In 1994, researchers discovered unusually high rates of lupus and multiple myeloma (a bone marrow cancer) among Arizona residents in Tucson and Nogales. These researchers theorized that the high rates could be attributed to exposure to toxic chemicals. In Tucson, fifty thousand people had consumed water contaminated with trichloroethylene, a degreasing solvent. On the U.S.-Mexico border in Nogales, pollution from approximately one hundred Mexican maquiladoras (factories) and smoldering waste dumps had long filled the area’s air and bodies of water with toxic waste. According to Los Angeles Times environmental writer Marla Cone, Nogales “is plagued with so many sources of pollution that no one has a clue which chemical— or more likely which combination—might be playing a role in the lupus and myeloma.”

Americans are currently exposed to more than seventy thousand chemicals and their toxic waste by-products, including benzene...