Technical Grade Hexachlorocyclohexane Research Articles

Photochemical degradation of β-hexachlorocyclohexane in snow and ice.

Hexachlorocyclohexane (HCH), a typical organochloride pesticide, is one of the persistent organic pollutants. Despite the ban on technical grade HCH, it has been continuously observed at a steady level in the environment. The photochemical degradation of β-HCH in snow and ice under ultraviolet (UV) irradiation was investigated in this study. The effects of pH as well as common chemical components in snow on the degradation kinetics were investigated. In addition, the photodegradation products were determined and the reaction mechanism was hypothesized. The results showed that under UV irradiation, β-HCH can be photolyzed in snow and ice, with the photochemical degradation process conforming to the first-order kinetic equation. Changing the pH and adding Fe2+ had minimal effect on the photochemical degradation kinetics, while the presence of acetone, NO2-, NO3- and Fe3+ significantly inhibited the process. The addition of hydrogen peroxide slightly inhibited the photochemical degradation of β-HCH. Finally, the reaction rate, products and degradation mechanism of β-HCH in snow were compared with those in the ice phase. The photochemical degradation rate of β-HCH in snow was approximately 24 times faster than that in the ice phase. The photolysis product of β-HCH in snow was α-HCH, produced by the isomerization of β-HCH. However, in ice, in addition to α-HCH, pentachlorocyclohexene was produced by dechlorination. The results of this study are helpful in understanding the transformation of organochlorine pesticides in snow and ice, as well as in providing a theoretical basis for snow and ice pollution prevention and control.

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

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

Microbial indicators for assessing the adverse impact of technical-grade hexachlorocyclohexane on soil quality

Technical-grade hexachlorocyclohexane (HCH) has been widely used for human health and agricultural purposes. Consequently, HCH residues have entered the soil ecosystem with concomitant deleterious effects on soil quality. The aim of this study was to assess the impact of HCH on soil microbial properties as biological indicators of soil quality. To this end, non-polluted soil was spiked with different amounts of a heavily HCH-polluted soil in order to obtain a concentration gradient between 0 and 1,500 mg HCH kg&lt;sup&gt;-1&lt;/sup&gt; dry matter soil. The mixtures were incubated under laboratory conditions for 2 months. Dehydrogenase activity, fluorescein diacetate hydrolysis activity (FDA), basal respiration, substrate-induced respiration (SIR), microbial biomass carbon, metabolic potential, and the soil quality index were negatively affected by increasing HCH concentrations in soil, in many cases following an exponential pattern. FDA and SIR appear &lt;em&gt;a priori&lt;/em&gt; suitable indicators for the impact of HCH on soil microbial properties and, hence, soil quality.

Thermal desorption of HCH

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−1 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.

Substantially Enhanced Degradation of Hexachlorocyclohexane Isomers by a Microbial Consortium on Acclimation

Widespread contamination of the environment, globally, has been caused by extensive and indiscriminate use of hexachlorocyclohexane (HCH) as an insecticide since the 1940s, threatening the biota including humans, and there is an urgent need to eliminate it, preferably through bioremediation technologies. A gamma-HCH-degrading microbial consortium was isolated by enrichment of a soil sample from a sugar cane field having a long history of technical grade HCH application. On acclimation the degrading ability improved substantially. The consortium, which took 10 days to degrade 25 microg mL(-1) of gamma-HCH, initially could mineralize even 300 microg mL(-1) of the substrate within 108 h on acclimation. With 300 microg mL(-1) substrate, the rate of degradation, as calculated for the early exponential phase, was 216 microg mL(-1) day(-1), the highest reported so far. An amount of 400 microg mL(-1) of gamma-HCH, however, was mineralized partially with only 78% Cl(-) release. No apparent accumulation of intermediary metabolites was observed up to 300 microg mL(-1) substrate, indicating a fast rate of mineralization. Aeration, mesophilic temperatures (20-35 degrees C), and near neutral pH (6.0-8.0) were favorable conditions for degradation. The presence of glucose at 1000 microg mL(-1) retarded the degradation, whereas cellulose and sawdust at 1600 microg mL(-1) and glucose at 100 microg mL(-1) did not show any marked effect. The consortium also mineralized alpha-, beta-, and delta-HCH efficiently. The consortium consisted of nine bacterial strains and a fungal strain, and individually they were able to degrade 10 microg mL(-1) of gamma-HCH. This mixed culture holds high potential for deployment in bioremediation of HCH-contaminated soils, waste dumpsites, and water bodies.

Fate and Degradation of POP-Hexachlorocyclohexane

Hexachlorocyclohexane (HCH) and its isomers are one of the most frequently detected chlorinated contaminants in the environment. In spite of the ban on technical grade HCH and restricted use of γ-HCH (lindane), its residues have not stopped from entering the environment. Its extensive use in the past, present use of lindane in several countries, unused stockpiles of date-expired HCH from earlier manufacturing, as well as leachates from earlier disposal at dump sites continue to pollute the biosphere. Because HCH is a persistent organic pollution (POP) known to have several toxic and deleterious effects on human health and wildlife, it becomes imperative to remove this substance of serious concern to the global community. A better understanding on the fate and degradation of this POP in the environment will facilitate in drawing measures to mitigate this chemical and bring about bioremediation of already contaminated sites. This review focuses on the fate, contamination levels, abiotic and biotic degradation of HCH isomers, genes and enzymes involved in microbial degradation, and future research needs in this area.

Aqueous phase partitioning of hexachlorocyclohexane (HCH) isomers by biosurfactant produced by Pseudomonas aeruginosa WH-2

The different isomers of technical-grade hexachlorocyclohexane (t-HCH) including the insecticidal γ-isomer, commonly known as lindane, have been reported to be toxic, carcinogenic and endocrine disrupters. The spatial arrangements of the chlorine atoms on different isomers and low aqueous phase solubility contribute to their persistence in environment, β-HCH being the most resistance to transformation. The biosurfactant preparation of Pseudomonas aeruginosa isolate WH-2 was evaluated for its ability to improve the aqueous phase partitioning of different isomers of HCH-muck. Further, the ability of biosurfactant preparation to emulsify HCH and n-hexadecane was checked under different conditions, usually characteristic of sites contaminated with pollutants viz. wide range of pH, temperature, and salinity. The data obtained from this study will be helpful in designing suitable bioremediation strategies for huge stock piles of HCH-muck and sites polluted by reckless use/disposal of HCH-isomers.

Enhanced biodegradation of hexachlorocyclohexane in upflow anaerobic sludge blanket reactor using methanol as an electron donor

Anaerobic dechlorination of technical grade hexachlorocyclohexane (THCH) was studied in a continuous upflow anaerobic sludge blanket (UASB) reactor with methanol as a supplementary substrate and electron donor. A reactor without methanol served as the experimental control. The inlet feed concentration of THCH in both the experimental and the control UASB reactor was 100 mg l −1. After 60 days of continuous operation, the removal of THCH was >99% in the methanol-supplemented reactor as compared to 20–35% in the control reactor. THCH was completely dechlorinated in the methanol fed reactor at 48 h HRT after 2 months of continuous operation. This period was also accompanied by increase in biomass in the reactor, which was not observed in the experimental control. Batch studies using other supplementary substrates as well as electron donors namely acetate, butyrate, formate and ethanol showed lower % dechlorination (<85%) and dechlorination rates (<3 mg g −1 d −1) as compared to methanol (98%, 5 mg g −1 d −1). The optimum concentration of methanol required, for stable dechlorination of THCH (100 mg l −1) in the UASB reactor, was found to be 500 mg l −1. Results indicate that addition of methanol as electron donor enhances dechlorination of THCH at high inlet concentration, and is also required for stable UASB reactor performance.

Vertical distributions of persistent organic pollutants (POPs) caused from organochlorine pesticides in a sediment core taken from Ariake bay, Japan

Persistent organic pollutants (POPs) of organochlorine pesticides such as dichlorodiphenyl trichloroethane (DDTs) and its metabolites, hexachlorobenzene (HCB), heptachlor, chlordane compounds (CHLs), aldrin, dieldrin, endrin, mirex and isomers of hexachlorocyclohexane (HCHs), were analyzed in sediment cores collected from Ariake Bay, Japan. Although Chikugo River has the largest flow in Ariake Bay, the total concentration of POPs in surface sediment was found in St.3, mouth of the Yabe River, where that level was two times higher than St.1, mouth of the Chikugo River. It could be assumed that the potential source of POPs contamination is relatively close to this study area. Relatively high residue levels of HCB, HCHs and DDTs in sediment core were found during the period from 1967 to 1970. In this layer, the HCB concentration investigated in sediment cores of Ariake Bay was maximum, 2.6 ng g(-1) dry weight and higher than that of Tokyo Bay and subsequently detected in deeper sediment cores. The ratio of (DDD+DDE)/SigmaDDTs was high in top sediments (0-2 cm). Although there was a concentration of DDTs in the top sediment, it was noticed that DDT emission did not cause direct input of DDT recently. The HCHs determined in upper sediment cores might be originated from long-range accumulation in environment after dispersing of technical-grade HCH. Moreover, the CHLs, dieldrin and heptachlor concentrations were detected and recently increased in sediment core. POPs in sediment cores of Ariake Bay based on the possibility of PCP contamination during the early 1960s were reflected.

Assessment of bioremediation possibilities of technical grade hexachlorocyclohexane (tech-HCH) contaminated soils

Hexachlorocyclohexane (HCH) is a broad spectrum insecticide still used in some of the developing countries, though developed countries have banned or curtailed its use. Even in those countries where the use of t-HCH has been discontinued for a number of years, the problem of residues of all isomers of t-HCH remains because of its high persistence. These insecticides in the soil disturb the delicate equilibrium between microorganisms and their environment. Few reports on the degradation of t-HCH isomers in soil are present in literature, and very little information is available on the effect of these t-HCH isomers on soil microflora. In the present study, an attempt has been made to see the microbial diversity in the uncontaminated soils and the effect of application of t-HCH on the soil microflora. The soil was spiked with t-HCH and incubated, at regular time intervals the soil samples were analyzed for microbial diversity as well as t-HCH isomers residues. The results show that at higher concentrations of t-HCH, microbial populations were inhibited and the inhibited populations did not reappear even after prolonged incubation. Potential t-HCH degrading cultures were isolated and subjected to further acclimation in order to enhance their degradation capacity. The results are presented and discussed in this paper.

Biodegradation of tech-hexachlorocyclohexane in a upflow anaerobic sludge blanket (UASB) reactor

Biodegradability of technical grade hexachlorocyclohexane (tech-HCH) was studied in an upflow anaerobic sludge blanket reactor (UASB) under continuous mode of operation in concentration range of 100–200 mg/l and constant HRT of 48 h. At steady state operation more than 85% removal of tech-HCH (upto 175 mg/l concentration) and complete disappearance of β-HCH was observed. Kinetic constants in terms of maximum specific tech-HCH utilization rate ( k) and half saturation velocity constant ( K L) were found to be 11.88 mg/g/day and 8.11 mg/g/day, respectively. The tech-HCH degrading seed preparation, UASB reactor startup and degradation in continuous mode of operation of the reactor is presented in this paper.

Bioremediation of HCH-contaminated soil: elimination of inhibitory effects of the insecticide on radish and green gram seed germination

The effects of technical grade hexachlorocyclohexane (tech-HCH) on the germination of different seeds were tested. Two types of seeds, radish and green gram showed marked reduction in germination percentage and seeding vigour index. The abnormalities and reduction in germination increased with increasing concentration of tech-HCH. At 100 μg HCH level the germination of radish and green gram seeds was inhibited almost completely on moist filter paper and soil. Protease and amylase activities were reduced in seeds grown in soil spiked with tech-HCH. Bioremediation of HCH-spiked soils with a HCH-degrading microbial consortium helped in eliminating the toxic effects of tech-HCH towards seed germination. The degradation of 25 μg tech-HCH g −1 soil was complete by 120 h. The seed germination and the activities of the assayed enzymes, amylase and protease, were same as before or better in bioremediated soils.

Biodegradation of hexachlorocyclohexane isomers in soil and food environment.

Persistence of chlorinated hydrocarbon insecticides in the environment is well documented. One early introduced insecticide, hexachlorocyclohexane (HCH), popularly called BHC, was used in large quantities all over the world until recently. In India, even today, technical grade HCH is being used extensively. Theoretically, HCH has eight possible stereoisomers of which four (alpha, beta, gamma, and delta) predominate in the technical product. These isomers significantly differ between themselves with respect to their persistence and toxicity toward insects, birds, mammals, and other nontarget organisms. The relative proportion of HCH isomers is, therefore, crucial from a toxicology standpoint. This problem assumes importance in light of reports that the HCH isomers undergo interconversion in soil, water, animals, plants, insects, etc. The persistence of HCH can be attributed in part to the interconversion of HCH isomers, which also restrict their solubility. In the present review, biotransformation of HCH isomers, both under aerobic and anaerobic conditions, and their degradation pathways have been described. In addition, emphasis is given to the interconversion of HCH isomers, including interconversion mechanisms, as this area has not received adequate coverage in earlier reviews on HCH.

Deviations in ornithine-related metabolism during hexachlorocyclohexane-induced hepatocarcinogenesis in mice: Evidence for conversion of glutamate to ornithine

Chronic administration of technical-grade hexachlorocyclohexane in Swiss male mice resulted in necrosis, and later in adenomatous nodules and hepatocellular carcinomas at 3, 7, and 10 months, respectively, after initiation of the experiment. A definite pattern of changes were observed of arginase, ornithine transaminase, ornithine carbamoyltransferase activities, and metabolites related to ornithine. Conversion of glutamate to ornithine correlated well with the decreased glutamate and constant ornithine in liver of mice fed hexachlorocyclohexane for 7 months.

Dominant-lethal study of technical-grade hexachlorocyclohexane in Swiss mice

Male Swiss mice, 6–8 weeks old, were given a diet containing technical-grade hexachlorocyclohexane (BHC) at 500 ppm continuously for 4,6 and 8 months. After the completion of the scheduled exposure period, the males were sequentially mated with 2–3 untreated virgin females at weekly intervals for 8 weeks. The females were autopsied at mid-term pregnancy for evaluation of dominant-lethal mutation. The number of dead implants, including deciduomas and dead embryos, showed a significant increase. Similarly, the percentage fertility and live embryos per female showed a decline when compared with the control.

Sequential changes in lactate, isocitrate, and malate dehydrogenases in mice exposed to technical grade hexachlorocyclohexane (BHC) and their possible relationship to liver tumors

Hexachlorocyclohexane (BHC) was fed at a 500-ppm-dose level in diet to pure inbred Swiss mice for 2, 4, 6, and 8 months. Later BHC was discontinued for 4 months and subsequently the animals were refed BHC for 1 month. The protein, lactate dehydrogenase (E.C.1.1.1.27), isocitrate dehydrogenase (E.C.1.1.1.42), and malate dehydrogenase (E.C.1.1.1.37) were studied from liver. The liver weight as percentage of body weight was also determined. The results showed an increase in the liver weight/body weight ratio and a decrease in protein and all three enzymes after BHC feeding for the different time intervals. The discontinuation of BHC in the diet resulted in the reversion of values of the above parameters toward the normal and after refeeding BHC for 1 month, the decreased values, as seen after initial BHC feeding, were again observed. This indicates that the changes in the values of lactate dehydrogenase, isocitrate dehydrogenase, and malate dehydrogenase are associated with hexachlorocyclohexane feeding in the diet. The significance of these changes is discussed.

Early changes in serum protein and liver LDH isoenzymes in mice exposed to technical grade hexachlorocyclohexane (BHC) and their possible relationship to liver tumours

Mice were exposed to hexachlorocyclohexane (BHC) in order to study the changes in the serum protein pattern and in the LDH isoenzymes of the liver. After 2 months of exposure the protein pattern showed a new band which persisted even after the development of a tumour. The LDH isoenzymes pattern showed a gradual decrease of the faster moving LDH-1 and LDH-2 bands which later disappeared completely when hepatic tumours formed. The significance of these results is discussed.