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

Bio-accumulation of organic contaminants in Indo-Pacific humpback dolphins: Preliminary unique features of the brain and testes

There is little information about the residue levels and congener composition of organic contaminants (OCs) in cetaceans. In the present study, we investigated the polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in the blubber, blood, brain and testes of Indo-Pacific humpback dolphins (Sousa chinensis) stranded in the Pearl River Estuary (PRE), China. The lowest blubber/tissue partition coefficients were found for sum hexachlorocyclohexanes (ΣHCHs) and ΣPAHs, while the highest were in ΣPCBs and sum dichlorodiphenyltrichloroethanes (ΣDDTs), likely attributing to the octanol-water partition features. The low levels of OCs in brain and testes theoretically resulted from the blood-brain barrier, blood-testes barrier, contaminant molecule dimensions and unique lipid compositions in the brain and testes. Compared with other contaminants, the higher mean brain/blood and testes/blood partition coefficients found for mirex, heptachlor, dieldrin and endrin would increase the risks associated with exposure-related toxicity and the bioavailability of contaminants within these tissues. Observations also suggest that as lipid mobilizes from blubber, contaminants may redistribute, leading to elevated tissue (such as brain) concentrations. Therefore, dolphins with less blubber may be more susceptible to health risks. The Indo-Pacific humpback dolphins living in PRE are at great risk due to variety of OCs in indirect contact with non-target organisms, affecting the health of animals (toxic effects and accumulation). Our findings contribute to the knowledge of the potential effects of OCs exposure on developmental neurotoxicity and reproductive damage in marine mammals.

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.

Hepatocellular carcinoma and the risk of occupational exposure

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. The main risk factors for HCC are alcoholism, hepatitis B virus, hepatitis C virus, nonalcoholic steatohepatitis, obesity, type 2 diabetes, cirrhosis, aflatoxin, hemochromatosis, Wilson's disease and hemophilia. Occupational exposure to chemicals is another risk factor for HCC. Often the relationship between occupational risk and HCC is unclear and the reports are fragmented and inconsistent. This review aims to summarize the current knowledge regarding the association of infective and non-infective occupational risk exposure and HCC in order to encourage further research and draw attention to this global occupational public health problem.

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.

Cancer incidence in a chlorochemical plant in Isère, France: an occupational cohort study, 1979-2002

BACKGROUND

A major French chlorine chemical plant (chlor-alkali process with diaphragm cell and manufacturing of organochlorine chemicals) has used or produced known or suspected carcinogenic compounds.

METHODS

A cohort study, based on the plant occupational health service and the regional cancer registry, analyzed the standardized incidence ratios of malignant tumors for the period 1979-2002. Individual exposures were estimated from workers' occupational histories in a dual division of jobs into 9 sectors and 115 workshops with known exposures.

RESULTS

Men (2,742) were followed, corresponding to 52,794 person-years. Primary tumors (304) were observed for 290 expected cases, a non-significant 5% excess. A significant excess was found of pleural mesothelioma and bladder cancer in employees hired before 1964.

CONCLUSION

Excesses of mesothelioma and bladder cancer were found, whereas there was no excess of hematopoietic cancers despite high benzene and dioxin exposures. Surprisingly, mesothelioma cases did not include workers who were the most exposed to asbestos.