A study showed that highly toxic insecticides used in cats and dogs to kill fleas are poisoning England’s rivers. Scientists say the discovery is “extremely related” to water insects and the fish and birds that depend on them, and they expect to cause significant damage to the environment.
The study found that in 99% of samples from 20 rivers, the content of fipronil was high, and the average content of a particularly toxic pesticide decomposition product was 38 times the safety limit. The fenoxtone found in the river and another nerve agent called imidacloprid have been banned on farms for many years.
There are approximately 10 million dogs and 11 million cats in the UK, and it is estimated that 80% of people will receive flea treatment (whether needed or not). The researchers said that blind use of flea therapy is not recommended, and new regulations are needed. Currently, flea treatments are approved without environmental damage assessment.
Rosemary Perkins of the University of Sussex, who was in charge of the research, said: “Fipronil is one of the most commonly used flea products. Recent studies have shown that it can be degraded to more insects than fipronil itself. More toxic compounds.” “Our results are very worrying.”
Dave Goulson, a research team member also at the University of Sussex, said: “I can’t fully believe that pesticides are so common. Our rivers are often polluted by these two chemicals for a long time. .
He said: “The problem is that these chemicals are so effective,” even in small concentrations. “We hope they will have a significant impact on the life of insects in the river.” He said that a pesticide that uses imidacloprid to treat flea in medium-sized dogs is enough to kill 60 million bees.
The first report of high levels of neonicotinoids (such as imidacloprid) in rivers was made by the conservation group Buglife in 2017, although the study did not include fipronil. Aquatic insects are susceptible to neonicotinoids. Studies in the Netherlands have shown that long-term waterway pollution has led to a sharp decline in the number of insects and birds. Due to other pollution from farms and sewage, aquatic insects are also decreasing, and only 14% of British rivers have good ecological health.
The new research, published in the journal Comprehensive Environmental Science, includes nearly 4,000 analyses of samples collected by the Environment Agency in 20 British rivers between 2016-18. These range from the River Test in Hampshire to the River Eden in Cumbria.
Fipronil was detected in 99% of the samples, and the highly toxic decomposition product Fipronil sulfone was found in 97% of the samples. The average concentration is 5 times and 38 times higher than its chronic toxicity limit, respectively. There are no official restrictions on these chemicals in the UK, so the scientists used the 2017 assessment report produced for the California Water Quality Control Board. Imidacloprid was found in 66% of the samples, and the toxicity limit was exceeded in 7 out of 20 rivers.
Fipronil was banned from use on farms in 2017, but it was rarely used before then. Imidacloprid was banned in 2018 and has been relatively rarely used in recent years. Researchers found the highest levels of pesticides downstream of water treatment plants, indicating that urban areas are the main source, not farmland.
As we all know, washing pets can flush fipronil into the sewer and then into the river, and dogs swimming in the river provide another way of pollution. Gulson said: “This must be the flea treatment that caused the pollution.” “Really, there is no other imaginable source.”
In the UK, there are 66 licensed veterinary products containing fipronil and 21 veterinary drugs containing imidacloprid, many of which are sold without a prescription. Regardless of whether flea treatment is required, many pets are treated every month.
Scientists say this needs to be reconsidered, especially in winter when fleas are uncommon. They said that new regulations should also be considered, such as requiring prescriptions and assessing environmental risks before being approved for use.
“When you start using any kind of pesticides on a large scale, there are often unintended consequences,” Gulson said. Obviously, something went wrong. There is no regulatory process for this particular risk, and it clearly needs to be done. ”
Matt Shardlow of Buglife said: “Three years have passed since we first emphasized the harm of flea treatment to wildlife, and no regulatory measures have been taken. The serious and excessive pollution of fipronil to all water bodies is shocking, and the government urgently needs to ban it. Use fipronil and imidacloprid as flea treatments.” He said that several tons of these insecticides are used in pets every year.