Urban-use pesticides in stormwater ponds and their accumulation in biofilms.

Stormwater ponds frequently receive urban runoff, increasing the likelihood of pesticide contamination. Biofilms growing in surface waters of these ponds are known to accumulate a range of aquatic contaminants, paradoxically providing both water purification services and potentially posing a threat to urban wildlife. Thus, sampling biofilms in stormwater ponds may be a critical and biologically relevant tool for characterizing pesticide contamination and toxicity in urban environments. Here, we aimed to investigate pesticide occurrences at 21 stormwater ponds in Brampton, ON, one of Canada's fastest growing municipalities, and quantify their accumulation in biofilm. Over nine weeks, we collected time-integrated composite water and biofilm samples for analysis of ∼500 current-use and legacy pesticides. Thirty-two pesticide compounds were detected across both matrices, with 2,4-D, MCPA, MCPP, azoxystrobin, bentazon, triclopyr, and diuron having near-ubiquitous occurrences. Several compounds not typically monitored in pesticide suites (e.g., melamine and nicotine) were also detected, but only in biofilms. Overall, 56 % of analytes detected in biofilms were not found in water samples, indicating traditional pesticide monitoring practices fail to capture all exposure routes, as even when pesticides are below detection levels in water, organisms may still be exposed via dietary pathways. Calculated bioconcentration factors ranged from 4.2 to 1275 and were not predicted by standard pesticide physicochemical properties. Monitoring biofilms provides a sensitive and comprehensive supplement to water sampling for pesticide quantification in urban areas, and identifying pesticide occurrences in stormwater could improve source-tracking efforts in the future. Further research is needed to understand the mechanisms driving pesticide accumulation, to investigate toxicity risks associated with pesticide-contaminated biofilm, and to evaluate whether pesticide accumulation in stormwater pond biofilms represents a route through which contaminants are mobilized into the surrounding terrestrial and downstream aquatic environments.

New insights into pesticide occurrence and multicompartmental monitoring strategies in stream ecosystems using periphyton and suspended sediment.

Streams are susceptible to pesticide pollutants which are transported outside of the intended area of application from surrounding agricultural fields. It is essential to monitor the occurrence and levels of pesticides in aquatic ecosystems to comprehend their effects on the aquatic environment. The common sampling strategy used for monitoring pesticides in stream ecosystems is through the collection and analysis of grab water samples. However, grab water sampling may not effectively monitor pesticides due to its limited ability to capture temporal and spatial variability, potentially missing fluctuations and uneven distribution of pesticides in aquatic environments. Monitoring using periphyton and sediment sampling may offer a more comprehensive approach by accounting for accumulative processes and temporal variations. Periphyton are a collective of microorganisms that grow on hard surfaces in aquatic ecosystems. They are responsive to chemical and biological changes in the environment, and therefore have the potential to act as a cost-effective, integrated sampling tool to monitor pesticide exposures in aquatic ecosystems. The objective of this study was to assess pesticides detected through periphyton, suspended sediment, and conventional grab water sampling methods and identify the matrix that offers a more comprehensive characterization of a stream's pesticide exposure profile. Ten streams across Southern Ontario were sampled in 2021 and 2022. At each stream site, water, sediment and periphyton, colonizing both artificial and natural substrates, were collected and analyzed for the presence of ~500 pesticides. Each of the three matrices detected distinctive pesticide exposure profiles. The frequency of detection in periphyton, sediment and water matrices were related to pesticides' log Kow and log Koc (P < 0.05). In addition, periphyton bioconcentrated 22 pesticides above levels observed in the ambient water. The bioconcentration factors of pesticides in periphyton can be predicted from their log Kow (simple linear regressions, P < 0.05). The results demonstrate that sediment and periphyton accumulate pesticides in stream environments. This highlights the importance of monitoring pesticide exposure using these matrices to ensure a complete and comprehensive characterization of exposure in stream ecosystems.

An Assessment of the Toxicity of Pesticide Mixtures in Periphyton from Agricultural Streams to the Mayfly Neocloeon triangulifer.

Residual concentrations of pesticides are commonly found outside the intended area of application in Ontario's surface waters. Periphyton are a vital dietary component for grazing organisms in aquatic ecosystems but can also accumulate substantial levels of pesticides from the surrounding water. Consequently, grazing aquatic organisms are likely subjected to pesticide exposure through the consumption of pesticide-contaminated periphyton. The objectives of the present study were to determine if pesticides partition into periphyton in riverine environments across southern Ontario and, if so, to determine the toxicity of pesticides in periphyton when fed to the grazing mayfly Neocloeon triangulifer. Sites with low, medium, and high pesticide exposure based on historic water quality monitoring data were selected to incorporate a pesticide exposure gradient into the study design. Artificial substrate samplers were utilized to colonize periphyton in situ, which were then analyzed for the presence of approximately 500 pesticides. The results demonstrate that periphyton are capable of accumulating pesticides in agricultural streams. A novel 7-day toxicity test method was created to investigate the effects of pesticides partitioned into periphyton when fed to N. triangulifer. Periphyton collected from the field sites were fed to N. triangulifer and survival and biomass production recorded. Survival and biomass production significantly decreased when fed periphyton colonized in streams with catchments dominated by agricultural land use (p < 0.05). However, the relationship between pesticide concentration and survival or biomass production was not consistent. Using field-colonized periphyton allowed us to assess the dietary toxicity of environmentally relevant concentrations of pesticide mixtures; however, nutrition and taxonomic composition of the periphyton may vary between sites. Environ Toxicol Chem 2023;42:2143-2157. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Characterizing the exposure of streams in southern Ontario to agricultural pesticides.

Aquatic communities can be exposed to pesticides transported from land. Characterizing this exposure is key to predicting potential toxic effects. In this study, samples of streamwater from 21 sites were used to characterize pesticide exposure to aquatic communities. Sites were in agricultural areas of southwestern Ontario, Canada and were sampled monthly from 2012 to 2019 from April to November. Samples were analyzed for a suite of hundreds of pesticides and pesticide degradation products and other water quality indicators (e.g., nutrients). Frequently detected pesticides included herbicides (2,4-D; bentazon; MCPP; metolachlor) and neonicotinoid insecticides (NNIs) (clothianidin; thiamethoxam) which were detected in >50% of samples collected between 2015 and 2019. Non-metric multidimensional scaling (NMDS) was used to explore connections between pesticide concentrations and upstream land use and crop type. Detectable concentrations of the NNI clothianidin and many herbicides were related to corn, soybean, and grain/cereal crops while concentrations of the NNI imidacloprid, insecticide flonicamid, and fungicide boscalid were related to greenhouse/nursery land use. Potential toxicity to aquatic communities was assessed by comparing pesticide concentrations to Pesticide Toxicity Index (PTI) values. Few samples exceeded levels where acute (1% of samples) or chronic toxicity (10.5%) would be expected. The diamide insecticide chlorantraniliprole was detected in several streamwater samples at levels that may cause toxicity to aquatic invertebrates, highlighting the need for continued toxicity research into this pesticide class. The number of pesticides detected was positively correlated with nutrient and total suspended solids levels, underscoring the multiple stressors aquatic communities are exposed to in these habitats.

The impact of risk management measures on the concentrations of per- and polyfluoroalkyl substances in source and treated drinking waters in Ontario, Canada.

Risk management measures (RMMs) are a broad set of tools used in global treaties and national regulations to manage, ban or restrict the use of toxic chemicals. Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals that are persistent, bioaccumulate, biomagnify and are inherently toxic to the environment and human health. For these reasons global RMMs have been imposed on the manufacture and use of select PFAS. To evaluate the occurrence and potential current risk of PFAS in the Ontario environment, PFAS were quantitatively measured in source waters pre- (2005-2007) and post- (2012-2016, 2018-2019) implementation of RMMs. Source water samples were collected pre- (n = 105), and post-RMMs (n = 326) from lake, river and groundwater and analyzed for up to 14 PFAS. Pre-RMMs, the most frequently detected PFAS in source water were perfluorooctanoic acid (PFOA; 83%) and perfluorooctane sulfonate (PFOS; 76%) followed by perfluorohexane sulfonate (PFHxS; 47%) and the maximum ∑PFAS10 was 42.1 ng/L. Post-RMMs, the maximum ∑PFAS10 (which includes PFOS) was statistically significantly reduced to 15.5 ng/L, well below the Federal Environmental Quality Guidelines for PFOS. To evaluate post-RMMs risk to human health, 226 drinking water samples were collected from 25 drinking water systems with conventional and advanced treatment. All individual (or ∑PFAS) concentrations are well below current and proposed Health advisory levels or regulatory guidelines/standards for PFAS in drinking water with calculated Risk Quotients (RQ) <0.02. This survey indicates that the implementation of RMMs for select PFAS have made a significant difference to the concentrations detected in source waters in Ontario, Canada.

The final discharge: Quantifying contaminants in embalming process effluents discharged to sewers in ontario, Canada.

The process of embalming human remains as part of the funeral home industry, entails replacing blood with embalming fluid. Typically the unused/excess fluids are disposed of directly to the sewershed or septic system. The presence of select contaminants in sewer discharges from 8 funeral homes (facilities) in York Region, Ontario during active embalming processes was studied. A wide range of contaminants including embalming fluids (formaldehyde and triclosan); metals, conventional parameters, persistent organic pollutants (polycyclic aromatic hydrocarbons, pesticides, and polychlorinated byphenyls), nonyl phenols and active pharmaceutical ingredients (APIs) were measured in the final embalming effluent and compared to regulatory sewer limits where available. Two main constituents of embalming fluids-formaldehyde and triclosan-were detected at maximum concentrations of 561,000 µg/L and 505 µg/L respectively. Other persistent organic pollutants detected in embalming effluent included banned pesticides lindane (83 ng/L) and metabolites of DDT (DDE; 2,300 ng/L). Elevated APIs found in over-the-counter drugs and products were also frequently detected at elevated concentrations (oxybenzone, hydrocortisone, lidocaine, naproxen, ibuprofen, ciprofloxacin and DEET). Most contaminants did not exceed regulatory sewer limits where available, however others including biochemical oxygen demand (cBOD5) and conventional parameters were consistently above regulatory limits. Large amounts of formaldehyde and triclosan may pose a risk to receiving sewersheds and receiving sewage treatment plants due to their antimicrobial activities.

Acute Effects of Binary Mixtures of Imidacloprid and Tebuconazole on 4 Freshwater Invertebrates.

Receiving waters from agricultural areas can contain multiple pesticides such as the neonicotinoid imidacloprid and the fungicide tebuconazole, leading to the potential for aquatic life to be exposed to such mixtures. In the present study, the effects of tebuconazole were tested alone and in binary mixtures with imidacloprid on 4 aquatic invertebrates: Chironomus dilutus, Hyalella azteca, Lumbriculus variegatus, and Neocloeon triangulifer. Acute (96-h) median lethal concentrations (LC50s) were derived for individual compounds and used to design a binary mixture study to determine cumulative effects. The LC50s showed that imidacloprid was more potent than tebuconazole by 1 to 3 orders of magnitude for the 4 species. Lethality data from mixture experiments were analyzed using MIXTOX to determine deviations from independent action, followed by the model deviation ratio (MDR) technique to determine the biological significance and reproducibility of observed mixture effects. MIXTOX showed that the cumulative toxicities of imidacloprid-tebuconazole differed between the species: for C. dilutus there was no deviation from independent action; however, for H. azteca the mixture was antagonistic (specifically dose ratio-dependent), and for N. triangulifer it was synergistic. The MDR method showed that only observations with H. azteca significantly deviated from independent action. Because of the lack of evidence of a clear deviation from independent action and the much greater potency of imidacloprid, the weight of evidence indicates that the presence of tebuconazole is unlikely to appreciably increase the hazard from imidacloprid exposure to aquatic invertebrates. Environ Toxicol Chem 2019;00:1-17. © 2019 SETAC.

Relative chronic sensitivity of neonicotinoid insecticides to Ceriodaphnia dubia and Daphnia magna.

Neonicotinoid insecticides are a group of plant protectants frequently detected in surface waters at low concentrations. Aquatic invertebrates therefore have the potential to be exposed chronically to low concentrations of neonicotinoids. The cladocerans Daphnia magna and Ceriodaphnia dubia are among the most commonly used invertebrate test species in aquatic toxicology. Both species are known to be acutely insensitive to neonicotinoids, and while chronic toxicity has been characterized for D. magna, little research has been conducted with C. dubia. In the present study we conducted 7-d static-renewal life cycle tests for 6 neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) with C. dubia, and a 21-d test with imidacloprid with D. magna. 7-d LC50s for C. dubia ranged from 8.42 mg L-1 for imidacloprid to > 100 mg L-1 for clothianidin; 7-d reproduction EC50s were 2.98 for thiacloprid, to > 67 mg L-1 for dinotefuran. D. magna were less sensitive than C. dubia to imidacloprid, by 4-fold for lethality and 1.5-fold for reproduction; however, acute-to-chronic ratios (ACRs) were similar. ACRs, based on 48-h acute LC50s and 7- or 21-d chronic reproduction EC10s, ranged from 5.4 for acetamiprid to 53.0 for imidacloprid (mean 36.6, CV = 51%). Chronic toxicity values for both species were orders of magnitude greater than concentrations reported in the environment, and thus hazard to these cladocerans is negligible.

Chronic toxicity of 6 neonicotinoid insecticides to Chironomus dilutus and Neocloeon triangulifer.

Neonicotinoid insecticides are frequently detected in surface waters near agricultural areas, leading to a potential for chronic exposure to sensitive aquatic species. The midge Chironomus dilutus and the mayfly Neocloeon triangulifer have been shown to be acutely sensitive to neonicotinoids. Previous studies have established chronic effects of some neonicotinoids on C. dilutus, but reproduction has not been studied. Toxic effects have not been assessed using N. triangulifer. We present the results of chronic, static-renewal tests for 6 neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) with C. dilutus (≤56-d in length) and N. triangulifer (≤32-d in length). Emergence was generally the most sensitive endpoint for both species across all neonicotinoids. Effect concentrations, 10% (EC10s; emergence) were 0.03 to 1.1 µg L-1 for acetamiprid, clothianidin, imidacloprid, and thiacloprid. Dinotefuran and thiamethoxam were less potent, with EC10s (C. dilutus) or median effect concentrations (EC50s; N. triangulifer) of 2.2 to 11.2 µg L-1 . Hazard was assessed through comparison of neonicotinoid environmental concentrations from agricultural surface waters in Ontario (Canada) with either the 5th percentile hazard concentration (for imidacloprid) or species-specific EC10s from the present study (for all remaining neonicotinoids). The resulting hazard quotients (HQs) indicated little to no hazard (HQ <1) in terms of chronic toxicity for acetamiprid, dinotefuran, thiacloprid, or thiamethoxam. A moderate hazard (HQ >1) was found for emergence of N. triangulifer for clothianidin, and a high hazard (HQ = 74) was found for imidacloprid. Environ Toxicol Chem 2018;37:2727-2739. © 2018 SETAC.

Chronic effects of an environmentally-relevant, short-term neonicotinoid insecticide pulse on four aquatic invertebrates.

Neonicotinoid insecticides used in agriculture can enter freshwater environments in pulses; that is, a short-term period of a higher concentration, followed by a period of a comparatively lower concentration. Non-target aquatic arthropods are exposed to these fluctuating concentrations of neonicotinoids. The present study investigated the potential latent effects of a single environmentally-relevant 24-h pulse of imidacloprid and thiamethoxam, in separate experiments, on the early life-stages of four aquatic arthropods (Hyalella azteca, Chironomus dilutus, Hexagenia spp., and Neocloeon triangulifer). At least three nominal pulse concentrations were tested for each neonicotinoid-species combination: 2.5, 5, and 10 µg L-1, which were based on environmental monitoring in Ontario, Canada. After exposure to the pulse, organisms were assessed for survival and immobilization. Surviving organisms were then moved into clean water for a chronic post-treatment period, where endpoints including survival, growth, reproduction or emergence, depending on the species, were evaluated. Immediately after the 24-h pulse, immobilization was seen in C. dilutus and N. triangulifer in the highest imidacloprid concentrations tested (8.8 and 8.9 µg L-1, respectively). After transfer to clean water, immobilized organisms recovered, and no latent toxicity was seen for any of the evaluated endpoints. H. azteca and Hexagenia spp. showed no effects immediately after the imidacloprid pulse, or after the chronic post-treatment period. No effects were seen in any species after the thiamethoxam pulse, or the post-treatment period. The present study shows that toxic effects due to short-term pulse exposures of ~9 µg L-1 imidacloprid can occur in sensitive insect species. However, organisms can recover when the stressor ceases, with no long-term effects on test organisms.

Acute toxicity of 6 neonicotinoid insecticides to freshwater invertebrates.

Neonicotinoids are a group of insecticides commonly used in agriculture. Due to their high water solubility, neonicotinoids can be transported to surface waters and have the potential to be toxic to aquatic life. The present study assessed and compared the acute (48- or 96-h) toxicity of 6 neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) to 21 laboratory-cultured and field-collected aquatic invertebrates spanning 10 aquatic arthropod orders. Test conditions mimicked species' habitat, with lentic taxa exposed under static conditions, and lotic taxa exposed under recirculating systems. Median lethal concentrations (LC50s) and median effect concentrations (EC50s; immobility) were calculated and used to construct separate lethal- and immobilization-derived species sensitivity distributions for each neonicotinoid, from which 5th percentile hazard concentrations (HC5s) were calculated. The results showed that the most sensitive invertebrates were insects from the orders Ephemeroptera (Neocloeon triangulifer) and Diptera (Chironomus dilutus), whereas cladocerans (Daphnia magna, Ceriodaphnia dubia) were the least sensitive. The HC5s were compared with neonicotinoid environmental concentrations from Ontario (Canada) monitoring studies. For all neonicotinoids except imidacloprid, the resulting hazard quotients indicated little to no hazard in terms of acute toxicity to aquatic communities in Ontario freshwater streams. For the neonicotinoid imidacloprid, a moderate hazard was found when only invertebrate immobilization, and not lethality, data were considered. Environ Toxicol Chem 2018;37:1430-1445. © 2018 SETAC.

Interlaboratory evaluation of the assessment of arsenic bioaccumulation from field collected sediments using Hexagenia spp.

Standardized bioaccumulation testing of aquatic organisms is essential to understanding the impact of historical contamination on the quality of water and sediment. A standardized 28-d laboratory bioaccumulation method with a freshwater burrowing mayfly, Hexagenia spp., has been developed and internally validated by the Ontario Ministry of the Environment and Climate Change (MOECC). An interlaboratory comparison was conducted to assess the precision of this method. Field-collected sediment contaminated with arsenic was chosen for the present study. Control and test sediments were subsampled and sent to 6 laboratories to perform the bioaccumulation test. One laboratory failed to meet the control survival criterion of ≥80%. When results of this laboratory are removed from the arsenic accumulation assessment, the mean interlaboratory variability (expressed as coefficient of variation) of the arsenic whole-body concentration is reduced from 44% to 24% in the test sediment-exposed Hexagenia spp. There was no significant interlaboratory difference between the Hexagenia spp. arsenic accumulations. While improved culturing and organism holding guidance may increase laboratory success, the MOECC Hexagenia spp. bioaccumulation test method has tight biological method precision when the control survival criterion is met. Environ Toxicol Chem 2016;35:2448-2455. © 2016 SETAC.