results of these two studies will be placed in the Administrative Record on completion. The fish biomass evaluation will be placed in the Administrative Record as an attachment to this Risk Assessment, which may be modified if necessary.
Nonetheless, the assumptions in the risk assessment include a recreational angler taking sufficient fish from this part of the river to consume about 20 pounds a year per person (25 grams per day on average), and it assumes all 20 pounds per year is taken exclusively from this area of the Peconic River. Again, in the absence of data, this number is derived from a standard recreational angler consumption survey conducted by the EPA. It is not based upon Peconic River specific conditions. This number is accepted as valid for two reasons: there are no other data upon which to base risk, and there are insufficient fisherman observed in this area of the Peconic to develop a statistically valid survey.
Another key factor of uncertainty related to this aspect is the assumption that the upper section of the river is connected to the downstream section of the river by continuously flowing water so that the fish population can be replenished from the downstream section. Through observation over the past 35 years, the upper portion of the river often does not have sufficient water to support this assumption. This — coupled with an assumption that the water level in the future may be higher than present conditions thus leading to continuous flooding and a sustained fish population — leads to the 25 gram per day fish consumption value being used in this risk assessment. Additionally, a consumption rate of 6.5 grams per day (approximately five pounds per year) was also evaluated.
In addition to the uncertainties about the productivity of the river for recreational anglers, there is another aspect to the fish that creates sufficient uncertainty as to warrant notation. The fish samples in the upstream parts of the Peconic River have often been of insufficient size to evaluate them as edible portions. This has required the use of whole-body fish tissue data to represent the edible portion for human consumption. This adds a degree of uncertainty to the risk assessment. In particular, consumption of PCBs will be overestimated, though consumption of mercury may be underestimated.
Current off-site residents or recreational fishers may obtain fish from the Peconic River from on-site accessible areas of BNL. Data for contaminants in edible fish tissue from this area of the Peconic River are under-represented in the data set used for the off-site receptors. Since the concentrations of contaminants, particularly polychlorinated biphenyls (PCBs), were generally greater above the gauging station (maximum in whole fish samples of 6 parts per million [ppm] PCBs) than below the gauging station (maximum in edible fish tissue samples of 0.16 ppm PCBs), the exposure concentrations used to represent the edible fish tissue concentrations available to off-site receptors may have been underestimated. An analysis of the uncertainty due to this lack of data indicate that, for the off-site receptors, the non-cancer health hazard from fish consumption may be up to 2.5 times greater than calculated or the cancer risk from fish consumption may be almost ten times greater, but the health hazard and cancer risk would still be much less than that reported for a potential future on-site resident or recreational fisher.
Exposures to contaminants were assumed to potentially occur through incidental ingestion, dermal contact, and inhalation of soils and sediment. Exposure was also assumed to occur through incidental ingestion of surface water, dermal contact with surface water, consumption of groundwater as a drinking water source, dermal contact with groundwater during bathing, inhalation of volatile organic compounds from groundwater during showering, consumption of locally caught fish, consumption of locally caught deer, and external gamma radiation from cesium-137.
Constituents of potential concern that were assessed are: inorganics (arsenic, cadmium, chromium, copper, cyanide, iron, manganese, mercury, and thallium), volatile organic compounds (1,1-dichloroethene, 1,2-dichloroethane, ammonia, chloroform, tetrachloroethene, and trichloroethene), pesticides (DDD, DDE, DDT and alpha-chlordane), PCBs (Aroclor-1242, Aroclor-1254, and Aroclor-1260), polycyclic aromatic hydrocarbons (benzo(a)pyrene and benzo(b)fluoranthene), and radionuclides (americium-241, cesium-137, cobalt-60, lead-210, plutonium-238, plutonium-239/240, strontium-90, tritium, uranium-233/234, uranium-235, and uranium-238).
The evaluation of total cancer risks revealed that the total excess cancer risks to current off-site adult (2.1´ 10-4) and young child (1.3´ 10-4) residents, adult (1.4´ 10-4) and young child (1.4´ 10-4) resident angler/hunters, and adult non-resident angler/hunters (1.4´ 10-4) that consume locally caught fish and deer were greater than the EPA acceptable range for excess risk of cancer of 1´ 10-4 to 1´ 10-6. That is, for a person meeting the conditions of the reasonably maximal exposed individual, the risk is greater than one in ten thousand. This is due to arsenic and trichloroethene in groundwater when used as a drinking water source and household supply, from cesium-137 in deer meat, and from polychlorinated biphenyls (PCB) in fish. Total excess cancer risks for off-site older children and off-site non-resident angler hunter younger children were all within the EPA acceptable range (9.0´ 10-5 for older child resident angler/hunter, 2.5´ 10-5 for young child non-resident angler/hunter, 3.1´ 10-5 for older child non-resident angler/hunter, and 6.2´ 10-5 for older child resident non-angler/hunter). This is also true of the current on-site trespasser with a total excess cancer risk of 1.2´ 10-6.
The total cancer risk for on-site exposure to a future resident consuming locally caught fish or an on-site angler/hunter who meets the conditions of the reasonably maximally exposed individual, exceeds the acceptable risk range established by the EPA. This level of risk is mostly based upon exposure to PCBs, as measured in whole fish, as well as exposure to cesium-137 in deer meat. The total cancer risks for these on-site receptors are 1.2´ 10-3 for adult resident angler/hunter, 5.4´ 10-4 for young child resident angler/hunter, 4.6´ 10-4 for older child resident angler/hunter, 1.1´ 10-3 for adult non-resident angler/hunter, 4.9´ 10-4 for young child non-resident angler/hunter, 4.4´ 10-4 for older child non-resident angler/hunter, 3.2´ 10-4 for adult resident non-angler/hunter, 2.8´ 10-4 for young child resident non-angler/hunter, and 1.2´ 10-4 for older child resident non-angler/hunter.
The total cancer risk for both current off-site and potential future on-site receptors not consuming locally caught fish or deer was significantly less. All were within the acceptable risk values established by the EPA.
In determining non-cancer risk, a hazard quotient value of 1.0 or less indicates that the risk is within an acceptable range; an organ or system specific value above 1.0 indicates that a person exposed consistent with the assumptions made may have an excess health hazard beyond what is considered acceptable by EPA criteria. The total non-cancer health hazard quotients for the following recreational angler adult and children scenarios, based on the assumptions for the reasonably maximally exposed individuals, exceeded 1.0: 5.0 for current off-site adult resident angler/hunter, 13 for current off-site young child resident angle/hunter, 9.1 for current off-site older child resident angler/hunter, 3.4 for current off-site adult non-resident angler/hunter, 7.9 for current off-site young child non-resident angler/hunter, 6.8 for current off-site older child non-resident angler/hunter, 62 for future on-site adult resident angler/hunter, 150 for future on-site young child resident angle/hunter, 120 for future on-site older child resident angler/hunter, 62 for future on-site adult non-resident angler/hunter, 140 for future on-site young child non-resident angler/hunter, and 120 for future on-site older child non-resident angler/hunter The primary contributor to these health hazards is the mercury as measured in edible fish tissue and PCBs as measured in whole-body fish tissue from on-site fish. Effects from mercury are primarily to the central nervous system, and effects from PCBs are generally to the immune system. The total non-cancer health hazard quotients for current off-site residents that are not recreational angler/hunters but may still consume locally caught fish are 2.5 for the adult, 9.6 for the young child, and 4.1 for the older child.
In addition to the contaminants in fish, arsenic and trichloroethene in groundwater contribute to the hazard quotient for the current off-site children. The hazard quotient for resident young children based on arsenic in groundwater in the off-site area is 1.7 and based on trichloroethene in groundwater is 2.2. However, arsenic in groundwater may likely be due to naturally occurring arsenic in soil and not related to site activities. Additionally, the concentrations of arsenic in groundwater are below the New York State groundwater standard of 25 micrograms per liter (m g/L) (6 New York Codes, Rules, and Regulations [NYCRR] Part 703), as well as the EPA’s established drinking water standard for arsenic of 10 m g/L. Arsenic may be related to naturally occurring arsenic within the soil of the region, and is not suspected to be site related. Trichloroethene has been detected in several monitoring well samples, as well as residential well samples, above the groundwater standard of five m g/L. An apparent trichloroethene plume has been identified in the Peconic River area. The groundwater in the area is classified as Class GA (fresh groundwaters) by the NYSDEC (6 NYCRR Part 701). Groundwater in the vicinity of the Peconic River is being addressed under Operable Unit (OU) V Record of Decision (BNL 2001a). To assure future safe drinking water, residents along the river in this area have been provided connection to the public water supply, and groundwater monitoring will continue. No further remedial action objectives are recommended for groundwater under OU V based on the results of this risk assessment.
Though this risk assessment evaluated exposure to cesium-137 through the consumption of potentially contaminated deer meat, it is likely that the elevated concentrations detected in deer are related more to other BNL on-site sources than to the Peconic River or OU V sources. Other sources that could result in cesium-137 in deer are being, or have been, remediated as part of Operable Unit I through the remediation of contaminated soils, which is designed to reduce the deer contamination. BNL also has an active deer monitoring program in place through which cesium-137 levels in deer are measured both on site and in off site areas. No further remedial action objectives that address deer contamination are recommended under OU V based on the results of this risk assessment.
In conclusion, for the reasonably maximally exposed individual, one who meets the assumptions made in this assessment with the established uncertainties, there is a potential for human health risk that exceeds the criteria established by the EPA. Therefore, it is recommended that remedial action objectives to address these risks be established and implemented on a timely basis to reduce this potential for risk to human health. Recommendations for additional actions include:
1.0 Introduction
This risk assessment evaluates the potential risks to human health for defined populations that may now, or at some time in the future, be exposed to various contaminants that have been identified in the upstream areas of the Peconic River as a result of past operations at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory (BNL). The assessment, which considers potential exposures for a reasonably maximally exposed individual under each of several scenarios, concludes that a human health risk from these contaminants may exist now and in the future if no action were to be taken. It is important to note that there are several uncertainties identified within the assessment that have a significant impact on the outcome of the calculations and should therefore be considered in determining any future actions.
The risks evaluated in this assessment are of two types. The first is a total cancer risk from all contaminants considered. The acceptable level of risk based upon United States Environmental Protection Agency (EPA) guidelines is an excess risk of cancer that is not more than one in ten thousand to one in one million greater than that of the general population. Cancer risks due to radiological contaminants are discussed in Section 6.4, cancer risk due to non-radiological contaminants are discussed in Section 6.2 and Section 6.3. The total cancer risk due to both radiological and non-radiological contaminants is presented in Section 6.5.
Additionally, for radionuclide exposure, a dose assessment that estimates the total radiological exposure is also presented in Section 6.4. Regulatory guidance addressing radionuclide contamination is often expressed in terms of annual dose.
The second type of risk is a non-cancer health hazard from the various contaminants through various pathways. This is measured through the use of a hazard quotient that is derived primarily through the use of EPA guidance documents. Non-cancer risks are discussed in Section 6.1.
In using the guidance provided by the EPA, as well as input from other regulatory agencies such as the New York State Department of Environmental Conservation (NYSDEC), the risk values calculated in this report represent a conservative estimate of risk for a reasonably maximally exposed individual. A list of these guidance documents is provided in Section 1.2.
This risk assessment proved to be particularly challenging because of the uncertainties that became evident as the assessment process was employed. In developing data sets for estimating risk, several difficulties were encountered where conservative assumptions in the absence of data were required. The number and significance of the uncertainties associated with this risk assessment demanded that a broad spectrum of exposure scenarios be included. Incorporating a number of scenarios representing various populations created a range of risk estimates for consideration in determining the most appropriate remedial actions to be taken. Given the uncertainties, and the conservatism built into this assessment, the estimated risk for average individuals is likely to be much less than that calculated in this assessment. These uncertainties are discussed in Section 6.7.
This risk assessment can best be used as a tool to evaluate the risk under various scenarios, coupled with an objective measure (such as analysis of fish tissue contaminant concentration) to evaluate the success of remedial actions while minimizing ancillary damage to the wetlands and the surrounding ecosystem.
Report Organization
Section 1.0 provides an introduction to this report. Section 2.0 presents an identification of the exposure pathways and potentially exposed populations that are addressed the baseline human health risk assessment. Section 3.0 addresses the constituents of potential concern (COPCs). The exposure assessment is presented in Section 4.0. This includes the quantification of exposure concentrations for the COPCs in the applicable media and the presentation of exposure factors for applicable. In Section 5.0, the toxicity of the COPCs is addressed, and the cancer slope factors and non-carcinogenic reference doses that are used in the risk assessment are presented. The risk characterization is presented in Section 6.0. This includes the presentation of media-specific non-carcinogenic health hazards and carcinogenic risks, an assessment of radiological risk and annual dose, and an evaluation across all media and pathways. Section 7.0 provides a summary and recommendations for remedial action objectives, and the references cited are included in Section 8.0.
1.1 Previous Activities
The Operable Unit V (OU V) Remedial Investigation (RI) Report (IT 1998) presented information on the nature and extent of contamination within OU V, including the Peconic River, and assessed the risk to human health and the environment. Since that report, additional samples of groundwater, surface water, soils, sediment, and fish have been collected for chemical and/or radiological analysis. Additional radionuclide data were reported in the Operable Unit V Plutonium Contamination Characterization and Radiological Dose and Risk Assessment Report (IT 2000), and a baseline human health risk assessment was prepared to present an estimation of potential carcinogen risks to human populations resulting from exposure to radionuclides associated with OU V currently and at some time in the future if no remedial action were to be taken at OU V. Risks from chemical contamination were not addressed in that report. Additionally, numerous sediment samples have since been collected from the Peconic River and measured for cesium-137 as part of the recent additional sediment characterization investigations. These data were presented in the Operable Unit V – Peconic River Analytical Results from the Supplemental Sediment Sampling Program Conducted September 4 – October 12, 2001 (BNL 2002).
Some of the receptors addressed in this risk assessment had been addressed in other risk assessments (IT 1998, 2000). The following summarizes those results as they pertain to the receptors to be addressed in the proposed risk assessment.
The 1998 RI Report evaluated an on-site trespasser in the current land-use scenario. The total non-radiological carcinogenic risk was 8 ´ 10-7, within the EPA guidance range for carcinogenic risk. This risk was mostly due to arsenic in sediment, soil, and surface water. The total non-carcinogenic hazard was estimated as 0.14, with half of this due to incidental ingestion of sediment with mercury contamination. This health hazard is well within the EPA guidance for non-carcinogenic hazard of unity.
A future on-site resident was also evaluated in the RI Report. However, this resident was assumed to be housed at the sand filter beds/berms area of the Sewage Treatment Plant (STP), not along the Peconic River. The total carcinogenic risk to adult and child future residents was estimated as 5 ´ 10-5 and 3 ´ 10-5, respectively. The risk was predominantly from the ingestion of arsenic from all media, but mostly in groundwater. The total non-carcinogenic hazard to adult and child future residents was estimated at 1.8 and 4.9, respectively. The groundwater ingestion pathway contributed most to this hazard with most of that from manganese.
The RI Report included an evaluation of cancer risks and non-cancer health hazards from occasional consumption of fish from either on-site or off-site areas. The cancer risk and non-cancer health hazard for future on-site residents consuming on-site fish were both found to be above acceptable levels, with polychlorinated biphenyl (PCBs) being the principle risk driver. The cancer risk and non-cancer health hazard based on occasional consumption of off-site fish was found to be within acceptable levels; however, the off-site fish used in the risk assessment did not include any fish from off-site areas near the site, but included fish from Schultz Road and downstream to Peconic Lake and Forge Pond. The current off-site data set is more conservative because it only uses fish from on-site near North Street and downstream only as far as Schultz Road.
A subsequent radiological risk assessment (IT 2000) included a future on-site resident and an off-site resident in the upstream section of the Peconic River, as well as other receptors. The increased lifetime cancer risk to the future on-site resident was estimated as 3 ´ 10-4. However, this risk was based almost entirely on external gamma radiation from the sand filter beds/berms area. (Cleanup of this contamination will be completed during the calendar year 2002.) The future on-site resident in the proposed risk assessment is assumed to be housed along the Peconic River, not on the sand filter beds/berms area. The increased lifetime cancer risk to the off site resident was estimated as 6.7 ´ 10-5, which is within the EPA range of 1 ´ 10-6 to 1 ´ 10-4.
The objective of this risk assessment is to reassess the human health risks related to contamination in the Peconic River as a result of the additional chemical and radiological analyses. The scope of this risk assessment was developed following review by and discussions with EPA, NYSDEC, New York State Department of Health (NYSDOH), and Suffolk County Department of Health Services (SCDHS) personnel. The scope has been designed in an effort to address the concerns of those agencies so as to present a responsible and credible assessment. The scope of this risk assessment was presented in the Risk Assessment Protocols for Operable Unit V Human Health Risk Assessment, which is attached as Appendix A to this report. The tables from that report are not included within Appendix A since the tables are presented elsewhere in this document as part of the risk assessment report. (Note that the table numbers presented in the protocol document do not correspond with the table numbers for those tables as they are presented in the risk assessment report.) The Protocol document has been revised to provide additional clarity deemed necessary during the review process. In particular the following areas have been revised:
Additional information regarding procedures that were not sufficiently detailed within the Protocol document have been incorporated within the text of the risk assessment report.
In compliance with Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) requirements, this risk assessment was prepared to present an estimation of potential carcinogenic risks and non-carcinogenic hazards to human populations resulting from exposure to chemical constituents originating from the Peconic River area of OU V, now and at some time in the future, if no remedial action were or will be taken (e.g., groundwater exposure is still assumed although public water hookups are in place in the affected area).
1.2 Guidance Documents
Procedures and methodologies used in the risk assessment are based on the following guidance:
2.0 Identification of Exposure Pathways and Potentially Exposed Populations
Risk assessments must first identify what populations may be affected by potential risks in a specific area, both now and in the future.
Currently, the on-site portion of the Peconic River is primarily forest and wetlands. There are no on-site residents in the area, so residential exposure for on-site residents was not considered under the current land-use scenarios. There are, however, residents off-site along the section of the Peconic River from the site boundary to Schultz Road; those residents were considered in this assessment. Additionally, trespassers onto the site may currently be exposed to on-site contaminants, and were considered.
The future land-use assessment considered an on-site resident along the Peconic River at some point after loss of institutional controls for the site. BNL’s future land use plan (BNL 1995) presents the projected land use for a period of 20 years. The potential timing of the postulated closure and the level of development are indeterminate. Consistent with its application in other Operable Units at BNL (e.g., OU I), it is assumed that, at a minimum, it would be 50 years before the site were released and available for residential zoning. However, it is important to note that the assumption of the 50-year time frame is not implicit to any of the risk evaluations presented in this report. For example, exposure to radionuclides and chemicals by future residents, though in the future, is conservatively evaluated considering current concentrations and does not account for radioactive decay or other processes that may lead to natural attenuation.
Additionally, off-site residents may be potentially exposed to contaminants in the upstream section of the off-site Peconic River. However, because the potential risks to future off-site residents would be based on current data, the future off-site resident is not addressed separately.
Exposure to contaminants in groundwater may occur through drinking the water when using groundwater as a drinking water source, through inhalation of volatile contaminants when using groundwater to shower, and through dermal contact when using groundwater to bathe.
Exposure to contaminants in soil near the river may occur through direct contact, through inhalation of airborne soil particulates, through incidental ingestion of soil during daily activities, and (for radionuclides) through external radiation. The potential for exposure to contaminants through consumption of homegrown fruits and vegetables was evaluated for consideration in the risk assessment. The soils assessed in this risk assessment are assumed to represent a narrow area along the Peconic River. Their extent and location would not result in a significant exposure pathway through the consumption of homegrown fruit and vegetables; thus, this pathway was not evaluated in the risk assessment.
Exposure to contaminants in sediment in the river may occur through direct contact, through inhalation of airborne particulates when the river is dry, through incidental ingestion of sediment during activities at the river, and (for radionuclides) through external radiation when sediment is exposed.
Exposure to contaminants in surface water in the Peconic River may occur through direct contact and through incidental ingestion when engaged in activities at the river.
Exposure to contaminants in fish and deer may occur through the consumption of meat from locally caught fish and deer. Though contaminants in deer meat may be the result of exposures elsewhere on the BNL site — which are being addressed through remediation at other Operable Units — the exposure to contaminants in deer meat is addressed as part of the total exposure to receptors associated with the Peconic River.
The table below summarizes the potential exposure pathways and the population considered in this risk assessment. Tables 1.1 and 1.2 present this information in greater detail as part of the site conceptual model.
Exposure Scenarios Considered
|
Current off-site resident |
Future on-site resident |
Current Off-Site Resident fisher/ |
Future On-Site Resident fisher/ |
Current Off-Site Non- |
Future Off-Site Non- |
Current On-Site Trespasser |
|
|
Groundwater |
|||||||
|
Drinking |
X3 |
X |
X3 |
X |
|||
|
Dermal contact1 |
X3 |
X |
X3 |
X |
|||
|
Inhalation2 |
X3 |
X |
X3 |
X |
|||
|
Soil |
|||||||
|
Ingestion |
X |
X |
X |
X |
b |
b |
X |
|
Dermal contact1 |
X |
X |
X |
X |
b |
b |
X |
|
Inhalation |
X |
X |
X |
X |
b |
b |
X |
|
External radiation1 |
X |
X |
X |
X |
b |
b |
X |
|
Sediment |
|||||||
|
Ingestion |
X |
X |
X |
X |
b |
b |
X |
|
Dermal contact1 |
X |
X |
X |
X |
b |
b |
X |
|
Inhalation |
X |
X |
X |
X |
b |
b |
X |
|
External radiation1 |
X |
X |
X |
X |
b |
b |
X |
|
Surface Water |
|||||||
|
Ingestion |
X |
X |
X |
X |
b |
b |
X |
|
Dermal contact1 |
X |
X |
X |
X |
b |
b |
X |
|
Fish |
|||||||
|
Consumption |
X |
X |
X |
X |
X |
X |
|
|
Deer |
|||||||
|
Consumption |
X |
X |
X |
X |
X = population considered
a = there are no on-site residents in OU V
b = considered insignificant compared to residential exposures
1 Dermal uptake is not applicable for radionuclides due to small permeability constants and additional shielding factors, whereas external radiation is only applicable for radionuclides.
2 Only inhalation of volatiles from groundwater is considered.
3 Exposure to groundwater is considered in the risk assessment although public water hookups have been provided in the affected area.
3.0 Constituents of Potential Concern
The purpose of the identification of the COPCs for use in the risk assessment is to focus the risk assessment process on the detected constituents that pose the greatest potential threat to human health. Section 3.1 defines the data sets that are used to represent the concentrations of constituents in the exposure media (e.g., surface soil, sediment). Section 3.2 describes the screening procedures used to select the COPCs. Section 3.3 presents the identified COPCs for each medium.
3.1 Data Sets
Chemical data from various environmental media were used in the previous baseline human health risk assessment: surface soil (0 to 6 inches), subsurface soil (0 to 12 feet), groundwater, surface sediment (0 to 6 inches), surface water, and fish. These data were fully validated by an independent contractor according to standard EPA procedures (1989a) to ensure that they were of suitable quality for use in the risk assessment. Since the baseline risk assessment, additional data have become available for some of these media. These data sets, as well as any additional data, are addressed in the following sections.
3.1.1 Surface Soil
Residents living along the Peconic River or trespassers to the BNL site near the Peconic River could be exposed to contaminants within the surface soils. These represent a relatively narrow band of soils adjacent to the Peconic River. Due to their limited area and their location next to the river, activities (e.g., construction) that would result in exposures to subsurface soils are unlikely. Because exposure to contaminants below the top six inches of soil is unlikely, data sets for concentrations in the top six inches were used for the human health risk assessment.
In general, soil samples had not been collected beyond the high water mark of the river up to the location or potential location of residential homes that would be representative of soil exposures to off-site or on-site riverside residents. However, several surface soil samples were collected in 2001 near the Peconic River in areas that may have received sediment removed from the river. These samples were collected near the STP discharge, near gauging station HM in Area A, and near gauging station HQ in Area D. Because these soil samples were collected from areas where it is suspected that sediment from the river may have been removed and placed on the nearby soil during construction activities related to the gauging stations, they were expected to be conservative estimates of average soil concentrations near the Peconic River. The data from these samples met all quality assurance/quality control (QA/QC) criteria, and these samples provide an additional surface soil data set: soils near the Peconic River. During the development of this risk assessment report, concerns were raised as to whether these were actually conservative estimates and whether soils nearer to residential homes may have higher cesium-137 concentrations from periodic flooding. In November 2002, several soil samples were collected along three transects extending from the high water mark of the river to the nearest residences. Cesium-137 was only detected in six of the fifteen samples, with the highest detected activity at 8 picoCuries per gram (pCi/g). These results were less than those reported for the soils near the gauging stations in Area A and Area D. No other data are available for soils, and not sediment, near the river. Thus, the on-site soil data set for this risk assessment consists of the soil data collected in Area A in 2001 and the off-site soil data set consists of the soil data collected in Area D in 2001.
3.1.2 Groundwater
Current and future off-site residents and potential future on-site residents could be exposed to contaminants in groundwater. Data representing groundwater in the area off-site and near the Peconic River and on-site near the Peconic River were used in this human health risk assessment.
The monitoring well groundwater data set used in the original risk assessment was used in this risk assessment. Groundwater samples from new and existing monitoring wells in the area have been collected as part of BNL’s annual monitoring program. The monitoring well data were evaluated to assure that they met the appropriate QA/QC criteria. The monitoring well data are considered most representative of potential drinking water exposures, and, with the addition of the more recent monitoring well data, provides a sufficiently large data set for use in the risk assessment.
The off-site groundwater data set used in the original risk assessment consisted of 65 off-site residential well samples collected and analyzed by the SCDHS. A formal risk assessment was not performed with this off-site groundwater data set; instead, the results of the individual well samples were compared to New York State or Federal drinking water standards.
For this risk assessment, the off-site groundwater data set consists of the results of samples collected from monitoring wells located near the eastern boundary of BNL in OU V and/or within the plume from OU V. This plume contains low-level volatile organic compounds (VOCs), primarily trichloroethene (TCE). The monitoring wells identified in the RI Report as AOC23-MW03 (061-04 and 061-05) are used for the off-site groundwater data set as well as monitoring wells, some more recently installed, sampled as part of the annual monitoring program (050-01, 050-02, 061-04, 061-05, 000-122, 000-123). (These wells are shown in Figure 2.) Additionally, SCDHS obtained data from a vertical profile monitoring well located off-site and within the OU V plume (identified as well MV-E within the data set). Data from this well are also included within the off-site groundwater data set. The data used for the off-site exposures were collected in 1995 as part of the RI, in 1999 as part of the Plutonium Contamination Characterization study, and up through 2001 as part of BNL’s annual monitoring program. Though the area defined by the groundwater data set has been provided public water hookups, the risk assessment assumes that off-site residents could use the groundwater as a drinking water and household-use source.
In evaluating risks due to use of groundwater as a household drinking water source, it is important to consider potential individual point sources (i.e., individual residential wells located at one point and at one general depth). Though the groundwater data used in this risk assessment are from wells that both characterize and delineate the potential contamination from OU V and the Peconic River, individual wells and well depths may have higher concentrations of some contaminants whereas other wells or depths may have higher concentrations of other contaminants. For example, the low-level VOC plume is located at a depth of approximately 200 feet below land surface (bls).
The data set contains data from monitoring wells located in the upper and lower portions of the deep aquifer. The range of these monitoring well screen intervals compare well with the range of screen intervals of domestic wells reported for the area. Data from monitoring wells located in the shallow aquifer were not used in the data set for this risk assessment since higher concentrations of contaminants were generally found below the shallow aquifer and the depths of these wells were less than the typical screen intervals of most domestic wells. The depths of the monitoring wells used for the OU V investigation are provided in the table below.
|
Upper Deep Aquifer |
Lower Deep Aquifer |
||
|
Well ID |
Screen Interval |
Well ID |
Screen Interval |
|
037-03 |
90-100 |
037-04 |
239-259 |
|
000-123 |
150-170 |
000-122 |
240-260 |
|
000-142 |
145-165 |
000-143 |
240-260 |
|
000-145 |
130-150 |
000-146 |
239-259 |
|
049-05 |
90-100 |
049-06 |
175-185 |
|
050-02 |
140-160 |
050-01 |
205-225 |
|
061-04 |
90-100 |
061-05 |
195-205 |
|
600-16 |
160-180 |
600-15 |
240-260 |
|
600-20 |
150-170 |
600-21 |
240-260 |
|
600-23 |
150-170 |
600-24 |
228-248 |
|
600-26 |
150-170 |
600-27 |
240-260 |
The potential uncertainty in the risk assessment concerning the use of the data from an extended area and various well depths is addressed in Section 6.7 of this report.
Results of the samples collected from on-site wells near the Peconic River in 1995 as part of the RI and in 1999 as part of the Plutonium Contamination Characterization study, as well as those collected up through 2001 as part of BNL’s annual monitoring program are used for the on-site groundwater data set in this risk assessment for exposures to potential future residents.
3.1.3 Surface Water
Current and future off-site residents, potential future on-site residents, and trespassers could be exposed to contaminants in surface water during activities in the Peconic River (e.g., swimming, wading). Thus, data representing concentrations of contaminants in the surface water either on-site or off-site were used in this human health risk assessment.
Nine surface water samples representing the surface water data set used in the previous risk assessment were located downstream of the STP discharge as far as the upper portion of Area C. On-site Area D contained no standing surface water during the period of surface water sample collections, and is often dry. Therefore on-site Area D is not represented in the on-site surface water data set. The on-site surface water data set used in this risk assessment consists of these nine surface water samples collected in 1995 as part of the RI.
Monthly data from 1972 to 1981 and from 1996 to 2001 indicate a yearly cycle that peaks around June and decreases through July and August and remains low (or no flow) throughout the early winter. Flow generally starts increasing in the January/February time frame. The 1996 to 2001 data indicate that flow generally stops around September or October and resumes in early winter. In dry years, it may stop in July or August. However, it is important to note that it is likely that portions of the upstream sections of the Peconic River (upstream) of Schultz Road will carry water during the early portion of the summer months, which is the peak fishing season.
Off-site Area D and Area E are also often dry, and did not contain water during most of the surface water sampling events. One sample was taken near Schultz Road during the RI Report Phase II sampling. However at that time, the Peconic River was dry from Area D on site until the confluence with the northern tributary to the Peconic River. Thus, the sample was not representative of surface water from the area. One sample was collected during the RI Report Additional Fish Tissue Study from on site near North Street, and one sample was collected from near Schultz Road. However, those were only analyzed for a limited number of contaminants, and only copper and lead were detected.
As part of BNL’s annual monitoring program, surface water samples have been collected periodically from gauging station HQ in Area D. Though the gauging station is on site, surface water passing through the gauging station is considered to be representative of surface water that could pass through the off-site Area D. In 2001, seven samples were collected between February and August. These data were used to represent the off-site surface water data set for this risk assessment.
3.1.4 Sediment
Current and future off-site residents, potential future on-site residents, and trespassers could be exposed to contaminants in sediment during activities in the Peconic River (e.g., swimming, wading). Thus, data representing concentrations of contaminants in the sediment water were appropriate for use in this human health risk assessment. Exposure to surface (top six inches) sediment is more likely than exposure to subsurface sediment. Therefore, surface sediment data was used.
The previous risk assessment used an on-site sediment data set consisting of the thirteen sediment samples collected from the top six inches of sediment collected from the on-site Peconic River extending from the STP to downstream of gauging station HQ near the BNL boundary. The risk assessment addressed potential on-site trespassers and future on-site residents that could be directly exposed to contaminated sediment in the on-site portion of the Peconic River (see Section 4.0 for further details). The applicable data (i.e., data that presents total concentrations in whole sediment and that have met appropriate QA/QC criteria) from the earlier studies were used in the reassessment. Additional sampling and analysis was conducted as part of the Supplementary Peconic River Sediment Sampling in September 2001 (BNL 2002), and was designed to fill gaps in the existing data necessary to better define the nature and extent of sediment contamination both on and off site. This consisted of 108 surface sediment samples collected on site and 49 surface sediment samples collected off site between the BNL boundary and an area just downstream of Schultz Road. These data were reviewed and validated to assure that they met the appropriate criteria, and the data from this sampling were used in the risk assessment for both on-site and off-site sediment data sets along with the data addressed in the previous paragraph.
Because the samples from the area just downstream of BNL (Area D) had higher levels of most contaminants in the sediment than areas further downstream (Areas E and P, for example), and because exposures to contaminants near where residents live are more likely to occur with more frequency, the data from Area D were used to represent the off-site sediment for evaluating potential exposures.. For example, the maximum concentration of cesium-137 in Area D was 17.4 pCi/g, whereas the maximum in Area E and Area P were 24.1 pCi/g and 22 pCi/g, respectively. Average concentrations for Area D or Area D extended to the maximum concentration in Area E were similar (7.9 pCi/g and 8.5 pCi/g, respectively). Average concentrations for other contaminants would decrease if the exposure area were increased (e.g., 12.4 milligrams per kilogram [mg/kg] to 10.5 mg/kg for mercury and 102 m g/kg to 92 m g/kg for Aroclor-1254, respectively).
Thus, the on-site sediment data set consists of the surface sediment data collected in 1995, 1996, and 1997 as part of the RI, in 1999 as part of the Plutonium Contamination Characterization study, and in 2001 as part of the Supplementary Peconic River Sediment Sampling. The off-site sediment data set consists of the surface sediment data collected from the off-site Area D in 1996 as part of the RI, in 1999 as part of the Plutonium Contamination Characterization study, and in 2001 as part of the Supplementary Peconic River Sediment Sampling.
The sediment data for both the on-site and off-site receptors included data from sediment that was usually covered with water, sediment that is often dry, and sediment that was only rarely wet. For certain exposure pathways (e.g., external gamma radiation), it was necessary to further divide the data into these subsets in order to assess total exposure.
3.1.5 Fish Tissue
People who consume fish from the Peconic River could be exposed to contaminants in the edible portions of those fish. Off-site residents or anglers can easily access the on-site portion of the Peconic River near North Street. Thus, it is appropriate to use the off-site edible fish tissue data from and including the on-site portion of North Street to Schultz Road for the risk assessment for current potential exposures, whereas it is appropriate to use the on-site edible fish tissue data from the STP down to and including North Street for the risk assessment for future potential exposures only.
A total of 97 fish tissue samples were collected in 1997 and analyzed as part of the Additional Fish Tissue Study. The report was presented as Appendix F.4 of the RI Report and was used in the original human health risk assessment. All fish collected during that study were analyzed as whole body samples (i.e., skin, scales, head, fins, viscera, bones, were all included in the sample), not as edible fish tissues. This was considered appropriate for assessing risks to wildlife that would consume whole fish, and it was considered conservative for assessing risks from organic contaminants to human health when only edible tissues are usually consumed. Lipophilic contaminants, such as PCBs, accumulate mainly in fatty tissues: belly flap, lateral line, subcutaneous and dorsal fat, dark muscle, gills, eyes, brain, and internal organs (EPA, 2000b). Many of these tissues are not typically consumed by humans. Contaminant concentration ratios between whole body samples and standard fillet samples have been reported to be greater than one (Parkerton et al., 1993; Nimmi and Oliver, 1989). Conversely, risks due to mercury may actually be underestimated when using whole body data (EPA 1997d). A total of 36 fish were collected from on-site areas and used to represent the on-site fish data set. A total of 37 fish were collected from off-site areas of the Peconic River and used to represent the off-site fish data set.
In 1996, fish were also collected from the on-site Peconic River and analyzed for chemical and radiological constituents. The results were reported in the Fish Tissue Bioaccumulation Study Report that was contained as Appendix F.3 of the RI Report. All fish were small (generally less than six inches in length) and were prepared by beheading and eviscerating. Composite samples were prepared representing the same species from the same location. These also were not prepared as edible fish tissue samples. Though most samples were analyzed for metals, only four samples were analyzed for organic contaminants. Fish have also been collected in the Peconic River on site as part of BNL’s annual monitoring program. These fish were treated as whole body samples due to the small size of the fish. The fish data from the 2000 Site Environmental Report (BNL 2001) and the 1999 Site Environmental Report (BNL 2000) provide data for a total of six fish samples from on site that were analyzed as whole body samples. The off-site fish data used in the baseline risk assessment reported in the RI Report were from fish collected from an area near Schultz Road, an area near Manor Road, Donahues Pond, and Forge Pond, and, therefore, represented a large off-site area. These fish were collected as whole body samples and not edible fish tissue. Thus, they were considered to be conservative estimates of actual exposure to organic contaminants and potentially under-estimates of actual exposure to mercury.
In June and July 2001, fish were collected from off-site areas downstream of gauging station HQ as far as the Schultz Road area by NYSDEC personnel. These fish were not tested as whole fish samples. Instead, larger fish were prepared as edible fillets, and smaller fish were beheaded and eviscerated, in accordance with EPA guidance (EPA 2000b). Edible fish data are preferred because they most accurately measure the potential exposure concentrations for people eating fish, and edible fillet concentrations and whole body concentrations are often drastically different. In fact, the edible fish tissue data from the North Street area and the Schultz Road area collection 2001 were compared to the data from the fish previously collected from the same areas that were tested as whole body samples. Concentrations of mercury, Aroclor-1254, dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethene (DDE), and dichlorodiphenyltrichloroethane (DDT) from the 1997 and 2001 collections were compared statistically and, as expected, were found to be statistically significantly different. The pesticides and PCBs, which partition to fatty tissues, were found to be significantly lower in the edible portions from 2001 than in the whole fish from 1997. In accordance with EPA guidance (2000b), edible fish tissue data should be used in the risk assessment. Thus, the recently collected fish tissue data from 2001 were used as the off-site fish data set in this human health risk assessment.
Though the fish collected on-site and upstream of the gauging station HQ were all analyzed as whole body samples, the data were used as estimates of on-site exposures because adequate edible portion sample data are not available for on site. These are likely to overestimate exposures to organic contaminants such as PCBs but may underestimate exposures to mercury. The data from the 1997 and 1996 collections, which constitute the bulk of the on-site data, as well as the data from the six samples collected as part of the annual monitoring program (BNL 2000, 2001), were used in the on-site fish tissue data set.
Since edible-portion sample data are not available for on-site fish except for the on-site Area D below the gauging station, whole-body sample data from the STP to on-site Area D above the gauging station were used. This provided a conservative estimate of on-site exposures for most organic contaminants in the edible portion of those fish, but may underestimate the mercury concentrations in the edible tissue of those fish. The data from the 1997 and 1996 collections and the data from the annual monitoring program were also used in the on-site fish tissue data set. Thus, the data set for fish used for potential future on-site exposure consists of whole-body data from on-site areas from Area D to the STP collected in 1996 and 1997 as part of the RI and from 1999 and 2000 as part of BNL’s annual monitoring program.
The data set for fish used for evaluating exposure by off-site residents and anglers consists of edible fish tissue data from the Peconic River Area D near North Street to Schultz Road collected in 2001 as part of BNL’s annual monitoring program. No edible fish tissue data were available for the on-site Area D above the gauging station, an area that is easily accessible to off-site receptors. Based on the concentrations of organic contaminants (particularly PCBs) measured in whole body samples from on-site Area D above the gauging station, it is expected that the edible fish tissue concentrations would be higher than those reported in the edible fish tissue data from below the gauging station. The lack of edible fish tissue data from the on-site Area D above the gauging station is addressed in Section 6.7 with regard to the potential uncertainty in the risk assessment.
For the most part, fish collected upstream of Schultz Road, particularly in the on-site upstream area, are generally small but have included a few sufficiently large fish to provide for fillets. Data from an ongoing investigation will be used to predict future fish size and biomass relative to water level in the Peconic River and similar streams.
3.1.6 Deer Tissue
Samples of deer tissue are routinely collected by BNL from on-site, off-site, and remote areas. These samples have been analyzed for select radionuclides, including cesium-137. Data from these samples are reported within BNL’s annual Site Environmental Reports (BNL 2001, 2000, 1999, 1998, 1997).
For the purposes of this risk assessment, a deer tissue data set for was used to evaluate exposures to hunters that obtain deer near BNL. Analysis of deer meat has been conducted for cesium-137. Analysis for other bioaccumulatable contaminants (e.g., mercury, cadmium, PCBs) has not been conducted. Thus, only exposures to cesium-137 can be quantitatively evaluated. The foraging range of deer is typically one square mile (Grund et al. 2002). It is reasonable and conservative to assume that any deer found within one mile of OU V or the off-site upstream section of the Peconic River may represent cesium-137 levels derived from OU V sources or the Peconic River. However, in non-optimal conditions, deer may range further for food and shelter. Deer with elevated cesium-137 levels have been found at further distances from BNL, and accumulation of cesium-137 in deer meat may occur from other areas of the BNL site besides the Peconic River. Since, the average cesium-137 levels in deer on the BNL site (2.4 pCi/g), on or within one mile of the BNL site (2.4 pCi/g), and on or within 10 miles of the BNL site (2.2 pCi/g) were similar, for the purpose of this risk assessment, the deer tissue data set contains data from deer collected from on the BNL site up to a distance of 10 miles.
Background deer tissue samples were considered to be those flesh or meat samples from deer collected 10 to 40 miles from BNL. Those deer are assumed to be representative of background cesium-137 levels. The data collected from background areas from 1996 to 2001 were used to define the background deer meat data set. The average concentration in these deer was 0.6 pCi/g.
The deer collected since 1992 and reported in the Site Environmental Reports were used to define the cesium-137 deer tissue data set for this risk assessment. Additionally, the Site Environmental Report contains data for non-edible tissues (e.g., bone) and other edible tissues (e.g., heart and liver), as well as standard meat, or flesh, samples. Since the hunter’s dietary intake is largely flesh samples and not organ meats, the data for the heart and liver (which generally showed lower cesium-137 levels than flesh samples) were not used in the data set to avoid biasing the data inappropriately toward the activities measured in the heart and liver.
The bioaccumulation of cesium-137 in deer is likely due more to other BNL sources than from the Peconic River. The remediation of soil as part of Operable Unit V is designed, in part, to address this bioaccumulation and reduce cesium-137 concentrations in deer. Regardless, the deer meat data set has been defined so as to address the total exposure with which receptors who are associated with the Peconic River area may come in contact.
3.1.7 Data QA/QC and Validation
Analytical data quality was assured through the use of standard field sampling and analytical laboratory procedures that were reviewed and approved by EPA and NYSDEC. All chemical and radiological data were validated to further assure the quality of the data. Data validation is a specific data evaluation process that examines adherence to EPA’s performance-based acceptance criteria. The analytical data validation process consisted of ensuring analytical data quality through the use of standard field sampling and analytical laboratory procedures, specifically evaluation of data completeness, verification of instrument calibration, measurement of laboratory precision using duplicate samples, measurement of laboratory accuracy using spikes, examination of blanks for contamination, assessment of adherence to method specifications and QC limits, and evaluation of method performance in the type of sample matrix.
3.2 Screening Procedures
It is important to focus on constituents that have the potential to cause the greatest risk. Screening procedures are used to limit the number of constituents of potential concern in each medium (EPA 1989a). Three screening procedures are used for the risk assessment data sets to assure that the proper contaminants are being assessed. The methodology for the screening procedures used in this risk assessment are addressed in the following paragraphs.The first level of screening is an evaluation of the frequency of detection in each of the data sets. Constituents that are infrequently detected may be artifacts in the data due to sampling, analytical, or other procedures and, therefore, may not be related to site operations or disposal practices. For this risk assessment, a constituent detected in five percent or fewer samples in any given environmental medium (e.g., groundwater, soil, fish) was omitted from the quantitative risk assessment for that medium. In addition, constituents that are considered essential nutrients, such as aluminum, calcium, sodium, magnesium, potassium and iron, were excluded.
The second level of screening that was applied to each of the data sets was a comparison method. For the comparison method, the maximum concentration detected in a medium or data set was compared to screening values. Region II of the EPA recommends the use of the Region IX Preliminary Remediation Goals (PRGs) as the appropriate screening values. These PRGs are based on generic residential exposure assumptions and either a hazard index of 1/10 or a cancer risk of 1 ´ 10-6 (a one in one million increased cancer risk). However, constituents that are known human carcinogens (Group A) were retained as COPCs if they exceeded screening values, regardless of the frequency of their detection. The Region IX PRGs were developed in 2000 and updated in 2002; the PRGs were reviewed prior to use in screening to assure that the most recent toxicity data were used in the development of the PRGs. PRGs were recalculated for those constituents for which toxicity data had changed since the development of the revised PRGs.
The third level of screening applies only to radionuclides. Region IX PRGs are not available for radionuclides. Instead, the maximum detected radionuclide activity in a particular medium was compared to the background activity for that radionuclide. If the maximum activity of that radionuclide was below that of the background, that radionuclide was not retained as a COPC for that particular medium. Since cancer risks are determined as the increased lifetime cancer risk above background, this screening procedure is appropriate. Background reference activities of selected radionuclides in soil were identified in the OU I RI Report. Additional data had been collected and reported in the Plutonium Contamination Characterization and Dose and Risk Assessment Report for other media and other radionuclides. Additionally, detected radionuclides with half-lives less than 6 months are also not considered in this risk assessment. The potential risk due to these radionuclides is incorporated in the slope factors for their parent radionuclides. Radium-226, which had been reported in some groundwater samples and was analyzed using gamma spectroscopy, was also eliminated as a COPC. Gamma spectroscopy is known to grossly overestimate, or misidentify, radium-226. Subsequent isotope specific analysis for radium-226, with lower detection limits, found no detectable levels of radium-226. For those radionuclides identified as COPCs, the activities used in the risk assessment are the measured exposure point concentrations minus the average background activities. In this way, the calculated risk is the incremental lifetime cancer risk above background.
Lead detected in environmental media at OU V has been addressed as follows. The EPA has not derived a carcinogenic slope factor or a non-carcinogenic reference dose for lead. The EPA recommends using the "Integrated Exposure Uptake Biokinetic Model for Lead in Children" for soil levels above 400 mg/kg and groundwater concentrations above the EPA action level of 15 micrograms per liter (µg/L). The highest soil concentration reported for OU V is 95.5 mg/kg, less than a quarter of the action level. Soils near the Peconic River were even less, with a maximum of 22.4 mg/kg. A further assessment of lead in soil was unnecessary. The Adult Lead Model (EPA, 1996a) indicates that the concentration in soil associated with adult exposures and impacts on the developing fetus range from 750 mg/kg to 1,750 mg/kg. Thus, the 400 mg/kg screening level is also protective of adults. The highest concentration in sediment reported in the OU V RI Report was 120 mg/kg. The highest concentration of lead in sediment was 214 mg/kg, which is below the action level. Based on this information, no further assessment of lead in sediment is necessary. The groundwater data set used from on site near the Peconic River used to evaluate potential off-site exposures had a maximum concentration of 3.2 µg/L and that for on-site future residential exposures had a maximum concentration of 1.4 µg/L. A further assessment of lead in groundwater was unnecessary.
3.3 Identification of COPCs
The results of the screening procedures for COPCs are presented in Table 2-1 through Table 2-11. Each table presents a summary of the occurrence, distribution, and selection of COPCs. The frequency of detection is listed as well as the minimum and maximum detected concentrations. The screening toxicity value is presented as well (e.g., the Region IX PRG) as additional information regarding other potential regulatory values. The last two columns indicate whether the constituent was considered to be a COPC for the risk assessment or not and the reason for its inclusion or exclusion.
Groundwater: For on-site groundwater, three inorganics, three VOCs, and four radionuclides were identified as COPCs: arsenic, manganese, thallium, 1,1-dichloroethene, chloroform, trichloroethene, plutonium-238, strontium-90, tritium, and uranium-233/234. For off-site groundwater, four inorganics, six VOCs, and four radionuclides were identified as COPCs: arsenic, cyanide, iron, manganese, 1,1-dichloroethene, 1,2-dichloroethane, ammonia, chloroform, tetrachloroethene, trichloroethene, plutonium-238, tritium, uranium-233/234, and uranium-238.
Surface soil: The only COPCs identified for on-site and off-site surface soil adjacent to the Peconic River were arsenic and cesium-137. Though arsenic in off-site soil was below the background concentration, it was still retained as a COPC.
Sediment: COPCs for on-site sediment were polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), inorganics, and radionuclides: Aroclor-1254, benzo(a)pyrene, benzo(b)fluoranthene, arsenic, mercury, americium-241, cesium-137, cobalt-60, lead-210, plutonium-238, plutonium-239/240, strontium-90, uranium-233/234, uranium-235, uranium-238, and tritium. Off-site sediment COPCs included arcolor-1254, arsenic, chromium, mercury, americium-241, cesium-137, plutonium-238, plutonium-239/240, and uranium-235.
Surface water: Arsenic, chloroform, cyanide, thallium, americium-241, tritium, uranium-233/234, and uranium-235 were identified as on-site surface water COPCs. Arsenic, uranium-233/234, and uranium-235 were also identified as off-site surface water COPCs.
Fish: COPCs in on-site fish are 4,4-DDD, 4,4-DDE, alpha-chlordane, Aroclor-1254, Aroclor-1260, arsenic, cadmium, copper, mercury, americium-241, cesium-137, strontium-90, uranium-234, uranium-235, and uranium-238. Mercury in fish is conservatively assumed to be all methyl mercury. Off-site fish COPCs are 4,4-DDD, 4,4-DDE, 4,4-DDT, Aroclor-1242, Aroclor-1254, mercury, cesium-137, and strontium-90. It should be noted that the analysis conducted on fish used for assessing the off-site receptors reported combined concentrations of Aroclor-1254 and Aroclor-1260. Since toxicity information is available for either total PCBs or Aroclor-1254, but not for Aroclor-1260, the reported concentrations were conservatively assumed to be all Aroclor-1254.
Deer: Deer meat samples have not been analyzed for non-radiological constituents. Deer meat was analyzed for cesium-137 due to the presence of cesium-137 in media throughout the site that may lead to uptake by plants on which deer might feed and due to the potential for cesium-137 to partition to the flesh instead of non-edible tissues. Other bioaccumulative contaminants such as PCBs or mercury are limited in their distribution (i.e., found in Peconic River sediment) and are unlikely to provide a significant source to deer. Therefore, only cesium-137 is identified as a COPC for deer meat.
4.0 Exposure Assessment
The Risk Protocols (found in Appendix A) define the assessment process. After samples were collected, the sample data were used as outlined in the protocols to determine exposures. The objective of the exposure assessment is to quantify the type and magnitude of the total exposure by potential receptors to COPCs that are present at, or migrating from, BNL, or are present off site but may be due to BNL activities, currently or at some time in the future if no further remedial actions were to be taken. The potentially exposed populations and exposure pathways to environmental media (e.g., soil, surface water, sediment, and groundwater) were identified in Section 2.0. Section 4.1 presents a list of some technical terms that are used within the exposure assessment. In Section 4.2, the statistical analyses that are used to determine a conservative exposure point concentration (EPC) are presented. Section 4.3 identifies the exposure pathways for each of the potential receptors being evaluated. In Section 4.4, the equations that are used to determine the Chronic Daily Intakes (CDI) of non-radiological COPCs and the total radiological intake and annual dose are presented, along with the exposure factor assumptions.
4.1 Definition of Terms
Some technical terms are used in this section of the document. Following is a brief explanation of what these terms mean, and how they are used.
Central Tendency Exposure (CTE): A risk descriptor representing the average or typical individual in a population, usually considered to be the mean or median of the distribution.
Chronic Daily Intakes (CDI): Exposure expressed as mass of a substance contacted per unit body weight per unit time, averaged over a long period of time (as a Superfund program guideline, seven years to a lifetime).
Exposure Point Concentration (EPC): The contaminant concentration within an exposure unit to which receptors are exposed. Estimates of the EPC represent the concentration term used in exposure assessment.
Hazard Index (HI): The sum of hazard quotients for substances that affect the same target organ or organ system. Because different pollutants may cause similar adverse health effects, it is often appropriate to combine hazard quotients associated with different substances.
Hazard Quotient (HQ): The ratio of a single substance exposure level over a specified time period (e.g., subchronic) to a reference dose (or concentration) for that substance derived from a similar exposure period.
Reasonable Maximum Exposure (RME): The highest exposure that is reasonably expected to occur at a site. The intent of the RME is to estimate a conservative exposure case (i.e., well above the average case) that is still within the range of possible exposures.
Reference Concentration (RfC): The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups which include children, asthmatics and the elderly) that is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be derived from various types of human or animal data, with uncertainty factors generally applied to reflect limitations of the data used.
Reference Dose (RfD): The RfD, like the RfC, is an estimate of the amount of exposure to which a person (including sensitive subpopulations) could be exposed to on a daily basis where adverse noncarcinogenic health effects (e.g., organ damage, biochemical alterations, birth defects) would not be expected.
Slope Factor (SF): A plausible upper-bound estimate of the probability of a response per unit intake of a chemical over a lifetime. The slope factor is used to estimate an upper-bound probability of an individual developing cancer as a result of a lifetime of exposure to a particular level of a potential carcinogen.
Upper Confidence Limit (UCL): The Upper Confidence Limit is the upper bound of a confidence interval around any calculated statistic, most typically an average. For example, the 95 percent confidence interval for an average is the range of values that will contain the true average (i.e., the average of the full statistical population of all possible data) 95 percent of the time.
4.2 Exposure Point Concentrations
Statistical analyses were performed to verify the distribution of contaminants in environmental media at the Peconic River and to determine a typical concentration for each constituent in each medium. The first step was to determine the appropriate statistical distribution (i.e., normal or log-normal) that the data represented. This was accomplished by using the W-test or D’Agostino’s Test depending on the size of the data set (Gilbert 1987). The W-test was developed by Shapiro and Wilk (1965) and is used for testing whether a data set is from a normal distribution. By conducting the test on the log-transformed data, it is equally effective for testing whether a data set is from a log-normal distribution. The W-test is used for data sets with fewer than 50 data points. D’Agostino’s test (D’Agostino 1971) is used for testing for normality or log-normality for data sets with greater than fifty elements.
For quantitative human health risk assessments, the EPC — which is the concentration term used in the exposure equations — is the arithmetic average of the concentration that is contacted over the exposure period. It is estimated from the arithmetic average concentration for a contaminant based on a set of sampling results. Because of the uncertainty associated with estimating the true average concentration at a site, the 95 percent upper confidence limit (UCL) of the arithmetic mean was used for this variable for the reasonable maximum exposure (RME). The 95 percent UCL provides reasonable confidence that the true site average concentration will not be underestimated. The arithmetic average concentration is used for the central tendency exposure (CTE). For normal and log-normal distributions, the UCL was calculated according to the following equations:
For normal distributions
where
UCL = upper confidence limit
x = mean of the un-transformed data
s = standard deviation of the un-transformed data
t = Student-t statistic
n = number of samples.
For log-normal distributions
where
UCL = upper confidence limit
x = mean of the transformed data
s = standard deviation of the transformed data
H = H-statistic
n = number of samples.
In accordance with EPA guidance (Singh et al. 1997), the non-parametric jackknife method was used to determine the 95 percent UCL for any data that were not identified as either normal or log-normal. The jackknife procedure requires no assumptions regarding the statistical distribution. The procedure is conceptually simple and is based on resampling techniques that tend to require considerable computing power. For a data set of size n, n estimates of the mean are computed by deleting one observation at a time from the data set. The jackknife estimate of the mean and the standard deviation can be calculated to reduce the bias in the data set, and appropriate confidence limits can be derived (see Singh et al. [1997] for mathematical details). For small data sets (those with fewer than 10 samples), the maximum detected concentration is used if the calculated 95 percent UCL exceeds the maximum detected concentration.
The 95 percent UCL was calculated for each of the data sets used as a conservative estimate of the true average concentration for that media that the data set represents. In the case that the calculated 95 percent UCL is greater than the maximum detected concentration, the maximum concentration was used instead of the calculated 95 percent UCL.
For the calculation of both average and 95 percent UCL concentrations, samples with non-detectable levels were considered to contain half of the detection limit of that constituent. In cases where samples with non-detectable levels had detection limits greater than the detected concentrations in all other samples, the data were not used in the calculation of 95 percent UCLs.
Table 3-1 through Table 3-11 present the EPCs for each of the COPCs identified in each medium. These tables include the statistical method used to determine the 95 percent UCL depending on the statistical distribution, if any, that fits the data, the 95 percent UCL and the arithmetic average concentration.
4.3 Quantification of Exposure
Identifying exposure pathways provides a method to estimate doses of
contaminants that populations may receive. Each exposure pathway was evaluated
for the four elements necessary to indicate potential exposure of a population.
Each identified pathway must meet these four criteria:
· a source and mechanism of release of contaminants
to the environment
· an environmental transport medium or mechanism of transfer of
contaminants among environmental media
· a point of potential contact of humans to the contaminated medium
· an identified route of exposure
An identified pathway indicates that the potential for exposure exists; it does not imply that exposures do or may actually occur. Exposure assessments for current land-use and future land-use scenarios are discussed in the following sections.
4.3.1 Current Conditions
Under current conditions, the potentially exposed populations include on-site trespassers and off-site residents. An on-site trespasser scenario was evaluated because residential properties are adjacent to the eastern boundary of OU V. An older child (aged 7 to 12) trespasser was selected as the sensitive, potentially exposed receptor for the on-site trespasser scenario. A younger child (aged 1 to 6) as a trespasser was not evaluated since the frequency of visits by a child of this age range is very unlikely. Additionally, adults trespassing onto the on-site portions near the Peconic River were considered less likely due to less free time for such activities. The older child could have adequate free time after school hours, on weekends and holidays, and during the summer months. The older child was selected for evaluation based on the greater likelihood and frequency of exposure. An off-site resident was assumed to reside near the off-site upstream section of the Peconic River. Both an adult, a younger child (aged 1 to 6), and an older child (aged 7 to 12) resident were evaluated. Additionally, a recreational hunter/angler may be exposed to contaminants in fish and game. A recreational hunter/angler who was not a riverside resident was evaluated as a potential receptor. In addition, a riverside resident may also be a recreational hunter/angler. This potential receptor was also evaluated. Estimates of the exposures are based on measurements of existing site conditions.
For an older child (aged 7 to 12) as the on-site trespasser, eight exposure pathways are evaluated in this current land use exposure assessment:
· Inhalation of soil particulates and dusts near
the Peconic River
· Incidental ingestion of soil near the Peconic
River
· Direct dermal contact with soil near the Peconic
River
· Incidental ingestion of sediment from the Peconic
River
· Direct dermal contact with sediment from the
Peconic River
· Inhalation of sediment particulates and dusts from
dry areas of the Peconic River
· Incidental ingestion of surface water from the
Peconic River
· Direct dermal contact with surface water in the
Peconic River
Table 4.1, Table 4.2, and Table 4.3 present the exposure pathway parameters that were used for the exposure algorithms to estimate intake of site-related contaminants through all identified pathways for an older child on-site trespasser for soil, sediment, and surface water, respectively. Some of those parameters (e.g., those not representing standard default exposure values) are discussed below.
Based on an older child (ages 7 to 12) playing and exploring the Peconic River area two days a week for up to eight months a year, the trespasser was assumed to be on-site 64 days a year, as a reasonable maximum exposure (RME). The central tendency exposure (CTE) was assumed to be 13 days/year based on playing and exploring the Peconic River area one day a week during the summer months (i.e., 13 weeks). An inhalation rate of 1.2 cubic meters per hour (m3/hr) was assumed as an average for the entire eight-hour exposure period (EPA, 1997a). This assumed moderate activity levels, on the average, for the entire exposure period.
Potential trespasser exposure to on-site groundwater was evaluated for consideration in this risk assessment. Neither ingestion nor dermal contact to groundwater is possible at OU V under current land-use scenarios. Therefore, trespasser exposure to on-site groundwater was not considered in this risk assessment.
Twelve environmental medium exposure pathways are evaluated in the resident exposure assessment:
· Incidental ingestion of soils from near the
Peconic River
· Direct dermal contact with soil from near the Peconic River
· Inhalation of soil particulates and dusts near the
Peconic River
· Incidental ingestion of sediment from the Peconic
River
· Direct dermal contact with sediment from the
Peconic River
· Inhalation of sediment particulates and dusts from
dry areas of the Peconic River
· Incidental ingestion of surface water in the
Peconic River through recreational activities
· Direct dermal contact with surface water in the
Peconic River
· Ingestion of fish caught from the off-site
upstream section of the Peconic River
· Ingestion of groundwater as the drinking water
source
· Direct dermal contact with groundwater through
bathing
· Inhalation of volatiles in groundwater during
showering exposure
· External radiation from gamma emitting
radionuclides in soil and sediment
Public water hookups have been provided to off-site residents near North Street in the area of groundwater contamination from OU V. However, the risk assessment conservatively assumes that the groundwater may be used as a household and drinking water source in that area.
Table 4.4 through Table 4.18 present the exposure pathway parameters that were used for the exposure algorithms to estimate intake of site-related contaminants through all identified pathways for off-site residents living near the Peconic River. Residents that are recreational anglers and/or recreational hunters that fish and hunt in this area of the Peconic River may also be exposed to contaminants in fish or game at different exposure levels than non-angler residents. The exposure parameters for recreational anglers/hunters are presented in Table 4.19 through Table 4.21 for fish exposure and in Table 4.37 through Table 4.39 for deer exposure. For residents who are recreational anglers/hunters in this area of the Peconic River, both the residential exposure pathways for other media (i.e., soil, surface water, sediment, groundwater) and the recreational angler exposure pathways (i.e., fish) were used together.
Exposure to surface water and sediment from the on-site Peconic River was included in the exposure assessment for the older child trespasser, and exposure to surface water and sediment from the off-site upstream section of the Peconic River was included in the exposure assessment for the off-site resident.
Ingesting chemical contaminants by eating fish caught in the upstream on-site Peconic River was not considered in the current land-use scenario, because on-site fish upstream of North Street are generally too small to be of edible size, and on-site access, excluding the accessible North Street area, is limited for people to actually fish. Ingesting chemical contaminants by eating fish caught off site or on site near North Street was considered in the current land-use scenario for the off-site resident.
As described previously, fish from the on-site Area D near North Street to Schultz Road were considered in the off-site resident exposure. The recreational angler adult and older child (both riverside resident and non-riverside resident) was assumed to have a RME of locally caught fish of 25 grams per day (g/day) (20 pounds per year [lb/year]) and a CTE of eight g/day (6.4 lb/year) (EPA 1997a). The recreational angler younger child was assumed to have a RME of locally caught fish of 12.5 g/day and a CTE of 4.0 g/day. This is based on the assumption that the young child would eat the same number of meals as the adult or older child but would eat smaller portions (4-ounce meals instead of 8-ounce meals). The adult, older child, or younger child riverside resident that is not a recreational angler was assumed to have an RME of 6.5 g/day (5.2 lb/year) (assuming occasional fishing in the area). The 6.5 g/day rate assumed catching and consuming locally caught fish as ten meals of a half pound each or, based on the small size of most fish previously caught in this upstream section of the Peconic River, twenty meals of a quarter pound each. The younger child is assumed to have the same consumption rate as the adult or older child because of the potential smaller size of the meals already assumed as possible for the adult and older child. Because the majority of the general population does not consume locally caught fish (EPA 1997a), it was assumed that CTE factors would not include exposure to locally caught fish. Fish exposure frequency was 365 days per year and the exposure duration for adults was 30 years for RME and nine years for CTE and for children was 6 years for both RME and CTE.
Data on concentrations of contaminants in deer meat from the Peconic River area are limited to radiological analysis. Therefore, the rates of consumption of deer for the recreational angler/hunter were only applicable to the radiological risk assessment. The recreational hunter (both riverside resident and non-riverside resident) was assumed to have an RME of 28.9 kilograms per year (kg/year) (64 lb/year) and a CTE of 2.7 kg/year (6 lb/year) (EPA 1997a). The riverside resident that is not a recreational hunter, or is not within a family with a recreational hunter, was assumed to eat no locally caught deer. Deer exposure frequency was assumed to be 365 days per year and the exposure duration was 30 years for RME and 9 years for CTE.
4.3.2 Future Conditions
A residential scenario was addressed for future land-use of the on-site Peconic River area in the event that the area is ever developed as residential property. A residential adult, a young child (aged 1 to 6) as the most sensitive receptor, and an older child (aged 7 to 12) were used as the potentially exposed populations.
Typical residential exposures to environmental media were evaluated for both adults and a small child, aged 1 to 6, in the hypothetical future land use scenario. This conservative exposure scenario assumed that residents would live on site near the Peconic River for up to 30 years, and that residents would use on-site groundwater for all domestic water needs. This residential exposure assessment also included exposure to surface water and sediment through play and recreational activities. For this exposure assessment of a hypothetical on-site resident, a total of thirteen exposure pathways were evaluated for the adult and child residents.
· Incidental ingestion of soils from near the
Peconic River
· Direct dermal contact with soil from near the
Peconic River
· Inhalation of soil particulates and dusts near the
Peconic River
· Incidental ingestion of sediment from the Peconic
River
· Direct dermal contact with sediment from the
Peconic River
· Inhalation of sediment particulates and dusts from
dry areas of the Peconic River
· Incidental ingestion of surface water in the
Peconic River through recreational activities
· Direct dermal contact with surface water in the
Peconic River
· Ingestion of fish caught from the off-site
upstream section of the Peconic River
· Ingestion of groundwater as the drinking water
source
· Direct dermal contact with groundwater through
bathing
· Inhalation of volatiles in groundwater during
showering exposure
· External radiation from gamma emitting
radionuclides in soil and sediment
The exposure pathway parameters used in exposure algorithms to estimate intake of site-related contaminants through all identified pathways for adult and young child residents are listed in Table 4.22 through Table 4.36. Future on-site residents that are recreational anglers and/or recreational hunters that fish and hunt in this area of the Peconic River may also be exposed to contaminants in fish or game at different exposure levels than non-angler residents. For residents who are recreational anglers/hunters in this area of the Peconic River, both the residential exposure pathways for other media (i.e., soil, surface water, sediment, groundwater) and the recreational angler exposure pathways (i.e., fish) were used together. Residents were assumed to be exposed to soil and groundwater-related contaminants by their respective pathways up to 350 days per year. Exposure to sediment and surface water through play and recreational activities was assumed to occur 150 days a year as a reasonable maximum exposure for the young child and older child living adjacent to the upstream section of the Peconic River. This was based on the assumption that the available days for such activities is generally during the non-winter months (length of day light and warmer weather) and that half of these available days are spent outdoors playing in the sediment of the Peconic River. The days of non-exposure could be due to weather conditions, playing outdoors but elsewhere, not having available free time during day light hours, spending free time indoors (e.g., watching television, playing with computer or video games). The 150 days of exposure additionally assumed that half of the winter weekend days were spent playing in the sediment of the Peconic River. The following equation provides the calculation of the exposure frequency.
Exposure to surface water and sediment from the Peconic River was included in the future on-site residential exposure scenario. The on-site groundwater data set was used to estimate potential exposure to future on-site residents by three pathways: ingestion of water for drinking and cooking, dermal absorption of contaminants in groundwater through bathing, and inhalation of volatile organic contaminants during showering.
4.4 Exposure Equations and Parameters
Environmental medium-specific exposure algorithms were developed for each of the identified exposure route/pathways. Exposure algorithms are used to estimate chronic daily intake of non-radiological COPCs by receptors (e.g., industrial workers, adult and young child residents) in potentially exposed populations. The exposure to radiological COPCs is assessed using basically the same algorithms and assumptions. The differences between estimating non-radiological and radiological exposure are described in Section 4.4.12.
For each exposure activity, the chronic daily intake (CDI), expressed as mg/kg-day, was an averaged daily dose of a COPC ingested or absorbed by a receptor. The averaged dose received by a receptor was the critical point estimate for determining the extent of health risk/hazard associated with exposure to each constituent. Determining the exposure assessment was difficult to establish and accounts for much of the inherent uncertainty associated with exposure assessment.
In general, three parameters most influence the CDI:
· COPC concentration in the exposure medium
· COPC dose received during each exposure activity
event
· Lifetime frequency of exposure activity events
Point estimates of COPC concentrations do not vary in assessing the CDI by different exposure routes to the same medium. However, exposure parameters that influence receptor intake or absorption of COPCs, such as exposure duration and frequency, can and do vary in the exposure algorithms used to estimate the CDI by different exposure routes to the same medium. For each identified pathway, a RME scenario was developed. The exposure parameters used in the RME assessments are both average and upper-bound (90th to 95th percentile distribution) point estimates for each parameter and together should represent maximum exposures that can reasonably be expected.
4.4.1 Inhalation of Airborne Dusts and Particulates
Potential health hazards posed by airborne particulate material emanating from the Peconic River site was estimated by using a respirable particle concentration based on the upper bound 95th percentile concentration for airborne particulates in Suffolk County. Based on a study of 20 locations in Suffolk County, the average outdoor respirable particulate load was 21.8±4.5 micrograms per cubic meter (m g/m3) with an upper bound 95th percentile concentration of 30.8 m g/m3 (EPA 1995). This concentration of airborne particulate material is a conservative estimate for site-related airborne dusts and particulates. Studies have indicated that only a fraction of the measured particulates in air are derived from on-site soil (NJDEP 1995). In fact, EPA’s soil screening guidance (EPA, 1996b) recommends using a particulate emission factor of 1.32´ 109 m3/kg which is equivalent to a concentration of airborne particulate material of only 0.76 m g/m3.
A primary assumption of the model was that all airborne dusts and particulates emanating from surface soil have aerodynamic average diameters less than 30 microns and are considered respirable particulates. The particulate concentration of 30.8 m g/m3 was used to estimate the constituent-specific concentrations of site-related contaminants, by multiplying this particulate concentration by the fraction of the constituent concentration in soil or dry Peconic River sediment.
For example, the 95th percentile upper confidence limit of the average concentration of arsenic in off-site sediment of the Peconic River is 5.39 mg/kg. Therefore, the concentration of arsenic in airborne particulate material when the river is dry and the sediment exposed was estimated as 30.8 m g/m3 ´ 0.00000539 = 0.000166 m g/m3.
Because volatile organic compounds were not determined to be COPCs in soils and sediment at the Peconic River, inhalation of volatile organics from soil or sediment was not considered in the inhalation pathways.
Sediment is less likely to contribute airborne dusts/particulates since it is submerged below the water surface. However, there are parts of the Peconic River that are intermittent (i.e., sometimes wet and sometimes dry), and fugitive dusts may be generated during the dry periods. Sediment in Area D and the off-site upstream section down to the northern tributary to the Peconic River is considered to be intermittent and to contribute to airborne dusts and particulates for half of the year.
Inhalation rates vary with activity level and with age. Inhalation rates are lowest when at rest or sedentary and increase with the level of exercise. EPA (1991) recommended the use of an inhalation rate of 20 cubic meters per day (m3/day) for RME evaluations for adults in residential settings. For resident children, the long-term average inhalation rate of 8.7 m3/day (EPA 1989a) was assumed. Trespasser inhalation rates were based on assumed activity patterns. Because an eight-hour exposure period was considered for each exposure event, it was assumed that the exposure would consist of a m