Volatile organic chemicals, or VOCs, are a group of chemicals that contain carbon and readily evaporate. VOCs are found in a variety of products, such as solvents, degreasers and cleaning solutions. Benzene, toluene and vinyl chloride are examples of VOCs. High levels of VOCs in drinking water may be harmful to human health.
All VOCs can be irritating if they come in contact with the skin or to the mucous membranes if they are inhaled. At high levels, many VOCs may also increase the risk of cancer or cause central nervous system depression. Specific VOCs have certain health effects. For example, benzene may cause anemia, and trichloroethylene can cause liver problems. Because of these health concerns, the Environmental Protection Agency (EPA) has set Maximum Contaminant Levels (MCLs) for over twenty VOCs. In addition, the Acton Water District has set its own set of standards for VOCs, which are more stringent than the EPA’s. The Acton Water District has set a drinking water standard of 1 microgram per liter (ug/L) for any single VOC or 5 ug/L for any mixture of VOCs.
There are many different sources of VOCs. VOCs generally enter drinking water sources from pollution from factories and processing plants, where they are used as industrial solvents and degreasers. Chemical spills and improper disposal of industrial waste can release VOCs into the ground, and from there, they can leach into the water supply.
Most of Acton’s wells are treated for VOCs. VOC treatment entails pumping the water up a large tower filled with specially designed packing material. The water then trickles down from the top of the tower as air is pumped in from the bottom. This breaks the water up into tiny droplets from which the VOCs can more easily evaporate. In addition, the water is regularly tested to ensure that the concentrations of VOCs meet the state’s and the town’s strict standards. The proactive installation of treatment for VOC removal, along with controls on land use activities within each well’s zone of contribution (Zone II), serve as multiple barriers to avoid VOC contamination of the District’s water.