Higher Hexachlorobenzene Research Articles

Mechanochemical remediation of the chlorinated compounds contaminated soil depending on the minerals inside-the most reasonable approach

This study explored a possible destruction of hexachlorobenzene (HCB) as example of persistent organic pollutants (POPs) as well as the dechlorination mechanism by directly using minerals in the soil, such as antigorite, talc and olivine. Compared with a stable quartz phase of SiO2, all three Mg silicate minerals demonstrated certain degrading capacity for HCB with different efficiency order as: antigorite > talc > olivine > SiO2 at 2 h of milling time. Interestingly, olivine exhibited a better performance than antigorite at 4 h of milling time, giving destruction percentage of 92.7% over 89.0% even at high concentrated HCB up to 5% added. Raman and ESR characterizations of the ball milled sample with olivine indicated the formation of amorphous carbon and graphitic carbon, and the occurrence of free radicals was observed to play an important role in dechlorination and carbonization of HCB. The first identified effectiveness of directly using Mg silicate minerals, allowed no addition of active chemicals during the ball milling, therefore avoided the concern over extrinsic contaminations on the soil. Olivine was further utilized to deal with actual contaminated soil and showed unique advantages on application prospects.

Fatty Acid Composition of Comamonas testosteroni under Hexachlorobenzene Loading Conditions

Changes in the lipid composition in bacterial membranes are considered to be the most important adaptation mechanisms to adverse chemical factors. The aim of the study was to compare the hexachlorobenzene effects on the fatty acid composition of total lipids Comamonas testosteroni. Methods. The study was performed with C. testosteroni UCM B-400 and B-401, B-213 strains. Bacteria were grown in the Luria-Bertrani (LB) liquid medium containing 10 and 20 mg/L of hexachlorobenzene (HCB). After cultivation, the biomass was separated by centrifugation and the fatty acid composition of total lipids was determined through analyzing its methyl esters. To assess the cell membrane properties, such parameters as the lipid unsaturation index, the average carbon chain length of fatty acids, and the membrane viscosity index were determined. Results. In the fatty acids spectrum of C. testosteroni B-400 after cultivation in a medium containing 20 mg/L of HCB, the contents of unsaturated hexadecenoic (C16:1) and octadecenoic (C18:1) acids were lower by 10.6 and 5.5%, respectively, and that of saturated hexadecanoic (C16:0) acid was higher by 8.4%, compared to the control. The fatty acid composition of C. testosteroni B-401 was more stable compared to strain B-400. Collection strain C. testosteroni B-213 compared to strains isolated from soil with high HCB load, in the presence of 10 and 20 mg/L of HCB had the highest relative content of saturated hexadecanoic acid (C16:0) up to 38.33—40.7%. Unsaturated octadecenoic acid decreased at the doses 10 and 20 mg/L to 1.5—2% compared to the control. In all strains under the HCB impact, there was an increase in the relative content of C17-cyclopropanoic acid compared to control variants. Conclusions. C. testosteroni UCM B-400, B-401, and B-213 bacteria under cultivation conditions in HCB-containing medium, decreasing the degree of lipid unsaturation and increasing the relative content of C17-cyclopropanoic acid can be considered as the main mechanisms regulating the cytoplasmic membrane fluidity; the displaying of these protective reactions had a strain trait and did not depend on the adaptation in natural isolating places.

Prenatal environmental exposures and associations with teen births.

Background:Children’s prenatal exposure to multiple environmental chemicals may contribute to subsequent deficits in impulse control, predisposing them to risk-taking.Objective:Our goal was to investigate associations between prenatal exposure mixtures and risk of teen birth, a manifestation of high-risk sexual activity, among 5,865 girls (1st generation) born in southeast Massachusetts from 1992-1998.Methods:Exposures included prenatal modeled polychlorinated biphenyls (PCBs), ρ,ρ′-dichlorodiphenyl dichloroethylene (DDE), hexachlorobenzene (HCB), lead (Pb), and mercury (Hg). We fit adjusted generalized additive models with multivariable smooths of exposure mixtures, 1st generation infant’s birth year, and maternal age at 1st generation birth. Predicted odds ratios (ORs) for teen birth were mapped as a function of joint exposures. We also conducted sensitivity analyses among 1st generation girls with measured exposure biomarkers (n=371).Results:The highest teen birth risk was associated with a mixture of high prenatal HCB, Hg, Pb, and PCB, but low DDE exposure, with similar associations in sensitivity analyses. The highest OR predicted for girls born in 1995 to mothers of median age (26 years) was at the 95th percentile of the HCB and PCB exposure distributions (OR=3.09; 95% confidence interval: 0.29, 32.4). Additionally, girls born earlier in the study period or to teen mothers were at increased risk of teen birth.Significance:Prenatal environmental chemical exposures and sociodemographic characteristics may interact to substantially increase risk of teen births.

Association between chlorinated pesticides in the serum of prepubertal Russian boys and longitudinal biomarkers of metabolic function.

Organochlorine pesticides (OCPs) have been linked to adult metabolic disorders; however, few studies have examined these associations in childhood. We prospectively evaluated the associations of baseline serum OCPs (hexachlorobenzene, β-hexachlorocyclohexane, and p,p'-dichlorodiphenyldichloroethylene) in Russian boys with subsequent repeated measurements of serum glucose, insulin, lipids, leptin, and calculated homeostatic model assessment of insulin resistance (IR). During 2003-2005, we enrolled 499 boys aged 8-9 years in a prospective cohort; 318 had baseline serum OCPs and serum biomarkers measured at ages 10-13 years. Multivariable generalized estimating equation and mediation regression models were used to examine associations and direct and indirect (via body mass index (BMI) (weight (kg)/height (m)(2))) effects of prepubertal OCP tertiles and quintiles with biomarkers. In multivariable models, higher p,p'-dichlorodiphenyldichloroethylene (quintile 5 vs. quintile 1) was associated with lower leptin, with relative mean decreases of 61.8% (95% confidence interval: 48.4%, 71.7%) in models unadjusted for BMI and 22.2% (95% confidence interval: 7.1%, 34.9%) in models adjusted for BMI; the direct effect of p,p'-dichlorodiphenyldichloroethylene on leptin accounted for 27% of the total effect. IR prevalence was 6.6% at ages 12-13 years. Higher hexachlorobenzene (tertile 3 vs. tertile 1) was associated with higher odds of IR in models adjusted for BMI (odds ratio = 4.37, 95% confidence interval: 1.44, 13.28). These results suggest that childhood OCPs may be associated with IR and lower leptin.

Dechlorination of hexachlorobenzene in treatment microcosm wetlands

There is little understanding of the pathways of hexachlorobenzene (HCB) removal in treatment wetlands. The aim of this research was to evaluate HCB dechlorination as affected by common reed (Phragmites australis) and broad-leaved cattail (Typha latifolia) applications in neutralized and enriched with nutrients peat with high, low and nil HCB concentration (300, 15, and 0μg/g, respectively). After 10 weeks of the experiment, HCB removal was 49.4–67.2% in High-HCB peat, and 57.6–74.8% in Low-HCB peat. The mean removal of HCB was 53.5% in the unvegetated and 68.7% in the vegetated microcosm wetlands. The amount of HCB metabolites showed that dechlorination rates in Low-HCB microcosms were higher than in High-HCB microcosms, which were mainly attributed to the lower phytotoxicity and higher dissolved organic carbon (DOC) content than that of Low-HCB. Although HCB uptake by plants was <0.1% of the initial concentration, in both High-HCB and Low-HCB peats vegetated with Typha and Phragmites, enhanced HCB dechlorination rate was found. This was probably because the roots and its exudates enhanced dechlorination process. Microbial degradation was the predominating process in HCB removal. The following dechlorinated metabolites of HCB were detectable from the water, macrophytes and peat samples: PeCB, 1,2,3,4-, 1,2,3,5- and 1,2,4,5-TeCB, 1,2,3-, 1,2,4- and 1,3,5-TCB.

A Worldwide Survey of Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, and Related Contaminants in Butter

The main source of human exposure to persistent organic pollutants (POPs) is, in general, food. In this study, 64 butter samples from 37 countries were analyzed to assess the global contamination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), hexachlorobenzene (HCB), and 2,2-bis (4-chlorophenyl)-1,1,1-trichloroethane (DDT) together with its major metabolites. The objectives of the study were to assess the presence of major organohalogen contaminants in butter, to trace geographical differences, and to determine toxic equivalents (TEQs) of PCDDs/Fs and dioxin-like PCBs in butter. The highest PCDD/F concentrations were found in butter from Korea with an average of 1.4 pg TEQ g(-1) lipid weight (l.w.). from PCDD/F and an additional contribution from the non- and mono-ortho-PCBs of 0.55 pg TEQ g(-1) l.w. Belgian butter showed average levels of 0.53 and 1.2 pg TEQ g(-1) l.w. for PCDDs/Fs and PCBs, respectively, but one sample of Belgium butter had a total TEQ level as high as 4.0 pg TEQ g(-1) l.w. Three out of five butter samples from Portugal showed similarly high PCDD/F TEQ levels. The sigmaPCB levels in European butter appeared to be somewhat higher than in the samples from the rest of the world. The average contribution of CB-153 to the total PCB concentration was 22% (SD 6.4, coefficient of variation 29%). Generally, the PCBs contributed around 60% of the total TEQ value, with CB-126 contributing approximately half of this value. This shows the important TEQ contribution from dioxinlike PCBs to the total TEQs. The highest HCB levels were found in butter samples from Russia, Ukraine, Belgium, and Slovenia. Low levels of HCB in butter were generally found in the Southern Hemisphere. Butter samples from countries from Eastern Europe had elevated sigmaDDT concentrations, with a particularly high concentration in Ukraine butter, followed by some Russian samples, Brazil, and the U.S.

Mixed Function Oxidase Activity and Organochlorine Levels in Farmed Sharpsnout Seabream (Diplodus puntazzo) from Two Intensive Aquaculture Facilities

Mixed function oxidase (MFO) activities and organochlorine levels were investigated in liver of farmed sharpsnout seabream bred in two intensive facilities, a sea farm and a land-based farm. The aim of this study is to investigate how different facility locations and breeding conditions might affect fish metabolic capabilities and accumulation of toxic chemicals in farmed sharpsnout seabream. The differences between breeding two or more fish species in the same cage or tank known as polyculture, and monoculture (1 species) were also investigated. The results showed that both facility location (sea and land) as well as breeding systems (polyculture and monoculture) might be responsible for the differences observed in both MFO enzyme activity and organochlorine levels. Significantly higher activities of two metabolizing enzymes such as 7-ethoxyresorufin-O-deethylase (EROD) and benzo(a)pyrene monooxygenase (B(a)PMO) were in fact recorded in land-based farmed fish than in sea farmed ones, and much higher in those from polyculture than in monoculture (p < 0.05). By contrast, the highest levels of dichlorodiphenyldichloroethilene (pp′DDE) and polychlorinated biphenyls (PCBs as Aroclor 1260) were measured in sea-farmed fish, except for hexachlorobenzene (HCB), which gave higher levels in land-based farmed fishes. No significant differences were observed between monoculture and polyculture in p,p′DDE and PCBs levels except for p,p′DDE which was significantly higher in monoculture than in polyculture (p < 0.05) in fish reared in tanks. Finally significantly higher HCB levels were measured in fish reared in monoculture in tanks (p < 0.05) and in polyculture in cages (p < 0.05). The low TEQ values obtained for PCB congeners at liver level indicated no concern for fish health.

Disruption of androgen regulation in the prostate by the environmental contaminant hexachlorobenzene.

Hexachlorobenzene (HCB) is a persistent environmental contaminant that has the potential to interfere with steroid hormone regulation. The prostate requires precise control by androgens to regulate its growth and function. To determine if HCB impacts androgen action in the prostate, we used a number of methods. Our in vitro cell-culture-based assay used a firefly luciferase reporter gene driven by an androgen-responsive promoter. In the presence of dihydrotestosterone, low concentrations (0.5-5 nM) of HCB increased the androgen-responsive production of firefly luciferase and high concentrations of HCB (> 10 microM) suppressed this transcriptional activity. Results from a binding assay showed no evidence of affinity between HCB and the androgen receptor. We also tested HCB for in vivo effects using transgenic mice in which the transgene was a prostate-specific, androgen-responsive promoter upstream of a chloramphenicol acetyl transferase (CAT) reporter gene. In 4-week-old mice, the proportion of dilated prostate acini, a marker of sexual maturity, increased in the low HCB dose group and decreased in the high HCB dose mice. In the 8-week-old mice, there was a significant decrease in both CAT activity and prostate weight upon exposure to 20 mg/kg/day HCB. Therefore, in vitro and in vivo data suggest that HCB weakly agonizes androgen action, and consequently, low levels of HCB enhanced androgen action but high levels of HCB interfered. Environmental contaminants have been implicated in the rising incidence of prostate cancer, and insight into the mechanisms of endocrine disruption will help to clarify their role.

Urinary porphyrin excretion in a human population highly exposed to hexachlorobenzene.

Data from an epidemic reported in Turkey (1955-1959) is the only information about the relationship between hexachlorobenzene (HCB) intake and porphyria cutanea tarda in humans. No information is available on the HCB threshold exposure level to induce porphyria cutanea tarda. To study HCB serum levels and urinary porphyrin excretion in the inhabitants of a village located near an organochlorine compound factory with high HCB concentrations in the air and to detect possible alterations in urinary porphyrin excretion and examine their relationship with HCB serum levels. Cross-sectional study. Unit of Porphyrias of a tertiary care facility in Barcelona, Spain. Six hundred four inhabitants of the village who were older than 14 years provided serum and urine samples (185 participants were factory workers). Serum HCB was analyzed by gas chromatography coupled to electron capture detection. Quantification of urinary total porphyrins was performed by spectrofluorimetry. Porphyrin profile was determined by high-pressure liquid chromatography. Hexachlorobenzene was detected in all serum samples (mean, 39.8 ng/mL; range, 1.1-1616.0 ng/mL), and levels were higher in factory workers. Mean +/- SD level urinary total porphyrin average concentration was 98 +/- 69 nmol/L (range, 9-1009 nmol/L). Only the urine sample with the highest porphyrin concentration showed an increase of highly carboxylated porphyrins, with a typical profile of porphyria cutanea tarda. In the remaining 603 urine samples, coproporphyrin was the predominant fraction. The airborne exposure to and increased body burden of HCB in the Flix village population are not enough to trigger a significant alteration of the heme biosynthesis pathway.

The occurrence of semivolatile persistent organic pollutants in ambient air in selected areas of slovakia

Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), hexachloro‐benzene (HCB) and p,p'‐DDE were analysed in ambient air collected in 1995—96 at 17 sampling sites situated in industrial, agricultural and forest areas. The concentrations of total PAHs (16 USEPA congeners) and seven carcinogenic congeners varied from 36 (a forest background location) to 689 ng m‐3 (in the vicinity of an iron and steel mill) and from 3.9 to 84 n gm‐3 , respectively. The highest total PCB concentrations were found in a town where PCBs were produced (11.3 ng m‐3), and at localities with heavy traffic (4.4 ng m‐3) and aluminium production (4.2 ngm‐3) while in agricultural areas they reached only 0.24 ngm‐3. In contrast, ambient air samples taken in agricultural areas contained the highest HCB levels (up to 4.7 ngm‐3). DDE concentrations were about 10‐times lower and ranged from 0.032 to 0.87 ngm‐3.

Hexachlorobenzene as a possible major contributor to the dioxin activity of human milk.

A dioxinlike compound is a compound that binds to the aryl hydrocarbon (Ah) receptor, results in dioxinlike effects, and bioaccumulates. These are the three factors for including dioxinlike chemicals in the toxic equivalency factor (TEF) concept. Risk assessment of dioxinlike compounds is based on using these TEFs. Hexachlorobenzene (HCB) has all three features and should therefore be included in this TEF concept. Relative potency values express the potency of a specific compound in comparison to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent dioxinlike compound, with a relative potency value of 1. For the estimation of the total dioxin activity in an environmental biological sample, the TEF value of a compound is multiplied by the concentration in the specific matrix. This results in a certain amount of toxic equivalents (TEQs) for this compound. The summation of all TEQs in a certain mixture gives the total dioxin activity of this mixture. HCB binds to the Ah receptor about 10,000 times less than TCDD. HCB is also about 10,000 times less potent than TCDD based on in vitro cytochrome P4501A induction and porphyrin accumulation. Using a relative potency value of 0.0001, HCB could add 10-60% to the total TEQ in human milk samples in most countries. In a few countries such as Spain, Slovakia, and the Czech Republic, HCB levels in human milk expressed as TEQ could contribute up to a factor of six to the total TEQ in comparison to the contribution of polychlorinated dioxins, dibenzofurans, and biphenyls together, i.e., up to a daily intake of about 1 ng TEQ/kg for a breast-fed infant. The HCB levels in human milk in these countries are about the same as in India. Biochemical, immunological, and neurological alterations have been observed in infants fed breast milk in countries with relatively low TEQ levels in human milk. Based on the above information, it is clear that HCB should be classified as a dioxinlike compound, that more studies are needed to reduce the uncertainty in the estimation of a relative potency value for HCB, and that epidemiological studies should be undertaken in infants fed breast milk in countries with high HCB exposure levels. Furthermore, measurements of HCB levels in human and environmental samples in conjunction with other dioxinlike compounds is a prerequisite to estimate the total dioxin activity in these samples.

Bioaccumulated Chlorinated Hydrocarbons and Red/White Blood Cell Parameters

The potential relationships between chlorinated hydrocarbon contamination in human serum and red/white blood cell profiles were investigated by multivariate techniques to assess the cellular response patterns to high and low organochlorine levels in the serum. Twenty-three healthy control subjects and fourteen patients with unexplained and persistent fatigue were divided on the basis of (a) high or low total organochlorine content, (b) high or low DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethene) content, and (c) high or low HCB (hexachlorobenzene) content. Discriminant function analysis revealed that the groups with high organochlorine content had significantly different red/white blood cell profiles compared with the low organochlorine groups ((a)P< 0.017, (b)P< 0.015, and (c)P< 0.0002). As a variable, the percentage of neutrophils was the most important discriminant parameter for differentiating between the high and low total organochlorine groups. Thirteen of the fourteen fatigued patients were characterized as “high total organocholorine content” (P< 0.04). The red cell distribution width was elevated in the high DDE group (P< 0.04) and was the most important discriminant parameter for differentiating between the high and low DDE groups. The percentage of eosinophils and the hemoglobin content were both reduced in the high HCB group (P< 0.009,P< 0.003, respectively) and the percentage of eosinophils was the most important discriminant parameter for differentiating between the high and low HCB groups. Those patients with unexplained and persistent fatigue had significantly higher levels of DDE compared with the controls and had different specific blood cell responses to organochlorines compared with control subjects.

HCB Load on Suspended Solids and in Sediments of the River Rhine

At the ICPR monitoring station Koblenz (Rhine-km 590.3) the load of hexachlorobenzene (HCB) on suspended solids has been measured for several years. In addition, sediments from impoundments on the Upper Rhine were analysed for HCB. The results show that the HCB load on suspended solids in the river Rhine has decreased to nearly half the initial value between 1985 and 1991. The still relatively high HCB concentrations amounting in average to 40 µg/kg on the suspended solids sampled at Koblenz can only be explained by recalling that sediments in the impoundments and in other contaminated sites of the Upper Rhine constitute a historic HCB storage, which contributes to the HCB load on suspended solids through remobilization during flood events. With regard to future trend monitoring activities for HCB in suspended solids, a minimum sampling interval of 14 days is recommended.

Epidemiology of hexachlorobenzene-induced porphyria in Turkey: clinical and laboratory follow-up after 25 years.

Cutanea tarda and mixed porphyric symptoms resulted from accidental ingestion of hexachlorobenzene (HCB)-treated seed grain in Turkey 25 years ago and involved about 4,000 persons with a 10% mortality. Twenty-five years later, 161 patients, 63 women and 98 men, with histories of HCB exposure as children or young adults were studied. Many patients had persistent abnormal porphyrin metabolism and prominent neurological, dermatologic, and orthopedic symptoms and signs. Thyromegaly was seen in 60% of the women and 27% of the men. The children born to porphyric mothers 25 years ago all died of pembe yara secondary to maternal milk and transplacental transfer of HCB. Current lactation specimens of porphyric patients show high HCB levels, up to 3.12 ppm, but the infant offspring appear normal.