A two-dimensional probabilistic acute human-health risk assessment of insecticide exposure after adult mosquito management

Ultra-low-volume (ULV) aerosol applications of insecticides are used to manage high densities of adult mosquitoes. We used two-dimensional probabilistic risk assessment methodologies to evaluate three pyrethroid insecticides (phenothrin, resmethrin, and permethrin), pyrethrins, and two organophosphate insecticides (malathion and naled), applied by truck-mounted ULV sprayer. Piperonyl butoxide, a synergist commonly used in pyrethroid and pyrethrins formulations, was also assessed. The objective of our study was to evaluate probabilistically if a deterministic human-health risk assessment of mosquito insecticides was sufficiently conservative to protect human-health. Toddlers and infants were the highest risk groups while adult males were the lowest risk group assessed in this study. Total acute exposure ranged from 0.00003 to 0.0003 mg/kg day for the chemicals and subgroups assessed examining inhalation, dermal, oral, and hand-to-mouth exposure. We used the risk quotient (RQ) method for our risk assessment, which is calculated by dividing the total potential exposure for each subgroup and chemical by its ingestion toxic endpoint value (RfD). Mean RQs ranged from 0.000004 to 0.034 for all subgroups and chemicals, with none exceeding the RQ level of concern. Naled had the highest RQs of any chemical assessed while PBO had the lowest. Sensitivity analysis demonstrated that the exposure from inhalation and deposition contributed the largest variance to the model output. Results support the findings of previous studies that the risks from adult mosquito management are most likely negligible, and that the human-health deterministic risk assessment is most likely sufficiently conservative.