Measuring indoor human pesticide exposures and use of environmental data to generate a predictive model of exposure

Human exposure to semi-volatile chemicals is an inherent consequence of pesticide use. Conjecture (Berteau et al., 1989) regarding the magnitude of residential human exposure to pesticides has prompted considerable study by registrants, government agencies and others. Generating accurate exposure estimates requires knowledge of the fate, transport, and availability of surface pesticide residues.; Exposure monitoring studies were conducted that measured the extent and duration of human exposure during a variety of normal residential pesticide use scenarios. Chlorpyrifos (CP) is an ideal pesticide for biomonitoring since a single, stable biomarker, trichloropyridinol (TCP), is rapidly cleared in urine (Nolan et al., 1984). The magnitude of exposure measured in these monitoring studies was considerably less than previously estimated, but exposure continued much longer than predicted from short-term biomonitoring studies or indoor environmental residue measurements.; Subsequent studies measured the persistence and transferability of chlorpyrifos on carpet. Chlorpyrifos residue was semi-persistent, with a half-life (t _1/2) of 231 to 347 hrs. The corresponding transferable residue obtained by pressing a cotton cloth with a 30 lb roller had a rapid decline shortly following application (α-phase), but was much slower during later periods (β-phase), with a half-life of about 50 hrs. During the α-phase, carpet moisture enhanced the availability of surface residues.; These findings were experimentally evaluated during a scripted activity study (Jazzercise®) that included high surface contact with a treated carpet. Measured absorbed daily dosages (ADDs) of persons exposed on three different days following application were 1.3 (day 0), 1.7 (day 1) and 1.0 μg/kg body weight (day 7). Total carpet residue (TCR), transferable residue (TR), and air level measurements were used to predict exposure potential. TR was a better predictor of human exposure (ADDs) than either air levels or TCR.; Persons who were exposed to pesticide in their homes under normal conditions of use, and participants in experimental exposure studies absorbed similar amounts of chlorpyrifos. These data contributed to development of a predictive model of exposure. ADDs from a residential monitoring study compared favorably with predicted exposures based upon TR from carpet. These studies demonstrate that TR measurements are the best available means to develop accurate indoor human exposure estimates.