Controlled human exposure to methyl tertiary butyl ether in gasoline: symptoms, psychophysiologic and neurobehavioral responses of self-reported sensitive persons.

Abstract

The 1990 Clean Air Act mandated oxygenation of gasoline in regions where carbon monoxide standards were not met. To achieve this standard, methyl tertiary butyl ether (MTBE) was increased to 15% by volume during winter months in many locations. Subsequent to the increase of MTBE in gasoline, commuters reported increases in symptoms such as headache, nausea, and eye, nose, and throat irritation. The present study compared 12 individuals selected based on self-report of symptoms (self-reported sensitives; SRSs) associated with MTBE to 19 controls without self-reported sensitivities. In a double-blind, repeated measures, controlled exposure, subjects were exposed for 15 min to clean air, gasoline, gasoline with 11% MTBE, and gasoline with 15% MTBE. Symptoms, odor ratings, neurobehavioral performance on a task of driving simulation, and psychophysiologic responses (heart and respiration rate, end-tidal CO(2), finger pulse volume, electromyograph, finger temperature) were measured before, during, and immediately after exposure. Relative to controls, SRSs reported significantly more total symptoms when exposed to gasoline with 15% MTBE than when exposed to gasoline with 11% MTBE or to clean air. However, these differences in symptoms were not accompanied by significant differences in neurobehavioral performance or psychophysiologic responses. No significant differences in symptoms or neurobehavioral or psychophysiologic responses were observed when exposure to gasoline with 11% MTBE was compared to clean air or to gasoline. Thus, the present study, although showing increased total symptoms among SRSs when exposed to gasoline with 15% MTBE, did not support a dose-response relationship for MTBE exposure nor the symptom specificity associated with MTBE in epidemiologic studies.ImagesFigure 1Figure 2

Toxicokinetics of human exposure to methyl tertiary-butyl ether (MTBE) following short-term controlled exposures

“…The coefficient of variance between the paired samples was 0.12. Duplicate blood samples were collected and analyzed using the procedures as described here and by the Center for Disease Control and Prevention during the same time period ( Fiedler et al, 2000 ). No statistical differences were found between paired blood samples and the coefficient of variances across the two laboratories were 0.5 for MTBE and 0.4 for TBA.…”

Environmental factors in medically unexplained symptoms and related syndromes: the evidence and the challenge.

“…Rather than simply dismiss these unexplained symptoms or consider them as isolated symptoms, over the past few decades, practitioners, patients, and investigators have coalesced these symptoms into syndromes, including chronic fatigue syndrome (CFS), fibromyalgia (FM), chronic hypoglycemia, and irritable bowel syndrome. Similar and sometimes almost overlapping groups of symptoms have been delineated in the aftermath of a variety of ongoing chemical or other environmental exposures and include sick building syndrome (nonspecific building-related illness), atypical connective tissue disease after silicone breast implants, multiple chemical sensitivities (MCS), and most recently Gulf War syndrome and sensitivity to methyl tert-butyl ether (MTBE) (3). Investigators have pointed out the substantial overlap between one unexplained symptom classification and another, such that 30-50% of individuals with CFS, FM, and MCS qualify (based on self-reported symptoms) for at least one of the other diagnoses, and substantial percentages of those reporting illness after the Gulf War have symptom complexes overlapping with CFS and MCS (4-7).…”

First measurements of methyl tert-butyl ether (MTBE) in the ambient air in San Jose, Costa Rica

“…It has also been reported that human exposure to vapours of reformulated gasoline may produce headaches, nausea and eye, nose, and throat irritation. Other in vivo toxicological studies have demonstrated cytological anomalies [3,4]. Measurements in the ambient air of other inorganic pollutants, such as sulphur dioxide, nitrogen oxides, carbon monoxide and particulate matter and volatile organic compounds (VOCs) have been made frequently in the past in San Jose, but MTBE concentrations were not previously measured [5,6].…”