Biomonitoring and evaluation of permethrin uptake in forestry workers using permethrin-treated tick-proof pants

We conducted a randomized case–control trial to analyze uptake of the insecticide/arcaricide permethrin in wearers of permethrin-impregnated and non-impregnated pants in German forestry. Eighty-two male workers were each equipped for a 16-week period with permethrin-treated (test group) or with non-treated work pants (control group). Pants with or without lining to protect against cuts, obtained from two different distributors, were worn in each group. Urinary permethrin metabolite levels were measured by GC-MS/MS before, during and after wearing of the pants. Permethrin uptake was calculated using additional questionnaire data. In the control group, metabolite levels in the range of environmental background exposure (median: ~0.5 μg/l) were measured. Subjects wearing impregnated pants showed consistently significantly higher exposure levels even before the first use of the pants with a maximum after 1 week of wearing the pants (median: ~12.5 μg/l). Significant differences in internal exposure were found depending on which of the distributors the pants came from. Metabolite levels decreased probably due to permethrin losses associated with laundering the pants. Calculated permethrin uptake is below the value corresponding to the WHO-proposed acceptable daily intake. Based on our data, a marginally increased cancer risk compared with the general population cannot be excluded when wearing impregnated pants over a working-lifetime period.