First report on probabilistic risk assessment of pesticide residues in a riverine ecosystem in South-South Nigeria

Occurrence and toxicological relevance of pesticides and trace metals in agricultural soils, sediments, and water of the Sogamoso River basin, Colombia

Historical pesticide use in agriculture and trace metal accumulation have long term impact on soil, sediment, and water quality. This research quantifies legacy and current-use pesticides and trace metals, assessing their occurrence and toxicological implications on a watershed scale in the Sogamoso River basin, tributary of the Magdalena River in Colombia. Organochlorine pesticides (22), organophosphates (7), and azole fungicides (5), as well as trace metals cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) were analyzed in croplands and along the river. Toxic units (TU) and hazard quotients (HQ) were calculated to assess the mixture toxicity. Organochlorines were detected in 84% of soils, 100% of sediments, and 80% of water samples. Organophosphates were found in 100% of soil and sediment samples, as well as in 70% of water samples. Azole fungicides were present in 79% of soils, 60% of sediments, and in 10% of water samples. Total pesticide concentrations ranged from 214.2 to 8497.7 μg/kg in soils, 569.6-12768.2 μg/kg in sediments, and 0.2-4.1 μg/L in water. In addition, the use of partition coefficient (Kd) and organic carbon fraction (foc) allowed the distribution analysis for most of the pesticides in sediments, suspended particulate matter (SPM), and water systems, but not for soils. Concentrations of trace metals Cu, Zn, Pb, and Zn exceeded international quality guidelines for agricultural soils in 16% of the samples. Furthermore, Cu and Zn concentrations exceeded sediment quality guidelines in 50 and 90% of the samples, respectively. These findings demonstrate the broad distribution of complex mixtures of trace metals, legacy organochlorines, and current-use pesticides across the basin, indicating that conventional agriculture is a significant source of diffuse pollution. Sustainable agricultural practices are needed to mitigate adverse impacts on ecosystems and human health.

Assessment of environmental and human health risk from pesticide residues in river Gomti, Northern India

Rivers get polluted with diverse types of hazardous and toxic substances, pesticides being one of them. The water and sediment of rivers get contaminated with pesticide residues coming through the run-off of vast agricultural fields along the catchment area and also from domestic sewage water. The residues get bio-concentrated and bio-accumulated in different aquatic organisms and animals including fishes along the food chain. Fish, one of the important and chief sources of proteins, are consumed by humans. The presence of toxic substances like pesticides in any food item is undesirable for the fear of health hazards. We have monitored the status of pesticide residue in river Gomti, a tributary of River Ganga that passes through the Uttar Pradesh state of India. Water, sediment, and fish samples collected from the different locations along the river stretch were analyzed for 34 targeted pesticide compounds belonging to organochlorines (OC), organophosphates (OP), and synthetic pyrethroids (SP) groups. In 52% of water, 30% of sediment, and 43% of fish samples residues of OCs were detected while the OPs were present in 33%, 25%, and 39% of samples respectively. However, none of the SPs could be recorded in any sample. The concentrations of the pesticides in water indicate stress conditions to some extent to aquatic life, but based on the human health risk assessment it can be concluded that consumption of fishes from the river contaminated with different OC or OP residues would not pose any direct risk to the consumers.

Global distribution of pesticides in freshwater resources and their remediation approaches

The role of pesticides in enhancing global agricultural production is magnificent. However, their unmanaged use threatens water resources and individual health. A significant pesticide concentration leaches to groundwater or reaches surface waters through runoff. Water contaminated with pesticides may cause acute or chronic toxicity to impacted populations and exert adverse environmental effects. It necessitates the monitoring and removing pesticides from water resources as prime global concerns. This work reviewed the global occurrences of pesticides in potable water and discussed the conventional and advanced technologies for the removal of pesticides. The concentration of pesticides highly varies in freshwater resources across the globe. The highest concentration of α-HCH (6.538 μg/L, at Yucatan, Mexico), lindane (6.08 μg/L at Chilka lake, Odisha, India), 2,4, DDT (0.90 μg/L, at Akkar, Lebanon), chlorpyrifos (9.1 μg/L, at Kota, Rajasthan, India), malathion (5.3 μg/L, at Kota, Rajasthan, India), atrazine (28.0 μg/L, at Venado Tuerto City, Argentina), endosulfan (0.78 μg/L, at Yavtmal, Maharashtra, India), parathion (4.17 μg/L, at Akkar, Lebanon), endrin (3.48 μg/L, at KwaZuln-Natl Province, South Africa) and imidacloprid (1.53 μg/L, at Son-La province, Vietnam) are reported. Pesticides can be significantly removed through physical, chemical, and biological treatment. Mycoremediation technology has the potential for up to 90% pesticide removal from water resources. Complete removal of the pesticides through a single biological treatment approach such as mycoremediation, phytoremediation, bioremediation, and microbial fuel cells is still a challenging task, however, the integration of two or more biological treatment approaches can attain complete removal of pesticides from water resources. Physical methods along with oxidation methods can be employed for complete removal of pesticides from drinking water.

A SWMM-Based Screening Model for Estimating Wastewater Treatment Burden of Pesticides on the Urban Scale

To estimate the treatment load of pesticides for wastewater treatment plants (WWTPs) on an urban scale, we developed a SWMM-based screening model that integrates the mass balance of pesticides in residential soil and the storm-water runoff passing through residential lawns. Furthermore, we introduce an approximate approach that simplifies the simulation using the octanol-water partition coefficients (i.e., log K_OW) of pesticides. The results indicate that the simulated transport factors (i.e., the dissipation kinetics-relevant property from the soil) of systemic pesticides (i.e., log K_OW < 2.0) are constant, whereas those of non-systemic pesticides decrease with increasing log K_OW, indicating that highly lipophilic pesticides are thermodynamically favored for soil absorption. By using the approximate approach, we estimated the total mass of pesticides entering the urban sewer system and the pesticide concentrations in the influent of WWTPs for a midsize city. The results indicate that the estimated concentration of systemic pesticides in the influent is ~9.2 ng L^-1 and that of pesticides with log K_OW values above 3.0 is below 0.84 ng L^-1. The pesticide concentrations are consistent with published field data, indicating that the approximate approach can be applied as preliminary modeling tool to recommend pretreatment values for urban WWTPs. Although the model must be further validated and refined using field data, the screening method can be used to help urban planners and engineers to manage the treatment process of pesticides in WWTPs.

Distribution and risk assessment of pesticide residues in sediment samples from river Ganga, India

Indiscriminate use of pesticides leads to their entry in to the bottom sediments, where they are absorbed in the sediment's particle and thus, may become the consistent source of aquatic pollution. The present work was carried out to evaluate pesticide residues in the sediment samples and associated human health risk of commonly used pesticides along the basin of river Ganga. Total of 16 pesticides were analyzed along three stretches of river Ganga. The concentration of pesticides in the upper stretch ranged from ND to 0.103 μg/kg, in the middle stretch ND to 0.112 μg/kg, and in the lower stretch ND to 0.105 μg/kg. Strong positive correlation was found between total organic carbon and total pesticide residues in sediment samples. Carcinogenic and non-carcinogenic values were estimated below the threshold limit suggesting no associated risk. Risks associated with the inhalation route of exposure were found to be higher than the dermal and ingestion routes. Children were found at higher risk at each site from multiple routes of exposure than adult population groups. Toxic unit values were found to be below the threshold value suggesting no risk associated with exposure of pesticides from sediments. However, long term effects on ecological quality due to consistent pesticide exposure must not be ignored. Therefore, the present study focuses on concrete efforts like lowering the irrational used of pesticides, tapping of agricultural and domestic drains, advice to farmers for appropriate use of pesticide doses, to reduce the threat of pesticide pollution in the river system and possible human health risk.

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

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

Public health implications of endocrine disrupting chemicals in drinking water and aquatic food resources in Nigeria: A state-of-the-science review

This state-of-the-science review is aimed at identifying the sources, occurrence, and concentrations of EDCs, including potential public health risks associated with drinking water and aquatic food resources from Nigerian inland waters. A total of 6024 articles from scientific databases (PubMed, Scopus, Web of science, ScienceDirect, Google Scholar, and African Journals Online) were identified, out of which, 103 eligible articles were selected for this study. Eleven (11) classes of EDCs (OCPs, PCBs, PBDEs, PAHs, BPA, OTs, PEs, PCs, PPCPs, sterols and n-alkanes) were identified from drinking waters, river sediments and aquatic food species from Nigerian rivers, showing that OCPs were the most studied and reported EDCs. Analytical methods used were HPLC, LC-MS/MS, GC-FID, GC-ECD and GC-MS with all EDCs identified to originate from anthropogenic sources. Carcinogenic, mutagenic, and teratogenic effects were the highest (54.4 %) toxicological effects identified, while reproductive/endocrine disruptive effects (15.2 %) and obesogenic effects (4.3 %) were the least identified toxicological effects. The targeted hazard quotient (THQ) and cancer risk (CR) were generally highest in children, compared to the adult populations, indicating age-specific toxicity. PEs produced the highest THQ (330.3) and CR (1.2) for all the EDCs in drinking water for the children population, suggesting enhanced vulnerability of this population group, compared to the adult population. Due to associated public health, wildlife and environmental risk of EDCs and their increasing concentrations in drinking water and food fish species from Nigerian inland waters, there is an urgent need for focused and strategic interventions, sensitization and policy formulation/implementation towards public health and aquatic food safety in Nigeria.

Screening safe pesticide application rates in crop fields for protecting consumer health: A backward model for interim recommended rates

To reduce human health risks and comply with regulatory standards, it is necessary to provide safe application rates of pesticides in crop fields. In this study, a screening-level model is proposed to improve the regulation of pesticide application rates based on the dynamiCrop platform, which can serve as a complementary approach to field trials for regulatory agencies. The screening-level model can conveniently simulate safe application rates of pesticides based on consumer health risks and maximum residue levels (MRLs). Using 2,4-D as an example, the simulation results agreed with the data of field trials under Good Agricultural Practices and demonstrated that current manufacturers' recommended application rates can effectively comply with MRLs and protect human health. In addition, we simulated the default safe application rates of 449 pesticides in five common crops using the default values of the acceptable daily intake (ADI; 0.01 mg kg^-1  day^-1 ) and MRL (0.01 mg kg^-1 ). The results demonstrated that aerial-fruit crops (e.g., tomatoes and apples) had much lower default safe application rates of pesticides than tuber crops due to the different pesticide uptake mechanisms of plants. In addition, the MRL-based default safe application rates were significantly lower than the ADI-based default rates, indicating that the default MRL of 0.01 mg kg^-1 adopted by current regulatory agencies is very conservative regarding population health risks. Although other factors, such as the variability of residue levels in crops, occupational exposure (farmers and operators), and multiple pesticide application patterns, need to be considered in future studies, our screening-level model could be used as a complementary tool in field trials to assist regulatory agencies in regulating pesticide application rates in crop fields. Integr Environ Assess Manag 2023;19:126-138. © 2022 SETAC.

Bioaccumulation of organochlorine pesticide residues (OCPs) at different growth stages of pacific white leg shrimp (Penaeus vannamei): First report on ecotoxicological and human health risk assessment

Pesticide residues (PRs) in farmed shrimps are concerning food safety risks. Globally, India is a major exporter of pacific white leg shrimp (P. vannamei). This study was undertaken to analyze PRs in the water, sediments, shrimps, and feed at different growth stages to evaluate the ecotoxicological and human health risks. PRs in the seawater and sediments ranged from not detected (ND) to 0.027 μg/L and 0.006-12.39 μg/kg, and the concentrations were within the maximum residual limits (MRLs) and sediment quality guidelines prescribed by the World Health Organization and Canadian Environment Guidelines, respectively. PRs in shrimps at three growth stages viz. Postlarvae, juvenile, and adults, ranged from ND to 0.522 μg/kg, below the MRLs set by Codex Alimentarius Commission and European Commission. Most of the PRs in water, sediments, and shrimps did not vary significantly (p > 0.05) from days of culture (DOC-01) to DOC-90. The hazard quotient (HQ) and hazard ratio (HR) were found to be < 1, indicating that consumption of shrimps has no noncarcinogenic and carcinogenic risks. PRs in shrimp feed ranged from ND to 0.777 μg/kg and were found to be below the MRLs set by EC, which confirms that the feed fed is safe for aquaculture practices and does not biomagnify in animals. The risk quotient (RQ) and toxic unit (TU) ranged from insignificant level (ISL) to 0.509 and ISL to 0.022, indicating that PRs do not pose acute and chronic ecotoxicity to aquatic organisms. The study suggested no health risk due to PRs in shrimps cultured in India and exported to the USA, China, and Japan. However, regular monitoring of PRs is recommended to maintain a sustainable ecosystem.

Pesticides in surface freshwater: a critical review

The objective of this study was to critically review studies published up to November 2021 that investigated the presence of pesticides in surface freshwater to answer three questions: (1) in which countries were the studies conducted? (2) which pesticides are most evaluated and detected? and (3) which pesticides have the highest concentrations? Using the Prisma protocol, 146 articles published from 1976 to November 2021 were included in this analysis: 127 studies used grab sampling, 10 used passive sampling, and 9 used both sampling techniques. In the 45-year historical series, the USA, China, and Spain were the countries that conducted the highest number of studies. Atrazine was the most evaluated pesticide (56% of the studies), detected in 43% of the studies using grab sampling, and the most detected in passive sampling studies (68%). The compounds with the highest maximum and mean concentrations in the grab sampling were molinate (211.38 µg/L) and bentazone (53 µg/L), respectively, and in passive sampling, they were oxyfluorfen (16.8 µg/L) and atrazine (4.8 μg/L), respectively. The levels found for atrazine, p,p'-DDD, and heptachlor in Brazil were higher than the regulatory levels for superficial water in the country. The concentrations exceeded the toxicological endpoint for at least 11 pesticides, including atrazine (Daphnia LC₅₀ and fish NOAEC), cypermethrin (algae EC50, Daphnia and fish LC₅₀; fish NOAEC), and chlorpyrifos (Daphnia and fish LC₅₀; fish NOAEC). These results can be used for planning pesticide monitoring programs in surface freshwater, at regional and global levels, and for establishing or updating water quality regulations.

Microbial Degradation of Aldrin and Dieldrin: Mechanisms and Biochemical Pathways

As members of the organochlorine group of insecticides, aldrin and dieldrin are effective at protecting agriculture from insect pests. However, because of excessive use and a long half-life, they have contributed to the major pollution of the water/soil environments. Aldrin and dieldrin have been reported to be highly toxic to humans and other non-target organisms, and so their use has gradually been banned worldwide. Various methods have been tried to remove them from the environment, including xenon lamps, combustion, ion conversion, and microbial degradation. Microbial degradation is considered the most promising treatment method because of its advantages of economy, environmental protection, and convenience. To date, a few aldrin/dieldrin-degrading microorganisms have been isolated and identified, including Pseudomonas fluorescens, Trichoderma viride, Pleurotus ostreatus, Mucor racemosus, Burkholderia sp., Cupriavidus sp., Pseudonocardia sp., and a community of anaerobic microorganisms. Many aldrin/dieldrin resistance genes have been identified from insects and microorganisms, such as Rdl, bph, HCo-LGC-38, S2-RDL^A302S, CSRDL1A, CSRDL2S, HaRdl-1, and HaRdl-2. Aldrin degradation includes three pathways: the oxidation pathway, the reduction pathway, and the hydroxylation pathway, with dieldrin as a major metabolite. Degradation of dieldrin includes four pathways: oxidation, reduction, hydroxylation, and hydrolysis, with 9-hydroxydieldrin and dihydroxydieldrin as major products. Many studies have investigated the toxicity and degradation of aldrin/dieldrin. However, few reviews have focused on the microbial degradation and biochemical mechanisms of aldrin/dieldrin. In this review paper, the microbial degradation and degradation mechanisms of aldrin/dieldrin are summarized in order to provide a theoretical and practical basis for the bioremediation of aldrin/dieldrin-polluted environment.

An appraisal of data collection, analysis, and reporting adopted for water quality assessment: A case of Nigeria water quality research

The appropriate acquisition and processing of water quality data are crucial for water resource management. As such, published articles on water quality monitoring and assessment are meant to convey essential and reliable information to water quality experts, decision-makers, researchers, students, and the public. The implication is that such information must emanate from data obtained and analysed in an up-to-date, scientifically sound manner. Thus, inappropriate data analysis and reporting techniques could yield misleading results and mar the endeavours of achieving error-free conclusions. This study utilises the findings on water quality assessment in Nigeria over the last 20 years to reveal the likely trends in water quality research regarding data collection, data analysis, and reporting for physicochemical, bacteriological parameters, and trace organics. A total of 123 Web of Science and quartile ranked (Q1-Q4) published articles involving water quality assessment in Nigeria were analysed. Results indicated shortcomings in various aspects of data analysis and reporting. Consequently, we use simulated heatmaps and graphs to illustrate preferred ways of analysing, reporting, and visualising some regularly used descriptive and inferential statistics of water quality variables. Finally, we highlight alternative approaches to the customarily applied water quality assessment methods in Nigeria and emphasise other areas of deficiency that need attention for improved water quality research.

Indigenous Fish-Based Assessment of Genotoxic Potentials of the Helong Reservoir in Guangzhou, China

The present study was conducted to assess the genotoxic potential of water from the Helong Reservoir, which was designated as a strategic drinking water source by the Guangdong Provincial Government of China in October 2016. Four kinds of common indigenous fish samples (Labeo rohita, Cirrhinus molitorella, red tilapia, and Oreochromis niloticus) were collected at 6 sampling sites during the period from July to November 2020. Fish from the clean drinking water source of the upper reaches of the Liuxihe Reservoir in Guangzhou were collected as the control. Both the alkaline single cell gel electrophoresis assay and the micronucleus test were used to detect DNA damage and the micronucleus rate in erythrocytes of fish samples, respectively. The results indicated that there was a significant increase in comet tail length, Olive tail moment, and micronucleus rates of all fish samples compared with those of the control (p < 0.05). The order of sensitivity to DNA damage and micronucleus formation was Labeo rohita > Cirrhinus molitorella > red tilapia > Oreochromis niloticus. The results of the 2 kinds of experiments were in perfect agreement with each other. We conclude that there are obvious genotoxic effects from the water in the Helong Reservoir. As a strategic drinking water source, the safety of the Reservoir water quality should be considered. The local government should put the restoration of the Helong Reservoir water quality on the agenda as soon as possible. Environ Toxicol Chem 2021;40:1919-1927. © 2021 SETAC.

Pesticides contamination in the Thamirabarani, a perennial river in peninsular India: The first report on ecotoxicological and human health risk assessment

This study evaluates the distribution of pesticides and assesses the ecological and human health risks associated with pesticide residues concentration in the Thamirabarani River, the only perennial river in Tamil Nadu, India. Observed a variation in the pesticide concentration in the water (not detected (ND)-31.69 μg/L), sediments (ND-14.77 μg/kg), and fish (0.02-26.05 μg/kg). Endosulfan, aldrin, and endrin were the predominant organochlorine pesticides present in water, sediments, and fish. The average concentration of pesticides (except endosulfan) in water and sediments was found to be below the acceptable threshold as per the water and sediment quality guidelines, posing no ecological hazard to aquatic organisms. The calculated risk quotient and toxic unit (0.1 > TU/RQ ≤ 1) represent low-to-medium acute and chronic toxicity to the aquatic organisms inhabiting the river basin. The average concentration of pesticides in fish (Labeorohita) was also below the maximum residual limits set by the Codex Alimentarius Commission (CAC). However, the calculated daily intakes of endosulfan, aldrin, and endrin were above the CAC-acceptable daily intake guidelines. The human health risk assessment showed that children and adults exposed to pesticides in water and sediments through ingestion and dermal contact could have higher cancer risks (CR > 10^-4) than inhalation. This study recommends implementing effective and routine pollution management schemes to avoid pesticide threats to aquatic and human health.

Blood biomarkers of herbicide, insecticide, and fungicide toxicity to fish-a review

Pesticides are widely used in the world agriculture, and they may adversely affect non-target organisms, including fish. The present 2000-2019 literature review summarizes hematological and blood biochemical effects of various herbicides, insecticides, and fungicides in fish. The observed changes usually indicate anemia and inflammation, as well as hyperglycemia, hypoproteinemia, increase in cortisol concentration and activities of hepatic aminotransferases that are typical for intoxication and stress. Other changes that are also sometimes observed such as increase in red blood parameters indicate compensatory response. The often-noted symptoms of immunosuppression show an adverse effect of pesticides on immune system and possible immunosuppression. Pathophysiological changes in fish induced by pesticides depend on many factors, such as active compound and its concentration, exposure duration, fish species, environmental conditions, etc. Hematological and blood biochemical parameters appear to be useful biomarkers for evaluation of physiological state of fish exposed to pesticides; however, they are not specific markers of intoxication.

Probabilistic risk assessment and spatial distribution of potentially toxic elements in groundwater sources in Southwestern Nigeria

The study investigated the concentration of potentially toxic heavy metals (PTHM) in groundwater sources (hand-dug wells and boreholes), spatial distribution, source apportionment, and health risk impact on local inhabitants in Ogun state. One hundred and eight water samples from 36 locations were analysed for Cr, Ni, Pb, Fe, Mn, Mg, Ca and Al. Mean values of 0.013, 0.003, 0.010, 0.088, 0.004 and 3.906 mg/L were obtained for Pb, Cr, Ni, Fe, Mn, and Al respectively at Iju district. Meanwhile, the average values of Pb, Ni, Fe, Mn, and Al concentrations at Atan district were 0.008, 0.0023, 0.011, 0.003, and 1.319 mg/L respectively. Results also revealed that the 44.4% and 11.13% of the borehole and well-water samples surpassed the World Health Organization limits for Pb at Atan. In Iju, the concentration of Pb and Al were relatively high, exceeding the stipulated standard in 100% of the samples. The Multivariate statistical analysis employed produced principal factors that accounted for 78.674% and 86.753% of the variance at Atan and Iju region respectively. Based on this, PTHM were traced to geogenic sources (weathering, dissolution, leaching) and anthropogenic emissions from industrial activities. In addition, the hazard quotient values obtained from the health risk assessment identified potential non-carcinogenic risk due to Pb via ingestion route. Ni was found to have high carcinogenic risk on adult and children, having exceeded the threshold limit. The outcome of the carcinogenic risk assessment revealed that 88.67% (for adults) and 1.12% (for children) of the cancer risk values surpassed the specified limits at Iju, whereas the cancer risk values were considerably lesser at Atan. In conclusion, the report of this study should serve as a beacon that will spark up strategic planning, comprehensive water resource management, and extensive treatment schemes in order to address the health complications linked with environmental pollution.