Pyrethroid sorption to Sacramento River suspended solids and bed sediments

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.

Pyrethroid insecticides in urban catch basins: A potential secondary contamination source for urban aquatic systems

Pesticide contamination is a threat to many aquatic habitats, and runoff from residential homes is a major contributor of these chemicals in urban surface streams and estuaries. Improved understanding of their fate and transport can help identify areas of concern for monitoring and management. In many urban areas, runoff water congregates in numerous underground catch basins before draining into the open environment; however, at present essentially no information is available on pesticide presence in these systems. In this study, we collected water samples from a large number of underground urban catch basins in different regions of California during the active pest management season to determine the occurrence and profile of the widely used pyrethroid insecticides. Detectable levels of pyrethroids were found in 98% of the samples, and the detection frequency of individual pyrethroids ranged from no detection for fenpropathrin to 97% for bifenthrin. In the aqueous phase, total pyrethroid concentrations ranged from 3 to 726 ng/L, with a median value of 32 ng/L. Pyrethroids were found to be enriched on suspended solids, with total concentrations ranging from 42 to 93,600 ng/g and a median value of 2,350 ng/g. In approximately 89% of the samples, whole water concentrations of bifenthrin were predicted to have toxic units >1 for sensitive aquatic invertebrates. The high detection frequency of bifenthrin and overall pyrethroid concentrations, especially for particle-bound residues, suggest that underground urban catch basins constitute an important secondary source for extended and widespread contamination of downstream surface waters by pesticides such as pyrethroids in urban regions.

Occurrence and ecotoxicological risk assessment of pesticides in sediments of the Rosetta branch, Nile River, Egypt

This study aimed to (1) monitor the occurrence and spatiotemporal variations of 100 pesticides in sediments collected monthly from July 2018 to June 2019 from sampling sites in El-Rahawy, Sabal, and Tala, along the Rosetta branch of the Nile River, Egypt, and (2) perform an ecological risk assessment for aquatic organisms upon exposure to the detected sediment pesticides based on the risk quotient (RQ) method. Out of the 100 pesticides monitored, 16 pesticides belonging to seven chemical families were detected, and 55% of the sediment samples were contaminated with one or more pesticide residues. The mean concentration (mg/kg dry weight (dw)) and detection frequency (%) of the four most frequently detected pesticides in the sediment samples were as follows: chlorpyrifos (0.18 mg/kg dw and 34%), p,p'-DDE (0.018 mg/kg dw and 30%), cypermethrin (0.03 mg/kg dw and 14%), and deltamethrin (0.026 mg/kg dw and 13%). The spatial distribution exhibited that El-Rahawy had the highest pesticide load (2.86 mg/kg dw) among the studied sites, whereas the temporal variations revealed that the highest total pesticide concentrations were detected in winter season (1.73 mg/kg dw). Meanwhile, 12 pesticides showed high RQs (>1), posing a potential ecological risk to aquatic species that live and feed on such sediments.

Bioavailability of legacy and current-use pesticides in juvenile Chinook salmon habitat of the Sacramento River watershed: Importance of sediment characteristics and extraction techniques

The Sacramento River watershed, California, provides important rearing and migratory habitat for several species of conservation concern. Studies have suggested significant benefits for juvenile fish rearing in floodplain habitats of the watershed compared to the mainstem Sacramento River. However, the potential for contaminant exposure in each of these two habitats is poorly understood. Consequently, the present study aimed to determine the distribution and occurrence of bioavailable pesticides within two known salmon habitats using a suite of approaches including exhaustive chemical extraction, single-point Tenax extraction (SPTE) and ex situ passive sampling. Sediment samples were collected from sites within both habitats twice annually in 2019 and 2020, with inundation of the floodplain and high flows for both areas in 2019 and low flow conditions observed in 2020. Sediment characteristics including total organic carbon, black carbon and particle size distribution were determined to elucidate the influence of physical characteristics on pesticide distribution. Using exhaustive extractions, significantly greater sediment concentrations of organochlorines were observed in the floodplain compared to the Sacramento River in both years, with bioaccessible organochlorine concentrations also significantly greater in the floodplain (ANOVA, p < 0.05). Using both SPTEs and exhaustive extractions, significantly fewer pesticides were detected across both sites under low flow conditions as compared to high flow conditions (Poisson regression, p < 0.05). Sediment characteristics including percent fines and black carbon had significant positive relationships with total and bioaccessible pyrethroid and organochlorine concentrations. Fewer analytes were detected using low-density polyethylene (LDPE) passive samplers as compared to SPTEs, suggesting greater sensitivity of the Tenax technique for bioavailability assessments. These findings suggest that threatened juvenile fish populations rearing on the floodplain may have greater exposure to organochlorines than fish inhabiting adjacent riverine habitats, and that pesticide exposure of resident biota may be exacerbated during high-flow conditions.

The V1016G mutation of the voltage-gated sodium channel (VGSC) gene contributes to the insecticide resistance of Aedes aegypti from Makassar, Indonesia

Aedes aegypti represents one of the main vectors of at least five relevant arthropod-borne viral infections in humans (i.e., Rift Valley fever, Dengue fever, Zika, chikungunya, and yellow fever) worldwide. Ae. aegypti control strategies are mostly based on using chemical insecticides (i.e., organophosphates, pyrethroids, carbamates, and organochlorines) and reducing larval sources. Furthermore, monitoring the growth activity and mapping the geographical distribution of insecticide resistance are mandatory, as recommended by the WHO. Accordingly, we conducted a study on the possible mechanism by which Ae. aegypti develops resistance to several frequently used chemical insecticides (i.e., λ-cyhalothrin, bendiocarb, cyfluthrin, deltamethrin, malathion, and permethrin) in the city of Makassar, Sulawesi, Indonesia. The results showed the progression of resistance toward the examined insecticides in Ae. aegypti populations in Makassar. The mortality rate of Ae. aegypti was less than 90%, with the highest resistance recorded against 0.75% permethrin. The molecular evaluation of the voltage-gated sodium channel gene (VGSC) showed a significant correlation of the V1016G gene mutation in the tested 0.75% permethrin-resistant Ae. aegypti phenotypes. Nevertheless, the F1534C point mutation in the VGSC gene of Ae. aegypti did not show a significant correlation with the phenotype exhibiting insecticide resistance to 0.75% permethrin. These results indicate that Ae. aegypti mosquitoes in Makassar City have developed resistance against the frequently used insecticide permethrin, which might spread to less-populated regions of Sulawesi. Therefore, we call for further entomological monitoring of insecticide resistance not only on Sulawesi but also on other closely located islands of the Indonesian archipelago to delay the spread of Ae. aegypti insecticide resistance.

Temporal-spatial distribution of synthetic pyrethroids in overlying water and surface sediments in Guangzhou waterways: potential input mechanisms and ecological risk to aquatic systems

Temporal-spatial distribution of synthetic pyrethroids (SPs) in overlying water and surface sediments and ecological risk to aquatic systems were investigated, where paired water and surface sediments were collected during dry and wet periods in Guangzhou urban waterways. Eight target SPs (i.e., tefluthrin, bifenthrin, cyhalothrin, permethrin, cyfluthrin, cypermethrin, esfenvalerate, and deltamethrin), with cypermethrin and permethrin as major components, were ubiquitously detected in both water (dissolved and particle phases, separately) and sediments. Significant increases of ΣSP (sum of eight SPs) concentrations were observed in both water and sediment from the dry period to the wet period. The spatial distribution of SPs was mostly impacted by land-use type, with the highest ΣSP concentrations in the residential areas, which indicates the massive application of pyrethroids in household mosquito control. It is demonstrated that SPs preferred to be adsorbed to the particles, and rainfall-induced runoff was suggested as an important mechanism that moved SPs to the receiving waterways. A rising trend on sediment concentrations of SPs in the Guangzhou area in the last decade implied increasing application of pyrethroid insecticides, with cypermethrin and permethrin as the dominant components, where the contamination of SPs was positively related with urbanization rate (e.g., resident population and green coverage area). A special emphasis was placed on the potential effects of both individual SPs and their mixtures in three trophic levels (i.e., algae, daphnia, and fish) using toxic units (TUs) and risk quotients (RQs) for water and sediments. In spite of no acute effects due to SPs in the sediments, the toxic units showed daphnia as the most sensitive species in water, with acute risks to daphnia exhibited in several sampling sites. The risk assessment points out that a chronic toxicity (RQ index) caused by SPs in three trophic levels (algae, daphnia, and fish) exists, especially in Daphnia magna. Graphical abstract.

Adverse effects of a synthetic pyrethroid insecticide cypermethrin on life parameters and antioxidant responses in the marine copepods Paracyclopina nana and Tigriopus japonicus

To find the adverse effects induced by cypermethrin, the ecotoxicological model copepods Tigriopus japonicus and Paracyclopina nana were exposed under cypermethrin, which is a widely used type-II pyrethroid insecticide in agriculture. Despite its large-scale application as insecticide in agriculture, little information is available on its adverse effects on aquatic invertebrates. In this study, the toxicity of cypermethrin on two copepods was assessed based on life parameters (growth rate and reproduction), oxidative stress and consequent antioxidant enzymatic activities, and gene expression profiles of antioxidants. The acute toxicity alone demonstrated that P. nana is less tolerant and sensitive against cypermethrin, compared to T. japonicus. However, under chronic exposure, life parameters of both P. nana and T. japonicus were severely affected by cypermethrin. Among antioxidant enzymatic activities, superoxide dismutase (SOD) and glutathione S-transferase (GST), in particular, demonstrated significant increase in response to cypermethrin. Furthermore, temporal-mRNA expression profile showed modulations in antioxidant related genes in response to cypermethrin. Our results provide the underlying toxic mechanism of cypermethrin and the oxidative stress defense mechanism and species-specific tolerance against cypermethrin in two model copepods species.

Grain size analysis of California waterbodies to determine the spatial extent and temporal trends of depositional areas where hydrophobic organic compounds could accumulate

The objective of this study was to summarize the grain size data from 1993 to 2016 from California water bodies and determine the number and percent of sites where sediment samples are primarily depositional sediment (more than 50% silt/clay) or non-depositional sediment (less than 50% silt/clay). Fine grain depositional areas were of interest because these are areas where hydrophobic organic compounds (HOCs) can accumulate if sources exist. Trends analysis of percent silt/clay data were conducted for all nine California Water Board Regions if adequate data for this type of analysis were available. Sediment sampling protocols were reviewed for all the grain size measurements to determine if depositional areas were targeted or random sampling was conducted. Twelve of the 13 sediment sampling protocols targeted depositional areas. Based on 23 years of data from 685 sites (1859 observations) in all 9 California Regions, the summary analysis showed that only 58% of the sites were considered depositional areas even when targeted sampling for depositional areas was used. Since only slightly more than half the sites were reported as depositional areas based on sampling that targets depositional areas, these results would certainly suggest that depositional areas are not dominant. In fact, for the one protocol where random sampling was used, depositional areas were not reported to be dominant. From an ecological risk perspective, the implication of this finding is that HOCs would not be expected to accumulate in the dominant type of sediment found in most California waterbodies. Trends analysis of percent silt/clay data showed mixed results for the various California Regions.

Global occurrence of pyrethroid insecticides in sediment and the associated toxicological effects on benthic invertebrates: An overview

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.

Suspended particles only marginally reduce pyrethroid toxicity to the freshwater invertebrate Gammarus pulex (L.) during pulse exposure

Current ecotoxicological research on particle-associated pyrethroids in freshwater systems focuses almost exclusively on sediment-exposure scenarios and sediment-dwelling macroinvertebrates. We studied how suspended particles influence acute effects of lambda-cyhalothrin and bifenthrin on the epibenthic freshwater amphipod Gammarus pulex (L.) using brief pulse exposures followed by a 144 h post exposure recovery phase. Humic acid (HA) and the clay mineral montmorillonite (MM) were used as model sorbents in environmentally realistic concentrations (5, 25 and 125 mg L(-1)). Mortality of G. pulex was recorded during the post exposure recovery phase and locomotor behavior was measured during exposure to lambda-cyhalothrin. We found that HA in concentrations ≥25 mg L(-1) adsorbed the majority of pyrethroids but only reduced mortality of G. pulex up to a factor of four compared to pyrethroid-only treatments. MM suspensions adsorbed a variable fraction of pyrethroids (10% for bifenthrin and 70% for lambda-cyhalothrin) but did not significantly change the concentration-response relationship compared to pure pyrethroid treatments. Behavioral responses and immobilisation rate of G. pulex were reduced in the presence of HA, whereas behavioral responses and immobilisation rate were increased in the presence of MM. This indicates that G. pulex was capable of sensing the bioavailable fraction of lambda-cyhalothrin. Our results imply that suspended particles reduce to only a limited extent the toxicity of pyrethroids to G. pulex and that passive uptake of pyrethroids can be significant even when pyrethroids are adsorbed to suspended particles.

Characteristics of suspended solids affect bifenthrin toxicity to the calanoid copepods Eurytemora affinis and Pseudodiaptomus forbesi

Bifenthrin is a pyrethroid pesticide that is highly toxic to aquatic invertebrates. The dissolved concentration is generally thought to be the best predictor of acute toxicity. However, for the filter-feeding calanoid copepods Eurytemora affinis and Pseudodiaptomus forbesi, ingestion of pesticide-bound particles could prove to be another route of exposure. The present study investigated bifenthrin toxicity to E. affinis and P. forbesi in the presence of suspended solids from municipal wastewater effluent and surface water of the San Francisco (CA, USA) Estuary. Suspended solids mitigated the toxicity of total bifenthrin to E. affinis and P. forbesi, but mortality was higher than what would be predicted from dissolved concentrations alone. The results indicate that the toxicity and bioavailability of particle-associated bifenthrin was significantly correlated with counts of 0.5-µm to 2-µm particle sizes. Potential explanations could include direct ingestion of bifenthrin-bound particles, changes in food consumption and feeding behavior, and physical contact with small particles. The complex interactions between pesticides and particles of different types and sizes demonstrate a need for future ecotoxicological studies to investigate the role of particle sizes on aquatic organisms.

Relationship of bifenthrin sediment concentrations to grain size and total organic carbon in California waterbodies: implications for ecological risk

A summary analysis of data sets from six California waterbodies was conducted to determine the relationship of bifenthrin sediment concentrations to: % sand/gravel; % silt; % clay; % silt/clay and % total organic carbon (TOC). The relationship of TOC to % sand/gravel, % silt, % clay, and % silt/clay was also analyzed. Statistically significant and meaningful direct relationships were reported between bifenthrin and % TOC, % silt, % clay and % silt/clay while a significant and meaningful inverse relationship was reported between bifenthrin and % sand/gravel. A significant and meaningful inverse relationship was reported between % TOC and % sand/gravel, while a significant and meaningful direct relationship was reported between % TOC and % silt, % clay and % silt/clay. Significant bifenthrin sediment concentrations would not be expected in non-depositional (sand/gravel) areas which have been reported to be dominant in various streams in California's Central Valley and are also the preferred habitat for many benthic macroinvertebrate taxa.

Distribution of pyrethroid insecticides in secondary wastewater effluent

Although the freely dissolved form of hydrophobic organic chemicals may best predict aquatic toxicity, differentiating between dissolved and particle-bound forms is challenging at environmentally relevant concentrations for compounds with low toxicity thresholds such as pyrethroid insecticides. The authors investigated the distribution of pyrethroids among 3 forms: freely dissolved, complexed with dissolved organic carbon, and sorbed to suspended particulate matter, during a yearlong study at a secondary wastewater treatment plant. Effluent was fractionated by laboratory centrifugation to determine whether sorption was driven by particle size. Linear distribution coefficients were estimated for pyrethroid sorption to suspended particulate matter (K(id)) and dissolved organic carbon (K(idoc)) at environmentally relevant pyrethroid concentrations. Resulting K(id) values were higher than those reported for other environmental solids, and variation between sampling events correlated well with available particle surface area. Fractionation results suggest that no more than 40% of the pyrethroid remaining in secondary effluent could be removed by extending settling periods. Less than 6% of the total pyrethroid load in wastewater effluent was present in the dissolved form across all sampling events and chemicals.

Comparing sorption behavior of pyrethroids between formulated and natural sediments

Formulated sediments are recommended for use in toxicity tests to achieve standardized evaluations. However, the organic matter used in formulated sediments may differ qualitatively from that in natural sediments, which may lead to different chemical partition patterns and, hence, different toxicity effects. By deriving partition coefficients for organic carbon and dissolved organic carbon (K(OC) and K(DOC) , respectively) for eight pyrethroid insecticides from three formulated and five natural sediments, the authors characterized the differences between formulated and natural sediments in pesticide sorption. For all pyrethroids, the mean values of K(OC) and K(DOC) of formulated sediments were two to three, and three to 10 times smaller than those of natural sediments, respectively. The two formulated sediments containing α-cellulose or Manitoba peat showed significantly (p<0.0001) smaller K(OC) and K(DOC) values than natural sediments based on statistical analyses, while the difference was not significant for the formulated sediment containing New Brunswick peat. The K(OC) values were closely correlated (p<0.001) with soot carbon content, while the amount of carboxylic or phenolic functional groups may have affected K(DOC) . Therefore, the source and quality of organic matter are likely the most important factors in formulated sediments and must be standardized to provide consistency in sediment toxicity tests.