Development of dermal and respiratory sampling procedures for human exposure to pesticides in indoor environments

No standard methods presently exist for measuring air and surface residues in indoor environments following pesticide applications. Four studies of chlorpyrifos broadcast applications for flea control were conducted to test preliminary sampling guidelines developed by Health and Welfare Canada. Air and wipe samples were collected for 24 hr following 0.5% or 0.48% chlopryifos applications. Ventilation from open doors or windows reduced air concentrations substantially. Air concentrations also varied with sampler height; i.e., greater near the floor than at one m above the floor. Wipe sampling from aluminum foil exhibited high precision (less than 10% coefficient of variation), and wipe sampling of carpets and other surfaces did not show variability in excess of the variability in initial pesticide deposits produced by the application procedures. Residues recovered from treated surfaces decreased by 60-70% over 24 hr, while residues on untreated surfaces increased 200-300% over this period. The Guidelines for Assessment of Indoor Occupant Exposure to Pesticides developed by Health and Welfare Canada have been revised in light of these findings, and provide a set of standard procedures for monitoring indoor air and surface residues. Further studies will be required to determine human exposures and health risks resulting from indoor pesticide applications.