Hexachlorocyclohexane Residues Research Articles

Hydrogeochemical analysis of processes affecting HCH removal using ZVI-based treatment technology

In the 1960s, ca. 3000–5000 tons of HCH residue were disposed of in an overburden dump at the Hájek kaolin/uranium mine site (Czech Republic). The dump leachate, which has a 136 μg/l average total content of hexachlorocyclohexane (HCH) isomers, discharges into a local creek and contaminates the ecosystem. A full-scale prototype for the treatment of dump leachate comprised three sequential stages: 1) permeable reactive modules filled with macro-zerovalent iron (mZVI), 2) a biosorption module and 3) an aerobic wetland module. After commissioning, HCH removal efficiency reached 95%, but decreased to 70% over the following 230 days, primarily due to the efficiency of the mZVI modules dropping from 76% to 39%. Hydrogeochemical analysis and geochemical modelling revealed that the reduction in efficiency was mainly caused by passivation of mZVI surfaces and clogging of mZVI pore spaces through precipitation of goethite, calcite and rhodochrosite, or siderite and magnetite instead of goethite where boundary conditions for O2 differed. XRD analysis of the solid phase from the mZVI modules confirmed the geochemical modelling results. The major part of the precipitated products (46–66 wt%) comprised a ferric hydroxide amorphous phase, especially in the initial mZVI module inlet, with goethite the second most abundant precipitate (10–40 wt%). Siderite and calcite also mainly precipitated in the initial module inlet. In conclusion, mZVI appears to be a suitable reductant for HCH; however, the longevity of the ZVI-based treatment system was negatively affected by precipitates in the presence of high concentrations of iron, manganese and carbonate species.

Lindane degradation potential of methanotrophs and soil microbial biomass from HCH contaminated sites

In the present study, soil physico-chemical properties, hexachlorocyclohexane (HCH) isomers, lindane degrading soil methanotrophs and soil microbial biomass-C, N and P were investigated by selecting 6 study sites in Lucknow and Renukoot region of Uttar Pradesh, Northern India. The ANOVA revealed significant variations soil physico-chemical properties (P<0.001), HCH residues concentrations (P<0.001) and lindane degradation by soil methanotrophs (P<0.001), across different study sites. The GC and GC-MS/MS analysis revealed soil contamination by α, β-, γ-, and δ-HCH, along with organochlorine pesticides (OCPs) including aldrin, β-endosulphan, and dichlorodiphenyltrichloroethane (DDT). The concentration of soil HCH isomers (0.43-310.97 μg g−1) was higher in the soil samples of Lucknow region, compared to the Renukoot (0.12–194.44 μg g−1) region. These results depict that methanotrophic isolates SBRJS01, SBIJS02 and SBJS03 compared to control, showed better growth at selected environmental parameters. During lindane degradation the maximum Cl− release among the methanotrophic isolates showed the trend as SBJS03> SBRJS01> SBIJS02> ControlURRH3. A positive linear relationship (R2=0.7951) was noted between lindane degradation and Cl− release during the methanotrophic isolates incubation period. A greater SMB–C, –N and –P values (365.2, 65.5, and 26.8 μg g−1 soil, respectively), having higher HCH residues were, recorded in the soil samples of Renukoot region, compared to the soils of Lucknow region.The negative correlation between SMB–C, –N, and –P values and different soil HCH isomers suggests that higher concentrations of lethal HCH residues persisting in soils negatively impacts the quantity of soil microbial biomass. Therefore, on-site monitoring and methanotrophic mediated bioremediation of HCH soil residues might be a viable and eco-friendly option in removal of this particular persistent soil pesticide from the contaminated area.

Reduced attention on restricted organochlorine pesticides, whereas still noteworthy of the impact on the deep soil and groundwater: a historical site study in southern China.

The use of hexachlorocyclohexanes (HCHs) in pesticides has been prohibited for decades in China. Since then, there have been urbanization and transformation of the functional areas of many sites, which were formerly involved in the HCH industry. However, it is possible that, unless properly managed, these sites may still contain HCH residues in the soil and thus pose a threat to the surrounding environment and the quality of groundwater. This study aimed to characterize soil residues in a typical site that was historically involved in HCH production in southern China, by analyzing the α-HCH, β-HCH, and γ-HCH contents of the soil. The results suggested that HCHs persist in the environment and can have long-term effects. It was found that α-HCH and β-HCH were present in many samples in concentrations that were comparable or higher than those specified by China's Class 1 screening values. The distribution of residues was significantly correlated with the historical HCH production activities in the areas. The characteristic ratios of α-HCH/γ-HCH and β-HCH/(α + γ)-HCH at different soil depths were 1.4-3.7 and 0.21-1.04, respectively, which indicated the presence of significant localized residues of HCHs. The presence of HCHs in the soil suggested a downward migration, with concentrations rapidly decreasing in the upper layer soil (0-5m), but a gradual increase in the deeper soil (5-14m). HCHs were detected at depths exceeding 24m, indicating heavy penetration. The proportions of γ-HCH and β-HCH changed with increasing soil depth, which was related to their relatively volatile and stable molecular structures, respectively. The results strongly suggested that there is widespread contamination of both soil and groundwater by HCHs even after decades. The likelihood of residual HCHs in the soil should therefore be taken into full consideration during urban planning to limit risks to human and environmental health.

Spatial redistribution and enantiomeric signatures of hexachlorocyclohexanes in Chinese forest soils: Implications to environmental behavior and influencing factors

Hexachlorocyclohexanes (HCHs) are a group of highly persistent pesticides. The concentrations of HCHs and the enantiomeric fractions of α-HCH in the O- and A-horizons from 30 mountains across China were analyzed in this study. The concentrations of total HCHs ranged from 0.061 to 46.9 ng/g (mean 2.12 ng/g) and 0.046 to 16.1 ng/g (mean 0.792 ng/g) in the O- and A-horizons, respectively. The HCH residues were mainly derived from the historical applications of technical HCH and lindane. Higher concentrations of HCHs were typically found in northern China, and no significant correlations were found between historical technical HCH usage and HCH isomer concentrations in either the O- or A-horizons (p > 0.05). Conversely, the concentrations of HCH isomers were significantly correlated with the environmental parameters (temperature and precipitation), thus indicating a typical secondary distribution pattern. Some HCH isomers tended to be transported northward under the long-term effect of monsoon. Chiral α-HCH was non-racemic in soils and showed preferential degradation of (−) α-HCH in both the O- and A-horizons. The transformation from γ-HCH to α-HCH might alter the enantiomeric signatures of α-HCH in soils. Moreover, the deviation from racemic of α-HCH was positively correlated with the C/N ratio in the A-horizon (p < 0.01), thus suggesting that the C/N ratio could alter the microbial activity and significantly affect the enantioselective degradation extent of α-HCH in soils.

Analysis of Pollution Characteristics and Sources in Surface Water in Typical Crop-Producing Areas of Qinghai Province

Currently used pesticides and organochlorine pesticides (OCPs), nitrogen and phosphorus were analyzed in surface water from 26 sampling sites of agricultural areas in Qinghai Province to elucidate their pollution characteristics and sources. The results showed that most of these currently used pesticides, with the exception of chlorpyrifos, were generally not detected. However, two OCPs were commonly detected in surface water from four typical crop-producing areas. The residual concentrations of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) measured 0~1.68 ng/L and 0.41~2.41 ng/L, respectively, in the water from the four crop-producing areas. The residues of these two OCPs pesticides were much lower than the standard limit of surface water environmental quality. The main forms of HCHs and DDTs were β-HCH and pp'-DDE, respectively, indicating that the residues of HCHs and DDTs in the surface water of the four crop-producing areas in Qinghai were mainly derived from historical drugs that had degraded for a long time. The average concentrations of TN, NO3--N and NH4+-N in the surface water of 26 sampling sites of four typical crop areas in Qinghai Province were 2.95, 1.71 and 0.17 mg/L, respectively. According to the national surface water environmental quality standards, TN concentrations in 57.7% of these sampling sites exceeded the Class V water standards. The average concentration of NO3--N was more than 70 times that of NH4+-N. Nonetheless, there were no significant differences in the concentrations of TN, NO3--N and NH4+-N in the four crop-producing areas. The concentrations of NO3--N and NO3--N in the surface water were positively correlated with the TN concentration (p < 0.05), indicating that the sources of nitrogen in the surface water were relatively consistent. The average value of TP concentrations in the surface water from these sampling sites was 0.034 mg/L, with no significant differences among different producing areas. The N/P values in surface water from the four crop-producing areas of Qinghai Province had a range of 9.2~302. Phosphorus was the limiting factor for the proliferation of plankton in water. Reducing the input of phosphorus in these areas may be the key to preventing the deterioration of water quality. Significant negative and positive correlations exist between HCHs and nitrate nitrogen, and total phosphorus, respectively, which may be attributed to the proliferation of degrading microorganisms caused by the eutrophication of water. The research results will help to identify the characteristics and sources of surface water pollution in the crop-producing areas of Qinghai Province, and provide data support for Qinghai Province to build an export area for green organic agricultural and livestock products.

Correlation of HCH Residues Levels and Metagenomic Lin Protein Sequences at Contaminated Sites

The residue level of hexachlorocyclohexane (HCH) at contaminated dumpsites and nearby or related sites were studied. Water samples and sediments were collected from different HCH contaminated sites for residue analysis. These different sites include solexa data of dumpsite, Ummari, Lucknow (U.P.) (SolexaDS), dumpsite (DS) and two samples at the pond sediments near the pesticide industry, Chinhat, Lucknow (U.P.) (PS1 and PS2). 1km and 5km away from the DS i.e., 1km and 5km respectively were also included in the study. There was a correlation of HCH residue concentration at different sites with LinA and LinB protein distribution. Further, to investigate prevalence of LinA and LinB protein sequences in the metagenomic data sets of sites with different HCH gradients, a gene-centric approach was used. The study showed that in HCH stressed niches, LinA and LinB sequences from the metagenomes were found to cluster, thereby providing evidence in support of the proposed evolution of these proteins in the HCH contaminated environment.

The exposure to hexachlorocyclohexane in the human organism and in the environment: transformative actions

Introduction: According to Ministry of Health reports produced between 2001 and 2002, the presence of Hexachlorocyclohexane isomers was detected in the blood serum of the population of Cidade dos Meninos. After two decades, there is still no definitive solution to the problem, about 2,000 people continue to live in the region, exposed to the toxic substances. The objective of this study is to analyze the environmental impact of contamination by Hexachlorocyclohexane, with emphasis on the health of the population of this region. Methodology: Literature review, carried out in a non-systematic way in the period from September 2021 to March 2022. Studies were searched in scientific databases: Portal regional da BVS, Medline, Lilacs, Scielo, Pubmed using the descriptors: HCH, Drill Dust, Hexachlorocyclohexane, Pesticide, Organochlorine Compound, Cidade dos Meninos. The data were complemented with the analysis of the list of references of the selected articles. This research was conducted according to the principles established in resolution 466/12 of the National Health Council. The study protocol was submitted and approved by the Research Ethics Committee of the Universidade Iguaçu. Results: The persistence of contamination by Hexachlorocyclohexane and the difficulties of access to health care of the affected population were observed.Discussion: The results of the various research analyzed, are decisive indicators of the need to develop agro-environmental measures to deal with the residues of Hexachlorocyclohexane in the contaminated area seeking an option to decontaminate the site. It is also necessary to provide monitoring in the area of health, in parallel with a process of awareness-raising of the residents in relation to the risks to which they are exposed. Conclusion: The City of Boys has been suffering the consequences of environmental and human contamination by Hexachlorocyclohexane for half a century. An interdisciplinary approach is needed in the areas of education, health and environment, strengthening efforts to reduce the impact of contamination on the environment and on the lives of this population.

Orizontal transfer of haloalkane dehalogenase (LinB) gene among novel hexachlorocyclohexane (HCH) degrading sphingomonads isolated from contaminated soil

Soil samples from a HCH dump site and agricultural fields were collected from northern part of India in order to determine residue levels of a-, b-, g- and d- HCH and distribution of HCH degrading sphingomonads. The concentration of HCH residues was found to be very high in dump site soil (upto 4252.47µg/g) but it was low in the soil collected from the agricultural lands (upto 7.7µg/g). Eight novel HCH degrading strains could be isolated from HCH dump site soil but none from agricultural soil. Southern blot hybridization studies revealed the presence of haloalkane dehalogenase (LinB) genes alongwith IS6100 mobile genetic element in all of these strains. Further, 16S rDNA based phylogenetic analysis showed that these strains belong to the genus Sphingobium of family sphingomonadacae. An evidence for horizontal transfer of linB gene among these novel sphingomonads (only five were analysed) was derived by phylogenetic incongruency based approach. The sequence analysis of linB gene of novel isolates showed high sequence similarity (&gt;98.9 to 100%) with each other indicating they were the homologs of same gene. Comparison of “species tree” with “linB gene tree” revealed incongruency among both the trees thus proving that this gene has disseminated among these novel sphingomonads in a recent HGT event. Presence of IS6100 element in all the strains further supported the evidence. This study reveals that the members of family sphingomonadacae are acquiring lin genes by horizontal transfer under high selective pressure of HCH and such phenomenon at a contaminated site is quite significant for bioremediation of HCH.

Impact of hexachlorocyclohexane addition on the composition and potential functions of the bacterial community in red and purple paddy soil

Soil studies have reported the effect of Hexachlorocyclohexane (HCH) on soil microbial communities. However, how soil microbial communities and function shift after HCH addition into the red and purple soil remains unclear. Here, we analyzed the HCH residue fate, and the functional composition and structure of microbial communities to HCH in the two soils. Under the 100 g/ha and 1000 g/ha treatment, the dissipation rate of HCH was 0.0386 and 0.0273 in the purple soil, 0.0145 and 0.0195 in the red soil. The enrichment of HCH degrading genes leads to a higher HCH dissipation rate in the purple soil. PCoA results demonstrated that HCH addition has a different effect on the community diversity in the two soils, and Proteobacteria and Acidobacteria were the major phyla in the two soils. The soil microbiome average variation degree values of red soil were higher than purple soil, which indicated that the soil microbiome in the purple soil was more stable than in the red soil under HCH addition. PICRUSt2 results indicated that functional genes involved in the carbon, nitrogen biogeochemical cycles and HCH degradation were more tolerant to HCH addition in the purple soil. This study provides new insights into understanding of the effect of HCH addition on soil microbial communities and function in the red and purple paddy soil.

Plants exert beneficial influence on soil microbiome in a HCH contaminated soil revealing advantage of microbe-assisted plant-based HCH remediation of a dumpsite

Persistence of hexachlorocyclohexane (HCH) pesticide is a major problem for its disposal. Soil microflora plays an important role in remediating contaminated sites. Keeping concepts of microbial- and phyto-remediation together, the difference between soil microflora with and without association of HCH accumulating plant species was studied. Metagenomic analysis among the non-plant soil (BS) (∑HCH 434.19 mg/g), rhizospheric soil of shrubs (RSS) (∑HCH 157.31 mg/g), and rhizospheric soil of trees (RSD) (∑HCH 105.39 mg/g) revealed significant differences in microbial communities. Shrubs and trees occurred at a long-term dumpsite accumulated α- and β- HCH residues. Plant rhizospheric soils exhibited high richness and evenness with higher diversity indices compared to the non-plant soil. Order Rhizobiales was most abundant in all soils and Streptomycetales was absent in the BS soil. Proteobacteria and Ascomycota were highest in BS soil, while Actinobacteria was enriched in both the plant rhizospheric soil samples. In BS soil, Pseudomonas, Sordaria, Caulobacter, Magnetospirillum, Rhodospirillum were abundant. While, genera Actinoplanes, Streptomyces, Bradyrhizobium, Rhizobium, Azospirillum, Agrobacterium are abundant in RSD soil. Selected plants have accumulated HCH residues from soil and exerted positive impacts on soil microbial communities in HCH contaminated site. This study advocates microbe-assisted plant-based bioremediation strategy to remediate HCH contamination.

Comparative proteomics unravelled the hexachlorocyclohexane (HCH) isomers specific responses in an archetypical HCH degrading bacterium Sphingobium indicum B90A.

Hexachlorocyclohexane (HCH) is a persistent organochlorine pesticide that poses threat to different life forms. Sphingobium indicum B90A that belong to sphingomonad is well-known for its ability to degrade HCH isomers (α-, β-, γ-, δ-), but effects of HCH isomers and adaptive mechanisms of strain B90A under HCH load remain obscure. To investigate the responses of strain B90A to HCH isomers, we followed the proteomics approach as this technique is considered as the powerful tool to study the microbial response to environmental stress. Strain B90A culture was exposed to α-, β-, γ-, δ-HCH (5 mgL-1) and control (without HCH) taken for comparison and changes in whole cell proteome were analyzed. In β- and δ-HCH-treated cultures growth decreased significantly when compared to control, α-, and γ-HCH-treated cultures. HCH residue analysis corroborated previous observations depicting the complete depletion of α- and γ-HCH, while only 66% β-HCH and 34% δ-HCH were depleted from culture broth. Comparative proteome analyses showed that β- and δ-HCH induced utmost systemic changes in strain B90A proteome, wherein stress-alleviating proteins such as histidine kinases, molecular chaperons, DNA binding proteins, ABC transporters, TonB proteins, antioxidant enzymes, and transcriptional regulators were significantly affected. Besides study confirmed constitutive expression of linA, linB, and linC genes that are crucial for the initiation of HCH isomers degradation, while increased abundance of LinM and LinN in presence of β- and δ-HCH suggested the important role of ABC transporter in depletion of these isomers. These results will help to understand the HCH-induced damages and adaptive strategies of strain B90A under HCH load which remained unravelled to date.

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 8.88µg/g in soil, nd -5.87µg/l in water and nd - 4.87µg/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.

Status, Sources, and Health Risk of Hexachlorocyclohexanes in the Air of the Rural Region of Zhangzhou, Southeast China

From October 2012 to September 2013, air samples of hexachlorocyclohexanes (HCHs) were collected by polyurethane foam passive air samplers (PUF-PAS) from Caiban Village (CbV), Baihua Village (BhV), Bumeishan Village (BmsV) and Qitang Village (QtV), located in the rural region of Zhangzhou, Southeast China. The test results showed that four HCH isomers (α-, β-, γ-, δ-HCH) were ubiquitous with ∑HCHs concentrations ranging from 4.80 to 41.9pg/m3 and a mean value of 17.7pg/m3. A seasonal variation was established in the air HCH levels. The highest ∑HCHs concentration was observed in the autumn whereas the lowest was detected in the spring. The ratio α/γ-HCH, which was used to identify the contamination source, revealed that air HCHs originated mainly from historical technical HCH residues and lindane usage. The health risk of inhalation exposure to atmospheric HCHs, assessed by the inhalation dosimetry methodology, was low and considered negligible for the local residents.

History traces of HCHs and DDTs by groundwater dating and their behaviours and ecological risk in northeast China

Organochlorine pesticides legacies, such as hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), remained in sediments or soils due to their difficulty in decomposition, especially in the agricultural areas where pesticides were widely used historically. Different from the little disturbed depositional environment of lake, it was difficult for rivers to explore the timing of DDT and HCH inputs through dating sediment cores as records. Based on groundwater dating, this study ascertained the historic pollution of DDT and HCH in Taizi River basin. HCH and DDT residues in groundwater were consistent with the historical production and usage, which increased from the 1950s to the 1980s and declined from the 1980s to the 1990s. Moreover, the partitioning behaviours of HCHs and DDTs in surface water and suspended particulate matter were discussed. It was revealed that β-HCH and o,p’-DDT were more likely to attach to suspended particulate matter than other isomers. Furthermore, species sensitivity distribution curves were generated using 54 toxicity data records to assess the risk of HCHs and DDTs in water and suspended particulate matter. These results indicated that p,p’-DDT in surface water posed a high risk to 95% of the aquatic life in the long run.

Effects of electron donors on the degradation of hexachlorocyclohexane and microbial community in submerged soils

PURPOSE: Hexachlorocyclohexane (HCH) is a pesticide that is persistent in aerobic but not in anaerobic conditions. The aim of this investigation was to elucidate the impacts of different electron donors on the degradation of hexachlorocyclohexane and their relationships with the microbial community in submerged soils. MATERIALS AND METHODS: Soil samples were collected from a pesticides-polluted site which was previously used for long-term storage of pesticides since the 1960s. Residual amounts of HCHs in submerged soils were assessed to evaluate the efficiency of the added electron donors after incubation. Changes in microbial community were monitored during incubation. RESULTS AND DISCUSSION: The efficiencies of removal of HCHs by Fe⁰, Fe⁰ + straw and glucose treatments were 63.8%, 40.3%, and 22.0%, compared with 5.4% by the control. Soil redox potential decreased rapidly following addition of Fe⁰ and became anaerobic, but there was no significant decrease in redox potential following the addition of glucose. Principal coordinates analysis (PCoA) confirms that the electron donors greatly affected the soil bacterial community. Furthermore, community composition analysis shows that Firmicutes was the dominant phylum after addition of carbon sources (straw and glucose) but Proteobacteria were dominant in the control and the Fe⁰ treatment. Prauserella, Actinobacteria, and Streptomyces showed highly significant increases in the Fe⁰ treatment and were positively correlated with total HCH residues. CONCLUSIONS: These findings indicate that the addition of organic materials (straw and glucose) had a gradual effect on the degradation of HCH while Fe⁰ acted rapidly. Elucidation of the relationships between electron donors and soil microbial communities will help in the bioremediation of HCH-contaminated sites.

Concentration, characterization and risk assessment of polycyclic aromatic hydrocarbons and organochlorine pesticides in soils from the Corn Belt of northeast China

AbstractOrganic contaminants in agricultural soils are widely reported; however, their accumulation patterns are quite different among regions. This study reports the distribution, accumulation and risk assessment of polycyclic aromatic hydrocarbons (PAHs), dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) in soils from the Corn Belt of northeast China at a regional scale. Concentrations of PAHs, DDT and HCH were 306‐5300, 6.00–82.0 and 4.07–15.6 ng g−1, respectively. Source analysis suggests PAHs were derived from regional combustion of biomass and coal, except where sites are strongly affected by local sources. The DDT and HCH residues in soils are likely to be derived from previous agricultural applications that have persisted due to slow microbiological degradation under low mean temperatures. Precipitation was only significantly correlated with PAH concentrations, suggesting that precipitation affected PAH but not DDT and HCH distributions at a regional scale. Positive correlations between DDT concentrations and total organic carbon (TOC) contents of soils suggest hydrophobic organic contaminants were associated with organic matter. In contrast, TOC contents were correlated with PAHs in alfisols but not in pedocals. Pedocals contained mainly high molecular weight PAHs, indicating that eluviation affected the accumulation of less hydrophobic organic contaminants. Different correlations between low‐molecular‐weight PAH and HCH concentrations with TOC contents were found in alfisols, suggesting that contaminant structure may also affect the accumulation of less hydrophobic organic contaminants in these soils. Risk analysis suggested that potential ecological risks related to soils in the Corn Belt may lead to reduced maize production and the potential for human health risks in the future.Highlights Few studies focus on regional‐scale factors that affect organic contaminant accumulation in soils. Environmental process affects less hydrophobic organic contaminant distribution at regional scale. Precipitation and eluviation affected accumulation of less hydrophobic contaminants in soils. PAH and OCP residues in the soil of maize fields may pose ecological risks affecting future crop production and human health.

Occurrence and Human Health Risk of Dichlorodiphenyltrichloroethane (DDT) and Hexachlorocyclohexane (HCH) Pesticide Residues in Commonly Consumed Vegetables in Southwestern Nigeria.

Background.Fluted pumpkin (Telfairia occidentalis) and amaranth (Amaranthus spp.) are common leafy vegetables produced and consumed in southwestern Nigeria. These vegetables attract insect pests which are controlled by pesticides that may have adverse impacts on human health.Objectives.To determine the levels of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) pesticide residues in the two vegetables and evaluate the potential health risks associated with their consumption.Methods.The pesticide residue levels were quantitatively and qualitatively determined using a gas chromatograph coupled with electron capture detector. Health risk assessment were performed using estimated average daily intake and hazard indices for two weight categories: children (16.7 kg) and adults (60 kg).Results.The results showed that delta-HCH, DDT and methoxychlor were predominantly detected in the two vegetables from both farms and markets. In amaranth, the mean concentration of methoxychlor, DDT and delta-HCH were 4.590 ± 2.774 mg/kg (dry weight (dw)), 0.757 ± 0.457 mg/kg (dw) and 0.577 ± 0.390 mg/kg (dw), respectively, while fluted pumpkin levels were 6.223 ± 2.489 mg/kg dw (methoxychlor), 0.504 ± 0.056 mg/kg dw (delta-HCH) and 0.486 ± 0.123 mg/kg dw (DDT). The levels of HCH and DDT residues were generally above the United Kingdom/European Commission maximum residue limit. The analysis of health risk estimates for non-carcinogenic risk revealed that for both vegetables, the hazard quotient for p, p′ DDT and methoxychlor was >1 for both children and adults. The health risk estimates for carcinogenic risk revealed that hazard indices values were >1 for children for both vegetables and alpha-HCH had a hazard index >1 for adults for amaranth. This means the residue exceeds acceptable standard and present potential risk to consumers of these vegetables.Conclusions.The results obtained from the present study indicate that consumption of amaranth contaminated with alpha-HCH could pose a carcinogenic risk for adult consumers. The consumption of the two vegetables could pose both non-carcinogenic and carcinogenic health risks to children and adults. Therefore, there is need for strict enforcement of regulations on pesticide usage to minimize human health risks.Competing Interests.The authors declare no competing financial interests.

Distribution and Potential Risk of Organochlorine Pesticides in the Soil of a Submerged Area Around Miyun Reservoir

Soil samples collected from a submerged area around Miyun Reservoir were analyzed for organochlorine pesticide (OCP) residues using GC-MS. The distribution characteristics and possible sources of OCPs were studied, as well as the potential ecological risk. The results showed the following:① the residuals of OCPs in the surface soil were mainly hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs), and the average contents of HCHs and DDTs were 1.74 ng·g-1 and 1.01 ng·g-1, respectively. In comparison with other lakes and reservoirs in China, the mean value of DDT content of the soil samples from Miyun Reservoir was slightly less, whereas the mean value of HCH content was similar to other waterbodies. ② There was a distinct spatial distribution of OCPs in soils of the submerged area. Specifically, the OCP content in the water-land interlaced soil was generally higher, with distinct differences to the water or in land. In the eastern region of the reservoir and in the Chaohe River inflow area, the residues of OCPs were mainly DDTs, as was the case for the submerged soils of small isolated watersheds. The OCPs in the submerged area of the northern reservoir and the western central reservoir were mainly γ-HCH residues, while HCH and DDT residues were found in high proportions in the flooded area where the Baihe River inflows. These patterns were related to sources of pollutants; ③ the source analysis showed that sources of HCHs could be related to lindane input, while DDTs mainly derived from the early residues in the environment; ④ there was low ecological risk from OCPs in most of the samples, and a potential risk from DDT in the Baihe inflow area and in the central submerged zone of the western reservoir.

Isomerspecific determination of sorption/desorption, transformation and bioaccumulation of hexachlorocyclohexanes at the case site Bitterfeld with special regard to ageing effects

ABSTRACTThe production of hexachlorocyclohexanes (HCHs) at Bitterfeld, Germany, caused heavy contamination of sediments in the receiving waters and soils of riverbanks and floodplains of the Spittelwasser creek with adverse effects on the rivers Mulde and Elbe. This study was launched to investigate the isomer specific behaviour of aged and non-aged hexachlorocyclohexanes focusing on their transformation, sorption and bioaccumulation. Spiked residues of α- and γ-HCH were transformed in aerobic water/sediment systems, while no elimination was observed for β-, δ- and ε-HCH. In contrast, aged residues of all HCH isomers were entirely stable under these aerobic conditions, while under anaerobic conditions a significant transformation was found for all spiked HCH isomers. Desorption hysteresis was identified for all isomers. Ageing led to an increase in the binding strength of HCH isomers to sediment, indicated by elevated logKOC-values and increased the persistence of HCH isomers in aerobic water/sediment systems. HCH bioaccumulated in benthic organisms of Spittelwasser creek and Schachtgraben canal. After their confluence the lipid normalised HCH concentrations in benthic organisms of Spittelwasser creek increased by a factor of 10, indicating the central role of HCH residues from the Schachtgraben canal for the HCH exposure of benthic biota in the aquatic system of the Spittelwasser creek.

Residues of organochlorine pesticides (OCPs) in aquatic environment and risk assessment along Shaying River, China.

Organochlorine pesticides (OCPs) are pesticides with global scale ubiquity, persistence and bioaccumulation, which leave long-term residuals in the water body. OCPs' high toxicity poses significant threats to human health and aquatic biodiversity, making assessment of OCPs' impact on aquatic ecology and human health urgently necessary. In this research, the presence of 16 OCPs in surface water and groundwater along Shaying River, China, as well as OCPs concentration correlations, was investigated at 24 selected sampling sites. At the same time, the ecological risk and human carcinogenic risk were also analyzed by risk quotient method and USEPA's Risk Assessment Guidance, respectively. Results showed that the total concentration of OCPs ranged from 21.0 to 61.4ngL-1 in groundwater, and 12.3-77.5ngL-1 in surface water. Hexachlorocyclohexane (HCHs) and heptachlor were the prominent contaminants in groundwater, which indicated their use in the recent past and confirmed their persistence. The α-HCH/γ-HCH ratios in groundwater confirmed that γ-HCH (lindane) was used as main substitute of technical HCH in the study area. The correlation analysis illustrated that δ-HCH and γ-HCH played a dominant role in HCHs residue. Heptachlor and α-HCH, as well as endosulfan and heptachlor epoxide, had a strongly significant positive correlation, suggesting an associated usage of the two pair OCPs. An extremely high ecological risk for aquatic organism was observed for γ-HCH, heptachlor and dieldrin, while the carcinogenic risks posed by the selected OCPs in surface water and groundwater were all acceptable.