This article carried in the Guardian is based on a recent paper which can be viewed here.
Guardian ‘Highly toxic insecticides used on cats and dogs to kill fleas are poisoning rivers across England, a study has revealed. The discovery is “extremely concerning” for water insects, and the fish and birds that depend on them, the scientists said, who expect significant environmental damage is being done.
The research found fipronil in 99% of samples from 20 rivers and the average level of one particularly toxic breakdown product of the pesticide was 38 times above the safety limit. Fipronil and another nerve agent called imidacloprid that was found in the rivers have been banned from use on farms for some years.
There are about 10 million dogs and 11 million cats in the UK, with an estimated 80% receiving flea treatments, whether needed or not. The researchers said the blanket use of flea treatments should be discouraged and that new regulation is needed. Currently, the flea treatments are approved without an assessment of environmental damage.
“Fipronil is one of the most commonly used flea products and recent studies have shown it degrades to compounds that are more toxic to most insects than fipronil itself,” said Rosemary Perkins at the University of Sussex, who led the study. “Our results are extremely concerning.”
Prof Dave Goulson, also at the University of Sussex and part of the team, said: “I couldn’t quite believe the pesticides were so prevalent. Our rivers are routinely and chronically contaminated with both of these chemicals.
“The problem is these chemicals are so potent,” he said, even at tiny concentrations. “We would expect them to be having significant impacts on insect life in rivers.” One flea treatment of a medium-sized dog with imidacloprid contains enough pesticide to kill 60 million bees, he said.
The first report of high levels of neonicotinoids such as imidacloprid in rivers came in 2017 from the conservation group Buglife, although that study did not include fipronil. Aquatic insects are known to be vulnerable to neonicotinoids and Dutch research has shown chronic waterway pollution led to sharp drops in insect numbers and falls in bird numbers. Aquatic insects are also declining due to other pollution from farms and sewage, with just 14% of English rivers in good ecological health.
The new study, published in the journal Science of the Total Environment, includes almost 4,000 analyses on samples gathered by the Environment Agency in 20 English rivers between 2016-18. These ranged from the River Test in Hampshire to the River Eden in Cumbria.’
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