BREATH MEASUREMENTS AS VOLATILE ORGANIC-COMPOUND BIOMARKERS

A brief review of the uses of breath analysis in studies of environmen tal exposure to volatile organic compounds (VOCs) is provided. The U.S . Environmental Protection Agency's large-scale Total Exposure Assessm ent Methodology Studies have measured concentrations of 32 target VOCs in the exhaled breath of about 800 residents of various U.S. cities. Since the previous 12-hr integrated personal air exposures to the same chemicals were also measured, the relation between exposure and body burden is illuminated. Another major use of the breath measurements ha s been to detect unmeasured pathways of exposure; the major impact of active smoking on exposure to benzene and styrene was detected in this way. Following the earlier field studies, a series of chamber studies have provided estimates of several important physiological parameters . Among these are the fraction, f, of the inhaled chemical that is exh aled under steady-state conditions and the residence times, tau(i) in several body compartments, which may be associated with the blood (or liver), organs, muscle, and fat. Most of the targeted VOCs appear to h ave similar residence times of a few minutes. 30 min, several hours, a nd several days in the respective tissue groups. Knowledge of these pa rameters can be helpful in estimating body burden from exposure or vic e versa and in planning environmental studies, particularly in setting times to monitor breath in studies of the variation with time of body burden. Improvements in breath methods have made it possible to study short-term peak exposure situations such as filling a gas tank or tak ing a shower in contaminated water.