Environmental Exposure and Risks of Companion Animal Parasiticides In UK Surface Waters

Parasiticides are commonly and extensively used to treat and prevent parasitic infestations. Previously, environmental exposure from pet parasiticides were assumed to be negligible. However, with > 21 million cats and dogs within the UK, there is growing concerns surrounding the potential for these compounds to pollute the aquatic environment. Limited studies have been undertaken
across this entire research area, therefore, major data gaps exist. This thesis aimed to assess the exposure and potential risks of companion animal parasiticides to the aquatic environment.

Available UK pet parasiticide products were reviewed, identifying their active compounds. A prioritisation exercise was undertaken to determine the compounds with the greatest relative environmental risk to focus on in future research. Exposure modelling was employed to determine the potential temporal and spatial trends of the exposure of fipronil and imidacloprid across Yorkshire, England. A Liquid Chromatography- Tandem Mass Spectrometry (LC-MS/MS) analytical methodology was developed for a broader range of parasiticide compounds in order to analyse samples collected from surface waters across England in 2024. Simple risk assessments were undertaken using risk quotients for generated exposure data to determine whether any risk could
be identified.

The findings of this research confirm that fipronil and imidacloprid are detected within surface waters in England and at concentrations that may be posing a risk, this in agreement with previous literature. The major finding from this research were the significant data gaps that exist when considering exposure and risk of pet parasiticides in the aquatic environment, therefore fifteen research priorities
have been highlighted. These recommendations cover a broad range of topics including, chemical properties, transparency of data, exposure, hazards, risks and regulations. Future research should aim to address these recommendations. This thesis contributed to filling gaps and contributing to a growing body of research whilst also suggesting a direction for future research.