New hazard in leaded gas?
Though ethylene dibromide (EDB) is best known today as the chemical fumigant banned from use as a pesticide in most U.S. agricultural and food operations (SN: 11/10/84, P.296), it is also an additive in leaded gasoline. Used alone or together with dichloroethane (DCE), it helps prevent deposition of lead compounds of engine parts. "The common understanding was that [EDB and DCE] are completely decomposed during combusion," say Markus D. Muller and Hans-Rudolf Buser of the Swiss Federal Research Station in Wadenswill. But a study they report in the November ENVIRONMENTAL SCIENCE AND TECHNOLOGY suggests otherwise.
Their mass spectra analysis of the exhaust of idling cars fueled with leaded gasoline revealed trace quantities of 44 unexpected halogenated compounds, most of them containing bromine. (Halogens are a group of elements on the periodic table that include bromine and chlorine.) In fact, the chemists note, the EDB-based brominated compounds prevailed even in the exhaust of gasoline that had initially contained equal quantities of both additives. None of these halogens was identified in the exhaust of vehicles fueled with unleaded gasoline.
Although the researchers note that the toxicity of most of the compounds, such as 2,4,6-tribomophenol, is not known, they do point out that several of the brominated ones are structurally similar to toxic chlorine-based herbicides.
Environmental contamination with these gasoline additives may be somewhat less of a concern for U.S. motorists since a dramatic phasedown in the use of lead in gasoline was completed earlier this year (SN: 3/23/85, p. 187).
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|Title Annotation:||halogenated compounds found in exhaust|
|Date:||Dec 6, 1986|
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