About 700 new chemicals are introduced each year, on top of 80,000 already in use. Since 1976, the EPA has restricted the use of five existing chemicals, according to Zimmerman. “If you live and breathe in the United States,” she says, “you are exposed to chemicals with little or no knowledge of their impacts on health or the environment.” Zimmerman is working toward a world in which the properties of chemicals that make them toxic are understood, so she and others can design alternatives that are equally effective, but more benign. She’s working through a database of 12 million chemicals, modeling their properties, and trying to correlate them with different toxicities to fish, birds, and mammals. She’s already identified molecular characteristics that affect fish or aquatic environments and is telling companies who develop such chemicals which chemicals are worth a second look in terms of potential toxicity.