green groups in the us are livid at the removal of tertiary butyl acetate (tbac) from the list of ground level ozone-forming volatile organic compounds (vocs ) by the us Environmental Protection Agency (epa). They say the epa's move on November 18, 2004, would weaken the country's Clean Air Act. vocs react in sunlight to form the harmful ground-level ozone.

The epa has also removed four other chemicals from the list of vocs: hfe-7000, hf3 -7500, hfc 227ea, and methyl formate. All these can no more be regulated under the Clean Air Act. Rob Brenner, deputy assistant epa administrator for air and radiation, said tbac could become a substitute for other vocs used as solvents in paints and other coatings because it is much less reactive. hfe -7000, hf3-7500, hfc 227ea, and methyl formate do not have a significant role in the formation of ground-level ozone and could substitute the more harmful chlorofluorocarbons and hydrochlorofluorocarbons, the epa said. But Brenner admits that tests on rats and mice had indicated that tbac could have long-term health effects. Thus, its production would be permitted only in limited quantities till further tests are conducted and manufacturers would be required to record and report its use.

The green groups, however, are not willing to let the epa dismiss the matter of health effects so easily. The Natural Resources Defense Council (nrdc) has charged the agency with violating "basic rules of chemistry' in the method used to determine tbac's reactivity. John Walke, director of nrdc's clean air programmes, said the epa "has it backward' by delisting tbac first and continuing with toxicity testing later. nrdc might undertake legal action to block the delisting after it is published, he added.