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Haloalkane dehalogenase, LinB, is a member of the α/β hydrolase family of enzymes. It has a wide range of halogenated substrates, but, has been mostly studied in context of degradation of hexachlorocyclohexane (HCH) isomers, especially β-HCH (5–12% of total HCH isomers), which is the most recalcitrant and persistent among all the HCH isomers. LinB was identified to directly act on β-HCH in a one or two step transformation which decreases its toxicity manifold. Thereafter, many studies focused on LinB including its structure determination using X-ray crystallographic studies, structure comparison with other haloalkane dehalogenases, substrate specificity and kinetic studies, protein engineering and site-directed mutagenesis studies in search of better catalytic activity of the enzyme. LinB was mainly identified and characterized in bacteria belonging to sphingomonads. Detailed sequence comparison of LinB from different sphingomonads further revealed the residues critical for its activity and ability to catalyze either one or two step transformation of β-HCH. Association of LinB with IS6100 elements is also being discussed in detail in sphingomonads. In this review, we summarized vigorous efforts done by different research groups on LinB for developing better bioremediation strategies against HCH contamination. Also, kinetic studies, protein engineering and site directed mutagenesis studies discussed here forms the basis of further exploration of LinB’s role as an efficient enzyme in bioremediation projects. [ABSTRACT FROM AUTHOR]

Purpose: Alkaline-thermal coupling activation of persulfate (PS) is an effective method for hexachlorocyclohexane (HCH) degradation. However, the process of this method requires high concentrations of NaOH and PS. Since HCH can be easily hydrolyzed into trichlorobenzene (TCB), in this study, we adopted the strategy of sequential addition of reagents (adding NaOH first and maintaining for 4 h before adding PS) and explored the effect of temperature and alkalinity on HCH hydrolysis and TCB oxidation, in order to develop a better degradation method for HCH which persists in the environment. Methods: Shake flask experiments were performed, which allowed for the examination of specific factors. The degradation of HCH was evaluated by measuring the concentrations of HCH and TCB during the reaction by gas chromatography. Results and discussion: It was found that high pH favored HCH hydrolysis but inhibited TCB oxidation. Almost no HCH degradation occurred under simultaneous addition (20 mM NaOH and 50 mM PS), while 80% of HCH was hydrolyzed within 4 h under sequential addition in soil. The results demonstrated that the concentration of alkali should be controlled and that sequential addition was more beneficial for the degradation of HCH, especially in the case of low alkali concentration. Moreover, the degradation efficiency was higher in soils with low soil organic matter (SOM) content, as SOM would affect PS and NaOH consumption and compete for radicals. Conclusion: This study provides practical information for future design of activated PS treatment for in situ remediation of HCH-contaminated environments. [ABSTRACT FROM AUTHOR]

Hexachlorocyclohexane (HCH) is one of the most widely used insecticides, which is included in the list of persistent organic pollutants. The genes involved in HCH degradation are known as lin genes. linA codes for the enzyme HCH dehydrochlorinase, which is a type of lyase dehalogenase and catalyzes the first step of dehydrochlorination of α-, γ- and δ-HCH. It is important to understand the phylogeny of lyase dehalogenases, as they are involved in the degradation of various xenobiotics. Lyase dehalogenases are underrepresented in the database. Homology search suggested that HCH dehydrochlorinase shares similarities with bile-acid 7-alpha dehydratase, scytalone dehydratase, ketosteroid isomerase, nuclear transport factor 2, and biphenyl 2,3 dioxygenase. This similarity is supported by secondary structure, homology modeling, and catalytic motif prediction. The catalytic site residues of HCH dehydrochlorinase are similar to bile-acid 7-alpha dehydratase and scytalone dehydratase. Dichloromethane dehalogenase shares homology with glutathione S-transferases and maleylacetoacetate isomerase. This similarity is further supported by the presence of similar glutathione binding sites and similar secondary structures. This study provides evidence that HCH dehydrochlorinase may have evolved from the enzymes having dehydratase activity and dichloromethane dehalogenase from the theta class of glutathione S-transferase. This study also identified key catalytic residues that can be mutated to make more efficient HCH and dichloromethane-degrading enzymes that can be used for enzymatic bioremediation. [ABSTRACT FROM AUTHOR]

This review elucidates different bioremediation approaches used for degradation of HCH from contaminated sites. It highlights the significance of degradative pathways, microbial diversity and impact of different environmental factors for developing viable bioremediation strategies. The application of innovative biotechnological approaches and a thorough understanding of HCH biodegradation pathways show great promise for the creation of long-term solutions to HCH pollution and the restoration of polluted soil ecosystems. Bioremediation technologies viz. biostimulation, bioaugmentation, phytoremediation have been considered till date for treating HCH-contaminated sites. Different bacterial and fungal strains have been reported for degradation of HCH residues. However, these methods are limited to γ-HCH degradation, at laboratory scale and achieving lower success rate for large scale demonstration trials. This review presents a theoretical background for degradation of different HCH isomers in soil through plants, microbes and through their cooperative interactions. This work briefly overviews the substantial contamination of the environment by HCH residues, along with spontaneous evolution of degradation pathways through various HCH degrading microbes. Bioremediation mechanism and pathways of HCH degradation through plants and microbes have been discussed thoroughly. Through molecular and genetic investigations, the complex metabolic pathways used by these microbes, including reductive dechlorination, hydrolysis, and ring cleavage, has been clarified. This study seeks to give a thorough summary of recent discoveries and developments in bioremediation methods for soil HCH degradation. Numerous microbial consortia, including fungi, plants, and bacteria have been recognised as important participants in the transformation of HCH. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Khat (Catha edulis) chewing is widespread in the region of East Africa. Even low levels of organochlorine pesticides (OCPs) in khat could induce public health concern. In a market-based study, from five popular khat varieties, a total of 35 composite khat samples were analyzed for dichlorodiphenyltrichloroethane (DDT) and its main transformation products, and four hexachlorocyclohexane (HCH) isomers. Extraction was carried out by quick, easy, cheap, effective, rugged and safe method (QuEChERS). OCP concentrations were determined by head space solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME–GC–MS). Every sample contained β-HCH above the maximum residue limit set by the European Commission. For total DDT, this was the case for 25.7% of the samples. The ratios of (p,p′-DDD + p,p′-DDE) to p,p′-DDT were less than one for 85% of khat samples, demonstrating recent use of DDT in khat farmlands. Conversely, the ratio of β-HCH to total HCH varied from 0.56 to 0.96, implying historical input of technical HCH. Assuming a daily chewable portion of 100 g, dietary intakes of p,p′-DDT, total DDT and total HCH by adults ranged from 3.12 to 57.9, 6.49 to 80.2 and 39.2 to 51.9 ng (kg body weight)−1 day−1, respectively. These levels are below acceptable levels suggested by international organizations. Chewing khat showed lower non-cancer health risk, but showed relatively higher cancer risk in terms of OCPs. Because khat is chewed without being subjected to any treatment, uncertainties associated with estimated intakes and health risks should be low. Therefore, this practice is of great concern. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, bioaugmentation and biostimulation were used to explore the efficiency of bioremediation of hexachlorocyclohexane (HCH)-contaminated soil in the laboratory. A complex microbial community (germ A, abbreviated as A) was used for bioaugmentation. The KNO3 and K2HPO4 (NP), wheat straw (JG), and glucose (PU) were used as exogenous amendments for biostimulation. Five treatments were set up: the control (CK), NP, A + NP, A + NP + JG, and A + NP + PU. After 28 days of remediation, the removal rate of total HCH (HCHs) in NP, A + NP, A + NP + JG, and A + NP + PU was 27.0%, 32.2%, 43.4%, and 45.3%, respectively. The results indicated that the removal of HCHs in A + NP, A + NP + JG, and A + NP + PU was higher than NP, indicating that bioaugmentation combined with biostimulation was more effective than biostimulation. Furthermore, compared with A + NP, A + NP + JG and A + NP + PU were more conducive to the degradation of HCHs. Because applying inorganic and organic nutrient substances simultaneously can effectively improve the living environment of microorganisms and increase microbial quantities in HCH-contaminated soil, therefore, the enzymatic reaction of microorganisms is accelerated, resulting in the efficiency of HCHs degradation improvement. The results indicated that bioaugmentation with germ A combine with biostimulation by organic and inorganic nutrients simultaneously constitutes a promising method for restoring soils contaminated with HCHs. This study would provide the basis for improving the bioremediation efficiency of HCH-contaminated soil. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The biotransformation of hexachlorocyclohexane isomers (HCH) by two Dehalococcoides mccartyi strains (195 and BTF08) and an enrichment culture was investigated and compared to conversion by the obligate anaerobic strain Clostridium pasteurianum strain DSMZ 525. The D. mccartyi strains preferentially transformed γ-HCH over α-HCH and δ-HCH isomers while β-HCH biotransformation was not significant. In case of the enrichment culture, γ-HCH was preferentially transformed over the δ-HCH, β-HCH and α-HCH isomers. Major observed metabolites in both cases were tetrachlorocyclohexene and as end products monochlorobenzene (MCB) and benzene. Dechlorination of the γ-HCH isomer was linked to an increase in cell numbers for strain 195. γ-HCH transformation was linked to considerable carbon stable isotope fractionation with the enrichment factor εc = − 5.5 ± 0.8‰ for D. mccartyi strain 195, εc = − 3.1 ± 0.4‰ for the enrichment culture and εc = − 4.1 ± 0.6‰ for co-metabolic transformation by C. pasteurianum. [ABSTRACT FROM AUTHOR]

The saprotrophic fungus Penicillium griseofulvum was chosen as model organism to study responses to a mixture of hexachlorocyclohexane (HCH) isomers (α-HCH, β-HCH, γ-HCH, δ-HCH) and potentially toxic metals (vanadium, lead) in solid and liquid media. The P. griseofulvum FBL 500 strain was isolated from polluted soil containing high concentrations of HCH isomers and potentially toxic elements (Pb, V). Experiments were performed in order to analyse the tolerance/resistance of this fungus to xenobiotics and to shed further light on fungal potential in inorganic and organic biotransformations. The aim was to examine the ecological and bioremedial potential of this fungus verifying the presence of mechanisms that allow it to transform HCH isomers and metals under different extreme test conditions. To our knowledge, this work is the first to provide evidence on the biotransformation of HCH mixtures, in combination with toxic metals, by a saprotrophic non-white-rot fungus and on the metabolic synergies involved. [ABSTRACT FROM AUTHOR]

Currently, there are large areas of soils contaminated with hexachlorocyclohexane (HCH) isomers which are included in the group of persistent organic pollutants. For the bioremediation of such soils, a new HCH-degrading Rhodococcus wratislaviensis strain Ch628 was isolated from long-term organochlorine contaminated soils. The strain Ch628 was able to degrade 32.3% γ-hexachlorocyclohexane (γ-HCH/lindane), 25.2% hexachlorobenzene, and 100% chlorobenzene in resting cell conditions. The strain Ch628 was bioaugmented in chronically HCH-contaminated soil. The results showed that the bioaugmentation of contaminated soil with the strain Ch628 led to HCH degradation. In the bioaugmented system, the efficiency of HCH removal at the initial concentration of about 238.7 ± 4.9 mg kg soil was 44.8%, while the system with indigenous microflora (without R. wratislaviensis strain Ch628) and the system with abiotic control removed 33.3 and 16.4% of this compound during the same period, respectively. Strain Ch628 could effectively degrade α-, β-, and γ-isomers of HCH (77.1, 100, and 100%, respectively) and heptachlorocyclohexane (69.9%) in the model soil systems. Moreover, the bioaugmentation with the strain Ch628 led to degradation of tri-, tetra-, and penta-chlorobenzenes, which are of HCH degradation metabolites. For the first time, it was found that the bioaugmentation with the bacterial strain Rhodococcus wratislaviensis Сh628 led to a significant reduction of the toxicity of the HCH-contaminated soil for the test organisms, such as Chlorella vulgaris Beijer and Daphnia magna Straus. [ABSTRACT FROM AUTHOR]

Assessment of biotic and abiotic degradation reactions by studying the variation in stable isotopic compositions of organic contaminants in contaminated soil and aquifers is being increasingly considered during the last two decades with development of Compound specific stable isotope analysis (CSIA) technique. CSIA has been recognized as a potential tool for evaluating both qualitative and quantitative degradation with measurement of shifts in isotope ratios of contaminants and their degradation products as its basis. Amongst a wide variety of environmental pollutants including monoaromatics, chlorinated ethenes and benzenes etc., it is only recently that its efficacy is being tested for assessing biodegradation of a noxious pollutant namely hexachlorocyclohexane (HCH), by pure microbial cultures as well as directly at the field site. Anticipating the increase in demand of this technique for monitoring the microbial degradation along with natural attenuation, this review highlights the basic problems associated with HCH contamination emphasizing the applicability of emerging CSIA technique to absolve the major bottlenecks in assessment of HCH. To this end, the review also provides a brief overview of this technique with summarizing the recent revelations put forward by both in vitro and in situ studies by CSIA in monitoring HCH biodegradation. [ABSTRACT FROM AUTHOR]

Hexachlorocyclohexane (HCH) contaminated soils were treated for a period of up to 64 days in situ (HCH dumpsite, Lucknow) and ex situ (University of Delhi) in line with three bioremediation approaches. The first approach, biostimulation, involved addition of ammonium phosphate and molasses, while the second approach, bioaugmentation, involved addition of a microbial consortium consisting of a group of HCH-degrading sphingomonads that were isolated from HCH contaminated sites. The third approach involved a combination of biostimulation and bioaugmentation. The efficiency of the consortium was investigated in laboratory scale experiments, in a pot scale study, and in a full-scale field trial. It turned out that the approach of combining biostimulation and bioaugmentation was most effective in achieving reduction in the levels of α- and β-HCH and that the application of a bacterial consortium as compared to the action of a single HCH-degrading bacterial strain was more successful. Although further degradation of β- and δ-tetrachlorocyclohexane-1,4-diol, the terminal metabolites of β- and δ-HCH, respectively, did not occur by the strains comprising the consortium, these metabolites turned out to be less toxic than the parental HCH isomers. [ABSTRACT FROM AUTHOR]

Various factors influence the isomeric composition of hexachlorocyclohexanes which are released to the environment. Original compositions in technical mixtures may vary slightly, but higher shifts are observable for transfer processes, bioaccumulation and microbial transformation. Consequently, the isomeric composition in environmental samples is a superposition of these processes. In this study, isomeric distributions and concentrations of hexachlorocyclohexanes were analyzed in water, sediment, and soil samples of a riverine system known to be highly contaminated by hexachlorocyclohexanes. To assess desorption of hexachlorocyclohexanes from particulate matter to water, batch shaking and percolation experiments were conducted complementary. Analyzed samples exhibited total hexachlorocyclohexane concentrations of up to 2.8 µg/g in sediments and up to 21 µg/L in river water predominated by the α-isomer. Downstream hexachlorocyclohexane pattern changed toward δ-isomer domination, while overall hexachlorocyclohexane concentrations decreased. Desorption experiments supported the assumption of discrimination by preferred association of the α- and β-isomers with particulate matter, showing elevated mobilization of γ-, δ- and ε-hexachlorocyclohexanes and lower mobilization of the α- and β-isomers. Soil samples of a riparian wetland exhibited elevated concentrations of hexachlorocyclohexanes exceeding 200 µg/g and predominance of α-hexachlorocyclohexanes in the top soil layer. Subjacent soil layers showed rapidly decreasing hexachlorocyclohexane concentrations and an isomeric shift toward the β-isomer. The assumed preferential mobilization of β-hexachlorocyclohexane was supported by desorption experiments. This study demonstrated firstly that transfer processes influence substantially hexachlorocyclohexane isomer distribution in the aquatic environment. Secondly, conditions of aging determine strength of association and remobilization potential of hexachlorocyclohexane residue down to an isomer-specific level. [ABSTRACT FROM AUTHOR]

To evaluate the effectiveness of the thermal remediation of soil decontamination, samples containing organochlorine insecticide hexachlorocyclohexane (HCH) were subjected to different temperatures depending on the exposure time. For this study, reference material and technical grade HCH were heated separately at β = 1 and 10 °C min in a thermogravimetric analyzer and contaminated soil samples were heated in an oven at different temperatures and heating time. To determine gaseous emissions generated during the heating of HCH isomers, HCH technical grade samples were heated in a closed system (reactor) and sample gases/vapors were collected for qualitative analysis. The results indicate that the contaminants are removed from soil to temperatures considerably lower than the respective boiling point. The thermogravimetric curves have shown that heating to 400 °C HCH results in fusion processes followed by evaporation, and investigating in the oven, the reduction in HCH concentration present in the contaminated soil depends on the temperature and length of heating. Gaseous emissions detected were from isomers of HCH, chlorine derivatives and benzene compounds. The laboratory tests show that parameters such as temperature, heating time and air flow can influence the thermal decontamination process of the subsoil. [ABSTRACT FROM AUTHOR]

In order to understand the interactions between beta-hexachlorocyclohexane (HCH) and chemical groups at activated carbon (AC) surface, the solid samples were hydrogenated aiming to decrease the amounts of oxygenated groups. Two AC samples designated by BagHO and BagP1.5 were prepared by water vapor activation and phosphoric acid activation, respectively, of sugarcane bagasse used as an AC precursor. A more simple molecule 1,2,3-trichloropropane (TCP) is used as a model of chlorinated compound. The AC were characterized by infrared, X-ray photoelectron spectroscopy (XPS), Raman resonance spectroscopies, as well as temperature-programmed desorption coupled with mass spectrometry (TPD-MS). BagP1.5 and BagHO AC surface contained oxygenated groups. Upon hydrogenation, a decrease of most of these group amxounts was observed for both samples, while hydroxyl groups increased. On the basis of temperature-programmed desorption data obtained for AC samples contaminated with TCP or HCH, it was possible to determine the type of hydrogen bond formed between each AC and HCH. [ABSTRACT FROM AUTHOR]

The content of organochlorine pesticides in blood of residents of the Russian Far East is assessed. Among hexachlorocyclohexane isomers, only β-HCH has been found. This fact indicates that contamination of the environment and human organisms by this pesticide began long ago. Its concentration varies from 2060 to 22,230 ng/g lipid. The probable sources of the toxicant found in human organisms are discussed. [ABSTRACT FROM AUTHOR]

This study reports data on the contents of organochlorine pesticides and heavy metals in the muscles and livers of eight individuals (five males and three females) of the Pacific walrus Odobenus rosmarus divergens Illiger, 1815, which were captured in the summer of 2011 in Mechigmensky Bay of the Bering Sea. Pesticides, namely α-, β-, and γ-isomers of hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its metabolites dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE), as well as the heavy metals Cd, Pb, and Hg were found in all samples studied. The total concentration of organochlorine pesticides in the muscles varied from 200 to 5700 ng/g lipid weight and in the liver from 4900 to 90300 ng/g lipid weight. The concentrations of cadmium, lead, and mercury were 0.04-6.7, 0.13-0.76, and 0.03-0.40 μg/g dry weight, respectively. On the whole, the contents of organochlorine pesticides and heavy metals in the organs of the Pacific walrus were lower compared to those in marine mammals from other regions of the World Ocean. [ABSTRACT FROM AUTHOR]

In Kazakhstan, there is a problem of finding ways to clean local sites contaminated with pesticides. In particular, such sites are the deserted and destroyed storehouses where these pesticides were stored; existing storehouses do not fulfill sanitary standards. Phytoremediation is one potential method for reducing risk from these pesticides. Genetic heterogeneity of populations of wild and weedy species growing on pesticide-contaminated soil provides a source of plant species tolerant to these conditions. These plant species may be useful for phytoremediation applications. In 2008-2009 and 2011, we surveyed substances stored in 80 former pesticide storehouses in Kazakhstan (Almaty oblast) to demonstrate an inventory process needed to understand the obsolete pesticide problem throughout the country, and observed a total of 354.7 t of obsolete pesticides. At the sites, we have found organochlorine pesticides residues in soil including metabolites of dichlorodiphenyltrichloroethane and isomers of hexachlorocyclohexane. Twenty-four of the storehouse sites showed pesticides concentrations in soil higher than maximum allowable concentration which is equal to 100 μg kg in Kazakhstan. Seventeen pesticide-tolerant wild plant species were selected from colonizing plants that grew into/near the former storehouse's pesticides. The results have shown that colonizing plant annual and biannual species growing on soils polluted by pesticides possess ability to accumulate organochlorine pesticide residues and reduce pesticide concentrations in soil. Organochlorine pesticides taken up by the plants are distributed unevenly in different plant tissues. The main organ of organochlorine pesticide accumulation is the root system. The accumulation rate of organochlorine pesticides was found to be a specific characteristic of plant species and dependent on the degree of soil contamination. This information can be used for technology development of phytoremediation of pesticide-contaminated soils. [ABSTRACT FROM AUTHOR]

A large-scale groundwater contamination characterises the Pleistocene groundwater system of the former industrial and abandoned mining region Bitterfeld/Wolfen, Eastern Germany. For more than a century, local chemical production and extensive lignite mining caused a complex contaminant release from local production areas and related dump sites. Today, organic pollutants (mainly organochlorines) are present in all compartments of the environment at high concentration levels. An integrated methodology for characterising the current situation of pollution as well as the future fate development of hazardous substances is highly required to decide on further management and remediation strategies. Data analyses have been performed on regional groundwater monitoring data from about 10 years, containing approximately 3,500 samples, and up to 180 individual organic parameters from almost 250 observation wells. Run-off measurements as well as water samples were taken biweekly from local creeks during a period of 18 months. A kriging interpolation procedure was applied on groundwater analytics to generate continuous distribution patterns of the nodal contaminant samples. High-resolution geological 3-D modelling serves as a database for a regional 3-D groundwater flow model. Simulation results support the future fate assessment of contaminants. A first conceptual model of the contamination has been developed to characterise the contamination in regional surface waters and groundwater. A reliable explanation of the variant hexachlorocyclohexane (HCH) occurrence within the two local aquifer systems has been derived from the regionalised distribution patterns. Simulation results from groundwater flow modelling provide a better understanding of the future pollutant migration paths and support the overall site characterisation. The presented case study indicates that an integrated assessment of large-scale groundwater contaminations often needs more data than only from local groundwater monitoring. The developed methodology is appropriate to assess POP-contaminated mega-sites including, e.g. HCH deposits. Although HCH isomers are relevant groundwater pollutants at this site, further organochlorine pollutants are present at considerably higher levels. The study demonstrates that an effective evaluation of the current situation of contamination as well as of the related future fate development requires detailed information of the entire observed system. [ABSTRACT FROM AUTHOR]

Enzyme 'hexachlorocyclohexane (HCH) dehydrochlorinase LinA' mediates first step of aerobic microbial degradation of a chlorinated insecticide γ-HCH. The archetypal LinA-type1 consists of 156 amino acids that include a directly repeated hexapeptide motif GIHFAP at positions 141-146 and 148-153. Analysis of a series of LinA mutants, containing none, one, two, or three units of this repeated motif revealed that two units, as present in wild-type LinA, are required for its optimal activity and stability. Moreover, the presence of a bend in its secondary structure due to a proline residue that precedes the distal repeated unit contributes to enhanced LinA activity. [ABSTRACT FROM AUTHOR]

Background and aims: Microbe-assisted phytoremediation is particularly effective for organic pollutants. The leguminous shrub Cytisus striatus (Hill) Rothm. has been proposed as a candidate species for the rhizoremediation of hexachlorocyclohexane (HCH)-contaminated sites. The aim of this study was to improve the performance of this species using microbial inoculants. Methods: C. striatus was grown in substrates contaminated with 0, 10 and 35 mg HCH kg for 8 weeks. Plants were either not inoculated (NI), or inoculated with the endophyte Rhodococcus erythropolis ET54b and the HCH-degrader Sphingomonas sp. D4 (isolated from a HCH-contaminated soil) on their own or in combination (ET, D4 and ETD4). Results: Inoculation with both bacterial strains (ETD4) resulted in decreased HCH phytotoxicity and improved plant growth. HCH-exposed plants inoculated with ETD4 presented a 120-160 % increase in root, and 140-160 % increase in shoot biomass, and led to a decrease in the activities of enzymes involved in anti-oxidative defence. APOD activity was reduced by up to 37 % in shoot tissues and 25 % in root tissues, and corresponding activities of SOD were reduced by up to 35 % and 30 %. HCH dissipation was enhanced in the presence of C. striatus but no significant effect of microbial inoculants was observed. Conclusions: Inoculating C. striatus with this combination of bacterial strains is a promising approach for the remediation of HCH-contaminated sites. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate hexachlorocyclohexane (HCH) exposure in children living in nine hot spots in four Mexican states. We analyzed HCH (α, β, and γ-isomers) in blood using gas chromatography/mass spectrometry. HCH exposure level in 261 children was assessed and approximately 75 % of the children studied had detectable levels of HCH. These levels ranged from 188 to 40,096.7 ng/g lipid. The highest mean levels were found in Lacanja (5,446.9 ng/g lipid), an indigenous community in Chiapas, Mexico. Our data indicate high exposure to HCH in children living in these communities. [ABSTRACT FROM AUTHOR]

The levels of 17 organochlorine pesticides residues (OCPs) in surface water and sediments from Tamiraparani river basin, South India were investigated to evaluate their potential pollution and risk impacts. A total of 96 surface water and sediment samples at 12 sampling stations were collected along the river in four seasons during 2008-2009. The ΣOCP concentrations in surface water and sediments were in the range of 0.1 to 79.9 ng l and 0.12 to 3,938.7 ng g dry weight (dw), respectively. Among the OCPs, the levels of dichlorodiphenyltrichloroethanes (DDTs), aldrin, dieldrin, cis-chlordane, trans-chlordane, and mirex were dominant in the sediments. The dominant OCPs in water samples are heptachlor, o,p′-DDE, dieldrin, o,p′-DDD, and mirex, which show different source of contamination pattern among sampling seasons. The distribution pattern of DDTs, hexachlorocyclohexane, and other OCPs in the present study shows heterogenic nature of nonpoint source of pollution. Notable contamination of water and sediment sample that was observed in upstream (S2) 58 ng l and downstream (S11) 1,693 ng g dw explains agricultural and municipal outfalls, whereas frequent damming effect reduces the concentration level in the midstream. The overall spatial-temporal distribution pattern of ΣOCP residues are illustrated by GIS package. [ABSTRACT FROM AUTHOR]

Hexachlorocyclohexane dehydrochlorinase (LinA) mediates first step of aerobic degradation of a chlorinated insecticide γ-hexachlorocyclohexane (γ-HCH). In this study, we describe characterization of a novel variant (LinA-type2) that is distinct from reported LinAs and is substantially more thermostable than archetypal LinA-UT26. LinA-type2 remains active even after 8 h of incubation at 45 °C, when nearly 50% activity of LinA-UT26 is lost after incubation for 60 min at the same temperature. Circular dichroism analysis revealed that secondary structures of LinA-UT26 and LinA-type2 are similar, but their Tm was 45 and 65 °C, respectively. Thermostability of LinA-type2 makes it suitable for bioreactors where allowance for higher temperatures can be of advantage. [ABSTRACT FROM AUTHOR]

Lindane (γ-hexachlorocyclohexane, γ-HCH) is a recalcitrant and toxic organochlorine insecticide. Due to its non-selective production process and widespread use, HCH isomers and their degradation products have been detected frequently in soils and groundwater. An innovative technology using microbial produced Pd(0) nanoparticles, i.e. bio-Pd, was developed to treat groundwater containing a mixture of HCHs and chlorobenzenes. In a first step, the groundwater was de-ironized and most of the chlorobenzenes were removed in a biological trickling filter. The μg L levels of HCHs and chlorobenzenes were removed in a second step by the bio-Pd-based technology. Therefore, a 200-L pilot scale reactor was developed with 100 mg L bio-Pd encapsulated in alginate beads. Hydrogen gas was bubbled at the bottom of the reactor and served to charge the bio-Pd catalyst. The reactor influent contained 5.2 μg L HCHs and 51.1 μg L chlorobenzenes. During a test period of 10 days, 29% of the HCH isomers and 63% of the chlorobenzenes were removed applying a nominal hydraulic residence time of 4 h. These removal percentages could be increased to 75 and 68% by doubling the nominal hydraulic residence time to 8 h. This study demonstrated that biologically produced nanoparticles of Pd can be applied for the large-scale remediation of groundwater contaminated with HCHs. [ABSTRACT FROM AUTHOR]

It has been suggested that prenatal exposure to some organochlorine compounds (OCs) may adversely affect thyroid function and may, therefore, impair neurodevelopment. The main aim of this study was to examine the relationship of cord serum levels of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (4,4′-DDT), 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (4,4′-DDE), β-hexachlorocyclohexane (β-HCH), hexachlorobenzene (HCB), four individual polychlorobiphenyl (PCB) congeners (118, 138, 153, and 180), and their sum, with neonatal thyroid stimulating hormone (TSH) levels in blood samples in a mother-infant cohort in Valencia, Spain. This study included 453 infants born between 2004 and 2006. We measured OC concentrations in umbilical cord serum and TSH in blood of newborns shortly after birth. Associations between neonatal TSH levels and prenatal OC exposure adjusted for covariates were assessed using multivariate linear regression analyses. Neonatal TSH levels tended to be higher in newborns with β-HCH levels in umbilical cord above 90th percentile (104 ng/g lipid) than in those with levels below the median (34 ng/g lipid), with an adjusted increment in neonatal TSH levels of 21% (95% confidence interval=−3, 51; P=0.09). No statistically significant association was found between the remaining OCs and TSH at birth. Prenatal exposure to β-HCH may affect neonatal thyroid hormone status and its function in neurological development. [ABSTRACT FROM AUTHOR]

The technical formulation of hexachlorocyclohexane (HCH) mainly consists of the insecticidal γ-isomer and noninsecticidal α-, β-, and δ-isomers, among which β-HCH is the most recalcitrant and has caused serious environmental problems. A γ-HCH-utilizing bacterial strain, Sphingobium sp. MI1205, was isolated from soil which had been contaminated with HCH isomers. This strain degraded β-HCH more rapidly than the well-characterized γ-HCH-utilizing strain Sphingobium japonicum UT26. In MI1205, β-HCH was converted to 2,3,5,6-tetrachlorocyclohexane-1,4-diol (TCDL) via 2,3,4,5,6-pentachlorocyclohexanol (PCHL). A haloalkane dehalogenase LinB (LinBMI) that is 98% identical (seven amino-acid differences among 296 amino acids) to LinB from UT26 (LinBUT) was identified as an enzyme responsible for the two-step conversion of β-HCH to TCDL. This property of LinBMI contrasted with that of LinBUT, which catalyzed only the first step conversion of β-HCH to PCHL. Site-directed mutagenesis and computer modeling suggested that two of the seven different amino acid residues (V134 and H247) forming a catalytic pocket of LinB are important for the binding of PCHL in an orientation suitable for the reaction in LinBMI. However, mutagenesis also indicated the involvement of other residues for the activity unique to LinBMI. Sequence analysis revealed that MI1205 possesses the IS 6100-flanked cluster that contains two copies of the linB MI gene. This cluster is identical to the one located on the exogenously isolated plasmid pLB1, suggesting that MI1205 had recruited the linB genes by a horizontal transfer event. [ABSTRACT FROM AUTHOR]

The chlorinated insecticide γ-hexachlorocyclohexane (γ-HCH) is sequentially metabolized by the products of linA, linB, linC, linD, linE, and linF genes to β-ketoadipate, which is subsequently mineralized. Two or more copies of these genes are present in the bacterium Pseudomonas aeruginosa ITRC-5 that was isolated earlier by selective enrichment on technical-HCH. At least one copy of linA, linB, linC, linD, and possibly linE is lost from ITRC-5 upon its growth on γ-HCH. All the lin genes, however, are lost when the bacterium was grown in Luria–Bertani (LB) medium. The loss of lin genes is accompanied with the loss/rearrangement of insertion sequence IS 6100 genes. Concomitant to the loss of lin genes, the degradation of HCH-isomers by “γ-HCH grown cells” is slower, when compared with “technical-HCH grown cells”, and is completely lost by “LB-grown cells”. The selective loss of lin genes during different growth conditions has not been reported before and is expected to help in understanding the dynamism of degradative genes. [ABSTRACT FROM AUTHOR]

Landfarming is a bioremediation technology in which contaminated soil is mixed with nutrients and amendments, and the material is periodically tilled for aeration. Contaminants are degraded, transformed and immobilised by means of biotic and abiotic reactions. In this study, a soil heavily contaminated (>5000 mg kg−1) with hexachlorocyclohexane (HCH) isomers derived from lindane production was treated using this technique. The combination of the physical disruption of HCH aggregates together with the biological degradation which is favoured by the improvement in the soil’s physical and chemical conditions, both contributed to a significant decrease of the α- and γ-HCH isomers (up to 89 and 82% of the initial concentration, respectively) at the end of the 11 month long experiment. In contrast, the most persistent β-isomer remained essentially unaffected. Flooded conditions did not improve HCH degradation. Degradation of α- and γ-HCH was quite rapid initially. Pentachlorocyclohexene (PCCH) and tetrachlorocyclohexene (TCCH) were identified as the main metabolites during the treatment period. The main variables that affected the process were: moisture content, temperature and especially the distribution and size of HCH aggregates, which limits HCH bioavailability. Aerobic landfarming appears to be an interesting and cost effective bioremediation treatment for soils contaminated with α- and γ-HCH isomers. However, complete sanitation of soil (total HCH < 2 mg kg−1), especially in the case of β-HCH, would require the application of other techniques, for example slurry system under anaerobic conditions. [ABSTRACT FROM AUTHOR]

The effect of prefeeding dehydrated amaranth leaves (AL), at 10 and 20% levels on hexachlorocyclohexane (HCH)-induced free radical stress in rat liver was evaluated. The HCH-induced raise in malonadialdehyde (MDA), conjugated dienes and hydroperoxides was diminished by AL. The effect of AL was highly effective with respect to reduction in these cytotoxic products, especially at 20% level. AL intake resulted in a significant increase in hepatic vitamin A and glutathione (GSH). However, the AL consumption reduced hepatic tocopherols. Feeding of AL at 10% level increased the hepatic glucose-6-phosphate dehydrogenase (G-6-PDH) activity while that at 20% level increased the hepatic glutathione reductase (GSSGR) as well, in addition to G-6-PDH. Amaranth leaves at 10 and 20% levels of feeding reduced the hepatic superoxide dismutase and glutathione peroxidase (GSH-Px) activities. The pre-feeding of AL resulted in the reversal of HCH-induced alteration in GSH-Px and G-6-PDH activities. The significant reduction in the level of glutathione S-transferase brought about by HCH was restored to control level by feeding 20% AL. It is concluded that the consumption of AL at 20% level produces reduction in the HCH-induced impairment of antioxidant status in rat liver. [ABSTRACT FROM AUTHOR]

Hexachlorocyclohexane (HCH) and lindane were used as insecticides since 1949s. They were progressively banished in most of the nations in the world, because of the their persistence and their potential toxicity and carcinogenicity. They are still occurring in the environment. These insecticides and isomers (α-HCH, β-HCH...) were detected in all media, e.g. soils, sediments, potable water, vegetables, human and animal tissues and air. In this review, we present the synthesis of the analytical procedures and materials used to determine the HCHs isomers in media such as vegetables, human tissues, animals tissues and rations. The analytical techniques which are presented permit to select the best analytical conditions to detect HCHs isomers. [ABSTRACT FROM AUTHOR]

Taking Beijing as a study area, a dynamic fugacity model was used to simulate the transfer and fate of technical HCHs according to the physic-chemical properties of the studying environment and HCH isomers. Dynamic changes of the transfer fluxes and concentrations of HCH isomers during 1952-2003 were simulated and the model results suggest good agreement between the calculated and measured concentrations of HCH isomers. During 1952-1983, the average input and output amount of HCHs through agricultural application and degradation are 130 t and 150 t respectively. The dominant transfer processes of HCHs in the study area are air-soil deposition, soil erosion and soil-air diffusion, transfer fluxes of these processes are 80 t⋅a−1, 16 t⋅a−1 and 11 t⋅a−1, which account for 92% of total transfer fluxes of HCHs isomers. There were approximately 253t HCHs in all environmental compartments of the study area during this period and 97% of which existed in soil compartment. Air and water advection became the dominant input sources of HCHs after 1984 when the application of technical HCHs was prohibited, concentration of HCHs quickly descended to a quite low level in several years. Total amount of HCHs isomers remaining in the study area environment now is less than 5% that before 1983, and this percentage may descend to 0.5% after 20 years by prediction. [ABSTRACT FROM AUTHOR]

The feasibility of the biodegradation of HCH and its intermediates has been investigated. A recent characterisation of two sites in The Netherlands has shown intrinsic biodegradation of HCH. At one site, breakdown products (monochlorobenzene, benzene and chlorophenol) were found in the core of the HCH-plume, whereas the HCH-concentration decreased over time and space. Characterisation of a second, industrial site indicated less intrinsic biodegradation and the need to stimulate biodegradation. In the laboratory, enhanced HCH degradation was tested with soil and groundwater material from both sites, and the required conversion to the intermediates benzene and monochlorobenzene was demonstrated. Furthermore, the biodegradation of these intermediates could be initiated by adding low amounts of oxygen (<5%). Adding nitrate enhanced this degradation. We hypothesise that this occurs through anaerobic nitrate reducing conversion of oxidised intermediates. At the non-industrial other site, intrinsic degradation took place, as shown in the laboratory experiments. Interpretation of the field data with computer codes Modflow and RT3D was performed. As a result of the modelling study, it has been proposed to monitor natural attenuation for several years before designing the final approach. At the industrial site, the results of the batch experiments are applied. Anaerobic HCH degradation to monochlorobenzene and benzene is stimulated via the addition of an electron donor. Infiltration facilities have been installed at the site to create an anaerobic infiltration zone in which HCH will be degraded, and these facilities are combined with the redevelopment of the site. [ABSTRACT FROM AUTHOR]

Many environmental contaminants known today are semivolatile organic compounds (SOC) and are present in the atmosphere. Airborne SOC are taken up and enriched by the epicuticular wax that covers leaves of higher plants. The purpose of the present work was to use pine needles 1) to map the distribution of airborne SOC in Europe, 2) to identify source regions, and 3) to identify hitherto unknown anthropogenic and/or natural substances. Some of the results were a confirmation of a suspected release of DDT in the former East Germany, high levels of pentachlorophenol were noted in Scandinavia, hexachlorocyclohexanes were higher in southern than in northern Europe, whereas PCB and hexachlorbenzene were rather evenly distributed throughout Europe. Elemental sulphur was identified as a previously unknown natural substance in higher plants. [ABSTRACT FROM AUTHOR]

Using hexachlorocyclohexane (BHC) as a model histopathological, histoenzymological, biochemical, and electrophoretic studies were undertaken to find out certain parameters for early diagnosis of liver cancer. In addition, cytogenetic studies were carried out to evaluate the effect of BHC feeding on mitotic and meiotic divisions. The results of these investigations suggest that there is a significant change in liver weight in experimental group. Histologically, liver cells follow a definite sequential cellular alteration ultimately leading to liver tumor. Histochemically, well defined pattern of glycogen accumulation and iron distribution in hepatocytes was observe. The electron-microscopic observation demonstrated prominently the proliferation of agranular endoplasmic reticulum in early stages. The distribution of certain enzymes linked with plasma membrane, lysosomes, and mitochondria showed the functional alteration of these organelles both in neoplastic nodules and tumours induced by BHC. The biochemical changes observed in gluconeogenic enzymes (G6Pase and F1,6dipase) and dehydrogenases (LDH, ICDH, and MDH) at different duration of exposure to BHC indicated decrease in enzyme activity of both gluconeogenic pathway and tricarboxylic acid cycle, linked with energy metabolism. These changes tend to recover with discontinuation of BHC but 8 months continuous feeding produces irreversible changes in G6Pase activity. Using polyacrylamide gel electrophoresis technique a change in serum proteins and LDH isoenzymes was observed. However, extrapolation of these findings to human situation needs more extensive studies, taking into account all possible variables, such as the DDT and BHC load in our environment and the body burden resulting there from. [ABSTRACT FROM AUTHOR]

The accumulation of hexachlorocyclohexane, one of the most commonly used chlorinated insecticides, was studied in a high-risk group of people who are exposed during its manufacturing process. The serum HCH concentration was estimated by quantitating its α, β, γ and δ-isomers with the help of GLC analysis. Exposed workers involved in maintenance work were found to have 3 times higher HCH residues than the controls, while in the plant operators and supervisors the levels were 5 times higher. The most severely exposed were the handlers who are in direct contact with the insecticide. The level of serum HCH residues in them was found to be about 12 times higher than those in the controls. The percentage composition of the insecticide, with respect to the different isomers, varied up to 20% for the γ-isomer, up to 30% for α-isomer and had between 60%-100% of the β-isomer in the samples. The serum levels of the insecticides were clearly related to the workers' job-related close contact, intensity, frequency, and the duration of their exposure. The total of HCH residues in the sera studied were in the range of 0.143-1.152 ppm. The importance of these findings and the relevant protective measures are discussed. [ABSTRACT FROM AUTHOR]

A sensitive and specific gas chromatographic method is described for the simultaneous determination of ten chlorinated phenols that appear in the urine of persons exposed to hexachlorocyclohexane (HCH). The phenolic compounds in the urinary samples are hydrolysed in an acidic medium and derivatised with acetic anhydride. This sample treatment permits routine application. The stationary phase (8% DC 200 on Chromosorb G AW-DMCS possesses a high separating capability for the acetic esters of the chlorophenols. The detection limits lie between 4.9 and 18.6 μg/l and allow determinations even in the environmentally interesting concentration range. The recoveries determined using aqueous standards range between 87 and 119% and the relative standard deviations are between 4.4 and 10.1%. [ABSTRACT FROM AUTHOR]

In a lindane (γ-hexachlorocyclohexane)-producing factory 54 male workers (mean age 40 years, mean duration of exposure 8 years) were studied with regard to their blood levels of testosterone, LH, and FSH. Twenty clerks of nearly the same age were examined for control purposes in the same way. Serum-LH concentrations of the exposed workers were significantly higher than in controls. Geometric mean values were 8.8 mIU/ml and 5.7 mIU/ml respectively. On the other hand, FSH levels were insignificantly higher. Concerning testosterone concentrations in serum, these were found to be slightly lower in the group of workers than in control persons but this difference could not be proved to be statistically significant. These results indicate certain perturbations in sex hormone regulation probably as a consequence of HCH-exposure. To judge the pathological significance of these alterations further investigation will be necessary. [ABSTRACT FROM AUTHOR]

Sixty male workers in a lindane (γ-hexachlorocyclohexane) producing factory were examined with regard to functions of nervous system in comparison with two external control groups having no contact with hazardous substances. Examinations of reflexes and sensibility revealed no pathological signs. Mean values of amplitude and frequency of forefinger tremor were found at about 20 μm and 10 Hz respectively without significant differences between groups. Manual skill tested by means of a tracking task was nearly the same in HCH-workers and a control group of dairy workers. On the contrary, a control group of clerks showed significantly better results in the tracking test, a probable consequence of their occupational practice. In electromyography no pathologic patterns were observed. The maximal motor nerve conduction velocity of ulnar nerves showed nearly identical mean values of 59.5 m/s in HCH-workers and controls. Neuromuscular conduction as revealed by distal latencies was not impaired. Furthermore, electroencephalographic recordings taken in spot-checks of HCH-workers and controls did not show any specific pathological signs. Only small abnormalities in rhythm could be observed in some cases of workers as well as of control persons indicating no increased incidence in the HCH exposed group. In conclusion, even after years or decades of occupational HCH exposure, in this study no signs of neurological impairment or perturbation of 'neuromuscular function' could be ascertained. [ABSTRACT FROM AUTHOR]

Sixty male workers in a lindane (y-hexachlorocyclohexane)-producing factory were examined with regard to health in comparison with an external control group of 20 clerks. Case history, physical examination, neurologic status, and ECG revealed no significant differences between groups. However, the following significant differences in clinical-chemical blood tests were ascertained: higher polymorphonuclear leukocyte count, lower lymphocyte count, higher reticulocyte count, lower prothrombin (Quick's) test, and lower blood concentrations of creatinine and uric acid. No significant differences were observed in total red and white blood cell as well as platelet counts, hemoglobin content, the other counts of differential blood picture, γ-GT, GOT, GPT, LDH, cholinesterase, triglycerides, cholesterol, and urea. In spite of a pronounced exposure to the α-, β-, and γ-isomers of hexachlorocyclohexane, no signs of severe impairment of health were observed; only small deviations in some laboratory tests were found having no pathologic significance. However, biological monitoring and health supervision of HCH-exposed workers should be carried out. [ABSTRACT FROM AUTHOR]

In a lindane ( γ-hexachlorocyclohexane = γ-benzenehexachloride)-producing factory 57 workers were studied with regard to their blood levels of the three hexachlorocyclohexane isomers: α-, β-, and γ-HCH. The TLV-TWA (MAK value 1979) for γ-HCH of 0.5 mg/m was not exceeded at any of the workplaces where HCH is synthesized and purified to lindane. Additionally, in some of the workers samples of s.c. adipose tissue were taken for determination of HCH-isomer content. An external group of 20 clerks was examined in the same way for control purposes. In contrast to the control persons, none of whom had HCH-concentrations in serum above the respective detection limits, the values determined in serum of the exposed workers were in the following ranges: α-HCH: 10-273 μg/l, β-HCH: 17-760 μg/l, and γ-HCH: 5-188 μg/l. Of special interest is the observation of a significant increase of β-HCH-concentration in serum with the time of employment in lindane production, indicating a pronounced accumulation of this substance in the human organism. Concentrations of this isomer in s.c. adipose tissues were about 300-fold higher than in serum. A significant correlation between both parameters could be established. The results of this study show that adherence to the TLV-TWA of γ-HCH is not sufficient for control of HCH-exposure. Furthermore, biological monitoring of exposed workers is necessary taking into account the three more important isomers α-, β-, and γ-HCH. [ABSTRACT FROM AUTHOR]

Hexachlorocyclohexane (HCH) is reported to induce oxidative stress in liver and testis of rat. With an objective to examine its effect on brain tissue acute toxicity of HCH (10 and 20 mg/kg body wt, i.p.) on the antioxidant defense system of cerebral hemisphere of rat was evaluated. Lipid peroxidation (LPX) was elevated after 24 h in the crude homogenate and sub-cellular fractions (nuclear and mitochondrial) except the microsomal fraction in which LPX was induced after 6 h and remained elevated till 24 h. The pesticide elicited decrease in the activities of cytosolic total, CN−-sensitive (not at 24 h) and CN-resistant superoxide dismutases; total, Se-dependent and Se-independent glutathione peroxidases; and catalase throughout the measurement period. In contrast, glutathione reductase activity was elevated till 24 h after a fall at 6 h of pesticide exposure. Cerebral contents of glutathione and ascorbic acid were decreased in response to HCH. The results suggest the possible involvement of reactive oxygen species in the mechanism of HCH-induced neurotoxicity in rat. [ABSTRACT FROM AUTHOR]

A commercial wettable-powder formulation (50% a. i.) of hexachlorocyclohexane (HCH) was applied to unplanted and planted (to rice) soils under flooded and non-flooded conditions at 1 kg a. i. ha at 15-day intervals. A mineral salts medium supplemented with γ-HCH as a sole source of C was inoculated with suspensions from HCH-treated and untreated soils (unplanted or planted to rice) and incubated under aerobic conditions. γ-HCH disappeared completely within 10 days from the aerobically incubated medium inoculated with the suspension from the treated soil compared to less than 30% loss from the uninoculated medium or from the medium inoculated with the suspension from the untreated soil, during the corresponding period. Soil samples from HCH-treated flooded pots lost their capacity for accelerated degradation of γ-HCH after autoclaving. The addition of HCH clearly stimulated aerobic degradation of γ-HCH, even in predominantly anaerobic flooded soil. The factor responsible for the accelerated degradation of γ-HCH in pretreated soil was not detected in the deeper layers (>10 cm) of flooded soil and in fields that had dried following the rice harvest. [ABSTRACT FROM AUTHOR]

Urine and organe of rats were examined for metabolites after oral dosage of the beta-isomer of hexachlorocyclohexane (HCH). Beta-HCH was converted to 2,3,4- and 2,4,6-trichlorophenol (TCP), to other isomers of TCP, and to 2,3,4,6-tetrachlorophenol. [ABSTRACT FROM AUTHOR]

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Sphingomonas paucimobilis degrades aerobically α, β, γ and δ-hexachlorocyclohexane. With α-HCH, complete degradation occurred after 3 days but with β and γ, and with δ-HCH, 98 and 56 % degradation occurred after 12 and 8 days of incubation, respectively. Pentachlorocyclohexene was formed as the primary metabolite during the degradation of all the HCH isomers. © Rapid Science Ltd. 1998 [ABSTRACT FROM AUTHOR]