•Current knowledge on pyrethroids in sediment is reviewed on a global scale.•Toxicity of sediment-associated pyrethroids to benthic invertebrates is evaluated.•Potential risk of pyrethroids to ...benthic community is simulated based on SQC.•Sediment-bound pyrethroids exhibited potential risk to benthic organisms globally.•Factors influencing sediment risk assessment of pyrethroids is discussed.
Pyrethroids are the third most applied group of insecticides worldwide and are extensively used in agricultural and non-agricultural applications. Pyrethroids exhibit low toxicity to mammals, but have extremely high toxicity to fish and non-target invertebrates. Their high hydrophobicity, along with pseudo-persistence due to continuous input, indicates that pyrethroids will accumulate in sediment, pose long-term exposure concerns to benthic invertebrates and ultimately cause significant risk to benthic communities and aquatic ecosystems. The current review synthesizes the reported sediment concentrations of pyrethroids and associated toxicity to benthic invertebrates on a global scale. Geographically, the most studied area was North America, followed by Asia, Europe, Australia and Africa. Pyrethroids were frequently detected in both agricultural and urban sediments, and bifenthrin and cypermethrin were identified as the main contributors to toxicity in benthic invertebrates. Simulated hazard quotients (HQ) for sediment-associated pyrethroids to benthic organisms ranged from 10.5±31.1 (bifenthrin) to 41.7±204 (cypermethrin), suggesting significant risk. The current study has provided evidence that pyrethroids are not only commonly detected in the aquatic environment, but also can cause toxic effects to benthic invertebrates, and calls for better development of accurate sediment quality criteria and effective ecological risk assessment methods for this emerging class of insecticides.
Fipronil is a phenylpyrazole insecticide with increasing urban use. Sixteen urban waterways and municipal wastewater were sampled for fipronil, its environmental degradates, and pyrethroid ...insecticides. Because findings could not be interpreted with existing data on fipronil degradate toxicity, EC50s and LC50s for fipronil and its sulfide and sulfone derivatives were determined for 14 macroinvertebrate species. Four species were more sensitive than any previously studied, indicating fipronil's toxicity to aquatic life has long been underestimated. The most sensitive species tested, Chironomus dilutus, had a mean 96-h EC50 of 32.5 ng/L for fipronil and 7–10 ng/L for its degradates. Hyalella azteca, a common testing species, was among the least sensitive. The typical northern California creek receiving urban stormwater runoff contains fipronil and degradate concentrations twice the EC50 of C. dilutus, and approximately one-third the EC50 for a stonefly, a caddisfly, and two mayfly species. The present study substantially increases data available on toxicity of fipronil degradates, and demonstrates that fipronil and degradates are common in urban waterways at concentrations posing a risk to a wide variety of stream invertebrates.
Tenax extraction, a measure of chemical desorption rates from sediments, was used to evaluate the bioaccessibility of bifenthrin in two different sediments exposed to three temperatures aged over a ...56-d holding period. A 24-h single-point Tenax extraction was used and parent
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C-bifenthrin and polar metabolites were quantified in the sediment and Tenax. Bioaccessibility of bifenthrin was inversely related to the organic carbon (OC) content in the sediment, holding time, and temperature. Sequestration of the bifenthrin into slowly desorbing fractions within the sediment appears to have decreased degradation of the parent compound into metabolites and decreased the amount of parent compound bioaccessible for uptake by the Tenax. These results suggest that the environmental risk of bifenthrin to aquatic species is greatest immediately after the pesticide enters a waterbody after runoff, for low-OC content sediments, and in areas or seasons where water temperatures are colder.
Commercial mosquito repellents (MRs) are generally applied as mosquito coils, electric vaporizers (liquid and solid) or aerosol spray, with pyrethroids often being the active ingredients. Four types ...of MRs were applied individually in a 13-m2 bedroom to study the occurrence, dissipation and risk of pyrethroids in indoor environments. Total air concentrations (in gas and particle phases) of allethrin, cypermethrin, dimefluthrin and tetramethrin during MR applications were three to six orders of magnitude higher than indoor levels before the applications, and allethrin emitted from a vaporizing mat reached the highest concentration measured during the current study (18,600 ± 4980 ng m−3). The fate of airborne pyrethroids was different when the four MRs were applied. Particle-associated allethrin accounted for 95% of its total concentration from the aerosol spray, and was significantly higher than the vaporizing mat (67%), suggesting that the released phase of MRs and size distribution of pyrethroid-carrying particles played important roles in the gas-particle partitioning process. In addition, air exchange through open windows more effectively reduced the levels of indoor pyrethroids than ventilation using an air conditioner. The inhalation risk quotients (RQ) for allethrin derived from application of the vaporizing mat ranged from 1.04 ± 0.40 to 1.98 ± 0.75 for different age-subgroups of the population, suggesting potential exposure risk. Special attention should be given concerning indoor exposure of pyrethroids to these vulnerable groups.
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•The types of mosquito repellents (MRs) affected indoor exposure to pyrethroids.•Pyrethroid levels increased 3–6 orders of magnitude after indoor MR application.•The gas-particle partitioning and dissipation of pyrethroids varied among MRs.•Vaporizing mat-emitted allethrin posed significant risk to children (<6 years old).
Concentrations of pyrethroids during mosquito repellent applications in indoor air were up to six orders of magnitude higher than outdoor concentrations, which posed risk to children.
Use of pesticides can have substantial nonlethal impacts on nontarget species, including driving evolutionary change, often with unknown consequences for species, ecosystems, and society. Hyalella ...azteca , a species complex of North American freshwater amphipods, is widely used for toxicity testing of water and sediment and has frequently shown toxicity due to pyrethroid pesticides. We demonstrate that 10 populations, 3 from laboratory cultures and 7 from California water bodies, differed by at least 550-fold in sensitivity to pyrethroids. The populations sorted into four phylogenetic groups consistent with species-level divergence. By sequencing the primary pyrethroid target site, the voltage-gated sodium channel, we show that point mutations and their spread in natural populations were responsible for differences in pyrethroid sensitivity. At least one population had both mutant and WT alleles, suggesting ongoing evolution of resistance. Although nonresistant H. azteca were susceptible to the typical neurotoxic effects of pyrethroids, gene expression analysis suggests the mode of action in resistant H. azteca was not neurotoxicity but was oxidative stress sustained only at considerably higher pyrethroid concentrations. The finding that a nontarget aquatic species has acquired resistance to pesticides used only on terrestrial pests is troubling evidence of the impact of chronic pesticide transport from land-based applications into aquatic systems. Our findings have far-reaching implications for continued uncritical use of H. azteca as a principal species for monitoring and environmental policy decisions.
While studies have documented the presence of pyrethroid insecticides at acutely toxic concentrations in sediments, little quantitative data on sources exist. Urban runoff, municipal wastewater ...treatment plants and agricultural drains in California’s Sacramento-San Joaquin River Delta were sampled to understand their importance as contributors of these pesticides to surface waters. Nearly all residential runoff samples were toxic to the amphipod, Hyalella azteca, and contained pyrethroids at concentrations exceeding acutely toxic thresholds, in many cases by 10-fold. Toxicity identification evaluation data were consistent with pyrethroids, particularly bifenthrin and cyfluthrin, as the cause of toxicity. Pyrethroids passed through secondary treatment systems at municipal wastewater treatment facilities and were commonly found in the final effluent, usually near H. azteca 96-h EC50 thresholds. Agricultural discharges in the study area only occasionally contained pyrethroids and were also occasional sources of toxicity related to the organophosphate insecticide chlorpyrifos. Discharge of the pyrethroid bifenthrin via urban stormwater runoff was sufficient to cause water column toxicity in two urban creeks, over at least a 30 km reach of the American River, and at one site in the San Joaquin River, though not in the Sacramento River.
Suisun Marsh, in northern San Francisco Bay, is the largest brackish marsh in California, and provides critical habitat for many fish species. Storm runoff enters the marsh through many creeks that ...drain agricultural uplands and the urban areas of Fairfield and Suisun City. Five creeks were sampled throughout a major storm event in February 2014, and analyzed for representatives of several major insecticide classes. Concentrations were greatest in creeks with urban influence, though sampling was done outside of the primary season for agricultural pesticide use. Urban creek waters reached maximum concentrations of 9.9ng/l bifenthrin, 27.4ng/l fipronil, 11.9ng/l fipronil sulfone, 1462ng/l imidacloprid, and 4.0ng/l chlorpyrifos. Water samples were tested for toxicity to Hyalella azteca and Chironomus dilutus, and while few samples caused mortality, 70% of the urban creek samples caused paralysis of either or both species. Toxic unit analysis indicated that bifenthrin was likely responsible for effects to H. azteca, and fipronil and its sulfone degradate were responsible for effects to C. dilutus. These results demonstrate the potential for co-occurrence of multiple insecticides in urban runoff, each with the potential for toxicity to particular species, and the value of toxicity monitoring using multiple species. In the channels of Suisun Marsh farther downstream, insecticide concentrations and toxicity diminished as creek waters mixed with brackish waters entering from San Francisco Bay. Only fipronil and its degradates remained measurable at 1–10ng/l. These concentrations are not known to present a risk based on existing data, but toxicity data for estuarine and marine invertebrates, particularly for fipronil's degradates, are extremely limited.
•Suisun Marsh, in California, provides habitat to several imperiled fish species.•Pesticides were sampled in creek waters flowing to the marsh after a winter storm.•Urban creeks were toxic to invertebrates due to bifenthrin and fipronil.•No toxicity was seen in agriculture-affected creeks, at least during the winter.•Fipronil was measurable in the marsh, but not toxic due in part to dilution.
Toxicity tests were performed with seven fluoroquinolone antibiotics, ciprofloxacin, lomefloxacin, ofloxacin, levofloxacin, clinafloxacin, enrofloxacin, and flumequine, on five aquatic organisms. ...Overall toxicity values ranged from 7.9 to 23,000 μg/L. The cyanobacterium Microcystis aeruginosa was the most sensitive organism (5‐d growth and reproduction, effective concentrations EC50s ranging from 7.9 to 1,960 μg/L and a median of 49 μg/L), followed by duckweed (Lemna minor, 7‐d reproduction, EC50 values ranged from 53 to 2,470 μg/L with a median of 106 μg/L) and the green alga Pseudokirchneriella subcapitata (3‐d growth and reproduction, EC50 values ranged from 1,100 to 22,700 μg/L with a median 7,400 μg/L). Results from tests with the crustacean Daphnia magna (48‐h survival) and fathead minnow (Pimephales promelas, 7‐d early life stage survival and growth) showed limited toxicity with no‐observed‐effect concentrations at or near 10 mg/L. Fish dry weights obtained in the ciprofloxacin, levofloxacin, and ofloxacin treatments (10 mg/L) were significantly higher than in control fish. The hazard of adverse effects occurring to the tested organisms in the environment was quantified by using hazard quotients. An estimated environmental concentration of 1 μg/L was chosen based on measured environmental concentrations previously reported in surface water; at this level, only M. aeruginosa may be at risk in surface water. However, the selective toxicity of these compounds may have implications for aquatic community structure.
Toxicity identification evaluation (TIE) methods can be used to identify toxic compounds in environmental samples using a variety of laboratory techniques. Whereas TIEs exist for nonpolar organics, ...relatively few methods are established for individual contaminant classes. Toxicity identification evaluations have shown pesticides to be the cause of toxicity in agricultural waters and effluents, and more recent studies have shown that the insecticide class of concern is pyrethroids. The primary objectives of the present study were to confirm a temperature TIE model and mechanistically explain these trends. This was achieved by comparing the relative toxicity and influence of temperature (13 vs 23°C) on Chironomus dilutus exposed to four insecticides, including two pyrethroids, an organophosphate, and an organochlorine, and then explaining these changes using toxicokinetics. A 10°C temperature decrease increased the toxicity of pyrethroids and DDT but decreased the toxicity of chlorpyrifos. The decrease in chlorpyrifos toxicity was driven primarily by the reduction of the formation of more toxic products via decreased biotransformation. The increase in DDT toxicity, in contrast, can be attributed to increased nerve sensitivity at 13 versus 23°C. The pyrethroid toxicity change, however, resulted from a combination of increased accumulation of parent compound and increased nerve sensitivity, exacerbating the toxicity of pyrethroids at 13°C. These trends also held true in sediment exposures with chlorpyrifos and permethrin, indicating that water‐only exposures were adequate substitutes for examining this mechanism.
Several populations of the amphipod, Hyalella azteca, have developed resistance to pyrethroid insecticides due to non-target exposure, but the dominance of the resistance trait is unknown. The ...current study investigated the dominance level of point mutations in natural populations of insecticide-resistant H. azteca and determined whether H. azteca from different clades with and without resistant alleles can hybridize and produce viable offspring. A parent generation (P0) of non-resistant homozygous wild type H. azteca was crossbred with pyrethroid-resistant homozygous mutant animals and the tolerance of the filial 1 (F1) generation to the pyrethroid insecticide, permethrin, was measured. Then the genotypes of the F1 generation was examined to assure heterozygosity. The resistant parents had permethrin LC50 values that ranged from 52 to 82 times higher than the non-resistant animals and both crossbreeding experiments produced heterozygous hybrid offspring that had LC50 values similar to the non-resistant H. azteca parent. Dominance levels calculated for each of the crosses showed values close to 0, confirming that the L925I and L925V mutations were completely recessive. The lack of reproduction by hybrids of the C x D breeding confirmed that these clades are reproductively isolated and therefore introgression of adaptive alleles across these clades is unlikely. Potential evolutionary consequences of this selection include development of population bottlenecks, which may arise leading to fitness costs and reduced genetic diversity of H. azteca.
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•Crossbreeding pyrethroid-resistant and non-resistant Hyalella azteca was studied.•Use of Po and F1 permethrin acute toxicity tests showed completely recessive mutation.•Breeding between different clades did not produce viable offspring.•Resistance was retained in pyrethroid-free culturing for at least five generations.•Pyrethroid resistance make H. azteca more vulnerable to population-level stressors.
Capsule: This study investigated the dominance level of point mutations in natural populations of insecticide-resistant H. azteca and determined whether H. azteca from different clades with and without resistant alleles can hybridize and produce viable offspring.
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