PHYSIOLOGICALLY-BASED ASSESSMENT OF HUMAN EXPOSURE TO URBAN AIR-POLLUTANTS AND ITS SIGNIFICANCE FOR PUBLIC-HEALTH RISK-EVALUATION

Exact measurements or modeling of human exposures to environmental pol lutants are of crucial importance for a realistic evaluation of public health risks. Current concepts, however, often use assumptions that r esult in overly conservative assessments of public health risks. Too f requently the dose of the pollutant retained in the body is approximat ed by oversimplified predictions assuming that all that is inhaled rem ains in the organism, that pollutant concentrations in various microen vironments are identical to those recorded by remote monitors, that th e residence indicates the sire where people spend all their time, and that the urban population is continuously exposed to outdoor air for 2 4 hr/day and 70 years/lifetime. The review shows that in intermittent exposures only a fraction of inhaled toxicants remains in the body, th at pollutant concentrations differ largely from one microenvironment t o another, and that human activity patterns must be incorporated in ev ery realistic exposure assessments. Specifically, the probability of b eing exposed to a short peak of ozone is predetermined in variable urb an concentrations primarily by the coincidence of exercising outdoors at the time and site of elevated ozone levels. When combined with a ph ysiologically based exposure evaluation, this probabilistic approach p rovides a scientifically sound estimate of actual occurrences of adver se exposures and a realistic assessment of potential health hazards.