(Beyond Pesticides, August 23, 2023) The use of pesticides on pets for fleas and ticks (parasiticides) has been traced to environmental contamination in a study that confirms earlier work both by the authors and internationally, according to researchers Rosemary Perkins, a veterinary surgeon, and David Goulson, PhD at the University of Sussex. The results are published in their recent study, â€śTo flea or not to flea: survey of UK companion animal ectoparasiticide usage and activities affecting pathways to the environment,â€ť which concludes that, â€ś[T]he potential cumulative impact of parasiticide emissions [into the environment] from many millions of pets treated multiple times each year is of serious concern.â€ť
The UK provides an opportunity to pinpoint water contamination from pet use for ectoparasites (e.g., fleas and ticks) of hazardous pesticides since, unlike in the U.S., the country has banned outdoor use of those chemicals commonly detectedâ€”the insecticides fipronil and imidacloprid (the same neonicotinoid bug killer tied to devastating losses of bees and other organisms). These findings confirm the historical peer reviewed scientific literature and defy the assumption of regulators that home or veterinary use of pesticides do not reach levels of concern for environmental contamination, either through exposure from down-the-drain (DTD) contamination or direct environmental transfer.
As the authors point out:
â€śBoth fipronil and imidacloprid have been restricted for agricultural use in the UK due to concerns regarding their impact on non-target invertebrates. Fipronilâ€™s approval for use as a plant protection product ended in 2017 (European Commission, 2019a) and the outdoor use of imidacloprid was banned in 2018 (European Food Safety Authority, 2018a). At present no plant protection products containing fipronil or imidacloprid are registered for use in the UK (Health and Safety Executive, 2022).â€ťÂ
In 2016, a study of eight San Francisco Bay (San Francisco, CA, USA) wastewater treatment plants (WWTPs) reached a dramatic conclusion: â€śThis first regional study on fiprole and imidacloprid occurrences in raw and treated California sewage revealed ubiquity and marked persistence to conventional treatment of both phenylpyrazole and neonicotinoid compounds. Flea and tick control agents for pets are identified as potential sources of pesticides in sewage meriting further investigation and inclusion in chemical-specific risk assessments.â€ťÂ In 2020, a team of researchers, including Dr. Goulson, found widespread contamination of English waterways with imidacloprid and fipronil, which they attributed to veterinary use, given the fact, in part, that the chemicals had by that time been banned for outdoor uses in the UK.
In the study, the authors identify numerous environmental exposure routes from ectoparasiticide (to treat insects on the bodyâ€™s surface) pet use through: down the drain and waste water treatment plants, swimming and bathing after application, urine and stool after systemic absorption of the chemicals, washing of treated animalsâ€™ bedding and other contacted textiles, ownersâ€™ washing of hands, and shedding hair and skin. The data cited in the literature identifies significant environmental exposure that is overlooked or simply assumed to be low by regulators. As the authors note: â€śFurther studies are required to quantify the load entering the environment through various pathways for the different parasiticidesâ€”including studies providing reliable emissions fractions for the routes and activities described above, and studies investigating the frequency of emitting activities. This study aims to shed light on the frequency of activities that are likely to lead to transfer of ectoparasiticides from pets to the environment, with a focus on DTD and direct pathways to waterways, including bathing of dogs (Teerlink, Hernandez & Budd, 2017), washing of their bedding (Jacobs et al., 2001) and swimming (Diepens et al., 2023).â€ť
In the U.S., the cumulative environmental exposure pathway associated with pet use of pesticides raises issues of elevated exposure to aquatic system and adverse impact on the aquatic food web. As disclosed in the Beyond Pesticides piece Poisoned Waterways, alarms began to go off when the EPA found in its 2017 risk assessment for the most widely used neonicotinoid, imidacloprid, that, â€ś[C]oncentrations of imidacloprid detected in streams, rivers, lakes and drainage canals routinely exceed acute and chronic toxicity endpoints derived for freshwater invertebrates.â€ť (USEPA. 2017. Preliminary Aquatic Risk Assessment to Support the Registration Review of Imidacloprid. Office of Chemical Safety and Pollution Prevention. Washington DC.) The agency evaluated an expanded universe of adverse effects data and finds that acute (short-term) and chronic (long-term) toxicity endpoints are lower (adverse effects beginning at 0.65 Âµg/L (micrograms per liter)-acute and 0.01 Âµg/L-chronic effects) than previously established aquatic life benchmarks (adverse effects from 34.5 Âµg/L-acute and 1.05Âµg/L-chronic effects). In its 2017 risk assessment, EPA finds risks from imidacloprid exposure to ecologically important organisms not previously evaluated as part of its regulatory review. Despite its acknowledgement that current benchmarks are not adequately protective, EPA describes its review process as requiring studies of the most sensitive organisms and a range of publicly available environmental laboratory and field studies. The addition of the veterinary use exposure pathway raises serious concerns in an environment that is already at or beyond the threshold of concern for aquatic life.
The pet study sets up a framework for quantifying the pathways of contamination as a result of veterinary use of parasiticides. The study authors generated 1,009 complete questionnaire responses on ectoparasiticide use data, looking at both use of oral medications (more popular among dog owners) and spot-on treatments (more popular among cat owners). This followed a pilot survey of 155 respondents (sample size of 385 people/household) from June to July, 2020. Participants were recruited from social media, over 18 years old, and included a mix of cat and dog owners. Over 81% of pet owners report that they were advised by veterinarians to use prophylactic flea/tick treatment throughout the year. Over 7% were advised to only use the chemicals during the warmer months. The study documents frequency of bathing and swimming of treated pets, and bed washing. The authors estimate the volume of use of the pesticides, with 9.4 million doses of imidacloprid (the most popular ectoparasiticide), with over one-third treated pets swimming at least once a month and over half being bathed once a month.
The study is indicative of exposure pathways of ectoparasiticides that, if not considered in the regulatory review of these chemicals, are missed as critical issues of environmental impact by regulators.
For information on caring for pets without toxic chemical exposure, see Beyond Pesticidesâ€™ Pets and Pesticides: Keeping Our Campanions Safe webpage. And always check out Beyond Pesticidesâ€™ Gateway on Pesticides Hazards and Safe Pest Management when using specific pesticide products to find out the toxicological and environmental information on pesticides, as well as alternatives to their use.
You have an exciting and unique opportunity to meet Dr. Goulson live at Beyond Pesticides 40th National Forum, Forging a Future with Nature, September 14, 2023, 1:00-3:30pm(Eastern-US). You can register here.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.