Manufacturers of 29 chemicals produced in volumes of at least 1 million lb per year would have to conduct toxicity testing of these products and turn the results over to EPA, under a Feb. 25 proposal from the agency. Among the affected high-production-volume (HPV) substances are diethyl ketone, 1-tetracosanol, 1-hexacosanol, and coal-tar oils. EPA says significant numbers of people are exposed to many of these substances, and many are released into the environment in substantial quantities. Makers of these 29 substances have not agreed to test them under the HPV Challenge Program, which was established in 1998 by EPA, the chemical industry trade group American Chemistry Council, and the activist group Environmental Defense Fund. Through that program, companies have voluntarily provided basic toxicity data for some 1,400 HPV chemicals. But makers of hundreds of other HPV substances have not followed suit, so EPA is promulgating rules under the Toxic Substances Control Act that require companies to produce the data. The 29 substances are the third batch of HPV chemicals for which EPA has required testing.