Larry S. Andrews

Acute Exposure to Low-Level Methyl Tertiary-Butyl Ether (MTBE): Human Reactions and Pharmacokinetic Response

AbstractThis two-part investigation assessed the effects of 1-h exposures to methyl tertiary-butyl ether (MTBE) at an ambient concentration of 1.7 ppm on healthy adults. In one part, four subjects participated in a pharmacokinetic study of blood levels of MTBE. Concentration in blood rose 20-fold from baseline to 17 μg/L by the end of exposure and declined to one-half that level at 40 min after exposure. In another part, 43 subjects participated in a double-blind study of reactions to exposures to MTBE (1.7 ppm), to a mixture of 17 volatile organic compounds (VOCs) (7.1 ppm), and to air. Subjects rated symptoms (e.g., irritation, headache, mental fatigue), their mood, and various environmental attributes (e.g., odor, air quality, temperature), and also took computerized performance tests during exposures. Measures of eye irritation (e.g., tear-film breakup, eye redness) and nasal inflammation (i.e., measurement of polymorphonuclear neutrophilic leukocytes, PMNs) were taken before and after exposure as obj...

Application of in Vivo Data on Chemical—Biological Interactions

Chemical-biological (CB) interactions are governed by both the structure of the chemical and the properties of the biological system. The ability of a drug or chemical to be absorbed from the lung, skin, or gastrointestinal tract and to enter the body is a CB interaction. Unless the chemical structure is fat-soluble enough to dissolve in the lipoprotein membrane, or small enough to pass through pores, or it mimics an endogenous substance that is actively transported, the chemical cannot move across membranes or skin. Ultimately, for a chemical to exert an effect it must be absorbed and enter the blood. Once in the blood, a chemical’s further disposition is governed by its pharmacokinetic characteristics, i.e., its distribution and elimination from body compartments.