Fipronil not only affects ants, termites and lice in pets, a use for which it is sold to individuals, as well as corn pests, which justifies its use in agriculture. It also seriously affects a multitude of species and it is in particular its effect on bees that has caused it to be banned in France since 2005 and in Europe since 2013, only twenty years after it was put on the market in 1993. But it remains widely used in South-East Asia where it leads sales, and in both Americas. In the United States, the phenylpyrazole family to which Fipronil and neonicotinoids belongs represent one third of the phytosanitary product market. The worldwide market for Fipronil alone stood at just over 400 million euros in 2018 and its manufacturer, BASF, expects sales of over 510 million euros in 2027. And this despite real impacts on the insects.
Lack of knowledge of the impact of Fipronil on natural environments
However, little was known about the impact of the pesticide on natural environments. Janet Miller, a researcher at Colorado State University (United States) has just filled this gap in an article published in Science Advances. One of the interests of the study is indeed to have studied the aquatic environment itself and not only the midges usually exposed to this member of the phenylpyrazole family. The other originality of this work is that it is not only interested in the basic molecule, but also in its four main metabolites, substances resulting from the degradation of the original product which is not very persistent in nature and not very volatile. . Of the four metabolites studied, only one has no effect on the environment, the other three are more toxic than Fipronil.
Fragments of nature brought to the laboratory
Janet Miller and her team built reconstructions of fast-flowing riverbeds on 36 plateaus, plunging them into streams for animal and plant species to colonize them. These “mesocosms” were then brought to a specialized laboratory in Fort-Collins (Colorado) where they were subjected for thirty days to levels of Fipronil and its metabolites representative of what is found in nature. All of them have been shown to be highly toxic to poorly studied species such as stoneflies, mayflies and trichoptera. These small, winged insects emerge in the spring after spending the winter as larvae. These are natural water quality indicators and one of the bases of the food chain, especially for a large number of birds. The study shows that their numbers drop drastically when exposed to pesticides. The availability of food for birds is not the only ecological consequence of this pollution. The larvae “graze” in fact the algae which covers the pebbles of rivers. Less numerous, they allow these plants to better colonize the environment.
At the same time, the researchers took water samples from rivers in agricultural and urban areas in five different regions of the United States where 70% of rivers contain levels of pesticides above authorized standards. Fipronil alone was found at levels above American standards on average in 16% of the country’s rivers. But with great regional disparities. In the Southeastern United States, 51% of rivers contain it compared to 9% in the northern Pacific coast.