[en] The oxygenated fuels business is again under attack. A trio of scientific teams charges that atmospheric monitoring suggests reformulated gasoline is not significantly cutting carbon monoxide (CO) levels and could be raising ambient concentrations of such compounds as formaldehyde and nitrogen oxides. The results, presented at last week's meeting of the American Chemical Society (ACS) in Denver, come less than a month after heightened public concerns about the health effects of methyl tert-butyl ether (MTBE). The scientists reporting at the ACS meeting separately measured air pollution in Denver; Albuquerque, NM; and Brazil-areas that have used oxygenated fuels for several years. The preliminary results, they say, show oxygenates use has little impact on carbon monoxide. And the researchers say they have found relatively high levels of acetaldehyde, formaldehyde, and related compounds, including the mutagen peroxyacetyl nitrate (PAN), in the atmosphere. According to Daniel Grosjean, of environmental research firm DGA (Ventura, Ca), measured levels of acetaldehyde in three Brazilian cities - which began using ethanol fuels in the late 1970s - appear to be among the highest in the world. The findings could cast serious doubts on the ambitious U.S. oxygenates program, which is increasingly requiring cities to use reformulated fuels. In 1988, Denver became the first U.S. city which mandated oxygenated fuels requirements. The region now uses oxygenates-mainly MTBE-for four months each year. But, says Larry G. Anderson, a chemist at the University of Colorado (Denver), we have seen no statistical effect on CO in the air. He points to a predicted 15%-20% drop in ambient CO by 1993. There is considerable evidence formaldehyde increased, Anderson says