EXPOSURE TO MTBE AND ACUTE HUMAN HEALTH-EFFECTS - A CRITICAL LITERATURE-REVIEW

Whether use of oxygen-rich gasoline additives to reduce air pollution is a cause of acute adverse health effects is an ongoing concern in th e United States. Attention has focused in particular on use of methyl tert-butyl ether (MTBE, CAS #1634-04-4) and, despite considerable publ ished research, debate persists regarding its potential for adverse he alth effects. To better understand the debate, we critically reviewed published and unpublished reports to assess whether differences in met hodological approach or quality could explain the variable results rep orted. We considered studies on acute human health effects of inhalati on exposure to MTBE either alone or in gasoline (19 reports) as well a s clinical use of parenteral MTBE to dissolve cholesterol gall stones (12 reports). Each study was reviewed from three perspectives (epidemi ology, industrial hygiene, and, clinical diagnostics), judged satisfac tory, limited adequacy, or unsatisfactory for each criterion, and grou ped into one of three categories from most to least adequate in overal l methodology. The studies judged most adequate on individual criteria and those with highest overall adequacy found no significant associat ion between MTBE exposure and symptoms. We propose that the persistent debate has been fueled by the findings of methodologically weak hypot hesis-generating studies.