Development of an aquatic exposure assessment model for Imidacloprid in sewage treatment plant discharges arising from use of veterinary medicinal products

Abstract

Background Imidacloprid is an active ingredient included in plant protection, biocidal and veterinary medicinal products (VMPs). VMPs containing Imidacloprid are formulated as spot-on products or collars and designed to protect pets, predominantly dogs and cats, from parasite infestation. Monitoring data collected under the Water Framework Directive between 2016 and 2018 showed detectable and varying levels of Imidacloprid in the UK surface water bodies. The aim of the work was to investigate the potential contribution of VMPs by developing a model for predicting the emissions from sewage treatment plants from the use of dog and cat spot-on and collar VMPs. Due to the absence of appropriate exposure models for VMPs, the model was built based on the principles of environmental exposure assessment for biocidal products. Results Three emission paths were considered to be the most likely routes for repeated emissions to waterways from the use of spot-on and collar VMPs, i.e., transfer to pet bedding followed by washing, washing/bathing of dogs, and walking dogs in the rain. The developed model was used to calculate the Imidacloprid concentrations in surface water after discharge from wastewater treatment plants. Realistic worst-case input parameters were deduced from sales and survey data and experimental studies. Modelled total concentrations in surface water for each pathway ranged from 0.84 to 4.8 ng/L. The calculated concentrations did not exceed the ecological thresholds for the most sensitive aquatic invertebrate organisms and were found to be much lower than the UK monitoring data for river water. For example, the calculated concentration from the bathing/washing of dogs was < 3% of the highest levels of Imidacloprid measured in surface waters. Conclusion In conclusion, a model has been successfully built and applied. The modelled data indicate that these VMPs make only a very small contribution to the levels of Imidacloprid observed in the UK water monitoring programme. Further, calculated concentrations do not exceed ecotoxicological threshold values indicating acceptable chronic safety to aquatic organisms.

Dead in the water: comment on “Development of an aquatic exposure assessment model for imidacloprid in sewage treatment plant discharges arising from use of veterinary medicinal products”

“…Furthermore, there is a lack of clarity surrounding the amount of imidacloprid Fig. 1 Flow diagram depicting Scenario 2/the "worst case scenario" presented by Anthe et al [1], illustrating the daily flow of imidacloprid, resulting from bathing dogs, through a standard STP (Sewage Treatment Plant) serving a human population of 10,000 people. Square brackets indicate amount of imidacloprid in grams and percentage of total imidacloprid applied per day.…”

“…F sim = fraction of dogs bathed per day (simultaneity factor), F washing = emission fraction of imidacloprid released due to bathing. F sim and F washing from Anthe et al [1] assumed to be present on, and so available for release from, pets treated with collars. The authors calculate this amount by dividing the quantity of imidacloprid in collars by 240, that being the number of days registered duration of efficacy for such collars.…”

“…Author details 1 School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK. 2 Chipping Norton Veterinary Hospital, Banbury Road, Chipping Norton, Oxfordshire OX7 5SY, UK.…”

“…Anthe et al [1] present a model, funded by Bayer, manufacturer of imidacloprid, that estimates imidacloprid levels in emissions from UK sewage Open Access *Correspondence: rp442@sussex.ac.uk 1 School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK Full list of author information is available at the end of the article treatment plants (STPs) resulting from the use of dog and cat spot-on and collar veterinary medicinal products (VMPs) containing imidacloprid, and thereby calculate a predicted environmental concentration (PEC) in waterways. Anthe et al 's model estimates the amount of imidacloprid applied daily to a population of cats and dogs in the catchment of an STP serving a human population of 10,000, then estimates how much of that imidacloprid passes from treated pets via STPs to waterways per day, via three scenarios-bathing pets, washing pets' bedding, or walking in rain-based on the likelihood of each scenario occurring per day.…”

Authors’ response on Perkins et al. (2021) “Dead in the water: comment on “Development of an aquatic exposure assessment model for imidacloprid in sewage treatment plant discharges arising from use of veterinary medicinal products”

“…Monitoring data collected under the Water Framework Directive between 2016 and 2018 showed detectable and varying levels of Imidacloprid in the UK surface water bodies. Anthe et al [1] investigated the potential contribution of VMPs by developing a model to predict the emissions from sewage treatment plants from the use of dog and cat spot-on and collar VMPs. Due to the absence of appropriate exposure models for VMPs, the model was built based on the principles of environmental exposure assessment for biocidal products under the biocidal product regulation (BPR).…”