Occurrence, profile and spatial distribution of organochlorines pesticides in soil of Nepal: Implication for source apportionment and health risk assessment

Organochlorine pesticide contamination of soils and dust from an urban environment in the Niger Delta of Nigeria

The concentrations, sources, and risk of twenty organochlorine pesticides (OCPs) in soils and dusts from a typical urban setting in the Niger Delta of Nigeria were examined. The Σ20 OCP concentrations (ng g-1) varied from 4.49 to 150 with an average value of 32.6 for soil, 4.67 to 21.5 with an average of 11.7 for indoor dust, and 1.6 to 96.7 with an average value of 23.5 for outdoor dust. The Σ20 OCP concentrations in these media were in the order: soil > outdoor dust > indoor dust, which was in contrast with the order of the detection frequency, i.e., indoor dust (95 to 100 %) > soil (60 to 90 %) > outdoor dust (30 to 80 %). The concentrations of the different OCP classes in these media followed the order: aldrin + dieldrin + endrin and its isomers (Drins) > chlordanes > dichlorodiphenyltrichloroethane (DDTs) > hexachlorocyclohexane (HCHs) > endosulfans for outdoor dust and soil, while that of the indoor dust followed the order: Drins > chlordanes > endosulfans > DDTs > HCHs. The cancer risk values for human exposure to OCPs in these sites exceeded 10-6 which indicates possible carcinogenic risks. The sources of OCPs in these media reflected both past use and recent inputs.

Analysis of nationwide soil pesticide pollution: Insights from China

China is a typical agricultural country that heavily relies on pesticides. Some pesticides can remain in the soil after application and thus pose a significant threat to human health. In order to characterize the status and hazards of nationwide soil contamination, this study extracted concentration data from published literature and analyzed them by a scoring approach, standard comparison and health risk assessment. For the soil pollution score, northern regions got the highest values, such as Henan (0.63), Liaoning (0.55), Heilongjiang (0.54) and Jilin (0.53), which implies high soil pesticide residues in these provinces. In contrast, Qinghai (-0.77), Guizhou (-0.64) and Tibet (-0.63) had lower scores. China's soil pesticide standards cover only 16 pesticides, and these pesticide concentrations were all below the corresponding standards. Direct exposure to soil pesticides in this study generally posed a negligible risk to children. Furthermore, pesticide dissipation and usage intensity in each province were analyzed as they were possible influences on pollution. The result showed that soil in the northern regions could accumulate more pesticides than those in the southern regions, and this geographic pattern was basically consistent with the distribution of soil pollution. However, the relationship between agricultural activities and soil pollution was less well characterized. It is recommended to establish a long-term monitoring database for pesticides and include more pesticides in regulatory frameworks. Additionally, efforts to accelerate pesticide degradation and shift the planting structure to reduce pesticide usage can help alleviate the pressure on soil from pesticides. This study can serve as a critical reference for policymakers and stakeholders in the field of agriculture.

Analytic and In Silico Methods to Understand the Interactions between Dinotefuran and Haemoglobin

This work lies in the growing concern over the potential impacts of pesticides on human health and the environment. Pesticides are extensively used to protect crops and control pests, but their interaction with essential biomolecules like haemoglobin (Hb) remains poorly understood. Spectrofluorometric, electrochemical, and in silico investigations have been chosen as potential methods to delve into this issue, as they offer valuable insights into the molecular-level interactions between pesticides and haemoglobin. The research aims to address the gaps in knowledge and contribute to developing safer and more sustainable pesticide practices. The interaction was studied by spectroscopic techniques (UV-Visible & Fluorescence), in silico studies (molecular docking & molecular dynamics simulations) and electrochemical techniques (cyclic voltammetry and tafel). The studies showed effective binding of dinotefuran with the Hb which will cause toxicity to human. The formation of a stable molecular complex between ofloxacin and Haemoglobin was shown via molecular docking and the binding energy was found to be -5.37 kcal/mol. Further, molecular dynamics simulations provide an insight for the stability of the complex (Hb-dinotefuran) for a span of 250 ns with a binding free energy of -53.627 kJ/mol. Further, cyclic voltammetry and tafel studies show the interaction of dinotefuran with Hb effectively.

Concentration and non-dietary human health risk assessment of pesticide residues in soil of farms in Golestan province, Iran

Detection of pesticide residues in soil samples was conducted using UHPLC-MS/MS. Non-dietary health risk assessment was conducted using calculate chronic daily intake (CDI) from ingestion, inhalation and dermal contact pathways and following non-carcinogenic and carcinogenic risks in the adults and adolescent. The rank order of pesticide in soil based on their concentration was malathion (0.082 mg kg-1)> cyproconazole (0.019 mg kg-1)> propargite (0.018 mg kg-1)> butachlor (0.016 mg kg-1) > chlorpyrifos (0.0067 mg kg-1)> diazinon (0.0014 mg kg-1)> imidacloprid (0.0007 mg kg-1). Hazard index (HI) values obtained of exposure to pesticides in soil in adults and adolescent were 0.0012 and 0.0035, respectively. Hence, exposed population are at the acceptable range of non-carcinogenic risk (HI < 1). Cancer risk (CR) values due to propargite in soil via ingestion pathway in adults and adolescent were 2.03E-09 and 2.08E-09, respectively; therefore, carcinogenic risk due to the exposure to pesticide contaminated soil was safe range (CR < 1E-06).

First surveillance of pesticides in soils of the perimeter of Tadla, a Moroccan sugar beet intensive area

With the long-term application of pesticides on sugar beet farms in the irrigated perimeter of Tadla in Morocco for over 50 years, pesticide monitoring is necessary to assess soil health. The objective of our study was to monitor multiple pesticide residues in topsoil samples collected from post-harvest sugar beet fields and verify their migration to deep soil layers. Topsoil and deep soil samples were collected from arbitrarily selected sugar beet fields in the IPT. In this study, a target-screening method was applied. All target pesticides were detected in soil samples, with tefluthrin being the most frequently detected pesticide. The residue with the highest concentration in soil samples was DDE. All the soil samples contained a mixture of pesticide residues, with a maximum of 13 residues per sample. The total pesticide content decreased toward more profound layers of soil, except in one field where it reached a concentration of 348 µg/kg at the deeper soil layer. For pesticides detected at the three soil depths, only tefluthrin concentration increased in the deep soil layer. The results provide comprehensive and precise information on the pesticide residue status in sugar beet soils warning against the multiple risks that this contamination can cause. This study indicates the need of regular monitoring of pesticides over a large area of the perimeter to enable decision-makers to pronounce the impacts of the extension and intensification of sugar beet cultivation at the irrigated perimeter of Tadla.

Distribution, Sources, and Risk Assessment of Organochlorine Pesticides in Water from Beiluo River, Loess Plateau, China

The Loess Plateau has been a focus of public discussion and environmental concerns over the past three decades. In this study, in order to investigate the effect of OCP pollution in water of the Beiluo River, concentrations of 25 OCPs at 17 locations in the water were examined. The results showed that the concentration of ∑OCPs in the water ranged from 1.76 to 32.57 ng L^-1, with an average concentration of 7.23 ng L^-1. Compared with other basins in China and abroad, the OCP content in the Beiluo River was at a medium level. Hexachlorocyclohexane (HCH) pollution in the Beiluo River was mainly from the mixed input of lindane and technical HCHs. Dichlorodiphenyltrichloroethane (DDT) pollution was mainly from the mixed input of technical DDTs and dicofol. Most of the OCP pollution came from historical residues. The risk assessment results showed that hexachlorobenzene (HCB) and endosulfan had high ecological risks in the middle and lower reaches of the Beiluo River. Most residual OCPs were not sufficient to pose carcinogenic and non-carcinogenic health risks to humans. The results of this study can provide a reference for OCP prevention and control and watershed environmental management.

National-scale monitoring of historic used organochlorine pesticides (OCPs) and current used pesticides (CUPs) in Chinese surface soil: Old topic and new story

Along with the restriction and prohibition of historic used organochlorine pesticides (OCPs), current used pesticides (CUPs) were widely used as alternatives. In order to investigate the pollution characteristics of pesticides, the levels and spatial distributions of OCPs and CUPs in 154 surface soil across China were comprehensively compared. Totally, 107 target pesticides were screened, and 20 OCPs and 34 CUPs were detected. The numbers of co-occurred pesticides in single soil sample were from 17 to 36 indicating the diversity and complexity of pesticides pollution. The concentrations of OCPs in urban soils were higher than rural soils, while rural > urban for CUPs. Furthermore, obviously different spatial distribution patterns were found for OCPs and CUPs. For OCPs, the secondary distribution pattern was dominant. For CUPs, the primary distribution pattern was obviously observed due to their current extensive usage. In addition, higher concentrations of both CUPs and OCPs were accumulated in the Northeast China Plain due to long-range atmospheric transport and deposition. Along with the old topic of OCPs, the study pointed out the preliminary understanding of CUPs pollution characteristic in surface soil of China, which provided a new story with the deep understanding of their environmental fate in both China and the world.

Concentrations, distribution, and risk assessment of endosulfan residues in the cotton fields of northern Xinjiang, China

In the current study, surface soil samples were collected from cotton fields in Shawan and Shihezi areas in northern Xinjiang and tested for endosulfan residues using gas chromatography-mass spectrometry. Results showed endosulfan sulfate was the predominant compound in the surface soil studied, followed by β-endosulfan and α-endosulfan with detection rates of 86.9%, 55.7%, and 49.2%, respectively, for the 61 soil samples collected. The average concentrations of endosulfan sulfate, α-endosulfan, and β-endosulfan were 0.743, 0.166, and 0.073 µg/kg, respectively. The ratios of α-/β-endosulfan were below 2.33 in all samples tested, suggesting no new endosulfan was added to the soil and the presence of endosulfan residues in this region was due to historical application in the past. According to the health risk assessment model recommended by the USA Environmental Protection Agency, the health risk of endosulfan residues in the studied area was low, and the maximum values of noncarcinogenic risks for children and adults were 2.30 × 10^-5 and 2.70 × 10^-6, respectively. Folsomia candida was the most sensitive organism to total endosulfan residues, with 38% of the total sampling sites classified as high risk. For earthworms, the proportion of high risk site was 13%. Lactuca sativa was the most tolerant organism to ∑ESs, with all sampling sites identified as negligible risk. This study provided current status of endosulfan residues and related risk in cotton fields, which could be used to support decision makers to prepare relevant regulations.

A nationwide survey on the endosulfan residues in Chinese cotton field soil: Occurrence, trend, and ecological risk

The nationwide occurrence of endosulfan residues in cotton fields has not yet been investigated. Therefore, in this study, 202 surface soil samples from 27 cities were collected from cotton fields in 8 major cotton-planting provinces of China, covering more than 97% of the national cotton sown area. The results showed that endosulfan residues were detected in cotton fields throughout the country. The main type of residue found was endosulfan sulfate (ES-sulfate), followed by β-endosulfan and α-endosulfan, with average concentrations of 0.475, 0.129, and 0.048 μg/kg, respectively. Significant spatial variations in the endosulfan residues was noted, and the highest concentration of endosulfan residues was observed in the northwest inland cotton-growing area, followed by that in the Yellow River basin and Yangtze River basin cotton-growing areas. The endosulfan residues showed significant positive correlations with soil organic matter and soil clay contents. The α/β endosulfan ratio was determined to be in the range of 0.02-1.20, indicating that endosulfan residues originated from the endosulfan application performed in historical cotton cultivation efforts. Together with the literature data, the concentrations of α-endosulfan and β-endosulfan residues peaked in 2015 and 2017, respectively, and showed an overall decreasing trend from 2002 to 2021. The results of the ecological risk assessment suggested that Folsomia candida was most sensitive to endosulfan residues, with 20.8% of the sites presenting a high risk. However, in general, the soil ecological risk of cotton fields across the country was low. Our study demonstrated that China has achieved promising results in controlling the use and pollution of endosulfan, especially after 2014.

Occurrence of persistent organic pollutants (POPs) in the atmosphere of South Korea: A review

Numerous studies found the presence of persistent organic pollutants (POPs) in various environmental compartments, including air, water, and soil. POPs have been discovered in various industrial and agricultural products with severe environmental and human health consequences. According to the data, South Korea is a hotspot for POP pollution in the southern part of Asia; hence, South Korea has implemented the Stockholm Convention's National Implementation Plan (NIP) to address this worldwide issue. The purpose of this review is to assess the distribution pattern of POPs pollution in South Korea's atmosphere. According to findings, PAHs, PCBs, BFRs, and PBDEs significantly polluted the atmosphere of South Korea; however, assessing their exposure nationwide is difficult due to a shortage of data. The POPs temporal trend and meta-analysis disclosed no proof of a decrease in PAHs and BFRs residues in the atmosphere. However, POP pollution in South Korea tends to decrease compared to contamination levels in neighboring countries like Japan and China.

Environmental monitoring and potential health risk assessment from Pymetrozine exposure among communities in typical rice-growing areas of China

Pymetrozine is one of the most commonly used insecticides in China. This study was conducted to analyse Pymetrozine's potential exposures through various environmental routes beyond the treatment areas. The aim was to estimate the potential health risk for communities due to non-dietary exposures to Pymetrozine in soil and paddy water. Data on registration of pesticides in China, government reports, questionnaires, interviews and literature reviews as well as toxicological health investigations were evaluated to determine the hazard and dose-response characteristics of Pymetrozine. These were based on the US EPA exposure and human health risk assessment methods and exposure data from soil and paddy water samples collected between 10 and 20 m around the resident's location. The exposure doses from dermal contact through soil and paddy water were estimated. The potential cancer risk from the following exposure routes was evaluated: ingestion through soil; dermal contact exposure through soil; dermal contact exposure through paddy water. The potential total cancer risk for residents was estimated to be less than 1 × 10^-6. These were relatively low and within the acceptable risk levels. The potential hazard quotient (HQ) from acute and lifetime exposure by dermal contact through paddy water and soil and acute and lifetime exposure by soil ingestion for residents was less than 1, indicating an acceptable risk level. This study suggested that there were negligible cancer risk and non-cancer risks based on ingestion and dermal contact routes of exposure to residents.

Organochlorine pesticides and polychlorinated biphenyls in high mountain lakes, Mexico

Pollution levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in the El Sol and the La Luna alpine lakes. The lakes are located in central Mexico, in the crater of the Nevado de Toluca volcano. The El Sol and the La Luna lakes are extremely relevant in Mexico and in the world because they are recognized as pristine regions and environmental reservoirs. Samples of atmospheric aerosol, sediment, plankton, and Tubifex tubifex (sludge worm) were collected at three different sample locations for three years (2017, 2018, and 2019) at three different times of year, meaning that the weather conditions at the time of sampling were different. Pollutants were analysed by gas chromatography-mass spectrometry with negative chemical ionisation (GC-MS/NCI). Endosulfan was the most frequent and abundant pollutant, showing the highest peaks of all. Atmospheric aerosol revealed Σ₂ = 45 pg/m³, including α and β, while sediment lakes displayed α, β and endosulfan sulfate as Σ₃ = 1963 pg/g, whereas plankton and Tubifex tubifex showed Σ₂ = 576 pg/g and 540 pg/g for α and β respectively. Results of endosulfan ratios (α/β) and (α-β/endosulfan sulfate) suggest that both fresh and old discharges continue to arrive at the lakes. This study shows for the first time the pollution levels of OCP and PCB in high mountain lakes in Mexico. These results that must be considered by policy makers to mitigate their use in the various productive activities of the region.

Exposure Routes and Health Risks Associated with Pesticide Application

Pesticides play an important role in agricultural development. However, pesticide application can result in both acute and chronic human toxicities, and the adverse effects of pesticides on the environment and human health remain a serious problem. There is therefore a need to discuss the application methods for pesticides, the routes of pesticide exposure, and the health risks posed by pesticide application. The health problems related to pesticide application and exposure in developing countries are of particular concern. The purpose of this paper is to provide scientific information for policymakers in order to allow the development of proper pesticide application technics and methods to minimize pesticide exposure and the adverse health effects on both applicators and communities. Studies indicate that there are four main pesticide application methods, including hydraulic spraying, backpack spraying, basal trunk spraying, and aerial spraying. Pesticide application methods are mainly selected by considering the habits of target pests, the characteristics of target sites, and the properties of pesticides. Humans are directly exposed to pesticides in occupational, agricultural, and household activities and are indirectly exposed to pesticides via environmental media, including air, water, soil, and food. Human exposure to pesticides occurs mainly through dermal, oral, and respiratory routes. People who are directly and/or indirectly exposed to pesticides may contract acute toxicity effects and chronic diseases. Although no segment of the general population is completely protected against exposure to pesticides and their potentially serious health effects, a disproportionate burden is shouldered by people in developing countries. Both deterministic and probabilistic human health risk assessments have their advantages and disadvantages and both types of methods should be comprehensively implemented in research on exposure and human health risk assessment. Equipment for appropriate pesticide application is important for application efficiency to minimize the loss of spray solution as well as reduce pesticide residuals in the environment and adverse human health effects due to over-spraying and residues. Policymakers should implement various useful measures, such as integrated pest management (IPM) laws that prohibit the use of pesticides with high risks and the development of a national implementation plan (NIP) to reduce the adverse effects of pesticides on the environment and on human health.

Organochlorine pesticides in riparian soils and sediments of the middle reach of the Huaihe River: A traditional agricultural area in China

Distributions, souces, ecological risks as well as environmental behaviors of 20 organochlorine pesticides (OCPs) in riparian soils and sediments of the middle reach of the Huaihe River, a traditional agricultural area of China, were investigated. ∑OCPs in riparian soils and sediments were 1.8-63 ng g^-1 (mean = 19 ± 12 ng g^-1) and 1.2-9.9 ng g^-1 (mean = 3.0 ± 1.8 ng g^-1), respectively. HCHs were the dominant OCPs in both soils and sediments, while high concentrations of ∑HEPTs and ∑DDTs were also detected in some soils and sediments. No correlations were found between concentrations of OCPs and organic matter contents in both soils and sediments. Based on the source analysis, most OCPs in the riparian soils were mainly from historical residues, such as historical usage of technical HCH, DDT, chlordane and endosulfan. OCPs in sediments were influenced not only by surface runoff by also by other factors, e.g. in-situ contamination (DDT-containing antifouling paints in ships) and/or hydraulic transport from some tributaries. Some never-used OCPs, such as heptachlor and aldrin, were widely detected in soils and sediments. This might be attributed to some unknown usages or long-range atmospheric transport of them from other source regions. Ecological risk analysis suggested that DDTs and HCHs in soils would not lead to an adverse effect on soil ecological environment as well as agricultural production, and OCP residues in sediments also would not pose a threat to the sediment-dwelling organisms.

Ultrasound-assisted QuEChERS-based extraction using EDTA for determination of currently-used pesticides at trace levels in soil

It is essential to monitor pesticides in soils as their presence at trace levels and their bioavailability can induce adverse effects on soil's ecosystems, animals, and human health. In this study, we developed an analytical method for the quantification of traces of multi-class pesticides in soil using liquid chromatography-tandem mass spectrometry. In this way, 31 pesticides were selected, including 12 herbicides, 9 insecticides, and 10 fungicides. Two extraction techniques were first evaluated, namely, the pressurized liquid extraction and the QuEChERS procedure. The latest one was finally selected and optimized, allowing extraction recoveries of 55 to 118%. The role of the chelating agent EDTA, which binds preferentially to soil cations that complex some pesticides, was highlighted. Coupled with liquid chromatography-tandem mass spectrometry, the procedure displayed very high sensitivity, with limits of quantification (LOQ) in the range 0.01-5.5 ng/g. A good linearity (R2 > 0.992) was observed over two orders of magnitude (LOQ-100 [Formula: see text] LOQ) with good accuracy (80-120%) for all compounds except the two pyrethroids lambda-cyhalothrin and tau-fluvalinate (accuracy comprised between 50 and 175%) and the cyclohexanedione cycloxydim (accuracy < 35%). Good repeatability and reproducibility were also achieved. The method was finally successfully applied to 12 soil samples collected from 3 land-use types. Among the 31-targeted pesticides, 24 were detected at least once, with concentration levels varying from LOQ to 722 ng/g. Many values were below 0.5 ng/g, indicating that the developed method could provide new knowledge on the extremely low residual contents of some pesticides.

Health Risk Assessment for the Residential Area Adjacent to a Former Chemical Plant

A health risk assessment was carried out for the residents of Łęgnowo-Wieś settlement adjacent to a former Zachem Chemical Plant, Bydgoszcz, Poland. Due to the unique Zachem site history and contamination profile, an innovative strategy for soil sampling and contaminant selection was applied. The novelty in the developed strategy consisted of selecting substances for the health risk assessment, taking into consideration the location and boundaries of the groundwater contamination plumes in relation to contamination sources. This allowed limiting the number of the analysed contaminants. The risk assessment focused on the surface soil of a residential area, which was divided into 20 sampling sectors and 6 backyards with wells from which water was used for watering edible plants. A total of 80 inorganic and organic substances were determined, including metals, phenol, aniline, BTEX, diphenyl sulphone, chloroaniline, epichlorohydrin, hydroxybiphenyl, nitrobenzene, octylphenols, toluenediamine, toluidine, 16 polycyclic aromatic hydrocarbons, tetrachloroethylene and trichloroethylene. For the health risk assessment, the United States Environmental Protection Agency’s deterministic method was applied. This applies conservative assumptions to obtain risk estimates protective for most of the potential receptors. Three exposure pathways were analysed: (1) incidental soil ingestion, (2) dermal contact with soil and (3) inhalation of fugitive soil particles and volatiles. In all sampling sectors and backyards, the total non-cancer risks (hazard index) were significantly lower than the acceptable level of 1. The acceptable cancer risk level for the single carcinogen of 1 × 10⁻⁵ was only insignificantly exceeded in the case of benzo(a)pyrene in three sectors and one backyard. The total cancer risks were lower than the acceptable level of 1 × 10⁻⁴ in all sampling sectors and all backyards. The findings show that the soil in the entire residential area is safe for the residents’ health and no remedial actions are required. However, since not all possible exposure pathways were analysed in this study, further research focused on assessing the health risk resulting from the consumption of locally grown food is strongly recommended.

Modeling pesticides in global surface soils: Exploring relationships between continuous and discrete emission patterns

Continuous pesticide emission at constant rate does not occur in reality, but can be a useful and simple concept in modeling studies. To explore the relationship between continuous and discrete emission patterns, we introduced a simple equivalent approach based on a comparison of simulated surface soil pesticide concentrations. The simulated results indicate that, at high soil pesticide dissipation rates and low emission frequencies, the average concentrations under the continuous and discrete emission scenarios were very similar. We demonstrated that the continuous emission model that used the simple average method to calculate the emission rate always overestimated the simulated pesticide concentrations in the surface soil compared to the discrete emission model when using a one-year period based on agricultural practices. In addition, we incorporated the equivalent approach into the USEtox model (a screening-level tool), which can approximate the average pesticide concentrations in surface soil using the time-integrated fate factors at different emission frequencies. The results indicate that the continuous-emission simulations agree with the discrete emission for at least 90% of the selected pesticides based on annual or semi-annual emission patterns. Further studies into other topics, such as random emission patterns and simulation periods, are required to improve the model. Nevertheless, the equivalent approach presented in this study can aid in transforming discrete emission patterns into continuous-emission-based models and improve surface soil pesticide management.

Gridded emission inventory of organophosphorus flame retardants in China and inventory validation

The bioaccumulation and adverse effects of organophosphorus flame retardants (OPFRs) on human health have become a global concern. China produces the largest amount of OPFRs globally and has the highest global market share. However, little is known about its emission level and environmental cycling, thereby causing uncertainties in the assessment of the environmental and health impacts of OPFRs. We developed a gridded annual OPFRs emission inventory at 1/4° longitude by 1/4° latitude resolution over China from 2014 to 2018. The results show that the annual OPFRs emissions increased from approximately 670 tons/yr in 2014 to 1000 tons/yr in 2018 in China. Higher OPFR emissions were identified in Jiangxi, Shandong, Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), and Pearl River Delta (PRD). In total, 2400 tons of OPFRs were released into the atmosphere during the multi-year period, in which production accounting for 56.6% of total OPFR emissions in China. An atmospheric transport model, the Canadian Model for Environmental Transport of Organochlorine Pesticides (CanMETOP), was employed to verify the gridded emission inventory and elucidate the atmospheric environmental fate of OPFRs. Modeled OPFRs in the air and soil agreed reasonably well with observed data, suggesting that the developed inventory was, to a large extent, reliable. The modeled atmospheric and surface soil concentrations of OPFRs across China ranged from 0 to 119 ng/m³ and 0 to 428 ng/g, respectively. East China is subjected to more intense OPFR contamination than the rest of the country. The results provide a valuable dataset and assessment of OPFRs, which may aid policy-makers and the scientific community in developing emission control strategies and evaluating the health and environmental consequences of OPFRs in China.

Ecological risk assessment of pesticide residues in soils from vegetable production areas: A case study in S-Nepal

Pesticides pose a serious risk to ecosystems. In this study, we used European Food Safety Authority methods, such as risk quotient (RQ) and toxicity exposure ratios (TER), to assess the potential ecological risks of 15 pesticide residues detected in agricultural soils in the Gaidahawa Rural Municipality of Nepal. The mean and maximum concentrations of the detected pesticide residues in the soil were used for risk characterization related to soil organisms. RQ_mean, TER_mean and RQ_maximum, TER_maximum were used to determine general and the worst-case scenarios, respectively. Of all the detected pesticides in soils, the no observed effect concentration (NOEC) for 27% of the pesticides was not available in literature for the tested soil organisms and their TER and RQ could not be calculated. RQ threshold value of ≥1 indicates high risk for organisms. Similarly, TER threshold value of ≥5, which is acceptable trigger point value for chronic exposure, indicates an acceptable risk. The results showed that the worst-case scenario (RQ_maximum) indicated a high risk for soil organisms from chlorpyrifos [RQ_maximum > 9 at depths (cm) of 0-5, 15-20 and 35-40 soil layer]; imidacloprid (1.78 in the 35-40 cm soil layer) and profenofos (3.37 in the 0-5 cm and 1.09 in the 35-40 cm soil layer). Likewise, for all the soil depths, the calculated TER for both the general and worst-case scenarios for chlorpyrifos ranged from 0.37 to 3.22, indicating chronic toxicity to F. candida. Furthermore, the risk of organophosphate pesticides for soil organisms in the sampling sites was mainly due to chlorpyrifos, except for two study sites where the risk was from profenofos. Ecological risk assessment (EcoRA) of the pesticide use in the study area indicated that the EFSA soil organisms were at risk at some of the localities where farmers practiced conventional farming.

Spatiotemporal distribution and human health risk assessment of potential toxic species in soils of urban and surrounding crop fields from an agricultural area, Córdoba, Argentina

The spatiotemporal distribution of potentially toxic species was studied in the topsoil of parks, playgrounds, and surrounding crop fields of Marcos Juarez City in Córdoba province, Argentina. The content of available metals and of some pesticides used in the region was determined. The mean values of available metal concentrations in all samples, expressed in mg kg^-1, were 7.99 ± 6.58, 0.89 ± 0.71, 0.35 ± 0.26, and 1.50 ± 1.40 for Pb, Cr, Cd, and Ni, respectively. Pearson's correlation coefficients, coefficient of variation (%), and principal component analysis were used to explore whether variations in metal content were associated with anthropogenic factors. Agrochemicals such as lindane, chlorobenzilate, endosulfan, endrin, permethrin, and chlorpyrifos were found in crop field soil samples. In turn, chlorothalonil, chlordanes, methoxychlor, DDT, permethrin, and chlorpyrifos were detected in park and playground soil samples. The degree of pollution with possible effects on environmental health was evaluated using the Nemerow integrated pollution index (NIPI) and the modified degree of contamination (mCd). In some campaigns, the values obtained from crop fields ranged from low to high pollution levels during periods of agrochemical application. Noteworthy, in periods of low agrochemical application in crop fields, a high level of pollution was observed in parks and playgrounds. For children, the hazard index (HI) values were higher than the threshold value of 1, suggesting a potential health risk. This study provides valuable information regarding land management practices and highlights the importance of monitoring and implementing policies to reduce human health risks.

Health risk assessment of hexachlorocyclohexane in soil, water and plants in the agricultural area of Potohar region, Punjab, Pakistan

In this study analysis of soil, water and plant residue samples is presented to evaluate the contamination levels and possible health risks. Hexachlorocyclohexane (HCH) is a persistent organic pollutant used as a pesticide in agricultural sector for pest control in order to obtain higher productivity. For analysis soil, water and crop residue samples were collected from different agricultural areas of the northern Punjab region of Pakistan. The investigation of the samples shows significant levels of HCH residues in all types of samples. Gas chromatography-mass spectrometry analysis was used to assess the higher residue levels of HCH in the samples. The concentration of HCH residues detected in samples ranged from 2.43 to 8.88 µg/g in soil, nd -5.87 µg/l in water and nd - 4.87 µg/g in plants. The presence of HCH residues in soil, water and plant samples was beyond the recommended quality guidelines. Human health risk was evaluated for cancer and non-cancer risks through dietary and non-dietary exposure routes. The hazard index was HI > 1 in children and HI < 1 in adults, while the non-dietary incremental lifetime cancer risks (ILCR) were beyond the internationally acceptable limit of 1 × 10^-5. Hence, results of the present investigation concluded the presence of high levels of HCH residues in samples and pose high health risk to the inhabitants. These findings are alarming and apprise the concerned departments for the remediation of contamination and proper implementation of environmental laws in the area.

Rapid transport of organochlorine pesticides (OCPs) in multimedia environment from karst area

Karst groundwater is crucial, but particularly vulnerable to contaminants. Anthropologically derived pollutants on the surface-environment in karst areas could easily and rapidly enter groundwater through highly developed transmissible structures and threaten water safety. To investigate such transport, we analyzed 24 organochlorine pesticides (OCPs) in the multimedia environment from the Zigui karst area of China, where agriculture is the predominant human activity. OCPs were frequently detected with the total OCP concentrations ranged from 228 to 7970 pg/g, 300 to 32,200 pg/L, 318 to 2250 pg/L, 149 to 2760 pg/g, and 752 to 12,000 pg/g in the soil, spring water, river water, spring sediment, and river sediment, respectively. HCB and p,p'-DDT were the most dominant OCP species. Isomeric and metabolic ratios indicated fresh inputs of Lindane, technical DDT, and Aldrin, although they have been banned in China. The spatial distributions, correlation analysis, and regression analysis suggested rapid OCP transport from the soil to the spring water, and from the soil and spring water to river water. OCPs in the soil and springs explained 92.3% and 89.0% of those in the spring water and river water, respectively. The solid transport with the fast-moving water was predominant for OCPs in sediments. Highly dynamic water systems and rapid OCP transport in the intro- and inter-medium suggested by our results substantiate the groundwater's vulnerability in karst areas. More studies on levels and transport of organic contaminants in karst systems and policy for protecting the karst groundwater are urgently required to control contaminant sources and ensure groundwater sustainability, since the karst water resources may suffer a potentially bleak future consisted of the decreased groundwater quantity and low water quality.

Health risks of exposure to soil-borne dichlorodiphenyltrichloroethanes (DDTs): A preliminary probabilistic assessment and spatial visualization

Residues of dichlorodiphenyltrichloroethane and its metabolites (DDTs) in soils continue to severely threaten and endanger human health. This present study comprehensively interprets the health risks associated with exposure to soil-borne DDTs and also identifies the spatial visualization of risks at a large regional scale in Fujian, China. There was significant spatial variability of human risk across the region, while levels of health risk displayed a significant positive correlation with population density (p < 0.05). High risk levels occurred mostly in the coastal areas in northeastern Fujian, with additional hotspots in inland areas. The highest total incremental lifetime cancer risks (ILCRs) occurred in Sanming, reaching up to 9.52 × 10^-5, 3.27 × 10^-5, and 1.76 × 10^-4 for children, teens, and adults, respectively. Further, the highest hazard index (HI) value was observed in Fuzhou, reaching up to 6.09, 3.84, and 2.37, respectively. The 95% confidence interval of data regarding ILCRs exceeded the recognized safe threshold, whereas the HI has been deemed accepted. Adults were identified as the most susceptible population in terms of cancer risks, with o,p'-DDT being the primary contributor of ILCRs. Moreover, children were showed to be the most vulnerable in terms of non-cancer risks, with p,p'-DDD being the main contributor of HI. Food ingestion appeared to be the dominant exposure pathway, for both cancer and non-cancer risks. The concentration of DDTs (C_soil) and exposure duration (ED) also greatly influenced the risk, together contributing to over 99% of the ILCRs and HI.

Spatial occurrence and composition profile of organophosphate esters (OPEs) in farmland soils from different regions of China: Implications for human exposure

The environmental load of organophosphate ester (OPE) flame retardants has caused a series of problems due to their extensive use. The soil matrix, as an ultimate sink for organic pollution, plays a vital part in the fate of OPEs in the environment. In this study, the spatial occurrence, composition profile and health risk of 13 OPE species in farmland soils from four provinces of China were characterized. Excluding tris(2,3-dibromopropyl) phosphate (TDBPP) and ethylhexyl diphenyl phosphate (EHDPP), the remaining eleven OPEs had a high detection frequency (DF) ranging from 60% to 100%. The range of total OPE (ΣOPE) concentrations were 62.3-394 ng/g dry weight (dw), with a median of 228 ng/g dw. Among these OPEs, tris(2-ethylhexyl) phosphate (TEHP) with a median of 143 ng/g dw) was the predominant species, followed by tricresyl phosphate (TCP; median of 20.1 ng/g dw) and tris(2-chloroethyl) phosphate (TCEP; median of 17.9 ng/g dw). In terms of geographical distribution, significantly lower OPEs levels were found in samples from Heilongjiang (159 ± 47.0 ng/g dw) than in those of Guangxi (264 ± 66.0 ng/g dw), Henan (252 ± 74.5 ng/g dw) and Hubei (242 ± 52.8 ng/g dw) provinces. Principal component analysis and Spearman's correlations were used to reveal potential sources of OPEs in the different provincial regions. Health risk exposure to OPEs in farmland soils was at an acceptable level (<1.20 × 10^-5 for non-carcinogenic risk to children as the most sensitive age group; and <6.47 × 10^-10 for carcinogenic risk to adults as the most sensitive age group) at the present detected concentrations. However, TCEP and TEHP, the predominant risk contributors, should be paid more attention.

Hexachlorocyclohexane toxicity in water bodies of Pakistan: challenges and possible reclamation technologies

Pakistan is an agro-economy country where hexachlorocyclohexane (HCH) pesticides are being used to improve crop productivity, as a result the risk of contamination of soil and sediment has been increased. HCH exhibits all the characteristics of persistent organic pollutants (POP), and was therefore added to the list of 'new POPs' in 2009. This review report revealed that the major rivers of Pakistan such as the Indus Basin, River Ravi, River Chenab and their tributaries all are contaminated with HCH and the highest residual concentration (4,090 ng/g) was detected in a pesticide burial ground in Hyderabad city. Major sources of HCH contamination were identified as agricultural runoff, discharge of untreated industrial effluents and surface runoff. In order to manage HCH pollution, various ex-situ and in-situ remediation techniques along with their merits and demerits are thoroughly reviewed. Among these, microbial bioremediation is a low cost, environment friendly, effective in-situ remediation technique for remediation of HCH. Overall, the information provided in this manuscript will provide a future reference to the scientific community and bridge the knowledge gap between HCH release in the environment and their mitigation through proper treatment methods.

The endangered African Great Ape: Pesticide residues in soil and plants consumed by Mountain Gorillas (Gorilla beringei) in Bwindi Impenetrable National Park, East Africa

Bwindi Impenetrable National Park situated southwest of Uganda is a biodiversity hotspot that is home to about half of the world's endangered mountain gorilla (Gorilla beringei). Given its ecological significance and mounting pressures from agricultural activities such as tea growing, continuous monitoring of the levels of chemical toxins like pesticides in the park and surrounding areas is needed for effective conservation strategies. Furthermore, persistent organochlorine pesticides (OCPs) like DDT were used in agricultural gardens and indoor spraying in Kanungu district between the 1950s and 80s. The focus of this study was to explore the possible exposure of mountain gorillas to OCPs and cypermethrin used by the farmers in the areas near the park. Data from our interviews revealed that glyphosate is the most widely used pesticide by the farmers in areas surrounding the park, followed by cypermethrin, and mancozeb. Samples of leaves from plants consumed by mountain gorillas along the forest edges of the park and surficial soils (15-20 cm depths) were collected from three sites (Ruhija, Nkuringo and Buhoma) and analysed for the presence of cypermethrin and OCPs residues. Concentrations of total (∑) DDTs and ∑endosulfans were up to 0.34 and 9.89 mg/kg dry weight (d.w), respectively in soil samples. Concentrations of ∑DDTs and ∑endosulfans in samples of leaves ranged from 0.67 to 1.38 mg/kg d.w (mean = 1.07 mg/kg d.w) and 0.9 to 2.71 mg/kg d.w (mean = 1.68 mg/kg d.w), respectively. Mean concentration of ∑DDTs in leaves exceeded the European pharmacopeia and United States pharmacopeia recommended maximum residue limit values for DDTs in medicinal plants (1.0 mg/kg). In addition, calculated hazard indices for silverbacks (36.35), females (57.54) and juveniles (77.04) suggested potential health risks to the mountain gorillas. o,p'-DDT/p,p'-DDT ratios (0.5-0.63) in samples of leaves confirmed recent input of dicofol-DDT type in Bwindi rainforest.

Occurrence and tissue distribution of organochlorinated compounds and polycyclic aromatic hydrocarbons in Magellanic penguins (Spheniscus magellanicus) from the southeastern coast of Brazil

Seabirds are suitable biomonitors for several persistent organic pollutants (POP), such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), although scarce studies of PAHs in seabirds are available, especially in South American populations. Therefore, this study aimed to assess OCPs, PCBs and PAHs, through gas chromatography-electron capture detector (GC-ECD) and gas chromatography-mass spectrometry (GC-MS) analyses, in liver (n = 9) and muscle tissue (n = 13) from juvenile Magellanic penguins (Spheniscus magellanicus) found stranded on the coast of Rio de Janeiro, Southeastern Brazil. DDT-related compounds were the most frequently detected OCP, and 4,4'-dichlorodiphenyldichloroethylene (DDE), the main DDT metabolite found in penguin tissues. OCP concentrations in liver were two-fold higher than in muscle tissues. Compound specific ratios identified recent exposure of penguins to some OCPs as well as evidence of legacy pollution associated with industrial sources. The predominant PCB congeners were PCB 8/5, PCB 138/160 and PCB 153/132, with concentrations ranging from <LOQ and 1500 ng g^-1 dry weight. This study comprises one of the few PAHs reports in penguin tissues, and, although most compounds were detected at very low levels or below the limit of quantitation (LOQ), the concentrations reported herein were up to 100-fold higher than in previous studies in penguins. Therefore, considering penguin vulnerability to marine oil spills during migration routes, further assessments are required in different tissues in order to assess potential environmental health risks to these sentinel species.

Nationwide levels and distribution of endosulfan in air, soil, water, and sediment in South Korea

We investigated the levels and distribution patterns of α- and β-endosulfan and endosulfan sulfate in air, soil, water, and sediment samples collected from the South Korean persistent organic pollutants (POPs) monitoring networks. In the air samples, the highest concentrations of the total (Σ₃) endosulfan (50.3-611 pg/m³, mean: 274 pg/m³) were observed during summer. Spearman analysis revealed a good correlation between agricultural land area and atmospheric concentrations of Σ₃ endosulfan except during winter. Regardless of the season, the ratio of the two isomers (α/β) was 3.6-4.9 in the air samples, higher than that observed in technical mixtures (2.0-2.3), possibly due to the higher volatility of α-endosulfan, compared to β-endosulfan. Concentrations of Σ₃ endosulfan in the soil samples (n.d.-13.4 ng/g, mean: 0.8 ng/g) were not significantly different except at some stations adjacent to large areas of farmland. The average levels of Σ₃ endosulfan in the water and sediment samples were 2.1 ng/L and 0.1 ng/g dw, respectively. In analyzing the four largest rivers, it was observed that a few water stations during spring and fall and sediment stations in fall had high concentrations of the two isomers and endosulfan sulfate, particularly around the Yeoungsan and Nakdong Rivers near large areas of agricultural land. Endosulfan sulfate was dominant at most water and sediment sampling stations. This study demonstrates that the endosulfan found in most environmental compartments most probably derives from agricultural areas despite its ban as a pesticide. On the other hand, given that it was also detected in industrial and urban areas, in which pesticide application does not occur, it can be conjectured that endosulfan is aerially transported at higher temperatures and continuously circulates within the environment.

Spatial distribution and compositional profiles of organochlorine pesticides in the surface soil from the agricultural, coastal and backwater transects along the south-west coast of India

South-west coast of India has a history of using pesticidal persistent organic pollutants (POPs) particularly endosulfan until aerial spraying was banned during early 2000. Since soil acts as a repository for such pesticidal persistent organic contaminants, we have monitored residues of seventeen organochlorine pesticides (OCPs) in the surface soil samples from the agricultural, coastal, and backwater transects along the south-west coast of India. OCPs concentration in soil were in the order agricultural > coastal > backwaters transects. Endrins, hexachlorocyclohexane (HCH) and heptachlors were among the dominant OCPs quantified in this study. Dominance of metabolites such as dichlorodiphenyldichloroethylene (DDE), dichlorodiphenyldichloroethane (DDD) and endosulfan sulfate indicates past usage. All the OCPs were dominant in the agricultural transect where plantations/agricultural activities are prevalent. In some specific sites, traces of HCH isomers showed ongoing usage of technical HCH in those sites contradicting the ban in agricultural sector. Backwater sites which are background locations showed positive correlation between soil organic carbon and soil borne OCPs thereby indicating an aged source possibly due to the short/long atmospheric transport from the site of application. Based on the policies regarding control, prevention and other measures for the management of pesticides in Kerala, it was concluded that the implementation on the ground level and the legal framework should be strengthened to prevent further illegal use of the banned pesticides.

Distribution Pattern of Organophosphate Esters in Particle-Size Fractions of Urban Topsoils Under Different Land-Use Types and Its Relationship to Organic Carbon Content

In this study, the distribution pattern of organophosphate esters (OPEs) in particle-size fractions of urban topsoils under different land-use types and its relationship to organic carbon content was investigated. Total OPEs concentrations in different particle-size fractions ranged from 17.07 to 221.77 ng/g. The distribution pattern of total OPEs concentrations and individual OPE concentration in different particle-size fractions were irregular and varied with the land-use type. The mass of OPEs is concentrated in small particles, large particles, or evenly distributed in each particle. This distribution pattern mainly depends on the mass distribution of each fraction to the soil. Tri-iso-butyl phosphate, tributyl phosphate, and triphenylphosphine oxide have a relatively higher concentration in most samples, and the concentration of tripropyl phosphate was the lowest in all samples. The correlations between total OPEs concentrations versus total organic carbon (TOC), black carbon (BC), and other carbon (OC) is weak. Their linear regression correlation coefficients were 0.0495, 0.0823, and 0.0097, respectively. The correlation between individual OPE concentrations versus TOC, BC, and OC also are weak. Except for triethyl phosphate, tris-(2-chloroethyl) phosphate, and tris-(1-chloro-2-propyl) phosphate, the linear regression correlation coefficients of other OPEs are all less than 0.1.

Concentration and distribution of pesticide residues in soil: Non-dietary human health risk assessment

Soil contamination by pesticide residues is a primary concern because of the high soil persistence of pesticides and their toxicity to humans. We investigated pesticide concentration and distribution at 3 soil depths in 147 soil samples from agricultural land and assessed potential health risks due to non-dietary human exposure to pesticides in Nepal. About sixty percent of the soil samples had pesticides (25% of the soil samples had single residue, 35% of the soil samples had mixtures of 2 or more residues) in 39 different pesticide combinations. Pesticide residues were found more frequently in topsoil. Overall, the concentration of pesticides ranged from 1.0 μg kg^-1 to 251 μg kg^-1, with a mean of 16 μg kg^-1. The concentration of the primary group, organophosphates (OPs), ranged from 1.23 μg kg^-1 to 239 μg kg^-1, with a mean of 23 μg kg^-1. Chlorpyrifos and 3,5,6-trichloro-2-pyridinol (TCP) were the predominant contaminants in soils. The ionic ratio of DDT and its degradation products suggested a continuing use of DDT in the area. Human health risk assessment of the observed pesticides in soil suggested negligible cancer risks and negligible non-cancer risks based on ingestion as the primary route of exposure. The predicted environmental concentrations (PECs) of pesticides were higher than the values found in the guidance for soil contamination used internationally. Low concentrations of residues in the soils from agricultural farms practicing integrated pest management (IPM) suggest that this farming system could reduce soil pollution in Nepal.

Polychlorinated biphenyls and organochlorines pesticides in indoor dust: An exploration of sources and health exposure risk in a rural area (Kopawa) of Nepal

While contamination of indoor environment with organochlorine compounds (OCs) is well documented worldwide, only a few studies highlighted the problem of indoor pollution in Indian sub-continent, including Nepal. This study insight the contamination level, distribution pattern, and sources of OCs in indoor dust from a rural area of Nepal. Additionally, daily exposure risk through different intake pathways was estimated in order to mark the potential risk of OCs to local residents. Results indicated the predominance of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in dust. Ʃ₂₆OCPs (median 87 ng/g) in dust was about 7-8 times greater than Ʃ₃₀PCBs (median 10.5 ng/g). DDT was the most abundant chemical among Ʃ₂₆OCPs, followed by HCHs and endosulfan, and accounted for 73%, 7%, and 4% of Ʃ₂₆OCPs, respectively. A relatively high level of ƩDDT than other OCPs suggests the existence of DDT source in the Nepalese environment. Among PCB, tetra-CBs were most prevalent, trailed by penta-CBs, hexa-CBs, and hepta-CBs, and comprised 28%, 21%, 17% and 17% of Ʃ₃₀PCBs, respectively. Dioxin like-PCBs (median 3.48 ng/g) was about two times higher than the total indicator-PCB (median 1.63 ng/g). High p,p-DDT/p,p-DDE ratio (median 2.89) suggested fresh application and minimal degradation of DDT in the local environment of Kopawa. While lower α-/γ-HCH ratio (median 0.75) indicated lindane contamination as the primary sources of HCH. Moreover, the low α-/β-endosulfan ratio (median 0.86) specified the fresh use of commercial endosulfan. Among OCPs, only DDT positively related to total organic carbon (TOC) (Rho = 0.55, p < 0.05) but not black carbon (BC), proposing minimal or zero impact of TOC and BC. For PCBs, PCB-126 was moderately and negatively correlated with TOC (Rho = -0.49, p < 0.05), but not BC. The daily risk exposure (DRE) assessment showed that children are more vulnerable to OCs than the adult. The DRE of OCs in this study were 2-4 order of magnitude lower than their corresponding reference dose (RfD), proposing insignificant risk.

Presence and Health Risks of Obsolete and Emerging Pesticides in Paddy Rice and Soil from Thailand and China

Organochlorine (OCPs) and organophosphorus pesticides (OPPs) have been intensively applied in rice paddy field farming to control pest infestation and increase the yield. In this study, we investigated the presence of organochlorine and organophosphorus pesticides in paddy rice and soil from rice plantations in Thailand and China. According to concentration and distribution of OCPs, the most abundant OCPs residues in rice and soil from Thailand and China were dichlorodiphenyltrichloroethane and hexachlorocyclohexanes. The OPPs of methidathion, carbophenothion, chlorpyrifos, and diazinon were common to Thailand and China in both types of samples. The detection frequency of multiple types of these pesticides was greater than 50% of total samples. The relative concentration of some OPPs residues in rice and soil from Thailand and China were significantly different from each other (p < 0.0083), whereas, no significant difference was observed for the relative concentration of OCPs residues in rice and soil from both countries, except for HCHs (p < 0.05). Bioaccumulation factors of OCPs between rice and soil samples indicated that OCPs and OPPs in soil could accumulate in rice. The carcinogenic and non- carcinogenic risks of OCPs and OPPs seem to be in the safe range as recommended by the European Union.

Organochlorine pesticides in the surrounding soils of POPs destruction facility: source fingerprinting, human health, and ecological risks assessment

The elimination of persistent organic pollutants (POPs) obsolete pesticides stockpiles, particularly the organochlorine pesticides (OCPs), is one of the critical environmental issues faced by many developing countries. This pioneering study aimed to investigate the occurrence, source fingerprinting, human health, and ecological risks of OCPs in the surroundings of the lone POPs pesticide destruction facility in Pakistan. The ΣOCPs residual levels in soil ranged from 35.98 to 566.77 ng/g dry weight (dw), with a mean concentration of 174.42 + 111.62 ng/g (dw). The OCPs contamination levels in the soil followed the pattern as ΣHCHs > Σendrins > Σendosulfans > dieldrin > Σheptachlors > ΣDDTs > Σchlordanes > methoxychlor. The ΣHCHs residual concentrations were comparatively higher than the previous national and global soil studies. The recent accumulation of HCHs, DDTs, and heptachlor was observed in the study area as identified by β-HCH/∑HCHs, (DDE + DDD)/ΣDDTs, heptachlor/Σheptachlor, and heptachlor exo-epoxide/heptachlor ratios. The OCPs' lifetime carcinogenic risk through ingestion, dermal, and inhalation exposure routes ranged from 1.65E-08 to 2.91E-07, whereas the noncarcinogenic hazard quotient (HQ) ranged from 9.12E-05 to 1.61E-03. The risk vulnerability among age groups was in the order: adult > toddler > child > teen > infant. The calculated risk levels were within an acceptable limit of one in a million (1 × 10^-6) for carcinogenic risk and HQ < 1 for noncarcinogenic risk. The current OCPs residual levels, especially dieldrin and endrin, exhibited low to medium ecological risks when compared to various worldwide limits. The upsurge of the OCPs' environmental contamination levels over the years and consideration of the food chain transfer might amplify the human health and ecological risks intensities.

Phytoremediation and Bioremediation of Pesticide-Contaminated Soil

Management and destruction of obsolete pesticides and the remediation of pesticide-contaminated soil are significant global issues with importance in agriculture, environmental health and quality of life. Pesticide use and management have a history of problems because of insufficient knowledge of proper planning, storage, and use. This manuscript reviews recent literature with an emphasis on the management of obsolete pesticides and remediation of pesticide-contaminated soil. The rhizosphere of plants is a zone of active remediation. Plants also take up contaminated water and remove pesticides from soil. The beneficial effects of growing plants in pesticide-contaminated soil include pesticide transformation by both plant and microbial enzymes. This review addresses recent advances in the remediation of pesticide-contaminated soil with an emphasis on processes that are simple and can be applied widely in any country.

Examining the role of total organic carbon and black carbon in the fate of legacy persistent organic pollutants (POPs) in indoor dust from Nepal: Implication on human health

Despite the fact that the consumption and import of legacy persistent organic pollutants (POPs) have been stopped in Nepal since 2001, they are still of worry for human prosperity and the environment because of their persistence behavior and constant release from sources that are presently being used. The essential objective of this study was to assess the concentration and spatial distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in residential dust from Nepal keeping in mind the end goal to evaluate the importance of total organic carbon (TOC) and black carbon (BC) in the fate of legacy POPs. Additionally, health risk exposure via dust ingestion and dermal absorption was estimated to evaluate the significance of dust media for human exposure. Results demonstrated that ∑OCPs in dust was 37 times greater than ∑PCBs. DDT was mostly dominated in the dust, and contributed 90% of the ∑OCPs, while hexa-CBs predominated among PCBs and represented 34% of ∑PCBs. Birgunj and Biratnagar had a relatively higher level of ∑OCPs and ∑PCBs than those of Kathmandu and Pokhara. TOC and BC showed a poor connection with OCPs, recommending little or no role. However, PCB in the dust, especially low congeners was strongly linked with TOC but not BC indicating the significant role of TOC. The daily risk exposure estimation indicated dermal absorption through dust as the principal means of OCPs/PCBs intake to both adult and children population. These estimated exposures were 2-4 orders of magnitude inferior to their corresponding reference dose showing insignificant risk.

Comparative acute toxicity of two phytosanitary molecules, lambda-cyhalothrin and acetamiprid, on Nile Tilapia (Oreochromis Niloticus) juveniles

This study aimed to compare the toxicity for fish of two active ingredients (lambda-cyhalothrin-20 g L^-1, a pyrethroid, and acetamiprid-15 g L^-1, a neonicotinoid) which are components of a commercial insecticide (Acer 35 EC) used in cotton crop in many West African countries. The juveniles of Oreochromis niloticus (4.01 ± 0.34 g, mean body weight) were exposed for 96 h to increasing concentrations of active ingredients (lambda-cyhalothrin and acetamiprid) or a mixture similar to Acer 35 EC (composed by 20 g of chemical compound lambda-cyhalothrin and 15 g of acetamiprid dissolved in 1 L of acetone). The experiments were carried out under controlled conditions in aquaria according to OECD Guidelines. During the experiments, the behavioral responses (loss of balance, color change, hyperactivity, etc.) that usually precede death were observed in exposed fish. Mortalities were recorded in each aquarium and the LC₅₀-96h of each chemical was determined. The LC₅₀-96h obtained were respectively 0.1268, 0.0029, 182.9 and 0.5685 ppm for Acer 35 EC, lambda-cyhalothrin, acetamiprid and mixture. All insecticides used in this study had profound impact on Nile tilapia behavior which may confirm the neurotoxicity of each single active compound as well as of their mixture.

A nationwide survey of 19 organophosphate esters in soils from China: Spatial distribution and hazard assessment

Organophosphate esters (OPEs) are ubiquitous in the environment, but little is known about their distribution in soils. In this study, we measured 19 OPEs in soil samples collected nationwide in China for the first time. Concentrations of 19 OPEs (∑OPEs) in soils ranged from 4.50 to 430 ng/g dry weight (dw), with a median value of 36.6 ng/g dw. ∑OPE concentrations in soils were significantly higher in Northeastern (90.6, 19.1-180 ng/g dw; median, range) and Eastern/Southern China (57.4, 7.23-430 ng/g dw), areas with high population density and economic development, than those in Central (35.8, 4.80-417 ng/g dw) and Western China (29.7, 4.50-228 ng/g dw). High concentrations of ∑OPEs were found in soils collected from sites located in the most urbanized areas of China including Beijing (126 ng/g dw), Shanghai (388 ng/g dw), and Guangzhou (430 ng/g dw). Chlorinated (Cl-) OPEs were the predominant compounds, accounting for over 74.0% of ∑OPE concentrations in soils from China. In soil samples from Northeastern and Eastern/Southern China, Cl-OPEs accounted for 84.3% and 92.1% of ∑OPE concentrations, respectively. Cresyl diphenyl phosphate (CDPP) and isodecyl diphenyl phosphate (IDDP), which have been less studied thus far, were also found at measurable concentrations (0.15-0.40 ng/g dw) in soils. The Spearman's rank correlations among major aryl-OPEs in soils were significant (Rho = 0.582-0.747, p < 0.01), which suggested similar sources of environmental release of these compounds. Total organic carbon (TOC) content was not correlated with the concentrations of ∑OPE in soils (Rho = 0.036, p > 0.05). A hazard assessment for ten OPEs in soils suggested a notable risk from tris(2-ethylhexyl) phosphate (TEHP) and trimethylphenyl phosphate (TMPP). Further studies are needed to elucidate the fate of TMPP in soils.

Pesticide residues in Nepalese vegetables and potential health risks

We conducted this study in order to assess the pesticide residues in vegetables and examine the related human health risk. Therefore, residues of 23 pesticides (organophosphates, organochlorines, acaricides, fungicides, and insecticides of biological origin) were analysed in the three main vegetable crops grown in Southern Nepal: 27 eggplant, 27 chilli and 32 tomato samples representing (i) conventional (N = 67) and ii) integrated pest management (IPM) fields (N = 19). Pesticide residues were found in 93% of the eggplant samples and in all of the chilli and tomato samples. Multiple residues were observed in 56% of the eggplant samples, 96% of chilli samples and all of the tomato samples. The range (µg/kg) of total detected pesticide residues in eggplants, chillies and tomatoes was 1.71-231, 4.97-507, 13.1-3465, respectively. The most frequently detected pesticides in these vegetables were carbendazim and chloropyrifos. Pesticide residues in 4% of the eggplant, 44% of the tomato and 19% of the chilli samples exceeded the EU maximum residue limits (MRLs). The residues of triazophos, omethoate, chloropyrifos and carbendazim exceeded the EU MRLs. Compared to chilli and eggplant crops, more carbendazim was sprayed onto tomato crops (p < 0.05). We assessed adolescent and adult dietary exposure using hazard quotient (HQ) and hazard index (HI) equations for the identified pesticides. HQ> 1 was observed for chloropyrifos, triazophos and carbendazim in eggplants; profenofos, triazophos, dimethoate, omethoate, chloropyrifos and carbendazim in tomatoes; and dichlorvos and chloropyrifos in chillies. Of all of the HQs, the highest acute HQ (aHQ) was for triazophos (tomato) in adolescents (aHQ=657) and adults (aHQ=677), showing the highest risks of dietary exposure. The cumulative dietary exposure showed a higher HI for organophosphates (HI>83) and a lower HI for organochlorines, acaricides and biological insecticides (HI<1). The concentration of pesticide residues in the vegetable crops from the IPM field was considerably lower, suggesting a greater ability of IPM systems to reduce the dietary risks from exposure to pesticides.

Insight into occurrence, profile and spatial distribution of organochlorine pesticides in soils of solid waste dumping sites of Pakistan: Influence of soil properties and implications for environmental fate

Waste dumping sites are considered as significant disposal pathway for waste contaminants including pesticides. In the present study OCPs were analyzed in soils of waste dumping sites of Pakistan. The mean concentrations of OCPs were in the order: ∑DDTs>∑HCHs>∑Endosulfan>∑HCB>Heptachlor. Order of overall ∑OCPs contamination with respect to location was Lahore>Sukkur>Karachi>Kamoki>Faisalabad>Hyderabad>Losar>Gujrat>Peshawar. Distribution of OCPs in solid waste dumping site was mainly influenced by textural classes, input history and pollution source. Soil texture was the dominant factor for retention of OCPs, whereas TOC and black carbon has not significantly impacted the concentrations of OCPs. Diagnostic ratios indicated the historical input, anaerobic degradation pathway and use of technical mixtures of DDTs in majority of waste dumping sites whereas for HCHs recent as well as past usage of technical mixture was prevalent in most of the areas. Regression analysis revealed a weak positive correlation of OCPs with socioeconomic indices (HDI, Population, waste generation) which is linked with history of use of these contaminants in the respective areas. Forecasted waste generation quantity for the year 2026 showed that waste generation amount will get doubled by the year 2026 suggesting the need properly designed waste management system.

Spatial distribution, source analysis, and health risk assessment of heavy metals contamination in house dust and surface soil from four major cities of Nepal

Raising population, deteriorating environmental conditions and limiting natural resources to handle the key environmental health problems have critically affected human health and the environment. Policy makers and planners in Nepal are more concerned today than at any other time in the past about the deterioration of the environmental condition. Therefore, understanding the connection between pollution and human wellbeing is fundamental endeavors to control pollution exposures and secure human wellbeing. This ability is especially critical for countries like Nepal where the issues of environmental pollution have customarily taken a second place to request for economic development. In this study, spatial distribution and sources of 12 heavy metals (HMs) were investigated in surface soils (n = 24) and house dust (n = 24) from four major urban areas of Nepal in order to mark the pollution level. Additionally, a health risk was estimated to establish the link between HMs pollution and human health. Results showed that the median concentration of Ag, Cd, Co, Cr, Cu, Ni, Pb, Sb, Mn and Zn in soil and dust were 2-13 times greater than the background value. The As, Zn, Cu, Cd, and Pb showed a relatively higher spatial variability in soil and dust. Zn was the most abundant metal measured in dust and soil and accounted for 59% and 55% of ∑₇HMs, respectively. The HMs in soil and dust were poorly correlated with total organic carbon (TOC) and black carbon (BC), suggesting little or no influence on HMs contamination. Source analysis study indicated the distribution of Cr, Ni, Sb, Ag, Pb, Cu, and Zn in soil and dust are mainly affected by anthropogenic sources, particularly traffic emissions, industrial source, and domestic households materials, while Co, Fe, As, Mn and Cd were from natural sources. The estimated carcinogenic risk (CR) of HMs in soil and dust exceeded the acceptable level of human exposure, recommending significant CR to the local population.

Endocrine disrupting pesticides in soil and their health risk through ingestion of vegetables grown in Pakistan

A comprehensive study was conducted to appraise the concentrations of 30 endocrine disrupting pesticides (EDPs) in soil and vegetable samples collected from Khyber Pakhtunkhwa, Pakistan. The sum of 30 EDPs (Σ₃₀EDPs) ranged from 192 to 2148 μg kg^-1 in the collected soils. The selected EDP concentrations exceeded their respective limits in most of the tested soils and showed great variation from site to site. Similarly, high variations in Σ₃₀EDP concentrations were also observed in vegetables with the highest mean concentration in lettuce (28.9 μg kg^-1), followed by radish (26.6 μg kg^-1), spinach (25.7 μg kg^-1), onion (16.2 μg kg^-1), turnip (15.6 μg kg^-1), and garlic (14.7 μg kg^-1). However, EDP levels in all studied vegetables were within FAO/WHO limits. The mean bioconcentration factor values were observed < 1 for all the studied vegetables. The health risk assessment revealed that the incremental lifetime cancer risk (ILCR) of Σ₃₀EDPs associated with vegetable ingestion was below the acceptable risk level (1 × 10^-6), showing no cancer risk to local inhabitants. However, exposure to endocrine disruptor and probable carcinogen heptachlor epoxide poses a potential non-cancer risk (hazard quotient (HQ > 1)) to children through vegetable consumption. The presence of banned EDPs in soils and vegetables of the study area indicates the stability of these legacy chemicals in the environment from over usage in the past or illegal current application for agricultural purposes. Graphical abstract.

Distribution, sources, and air-soil exchange of OCPs, PCBs and PAHs in urban soils of Nepal

Due to the high temperature and extensive use of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), tropical cities could act as secondary sources of these pollutants and therefore received global concern. As compared with other tropical cities, studies on the air-soil exchange of OCPs, PCBs and PAHs in tropical Nepali cities remained limited. In the present study, 39 soil samples from Kathmandu (capital of Nepal) and 21 soil samples from Pokhara (second largest city in Nepal) were collected The soil concentrations of the sum of endosulfans (α- and β-endosulfans) ranged from 0.01 to 16.4 ng/g dw. Meanwhile, ∑dichlorodiphenyltrichloroethane (DDTs) ranged from 0.01 to 6.5 ng/g dw; ∑6PCBs from 0.01 to 9.7 ng/g dw; and ∑15PAHs from 17.1 to 6219 ng/g dw. High concentrations of OCPs were found in the soil of commercial land, while, high soil PAH concentrations were found on tourist/religious and commercial land. Combined the published air concentrations, and the soil data of this study, the directions and fluxes of air-soil exchange were estimated using a fugacity model. It is clear that Nepal is a country contributing prominently to secondary emissions of endosulfans, hexachlorobenzene (HCB), and low molecular weight (LMW) PCBs and PAHs. The flux for all the pollutants in Kathmandu, with ∑endosulfans up to 3553; HCB up to 5263; and ∑LMW-PAHs up to 24378 ng m^-2 h^-1, were higher than those in Pokhara. These high flux values indicated the high strength of Nepali soils to act as a source.

Polycyclic aromatic hydrocarbons in house dust and surface soil in major urban regions of Nepal: Implication on source apportionment and toxicological effect

Urban centers have turned to be the provincial store for resource consumptions and source releases of different types of semi-volatile organic compounds (SVOCs) including polycyclic aromatic hydrocarbons (PAHs), bringing about boundless environmental pollutions, among different issues. Human prosperity inside urban communities is unambiguously dependent on the status of urban soils and house dusts. However, environmental occurrence and sources of release of these SVOCs are challenging in Nepalese cities, as exceptionally very limited data are accessible. This motivated us to explore the environmental fate, their source/sink susceptibilities and health risk associated with PAHs. In this study, we investigated the contamination level, environmental fate and sources/sink of 16 EPA's priority pollutants in surface soil and house dusts from four major cities of Nepal. Additionally, the toxicological effect of individual PAH was studied to assess the health risk of PAHs. Generally, the concentrations of ∑₁₆PAHs in surface soil were 1.5 times higher than house dust, and ranged 767-6770ng/g dry weight (dw) (median 1810ng/g dw), and 747-4910 dw (median 1320ng/g dw), respectively. High molecular weight-PAHs both in soil and dust were more abundant than low molecular weight-PAHs, suggesting the dominance of pyrogenic source. Moderate to weak correlation of TOC and BC with PAHs in soil and dust suggested little or no role of soil organic carbon in sorption of PAHs. Source diagnostic ratio and principal component analysis indicated fossil fuel combustion, traffic/vehicular emissions and combustion of biomass are the principal sources of PAHs contamination in Nepalese urban environment. The high average TEQ value of PAHs in soil than dust suggested high risk of soil carcinogenicity compared to dust.

Environmental concentration and atmospheric deposition of halogenated flame retardants in soil from Nepal: Source apportionment and soil-air partitioning

While various investigations have been driven on polybrominated diphenyl ethers (PBDEs) and other flame retardants (FRs) in different framework around the world, information about contamination and fate of PBDEs and other FRs in developing countries especially in the Indian subcontinent is uncommon. Nepal being located in the Indian subcontinent, very little is known about contamination level of semi-volatile organic pollutants discharged into the environment. This motivated us to investigate the environmental fate of halogenated flame retardant (HFRs) in Nepalese condition. In this study, we investigated the concentration, fate, and sources of 9 PBDEs, 2 dechlorane plus isomers (DPs), and 6 novel brominated flame retardants (NBFRs). Moreover, air-soil exchange and soil-air partitioning were also evaluated to characterize the pattern of air-soil exchange and environmental fate. In general, the concentrations of NBFRs in soil were more prevalent than PBDEs and DPs, and accounted 95% of ∑HFRs. By and large, the concentrations of NBFRs and DPs were measured high in Kathmandu, while PBDEs level exceeded in Pokhara. Principal component analysis (PCA) study suggested contributions from commercial penta-, octa-, and deca-BDEs products and de-bromination of highly brominated PBDEs as the significant source of PBDEs. Likewise, low f_anti ratio suggested DPs in soil might have originated from long-range atmospheric transport from remote areas, while high levels of decabromodiphenyl ethane (DBDPE) in soil were linked with the use of wide varieties of consumer products. The estimated fugacity fraction (ff) for individual HFR was quite lower (<0.05) than equilibrium value, suggesting that deposition and net transport from air to the soil is overwhelming. Soil-air partitioning study revealed neither octanol-air partition coefficient (K_OA) nor black carbon partition coefficient (K_BC-A) is an appropriate surrogate for soil organic matter (SOM), subsequently, absorption by SOM has no or little role in the partitioning of HFRs.

Organophosphate ester flame retardants in Nepalese soil: Spatial distribution, source apportionment and air-soil exchange assessment

Despite soil being the major terrestrial environmental reservoir and one of the significant sinks for many hydrophobic organic compounds including organophosphate ester flame retardants (OPFRs), limited information is available about concentration and fate of OPFRs contamination in urban soil in general and especially in case of Nepal. This study investigates the environmental concentration, spatial distribution and source apportionment of eight OPFRs in surface soil (n = 28) from four major cities of Nepal with special interest on air-soil exchange. Overall, significantly high concentrations of ∑₈OPFR were measured in soil ranging from 25-27,900 ng/g dw (median 248 ng/g dw). In terms of compositional pattern, tris(methyl phenyl) phosphate (TMPP) was the most abundant phosphorus chemical in soil, followed by tris(2-chloroisopropyl) phosphate (TCIPP), and accounted for 35-49% and 8-25% of ∑₈OPFRs, respectively. The high level of these OPFRs was attributed to local sources as opposed to transboundary influence from remote areas. A Spearman's rank correlation analysis exhibited weak correlation of ∑₈OPFRs with TOC (Rho = 0.117, p < 0.05) and BC (Rho = 0.007, p < 0.05), suggesting little or no influence of TOC and BC on the concentration of ∑₈OPFRs. The fugacity fraction (ff) results indicated a strong influence of soil contamination on atmospheric level of OPFRs via volatilization.

Polychlorinated biphenyls in Nepalese surface soils: Spatial distribution, air-soil exchange, and soil-air partitioning

Regardless of the ban on the polychlorinated biphenyls (PCBs) decade ago, significant measures of PCBs are still transmitted from essential sources in cities and are all inclusive ecological contaminants around the world. In this study, the concentrations of PCBs in soil, the air-soil exchange of PCBs, and the soil-air partitioning coefficient (K_SA) of PCBs were investigated in four noteworthy urban areas in Nepal. Overall, the concentrations of ∑₃₀PCBs ranged from 10 to 59.4ng/g dry weight; dw (mean 12.2ng/g ±11.2ng/g dw). The hexa-CBs (22-31%) was most dominant among several PCB-homologues, followed by tetra-CBs (20-29%), hepta-CBs (12-21%), penta-CBs (15-17%) and tri-CBs (9-19%). The sources of elevated level of PCBs discharge in Nepalese soil was identified as emission from transformer oil, lubricants, breaker oil, cutting oil and paints, and cable insulation. Slightly strong correlation of PCBs with TOC than BC demonstrated that amorphous organic matter (AOM) assumes a more critical part in holding of PCBs than BC in Nepalese soil. The fugacity fraction (ff) results indicated the soil being the source of PCB in air through volatilization and net transport from soil to air. The soil-air partitioning coefficient study suggests the absorption by soil organic matter control soil-air partitioning of PCBs. Slightly weak but positive correlation of measured Log K_SA with Log K_OA (R² = 0.483) and Log K_BC-A (R² = 0.438) suggests that both Log K_OA and Log K_BC-A can predict soil-air partitioning to lesser extent for PCBs.