Concern for wildlife as 100-fold increase in chemicals found in harbours
Insecticide used for pet flea treatment has been found in waters in south coast harbours.
Chemical pollution has increased by 100-fold in the waters of two south coast harbours which are home to sites of special scientific interest (SSSI), according to a new study.
Researchers from three universities have analysed the waters of Chichester and Langstone harbours and discovered 105 different pharmaceuticals, pesticides and illegal drugs including an insecticide used as a common pet flea treatment.
And the environmental scientists found that some of the chemicals increased by over 100-fold following rainy days which led to combined sewer overflows (CSOs) into the harbours which are on the border of Hampshire and West Sussex.
The team, made up of researchers from Brunel University, London, University of Portsmouth and Imperial College London, says that they are worried about the impact on the local wildlife in the 21 SSSIs in the area.
Dr Thomas Miller, from Brunel University, said: “CSO discharges were an obvious source of chemical pollution in these waters.
“Our study found that some chemicals increased by over 100-fold in water after these discharges, making them a high risk to aquatic wildlife.”
The study, carried out with the help of the Clean Harbours Partnership and published in the journal Environment International, examined 339 water samples which revealed 67 pharmaceuticals, 29 pesticides and nine recreational drugs.
It comes after the Environment Agency revealed that storm overflows spilled sewage into England’s rivers, lakes and coasts for new highs of more than 3.61 million hours in 2024.
The researchers found that seaweed soaked up more chemicals than shellfish and the insecticide imidacloprid, used a pet flea treatment, created the highest risk based on levels found in surface water.
Dr Leon Barron, from 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.”
The team also found the presence of 1,3-diphenylguanidine, which is used in rubber production and which they say could indicate pollution from tyre-wear particles and road run-off after rainfall events.
Lead author Jasmin Uhlhorn, a PhD student from Brunel University, said: “The research underscores the complexity of chemical mixtures present in transitional and coastal water systems, highlighting the need for more comprehensive monitoring to investigate their sources, including the impacts of CSO discharges.
“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.”
Professor Alex Ford, from the University of Portsmouth’s Institute of Marine Sciences, said: “The impact of these contaminants we are yet to fully understand, but it’s clear from our data that they increase substantially under storm events which discharge untreated sewage.”
CHP co-founder Rob Bailey said: “It is concerning to see such a large cocktail of chemicals being detected and hear their effects are largely unknown.
“As a community-based organisation we will continue to push for better monitoring of these protected marine habitats used by our members.”
