Characteristics of residual organochlorine pesticides in soils under different land-use types on a coastal plain of the Yellow River Delta

Air pollutants in bronchoalveolar lavage fluid and pulmonary tuberculosis: A mediation analysis of gene-specific methylation

Particulate matter (PM) exposure could alter the risk of tuberculosis, but the underlying mechanism is still unclear. We enrolled 132 pulmonary tuberculosis (PTB) patients and 30 controls. Bronchoalveolar lavage fluid samples were collected from all participants to detect organochlorine pesticides, polycyclic aromatic hydrocarbons, metal elements, and DNA methylation of immunity-related genes. We observed that γ-HCH, Bap, Sr, Ag, and Sn were related to an increased risk of PTB, while Cu and Ba had a negative effect. IFN-γ, IL-17A, IL-2, and IL-23 had a higher level in the PTB group, while IL-4 was lower. The methylation of 18 CpG sites was statistically associated with PTB risk. The methylation at the IL-4_06_121 site showed a significant mediating role on γ-HCH, Sr, and Sn. Our study suggests that PM exposure can increase the risk of tuberculosis by affecting DNA methylation and cytokine expression.

Occurrence and exposure risk assessment of organochlorine pesticides in two waterbird species from Honghu Lake Wetland, Central China

Monitoring and evaluating bird exposure to hazardous pollutants in wetlands are receiving considerable attention. In this study, the occurrence of 18 organochlorine pesticides (OCPs) in the muscle of bean geese (Anser fabalis) and common teals (Anas crecca) collected from Honghu Lake Wetland (HLW), Central China was studied. Additionally, an exposure risk assessment model was applied to obtain risk levels of OCPs to these birds through three oral routes (food intake, water drinking and soil ingestion). The results suggested that the most abundant OCPs detected in the muscle of waterbirds were DDTs (7.68-602 ng/g lipid weight), followed by HCHs (1.39-89.8 ng/g lipid weight). A significant difference (p < 0.05) existed between two species, but most of OCPs exhibited no statistically relationship with age or gender (p > 0.05). The compositional patterns of OCPs combined with ratios of certain metabolites to their parent compounds indicated that all OCPs in the HLW were largely from historical usage except heptachlor. The exposure risk assessment revealed that common teals with lighter weight had greater exposure risks than bean geese. Of the OCPs analyzed, DDTs could probably cause harm to target birds studied here. Exposure via food intake was identified to be significant while soil ingestion and water drinking contributed least, but they should still be concerned.

Typical organic contaminants in hair of adult residents between inland and coastal capital cities in China: Differences in levels and composition profiles, and potential impact factors

The growing of urbanization, industrialization, and agricultural production have resulted in the increasing contamination of typical organic contaminants (OCs) in China. However, data on differences in exposure characteristics of typical OCs between the coastal and inland cities among residents in China are limited. In this study, hair samples were collected from adult residents in 10 and 17 provincial capital cities in coastal and inland China, respectively, to investigate the differences in the levels and composition profiles of typical OCs. The potential factors impacting the human exposure to OCs were also examined based on the relationship among the hair OC levels and the population characteristics and statistical indicators. The median concentrations of dichlorodiphenyltrichloroethane's (DDTs), polybrominated diphenyl ethers (PBDEs), and organophosphorus flame retardants (PFRs) in hair of coastal urban residents were 3.64, 5.58, and 268 ng/g, respectively, while their concentrations in samples from inland urban residents were 1.84, 3.85, and 202 ng/g, respectively. Coastal residents showed significantly higher hair OC concentrations than inland residents (p < 0.05). BDE209 and p,p'-DDE were the predominant chemicals for PBDEs and DDTs, respectively, in both coastal and inland cities. Tris(2-chloroisopropyl) phosphate (TCIPP) was the dominant PFR in coastal residents' hair, while triphenyl phosphate (TPHP) was the major PFR in inland residents' hair, possibly owing to the different usages of the PFRs. Significant gender differences were observed in the levels and composition profiles of OCs (p < 0.05). The levels of p,p'-DDE and TCIPP were significantly related to the gross domestic product (GDP), gross secondary industry product, and the per capita consumption of aquatic products (p < 0.05). This study provides scientific data for evaluating human exposure to OCs in urban residents at a large scale and its associations with statistical indicators including urbanization, industrialization, agricultural production, and diet in China.

Coming ecological risks of organochlorine pesticides and novel brominated flame retardants in the Yellow River Basin

To conduct ecological risk assessment, food, water and soil samples were collected from five densely populated irrigation areas in the Yellow River Basin (YRB), and analyzed for organochlorine pesticides (OCPs) and novel brominated flame retardants (NBFRs). The results showed that the OCP residues (∑₁₄OCP were 0.748 ng L^-1, 13.1 ng g^-1 dw and 3.22 ng g^-1 dw in water, soil and maize) were generally within moderate levels in the YRB. Dichlorodiphenyltrichloroethane (DDT) residues dominated the OCPs, and potential ecological risks to aquatic and terrestrial organisms likely stemmed from dichlorodiphenyldichloroethylene (DDE) pollution in the upper reaches of the YRB in the Ningxia and Hetao Plain. The NBFR concentrations in the YRB were 90.9 pg L^-1 in water, 21.1 pg g^-1 dw in soil and 3.81 pg g^-1 dw in maize. Positive correlations were observed between soil and maize contamination in the five irrigated districts, indicating a potential threat to grain security and human health risks caused by OCPs and NBFRs. Pollutants detected in soil and maize primarily originated from historical use (36.3 %), while the sources in water were more complex (64.4 %) and new inputs could not be excluded. Integrated health risks of human exposure to agricultural products and water from the YRB were acceptable. However, the ecological risk of the Ningxia Plain would further deteriorate to the medium risk after 2032. The increasing ecological risk of DDT in water indicates that regular monitoring should strengthen to ensure grain and water safety in the YRB.

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.

Evaluation of residual level and distribution characteristics of organochlorine pesticides in agricultural soils in South Korea

In this study, we evaluated the residual levels and distribution characteristics of 10 organochlorine pesticides (OCPs) in the soil of agricultural lands (paddy field, vegetable field, and orchard, n = 150) nationwide. As a result of the investigation, 3-10 types of OCPs were detected in combination in 144 locations (96%) of the total 150 locations. Among those OCPs, dichlorodiphenyltrichloroethane (DDT) and endosulfan were detected in high amounts. The geometric mean concentrations of DDT and endosulfan were ∑DDT 0.31 ng g^-1 (ND-2187.18 ng g^-1) and ∑endosulfan 0.33 ng g^-1 (ND-312.68 ng g^-1), respectively. OCP concentrations were generally higher in orchards than in other agricultural fields due to a large amount of pesticides used. DDT in two orchards was detected at 2187.18 ng g^-1 and 1061.78 ng g^-1, exceeding the levels stated in the Canadian DDT Soil Quality Guidance (SQG, 700 ng g^-1). The result of applying the isomer ratio to evaluate the recent or past use of DDT, endosulfan, and hexachlorocyclohexane (HCH), which had a high detection rate, showed that it could be attributable to historical usage. DDT and HCH showed statistically similar residual distribution patterns; however, endosulfan did not show a clear correlation with DDT and HCH due to the effect of its recent use. Thus, the results of evaluation of OCP residual levels and distribution characteristics can be used for the soil management policy of OCPs in agricultural lands in Korea.

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.

Temporal and sex-based variation in organochlorine pesticide levels in the blue-footed booby in two coastal colonies of Sinaloa, Mexico

The temporal, inter-site, and sex-based variation of 19 organochlorine pesticides (OCPs) in blood plasma samples collected from blue-footed boobies of two islands in Sinaloa, Mexico, was evaluated. The effect of OCPs was evaluated with the heterophil/lymphocyte ratio, micronucleated erythrocyte frequency, and scaled mass index. The OCP-group levels decreased as the breeding season progressed, and interannual (but not inter-colony) differences were detected. Intra-annual variation in OCP levels seemed to reflect run-off inputs, although other environmental processes may better explain the variation between years. Sex-based differences in OCP levels were likely related to ecological and physiological processes linked to breeding (e.g., egg-laying and use of lipid reserves). No correlations between OCP-group levels and biomarkers were detected. Small pelagic fishes are the main prey sources of blue-footed boobies and the targets of regional industrial fisheries, and thus blue-footed booby OCP levels could reflect ecosystem health and indicate potential risks for human consumers.

Levels of persistent organic pollutants in pine tree components and ambient air

Pine needles are employed as alternative biomonitoring agents in atmospheric studies. In this study, pine (Pinus Pinea) components (needles and branches) and air samples were collected simultaneously to monitor polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) from Gemlik, Turkey between January and December 2016. The relationship between ambient air and pine needles were examined to enlighten the usability of pine components as passive samplers for persistent organic pollutants (POPs) in the Marmara region. Average ∑₁₄PAH concentrations for the ambient air, pine needles, and pine branches were 23.1 ± 18.3 ng/m³, 626 ± 306 ng/g DW and 548 ± 261 ng/g DW respectively. PCB concentrations were 118 ± 74 pg/m³, 7.5 ± 2.1 ng/g DW and 6.8 ± 2.9 ng/g DW and ∑₁₀ OCP concentrations were 122 ± 89 ng/m³,1.3 ± 1.5 ng/g DW and 10.0 ± 3.8 ng/g DW in the same order. Levels of PAHs and PCBs were higher in needles than branches. PAH, PCB and OCP concentrations in pine components tended to decrease with increasing temperatures in spring. PAH compounds with medium and light molecular weighted ones were found to be dominant. On the other hand, the predominant PCB components were the medium-weighted congeners while γ-HCH, Heptachlor endo. Epox. Iso A, endrin aldehyde, and methoxychlor were the dominant OCP species.

Magnetic solid phase extraction using Fe3O4@β-cyclodextrin–lipid bilayers as adsorbents followed by GC-QTOF-MS for the analysis of nine pesticides

A rapid method for the analysis of trace organochlorine pesticides in a complex matrix.

Clustering Coastal Land Use Sequence Patterns along the Sea–Land Direction: A Case Study in the Coastal Zone of Bohai Bay and the Yellow River Delta, China

Specific knowledge about the characteristics of coastal land use along the sea–land direction helps to better understand the spatial heterogeneity of coastal land use, which could offer scientific support for rational land management and the sustainable development of the coastal zone. However, the traditional methods including buffering or the regional method are hard to extract detailed spatial structure and location correlations of coastal land use along the sea–land direction. Therefore, we developed a model, called sequence–based clustering of coastal land use pattern (SCCLUP), to mine the coastal land use sequence patterns (CLUSPs) along the sea–land direction. As a case study in the major coastal zone of Bohai Bay and the Yellow River Delta from 1990 to 2010, we found that: (1) The land use showed a sequential distribution along the sea–land direction. And the land use closed to shoreline and inland boundary had relative stable sequential location along the sea–land direction. However, the middle land uses had dynamic sequential locations that led to multiple CLUSPs; (2) due to the increasing percent of construction land, the artificial level of CLUSPs was continuously increasing and new CLUSPs tended to distribute around port areas. Different CLUSPs with similar land use sequential relationships tended to have similar land use structure along the sea–land direction; (3) the land uses sequential location along the sea–land direction revealed the actual distance of land use to the shoreline and had a tight correlation with environmental factors (salinity, water, and landform). The land use with large increasing and wide adaptivity (like construction land) had a large impact on the changes of CLUSPs in the study area. Therefore, strong control should be provided for the excessive expansion of land use like construction land to limit the over changes in land use pattern along the sea–land direction. Additionally, the spatial heterogeneity of land use along the sea–land direction should be considered to a better understanding of anthropic impacts on the coastal zone.

Variations in Soil Bacterial Composition and Diversity in Newly Formed Coastal Wetlands

Coastal ecosystems experience some of the most active land–ocean interactions in the world, and they are characterized by high primary productivity and biological diversity in the sediment. Given the roles of microorganisms in soil biogeochemical cycling and their multifaceted influence on soil ecosystems, it is critical to understand the variations and drivers of soil microbial communities across coastal ecosystems. Here, we studied soil bacterial community dynamics at different sites (from seawater to freshwater) in the Yellow River Delta, China. Bacterial community composition and diversity over four seasons were analyzed through 16S rRNA genes. Notably, the bacterial community near the ocean had the lowest alpha-diversity when compared with the other sites. No significant differences in bacterial communities among seasons were found, indicating that seasonal variation in temperature had little influence on bacterial community in the newly formed wetlands in the Yellow River Delta. Bacterial community structure changed substantially along the salinity gradient, revealing a clear ecological replacement along the gradual transformation gradient from freshwater to seawater environment. Redundancy analysis revealed that salinity was the main driver of variations in bacterial community structure and explained 17.5% of the variability. Our study provides a better understanding of spatiotemporally determined bacterial community dynamics in coastal ecosystems.

Residues and sources of organochlorine pesticides in soils of elementary schools and communities in Wenchuan 5.12 Earthquake-affected areas

The disinfectants and pesticides extensively used after Wenchuan 5.12 Earthquake on May 12, 2008 (so-called Wenchuan 5.12 Earthquake), for epidemic prevention purpose can raise great concerns of environmental pollution and potential personal exposure. To investigate the soil pollution caused by the intensive application in earthquake-affected areas, surface soil samples from two elementary schools, two communities and two background areas were collected in Beichuan County and Dujiangyan City once per location in spring and in autumn in 2011 and then analyzed by gas chromatography/mass spectrometry for organochlorine pesticides (OCPs). The results showed serious soil pollution of hexachlorocyclohexanes (HCHs, 0.05-60.05 ng/g) and dichloro-diphenyl-trichloroethane (DDTs, 0.06-35.79 ng/g) in the study areas compared with Wolong Nature Reserve (0.03-0.81 ng/g for HCHs and 0.02-0.40 ng/g for DDTs). The concentrations of most OCPs in soil of Beichuan County (e.g., 0.10-60.05 ng/g for HCHs and 0.17-35.79 ng/g for DDTs) were much higher than those of Dujiangyan City (e.g., 0.05-20.58 ng/g for HCHs and 0.06-10.69 ng/g for DDTs). In Beichuan County, the highest concentrations of HCHs and DDTs were found in the elementary school. In Dujiangyan City, the highest concentrations of HCHs and DDTs were found in the elementary school and the community, respectively. The concentrations of HCHs and DDTs were generally higher in spring than those in autumn. The predominant species (γ-HCH in ∑HCHs and 4,4'-DDT in ∑DDTs) and specific ratios suggested new inputs of lindane and technical DDT in the study areas. Therefore, continuous soil monitoring and possible intervention would be recommended to minimize local residents' exposure to these toxic chemicals.

Organic contamination and remediation in the agricultural soils of China: A critical review

Soil pollution is a global problem in both developed and developing countries. Countries with rapidly developing economies such as China are faced with significant soil pollution problems due to accelerated industrialization and urbanization over the last decades. This paper provides an overview of published scientific data on soil pollution across China with particular focus on organic contamination in agricultural soils. Based on the related peer-reviewed papers published since 2000 (n=203), we evaluated the priority organic contaminants across China, revealed their spatial and temporal distributions at the national scale, identified their possible sources and fates in soil, assessed their potential environmental risks, and presented the challenges in current remediation technologies regarding the combined organic pollution of agricultural soils. The primary pollutants in Northeast China were polycyclic aromatic hydrocarbons (PAHs) due to intensive fossil fuel combustion. The concentrations of organochlorine pesticides (OCPs) and phthalic acid esters (PAEs) were higher in North and Central China owing to concentrated agricultural activities. The levels of polychlorinated biphenyls (PCBs) were higher in East and South China primarily because of past industrial operations and improper electronic waste processing. The co-existence of organic contaminants was severe in the Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei Region, which are the most populated and industrialized regions in China. Integrated biological-chemical remediation technologies, such as surfactant-enhanced bioremediation, have potential uses in the remediation of soil contaminated by multiple contaminants. This critical review highlighted several future research directions including combined pollution, interfacial interactions, food safety, bioavailability, ecological effects, and integrated remediation methods for combined organic pollution in soil.

Legacy and emerging halogenated flame retardants in the middle and lower stream of the Yellow River

Halogenated flame retardants (HFRs), mainly encompassing polybrominated diphenylethers (PBDEs), dechlorane plus (DP) and emerging bromine flame retardants (EBFRs), are widely employed nowadays in daily lives. However, limited knowledge has been gained to date on the concentrations and distributions of HFRs in particular within certain regions. In the present study, legacy and emerging HFRs were systematically measured in suspended particle matter (SPM) and sediments collected in 2014 from the middle and lower reach of the Yellow River in Henan province. The total concentrations of HFRs in SPM among the three seasons were 42.2±91.2ngg^-1, which was far higher than the corresponding values of HFRs in sediments (1.82±2.94ngg^-1). In this study, PBDEs, DP and EBFRs in sediment almost exhibited relatively lower levels as compared to those found in other studies, where the limited usage of HFRs in the middle and lower stream of the Yellow River was probably the major impact factor. EBFR was the predominate pollutant from SPM and sediments in most of the sampling sites, suggesting that EBFRs were widely used nowadays as substitute materials of 'old' FRs. The mean concentration values of DBDPE/BDE-209 in SPM and sediments were apparently higher than those of previous studies. Furthermore, it is interesting to reveal that herein almost all of the HFR concentrations were unrelated to the population and GDP, which might be attributed to the characteristics of 'elevated stream' of the Yellow River as well as the complex river systems in Henan province.

The complete genome of Ziziphus jujuba cv. dongzao, an economic crop in Yellow River Delta of China

The complete chloroplast genome of Ziziphus jujuba cv. dongzao, known as an important economic cultivar in Yellow River Delta of China was reported. It exhibits a quadripartite structure with 161,493 bp including a large single copy region (89,178 bp), a small single copy region (19,357 bp) and a pair of inverted repeats regions (26,479 bp). It has 36.79% GC content and 114 unique genes. Phylogenetic analysis showed that it was a member of Ziziphus and more closely related to Berchemiella wilsonii. Border analysis revealed that there were some differences in the borders of the four related cultivars.

Occurrence, enantiomeric signature and ecotoxicological risk assessment of HCH isomers and DDT metabolites in the sediments of Kabul River, Pakistan

Hexachlorocyclohexane (HCH) isomers and dichlorodiphenyltrichloroethane (DDT) metabolites were analyzed in sediments of three different depths (0-10, 10-20 and 20-30 cm) collected from Kabul River, Pakistan, in February 2014. The occurrence levels, enantiomer fractions and potential ecological risk of these organochlorine pesticides (OCPs) were evaluated. The total concentrations of ∑HCHs and ∑DDTs in surface sediments ranged from 4.9-23.9 ng g^-1 and from 6.4-18.8 ng g^-1 (dry weight basis), respectively. The vertical contamination profile of DDTs was found in order of 20-30 cm >10-20 cm >0-10 cm, indicated that the residue levels of DDTs gradually decreased after it was banned. The ratios of β-HCH/HCHs ranged from 0.04 to 0.73 (69 % of samples below 0.5) suggesting the fresh input of HCHs, while isomeric ratios of α-HCH/γ-HCH (ranged from 0.02 to 7.94), with 76 % of samples less than 3, indicating the cocktail use of technical grade HCH and lindane in the study area. The ratio of (DDE + DDD)/DDTs (ranged from 0.42 to 0.90) indicated long-term biodegradation of parent DDT. The enantiomer of α-HCH was generally racemic or close to racemic for most of the samples, with enantiomeric fraction (EF) value <0.5 for some of the samples indicated the preferential biodegradation of (+)-α-HCH enantiomer, while for o,p'-DDT the EF values >0.5 indicated the depletion of (-)-o,p'-DDT enantiomer in most of the samples. According to sediment quality guidelines (SQGs), HCH contamination is the main concern for ecotoxicological risk in Kabul River.

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

Nepal is a landlocked country located between world's two most populous countries-India and China where high level of organochlorines pesticides has been reported from multi-environmental matrices. In this study, we investigated the occurrence, distributions and profile of selected OCP chemicals in surface soil samples (N=72) from four major cities of Nepal. Overall, the sum of total OCPs in soil ranged from 20 to 250ng/g with Biratnagar being the most polluted site in Nepal. DDTs and endosulfans were the most abundant OCP chemicals in soil samples. The concentration of DDTs ranged from 8 to 230ng/g, 8-56ng/g, 8-63ng/g, and 8-27ng/g in surface soil, while endosulfans were in the range of 2.9-3.3ng/g, 2.8-8.7ng/g, 2.8-3.4ng/g, 2.8-3.2ng/g in Biratnagar, Kathmandu, Pokhara and Birgunj, respectively. The isomeric ratio of DDT and their metabolites suggested the ongoing usages of technical DDT as well as dicofol in this region. Lower ratio of α/β-endosulfan indicated past application of endosulfans in Nepal. HCHs were less detected OCPs in soil sample accounting only 4-9% of ∑OCPs. The isomeric ratio of α-/γ-HCH indicated that the HCHs may be originated from mixed source of technical HCH as well as lindane use. Scattered plot of TOC and BC showed they were weakly and positively related with concentration of OCPs in soil. Health risk assessment modeling study of OCPs in soil suggested moderate cancer risk with ingestion being the most potential pathway of OCPs exposure.