Swimming emissions from dogs treated with spot-on fipronil or imidacloprid: Assessing the environmental risk

Fipronil and imidacloprid are increasingly recognised as contaminants of concern in aquatic environments. This study aimed to quantify swimming emissions from dogs treated with spot-on fipronil or imidacloprid, assess the associated environmental risks and evaluate whether current label instructions on swimming restrictions are adequate.

Emissions from swimming were measured for 49 dogs treated with spot-on fipronil or imidacloprid on days 5, 14 or 28 post-application. The environmental risk was assessed by calculating risk quotients, dividing the predicted environmental concentrations by the predicted no-effect concentrations for freshwater ecosystems.

Mean washoff ranged from 4% to 0.4% of the applied dose for fipronil and 10% to 1.4% for imidacloprid across the 5-28-day period. Risk quotients indicate a risk to aquatic ecosystems throughout the products' duration of action.

The results may underestimate emissions for fipronil, as swimming is permitted from 3 days post-application and measurements began on day 5.

This study highlights clear ecological risks from spot-on parasiticides and provides evidence that current label instructions on swimming do not provide sufficient environmental protection. Risk-based parasite control strategies and extended swimming restrictions are recommended. Regulatory review of environmental risk assessments and mitigation measures is warranted to protect aquatic environments.