Each year the U.S. EPA reviews an average of 1,700 new compounds that industries are seeking to introduce. The 1976 Toxic Substances Control Act requires that they be tested for any ill effects before approval only if evidence of potential harm exists -which is seldom the case for new chemicals. The agency approves about 90 percent of the new compounds without restrictions. Only a quarter of the 82,000 chemicals in use in the U.S. have ever been tested for toxicity.