Filling gaps between exposure modeling and the analysis of urinary biomarkers using personal air monitoring: An intervention study of permethrin used in home insecticide spray

Permethrin is one of the most widely used active ingredients in spray-type home insecticides. However, indoor permethrin exposure resulting from the use of home insecticides is not well-characterized, as measured permethrin concentrations in indoor environmental and biological media with a known application rate are scarce. We conducted an intervention study with four participants for seven days. We conducted personal air monitoring and collected 24-h urine samples in which we quantified time-weighted average (TWA) permethrin concentrations in indoor air (C_air) and urinary concentrations of two permethrin metabolites, 3-phenoxybenzoic acid (3-PBA) and cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis/trans-DCCA). We also estimated (1) TWA C_air using a simple indoor air model and (2) urinary excreted (UE) mass using a simple excretion model with both estimated and measured TWA C_air. Measurements of TWA C_air from personal air monitoring were lower than those estimated from the indoor model by a factor of 2.9 to 49.4. The ratio of estimated to measured UE mass ranged 3.5–18.2 when using estimated TWA C_air and 1.1–2.9 when using measured TWA C_air. Smaller ratios in estimating internal permethrin exposure from personal air monitoring suggest that personal air monitoring could reduce uncertainties in permethrin exposure assessment resulting from the use of spray-type insecticides.