Down-the-drain pathways for fipronil and imidacloprid applied as spot-on parasiticides to dogs: Estimating aquatic pollution

Chemical profiling of surface water and biota in protected marine harbours impacted by combined sewer overflows

Few studies exist that focus on contaminants of emerging concern (CECs) in transitional and coastal waterbodies. This study presents chemical profiling of two protected marine harbours on the South coast of the UK sampled in 2022. Across 21 sites, 105 unique compounds were detected (0.05 ng L-1 --1798 ng L-1, median: 11 ng L-1) in water samples and biota, including 67 pharmaceuticals, 29 pesticides and nine recreational drugs. There were significant differences between campaigns with increased chemical numbers and concentrations that coincided with increased rainfall and combined sewer overflow (CSO) discharges. The comparison with CSO discharges revealed that they were an important source for loading of specific chemicals with concentrations increasing for some cases by three-orders of magnitude. High relative risks were estimated for sites sampled during recorded CSO discharges for five compounds with risk quotients (RQs) ranging from 1.1 up to 9.3, with the highest risk from the neonicotinoid, imidacloprid. To understand the exposure in biota, six species; one macroalgae (Fucus vesiculosus) and five fauna (Hediste diversicolor, Patella vulgate, Crassostrea gigas, Carcinus maenas, Echinogammarus marinus) were analysed (n = 5/species) at a CSO-impacted site. Between eight to 18 compounds were detected with Fucus vesiculosus (seaweed) showing the highest accumulation with mean cumulative burdens reaching up to 343 ± 71 ng g-1. Surface water contamination did not correlate with body burdens. Overall, the work highlights the complexity of the chemical space present in a transitional waterbody showing dynamic contamination patterns that are further influenced by tide, rainfall and salinity. CSOs demonstrated an important but compound specific role for CEC input and pulsing into receiving waters.

Swimming emissions from dogs treated with spot-on fipronil or imidacloprid: Assessing the environmental risk

BACKGROUND

Fipronil and imidacloprid are increasingly recognised as contaminants of concern in aquatic environments. This study aimed to quantify swimming emissions from dogs treated with spot-on fipronil or imidacloprid, assess the associated environmental risks and evaluate whether current label instructions on swimming restrictions are adequate.

METHODS

Emissions from swimming were measured for 49 dogs treated with spot-on fipronil or imidacloprid on days 5, 14 or 28 post-application. The environmental risk was assessed by calculating risk quotients, dividing the predicted environmental concentrations by the predicted no-effect concentrations for freshwater ecosystems.

RESULTS

Mean washoff ranged from 4% to 0.4% of the applied dose for fipronil and 10% to 1.4% for imidacloprid across the 5-28-day period. Risk quotients indicate a risk to aquatic ecosystems throughout the products' duration of action.

LIMITATIONS

The results may underestimate emissions for fipronil, as swimming is permitted from 3 days post-application and measurements began on day 5.

CONCLUSION

This study highlights clear ecological risks from spot-on parasiticides and provides evidence that current label instructions on swimming do not provide sufficient environmental protection. Risk-based parasite control strategies and extended swimming restrictions are recommended. Regulatory review of environmental risk assessments and mitigation measures is warranted to protect aquatic environments.

Antiparasitic Collars: Concentration Levels of Imidacloprid and Flumethrin in Dog Fur Suggest Low Toxicity Risks for Adult Humans

Seresto by Elanco (formerly Bayer Animal Health) is a collar for cats and dogs that provides long-lasting antiparasitic protection through the gradual release of imidacloprid and flumethrin onto the animal's skin. Although the EPA has deemed Seresto safe, their assessment is based on laboratory data, which may not fully reflect real-world exposure. Furthermore, recent reports of over 900 adverse human health events between 2012 and 2022 underscore the need for further safety investigations. We measured these chemicals' concentrations from the fur of eight dogs over 9 months to evaluate how daily interactions with pets could expose humans to toxic levels. Flumethrin was mostly undetectable, and imidacloprid levels were well below the toxicity threshold, suggesting low risks. However, factors like cumulative exposure and individual characteristics warrant consideration. Concentration levels were highest right after collar application, potentially reaching up to 11.6% of an 8 kg child's acceptable daily intake. We recommend limiting prolonged contact with pets, especially for young children, in the first 48 h post-application. We detected residual imidacloprid prior to collar application and 1 month after removal, raising questions as to the potential contamination risks that roaming pets could pose to ecosystems, given the known environmental impacts of these chemicals.

Characterizing pyrethroid and fipronil concentrations in biosolids

Pesticides are prevalent in wastewater, yet few studies have measured pesticides in biosolids and aqueous media from samples collected concurrently. Seventeen California wastewater treatment plants (WWTPs) were sampled in May 2020. Biosolids samples were analyzed for 27 analytes, and paired aqueous samples (influent and effluent) were analyzed for 23 analytes. Analytes included fipronil and its transformation products (fiproles), pyrethroids, novaluron, and several other pesticides with down-the-drain transport potential. Of the 27 compounds analyzed in biosolids samples, 16 were detected in at least one sample, and 10 had a detection frequency (DF) of at least 25 %. Fipronil sulfone, fipronil sulfide, and fipronil were the most frequently detected fiproles (DF = 100 %, 94 %, and 67 %, respectively); permethrin was the most frequently detected pyrethroid (DF = 100 %), followed by bifenthrin (DF = 94 %), cyhalothrin (DF = 89 %), and etofenprox (DF = 78 %). To elucidate fipronil transformation pathways within the treatment system, data from the three sample types were compared; findings were generally consistent with transformation pathways reported previously (e.g., some fiproles were rarely detected in influent or biosolids, but frequently detected in effluent, indicating their formation during the treatment process). No correlations were found between WWTP characteristics and pesticide concentrations in biosolids. The fraction of organic carbon (fOC) of each biosolids sample was measured, and a statistically significant negative correlation was observed between fOC and some fiproles, but not fipronil; possible explanations are discussed. Additional analysis for two major agricultural pesticides (bifenthrin and permethrin) indicated that estimated mass loads of these pesticides in biosolids applied to land as a soil amendment are minimal (approximately 2 to 3 orders of magnitude lower) compared to inputs from agricultural applications. This study provides insight on the magnitude of pesticides entering the environment via land-applied biosolids; existing regulations surrounding agricultural pesticide applications are expected to also be protective of the relatively low inputs from biosolids.

'The ecosystem impacts of pet parasite management must be addressed'

Peter Holdsworth and Maggie Fisher argue that although prophylactic use of parasiticides appears to support the One Health concepts of protecting animal and human health, this approach fails to consider the ecosystem health pillar.

Dog swimming and ectoparasiticide water contamination in urban conservation areas: A case study on Hampstead Heath, London

Widespread occurrence of two ectoparasiticide compounds in the aquatic environment, imidacloprid and fipronil, have prompted concerns about their potential environmental impacts. However, very little focus has been placed on water bodies in urban green spaces used for dog swimming. In this study, occurrence of both substances on Hampstead Heath, London, was compared in ponds with (n = 3) and without dog swimming activity (n = 3), as well as connecting streams above, between, and below these ponds (n = 6). Imidacloprid and fipronil were detected at main swimming points in dog swimming ponds at mean concentrations of 309 ± 104 ng/L and 32 ± 13 ng/L, respectively, indicating a high environmental risk in these samples. Measured concentrations in ponds not accessible for dog swimming were either below the limits of detection or limits of quantification for both chemicals. Across all ponds, there was a strong positive correlation between measured dog swimming activities and concentrations of imidacloprid (R2 = 0.91) and fipronil (R2 = 0.79). Some contamination was detected in connecting streams between ponds. A wider chemical analysis for the presence of urban waste water chemical residue signatures indicated minimal contamination, including in source waters. A survey of visitors who allow their dogs to swim in the sampled ponds confirmed frequent use of products containing imidacloprid and fipronil. In total, 86 % of 101 dog owners were unaware of the potential environmental impacts of products, and 94 % indicated that protecting nature would be an important consideration when selecting products. Besides the current practice of limiting dog access to ponds, information collected on product use and dog swimming practices identified additional opportunities to reduce contamination. We suggest that more cooperation between industry, regulators, veterinarians, green space managers, and the public can reduce risks to urban biodiversity while maintaining recreational benefits for dog owners and dogs.

Factors contributing to pesticide contamination in riverine systems: The role of wastewater and landscape sources

Wastewater treatment plant (WWTP) discharges can be a source of organic contaminants, including pesticides, to rivers. An integrated model was developed for the Potomac River watershed (PRW) to determine the amount of accumulated wastewater percentage of streamflow (ACCWW) and calculate predicted environmental concentrations (PECs) for 14 pesticides in non-tidal National Hydrography Dataset Plus Version 2.1 stream segments. Predicted environmental concentrations were compared to measured environmental concentrations (MECs) from 32 stream sites that represented a range of ACCWW and land use to evaluate model performance and to assess possible non-WWTP loading sources. Statistical agreement between PECs and MECs was strongest for insecticides, followed by fungicides and herbicides. Principal component analysis utilizing optical fluorescence and ancillary water quality data identified wastewater and urban runoff sources. Pesticides that indicated relatively larger sources from WWTPs included dinotefuran, fipronil, carbendazim, thiabendazole, and prometon whereas imidacloprid, azoxystrobin, propiconazole, tebuconazole, and diuron were more related to urban runoff. In addition, PECs generally comprised a low proportion of MECs, which indicates possible dominant loading sources beyond WWTP discharges. Cumulative potential toxicity was higher for sites with greater ACCWW and/or located in developed areas. Imidacloprid, fipronil, and carbendazim accounted for the largest portion of predicted potential toxicity across sites. The chronic aquatic life toxicity benchmarks for freshwater invertebrates were exceeded for 82 % of the imidacloprid detections (n = 28) and 47 % of the fipronil detections (n = 19). These results highlight the ecological implications of pesticide contamination from WWTP discharges and also the potential legacy effects from accumulated soil and groundwater sources. Pesticide management strategies that mitigate both current and historical impacts may improve the health of aquatic ecosystems.

Sustainable dairy farming and fipronil risk in circular feeds: insights from an Italian case study

Circular feeds, such as grain dry distillers, citrus pulp, cane molasses, and potatoes peels, are co-products of biomass processes. They are currently proposed in animal nutrition to improve the environmental and economic sustainability of the food production chain. In this paper, we report a case study involving fipronil, a pesticide currently not authorized for agriculture within the EU, but used in the Americas, Eastern Europe, and Asia. Fipronil was found at a mean level of 0.49 mg/kg, in a grain dry distiller batch administered to dairy cows. This finding, along with other evidence of potential fipronil presence in feed materials, prompted us to evaluate the risk to food safety and food security from 12 different conventional and sustainable feeding regimens. To this purpose, we considered a fipronil feed-to-milk carry-over rate of 0.52, the tolerance levels in fodders and food from The EU, Codex Alimentarius, and US-EPA, and the Acceptable Daily Intake (ADI) of 0.0002 mg/kg body weight for adverse effects on thyroid function in dairy cows. Under a conservative scenario, fipronil-contaminated potato peels and grain distillers in the feeding regimens may play a pivotal role in exceeding the EU Maximum Residue Level (MRL) in bovine milk and fat (0.005 and 0.030 mg/kg, respectively). Hay-based diets with soybean hulls and cane molasses show negligible risks (Hazard Index ∼ 1). In all cases, the ADI exceedance suggests the need to evaluate thyroid function in dairy cows exposed to fipronil as a food security factor.

Pilot study on neonicotinoids in Finnish waterbirds: no detectable concentrations in common goldeneye (Bucephala clangula) plasma

Neonicotinoids have been detected in farmland-associated birds and exposure to these insecticides has been linked to adverse effects. Even though neonicotinoids are mobile and persistent and have been detected in surface waters and aquatic invertebrates, there is a considerable lack of knowledge on their occurrence in waterbirds. Here we investigated the occurrence of seven neonicotinoids and some of their transformation products (imidacloprid, thiacloprid, thiamethoxam, acetamiprid, clothianidin, dinotefuran, nitenpyram, 6-chloronicotinic acid, hydroxy-imidacloprid, imidacloprid-urea, imidacloprid-olefin, thiamethoxam-urea, thiacloprid-amide, acetamiprid-acetate, and acetamiprid-desmethyl) in blood plasma of 51 incubating female common goldeneyes (Bucephala clangula). We collected samples from five different regions from southern to northern Finland encompassing rural and urban settings in coastal and inland areas. Surprisingly, none of the targeted neonicotinoids was found above the limit of detection in any of the samples. As neonicotinoid concentrations in wild birds can be very low, a likely reason for the nil results is that the LODs were too high; this and other possible reasons for the lack of detection of neonicotinoids in the goldeneyes are discussed. Our results suggest that neonicotinoid exposure in their breeding areas is currently not of major concern to female goldeneyes in Finland. Even though this study did not find any immediate danger of neonicotinoids to goldeneyes, further studies including surface water, aquatic invertebrates, and other bird species could elucidate potential indirect food chain effects.

Quantification and risk assessment of polar organic contaminants in two chalk streams in Hampshire, UK using the Chemcatcher passive sampler

Freshwater systems are facing a number of pressures due to the inputs of polar organic contaminants from a range of sources including agriculture, domestic and industry. The River Itchen and River Test are two sensitive chalk streams in Southern England that are experiencing a decline in invertebrate communities. We used Chemcatcher passive samplers to measure time-weighted average concentrations (14 days) of polar pollutants at nine sites on the River Itchen and eight sites on the River Test over a 12-month period. Sampler extracts were analysed using a targeted LC/MS method. In total, 121 plant protection products and pharmaceutical and personal care products were quantified (range of log Kow from - 1.5 to 7). Concentrations (sub ng L-1 to >500 ng L-1) in both rivers showed spatial and temporal variations. A greater number of compounds and higher concentrations were found in the River Test. The chemical profile was dominated by inputs from wastewater treatment plants and legacy plant protection products. On the River Itchen, high concentrations (∼100 ng L-1) of caffeine were observed directly downstream of a fish farm. Using the NORMAN database, the predicted no effect concentration (PNEC) freshwater values were exceeded by only five contaminants (2-hydroxy-terbuthylazine, alprazolam, azithromycin, diclofenac and imidacloprid). In addition, venlafaxine was detected above its EU Watch List concentration. These exceedances were mainly downstream of direct inputs from treatment plants. These compounds are known to have ecotoxicological effects on a range of aquatic biota including macroinvertebrates. Of concern is the ubiquitous presence of the ectoparasiticide imidacloprid, highlighting the need to control its use. The impact of the cocktail of pollutants found in this study on the long-term effects on chalk stream ecosystems remains unknown and needs further investigation.

Apportioning sources of chemicals of emerging concern along an urban river with inverse modelling

Concentrations of chemicals in river water provide crucial information for assessing environmental exposure and risks from fertilisers, pesticides, heavy metals, illicit drugs, pathogens, pharmaceuticals, plastics and perfluorinated substances, among others. However, using concentrations measured along waterways (e.g., from grab samples) to identify sources of contaminants and understand their fate is complicated by mixing of chemicals downstream from diverse diffuse and point sources (e.g., agricultural runoff, wastewater treatment plants). To address this challenge, a novel inverse modelling approach is presented. Using waterway network topology, it quantifies locations and concentrations of contaminant sources upstream by inverting concentrations measured in water samples. It is computationally efficient and quantifies uncertainty. The approach is demonstrated for 13 contaminants of emerging concern (CECs) in an urban stream, the R. Wandle (London, UK). Mixing (the forward problem) was assumed to be conservative, and the location of sources and their concentrations were treated as unknowns to be identified. Calculated CEC source concentrations, which ranged from below detection limit (a few ng/L) up to 1μg/L, were used to predict concentrations of chemicals downstream. Using this approach, >90% of data were predicted within observational uncertainty. Principal component analysis of calculated source concentrations revealed signatures of two distinct chemical sources. First, pharmaceuticals and insecticides were associated with a subcatchment containing a known point source of treated effluent from a wastewater treatment plant. Second, illicit drugs and salicylic acid were associated with multiple sources, interpreted as input from untreated sewage including Combined Sewer Overflows (CSOs), misconnections, runoff and direct disposal throughout the catchment. Finally, a simple algorithmic approach that incorporates network topology was developed to design sampling campaigns to improve resolution of source apportionment. Inverse modelling of contaminant measurements can provide objective means to apportion sources in waterways from spot samples in catchments on a large scale.