MTBE's Effects

In response to the 1990 Clean Air Act, oxygenators such as MTBE (methyl tertiary butyl ether) were added to fuels in concentrations up to 15% in order to reduce carbon monoxide pollution. It was only when acute health complaints-an increase in headaches, nausea, and eye, nose, and throat irritations-surfced following this increase in MTBE use that researchers began to study the possible health effects of the compound. Earlier studies had looked at the effect of pure MTBE on healthy individuals. However, a study by Nancy Fiedler and colleagues at the University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School in Piscataway, New Jersey, is the first to study controlled exposures of individuals to MTBE in gasoline vapor at concentrations that mimic real-life exposures such as refueling or driving situations [EHP 108:753-763]. The researchers compared the symptoms, psychophysiologic reactions , and neurobehavioral performance of two experimental groups during exposure to four controlled exposure conditions: dean air, regular gasoline fiumes, and fumes of gasoline containing either 11% or 15% MTBE. Researchers compared one group of 12 individuals selected based on their self-report of symptoms associated with MTBE exposure with another group of 19 control individuals without self-reported sensitivities. The exposures occurred one week apart and took place in a controlled environment facility. After a 5-minute relaxation period known as the baseline period, subjects were exoe for 15 minutes to one of the four exposure conditions. After each exposure, subjects rated their experience of 42 diffierent symptoms assocated with MTE and solvent exposure, anxiety, depression, and breatling problems. They also rated the testing environment on factors that might have aflctd their symptom reports, and completed odor questionnaires assessing the intensity of and irritation caused by the gasoline odor in the room at the time. The subjects took a computerized driving test to test the effects of MTBE on functions such as reaction time and peripheral vision. Researchers measured psychophysiologic responses, finger temperature , finger pulse volume, and the percentage of carbon dioxide in exhaled breath (an indicator of hyperventilation), and the measures were compared to those taken during the baseline period. Before departing each day, subjects were asked to guess which exposure condition they had experienced during that session. The researchers found that, compared with the control group, the group of sensitives reported significantly more total symptoms when exposed to gasoline with 15% MTBE than when exposed to gasoline with …