Survey of bioaccessible pyrethroid insecticides and sediment toxicity in urban streams of the northeast United States

Relationship between stream size, watershed land use, and pesticide concentrations in headwater streams

A quantitative multiresidue study of current-use pesticides in multiple matrices was undertaken with field sampling at 32 headwater streams near Lac Saint-Pierre in Québec, Canada. A total of 232 samples were collected in five campaigns of stream waters and streambed sediments from streams varying in size and watershed land use. Novel multiresidue analytical methods from previous work were successfully applied for the extraction of pesticide residues from sediments via pressurized liquid extraction (PLE) and quantitative analysis using ultra high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) with online sample preparation on a hydrophilic-lipophilic balance (HLB) column. Of the 31 target compounds, including 29 pesticides and two degradation products of atrazine, 29 compounds were detected at least once. Consistent with other studies, atrazine and metolachlor were the most widely-detected herbicides. Detections were generally higher in water than sediment samples and the influence of land use on pesticide concentrations was only detectable in water samples. Small streams with a high proportion of agricultural land use in their watershed were generally found to have the highest pesticide concentrations. Corn and soybean monoculture crops, specifically, were found to cause the greatest impact on pesticide concentration in headwater streams and correlated strongly with many of the most frequently detected pesticides. This study highlights the importance of performing multiresidue pesticide monitoring programs in headwater streams in order to capture the impacts of agricultural intensification on freshwater ecosystems.

d-Tetramethrin causes zebrafish hepatotoxicity by inducing oxidative stress and inhibiting cell proliferation

d-Tetramethrin is one of the main components of mosquito control products, and is widely used for the control of dengue fever and insecticide production. Due to its widespread use, d-tetramethrin is a ubiquitous environmental pollutant and poses potential risks to human health. However, the effects of d-tetramethrin on liver morphology and function are not clearly established. In this study, we used zebrafish as an animal model to analyze the acute and chronic effects of d-tetramethrin exposure on the liver. We exposed zebrafish larvae and adults to different concentrations of d-tetramethrin and examined the impact of d-tetramethrin on lipid and glycogen metabolism, cellular properties, oxidative stress, cell proliferation, and apoptosis in the liver. We also analyzed transcriptional changes in genes related to apoptosis, inflammation, and cell proliferation using qPCR. Zebrafish exposed to d-tetramethrin exhibited severe liver damage, as evidenced by the presence of vacuoles and nuclear distortion in liver cells. The liver area in zebrafish larvae of the treatment group was significantly smaller than that of the control group. Significant lipid accumulation and decreased glycogen levels were observed in the livers of both zebrafish larvae and adults exposed to d-tetramethrin. Furthermore, d-tetramethrin exposure induced apoptosis and inflammation in zebrafish embryos. Additionally, d-tetramethrin caused liver damage, metabolic dysfunction, and impaired liver function. These results suggest that d-tetramethrin induces liver toxicity in zebrafish, by inducing oxidative stress and inhibiting cell proliferation.

Multiresidue method for the fast and efficient analysis of current-use pesticides in streambed sediments using pressurized liquid extraction

A multiresidue method for the fast and efficient analysis of current-use pesticides in streambed sediments is reported. The method employs pressurized liquid extraction (PLE) for the automated extraction of pesticide residues from small quantities (5 g) of lyophilized sediment samples. Various PLE parameters, including the extraction solutions and oven temperature, were optimized for thirty diverse current-use pesticides (CUPs) known to be commonly applied to corn and soybean monoculture crops. Following extraction, samples were analyzed with a fast and simplified quantitative multiresidue analytical method using ultra high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) with online solid phase extraction (SPE) on a hydrophilic-lipophilic balance (HLB) column. Validation of the method demonstrated acceptable recoveries (avg 41.4 %) comparable with other multiresidue methods for sediments, reliable intraday (<13 %) and interday (<24 %) repeatability, reasonable matrix effects (avg -54 %), and low LODs (avg 0.53 ng g-1 dw) and LOQs (avg 2.18 ng g-1 dw) given the complexity of the sediment matrix. The method was applied to 119 streambed sediment samples collected from agriculture-adjacent headwater streams near Lac Saint-Pierre in Québec, Canada to demonstrate the utility of the method. Fourteen of the thirty target analytes were detected within the samples, including nine herbicides, two insecticides, and three fungicides. To the best of our knowledge, an equally simple and efficient multiresidue method for the quantitative analysis of diverse CUPs in streambed sediments using PLE and UHPLC-MS/MS with online SPE has not yet been reported in the literature. This method helps to reduce labour and material inputs, avoids excessive sample manipulation, and allows for fast quantitative analysis of trace pesticide residues in streambed sediments, with the potential for application to other contaminants of emerging concern.

Distribution of pyrethroid insecticides in urban storm drain structures: Catch basins, open channels, and outfalls

Surface water runoff can transport contaminants offsite to downstream aquatic ecosystems. The prevalence of impervious surfaces in urban areas enhances surface runoff and contributes to contamination of urban surface streams. Urban areas have complex drainage systems for the conveyance of drainage water, however, there is a dearth of information on the distribution of contaminants within storm drain system structures. Pyrethroid insecticides are among the most used insecticides in urban areas, and trace levels of pyrethroids are known to exert toxicity to aquatic invertebrates. To investigate pyrethroid occurrence and distribution throughout an urban drainage system, samples of water, sediment, algae, and biofilm were collected from catch basins, open channels, and outfalls in Los Angeles County, California, during the dry season. From 3 catch basins, 7 open channels, and 7 outfalls, a total of 28 water samples, 4 sediment samples, 8 algae samples, and 4 biofilm samples were collected and analyzed. Pyrethroid concentrations above the reporting limit were detected in 89% of water samples and all sediment, algae, and biofilm samples, with bifenthrin and cyfluthrin being the most frequently detected compounds. The median total pyrethroid concentrations in water, sediments, algae, and biofilms were 27 ng/L, 88 ng/g, 356 ng/g, and 3556 ng/g, respectively. Bifenthrin concentrations in catch basins were found to be significantly higher than those in open channels or outfalls. Significant correlations were found for various metrics, including between pyrethroid partitioning in water samples and total suspended solids. These findings highlight the role of underground catch basins as a sink as well as a secondary source for contaminants such as pyrethroid insecticides. Prevention of the input of these urban originated contaminants to catch basins is crucial for protecting the water quality of urban surface waters.

Avoidance behavior of Hyalella azteca in response to three common-use insecticides

Non-target organisms in aquatic environments may experience lethal or sublethal effects following exposure to contaminants. Most protocols and regulations, however, are designed to provide protection from lethal effects and are thus based on conventional estimates of population lethality. The relative lack of reliable behavioral endpoints makes it challenging to implement regulations that are similarly protective against sublethal toxicity. The objective of this study was to quantify the avoidance behavior of Hyalella azteca when exposed to three insecticides-bifenthrin (B), chlorpyrifos (C), and permethrin (P)-at a range of estimated lethal concentrations. A two-choice behavioral arena was used for each chemical to quantify H. azteca activity and time spent in either uncontaminated sediment or sediment spiked at concentrations reflecting estimated 48-h lethal concentrations (LC50, LC25, and LC10). For all three insecticides, naïve H. azteca demonstrated a preference for the uncontaminated sediment over the contaminated sediment at the LC50 (B: 312 ng/gOC; C: 1265 ng/gOC; P: 5042 ng/gOC) and LC25 (B: 230 ng/gOC; C: 859 ng/gOC; P: 3817 ng/gOC), spending significantly more time in the uncontaminated side of the arena. H. azteca did not avoid sediment at LC10 (B: 204 ng/gOC; C: 609 ng/gOC; P: 1515 ng/gOC) levels, indicating the existence of a potential threshold of detection. Despite the lack of substrate preference at this exposure level, H. azteca were nevertheless more active (i.e., increased zone-switching) when exposed to bifenthrin at the LC10, suggesting a possible irritation response (e.g., movement after exposure) to this chemical. Our results provide evidence that H. azteca exhibit innate avoidance responses to sediments contaminated with common insecticides at concentrations below those represented by traditional toxicological endpoints (e.g., LC50). The sensitivity and ease with which this behavioral endpoint can be assayed demonstrates the potential utility of behavioral endpoints in toxicological assessments using model organisms.

Ecological risk assessment of pesticides in sediments of Pampean streams, Argentina

After their application in agricultural areas, pesticides are dispersed throughout the environment, causing contamination problems. In Argentina, the main promoter of transgenic biotechnology in the region, the total consumption of agrochemicals has increased significantly in recent years. Most chemicals dumped near surface waters eventually end up in bottom sediments and can be toxic to the organisms that live there. However, published data on the mixing of pesticides in this compartment is still scarce. The objective of this work was to detect and quantify pesticide residues in the sediment of rural streams in the Pampas region and to carry out acute and chronic risk assessment in these aquatic ecosystems. The study area comprises the mountainous system of Tandilia, located in one of the most productive agricultural areas in the country. The concentration of atrazine, acetochlor, chlorpyrifos, cypermethrin, and 2,4-D in the sediment of four rural streams was determined in three different seasons, and the toxic units (TU) and the risk ratios (RQ) were calculated. All the compounds analyzed were detected in most of the sampling seasons and study sites, at concentrations higher than those established in the national and international quality guidelines for the protection of aquatic biota in surface waters and for human consumption. Chlorpyrifos, cypermethrin, and acetochlor were the main pesticides contributing to the TU and RQ values, representing a medium or high ecological risk in most of the sites. Therefore, the evaluation of these pesticides in the bottom sediments could be a decisive factor in assessing the risk to the aquatic environment.

Predicting Resistance: Quantifying the Relationship between Urban Development, Agricultural Pesticide Use, and Pesticide Resistance in a Nontarget Amphipod

Resistance alleles within the voltage-gated sodium channel (vgsc) have been correlated with pyrethroid resistance in wild populations of the nontarget amphipod, Hyalella azteca from California (CA), U.S.A. In the present study, we expand upon the relationship between land use and the evolution of pesticide resistance in H. azteca to develop a quantitative methodology to target and screen novel populations for resistance allele genotypes in a previously uninvestigated region of the U.S. (New England: NE). By incorporating urban land development and toxicity-normalized agricultural pesticide use indices into our site selection, we successfully identified three amino acid substitutions associated with pyrethroid resistance. One of the resistance mutations has been described in H. azteca from CA (L925I). We present the remaining two (vgsc I936F and I936V) as novel pyrethroid-resistance alleles in H. azteca based on previous work in insects and elevated cyfluthrin resistance in one NE population. Our results suggest that urban pesticide use is a strong driver in the evolution of resistance alleles in H. azteca. Furthermore, our method for resistance allele screening provides an applied framework for detecting ecosystem impairment on a nationwide scale that can be incorporated into ecological risk assessment decisions.

Evaluation of silver nanoparticle acute and chronic effects on freshwater amphipod (Hyalella azteca)

Silver nanoparticles (AgNPs) are known to cause ecotoxic effects, but there are no existing derived ambient water quality criteria (AWQC) for these nanomaterials to protect freshwater aquatic life due to insufficient toxicological data. We exposed Hyalella azteca to silver nitrate, citrate-coated AgNPs (citrate-AgNPs), and polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs) in a 10-day and 28-day water-only static renewal system with clean sand as a substrate for the amphipods and compared their point estimates with the United States Environmental Protection Agency (USEPA) AWQC for silver. We observed that all treatments decreased the survival, growth, and biomass of H. azteca, and the order of toxicity was AgNO₃ > citrate-AgNPs > PVP-AgNPs. The LC50s of AgNO₃, citrate-AgNPs, and PVP-AgNPs were 3.0, 9.6, and 296.0 µg total Ag L^-1, respectively, for the acute exposure and 2.4, 3.2, and 61.4 µg total Ag L^-1, respectively, for the chronic exposure. Acute and chronic EC20s of citrate-AgNPs ranged from 0.5 to 3.5 µg total Ag L^-1 while that of PVP-AgNPs ranged from 31.2 to 175 µg total Ag L^-1 for growth and biomass. Both Ag⁺ released from AgNPs and the nanoparticles contributed to the observed toxicity. The dissolution and toxicity of AgNPs were influenced by surface coating agents, particle size, and surface charge. Most point estimates for AgNPs were above AWQC for silver (4.1 µg L^-1) and the lowest concentration (0.12 µg/L) at which Ag is expected to cause chronic adverse effects to freshwater aquatic life. Our study demonstrates that the current AWQC for silver, in general, is protective of freshwater aquatic life against AgNPs tested in the present study.

Bioavailability for organic chemical bioaccumulation follows the power law

Despite the importance of bioavailability for organic chemical bioaccumulation by terrestrial and benthic invertebrates, the principles of bioavailability for organic chemical bioaccumulation remain poorly understood. Here we use large-scale databases with contrasting geographic, compound and organism coverage (from 925 sites, 446 compounds and 184 invertebrate species), and report that bioavailability for organic chemical bioaccumulation follows the power law. It represents that the internal concentration of organic chemicals is the composite power function of the lipid fraction of invertebrates, bulk site concentration of compounds, and organic carbon content of soils/sediments. This law directly links environmental exposures and body burdens of organic chemicals in contaminated sites, and provides a method for enabling case-specific risk assessments of a vast number of organic chemicals and contaminated sites. Our findings may pave the way for translating bioavailability knowledge into risk-oriented regulation of organic chemicals and contaminated sites.

Toxicity and remediation of pharmaceuticals and pesticides using metal oxides and carbon nanomaterials

The worldwide development of agriculture and industry has resulted in contamination of water bodies by pharmaceuticals, pesticides and other xenobiotics. Even at trace levels of few micrograms per liter in waters, these contaminants induce public health and environmental issues, thus calling for efficient removal methods such as adsorption. Recent adsorption techniques for wastewater treatment involve metal oxide compounds, e.g. Fe2O3, ZnO, Al2O3 and ZnO-MgO, and carbon-based materials such as graphene oxide, activated carbon, carbon nanotubes, and carbon/graphene quantum dots. Here, the small size of metal oxides and the presence various functional groups has allowed higher adsorption efficiencies. Moreover, carbon-based adsorbents exhibit unique properties such as high surface area, high porosity, easy functionalization, low price, and high surface reactivity. Here we review the cytotoxic effects of pharmaceutical drugs and pesticides in terms of human risk and ecotoxicology. We also present remediation techniques involving adsorption on metal oxides and carbon-based materials.

Pyrethroid bioaccumulation in field-collected insecticide-resistant Hyalella azteca

Wild-type Hyalella azteca are highly sensitive to pyrethroid insecticides and typically do not survive exposure; however, pyrethroid bioaccumulation by insecticide-resistant H. azteca is an important potential risk factor for the transfer of pyrethroids to higher trophic species in aquatic systems. In the current study, four populations of pyrethroid-resistant H. azteca with corresponding sediment samples were sampled throughout the year, and nine-current use pyrethroids (tefluthrin, fenpropathrin, bifenthrin, cyhalothrin, permethrin, cyfluthrin, cypermethrin, esfenvalerate and deltamethrin) were measured. Bifenthrin was detected in every pyrethroid-resistant H. azteca tissue sample, up to 813 ng/g lipid, while cyhalothrin and permethrin were detected in fewer (18 and 28%, respectively) samples. Concurrent sampling of the sediment showed total pyrethroid concentrations exceeding toxic unit thresholds for non-resistant H. azteca survival, and confirmed the ubiquitous presence of bifenthrin at each site and sampling event. Bifenthrin concentrations in H. azteca tended to be higher in samples collected in winter months, and seasonal factors, such as temperature and rainfall, may have contributed to the noted differences in bioaccumulation. Finally, the bifenthrin and permethrin biota-sediment accumulation factors (BSAF) for pyrethroid-resistant H. azteca were similar to the BSAF values for less sensitive invertebrates, and therefore the development of resistance may enable an additional pathway for trophic transfer of pyrethroids in species that would otherwise be too sensitive to survive the exposure.

Utility of normalizing Tenax extractable concentrations for phase volume in application as an environmental screening tool

Bioaccessibility-based extraction tools, such as single-point Tenax extractions (SPTEs), provide cost-effective and accurate estimates of bioaccumulation and toxicity of hydrophobic organic contaminants during environmental sampling. Use of SPTEs as a screening tool in risk assessment is hindered by the requirement for normalization of extractable concentrations for organic carbon (OC). Normalizing SPTE concentrations for the volume of Tenax used during the extraction could improve the applicability of this methodology by removing the system dependence when applying SPTE concentrations to estimates of bioaccumulation. The objective of this study was to examine the utility of Tenax phase volume normalization in place of OC normalization when using SPTEs to estimate bioaccumulation. No significant differences were observed between the slope of regression lines generated between SPTE concentrations normalized for either Tenax phase volume or OC (p = 0.410), but slight improvement of the regression was noted when using phase volume normalization (R² = 0.829) compared to OC normalization (R² = 0.740). Replacing OC normalization with phase volume normalization in use of SPTEs more accurately represents the partition of the chemical to the Tenax during the SPTE, improves estimates of bioaccumulation, and expands the use of SPTEs as a rapid assessment tool for determining bioaccumulation during screening of contaminated environments.

How Plants Synthesize Pyrethrins: Safe and Biodegradable Insecticides

Natural pyrethrin insecticides produced by Dalmatian pyrethrum (Tanacetum cinerariifolium) have low mammalian toxicity and short environmental persistence, providing an alternative to widely used synthetic agricultural insecticides that pose a threat to human health and the environment. A recent surge of interest in the use of pyrethrins as agricultural insecticides coincides with the discovery of several new genes in the pyrethrin biosynthetic pathway. Elucidation of this pathway facilitates efforts to breed improved pyrethrum varieties and to engineer plants with improved endogenous defenses or hosts for heterologous pyrethrin production. We describe the current state of knowledge related to global pyrethrum production, the pyrethrin biosynthetic pathway and its regulation, and recent efforts to engineer the pyrethrin pathway in diverse plant hosts.

Recessivity of pyrethroid resistance and limited interspecies hybridization across Hyalella clades supports rapid and independent origins of resistance

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.

Cytotoxic aquatic pollutants and their removal by nanocomposite-based sorbents

Water is an extremely essential compound for human life and, hence, accessing drinking water is very important all over the world. Nowadays, due to the urbanization and industrialization, several noxious pollutants are discharged into water. Water pollution by various cytotoxic contaminants, e.g. heavy metal ions, drugs, pesticides, dyes, residues a drastic public health issue for human beings; hence, this topic has been receiving much attention for the specific approaches and technologies to remove hazardous contaminants from water and wastewater. In the current review, the cytotoxicity of different sorts of aquatic pollutants for mammalian is presented. In addition, we will overview the recent advances in various nanocomposite-based adsorbents and different approaches of pollutants removal from water/wastewater with several examples to provide a backdrop for future research.

Sediment toxicity of the fungicide fludioxonil to benthic macroinvertebrates -evaluation of the tiered effect assessment procedure

28-Day sediment-spiked laboratory toxicity tests with eight benthic macroinvertebrates and the lipophilic fungicide fludioxonil were conducted to verify the proposed tiered sediment effect assessment procedure as recommended by the European Food Safety Authority (EFSA). The test species were the oligochaetes Lumbriculus variegatus and Tubifex tubifex, the insects Chironomus riparius and Caenis horaria, the crustaceans Hyalella azteca and Asellus aquaticus and the bivalves Corbicula fluminalis and Pisidium amnicum. Toxicity estimates were expressed in terms of total concentration of dry sediment as well as in pore water concentration. Field-collected sediment, also used in a previously performed sediment-spiked microcosm experiment, was used in tests with all species. L. variegatus and C. riparius had similar lowest 28d-L(E)C₁₀ values when expressed in terms of total sediment concentration, but in terms of pore water concentration L. variegatus was more sensitive. Three of the six additional benthic test species (A. aquaticus, C. horaria, C. fluminalis) had 28d-EC₁₀ values a factor of 2-6 lower than that of L. variegatus. Comparing different effect assessment tiers for sediment organisms, i.e. Tier-0 (Modified Equilibrium Partitioning approach), Tier-1 (Standard Test Species approach), Tier-2 (Species Sensitivity Distribution (SSD) approach) and Tier-3 (Model Ecosystem approach), it is concluded that the tiers based on sediment-spiked laboratory toxicity tests provide sufficient protection when compared with the Tier-3 Regulatory Acceptable Concentration (RAC). Differences between Tier-1 and Tier-2 RACs, however, appear to be relatively small and not always consistent, irrespective of expressing the RAC in terms of total sediment or pore water concentration. Derivation of RACs by means of the SSD approach may be a challenge, because it is difficult obtaining a sufficient number of valid chronic EC₁₀ values with appropriate 95% confidence bands for sediment-dwelling macroinvertebrates. Therefore, this paper proposes a Tier-2 Weight-of-Evidence approach to be used in case an insufficient number of valid additional toxicity data is made available. Similar studies with pesticides that differ in fate properties and toxic mode-of-action are necessary for further validation of the tiered effect assessment approach for sediment organisms.

Biofilms Provide New Insight into Pesticide Occurrence in Streams and Links to Aquatic Ecological Communities

Streambed sediment is commonly analyzed to assess occurrence of hydrophobic pesticides and risks to aquatic communities. However, stream biofilms also have the potential to accumulate pesticides and may be consumed by aquatic organisms. To better characterize risks to aquatic life, the U.S. Geological Survey Regional Stream Quality Assessment measured 93 current-use and 3 legacy pesticides in bed sediment and biofilm from 54 small streams in California across a range of land-use settings. On average, 4 times as many current-use pesticides were detected in biofilm at a site (median of 2) as in sediment (median of 0.5). Of 31 current-use pesticides detected, 20 were detected more frequently in biofilm than in sediment and 10 with equal frequency. Pyrethroids as a class were the most potentially toxic to benthic invertebrates, and of the 9 pyrethroids detected, 7 occurred more frequently in biofilm than sediment. We constructed general additive models to investigate relations between pesticides and 6 metrics of benthic community structure. Pesticides in biofilm improved fit in 4 of the 6 models, and pesticides in sediment improved fit in 2. The results indicate that the sampling of stream biofilms can complement bed-sediment sampling by identification of more current-use pesticides present and better estimation of ecological risks.