Current-use Insecticides Research Articles

Aquatic-Terrestrial Insecticide Fluxes: Midges as Neonicotinoid Vectors.

Exposure of freshwater ecosystems to insecticides can negatively impact the development of emerging aquatic insects. These insects serve as an important nutritional subsidy for terrestrial insectivores. Changes in insect emergence phenology (i.e., emergence success and temporal pattern) or fluxes of insecticides retained by the emerging adults have the potential to negatively impact terrestrial food webs. These processes are influenced by contaminant toxicity, lipohilicity, or metabolic processes. The interplay between emergence phenology, contaminant retention through metamorphosis, and associated contaminant flux is not yet understood for current-use insecticides. In a microcosm study, we evaluated the impacts of a 24-h pulse exposure of one of three current-use insecticides, namely pirimicarb, indoxacarb, and thiacloprid, at two environmentally realistic concentration levels on the larval development and emergence of the nonbiting midge Chironomus riparius. In addition, we measured insecticide concentrations in the larvae and adults using ultrahigh performance liquid chromatography coupled to tandem mass spectrometry by electrospray ionization. Exposure to pirimicarb delayed larval development and emergence, and exposure to indoxacarb reduced emergence success. The neonicotinoid thiacloprid had the greatest impact by reducing larval survival and emergence success. At the same time, thiacloprid was the only insecticide measured in the adults with average concentrations of 10.3 and 37.3 ng/g after exposure at 0.1 and 4 µg/L, respectively. In addition, an approximate 30% higher survival to emergence after exposure to 0.1 µg/L relative to a 4-µg/L exposure resulted in a relatively higher flux of thiacloprid, from the aquatic to the terrestrial environment, at the lower exposure. Our experimental results help to explain the impacts of current-use insecticides on aquatic-terrestrial subsidy coupling and indicate the potential for widespread dietary exposure of terrestrial insectivores preying on emerging aquatic insects to the neonicotinoid thiacloprid. Environ Toxicol Chem 2023;42:60-70. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Single and combined effects of insecticides on multi-level biomarkers in the non-target amphipod Gammarus fossarum exposed to environmentally realistic levels

Aquatic media are ultimate recipients of various contaminants including pesticides pervasively applied in agrosystems. Characterizing the ecotoxicity of pesticides and their mixtures to aquatic wildlife at field-realistic levels is thus crucial for environmental risk assessment. This study aims at assessing the effects of two current-use insecticides, imidacloprid and chlorpyrifos, on Gammarus fossarum using multi-level biomarkers. In microcosms, gammarids were exposed for 72 h to insecticides tested individually or in mixture at 0.01, 0.1 and 1 μg/L of each chemical. Multi-metric responses were assessed at the individual level (behavioural traits: locomotion, respiration and amplexus formation) and the cellular level (enzymes involved in growth, moulting, digestion and cell stress). The results showed insecticide-elicited behavioural and biochemical responses from the lowest concentration of 0.01 μg/L. Overall, single exposures stimulated behavioural traits and inhibited enzymatic activities, highlighting subtle impacts at different organizational levels but these were not dose related. For binary mixtures, antagonistic effects (i.e. less-than-additive) on biomarkers were mainly observed when compared with single exposures. Multi-variable analyses indicated the complementarity of behavioural and biochemical biomarkers in identifying sublethal biological alterations and dose-dependent multiple action sites of insecticides. Besides, the mortality observed only for the mixture at 1 μg/L demonstrated a high lethal potential of insecticides in a simple binary combination. To conclude, this study demonstrates disturbances in individual performances and cellular impairments occurring at environmentally realistic exposure levels in a non-target wild species. Since the sublethal effects, such as those identified with this multi-biomarker approach, could lead to long-term alterations in population dynamics of agricultural areas, they constitute promising early endpoints for risk assessment of insecticides.

Legacy and Current-Use Insecticides in Agricultural Sediments from South China: Impact of Application Pattern on Occurrence and Risk.

Legacy and current-use insecticides were analyzed in sediments collected from a typical rice-planting region in South China. Total concentrations of insecticides varied from 1.63 to 775 ng g-1 with mean and median values of 67.0 and 11.5 ng g-1, respectively. Pyrethroids predominated pesticide composition (31.7%), followed by organophosphates (23.0%) and fiproles (20.8%). Sediment risk analysis showed that pyrethroids, fiproles, and abamectin posed significant risk to benthic invertebrates in one-third of sediments. Different distributions of pyrethroids and organophosphates in urban and agricultural areas were consistent with their application patterns, whereas legacy organochlorine pesticides showed no region-specific distribution because of rapid transition of land use pattern from agricultural to urban areas. Likely illegal use of pyrethroids and fipronil caused serious ecological risks in agricultural waterways. Pyrethroids and fipronil were restricted to use in paddy fields, but their occurrence and risk in agricultural waterways were high, calling for better measures to regulate the illegal use of insecticides.

Distribution of pesticides in dust particles in urban environments

In regions with a mild climate, pesticides are often used around homes for pest control. Recent monitoring studies have linked pesticide use in residential areas to aquatic toxicity in urban surface water ecosystems, and suggested dust particles on paved surfaces as an important source of pesticides. To test the hypothesis that dust on hard surfaces is a significant source of pesticides, we evaluated spatial and temporal patterns of current-use insecticides in Southern California, and further explored their distribution as a function of particle sizes. Pyrethroid insecticides were detected in dust from the driveway, curb gutter and street at 53.5–94.8%, with median concentrations of 1–46 ng g−1. Pyrethroid residues were uniformly distributed in areas adjacent to a house, suggesting significant redistribution. The total levels of pyrethroids in dust significantly (p < 0.01) decreased from October to February, suggesting rainfalls as a major mechanism to move pesticide residues offsite. Fipronil as well as its degradation products, were detected at 50.6–75.5%, and spatial and temporal patterns of fipronil residues suggested rapid transformations of fipronil to its biologically active intermediates. Moreover, pyrethroids were found to be enriched in fine particles that have a higher mobility in runoff than coarse particles. Results from this study highlight the widespread occurrence of pesticides in outdoor dust around homes and the potential contribution to downstream surface water contamination via rain-induced runoff.

Assessing the effects of urbanization on the environment with soil legacy and current-use insecticides: A case study in the Pearl River Delta, China

To evaluate the impacts of anthropogenic events on the rapid urbanized environment, the levels of legacy organochlorine pesticides (OCPs) and current-use insecticides (CUPs), i.e., dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), pyrethroids and organophosphates in soil of the Pearl River Delta (PRD) and surrounding areas were examined. Spatial concentration distributions of legacy OCPs and CUPs shared similar patterns, with higher concentrations occurred in the central PRD with more urbanization level than that in the PRD's surrounding areas. Furthermore, relatively higher concentrations of OCPs and CUPs were found in the residency land than in other land-use types, which may be attributed to land-use change under rapid urbanization. Moderate correlations between gross domestic production or population density and insecticide levels in fifteen administrative districts indicated that insecticide spatial distributions may be driven by economic prosperity. The soil–air diffusive exchanges of DDTs and HCHs demonstrated that soil was a sink of atmospheric o,p′-DDE, o,p′-DDD, p,p′-DDD and o,p′-DDT, and was a secondary source of HCHs and p,p′-DDT to atmosphere. The soil inventories of DDTs and HCHs (100±134 and 83±70tons) were expected to decrease to half of their current values after 18 and 13years, respectively, whereas the amounts of pyrethroids and organophosphates (39 and 6.2tons) in soil were estimated to decrease after 4 and 2years and then increase to 87 and 1.0tons after 100years. In this scenario, local residents in the PRD and surrounding areas will expose to the high health risk for pyrethroids by 2109. Strict ban on the use of technical DDTs and HCHs and proper training of famers to use insecticides may be the most effective ways to alleviate the health effect of soil contamination.

Distribution and toxicity of current-use insecticides in sediment of a lake receiving waters from areas in transition to urbanization

Current-use insecticides including organophosphate (OPs) and synthetic pyrethroid (SPs) insecticides were analyzed in 35 sediment samples collected from Chaohu Lake in China, where a transition from a traditional agricultural to a modern urbanized society is ongoing. Total concentrations of five OPs and eight SPs ranged from 0.029 to 0.681 ng/g dry weight and 0.016–301 ng/g dry weight, respectively. Toxic unit analysis showed that 13% of the sediment samples likely produced over 50% of the mortality for benthic invertebrates. Analysis also showed that cypermethrin was the principal contributor to the toxicity. Spatial distribution evaluation implied that OPs were mainly from non-point sources associated with agricultural activities. Conversely, SPs may have been derived from runoff of inflowing rivers through urban regions, as their concentrations were well-correlated with concentrations of other urban-oriented contaminants.

Effects of Pesticides Monitored with Three Sampling Methods in 24 Sites on Macroinvertebrates and Microorganisms

Grab water samples, sediment samples, and 2,2,4-trimethylpentane passive samplers (TRIMPS) were used to determine the exposure to 97 pesticides in 24 southeast Australian stream sites over 5 months. Macroinvertebrate communities and selected microorganisms (bacteria, flagellates, ciliates, amoebas, nematodes, and gastrotrichs) were sampled to detect relationships with pesticide toxicity. Sediment samples had the highest estimated toxicities in terms of toxic units (TU) for Daphnia magna (TUDM) and for Selenastrum capricornutum (TUSC). The pesticide-selective SPEARpesticides and the general SIGNAL index for macroinvertebrates exhibited negative linear relationships (r(2) = 0.67 and 0.36, respectively) with pesticide contamination in terms of log maximum TUDM (log mTUDM), suggesting macroinvertebrate community change due to pesticide exposure. Pesticide contamination was the only measured variable explaining variation in ecological quality. Variation in the densities of several microbial groups was best explained by environmental variables other than log TUs. The log mTUDM values derived from sediment concentrations were most important to establish a link with effects on macroinvertebrates, whereas log mTUDM of grab water samples had only minor contribution. Current-use insecticides and fungicides can affect macroinvertebrate communities and monitoring of sediment and continuous water sampling is needed to detect these effects.

Linking mechanistic and behavioral responses to sublethal esfenvalerate exposure in the endangered delta smelt; Hypomesus transpacificus (Fam. Osmeridae).

BackgroundThe delta smelt (Hypomesus transpacificus) is a pelagic fish species listed as endangered under both the USA Federal and Californian State Endangered Species Acts and considered an indicator of ecosystem health in its habitat range, which is limited to the Sacramento-San Joaquin estuary in California, USA. Anthropogenic contaminants are one of multiple stressors affecting this system, and among them, current-use insecticides are of major concern. Interrogative tools are required to successfully monitor effects of contaminants on the delta smelt, and to research potential causes of population decline in this species. We have created a microarray to investigate genome-wide effects of potentially causative stressors, and applied this tool to assess effects of the pyrethroid insecticide esfenvalerate on larval delta smelt. Selected genes were further investigated as molecular biomarkers using quantitative PCR analyses.ResultsExposure to esfenvalerate affected swimming behavior of larval delta smelt at concentrations as low as 0.0625 μg.L-1, and significant differences in expression were measured in genes involved in neuromuscular activity. Alterations in the expression of genes associated with immune responses, along with apoptosis, redox, osmotic stress, detoxification, and growth and development appear to have been invoked by esfenvalerate exposure. Swimming impairment correlated significantly with expression of aspartoacylase (ASPA), an enzyme involved in brain cell function and associated with numerous human diseases. Selected genes were investigated for their use as molecular biomarkers, and strong links were determined between measured downregulation in ASPA and observed behavioral responses in fish exposed to environmentally relevant pyrethroid concentrations.ConclusionsThe results of this study show that microarray technology is a useful approach in screening for, and generation of molecular biomarkers in endangered, non-model organisms, identifying specific genes that can be directly linked with sublethal toxicological endpoints; such as changes in expression levels of neuromuscular genes resulting in measurable swimming impairments. The developed microarrays were successfully applied on larval fish exposed to esfenvalerate, a known contaminant of the Sacramento-San Joaquin estuary, and has permitted the identification of specific biomarkers which could provide insight into the factors contributing to delta smelt population decline.

Occurrence and potential toxicity of pyrethroids and other insecticides in bed sediments of urban streams in central Texas

Despite heavy insecticide usage in urban areas, only a few studies have investigated the impact of current-use insecticides on benthic invertebrates in urban streams. The objective of this study was to measure the presence and concentration of current-use pesticides in sediments of residential streams in central Texas. Additionally, toxicity of these sediments to Hyalella azteca was evaluated. Sediment samples were collected from several sites in urban streams over the course of a year, of which, 66% had greater than one toxic unit (TU) of insecticide. Bifenthrin was the greatest contributor accounting for 65% of the TUs, and sediment toxicity to H. azteca correlated with the magnitude of total insecticides and bifenthrin TUs. The results of this study further raise concerns over the environmental consequences posed by many current-use insecticides, especially pyrethroids, in urban settings.

Effects of neurotoxic insecticides on heat-shock proteins and cytokine transcription in Chinook salmon (Oncorhynchus tshawytscha)

This study investigated sublethal, molecular effects of two current-use insecticides, chlorpyrifos (CP) and esfenvalerate (EV) in juvenile Chinook salmon. Heat-shock protein (hsp60, hsp70, hsp90) expression was quantified by Western blotting in muscle, liver and gill, and transcription of four cytokines (TGF-β, IL-1β, IGF-1, Mx-protein) was measured by real-time TaqMan® PCR in anterior kidney and spleen. Expression of hsp was increased in muscle and liver at ⩾1.2 and 7.2μg/L CP, and at ⩾0.01 and 0.1μg/L EV, respectively. Transcription of IL-1β and TGF-β was elevated in kidney at ⩾1.2μg/L CP, while EV had no effect. No changes in cytokine transcription were observed in the spleen. Our results show that these insecticides cause cellular effects at environmental concentrations, and that hsps are sensitive indicators of sublethal exposure to CP and EV. In addition, CP may exert immunotoxic effects by altering the transcription of important mediators of the fish immune system.

Pesticide Body Residues of Hyalella azteca Exposed to Mississippi Delta Sediments

This article discusses pesticide residues in the sediments of the Lower Mississippi River Alluvial Plain of Arkansas and Mississippi related to bioaccumumulation by the freshwater crustacean Hyalella azteca. According to the authors, most of these pesticides are the result of agricultural runoff and consist of both current use and legacy or discontinued pesticides. Three types of watersheds were investigated including National Wildlife Refuge, Best Management Practices (BMPs) and watersheds where the total maximum daily load of legacy pesticides exceeded guidelines. They concluded that BMPs have little if any impact on pesticide sequestration and few available current-use insecticides but greater legacy compounds accumulated in H. azteca tissues

Linking in situ bioassays and population dynamics of macroinvertebrates to assess agricultural contamination in streams of the Argentine pampa

The two local crustacean species Hyalella curvispina and Macrobrachium borelli were chosen for assessment of agricultural contamination in two streams (Horqueta and Maguire) in the Argentine pampa. In parallel with in situ bioassays of both species, the population dynamics and the organismic drift of H. curvispina were investigated throughout the main period of insecticide application, from December 2001 to March 2002. In Maguire none of the current-use insecticides (chlorpyrifos, α-cypermethrin, and endosulfan) in question were detected throughout the sampling period. During 1-week intervals with no contamination by insecticides the survival rate of H. curvispina varied between 77±6% (±SE, n=4) and 85±3%. In Horqueta during a week with a peak insecticide contamination of 64μg/kg chlorpyrifos in the suspended particles, a mortality of 100% was observed in the in situ bioassays for both species, H. curvispina and M. borelli. At the same time, in Maguire H. curvispina showed reduced survival rates of 23±5% and 25±18% at the two sites, while the survival rate of M. borelli was 60±11% upstream and 93±5% downstream, below a wetland. During the period with 100% mortality of H. curvispina in Horqueta, the population density of this species decreased correspondingly, from 106±26 to 0 individuals/m2. We conclude that in situ bioassays can be successfully linked to in-stream population dynamics for the same species and that this link is very useful for interpreting causal exposure–effect relationships.

Current-use insecticides, phosphates and suspended solids in the Lourens River, Western Cape, during the first rainfall event of the wet season

Pesticide contamination resulting from agricultural runoff depends on the time period between application and rainfall. In Western Cape orchard areas, the last pesticide application of the growing season in summer takes place at the end of February. Pesticides, total phosphates and total suspended solids (TSS) were measured in the Lourens River at the beginning of April 1999 prior to the first rainfall of the rainy season and in the middle of April during high discharge following the first rainfall of 9.6 mm/d. Pre-runoff samples indicated only contamination with total endosulfan (&#945;, &#946;, sulphate) at levels up to 0.06 µg/l. Runoff during the first rainfall event resulted in an increase in the levels of endosulfan, chlorpyrifos and azinphos-methyl, to 0.16. WaterSA Vol.27(1) 2001: 65-70

Comparison of spray drift- and runoff-related input of azinphos-methyl and endosulfan from fruit orchards into the Lourens River, South Africa

Spray drift and edge-of-field runoff are regarded as important routes of nonpoint-source pesticide input into aquatic surface waters, with current regulatory risk assessment in Europe focussing largely on spray drift. However, the two routes of entry had rarely been compared directly in the same catchment. To this end, the concentrations and loads of the current-use insecticides azinphos-methyl (AZP) and endosulfan (END) were monitored in the Lourens River, South Africa downstream of a 400-ha fruit orchard area during normal farming practice. Spray drift-related peak pesticide levels in the tributaries were in the range of 95th-percentiles of standard drift values according to regulatory risk assessment procedures. Resulting concentrations in Lourens River water samples ( n=3) at a discharge of 0.28 m 3/s were as high as 0.04±0.01 μ g/l AZP and 0.07±0.02 μ g/l END. Pesticide levels at the same site during runoff following 3 storm events varying in rainfall between 6.8 and 18.4 mm/d (discharge: 7.5–22.4 m 3/ s ) were considerably higher: by factors between 6 and 37 for AZP (0.26–1.5 μg/l) and between 2 and 41 for END (0.13–2.9 μg/l). Levels of pesticides associated with suspended particles were increased during runoff only up to 1247 μg/kg AZP and 12082 μg/kg END. A possible reason for the relative importance of runoff is that runoff largely integrates potential pesticide input over both time and space, because the prerequisites for the occurrence of runoff in terms of application and plot characteristics as well as meteorological conditions are far less specific than for spray drift. A probability analysis based on pesticide application patterns and 10-yr rainfall data indicates that the frequencies of rainfall events ⩾10 and ⩾15 mm/d are 3.4 and 1.7 per spraying season, respectively.

Rainfall-induced sediment and pesticide input from orchards into the lourens river, western cape, south africa: importance of a single event

Rainfall-induced runoff transported sediments and pesticides into the Lourens River and its tributaries during a 28.8-mm rainstorm in mid-December 1998. Average 1-h peak levels of current-use insecticides applied to adjacent orchard plots were 1.5μgl−1 azinphos-methyl, 0.2μgl−1 chlorpyrifos and 2.9μgl−1 total endosulfan (α, β, S) in the river itself. Respective average 1-h pesticide levels associated with suspended particles were 1247, 924 and 12082μgkg−1, along with 980μgkg−1 of prothiofos. Total suspended solids increased during runoff from 32 to 520mgl−1. The contaminated edge-of-field runoff entered the river via the tributaries directly bordering the orchard-growing areas. Increased concentrations of azinphos-methyl and prothiofos associated with suspended sediments were demonstrated to persist for about 3.5 months without any further input in one of the tributaries. This illustrates that the short-term exposure has the potential to result in long-term contamination of surface waters. In terms of chemical load during the 1-h peak discharge period, the single rainfall event caused a loss of 173gh−1 azinphos-methyl, 55gh−1 chlorpyrifos, 740gh−1 total endosulfan (α, β, S) and 41gh−1 prothiofos. Levels of contamination were extremely high; they exceed the national water quality standards and those established by the US EPA. A comparison with standard toxicity data and 24-h LC50s for the local amphipod species Paramelita nigroculus, obtained during this study, indicates that the concentrations found in the river may result in acute toxic effects on aquatic invertebrates and fishes. A probability analysis of 10-y rainfall data revealed that the frequency of a similar storm event occurring within the main spraying season is 1.7y−1.

Insecticide and metal contamination of a mixed cover agricultural watershed

Although pesticides used to control detrimental insects have changed since the wide spread use of highly persistent organochlorine insecticides in the 1940s through the 1970s, pesticides still present environmental problems. Random sampling of major watershed features of Otoucalofa Creek was conducted to study the distribution and concentration of residual and current use insecticides and metals in a mixed cover agricultural watershed. Samples of water, soil, sediment and fishes were taken from Otoucalofa Creek watershed and tested for 23 contaminants, including persistent organochlorine and current-use insecticides, PCBs and metals. Otoucalofa Creek watershed was chosen because of its location in the loess hills of northern Mississippi, USA, and the fact that its drainage includes 10,100 hectares of forest, 6,100 hectares of rowcrops, 4,900 hectares of pasture, and the small town of Water Valley (pop. 4,147). The greatest concentrations of insecticides were found in fish, but the highest concentrations of metals were found in soil and sediments. Six of 7 metals and 11 of 15 insecticides tested were present in fish samples. Arsenic and mercury averaged 0.67 μg/g and 0.31 μg/g, respectively, in soil samples and 0.25 μg/g and 0.03 μg/g in sediment samples, but were in lower concentrations in fish tissue. Relatively high concentrations of zinc were found in soil and sediment. DDT and its metabolites averaged 118 ng/g in fish, averaged only 1.90 ng/g in sediments and were undetectable in soil. Contamination of water was dependent upon storm related discharge and is therefore a transient phenomenon. Water samples taken during normal flow had the lowest concentrations of both metals and insecticides. Storm flow (High Stage) samples had significantly higher concentrations of insecticides and metals than did normal flow. Since arsenic is the only persistent contaminant still being applied to agricultural land, concentrations of residual insecticides should steadily decline. Current use insecticides were only detected seasonally and in extremely low concentrations, however, this transient, short term exposure, which may not have been as detrimental with less toxic organochlorine pesticides, is more significant with acutely toxic current use compounds.

Insecticide and metal contamination of a mixed cover agricultural watershed

Although pesticides used to control detrimental insects have changed since the wide spread use of highly persistent organochlorine insecticides in the 1940s through the 1970s, pesticides still present environmental problems. Random sampling of major watershed features of Otoucalofa Creek was conducted to study the distribution and concentration of residual and current use insecticides and metals in a mixed cover agricultural watershed. Samples of water, soil, sediment and fishes were taken from Otoucalofa Creek watershed and tested for 23 contaminants, including persistent organochlorine and current-use insecticides, PCBs and metals. Otoucalofa Creek watershed was chosen because of its location in the loess hills of northern Mississippi, USA, and the fact that its drainage includes 10,100 hectares of forest, 6,100 hectares of rowcrops, 4,900 hectares of pasture, and the small town of Water Valley (pop. 4,147). The greatest concentrations of insecticides were found in fish, but the highest concentrations of metals were found in soil and sediments. Six of 7 metals and il of 15 insecticides tested were present in fish samples. Arsenic and mercury averaged 0.67 μg/g and 0.31 μg/g, respectively, in soil samples and 0.25 μg/g and 0.03 μg/g in sediment samples, but were in lower concentrations in fish tissue. Relatively high concentrations of zinc were found in soil and sediment. DDT and its metabolites averaged 118 ng/g in fish, averaged only 1.90 ng/g in sediments and were undetectable in soil. Contamination of water was dependent upon storm related discharge land is therefore a transient phenomenon. Water samples taken during normal flow had the lowest concentrations of both metals and insecticides. Storm flow (High Stage) samples had significantly higher concentrations of insecticides and metals than did normal flow. Since arsenic is the only persistent contaminant still being applied to agricultural land, concentrations of residual insecticides should steadily decline. Current use insecticides were only detected seasonally and in extremely low concentrations, however, this transient, short term exposure, which may not have been as detrimental with less toxic organochlorine pesticides, is more significant with acutely toxic current use compounds.