The Toxic Substances Control Act (TSCA), enacted by Congress in 1976, gives the U.S. Environmental Protection Agency (EPA) the responsibility for checking the relative safety of all chemical substances not already covered under other federal laws. The EPA can control or ban a chemical if it poses an unreasonable risk to human or environmental health. Manufacturers must give the EPA information about new chemicals before they are commercially produced or marketed. The EPA then reviews the information and can order further testing to determine, for instance, whether the substance is persistent, carcinogenic, or otherwise acutely toxic. The acute toxicity or short term poisoning effects of chemicals can be evaluated by the LD50 test that determines the lethal dose required to kill fifty percent of test animals, usually rats or mice. Microbial biotechnology products for use in industry have been subject...