Examining impacts of current-use pesticides in Southern Ontario using in situ exposures of the amphipod Hyalella azteca

Laboratory and In situ Selenium Bioaccumulation Assessment in the Benthic Macroinvertebrates Hyalella azteca and Chironomus dilutus

Selenium (Se) bioaccumulation and toxicity in aquatic vertebrates have been thoroughly investigated. Limited information is available on Se bioaccumulation at the base of aquatic food webs. In this study, we evaluated Se bioaccumulation in two benthic macroinvertebrates (BMI), Hyalella azteca and Chironomus dilutus raised in the laboratory and caged in-situ to a Canadian boreal lake e (i.e., McClean Lake) that receives continuous low-level inputs of Se (< 1 μg/L) from a uranium mill. Additional Se bioaccumulation assays were conducted in the laboratory with these BMI to (i) confirm field results, (ii) compare Se bioaccumulation in lab-read and native H. azteca populations and (iii) identify the major Se exposure pathway (surface water, top 1 cm and top 2-3 cm sediment layers) leading to Se bioaccumulation in H. azteca. Field and laboratory studies indicated overall comparable Se bioaccumulation and trophic transfer factors (TTFs) in co-exposed H. azteca (whole-body Se 0.9-3.1 µg/g d.w; TTFs 0.6-6.3) and C. dilutus (whole-body Se at 0.7-3.2 µg Se/g d.w.; TTFs 0.7-3.4). Native and lab-reared H. azteca populations exposed to sediment and periphyton from McClean Lake exhibited similar Se uptake and bioaccumulation (NLR, p = 0.003; 4.1 ± 0.8 µg Se/g d.w), demonstrating that lab-reared organisms are good surrogates to assess on-site Se bioaccumulation potential. The greater Se concentrations in H. azteca exposed to the top 1-3 cm sediment layer relative to waterborne exposure, corroborates the importance of the sediment-detrital pathway leading to greater Se bioaccumulation potential to higher trophic levels via BMI.

Microparticles in Wild and Caged Biota, Sediments, and Water Relative to Large Municipal Wastewater Treatment Plant Discharges

Anthropogenically modified microparticles including microplastics are present in municipal wastewater treatment plant (WWTP) effluents; however, it is unclear whether biotic exposures are elevated downstream of these outfalls. In the fall of 2019, the present study examined whether microparticle levels in resident fish, environmental samples, and caged organisms were elevated near the Waterloo and Kitchener WWTP outfalls along the Grand River, Ontario, Canada. Wild rainbow darters (Etheostoma caeruleum) were collected from a total of 10 sites upstream and downstream of both WWTPs, along with surface water and sediment samples to assess spatial patterns over an approximately 70-km river stretch. Amphipods (Hyalella azteca), fluted-shell mussels (Lasmigona costata), and rainbow trout (Oncorhynchus mykiss) were also caged upstream and downstream of one WWTP for 14 or 28 days. Whole amphipods, fish digestive tracts, and mussel tissues (hemolymph, digestive glands, gills) were digested with potassium hydroxide, whereas environmental samples were processed using filtration and density separation. Visual identification, measurement, and chemical confirmation (subset only) of microparticles were completed. Elevated abiotic microparticles were found at several upstream reference sites as well as at one or both wastewater-impacted sites. Microparticles in amphipods, all mussel tissues, and wild fish did not show patterns indicative of increased exposures downstream of effluent discharges. In contrast, elevated microparticle counts were found in trout caged directly downstream of the outfall. Across all samples, cellulose fibers (mainly blue and clear colors) were the most common. Overall, results suggest little influence of WWTP effluents on microparticles in biota but rather a ubiquitous presence across most sites that indicates the importance of other point and nonpoint sources to this system. Environ Toxicol Chem 2024;00:1-15. © 2024 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Toxicity of fipronil and 2,4-D formulations (alone and in a mixture) to the tropical amphipod Hyalella meinerti

Conventional farming uses a large volume of pesticides that may reach aquatic ecosystems. This is also the case for the insecticide fipronil and the herbicide 2,4-D, which are widely used in many crops. This study aimed at evaluating the individual and mixture toxicity of these pesticides to the tropical amphipod Hyalella meinerti. To this end, acute toxicity tests (96 h) were conducted. Chronic bioassays (10 days) were also carried out, in which the body length and dry biomass were evaluated as endpoints. In addition, a complete factorial mixture chronic toxicity test was carried out. H. meinerti was sensitive to fipronil in the acute toxicity tests, with a LC₅₀-96-h of 0.86 μg L^-1 (95% CI 0.26-0.46), and no acute effects were observed after 2,4-D exposure even at the highest test concentration of 100 mg L^-1. In the chronic toxicity tests, all tested concentrations of both pesticides decreased the growth of H. meinerti, in which losses on biomass reached 45% and 65% for 2,4-D and fipronil, respectively. The pesticide mixture indicated antagonism although it still significantly decreased the body growth. The results obtained indicate a high sensitivity of H. meinerti exposed to environmentally realistic concentrations, demonstrating that there are risks for the species in real field conditions.

Prioritization of Pesticides for Assessment of Risk to Aquatic Ecosystems in Canada and Identification of Knowledge Gaps

Pesticides can enter aquatic environments via direct application, via overspray or drift during application, or by runoff or leaching from fields during rain events, where they can have unintended effects on non-target aquatic biota. As such, Fisheries and Oceans Canada identified a need to prioritize current-use pesticides based on potential risks towards fish, their prey species, and habitats in Canada. A literature review was conducted to: (1) Identify current-use pesticides of concern for Canadian marine and freshwater environments based on use and environmental presence in Canada, (2) Outline current knowledge on the biological effects of the pesticides of concern, and (3) Identify general data gaps specific to biological effects of pesticides on aquatic species. Prioritization was based upon recent sales data, measured concentrations in Canadian aquatic environments between 2000 and 2020, and inherent toxicity as represented by aquatic guideline values. Prioritization identified 55 pesticides for further research nationally. Based on rank, a sub-group of seven were chosen as the top-priority pesticides, including three herbicides (atrazine, diquat, and S-metolachlor), three insecticides (chlorpyrifos, clothianidin, and permethrin), and one fungicide (chlorothalonil). A number of knowledge gaps became apparent through this process, including gaps in our understanding of sub-lethal toxicity, environmental fate, species sensitivity distributions, and/or surface water concentrations for each of the active ingredients reviewed. More generally, we identified a need for more baseline fish and fish habitat data, ongoing environmental monitoring, development of marine and sediment-toxicity benchmarks, improved study design including sufficiently low method detection limits, and collaboration around accessible data reporting and management.

Effects of weathered sediment-bound dilbit on freshwater amphipods (Hyalella azteca)

Bitumen mined in the oil sands region of Northern Alberta, Canada, is diluted with natural gas condensates to form dilbit, which is transported through pipelines. Sections of these pipelines come close to freshwater ecosystems. If dilbit is spilled into or near an aquatic environment, environmental weathering processes, such as evaporation and sediment interaction, influence the fate and toxicity of dilbit to aquatic organisms. To date, most studies of the effects of dilbit on the health of aquatic organisms have not considered weathering processes. Thus, the goal of this study was to assess the toxicity of weathered sediment-bound dilbit (WSD) to an aquatic organism. Adult freshwater amphipods (Hyalella azteca) were exposed directly to WSD or the water-soluble fraction (WSF) of WSD. Direct exposure to WSD resulted in oil-mineral aggregates adhering to the appendages and gas exchange structures of amphipods, causing acute lethality. After a 10-min exposure to WSD, amphipods consumed half as much oxygen and their appendage movement was impaired. Exposure to the WSF, which contained a total PAH concentration of 1.08 μg/L, did not result in acute lethality, or significantly affect respiration, activity or acetylcholinesterase activity. Results of the present study indicate that physical interaction with oil-mineral aggregates after a spill of dilbit is a threat to benthic invertebrates, whereas the WSF does not cause acute adverse effects. As the transport of dilbit through pipelines increases in North America, studies must incorporate environmental weathering processes when determining the effects of dilbit on aquatic organisms.

The Single and Combined Effects of Wildfire Runoff and Sediment-Bound Copper on the Freshwater Amphipod Hyalella azteca

The frequency of wildfire is expected to increase with time as a function of climate change. Recent studies in our laboratory have demonstrated that pyrogenic polycyclic aromatic hydrocarbons can cause greater-than-additive effects in Hyalella azteca in the presence of low concentrations of Cu. We hypothesized that freshwater animals inhabiting Cu-contaminated sites, such as those in the vicinity of Cu mines, may be vulnerable to nonadditive toxicity from contaminants released by wildfires. To investigate the interaction between Cu and water conditioned by burnt wood ash (fire extract), we exposed H. azteca for 14 d to binary mixtures of 225 mg/kg Cu-enriched artificial sediment (225 mg Cu/kg) and a fire extract dilution series (12.5, 25, 50, 75, and 100%). All binary mixtures of Cu-enriched sediment and fire extract resulted in complete mortality with the exception of Cu-enriched sediment + 12.5% fire extract. The combination of Cu-enriched sediment with 12.5% fire extract had a more-than-additive effect on survival and tissue Cu concentration, but there was no reduction in growth or acetylcholinesterase activity compared to the 225 mg/kg Cu-contaminated sediment or fire extract control, respectively. Acetylcholinesterase activity was significantly reduced in amphipods exposed to fire extract, but the presence of Cu did not exacerbate this effect. The results suggest that Cu-contaminated water bodies that receive runoff from wildfires are at risk of enhanced toxicity. Environ Toxicol Chem 2020;39:1988-1997. © 2020 SETAC.

In Situ Reproductive Bioassay with Caged Gammarus fossarum (Crustacea): Part 1-Gauging the Confounding Influence of Temperature and Water Hardness

Monitoring the adverse effects of environmental contaminants on the reproduction of invertebrate species in the field remains a challenge in aquatic ecotoxicology. To meet the need for reliable tools for in situ toxicity assessment, we present the first part of a methodological study of the in situ implementation of a reproductive bioassay in Gammarus previously developed for screening the toxicity of chemical compounds during laboratory exposure. To ensure the correct interpretation of the modulation of reproductive markers (molting, fecundity, follicle growth, and embryonic development) in uncontrolled environmental conditions, we experimentally assessed and statistically modeled the variability in the female reproductive cycle during laboratory exposure under several temperature and water hardness conditions. Whereas water hardness did not influence the reproductive cycle, the significant accelerating effect of temperature on the dynamics of molting and marsupial development was finely modeled, by detailing the influence of temperature on the probability of transition between all molt and embryonic stages along the female cycle. In addition, no effect of temperature or water hardness was detected on the number of oocytes and embryos carried by females. Furthermore, the finding that the relative durations of the first 4 molt and embryonic stages are constant whatever the temperature makes it possible to predict the molting dynamics in fluctuating temperature conditions. Because this could allow us to take into account the confounding influence of temperature on the measurement of reproductive markers, the implications of these findings for an optimal in situ implementation of the reproductive bioassay with G. fossarum are discussed. The relevance of this modeling approach during in situ implementation is tested in a companion study. Environ Toxicol Chem 2020;39:667-677. © 2019 SETAC.

Bioaccumulation, Biotransformation, and Synergistic Effects of Binary Fungicide Mixtures in Hyalella azteca and Gammarus pulex: How Different/Similar are the Two Species?

Aquatic organisms are consistently exposed to a mixture of micropollutants that can bioaccumulate, undergo biotransformation, and may exert mixture effects. However, little is known on the underlying mechanisms and species-specificity. Herein we investigated bioaccumulation, biotransformation and synergistic effects of azole (i.e., prochloraz) and strobilurin (i.e., azoxystrobin) fungicides in the two aquatic invertebrate species, Hyalella azteca and Gammarus pulex. Bioaccumulation of azoxystrobin was similar, whereas bioaccumulation of prochloraz was slightly different in the two species but was still significantly below the REACH criteria for bioaccumulative substances. Similar biotransformation patterns were observed in both species, and only a few unique biotransformation reactions were detected in H. azteca such as malonyl-glucose and taurine conjugation. Toxicokinetic modeling additionally indicated that biotransformation is a more important elimination pathway in H. azteca. In mixtures, no-observed-adverse-effect levels of prochloraz decreased the LC₅₀s of azoxystrobin in both species which correlated well with increased internal azoxystrobin concentrations. This synergistic effect is partly due to the inhibition of cytochrome P450 monooxygenases by prochloraz which subsequently triggered the reduced biotransformation of azoxystrobin (lower by five folds in H. azteca). The largely similar responses in both species suggest that the easier-to-cultivate H. azteca is a promising representative of invertebrates for toxicity testing.

Sensitivity of multiple life stages of 2 freshwater mussel species (Unionidae) to various pesticides detected in Ontario (Canada) surface waters

Freshwater mussels contribute important ecological functions to aquatic systems. The water filtered by mussel assemblages can improve water quality, and the mixing of sediments by burrowing mussels can improve oxygen content and release nutrients. However, nearly 70% of North American freshwater mussel species are listed as either endangered, threatened, or in decline. In Ontario, 28 species are in decline or in need of protection. Even though freshwater mussels have a heightened sensitivity to some contaminants, few studies have investigated the risks that various pesticide classes pose to one freshwater mussel species or among life stages. Lampsilis siliquoidea and Villosa iris were the focus of the present study, with the latter currently listed as of "special concern" in Canada. A potential risk to the recovery of freshwater mussel species is the presence and persistence of pesticides in Ontario surface waters. Acute (48 h) toxicity tests were performed with V. iris glochidia to determine the effect on viability (surrogate for survival) following exposure to 4 fungicides (azoxystrobin, boscalid, metalaxyl, and myclobutanil), 3 neonicotinoids (clothianidin, imidacloprid, and thiamethoxam), 2 carbamates (carbaryl and malathion), 1 organophosphate (chlorpyrifos), and 1 butenolide (flupyradifurone). Juvenile and adult L. siliquoidea were also exposed to azoxystrobin, clothianidin, imidacloprid (juvenile only), and carbaryl (adult only). Our study found in general that all life stages were insensitive to the pesticides tested, with median effect and lethal concentrations >161 µg/L. The pesticides tested likely represent a minimal risk (hazard quotients <5.4 × 10^-3 ) to freshwater mussel viability and survival in acute (48 h) and subchronic (28 d) exposures, respectively, in Ontario streams where pesticide concentrations were considerably lower than those tested in the present study. Environ Toxicol Chem 2018;37:2871-2880. © 2018 SETAC.

Development of polyurethane-based passive samplers for ambient monitoring of urban-use insecticides in water

Widespread use of insecticides for the control of urban pests such as ants, termites, and spiders has resulted in contamination and toxicity in urban aquatic ecosystems in different regions of the world. Passive samplers are a convenient and integrative tool for in situ monitoring of trace contaminants in surface water. However, the performance of a passive sampler depends closely on its affinity for the target analytes, making passive samplers highly specific to the types of contaminants being monitored. The goal of this study was to develop a passive sampler compatible with a wide range of insecticides, including the strongly hydrophobic pyrethroids and the weakly hydrophobic fipronil and organophosphates. Of six candidate polymeric thin films, polyurethane film (PU) was identified to be the best at enriching the test compounds. The inclusion of stable isotope labeled analogs as performance reference compounds (PRCs) further allowed the use of PU film for pyrethroids under non-equilibrium conditions. The PU sampler was tested in a large aquarium with circulatory water flow, and also deployed at multiple sites in surface streams in southern California. The concentrations of pesticides derived from the PU sampler ranged from 0.5 to 18.5 ng/L, which were generally lower than the total chemical concentration measured by grab samples, suggesting that suspended particles and dissolved organic matter in water rendered them less available. The influence of suspended particles and dissolved organic matter on bioavailability was more pronounced for pyrethroids than for fipronils. The results show that the developed PU film sampler, when coupled with PRCs, may be used for rapid and sensitive in-situ monitoring of a wide range of insecticides in surface water.

Critical and systematic evaluation of data for estimating human exposures to 2,4-dichlorophenoxyacetic acid (2,4-D) - quality and generalizability

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been commercially available since the 1940's. Despite decades of data on 2,4-D in food, air, soil, and water, as well as in humans, the quality the quality of these data has not been comprehensively evaluated. Using selected elements of the Biomonitoring, Environmental Epidemiology, and Short-lived Chemicals (BEES-C) instrument (temporal variability, avoidance of sample contamination, analyte stability, and urinary methods of matrix adjustment), the quality of 156 publications of environmental- and biomonitoring-based 2,4-D data was examined. Few publications documented steps were taken to avoid sample contamination. Similarly, most studies did not demonstrate the stability of the analyte from sample collection to analysis. Less than half of the biomonitoring publications reported both creatinine-adjusted and unadjusted urine concentrations. The scope and detail of data needed to assess temporal variability and sources of 2,4-D varied widely across the reviewed studies. Exposures to short-lived chemicals such as 2,4-D are impacted by numerous and changing external factors including application practices and formulations. At a minimum, greater transparency in reporting of quality control measures is needed. Perhaps the greatest challenge for the exposure community is the ability to reach consensus on how to address problems specific to short-lived chemical exposures in observational epidemiology investigations. More extensive conversations are needed to advance our understanding of human exposures and enable interpretation of these data to catch up to analytical capabilities. The problems defined in this review remain exquisitely difficult to address for chemicals like 2,4-D, with short and variable environmental and physiological half-lives and with exposures impacted by numerous and changing external factors.

Acute toxicity and esterase response to carbaryl exposure in two different populations of amphipods Hyalella curvispina

During the last years, a carbaryl insecticide was extensively applied in the valley of Río Negro and Neuquén, North Patagonia Argentina, to manage codling moths (Cydia pomonella), the main pest of pear and apple trees. In this study carbaryl susceptibility and B-esterase activity from both insecticide-exposed and non-exposed field populations of amphipods Hyalella curvispina were studied. Two subpopulations, one susceptible to carbaryl (LC₅₀=213±7.5μg/L carbaryl) and one resistant to it (LC₅₀=14,663±2379μg/L carbaryl), were found in the agricultural area selected in this study. Both populations were, in turn, more resistant to carbaryl than the population from a pristine area (LC₅₀=11.31±2.27μg/L carbaryl). The in vivo 48h-IC₅₀ values for cholinesterase (ChE) were close to the corresponding 48h-LC₅₀ values as determined for the non-exposed population (IC₅₀=7.16±0.86μg/L carbaryl) and for the susceptible subpopulation from the insecticide-exposed site (IC₅₀=193±99μg/L carbaryl). Carbaryl exposure of the amphipods from the agricultural area mentioned above produced a significant decrease of carboxylesterase (CabE) activity, at a sublethal concentration (10μg/L) that was not able to significantly inhibit ChE, thereby showing a protective role of CabE and its usefulness as early biomarker. However, at lethal concentrations the inhibition of ChE activity was higher than that of CabE. On the other hand, CabE of amphipods from the pristine site was less sensitive to carbaryl than ChE, suggesting a different participation of CabE in ChE protection in the susceptible population of H. curvispina. Pulse exposure to carbaryl for 2h caused a significant inhibition of ChE in amphipods from both populations, with a fast recovery as expected for a carbamate insecticide. In conclusion, we proved that amphipods from the said agricultural area have developed resistance to carbaryl and showed the presence of two subpopulations with a different response to the insecticide. Moreover, these results reinforce the use of ChE together with CabE inhibition as indicators of carbamate exposure in H. curvispina.

Single and joint toxic effects of five selected pesticides on the early life stages of zebrafish (Denio rerio)

Instead of individual ones, pesticides are usually detected in water environment as mixtures of contaminants. Laboratory tests were conducted in order to investigate the effects of individual and joint pesticides (phoxim, atrazine, chlorpyrifos, butachlor and λ-cyhalothrin) on zebrafish (Denio rerio). Results from 96-h semi-static toxicity test indicated that λ-cyhalothrin had the greatest toxicity to the three life stages (embryonic, larval and juvenile stages) of D. rerio with LC₅₀ values ranging from 0.0031 (0.0017-0.0042) to 0.38 (0.21-0.53) mg a.i. L^-1, followed by butachlor and chlorpyrifos with LC₅₀ values ranging from 0.45 (0.31-0.59) to 1.93 (1.37-3.55) and from 0.28 (0.13-0.38) to 13.03 (7.54-19.71) mg a.i. L^-1, respectively. In contrast, atrazine showed the least toxicity with LC₅₀ values ranging from 6.09 (3.34-8.35) to 34.19 (24.42-51.9) mg a.i. L^-1. The larval stage of D. rerio was a vulnerable period to most of the selected pesticides in the multiple life stages tested. Pesticide mixtures containing phoxim and λ-cyhalothrin exerted synergistic effects on the larvae of D. rerio. Moreover, the binary mixture of phoxim-atrazine also displayed synergistic response to zebrafish. It has been assumed that most chemicals are additive in toxicity. Therefore, it is crucial to clarify the synergistic interaction for pesticide regulators and environment managers. In the present study, our data provided a clear picture on ecological risk of these pesticide mixtures to aquatic organisms. Moreover, joint effects play a more important role than individual ones, which require more attention when defining standard for water environment quality and risk assessment protocols.