Research has recently found that the highly toxic insecticides used on cats and dogs to kill fleas are poisoning England’s rivers. Scientists believe that significant environmental damage is being done to important water insect populations, down at the bottom of the freshwater food chain.
Despite their use being totally banned on farms, fipronil and a neonicotinoid called imidacloprid are the most commonly used active components in flea products for your dog. Researchers from Sussex University have found that England’s rivers are routinely and chronically contaminated with both of these insecticides.
Caddis fly larvae: if the larvae are killed by pollution, the Odonata and birds that eat the adult flies are affected too.
Fipronil is particularly dangerous because it degrades into compounds that are even more toxic to most water insects than the fipronil itself. It and its breakdown products have been found in 99% of the water samples taken by the Environment Agency from 20 rivers across England, between 2016 and 2018. The average level of one particularly toxic breakdown product, fipronil sulfone, was 38 times larger than the permitted safety limit.
Agricultural use of fipronil and imidacloprid was banned in 2017, so the researchers found their presence in such concentrations in our rivers, at first, problematic. Then it was discovered that the highest levels of the pesticides were downstream from water treatment plants: urban areas are the main source, not farmland.
 Adult flea;  there are 66 UK licensed products containing fipronil and 21 containing imidacloprid.
The researchers have concluded that there is really no other possible source for the pollution than flea treatments for pets. Even at tiny concentrations, these chemicals are very potent: one imidacloprid treatment for a medium sized dog contains enough pesticide to kill 60 million bees*.
There are 66 veterinary products containing fipronil and 21 containing imidacloprid licenced for use in the UK. Pet owners are encouraged to treat their animals with these toxins every month whether the flea treatment is needed or not.
It is possible that tonnes of these insecticides are being applied to our pets every year and most of it ends up in our waterways. The washing of pets flushes fipronil into sewers and subsequently into rivers; dogs swimming in rivers, streams and ponds is another pathway for contamination.
There are about 10 million dogs in the UK, with an estimated 80% of them receiving flea treatments. These are broad spectrum insecticides, killing not only the fleas on your dog but a wide range of other insects as well, important water insects among them.
There are particular dangers, in these dangerous times, to damaging the basis of the freshwater food chain. We will examine this and how it relates to our park in more detail tomorrow in Part Two of this post…..
*We have been unable to find the source of this horrifying statistic but we have seen it reported on several reputable sites.