Scientists have called for a rethink of the blanket use of flea treatments for pets after finding high levels of chemicals at protected marine harbours on the south coast of England.
Imidacloprid, a neonicotinoid insecticide commonly used in flea and tick treatments for cats and dogs, was found in Chichester and Langstone harbours at concentrations that could harm aquatic life.
Leon Barron, reader in analytical and environmental sciences at Imperial College London, said: “Out of so many chemicals detected, the presence of pet tick and flea treatments in the harbours was especially concerning. We urgently need to reassess the practice of blanket preventative treatment of our dogs and cats to help bring the risk down.”
Researchers took samples at Chichester and Langstone harbours near Portsmouth
UNIVERSITY OF PORTSMOUTH/PA
Imidacloprid was banned for use in farming seven years ago but is still sold in large quantities as a precaution against fleas. It can reach waterways by owners washing pets, flushing their waste down lavatories and by people washing their hands after applying treatments.
A study by Barron and colleagues, published on Monday in the journal Environment International, involved researchers collaborating with citizen scientists to analyse seawater, seaweed and shellfish from Chichester and Langstone. Both harbours are designated as sites of special scientific interest, meaning their fauna and flora are considered important.
The researchers found 105 unique compounds, including 67 pharmaceuticals, 29 pesticides and nine recreational drugs, in samples taken from 21 sites in the two sites during spring and autumn 2022. Chemical readings spiked significantly during wet weather, when combined sewer overflows (CSOs) discharged raw sewage directly into the sensitive environments. Imidacloprid was found in more than half of the samples taken.
The true risk of chemicals such as imidacloprid, sold in large quantities as a flea treatment, may be underestimated
ALAMY
Thomas Miller from Brunel University of London, an author of the research, said: “CSO discharges were an obvious source of chemical pollution in these waters. Our study found that some chemicals increased by over a hundredfold in water after these discharges, making them a high risk to aquatic wildlife.”
Sewage was spilled across England for the longest time on record last year, for 3.6 million hours. Southern Water, which operates around Chichester and Langstone, contributed more than 300,000 hours to the tally. The Times’ Clean it Up campaign is calling for curbs on such spills.
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Nine of the pesticides identified at the harbours are no longer approved for agricultural use in the UK, with some having been banned for more than a decade. It is unclear where these persistent chemicals are coming from, but it is thought they may be linked to historical use.
Other substances of interest included 1,3-Diphenylguanidine, a compound used in rubber production, which suggests potential contamination from tyre-wear particles and road run-off, particularly after rainfall.
The research also examined how these chemicals are impacting marine life in Langstone harbour. Generally, seaweed (Fucus vesiculosus) was found to accumulate a higher burden of chemicals compared with shellfish such as oysters.
Jasmin Uhlhorn, a PhD student from Brunel University and a co-author of the study, said: “While studies on chemical pollution in these environments are limited, the findings suggest that the true risks of chemical mixtures may be underestimated, particularly for marine species.”
Nick Mills, the director of environment and innovation at Southern Water, said: “Tackling the presence of these chemicals is a challenge for society as a whole. While we are investing heavily in cutting storm overflows, and are removing more and more contaminants through wastewater treatment, the most sustainable solution is to meet the problem at source by changing legislation to restrict or ban certain chemicals and keep them out of pipes in the first place.”
The Times is demanding faster action to improve the country’s waterways. Find out more about the Clean It Up campaign.
