Flea control agents can endanger aquatic invertebrates

A research group recently found dangerous levels of insecticides in English rivers and determined that flea control products are likely to be responsible.

The study follows on from work published in the US and worldwide on environmental pollution with fipronil, fipronildegradates, and imidacloprid, which are often associated with contamination from flea and tick products that have been applied to domestic animals and passed through sewers. The studies relate to topical products rather than oral ones.

An article published February 10 in Science of the Total Environment suggests that water samples collected by the UK Environment Agency from 20 English rivers almost always contained fipronil and usually imidacloprid, both neurotoxic pesticides. The University of Sussex authors analyzed the authorities’ data and found that the mean concentration of fipronil was five times the chronic limit of toxicity.

While the mean imidacloprid concentration was below the chronic toxicity limit, seven of the 20 rivers were above the limit.

The samples with the highest concentrations of each chemical came just after sewage treatment plants, and the authors said the results back up their claim that the chemicals came from veterinary flea control products that flush household drains.

“These results suggest a need to reassess the environmental risks associated with the use of parasite control products and the environmental impact assessments these products undergo prior to regulatory approval,” the article reads. “A reassessment of the current protocols for treating ectoparasites may also be warranted.”

Researchers washed dogs treated with topical flea and tick products to measure the levels of pesticides that were flushed into sewers. (Courtesy Jennifer Teerlink, PhD / California Department of Pesticide Regulation)

Studies in the US find a link between pet products and pollution

An Arizona State University team found that fiprole (fipronil and its breakdown products) was ubiquitous in water samples collected by the U.S. Environmental Protection Agency from 2001-16. Samples from the wastewater from 12 sewage treatment plants in 2015-16 also contained these compounds in dangerous concentrations for chronically exposed aquatic invertebrates.

Researchers from the Biodesign Center for Environmental Health Engineering and the School of Sustainable Engineering and the Built Environment in the state of Arizona described these findings in the February 2019 issue of Water Research.

The Water Research article notes that previous studies suggest that fiprolene is toxic to aquatic invertebrates and pollinators at levels of parts per trillion, and that the breakdown products have half-lives of up to several hundred days. The authors called for further investigation and regulation of the non-agricultural use of fipronil, “in particular the selective treatment for controlling fleas and ticks in domestic animals”.

In another study, a California-based research team washed dogs either two, seven, or 28 days after using a fipronil product and found fipronil and fipronil sulfone in all samples. They published these results in Science of the Total Environment in 2017.

Twenty-eight days after application, the team found that fiprolen could be removed and flushed down the drain at the rate of milligrams per dog.

“Measurements of removable pesticide residues during routine bathing confirm that spot-on fipronil treatments contribute a significant mass fraction of the total fipronil load into the sewerage basin,” the article said.

If groomers and pet owners washed 25% of treated dogs within a week of use, that would account for all of the fiprole load in the sewers – based on measurements from water treatment plants in Northern California, the article said.

Jennifer Teerlink, PhD, environmental program manager for the California Department of Pesticide Regulation’s surface water program and lead author of the 2017 article on fipronil washed off by dogs, said she expected other sources – like water used to wash clothes or pets – to carry bedding also fipronil in the waterways, but in lower concentrations. She said the study didn’t look at how often dogs are bathed, and she thinks it’s good to look at data from professional dog groomers in particular.

Dr. Teerlink said she and her colleagues in the surface water protection program continue to investigate the sources and concentrations of pesticides in wastewater, mainly imidacloprid, fipronil and pyrethroids. This work includes the modeling of what proportion of fipronil that reaches water bodies comes from wastewater.

Pesticide levels in waterways have already raised enough environmental concerns to prompt changes in the use of some products. In 2017, the state changed the registration of sprays containing fipronil that were used outside of buildings to keep ants or termites out. The state banned its use during the November to February rainy season, reduced the maximum concentration and width of splashes outside of buildings, and banned its use on some impervious surfaces connected to runoff.

No products containing fipronil are registered for agricultural use in California, said Dr. Tar link. The Arizona state team separately found no association between fiprole concentrations and agricultural fipronil use.

Kelly D. Moran, PhD, senior scientist at the San Francisco Estuary Institute, co-authored a 2016 article published in Environmental Toxicology and Chemistry that shows that most of the fipronil and imidacloprid that enter sewage treatment plants are through her get into surface water. and flea and tick products were likely the major sources in sewage. The team found an amazing consistency of contamination per capita, she said. Dr. Teerlink was also one of the authors of this paper.

Dr. Moran has also worked as a wastewater treatment consultant and found that the levels of fipronil and imidacloprid in wastewater could hinder efforts by some cities to perform the purification required to reuse wastewater for drinking water. Disposing of waste from this process becomes more difficult with higher pesticide concentrations, she said.

Pesticides endanger the health of the ecosystem

Researchers from the US Geological Survey and the EPA stated in an article published in Environmental Science and Technology in May 2017 that fipronil and imidacloprid are among the pesticides threatening aquatic life in 38 rivers in the US, analysis of samples shows which were collected from November 2012 to June 2014.The researchers tested the samples for organic contaminants of human origin – specifically pesticides, antimicrobials, pharmaceuticals and breakdown products of these substances – and found 389.

“Invertebrates comprise most of the animal biomass in aquatic ecosystems and current results suggest significant potential for adverse effects from pollutants,” the article reads. “For example, the phenylpyrazole insecticide fipronil blocks the GABA-gated chloride channels of the insects’ central nervous system, resulting in decreased reproduction and decreased survival, and at least two fipronil breakdown products (sulfide, sulfone) are said to be more toxic than to sensitive aquatic invertebrates the trunk connection. “

Fipronil degradation, desulfinylfipronil, was the most commonly detected contaminant and occurred in 32 of 38 rivers. The researchers found at least two fipronil-related compounds in 19 sites and imidacloprid in 37%.

EPA officials are reviewing approved uses of fipronil under a program that re-evaluates all registered pesticides at least every 15 years, and in May 2020 EPA officials published a draft risk assessment showing the levels of fipronil and fipronil degradation in sewage treatment plants Wastewater was found, according to a statement by an EPA spokesman.

“If the EPA determines that exposure to pesticides poses urgent risks to humans or the environment that require immediate attention, the agency will take appropriate regulatory action regardless of the status of the pesticide’s registration review,” the statement said.

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