Serum dioxin levels in former chlorophenol workers

BDE-209 and TCDD enhance metastatic characteristics of melanoma cells after chronic exposure

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) and BDE-209 (decabromodiphenyl ether) are persistent organic pollutants (POPs) produced by industrial activities and associated with several diseases. TCDD is a known human carcinogen, but few studies investigated about the effects of exposure to both compounds, i.e., whether BDE-209 and TCDD can render tumor cells more aggressive and metastatic. In the current study we investigated if the exposure of B16-F1 and B16-F10 melanoma murine cells to environmental relevant concentrations of TCDD and BDE-209 at 24 h and 15-day exposure modulates the expression of genes related to metastasis, making the cells more aggressive. Both pollutants did not affect cell viability but lead to increase of cell proliferation, including the upregulation of vimentin, MMP2, MMP9, MMP14 and PGK1 gene expression and downregulation of E-cadherin, TIMP2, TIMP3 and RECK, strongly suggesting changes in cell phenotypes defined as epithelial to mesenchymal transition (EMT) in BDE-209 and TCDD-exposed cells. Foremost, increased expression of metalloproteinases and decreased expression of their inhibitors made B16-F1 cells similar the more aggressive B16-F10 cell line. Also, the higher secretion of extracellular vesicles by cells after acute exposure to BDE-209 could be related with the phenotype changes. These results are a strong indication of the potential of BDE-209 and TCDD to modulate cell phenotype, leading to a more aggressive profile.

TCDD promotes liver fibrosis through disordering systemic and hepatic iron homeostasis

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is a toxic environmental pollutant which can cause severe health problems, such as fibrosis. However, the toxic effects and related mechanism of TCDD on the liver remain largely unknown. In this study, we established a liver fibrosis mouse model upon exposure of TCDD, as evidenced by increased collagen I, tumor growth factor β1 (TGFβ1), α-smooth muscle actin (α-SMA), and Masson staining. Meanwhile, there was also a significant increase of inflammatory factors and TUNEL-positive hepatocytes in liver, indicating that liver inflammation and hepatic cell apoptosis occurred. In addition, increased serum and liver iron were concomitant with liver injury induced by TCDD. We further investigated the mechanism underlying TCDD-induced hepatocyte apoptosis through apoptosis polymerase chain reaction array, and found that a crucial apoptosis-related gene, cell death-inducing DFF45-like effector b (Cideb), was significantly increased in primary hepatocytes from TCDD-exposed mice, and accompanied by liver iron deposition in hepcidin knockout mice. Therefore, Cideb depletion could effectively attenuated TCDD or iron induced cell death related genes expression. In conclusion, our results showed that iron-induced Cideb expression played a critical role in promoting TCDD-induced hepatocyte apoptosis and liver fibrosis, which provide a novel mechanism for understanding TCDD-induced liver injury.

Non‑infective occupational risk factors for hepatocellular carcinoma: A review (Review)

Liver cancer is the second leading worldwide cause of cancer‑associated mortalities. Hepatocellular carcinoma, which accounts for the majority of liver tumors, ranks fifth among types of human cancer. Well‑established risk factors for liver cancer include the hepatitis B and C viruses, aflatoxins, alcohol consumption, and oral contraceptives. Tobacco smoking, androgenic steroids, and diabetes mellitus are suspected risk factors. Current knowledge regarding non‑infective occupational risk factors for liver cancer is inconclusive. The relevance of liver disorders to occupational medicine lies in the fact that the majority of chemicals are metabolized in the liver, and toxic metabolites generated via metabolism are the predominant cause of liver damage. However, their non‑specific clinical manifestations that are similar in a number of liver diseases make diagnosis difficult. Furthermore, concomitant conditions, such as viral hepatitis and alcohol or drug abuse, may mask liver disorders that result from occupational hepatotoxic agents and block the demonstration of an occupational cause. The identification of environmental agents that result in human cancer is a long and often difficult process. The purpose of the present review is to summarize current knowledge regarding the association of non‑infective occupational risk exposure and HCC, to encourage further research and draw attention to this global occupational public health problem.

Skin diseases associated with Agent Orange and other organochlorine exposures

Organochlorine exposure is an important cause of cutaneous and systemic toxicity. Exposure has been associated with industrial accidents, intentional poisoning, and the use of defoliants, such as Agent Orange in the Vietnam War. Although long-term health effects are systematically reviewed by the Institute of Medicine, skin diseases are not comprehensively assessed. This represents an important practice gap as patients can present with cutaneous findings. This article provides a systematic review of the cutaneous manifestations of known mass organochlorine exposures in military and industrial settings with the goal of providing clinically useful recommendations for dermatologists seeing patients inquiring about organochlorine effects. Patients with a new diagnosis of chloracne, porphyria cutanea tarda, cutaneous lymphomas (non-Hodgkin lymphoma), and soft-tissue sarcomas including dermatofibrosarcoma protuberans and leiomyosarcomas should be screened for a history of Vietnam service or industrial exposure. Inconclusive evidence exists for an increased risk of other skin diseases in Vietnam veterans exposed to Agent Orange including benign fatty tumors, melanomas, nonmelanoma skin cancers, milia, eczema, dyschromias, disturbance of skin sensation, and rashes not otherwise specified. Affected veterans should be informed of the uncertain data in those cases. Referral to Department of Veterans Affairs for disability assessment is indicated for conditions with established associations.

"Intrinsic" elimination rate and dietary intake estimates for selected indicator PCBs: toxicokinetic modeling using serial sampling data in US subjects, 2005-2010

Changes in measured concentrations of persistent compounds such as polychlorinated biphenyls (PCBs) in an individual over time reflect not only intrinsic elimination rates but also any ongoing intake of the compounds and changes in the volume of distribution. Thus, "apparent" elimination rates calculated from data on changes in serum lipid-adjusted concentration may over- or under-estimate the "intrinsic" elimination rates for such compounds. Serum PCB concentrations were measured in 43 individuals approximately 5years apart. Changes in measured concentrations and body weights were used to estimate mass-based apparent elimination rates. The changes in estimated body mass of PCBs 105, 118, 138, 153, and 180 were input into a simple first-order model employing previously estimated intrinsic elimination rates to estimate congener-specific average dietary intake rates over the period between samples. Calculated median dietary intakes were compared to previous estimates. Intrinsic elimination rates were adjusted for two congeners. The analyses support central tendencies of intrinsic elimination rates of approximately 5years for PCBs 105 and 118, 11years for PCB 138, 14.4years for PCB 153, and 20years or more for PCB 180. Estimated dietary intakes for this population and time period depend on the assumed intrinsic elimination rates and range from 0.1ngkg(-1)d(-1) for PCB 105 to approximately 1-2ngkg(-1)d(-1) for PCB 180. Estimated body burdens of PCB 180 changed very little over the five-year period, suggesting near steady-state exposure levels. As a result, estimates for both elimination half-life and ongoing intake rates for this congener are highly uncertain.

Risk ranking priority of carcinogenic and/or genotoxic environmental contaminants in food in Belgium

This paper focuses on the risks of environmental carcinogenic and/or genotoxic contaminants in food. It describes, for each contaminant studied, the carcinogenicity and genotoxicity, the toxicological reference values, the exposure and the risk characterisation. The compounds studied were classified into 3 categories based on a risk assessment. Effects others than carcinogenicity and/or genotoxicity (e.g. endocrine disruption activity) were also taken into account for the classification. Given the low margin of exposure values for arsenic and lead, these two compounds are classified as priority 1 (high concern) for food safety and as a first priority to take actions to reduce exposure. Cadmium, methylmercury, dioxins and dioxin-like polychlorinated biphenyls (PCB), non-dioxin-like PCB and toxaphene are classified as priority 2 (medium concern). Polybrominated biphenyls, chlordane, heptachlor, dichlorodiphenyltrichloroethane (DDT) and metabolites, hexachlorobenzene, hexachlorocyclohexane (lindane included), polychlorophenols and their salts are classified as priority 3 (low concern).

Elimination rates of dioxin congeners in former chlorophenol workers from Midland, Michigan

BACKGROUND

Exposure reconstructions and risk assessments for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other dioxins rely on estimates of elimination rates. Limited data are available on elimination rates for congeners other than TCDD.

OBJECTIVES

We estimated apparent elimination rates using a simple first-order one-compartment model for selected dioxin congeners based on repeated blood sampling in a previously studied population.

METHODS

Blood samples collected from 56 former chlorophenol workers in 2004-2005 and again in 2010 were analyzed for dioxin congeners. We calculated the apparent elimination half-life in each individual for each dioxin congener and examined factors potentially influencing elimination rates and the impact of estimated ongoing background exposures on rate estimates.

RESULTS

Mean concentrations of all dioxin congeners in the sampled participants declined between sampling times. Median apparent half-lives of elimination based on changes in estimated mass in the body were generally consistent with previous estimates and ranged from 6.8 years (1,2,3,7,8,9-hexachlorodibenzo-p-dioxin) to 11.6 years (pentachlorodibenzo-p-dioxin), with a composite half-life of 9.3 years for TCDD toxic equivalents. None of the factors examined, including age, smoking status, body mass index or change in body mass index, initial measured concentration, or chloracne diagnosis, was consistently associated with the estimated elimination rates in this population. Inclusion of plausible estimates of ongoing background exposures decreased apparent half-lives by approximately 10%. Available concentration-dependent toxicokinetic models for TCDD underpredicted observed elimination rates for concentrations < 100 ppt.

CONCLUSIONS

The estimated elimination rates from this relatively large serial sampling study can inform occupational and environmental exposure and serum evaluations for dioxin compounds.

Blood levels of dioxins, furans, dioxin-like PCBs, and TEQs in general populations: a review, 1989-2010

A comprehensive worldwide literature review of blood levels of dioxins and dioxin-like compounds in non-exposed adult general populations was performed. The studies published in 1989-2010 reporting information on polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), non-ortho-PCBs (nPCBs), mono-ortho-PCBs (mPCBs) levels and Toxic Equivalencies (TEQs, a summary weighted measure of their combined toxicity) were reviewed. TEQs were calculated using as standard the most recent WHO 2005 reevaluation of Toxic Equivalency Factors (TEFs). Weighted multiple regression analyses adjusted for year, subject's age, type of sample analyzed, method used for values below detection limit, and central tendency measure used were performed for each congener and standardized TEQs (log-transformed). We identified 187 studies regarding 29,687 subjects of 26 countries. Year of blood collection ranged from 1985 to 2008. The studies reporting congener levels 161. In adjusted analyses, European countries showed higher levels of most dioxin-like congeners and TEQs. A strong positive association of subjects' age with most congeners and with TEQ values was found, confirming previous findings. Significant decreases over time (1985-2008) were documented for PCCDs, PCDFs, and TEQs including their contributions. No significant decrease was found for non-ortho-PCBs, notably PCB 126. Only some mono-ortho-PCBs showed clear significant declines. Accordingly, TEQs including only PCB contribution did not decrease over time. In interpreting these findings, it should be considered that for dioxin-like PCBs the analysis period was shorter (17 years), since these compounds were first measured in 1992.

Biochemical study of retired pentachlorophenol workers with and without following dietary exposure to PCDD/Fs

PCDD/Fs are found as impurities in commercial pesticide sodium pentachlorophenol (Na-PCP) salt. We compared, using multivariate logistic regression analysis adjusted for confounding factors, serum PCDD/F levels and biochemical examinations of retired Na-PCP workers and other inhabitants living near a closed Na-PCP plant that discharged PCP-contaminated wastewater into a nearby pond in Tainan, Taiwan. In this cross-sectional study from October 2006 through May 2009, 1167 participants were divided into groups according to their occupational (retired Na-PCP plant workers versus other residents) and dietary exposure (eating polluted fish versus not eating polluted fish) to PCDD/Fs, and a general population from a large-scale survey. Serum PCDD/F levels were significantly different between these groups (range: from 22.9±10.0pg WHO(98)-TEQ(DF) g(-1) lipid in the general population to 109.6±94.5pg WHO(98)-TEQ(DF) g(-1) lipid in retired Na-PCP workers eating polluted seafood; P(trend)<0.001). Distinct patterns of PCDD/Fs congener profiles, showing a significantly higher proportion of 1,2,3,7,8-PeCDD, 1,2,3,6,7,8-HxDD, and less 2,3,4,6,7,8-HpCDF, OCDF, were also found among workers and residents with different serum PCDD/F levels versus the general population. After adjusting for confounding factors, glucose (adjusted odds ratio [AOR] 7.22 [95% CI: 4.04-12.90]), triglycerides (AOR 4.31 [95% CI: 2.57-7.22]), blood urea nitrogen (AOR 2.90 [95% CI: 1.58-5.33]), creatine (AOR 5.83 [95% CI: 1.12-30.30]) and total protein (AOR 3.74 [95% CI: 1.91-7.31]) levels in retired workers were significantly higher than in the reference group. Occupational exposure to PCDD/Fs is associated with biochemical abnormalities that may persist for years after serum PCDD/F levels have declined.

TCDD exposure estimation for workers at a New Zealand 2,4,5-T manufacturing facility based on serum sampling data

Employment in the manufacture of the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) is associated with potential exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and elevated serum lipid TCDD concentrations can be measured in workers for decades after terminated occupational exposure. As part of an epidemiological study of 1599 workers employed at a facility in New Plymouth, New Zealand that manufactured 2,4,5-T, serum TCDD concentrations measured in blood samples from 346 workers were used with work history records and a simple pharmacokinetic model in a linear regression to estimate dose rates associated with specific job exposure groups at the facility. The model was used to estimate serum TCDD concentration profiles over time for each individual in the full study group and accounted for 30% of the observed variance in TCDD concentrations in the serum donor subgroup. The model underestimated measured concentrations substantially for eleven individuals in the study group; examination of questionnaire data revealed a variety of activities apart from routine employment at the facility that may have contributed to the measured serum TCDD concentrations. Estimated serum TCDD concentrations were below 300 p.p.t. for all individuals in the cohort over the entire study time period, lower than estimates for other 2,4,5-T worker populations. This finding is consistent with occupational medicine records, which indicated that no cases of chloracne were ever diagnosed among workers employed on the site. The modeled exposures will be used in an evaluation of mortality patterns of workers at this facility.

Hierarchical cluster analysis of polychlorinated dioxins and furans in Michigan, USA, soils: evaluation of industrial and background congener profiles

As part of the University of Michigan Dioxin Exposure Study, soil samples were collected from 766 residential properties near the Tittabawassee River between Midland and Saginaw; near the Dow Chemical Facility in Midland; and, for comparison, in the other areas of Midland and Saginaw Counties and in Jackson and Calhoun Counties, all located in the state of Michigan, USA. A total of 2,081 soil samples were analyzed for 17 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). In order to better understand the distribution and sources of the PCDD/F congeners in the study area, hierarchical cluster analysis (HCA) was used to statistically group samples with similar congener patterns. The analysis yielded a total of 13 clusters, including: 3 clusters among the soils impacted by contamination present in the Tittabawassee River sediments, a cluster comprised mainly of samples collected within the depositional area of the Dow incinerator complex, a small cluster of samples with elevated 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD), and several clusters exhibiting background patterns. The clusters related to the Tittabawassee River floodplain contamination all contained elevated PCDF levels and were differentiated from one another primarily by their relative concentrations of higher-chlorinated PCDDs, a difference likely related to both extent and timing of impacts from Tittabawassee sediments. The background clusters appear to be related to combustion processes and are differentiated, in part, by their relative fractions of TCDD. Thus, HCA was useful for identifying congener profile characteristics in both contaminated and background soil samples.

Serum concentrations of chlorinated dibenzo-p-dioxins and dibenzofurans among former New Zealand trichlorophenol workers

This study examined serum levels of 2,3,7,8-substituted chlorinated dioxins and furans, and 15 PCBs for 346 New Zealand employees who worked at a site that manufactured 2,4,5-trichlorophenol (TCP) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T). Participants with potential TCP or 2,4,5-T exposures had mean lipid-adjusted 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) levels of 9.9 ng kg(-1) lipid compared to 4.9 ng kg(-1) for workers with no exposure at the site. Among exposed workers, we found evidence of differences in 2,3,7,8-TCDD levels by department and duties. Workers involved in an accidental release had the highest mean 2,3,7,8-TCDD levels, 37.9 ng kg(-1), followed by workers in the trichlorophenol plant, 23.4 ng kg(-1). Workers with potential intermittent exposures to 2,3,7,8-TCDD in construction, maintenance, mechanics, and transport had 2,3,7,8-TCDD levels above New Zealand background levels of 3.9 ng kg(-1), indicating workplace exposures. Among participants with work history indicating no 2,3,7,8-TCDD exposures, we observed some individuals with 2,3,7,8-TCDD levels above background levels. However, in most cases, these workers reported workplace exposures not recorded on their work histories or held other jobs with the potential for 2,3,7,8-TCDD exposures outside the plant. All other dioxin, furan, and PCB levels were similar among the exposed and unexposed workers.

Serum dioxin levels in former New Zealand sawmill workers twenty years after exposure to pentachlorophenol (PCP) ceased

From the 1950s to the late 1980s pentachlorophenol (PCP) based anti-sapstain fungicides were widely used in the New Zealand timber industry. Workers involved in treatment, or those handling freshly treated timber, experienced significant PCP exposure. Commercial grade PCP contained contaminants including 2,3,7,8-substituted polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners. To determine whether PCP exposure had resulted in elevated serum dioxin levels twenty years after its use had ceased we tested 94 former sawmill workers randomly selected from surviving members of a cohort enumerated for a mortality and cancer incidence study. After interviewing these individuals to collect demographic data and a comprehensive work history, they were divided into 71 PCP-exposed and 23 non-exposed individuals on the basis of job title and work tasks performed. We compared age-adjusted dioxin levels in the exposed and non-exposed groups, examined the effect of PCP exposure duration and intensity, and compared congener profiles with those found in the commercial grade PCP used at the time. Mean levels in exposed workers were elevated when compared with the non-exposed, with levels of 1,2,3,6,7,8-HxCDD, 1,2,3,4,6,7,8-HpCDD and OCDD being two to three times higher. The congener profiles in serum were consistent with those in PCP solutions, and dioxin levels increased with both employment duration and estimated exposure intensity. Serum dioxin levels in former New Zealand sawmill workers remain elevated twenty years after exposure to PCP ceased, and reflect the pattern of past PCP exposure.

Chlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyl profiles of workers with trichlorophenol and pentachlorophenol exposures

We examined the serum lipid adjusted levels of 2,3,7,8-substituted chlorinated dioxins and furans, and four coplanar PCBs for 98 workers. We found workers who worked only in the trichlorophenol units had mean lipid adjusted 2,3,7,8-TCDD levels of 36.8 ppt significantly higher (p<0.05) than 6.0 ppt in the reference group. Workers who worked only in the pentachlorophenol units had mean lipid adjusted levels for 123478-HxCDD of 14.8 ppt, 123678-HxCDD of 156.4 ppt,123789-HxCDD of 23.7 ppt, 1234678-HpCDD of 234.6 ppt, and OCDD of 2,778.2 ppt significantly higher (p<0.05) than the reference group levels for the same congeners of 7.5, 71.8, 8.0, 67.5, and 483.2 ppt, respectively. While we did find 12378-PeCDD levels higher than the reference group in trichlorophenol and pentachlorophenol workers, the differences are small, and could be attributed to normal variation. All furan levels among the trichlorophenol or pentachlorophenol only workers were not significantly different than the reference group. Workers with both trichlorophenol and pentachlorophenol exposures had mean dioxin levels consistent with complex chlorophenol exposures. Tradesmen who worked throughout the plant had congener profiles consistent with both trichlorophenol and pentachlorophenol exposures. PCB 169, 23478-PeCDF, 123478-HxCDF, and 123678-HxCDF levels were also significantly greater (p<0.05) in these tradesmen than in the reference group. We found distinct patterns of dioxin congeners many years after exposure among workers with different chlorophenol exposures. We were effectively able to distinguish past trichlorophenol exposures from pentachlorophenol exposures based on differing serum dioxin profiles among workers.

Serum concentrations of chlorinated dibenzo-p-dioxins and dibenzofurans among former Michigan trichlorophenol and pentachlorophenol workers

This study examines serum levels of 2,3,7,8-substituted chlorinated dioxins and furans, and PCBs for 375 Michigan workers with potential chlorophenol exposure, 37 Worker Referents, and 71 Community Referents. The chlorophenol workers were last exposed to trichlorophenol and/or pentachlorophenol 26-62 years ago. Employees working only in the trichlorophenol units had mean lipid-adjusted 2378-tetrachlorodibenzo-p-dioxin (TCDD) levels of 15.9 ppt compared with 6.5 ppt in the Worker Referents. Employees working only in the pentachlorophenol units had mean lipid-adjusted levels for 123478-H6CDD of 16.1 ppt, 123678-H6CDD of 150.6 ppt, 123789-H6CDD of 20.2 ppt, 1234678-H7CDD of 192.6 ppt, and OCDD of 2,594.0 ppt compared with the Worker Referent levels for the same congeners of 7.5, 74.7, 8.6, 68.7, and 509.1 ppt, respectively. All furan and PCB levels among workers in the trichlorophenol and/or pentachlorophenol departments were similar to the Worker Referents. The Tradesmen who worked throughout the plant had dioxin congener profiles consistent with both trichlorophenol and pentachlorophenol exposures. PCB levels and levels of 23478-P5CDF, 123478-H6CDF, and 123678-H6CDF were also greater in these Tradesmen than in the Worker Referents. The Worker Referent group had higher levels of dioxins and furans than the Community Referents indicating the potential for exposure outside the chlorophenol departments at the site. Distinct patterns of dioxin congeners were found many years after exposure among workers with different chlorophenol exposures. Furthermore, past trichlorophenol exposures were readily distinguishable from past pentachlorophenol exposures based on serum dioxin evaluations among workers. These data can be used to better assess dioxin exposures in future health studies.

Body mass index and serum chlorinated dibenzo-p-dioxin and dibenzofuran levels

Several studies have found that current levels of 2,3,7,8 tetrachlorodibenzo-p-dioxin in serum lipids are related to age with older persons generally having higher levels. To account for this age pattern, reference ranges based on national samples have been established in order to allow determination of background levels for regional studies. In several studies, body mass index (BMI), has also been associated with current 2,3,7,8 tetrachlorodibenzo-p-dioxin levels with increasing body mass index related to increasing levels. We measured lipid-adjusted serum levels for all 2,3,7,8-substituted dioxins and furans in 62 chemical manufacturing workers with chlorophenol exposures and 36 workers without chlorophenol exposures employed at the same location. We then assessed the impact of age and BMI on the serum levels of all these compounds in the presence of other potential confounders. We found that both factors are important independent determinants of serum levels of 2,3,7,8-substituted dioxins and furans. Specifically, age and BMI are both important factors for assessing background levels of 2,3,7,8 tetrachlorodibenzo-p-dioxin, 1,2,3,7,8 pentachlorodibenzo-p-dioxin and the calculated total toxic equivalency. BMI, but not age, is important for assessing background levels of higher chlorinated dioxins and some hexachlorofurans. We conclude that age and BMI are both important considerations when comparing a potentially exposed group to a referent group, or to national norms. Further, age and BMI may also be important in epidemiology studies where back-extrapolation from current dioxin levels is used to assess historical chlorophenol exposure.