The chemical revolution over the last 50 years has brought great benefits; it has also exposed us to unknown risks from thousands of untested chemicals that now circulate around us and inside of us. In a pioneering private study led by Mount Sinai School of Medicine in New York, researchers ran tests on nine adult volunteers from five states who did not work with chemicals on the job or live near an industrial facility. Before running out of money for testing, they found 167 industrial compounds, pesticides, pollutants, and other chemicals: 76 causing cancer in humans or animals, 94 toxic to the brain and nervous system, and 79 causing birth defects or abnormal development. The dangers of exposure to these chemicals in combination has never been studied. Except for chemicals used in drugs, food, and feed for animals, most chemicals are never tested for safety. By 2000, EPA logged 78,000 chemicals in commerce, only one-fifth with recorded tests for health risks. Faced with this great number of chemicals circulating in and around us, Congress demanded that the Environmental Protection Agency (EPA) tackle the greatest risks first, by determining which contaminants in tap water are the most widespread, harmful, and cost-effective to regulate. The Safe Drinking Water Act (SWDA) of 1996 requires EPA to publish a list of the most prevalent and worrisome unregulated contaminants. From the nation’s thousands of unregulated chemicals and microbes, in 1998 EPA chose about 60 for monitoring and potential regulation, known as its “Contaminant Candidate List” (CCL). To check the contaminants in your local water supply, see EPA’s National Contaminant Occurrence Database (NCOD). On July 18, EPA announced it was dropping nine contaminants from its candidate list as not posing serious enough health risks to control or remove them from tap water: “no regulatory action is appropriate.” The nine contaminants dropped by EPA include three inorganic compounds (manganese, sodium, sulfate); three synthetic organic compounds (aldrin, dieldrin, metribuzin); two volatile organic compounds (hexachlorobutadiene, naphthalene); and one microbial contaminant, acanthamoeba. Instead of regulating these contaminants, “EPA intends to release a guidance document for Acanthamoeba that will be directed mainly to contact lens wearers and will address the risks of Acanthamoeba eye infection associated with improper care of contact lenses.” EPA will also issue a “sodium advisory” that “provides appropriate cautions for individuals on low-sodium or sodium-restricted diets.” EPA is still studying the other 51 contaminants, including the toxic chemical perchlorate, the main ingredient in rocket and missile fuel. Perchlorate “contaminates drinking water supplies, groundwater or soil in hundreds of locations in at least 43 states,” according to the Environmental Working Group (EWG). The chemical can cause thyroid disease as well as a wide range of neurological problems for infants and children. “I don’t think too many scientists within EPA would dispute that perchlorate is bad and that we know enough to begin placing some regulations on it,” Bill Walker of the EWG told Environment and Energy Daily. Also on July 18, EPA announced it had completed reviewing half the 69 tap water contaminants regulated prior to 1997, as required every six years by the Safe Drinking Water Act of 1996. Thirty-four contaminants were still under review. Of the 35 completed, EPA decided 16 contaminants were still appropriately regulated, and 18 were ruled too “low priority” to change or EPA lacked enough information to decide. EPA will revise the rules for “total coliform” bacteria.