A major target of environmental restoration and waste reduction efforts at Brookhaven National Laboratory (BNL) is the group of chemicals known as volatile organic compounds (VOCs). Historical and widespread use of these chemicals in government, industry and the home has left a challenging legacy of groundwater contamination at BNL and many other locations.
VOCs are chemicals that evaporate (or volatilize) when they are exposed to air. They are called organic because they contain carbon. These chemicals are used in the manufacture of, or are present in, many products used daily in both homes and businesses. Some products, like gasoline, actually are VOCs.
VOCs are used as fuels (gasoline and heating oil) and are components of many common household items like polishes, cosmetics, perfumes and cleansers. They are also used in industry and government as degreasers and solvents, and in dry cleaning. VOCs are present in many fabrics and furnishings, construction materials, adhesives and paints. In offices, VOCs can be found in correction fluid, magic markers, paper, rubber bands, invisible tape and other products.
The names of many VOCs may be familiar: carbon tetrachloride, trichloroethene (TCE), tetrachloroethene (PCE), trichloroethane (TCA), benzene and toluene. Because of their widespread historical use, and past lack of stringent disposal requirements, they are in our air, soil, and water in varying concentrations.
Regulatory requirements
Federal regulation of industrial and government VOC use and disposal began with the formation of the U.S. Environmental Protection Agency in the early 1970s. Until that time, people had limited specific knowledge about these chemicals and their potentially toxic effects. Chemicals were poured into sinks and toilets, directly onto the ground or into cesspools and sewers.
After testing found that VOCs could sometimes linger in the environment for years, federal and state agencies began to pass laws that set limits for disposal. These limits are based on extensive studies that provide information about each chemical and its effects on humans, animals, and the environment.
However, by the time these studies were completed and regulatory limits were set, large amounts of these VOCs had already been released to the environment.
VOCs and groundwater
Over the years, products containing VOCs have been spilled on the ground or disposed of in ways that have caused them to enter the groundwater directly (i.e., through cesspools, septic systems, drywells and landfills). VOCs spilled or dumped on the ground (e.g., when a lawnmower's gas tank is overfilled) evaporate to some extent, but they also are absorbed by the soil.
Rain or snow can then carry the VOCs deeper into the ground, where they eventually reach the groundwater. The VOCs do not volatize in the groundwater because of the lack of air movement. As a result, they will remain in the groundwater until removed by the natural processes of decay, dilution and biodegradation. Once they are in the groundwater, the VOCs migrate with the groundwater and can potentially enter drinking water wells.
VOCs and BNL
VOCs have been used as solvents and degreasers at the BNL site since it was the U.S. Army's Camp Upton. Past disposal practices at the Laboratory site have led to the formation of several "plumes," or areas of groundwater contamination, some of which extend beyond the Lab's boundaries (see illustration, right). BNL is actively treating these plumes to prevent further off-site movement of these chemicals and to clean the sole-source aquifer.
While BNL is cleaning up the legacy of past VOC use, it is also looking to prevent future contamination of the environment. The Lab is working to reduce the amount of VOCs and other hazardous materials used at the site through its expanding pollution prevention and waste reduction programs (see illustration, below). Over the past three years, such efforts have cut the amount of hazardous waste produced at the Laboratory in half.
As part of these programs, potential sources of contaminants at the Lab are being identified and removed or replaced. Solvents and degreasers that are safer for the environment are being selected and used in ways that minimize their potential for environmental release, and volume reduction and decontamination techniques are being employed to reduce the quantity of waste requiring disposal by BNL.
Remediating groundwater
Several technologies are available to reduce the concentrations of VOCs in groundwater. One of the most effective of these technologies is air stripping. It involves mixing air with the contaminated groundwater, which "strips," or removes, the VOCs from the water. The clean water is then returned to the ground. The air carrying the VOCs (now in gaseous form) is released into the atmosphere, at levels below regulatory limits, or treated further. Another common technology involves using carbon filters to remove VOCs from the groundwater.
These technologies are successfully used at many sites throughout the world to clean up VOC-contaminated groundwater. They are also used as a common form of treatment for public water supply wells. BNL is currently using three similar systems to treat on-site groundwater. Construction of a fourth system in an off-site area just south of the Lab will begin this summer (see the January 1998 issue for more information).
VOCs and health
Researchers have extensively studied the effects of most common VOCs on animals and humans. Federal and state regulatory agencies use the results of these studies, such as those performed by the Agency for Toxic Substances and Disease Registry (ATSDR), to determine health advisory levels and set limits on the amount of each VOC that is considered safe for human exposure.
Health advisory levels are based on a "no-effect level." The no-effect level is the maximum VOC dose that does not produce a known toxic effect in experiments and is further reduced by an additional safety factor.
The limits for each chemical are set by the U.S. Environmental Protection Agency (EPA), as well as the individual states. These agencies have established a maximum contaminant level (MCL) for each VOC. If water contains less than the MCL of the chemical, the water is considered safe for drinking. Local government agencies may also set their own drinking water standards; these are usually more stringent than the EPA's standards.
While the health effects of low-level exposure to VOCs are not known, studies have shown that exposure to, or ingestion of, VOCs in high concentrations can cause various health effects, including cancer.
Preventing exposure to VOCs is the best way to avoid the possibility of adverse health effects. Since 1996, the DOE has connected more than 1,500 BNL-area homes and businesses to the public water supply as a precautionary measure. The Suffolk County Water Authority samples and analyzes its water on a regular basis to ensure that it meets all guidelines established for potable supply wells.
Awareness is key
Government facilities like BNL, business owners and residents can help to prevent future VOC contamination of the groundwater by ensuring that dirty or spent solvents or paint thinners are properly disposed. Pouring them on the ground or down the drain contributes to groundwater contamination. Underground fuel and oil tanks should be checked for leakage.
BNL, meanwhile, will continue to clean up remaining groundwater contamination
while further reducing the use of these chemicals in day-to-day operations.
New initiatives, like the Lab's recent decision to participate in the Town
of Brookhaven's recycling program, will also help to minimize the Lab's
impact on the environment.