Toxicological and Performance Aspects of Oxygenated Motor Vehicle Fuels (1996) / Chapter Skim
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EXECUTIVE SUMMARY
EXECUTIVE SUMMARY
Pages 1-16
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Additional concerns have been raised about the detection of low levels of MTBE in some samples of groundwater. Due to the public concern over the potential health effects of MTBE-oxygenated fuels, more than $2 million of scientific studies have been conducted by EPA and others to investigate the reported symptoms.
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. The purpose of the interagency report was to provide a review of the scientific information on oxygenated fuels and to assess effects of the winter oxygenated-fuels program on air quality, fuel economy, engine performance, water quality, and public health.
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AIR QUALITY CRITIQU E OF ~ NTERAGENCY DRAFT REPORT The interagency report concludes that there have been substantial reductions in ambient CO concentrations in the past 20 years and that vehicle emission controls have been a major factor in this reduction. The committee agrees with these conclusions.
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The committee agrees with the interagency report that, under many fuel-control systems, oxygenated fuels decrease CO emissions under Federal Test Procedure conditions (at 75°F)
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If a beneficial effect of reduction in CO is demonstrated in that field study, a carefully designed study should then investigate the effects of oxygenated fuels on emissions of NOX, VOCs, and toxic air pollutants on winter air quality, using appropriate controls and accounting for differences in such factors as fleet population, high-emitting vehicles, inspection and maintenance programs, and local fleet characteristics. The introduction of toxic organic compounds into the air, as well as a fuel-economy penalty, should also be addressed in such a study.
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WATER QUALITY CRITIQUE OF INTERAGENCY DRAFT REPORT The interagency report discussed water-quality issues arising from the use of fuel oxygenates (primarily MTBE) and their movement in the hydrologic cycle.
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The large majority of states do not have any programs or requirements in place to monitor MTBE or other fuel oxygenates in stormwater runoff, groundwater, or drinking water. The absence of these monitoring data prevents an accurate assessment of exposure of human or aquatic biota to MTBE, possible health effects, and implementation of control measures to prevent adverse impacts.
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The lifetime exposures calculated for these scenarios are 10 times higher than the maximum daily exposures estimated on the basis of empirical data as summarized in the portion of the report prepared by the Health Effects Institute (HEI)
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The relationship between fixed-site community monitoring and personal exposures to MTBE and related air pollutants should be evaluated in order to determine the information value of using community monitoring for assessing human exposure. POTENTIAL H EALTH E FFECTS O F OXYG ENATES CRITIQU E OF ~ NTERAGENCY DRAFT REPORT The committee is in basic agreement with the evaluation of data presented in the interagency report with respect to the metabolism, disposition, and toxicokinetics of MTBE.
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By suggesting that "a relatively smaller proportion of persons" might have problems with exposure, the interagency report appears to ignore consistent findings in exposed workers and overlooks the possibility that typical occupational exposures may pose an overall problem, whether or not a more sensititive subpopulation exists. There are virtually no data to indicate that the reported acute health effects are confined to a sensitive subpopulation.
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The committee believes there should be better coordination between clinical observations, epidemiologic studies, and exposurechamber experiments regarding research on acute human health effects and exposure to oxygenated fuels. Improved clinical characterization of symptoms reported to be attributed to exposures from MTBE in gasoline is also needed and should take into account the actual types of symptoms experienced by individuals, the settings in which the symptoms occur (e.g., refueling versus driving)
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However, the committee does not recommend that ecological studies be undertaken at the present ~ -, -- -bird time, but rather that missing routine environmental-monitoring data on air and water begin to be collected, so that such studies can be conducted in the future. POTENTIAL HEALTH EFFECTS OF OTHER POLLUTANTS CRITIQUE OF INTERAGENCY DRAFT REPORT The committee agrees with the interagency report that the data are too limited to evaluate the effectiveness of the winter oxygenated-fuel program in lowering CO exposures to a level that would not affect cardiovascular morbidity and mortality.
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RISK ASSESSMENT CRITIQUE OF INTERAGENCY DRAFT REPORT With respect to the noncarcinogenic effects of MTBE resulting from lon~term, continuous inhalation, the interagency report's use of EPA's reference concentration (RfC)
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RESEARCH N REDS The National Research Council committee suggests that the portion of the report that was prepared by HE] be used as the framework and database (with appropriate additions and reinterpretations as described by the National Research Council committee)
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