Water quality monitoring 2024: pet treatments
Introduction
This report presents the results of the 2024 water quality monitoring for fipronil and imidacloprid, two active ingredients used in a range of externally applied veterinary treatments (spot-on treatments and collars) for the control of external parasites primarily in cats and dogs.
Neither imidacloprid nor fipronil are listed in The Scotland River Basin District (Standards) Directions 2024. However, both have been identified as substances of increasing concern in surface waters. Imidacloprid was included in the 1st Water Framework Directive Watch List in 2015 (EU/ 2015/495) and fipronil was added to the 4th Watch List in 2022 (EU/2022/1307). Imidacloprid is also classed as hazardous to groundwater.
This report and the data from our SEPA monitoring has been shared with the UK cross-government Pharmaceuticals in the Environment (UK PiE) group. In August 2025, the UK PiE group set out a roadmap of activities to address the levels of these two substances in UK waters.
What we found
In 2024, we collected water samples from 298 locations across Scotland. There were 274 surface water locations and 24 groundwater locations.
We analysed a total of 844 samples. 820 of these were surface water samples and 24 were groundwater samples.
Surface waters
Fipronil was detected at least once in 16% of surface water locations and in 7% of the samples analysed.
The concentrations detected ranged from 1.06 ng/l to 19.95 ng/l (nanogram per litre).
The highest concentration was measured in a sample from the Quhomery Burn, a tributary of the River Ugie in Aberdeenshire.
Imidacloprid was detected at least once in 4% of surface water locations and 1% of the samples analysed.
The concentrations detected ranged from 6.95 ng/l to 82.94 ng/l, with the highest concentration measured in a sample from the River Annan in Dumfries and Galloway.
Groundwater
No fipronil or imidacloprid was detected in any of the 24 groundwater samples collected in 2024.
What next
Monitoring in surface water and groundwater will continue through 2025 and 2026 and datasets and reports will be published as they become available.