A human biomonitoring study evaluating exposure to imidacloprid among pet owners following the use of ectoparasite treatments

Imidacloprid (IMI), a neonicotinoid insecticide (NNI), is commonly used in ectoparasite treatments for pets. With the rise of pet ownership globally, there is also a rise in ectoparasite treatment use and a potential for human exposures to these chemicals. This study explored human exposures to IMI following IMI-based ectoparasite treatment application to household pets, using human biomonitoring methods. In this study, 67 participants in Irish households that applied IMI-based ectoparasite treatments provided five first-morning void urine samples for five days in a row. The first morning urine sample was collected the morning before treatment application, and then one sample was collected each of the following four days. All samples (n = 335) were analysed for IMI, and its metabolites, IMI-olefin and 4/5-hydroxy-IMI (OH-IMI). The study results show a pronounced increase in pet owners' urinary concentrations of IMI, IMI-olefin and OH-IMI in the days following the application. The detection frequency for IMI-olefin increased from 26% in pre-treatment samples to over 74% in post-treatment samples. Participants who had more physical interactions with the treated pet had markedly higher urinary concentrations of the IMI-olefin, as did participants who had used a larger quantity of IMI. However, all urinary concentrations indicated IMI exposures were below the Acceptable Daily Intake (ADI). Urinary concentrations persisted over the sampling period, with no notable decrease in concentrations of IMI-olefin or OH-IMI after five days of sampling. Future studies should aim to conduct sampling over a longer timeframe to find the duration of exposure from IMI product use.