Morbidity follow up study of BASF employees exposed to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) after a 1953 chemical reactor incident

Chlordane exposure causes developmental delay and metabolic disorders in Drosophila melanogaster

The incidence of metabolic diseases is increasing every year, and several studies have highlighted the activity of persistent organic pollutants (POPs) in causing hyperlipidemia and diabetes, and these compounds are considered to be endocrine disrupting chemicals (EDCs). Chlordane is classified as an endocrine disruptor, but the mechanism of how it functions is still unclear. This study investigates the effects of chlordane exposure on Drosophila larvae. Drosophila was cultured in diet containing 0.01 μM, 0.1 μM, 1 μM, 5 μM, and 10 μM chlordane, and the toxicity of chlordane, the growth and development of Drosophila, the homeostasis of glucose and lipid metabolism and insulin signaling pathway, lipid peroxidation-related indicators and Nrf2 signaling pathway were evaluated. We here found that exposure to high concentrations of chlordane decreased the survival rate of Drosophila and that exposure to low concentrations of chlordane caused disruption of glucose and lipid metabolism, increased insulin secretion and impairment of insulin signaling. Notably, it also led to massive ROS production and lipid peroxidation despite of the activation of Nrf2 signaling pathway, an important pathway for maintaining redox homeostasis. Collectively, chlordane causes lipid peroxidation and disrupts redox homeostasis, which may be a potential mechanism leading to impaired insulin signaling and the metabolism of glucose and lipid, ultimately affects Drosophila development.

Severe dioxin-like compound (DLC) contamination in e-waste recycling areas: An under-recognized threat to local health

Electrical and electronic waste (e-waste) burning and recycling activities have become one of the main emission sources of dioxin-like compounds (DLCs). Workers involved in e-waste recycling operations and residents living near e-waste recycling sites (EWRS) are exposed to high levels of DLCs. Epidemiological and experimental in vivo studies have reported a range of interconnected responses in multiple systems with DLC exposure. However, due to the compositional complexity of DLCs and difficulties in assessing mixture effects of the complex mixture of e-waste-related contaminants, there are few studies concerning human health outcomes related to DLC exposure at informal EWRS. In this paper, we have reviewed the environmental levels and body burdens of DLCs at EWRS and compared them with the levels reported to be associated with observable adverse effects to assess the health risks of DLC exposure at EWRS. In general, DLC concentrations at EWRS of many countries have been decreasing in recent years due to stricter regulations on e-waste recycling activities, but the contamination status is still severe. Comparison with available data from industrial sites and well-known highly DLC contaminated areas shows that high levels of DLCs derived from crude e-waste recycling processes lead to elevated body burdens. The DLC levels in human blood and breast milk at EWRS are higher than those reported in some epidemiological studies that are related to various health impacts. The estimated total daily intakes of DLCs for people in EWRS far exceed the WHO recommended total daily intake limit. It can be inferred that people living in EWRS with high DLC contamination have higher health risks. Therefore, more well-designed epidemiological studies are urgently needed to focus on the health effects of DLC pollution in EWRS. Continuous monitoring of the temporal trends of DLC levels in EWRS after actions is of highest importance.

The Protective Effect of α-Tocopherol on the Content of Selected Elements in the Calvaria for Exposed Hens to TCDD in the Early Embryonic Period

This paper focuses on negative effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on element content in male chicken calvaria and α-tocopherol (vitamin E) ability to reduce its toxic potential on bone mineralization in offspring. In the experiment carried out once, a solution containing only DMSO, TCDD, TCDD + α-tocopherol, and exclusively α-tocopherol was administrated. Subsequently, on the 5th day after hatching, the mineral composition of the chicken calvaria was evaluated. The results obtained suggest that the use of α-tocopherol contributes to the maintenance of the concentration of calcium, magnesium, and manganese in the chicken calvaria treated with TCDD in the embryonic period. In turn, vitamin E increases the level of zinc. It has been found that α-tocopherol in chicken embryos has a protective effect against disturbance of level of chosen trace elements in the bones of offspring caused by the TCDD.

Plasma Oligomeric Beta Amyloid in Alzheimer's Disease with History of Agent Orange Exposure

BACKGROUND AND PURPOSE

During the Vietnam War, many Korean soldiers were exposed to Agent Orange. Until now, there existed only limited evidence of association between exposure to Agent Orange and Alzheimer's disease (AD). The main pathological feature of AD is brain amyloidosis. To explore the pathophysiological characteristic of AD with Agent Orange exposure, we compared newly developed amyloid beta (Aβ) oligomer levels in plasma between AD with Agent Orange exposure and without exposure.

METHODS

We recruited 48 AD patients with Agent Orange exposure and 66 AD patients without Agent Orange. Using the Multimer Detection System technique, which was based on an enzyme-linked immunosorbent assay, we measured Aβ oligomers in the plasma of study subjects.

RESULTS

Compared to normal control patients, plasma Aβ oligomer levels were higher in AD patients regardless of history of Agent Orange exposure. However, AD patients with Agent Orange exposure showed higher plasma Aβ oligomer levels than AD patients without Agent Orange.

DISCUSSION

This study showed higher plasma Aβ oligomer levels in AD patients with Agent Orange exposure compared to AD patients without Agent Orange. This finding suggests the possibility of a different pathophysiology of AD patients with Agent Orange exposure from AD patients without Agent Orange.

Combat zone exposure and respiratory tract disease

BACKGROUND

The impact of deployment to combat zones on the respiratory and sinonasal health of U.S. soldiers is an emerging public health concern. Retrospective studies have shown a correlation between deployment and development of post-deployment pathology, particularly of the aerodigestive system. Respiratory disease, including sinusitis, allergic rhinitis, and asthma, are commonly reported in soldiers deployed to the Middle East and Southwest Asia.

METHODS

Current literature pertaining to combat zone exposure and development of respiratory disease was retrieved using PubMed, Embase, Web of Science, and Google Scholar.

RESULTS

Several types of combat zone exposures exist that may play an influential role in the development of upper and lower respiratory tract diseases. Exposures including foreign dusts, harsh environments, particulate size, and close living quarters may play a causative role. The effect of combat zone exposures has been better examined for lower respiratory tract diseases; however, with the theory of the unified airway, the upper respiratory tract may also be involved. There is evidence that the upper respiratory tract is susceptible, with an increased risk for development of sinusitis and sinonasal disease; however, the quality of evidence of the present literature is generally low.

CONCLUSION

More research is necessary to determine a pathophysiologic mechanism between combat zone exposure and the development of sinonasal disease. Practicing otolaryngologists should be aware of the possibility of combat zone exposures that could contribute to rhinologic symptomatology.

[Pesticides and hypothyroidism in farmers of plantain and coffee growing areas in Quindio, Colombia]

OBJECTIVES

To establish the correlation between hypothyroidism and blood pesticide levels.

MATERIALS AND METHODS

Cross-sectional study in agricultural workers and their permanent partners in plantain and coffee producing municipalities as reference population. A representative sample was estimated and thyroid function tests were performed using ELISA Stat Fax 303/Plus reader, at a wavelength of 450 nm. Organochlorine pesticide residuality was determined, a dispersive liquid-liquid microextraction (DLLME) assisted by sonication was implemented, and a gas chromatography-micro-electron capture detector (GC-pECD) was used for the analysis.

RESULTS

819 participants, 58.7% men and 41.3% women were included; their average age was 48.1 years. Prevalence of symptomatic hypothyroidism (1.2%) and subclinical hypothyroidism (6.7%) was observed, with a higher prevalence in people older than 60 years (2.6% and 8.9%, respectively). Non-causal association was found between subclinical hypothyroidism and the organochlorine pesticides 4,4'-DDE (sig.0,006), Heptachlor (sig.0,04), and Endosulfan I (sig.0,02). Antiperoxidase (Anti TPO) antibodies ≥60 lU/ml were associated with subclinical hypothyroidism (OR 2.6).

CONCLUSIONS

The prevalence of hypothyroidism in the studied population is similar to that reported in the literature, and lower than in urban areas. In turn, the prevalence of subclinical hypothyroidism is higher and positive anti-TPO values are related to risk of progression to frank hypothyroidism, which is why follow-up is required in these patients. Three organochlorine pesticides were associated with subclinical hypothyroidism. TSH screening is recommended in people aged 40 and over, especially if they are exposed to the aforementioned agrochemicals.

Morbidity in New Zealand pesticide producers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

OBJECTIVES

To conduct a cross-sectional morbidity survey among 245 former employees of a pesticide production plant exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in New Zealand.

METHODS

Demographic factors and health information were collected in face-to-face interviews. TCDD, lipids, thyroid hormones, glucose and immunoglobulin G (IgG) were determined in non-fasting blood. For 111 participants, a neurological examination was conducted. Associations between health outcomes and working in a TCDD exposed job (prevalence 49%) and serum TCDD concentration≥10pg/g lipid (18%) were assessed using logistic regression whilst controlling for age, gender, smoking, body mass index and ethnicity.

RESULTS

Diabetes was more common in those who had worked in TCDD exposed jobs (OR 4.0, 95%CI 1.0-15.4) and in those with serum TCDD ≥10pg/g (OR 3.1, 95%CI 0.9-10.7). Non-fasting glucose levels >6.6mmol/l were more common in those with TCDD exposed jobs (OR 3.6, 95%CI 1.0-12.9), as were serum free thyroxine 4<12.8pmol/l (OR 4.5, 95%CI 1.4-14.4), triglycerides >1.7mmol/l (OR 2.5, 95%CI 1.1-5.7) and high density lipoprotein cholesterol (HDL) <1mmol/l (OR 4.0, 95%CI 1.2-13.2). IgG was negatively associated with TCDD (linear regression p=0.05). The neurological examination revealed a higher frequency of abnormal reflexes in those with serum TCDD ≥10pg/g (OR 4.8, 95%CI 1.1-21.0).

CONCLUSIONS

In this occupationally exposed population, TCDD was associated with an increased risk of diabetes and a range of subclinical responses in multiple systems (peripheral nervous system, immune system, thyroid hormones and lipid metabolism), several decades after last exposure. These results need to be interpreted with caution due to the small study size and the cross-sectional nature of the study.

Association Between Dioxin and Metabolic Syndrome by Age and Sex in an Endemic Area of Exposure in Taiwan

BACKGROUND

Some of the effects of dioxins seem to be different between men and women, and exposures starting at an early age seem to have more prominent effects. Therefore, we conducted a study in Taiwan to evaluate the associations between exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and metabolic syndrome (MetS) starting at different ages in both sexes.

METHODS

We recruited participants from an area where residents were exposed to PCDD/Fs released from a factory and defined serum PCDD/Fs levels ≥20 pg WHO98-TEQDF/g lipid as high dioxin levels. MetS was defined as meeting three of the following criteria: fasting glucose ≥100 mg/dl or under treatment for diabetes, waist circumference ≥90 cm in men or ≥80 cm in women, triglycerides ≥150 mg/dl or under treatment for elevated triglycerides, high-density lipoprotein <40 mg/dl in men or <50 mg/dl in women, and blood pressures ≥130/85 mmHg or under treatment for hypertension.

RESULTS

Of the 2758 participants, 785 patients with MetS were identified, and we observed positive associations between a high dioxin level and MetS. After adjusting for sex, age, and age at starting exposure, we found that a high dioxin level was an independent predictor for MetS (adjusted odds ratio =1.38; 95% confidence interval = 1.11, 1.72). When we stratified the participants by gender, we found that a high dioxin level remained an independent predictor of MetS in men, but not in women, regardless of the age at starting exposure.

CONCLUSIONS

Exposure to PCDD/Fs was associated with MetS in men, independent of age and age at starting exposure.

Adipose Tissue as a Site of Toxin Accumulation

We examine the role of adipose tissue, typically considered an energy storage site, as a potential site of toxicant accumulation. Although the production of most persistent organic pollutants (POPs) was banned years ago, these toxicants persist in the environment due to their resistance to biodegradation and widespread distribution in various environmental forms (e.g., vapor, sediment, and water). As a result, human exposure to these toxicants is inevitable. Largely due to their lipophilicity, POPs bioaccumulate in adipose tissue, resulting in greater body burdens of these environmental toxicants with obesity. POPs of major concern include polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDDs/PCDFs), and polybrominated biphenyls and diphenyl ethers (PBBs/PBDEs), among other organic compounds. In this review, we (i) highlight the physical characteristics of toxicants that enable them to partition into and remain stored in adipose tissue, (ii) discuss the specific mechanisms of action by which these toxicants act to influence adipocyte function, and (iii) review associations between POP exposures and the development of obesity and diabetes. An area of controversy relates to the relative potential beneficial versus hazardous health effects of toxicant sequestration in adipose tissue. © 2017 American Physiological Society. Compr Physiol 7:1085-1135, 2017.

Is Parkinson's Disease with History of Agent Orange Exposure Different from Idiopathic Parkinson's Disease?

Background and Purpose

During Vietnam War, many Korean soldiers were dispatched to fight in the war where they were exposed to Agent Orange. Until now, there exist only limited evidence on existence of association between exposure to Agent Orange and Parkinson's disease (PD). To elucidate the effects of Agent Orange exposure on PD, we compared the clinical characteristics and radiolabeled 18F-FP-CIT PET uptake between patients with Agent Orange exposure and patients with Agent Orange no-exposure.

Methods

We retrospectively evaluated 143 patients exposed to Agent Orange and 500 patients with no exposure to Agent Orange from our movement clinics database. The differences between clinical characteristics and pattern of 18F-FP-CIT PET uptake were investigated.

Results

Among Unified Parkinson's Disease Rating Scale III motor subscales, tremor at rest, rigidity, finger taps, and rapid alternating movement was significantly higher in patients exposed to Agent Orange as compared to patients with no exposure to Agent Orange. The facial expression score was significantly lower in patients exposed to Agent Orange as compared to patients with no exposure to Agent Orange. Compared to patients not exposed to Agent Orange, all basal ganglia areas (contra- and ipsilateral caudate nucleus, anterior putamen, and posterior putamen) showed a lower18F-FP-CIT uptake and higher asymmetry index of anterior and posterior putamen was found in patients exposed to Agent Orange. The caudate/putamen ratio was significantly lower in patients exposed to Agent Orange as compared to patients with no exposure to Agent Orange.

Conclusions

This study showed a different clinical profile and FP-CIT PET findings between patients exposed to Agent Orange as compared to patients with no exposure to Agent Orange. This finding suggests the possibility of different pathophysiology of PD in patients exposed to Agent Orange from idiopathic PD.

Occupational chemical exposure and diabetes mellitus risk

Diabetes mellitus (DM) is a group of metabolic diseases that may originate from an interaction between genetic and lifestyle risk factors. However, the possible role of occupational chemical exposures in the disease development and progression remains unclear. Therefore, this review aimed to provide a comprehensive evaluation of the relationship between occupational exposure to specific chemical substances or industrial activities and DM morbidity and mortality outcomes. Although some positive findings may support the diabetogenic role of certain pesticides and dioxins in different workplaces, the variable conditions of exposure, the lack of quantitative environmental or biological monitoring data and the different outcomes evaluated do not allow defining a specific exposure-disease causality. Therefore, further epidemiological studies will be necessary to adequately assess modes of action for different substances, dose–response relationships as well as individual susceptibility factors potentially affecting the exposure-disease continuum. Overall, this appears important to adequately assess, communicate and manage risks in occupational chemical exposure settings with the aim to protect workers and build healthier job conditions for diabetic employees.

Association between Dioxin and Diabetes Mellitus in an Endemic Area of Exposure in Taiwan: A Population-Based Study

Dioxin has been recognized as an environmental endocrine disruptor, but epidemiology studies of its effects on type 2 diabetes mellitus (DM) found inconsistent results, especially in men. Therefore, we conducted a study in Taiwan to evaluate the association between exposure to dioxin and DM.We recruited participants in an area where the residents were exposed to dioxin released from a factory. Using 20 and 64 pg WHO98-TEQDF/g lipid as the cut-offs, we categorized participants into 3 groups according to the level of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the serum. We defined DM as a fasting plasma glucose level more than 126 mg/dl or an existing diagnosis.Of the 2898 participants, 425 patients of DM were identified, and we observed positive associations between dioxin and DM. After adjusting for age and body mass index (BMI), we found that a high serum dioxin level was an independent risk factor for DM (adjusted odds ratio [AOR] associated with 20-63 pg WHO98-TEQDF/g lipid = 2.1, 95% confidence interval [95% CI] 1.5-2.9; AOR for ≥64 pg WHO98-TEQDF/g lipid = 3.2, 95% CI 2.1-4.8). The findings are compatible with those in previous studies of PCDD/Fs. When we stratified the participants by sex, the serum dioxin level remained an independent risk factor for DM in both men and women.Exposure to dioxin is a risk factor for DM, independent of age and BMI in both men and women. Therefore, screening and intervention programs should be considered in endemic areas of exposure to dioxin.

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.

Dose-response relationship between serum 2,3,7,8-tetrachlorodibenzo-p-dioxin and diabetes mellitus: a meta-analysis

We systematically evaluated studies published through May 2014 in which investigators assessed the dose-response relationship between serum levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the occurrence of diabetes mellitus (DM), and we investigated the extent and sources of interstudy heterogeneity. The dose-response relationship between serum TCDD and DM across studies was examined using 2 dependent variables: an exposure level-specific proportion of persons with DM and a corresponding natural log-transformed ratio measure of the association between TCDD and DM. Regression slopes for each dependent variable were obtained for each study and included in a random-effects meta-analysis. Sensitivity analyses were used to assess the influence of inclusion and exclusion decisions, and sources of heterogeneity were explored using meta-regression models and a series of subanalyses. None of the summary estimates in the main models or in the sensitivity analyses indicated a statistically significant association. We found a pronounced dichotomy: a positive dose-response in cross-sectional studies of populations with low-level TCDD exposures (serum concentrations <10 pg/g lipid) and heterogeneous, but on balance null, results for prospective studies of persons with high prediagnosis TCDD body burdens. Considering the discrepancy of results for low current versus high past TCDD levels, the available data do not indicate that increasing TCDD exposure is associated with an increased risk of DM.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

Agent Orange exposure and disease prevalence in Korean Vietnam veterans: the Korean veterans health study

Between 1961 and 1971, military herbicides were used by the United States and allied forces for military purposes. Agent Orange, the most-used herbicide, was a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid, and contained an impurity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Many Korean Vietnam veterans were exposed to Agent Orange during the Vietnam War. The aim of this study was to evaluate the association between Agent Orange exposure and the prevalence of diseases of the endocrine, nervous, circulatory, respiratory, and digestive systems. The Agent Orange exposure was assessed by a geographic information system-based model. A total of 111,726 Korean Vietnam veterans were analyzed for prevalence using the Korea National Health Insurance claims data from January 2000 to September 2005. After adjusting for covariates, the high exposure group had modestly elevated odds ratios (ORs) for endocrine diseases combined and neurologic diseases combined. The adjusted ORs were significantly higher in the high exposure group than in the low exposure group for hypothyroidism (OR=1.13), autoimmune thyroiditis (OR=1.93), diabetes mellitus (OR=1.04), other endocrine gland disorders including pituitary gland disorders (OR=1.43), amyloidosis (OR=3.02), systemic atrophies affecting the nervous system including spinal muscular atrophy (OR=1.27), Alzheimer disease (OR=1.64), peripheral polyneuropathies (OR=1.09), angina pectoris (OR=1.04), stroke (OR=1.09), chronic obstructive pulmonary diseases (COPD) including chronic bronchitis (OR=1.05) and bronchiectasis (OR=1.16), asthma (OR=1.04), peptic ulcer (OR=1.03), and liver cirrhosis (OR=1.08). In conclusion, Agent Orange exposure increased the prevalence of endocrine disorders, especially in the thyroid and pituitary gland; various neurologic diseases; COPD; and liver cirrhosis. Overall, this study suggests that Agent Orange/2,4-D/TCDD exposure several decades earlier may increase morbidity from various diseases, some of which have rarely been explored in previous epidemiologic studies.

Toxicant-associated steatohepatitis

Hepatotoxicity is the most common organ injury due to occupational and environmental exposures to industrial chemicals. A wide range of liver pathologies ranging from necrosis to cancer have been observed following chemical exposures both in humans and in animal models. Toxicant-associated fatty liver disease (TAFLD) is a recently named form of liver injury pathologically similar to alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). Toxicant-associated steatohepatitis (TASH) is a more severe form of TAFLD characterized by hepatic steatosis, inflammatory infiltrate, and in some cases, fibrosis. While subjects with TASH have exposures to industrial chemicals, such as vinyl chloride, they do not have traditional risk factors for fatty liver such as significant alcohol consumption or obesity. Conventional biomarkers of hepatotoxicity including serum alanine aminotransferase activity may be normal in TASH, making screening problematic. This article examines selected chemical exposures associated with TAFLD in human subjects or animal models and concisely reviews the closely related NAFLD and ALD.

Metabolic impacts of high dietary exposure to persistent organic pollutants in mice

Persistent organic pollutants (POPs) have been linked to metabolic diseases. Yet, the effects of high exposure to dietary POPs remain unclear. We therefore investigated whether elevated exposure to POPs provided by whale meat supplementation could contribute to insulin resistance. C57BL/6J mice were fed control (C) or very high-fat diet (VHF) containing low or high levels of POPs (VHF(+POPs)) for eight weeks. To elevate the dietary concentrations of POPs, casein was replaced by whale meat containing high levels of pollutants. Feeding VHF(+POPs) induced high POP accumulation in the adipose tissue of mice. However, compared with VHF-fed mice, animals fed VHF(+POPs) had improved insulin sensitivity and glucose tolerance, and reduced body weight. Levels of ectopic fat in skeletal muscles and liver were reduced in mice fed VHF(+POPs). These mice also gained less adipose tissue and had a tendency to reduced energy intake. In pair-feeding experiments, improved insulin action and reduced body weight gain were still observed in VHF(+POPs) compared to VHF pair-fed mice. We concluded that mice fed VHF contaminated with POPs derived from whale meat remain sensitive to insulin and glucose tolerant despite significant body burden of POPs. This indicates complex interactions between organic pollutants and nutrition in the development of metabolic disorders.

Re-analysis of Ranch Hand study supports reverse causation hypothesis between dioxin and diabetes

A dose-response relationship between serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) and adult diabetes risk has been reported among U.S. Vietnam veterans in the Ranch Hand (RH) cohort. We examine the hypothesis that diabetes progression leads to higher serum dioxin (reverse causation) rather than higher serum dioxin leading to diabetes (causation) across the longitudinal medical monitoring data on these airmen. Lipid-adjusted serum dioxin levels and clinical parameters relating to diabetes progression were examined. Potential confounding due to age, race, diabetes family history, serum total lipid, and body mass index (BMI) was accounted for. The similar incidence of diabetes in RH and Comparison veterans, along with generally similar incidence trends with dioxin decile and lipid decile despite the large differential in serum dioxin, is evidence consistent with reverse causation. Of 135 RH diabetics with at least two dioxin measurements, 32.6% had a temporary serum dioxin increase more than a decade after Vietnam tour and another 22.2% had an interval of unusually slow half-life (>15.5 years); these diabetes-related changes shifted more diabetics into the higher dioxin deciles. Further, the increased diabetes odds ratio among the generally younger RH veterans in the highest dioxin decile is associated with a higher incidence of adult obesity in this RH subgroup, both at tour of duty and decades later. Change in serum dioxin levels is likely due to diabetes progression or poor control and is not independently related to serum dioxin concentrations. In summary, the data from the Ranch Hand studies does not indicate that dioxin increases adult diabetes risk.

Thyroid follicular lesions induced by oral treatment for 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin and dioxin-like compounds in female Harlan Sprague-Dawley rats

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and structurally-similar dioxin-like compounds affect thyroid function and morphology and thyroid hormone metabolism in animals and humans. The National Toxicology Program conducted eight 2-year gavage studies in female Harlan Sprague-Dawley rats to determine the relative potency of chronic toxicity and carcinogenicity of TCDD, 3,3',4,4',5-pentachlorobiphenyl (PCB126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 2,3',4,4',5-pentachlorobiphenyl (PCB118), 2,2',4,4',5,5'-hexachloro-biphenyl (PCB153), a tertiary mixture of TCDD/PCB126/PeCDF, and two binary mixtures (PCB126/PCB153 and PCB126/PCB118). Administration of these compounds was associated with increased incidences of thyroid follicular cell hypertrophy, variably observed in the 14-, 31-, and 53-week interim and 2-year sacrifice groups. In all studies, the incidences of follicular cell adenoma and carcinoma were not increased. Decreased levels of serum thyroxine were primarily noted in the 14-or-later -week interim groups of all chemicals. Serum triiodothyronine (T3) levels were increased in the TCDD, PCB126, PeCDF, TCDD/PCB126/PeCDF, and PCB126/PCB153 studies, while decreased levels were noted in the PCB153 and PCB126/PCB118 studies. TCDD, PCB126, PCB126/PCB153, and PCB126/PCB118 increased levels of serum thyroid-stimulating hormone almost in a dose-dependent manner in the 14-week groups. These data suggest that although dioxin-like compounds alter thyroid hormones and increase follicular cell hyperplasia, there is not an increase in thyroid adenoma or carcinoma in female Sprague-Dawley rats.

Pesticide use and thyroid disease among women in the Agricultural Health Study

Thyroid disease is common, and evidence of an association between organochlorine exposure and thyroid disease is increasing. The authors examined the cross-sectional association between ever use of organochlorines and risk of hypothyroidism and hyperthyroidism among female spouses (n = 16,529) in Iowa and North Carolina enrolled in the Agricultural Health Study in 1993-1997. They also assessed risk of thyroid disease in relation to ever use of herbicides, insecticides, fungicides, and fumigants. Prevalence of self-reported clinically diagnosed thyroid disease was 12.5%, and prevalence of hypothyroidism and hyperthyroidism was 6.9% and 2.1%, respectively. There was an increased odds of hypothyroidism with ever use of organochlorine insecticides (adjusted odds ratio (OR(adj)) = 1.2 (95% confidence interval (CI): 1.0, 1.6) and fungicides (OR(adj) = 1.4 (95% CI: 1.1, 1.8) but no association with ever use of herbicides, fumigants, organophosphates, pyrethroids, or carbamates. Specifically, ever use of the organochlorine chlordane (OR(adj) = 1.3 (95% CI: 0.99, 1.7), the fungicides benomyl (OR(adj) = 3.1 (95% CI: 1.9, 5.1) and maneb/mancozeb (OR(adj) = 2.2 (95% CI: 1.5, 3.3), and the herbicide paraquat (OR(adj) = 1.8 (95% CI: 1.1, 2.8) was significantly associated with hypothyroidism. Maneb/mancozeb was the only pesticide associated with both hyperthyroidism (OR(adj) = 2.3 (95% CI: 1.2, 4.4) and hypothyroidism. These data support a role of organochlorines, in addition to fungicides, in the etiology of thyroid disease among female spouses enrolled in the Agricultural Health Study.

Key developments in endocrine disrupter research and human health

Environmental etiologies involving exposures to chemicals that mimic endogenous hormones are proposed for a number of adverse human health effects, including infertility, abnormal prenatal and childhood development, and reproductive cancers (National Research Council, 1999; World Health Organization, 2002). Endocrine disrupters represent a significant area of environmental research with important implications for human health. This article provides an overview of some of the key developments in this field that may enhance our ability to assess the human health risks posed by exposure to endocrine disrupters. Advances in methodologies of hazard identification (toxicogenomics, transcriptomics, proteomics, metabolomics, bioinformatics) are discussed, as well as epigenetics and emerging biological endpoints.

Risk of leukaemia among pesticide manufacturing workers: a review and meta-analysis of cohort studies

PURPOSE

The purpose of this paper is to review available cohort studies and to estimate quantitatively the association between occupational exposure in plants manufacturing pesticides and leukaemia.

METHODS

Following a systematic literature search, relative risks were extracted from 14 studies published between 1984 and 2004. Fixed effect analyses were carried out as heterogeneity between studies was not detected. Meta-analyses were performed on the whole set of data and separate analyses were conducted for specific chemical classes of pesticides as well as type of leukaemia.

RESULTS

The meta-rate ratio estimate for all studies was 1.43 (95% confidence interval [CI] 1.05-1.94). After stratification by chemical class, consistent increases in the risk of leukaemia were found in all groups but statistical significance was found only for phenoxy herbicides unlikely to have been contaminated with dioxins and furans. This last finding appears equivocal in view of the existing literature. The separate analysis conducted on leukaemias from the myeloid lineage showed the highest relative risk (6.99; 95% CI 1.96-24.90). There was no obvious indication of publication bias.

CONCLUSION

The overall meta-analysis among pesticide manufacturing workers provides quantitative evidence to consider occupational exposure to pesticides as a possible risk factor for leukaemia but available data are too scarce for causality ascertainment. Epidemiological evidence did not allow identifying a specific pesticide or chemical class that would be responsible for the increased risk. Exposure to pesticides may be a significant risk factor for specifically developing myeloid leukaemia and there is a need for additional large well-conducted studies with clear definition of exposure and of leukaemia type(s).

A critical comparison of murine pathology and epidemiological data of TCDD, PCB126, and PeCDF

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, or dioxin) and dioxin-like compounds (DLCs) induce numerous toxicities, including developmental, endocrine, immunological, and multi-organ carcinogenic, in animals and/or humans. Multiple studies completed by the National Toxicology Program (NTP) focused on the effects caused in Harlan Sprague-Dawley rats by specific DLCs, among them the prototypical dioxin, TCDD. Because humans are exposed daily to a combination of DLCs, primarily via ingestion of food, the Toxic Equivalency Factor (TEF) was developed in order to evaluate health hazards caused by these mixtures. Herein we review the pathological effects reported in humans exposed to TCDD; 3,3',4,4',5-pentachlorobiphenyl (PCB 126); and 2,3,4,7,8,-pentachlorodibenzofuran (PeCDF) and compare them to similar changes seen in NTP murine studies performed with the same compounds. While there were differences in specific pathologies observed, clear consistency in the target organs affected (liver, oral cavity, cardiovascular system, immune system, thyroid, pancreas, and lung) could be seen in both human studies and rodent toxicity and carcinogenicity investigations.

Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds

Dioxin and dioxin-related compounds have been associated with high incidences of pulmonary dysfunctions and/or cancers in humans. To evaluate the relative potencies of effects of these compounds, the National Toxicology Program completed a series of two-year bioassays which were conducted using female Harlan Sprague-Dawley rats. The rats were treated orally for up to 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3,3',4,4',5-pentachlorobiphenyl (PCB126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and a ternary mixture of TCDD, PCB126 and PeCDF. In addition to treatment-related effects reported in other organs, a variety of pulmonary lesions were observed that were related to exposure. Pulmonary CYP1A1-associated 7-ethoxyresorufin-O-deethylase (EROD) activity was increased in all dosed groups. The most common non-neoplastic lesions, which occurred in all studies, were bronchiolar metaplasia and squamous metaplasia of the alveolar epithelium. Cystic keratinizing epithelioma was the most commonly observed neoplasm which occurred in all studies. A low incidence of squamous cell carcinoma was associated only with PCB126 treatment. Potential mechanisms leading to altered differentiation and/or proliferation of bronchiolar and alveolar epithelia may be through CYP1A1 induction or disruption of retinoid metabolism.

Health status of Army Chemical Corps Vietnam veterans who sprayed defoliant in Vietnam

BACKGROUND

U.S. Army Chemical Corps veterans handled and sprayed herbicides in Vietnam resulting in exposure to Agent Orange and its contaminant 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin). This study examined the long-term health effects associated with herbicide exposure among these Vietnam veterans.

METHODS

A health survey of these 1,499 Vietnam veterans and a group of 1,428 non-Vietnam veterans assigned to chemical operations jobs was conducted using a computer-assisted telephone interview (CATI) system. Exposure to herbicides was assessed by analyzing serum specimens from a sample of 897 veterans for dioxin. Logistic regression analyses were used to estimate the risk of selected medical outcomes associated with herbicide exposure.

RESULTS

Odds ratios for diabetes, heart disease, hypertension, and chronic respiratory disease were elevated, but not significantly (P>0.05) for those who served in Vietnam. However, they were significantly elevated among those Vietnam veterans who sprayed herbicides: diabetes, odds ratio (OR)=1.50 (95% confidence interval [95%CI]=1.15-1.95); heart disease, OR=1.52 (1.18-1.94); hypertension, OR=1.32 (1.08-1.61); and chronic respiratory condition, OR=1.62 (1.28-2.05). Hepatitis was associated with Vietnam service, but not with herbicide application.

CONCLUSIONS

Vietnam veterans who were occupationally exposed to herbicide experienced a higher risk of several chronic medical conditions relative to other non-Vietnam veterans. A potential selection bias is of concern. However, there were relatively high participation rates in both the Vietnam and non-Vietnam veteran groups, and the prevalence rates of some of these medical conditions among non-Vietnam veterans were comparable to general populations. Therefore, self-selection factors are considered unlikely to have biased the study results.

A strong dose-response relation between serum concentrations of persistent organic pollutants and diabetes: results from the National Health and Examination Survey 1999-2002

OBJECTIVE

Low-level exposure to some persistent organic pollutants (POPs) has recently become a focus because of their possible link with the risk of diabetes.

RESEARCH DESIGN AND METHODS

Cross-sectional associations of the serum concentrations of POPs with diabetes prevalence were investigated in 2,016 adult participants in the National Health and Nutrition Examination Survey 1999-2002. Six POPs (2,2',4,4',5,5'-hexachlorobiphenyl, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, oxychlordane, p,p'-dichlorodiphenyltrichloroethane, and trans-nonachlor) were selected, because they were detectable in >or=80% of participants.

RESULTS

Compared with subjects with serum concentrations below the limit of detection, after adjustment for age, sex, race and ethnicity, poverty income ratio, BMI, and waist circumference, diabetes prevalence was strongly positively associated with lipid-adjusted serum concentrations of all six POPs. When the participants were classified according to the sum of category numbers of the six POPs, adjusted odds ratios were 1.0, 14.0, 14.7, 38.3, and 37.7 (P for trend < 0.001). The association was consistent in stratified analyses and stronger in younger participants, Mexican Americans, and obese individuals.

CONCLUSIONS

There were striking dose-response relations between serum concentrations of six selected POPs and the prevalence of diabetes. The strong graded association could offer a compelling challenge to future epidemiologic and toxicological research.

Chronic exposure to dioxin-like compounds and thyroid function among New York anglers

Experimental studies suggest that dioxin-like compounds influence thyroid function, although human studies have presented equivocal results. Great Lakes sportfish consumers represent a population with greater potential for exposure to dioxin-like compounds than non-consumers. Thirty-eight licensed anglers participating in a dioxin exposure study, consumers and non-consumers, conducted as part of the New York Angler Cohort Study, donated blood and completed questionnaires regarding demographic, clinical, and sportfish consumption data. Sera were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), coplanar biphenyls (PCB), and PCB IUPAC #153, in addition to thyroid stimulating hormone (TSH), total and free thyroxine (T(4) and fT(4)), total triiodothyronine (T(3)), and lipids. An inverse linear association between serum fT(4) and the sum of dioxin-like congener concentrations (∑DIOXs) in serum (B=-0.3, 95% CI=-0.5, -0.1) was identified adjusting for PCB #153 and serum lipids (R(2)=0.3, p=0.02, n=37). The results of this study are preliminary but suggest an inverse association between dioxin-like compounds and fT(4).

Review and Meta-analysis of Risk Estimates for Prostate Cancer in Pesticide Manufacturing Workers

PURPOSE

The purpose of the present paper is to review cohort studies that examined the occurrence of prostate cancer in pesticide manufacturing workers in order to undertake a qualitative and quantitative evaluation of the risk as well as to assess the level of epidemiological evidence for each class of chemical compounds.

METHODS

Following a systematic literature search, relative risk (RR) estimates for prostate cancer were extracted from 18 studies published between 1984 and 2004. All studies were summarised and evaluated for homogeneity and publication bias. As no significant heterogeneity was detected, combined RR estimators were calculated using a fixed effect model. Meta-analyses were performed both on the whole set of data and for each chemical class separately.

RESULTS

The meta-rate ratio estimate for all studies was 1.28 [95% confidence interval (CI) 1.05-1.58]. After stratification by specific chemical class, consistent increases in the risk of prostate cancer were found in all groups but statistical significance was found only for accidental or non-accidental exposure to phenoxy herbicides contaminated with dioxins and furans. There was no obvious indication of publication bias.

CONCLUSION

The overall meta-analysis provides additional quantitative evidence consistent with prior reviews focusing on other groups exposed to pesticides (farmers, pesticide applicators). The results again point to occupational exposure to pesticides as a possible risk factor for prostate cancer but the question of causality remains unanswered. Epidemiological evidence did not allow identifying a specific pesticide or chemical class that would be responsible for the increased risk but the strongest evidence comes from workers exposed to phenoxy herbicides possibly in relation with dioxin and/or furan contamination.

Dioxin effects on neonatal and infant thyroid function: routes of perinatal exposure, mechanisms of action and evidence from epidemiology studies

OBJECTIVES

Animal experiments suggest that thyroid function alterations in newborns and infants may represent one of the most sensitive markers of toxicity from 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Dioxin can be transferred from the mother to the offspring either in utero or through lactation. It has been suggested that thyroid-hormone alterations produced by dioxin in utero or shortly after birth may underlie long-term effects, such as cognitive-ability and neurodevelopment impairment. In the present review article, we appraise available evidence on the effects of perinatal exposure to dioxin on fetal and infant thyroid function.

METHODS

We summarized the routes of perinatal dioxin exposure and research results on possible mechanisms of dioxin toxic effects on thyroid function. We performed a systematic review of epidemiology studies conducted on mother-child pairs exposed to background environmental levels to investigate dioxin effects on neonatal and infant thyroid function.

RESULTS

Toxicological and mechanistic data indicate that dioxin may impair thyroid function in exposed newborns and infants. Investigations on background-exposed children have not consistently demonstrated an association between perinatal TCDD exposure and thyroid function, although some of the studies suggest that sub-clinical hypothyroidism may be induced by perinatal dioxin exposure within 3 months from birth. Between studies inconsistencies may be related to lab method differences, mixed exposures, and small sample size of the populations evaluated.

CONCLUSION

Epidemiology studies have as yet failed to demonstrate an association between perinatal TCDD exposure and thyroid function alterations in human subjects, although suggestive evidence from animal and in-vitro experimental data is available.

Effect of chlorophyllin-chitosan on excretion of dioxins in a healthy man

We investigated the usefulness of chitosan and chlorophyllin-chitosan (chl-chitosan) administration for reduction of the body burden of environmental dioxins, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/ Fs) and coplanar polychlorinated biphenyls (Co-PCBs), by examining the excretion levels in the feces and sebum of a healthy man. The volunteer ate the same three meals every day during the 40-d experiment, which was composed of five phases (I-V) of 8 d each. In phase I (days 1-8), the volunteer was given only the basal diet. In phases II-V, 0.2 g of chitosan, 0.6 g of chitosan, 0.2 g of chl-chitosan, and 0.6 g of chl-chitosan, respectively, were administered immediately after each meal. We measured daily the amount of dioxins occurring in the feces and sebum during the last 5 d of each phase. The total toxicity equivalency (TEQ) of the dioxin in phases I-V were 27, 26, 38, 36, and 67 pg/d in the feces and 20, 19, 16, 16, and 14 pg/d in the sebum, compared with 74 pg/d in the food. The excretion of dioxins in the feces was significantly increased in phases III, IV, and V, being 140% (p < 0.05), 135% (p < 0.05), and 249% (p < 0.01) of the control level (phase I). Although the dioxin in the sebum was slightly decreased in phase V as compared with the control level, the total amount of excreted dioxin in feces and sebum was increased significantly in phase V, being 174% of the control level, which is almost the same level as that in the food. This indicates that chl-chitosan can prevent accumulation of dioxin, at least at the intake level of normal foods.

Soft-tissue sarcoma and dioxin: A case-control study

Soft-tissue sarcoma has been proposed to be a candidate for a dioxin-induced cancer. However, previous epidemiologic studies have suffered from poor exposure data and mixed exposures. We studied the association between sarcoma risk and individually estimated dioxin exposure in a general population exposed to relatively low levels of dioxin via food. A multicenter prospective case-control study was conducted in 4 university hospitals and 12 other hospitals in southern Finland. Participants included 110 patients with soft-tissue sarcoma (cases) and 227 area- and age-matched controls. Controls were patients operated for appendicitis. Individual dioxin concentrations were analyzed from subcutaneous fat samples by gas chromatography-mass spectrometry. The average (range) dioxin concentration was 33.4 (4.4-145.5) ng/kg (toxic equivalencies in fat according to WHO). No increased risk associated with increased dioxin concentration was observed. In contrast, the highest risk of sarcoma was found at low levels of dioxin. Odds ratios for different quintiles as compared with the lowest quintile of dioxins (median, 11.5 ng/kg) varied from 0.43 (95% CI = 0.18-1.05) to 0.65 (95% CI = 0.22-1.95). The result was little affected by studied confounders and the findings were similar for different sarcoma subtypes, age groups and study areas. The results imply that dioxin does not increase the risk of soft-tissue sarcoma at the present population levels.

Possible effects of polychlorinated biphenyls and organochlorinated pesticides on the thyroid after long-term exposure to heavy environmental pollution

The purpose of this work was to study the effects of high environmental exposure to polychlorinated biphenyls (PCBs) and other organochlorines on the thyroid. Thyroid volume, hypoechogenicity and nodules (by ultrasound), presence of antithyroid peroxidase (anti-TPO) antibodies, and abnormal thyroid-stimulating hormone (TSH) levels in serum (by radioimmunoassay) were examined in 101 adults from the PCB-polluted area in 360 controls. Serum levels of PCBs, hexachlorobenzene, gamma-hexachlorocyclohexane (HCH), p,p'-DDT(1,1,1-trichloro-2,2'-bis(p-chlorophenyl)ethane), and p,p'-DDE(1,1-dichloro-2,2'-bis(p-chlorophenyl)ethene) were measured by high-resolution gas chromatography. Very high levels of PCBs were found in the polluted area (7300 +/- 871 ng/g lipids) compared with controls (2045 +/- 147 ng/g). Positive correlations (P < 0.001) were found between the levels of all organochlorines and their total except for hexachlorocyclohexane (HCH). In the polluted area, the highest thyroid volumes (18.7 +/- 2.32 mL; mean +/- SE) were clustered among 23 subjects (17 males and six females) with PCB levels above 10,000 ng/g (range 10,000-58,667 ng/g). In the remaining 438 subjects the thyroid volume was 14.2 +/- 0.29 mL. These data suggest that there might be a threshold serum PCB level of approximately 10,000 ng/g that may influence the thyroid volume. A two-way ANOVA showed that all thyroid volumes in the polluted area were significantly higher (P < 0.001) than in the control area. In males from the polluted area, the frequencies of thyroid hypoechogenicity, thyroid nodules, positive anti-TPO, and abnormal TSH level were higher than in males from the control area, whereas such differences were not observed in females. Increased thyroid volume and indicators of potential thyroid dysfunction were associated with long-term environmental exposure to PCBs. These effects on the thyroid were confined to subjects with PCB levels above 10,000 ng/g of lipid (thyroid volume) and to males from the polluted area (thyroid hypoechogenicity, thyroid nodules, positive anti-TPO, and abnormal TSH).

Serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) levels and thyroid function in Air Force veterans of the Vietnam War

PURPOSE

We assessed potential health effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) concentration in serum on thyroid function in US Air Force veterans involved in Operation Ranch Hand, the unit responsible for the aerial spraying of herbicides, including TCDD-contaminated Agent Orange, during the Vietnam War from 1962 to 1971. Other Air Force veterans who were not involved with spraying herbicides were included as Comparisons.

METHODS

We analyzed thyroxine (total T4), thyroid stimulating hormone (TSH), triiodothyronin percent uptake (T3% uptake), the free thyroxine index (FTI), and thyroid diseases against serum TCDD levels. Data was available for 1,009 Ranch Hand and 1,429 Comparison veterans compliant to any of five examinations in 1982, 1985, 1987, 1992, and 1997. Each veteran was assigned to one of four exposure categories based on serum TCDD levels, named Comparison, Ranch Hand Background, Ranch Hand Low Elevated, and Ranch Hand High Elevated.

RESULTS

Cross-sectional analyses found statistically significantly increased TSH means at the 1985 and 1987 examinations in the High category and a significant increasing trend across the three Ranch Hand TCDD categories in 1982, 1985, 1987 and 1992. A repeated-measures analysis found significantly increased TSH means in the High TCDD category. We found no significant relation between the occurrence of thyroid disease and TCDD category.

CONCLUSIONS

These findings suggest that TCDD affects thyroid hormone metabolism and function in Ranch Hand veterans. Further follow-up will be necessary to understand the relation, if any, between thyroid disease and TCDD levels.

Basis for a proposed reference dose (RfD) for dioxin of 1-10 pg/kg-day: a weight of evidence evaluation of the human and animal studies

The dioxins have been perhaps the most studied of all chemicals to which humans are routinely exposed. It has been reported that more than 5,000 scientific papers have been published that have evaluated the toxicology of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Although the cancer hazard posed by this chemical has probably received the bulk of attention over the past 20 years, the U.S. Environmental Protection Agency (EPA) and the recent U.S. EPA Science Advisory Board (SAB) that reviewed the "Reassessment" have suggested that the noncancer hazard may well be more important than the cancer hazard at current background doses to the general public. The World Health Organization (WHO) and U.K. Food Standards Agency (FAO) committee (JECFA) on dioxins has reached similar conclusions. This article reviews the published studies involving laboratory animals and humans that address the noncancer effects. Based on our review, developmental toxicity is the most sensitive effect of TCDD consistently seen in mice and rats. Specifically, of the various studies, a no-observed-adverse-effects level (NOAEL) of 13 ng/kg (maternal body burden) was identified as the most pertinent for deriving a reference dose (RfD) for humans. Although more than a dozen different adverse effects have been reported in various studies of humans over the past 25 years, the most consistent clinically important adverse effect of human exposure appears to be chloracne. Following a review of all published studies, we concluded that the best estimate of a LOAEL for production of chloracne is approximately 160 ng/kg (body burden). Based on our analysis, an RfD of between 1 and 10 pg/kg-d (TCDD TEQ) is consistent with the objectives of this risk criterion. Maintaining a lifetime average daily dose below this concentration, based on what is known today, should prevent noncancer effects in virtually all persons. This value is consistent with the JECFA recommendation of 70 pg/kg-mo.

Immunologic effects of dioxin: new results from Seveso and comparison with other studies

Animal studies indicate that the immune system is one of the most sensitive targets of the toxic effects of 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD). TCDD inhibits immunoglobulin secretion and decreases resistance to bacterial, viral, and parasitic infections in exposed animals. Nearly 20 years after the Seveso, Italy, accident, we measured immunoglobulin and complement plasma levels in a random sample of the population in the most highly exposed zones (n = 62) and in the surrounding noncontaminated area (n = 58). Plasma IgG levels decreased with increasing TCDD plasma concentration (r = -0.35, p = 0.0002). Median IgG concentration decreased from 1,526 mg/dL in the group with the lowest (< 3.5 ppt) TCDD levels to 1,163 mg/dL in the group with the highest (20.1-89.9 ppt) TCDD levels (p = 0.002). The association was significant (p = 0.0004) after adjusting for age, sex, smoking, and consumption of domestic livestock and poultry in multiple regression analysis and persisted after exclusion of subjects with inflammatory diseases and those using antibiotics or nonsteroidal anti-inflammatory drugs. IgM, IgA, C3, and C4 plasma concentrations did not exhibit any consistent association with TCDD levels. We performed a systematic review of all the articles published between 1966 and 2001 on human subjects exposed to TCDD reporting information on circulating levels of immunoglobulins and/or complement components. The literature indicates that the evidence for effects of TCDD on humoral immunity is sparse. Methodologic issues, results, and possible sources of variation between studies are discussed. The possible long-term immunologic effects of TCDD exhibited by the participants of the present study, coupled with the increased incidence of lymphatic tumors in the area of the accident, warrant further investigation.

Linking dioxins to diabetes: epidemiology and biologic plausibility

Recent epidemiologic studies suggest a possible association between dioxin-like compounds (DLCs) and diabetes in human populations, although experimental links between DLCs and diabetes are lacking. The public health significance of such an association is that all populations are exposed to small but measurable levels of DLCs, chronic low-dose exposure to which may hasten the onset of adult-onset diabetes in susceptible individuals. In this article, we review the epidemiologic studies and propose biologically plausible connections between dioxins and diabetes. Specifically, we suggest that aryl hydrocarbon (Ah) receptor functions may antagonize peroxisome proliferator-activated receptor (PPAR) functions, and hence that the Ah receptor may promote diabetogenesis through a mechanism of PPAR antagonism.

Environmental contaminants as etiologic factors for diabetes

For both type 1 and type 2 diabetes mellitus, the rates have been increasing in the United States and elsewhere; rates vary widely by country, and genetic factors account for less than half of new cases. These observations suggest environmental factors cause both type 1 and type 2 diabetes. Occupational exposures have been associated with increased risk of diabetes. In addition, recent data suggest that toxic substances in the environment, other than infectious agents or exposures that stimulate an immune response, are associated with the occurrence of these diseases. We reviewed the epidemiologic data that addressed whether environmental contaminants might cause type 1 or type 2 diabetes. For type 1 diabetes, higher intake of nitrates, nitrites, and N-nitroso compounds, as well as higher serum levels of polychlorinated biphenyls have been associated with increased risk. Overall, however, the data were limited or inconsistent. With respect to type 2 diabetes, data on arsenic and 2,3,7,8-tetrachlorodibenzo-p-dioxin relative to risk were suggestive of a direct association but were inconclusive. The occupational data suggested that more data on exposure to N-nitroso compounds, arsenic, dioxins, talc, and straight oil machining fluids in relation to diabetes would be useful. Although environmental factors other than contaminants may account for the majority of type 1 and type 2 diabetes, the etiologic role of several contaminants and occupational exposures deserves further study.

Dioxin and diabetes mellitus: an analysis of the combined NIOSH and Ranch Hand data

OBJECTIVES

To reanalyze in a similar manner the two principal studies of TCDD (tetrachlorodibenzo-p-dioxin) and diabetes in an attempt to reconcile disparate results.

METHODS

Data from 990 United States Air Force veterans (Ranch Hand) and 1275 referents were reanalyzed, and a NIOSH population of 267 chemical workers and 227 referents. The Ranch Hand veterans had lower concentrations of lipid adjusted serum TCDD (median 12 parts per trillion (ppt)) than the NIOSH workers (median 75 ppt) when examined in the late 1980s. An analysis was conducted of the combined data sets, adopting a uniform approach to outcome definition, data analysis, and covariate control.

RESULTS

The combined exposed groups did not differ markedly from the combined non-exposed groups for prevalence of diabetes (odds ratio (OR) 1.17, 95% confidence interval (95% CI) 0.92 to 1.48), with no evidence of heterogeneity of exposure effect between studies. Also virtually no difference was found between combined exposed and non-exposed groups in mean fasting serum glucose (difference in log serum glucose 0.002, 95% CI -0.006 to 0.010), and there was little evidence in either study of a dose-response trend for fasting serum glucose. An increasing trend was found (p=0.0001) in prevalence of diabetes with increased TCDD (at the time of examination or at time of last exposure) among the Ranch Hand population, with excess risk largely confined to the highest 8% of the exposed group (>78 ppt serum TCDD), which had an OR of 3.21 (95% CI 1.81 to 5.72) versus those with <10 ppt TCDD. However, no such positive dose-response was found in the NIOSH population.

CONCLUSIONS

There was little overall evidence that the exposed workers were at higher risk than the non-exposed workers of diabetes or abnormal fasting glucose. However, the Ranch Hand subjects showed a positive dose-response for diabetes, whereas the more highly exposed NIOSH subjects did not. The reason for the difference in diabetes dose-response trends between the two studies is unknown.

Severe 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) intoxication: clinical and laboratory effects

A variety of health effects have been attributed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but little information is available on the course of a verified high-level TCDD intoxication. In this paper we describe two cases of heavy intoxication with TCDD and present a 2-year follow-up including clinical, biochemical, hematologic, endocrine, and immunologic parameters monitored in two women, 30 and 27 years of age, who suffered from chloracne due to TCDD intoxication of unknown origin. Patient 1, who had the highest TCDD level ever recorded in an individual (144,000 pg/g blood fat), developed severe generalized chloracne, whereas in the second patient, despite heavy intoxication (26,000 pg/g blood fat), only mild facial acne lesions occurred. Both patients initially experienced nonspecific gastrointestinal symptoms. In Patient 1 we observed a moderate elevation of blood lipids, leukocytosis, anemia, and secondary amenorrhoea. The laboratory parameters in Patient 2 were all normal. Despite the high TCDD levels, apart from chloracne, only few clinical and biochemical health effects were observed within the first 2 years after TCDD intoxication.

Serum dioxin and hepatic abnormalities in veterans of Operation Ranch Hand

PURPOSE

We studied hepatic abnormalities and indices of hepatic function in relation to exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) in veterans of Operation Ranch Hand, the Air Force unit responsible for the aerial spraying of herbicides in Vietnam from 1962 to 1971.

METHODS

The prevalence of ever having liver disease through March 1993, and level of alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase (GGT), lactic dehydrogenase (LDH), alkaline phosphatase, and total bilirubin were examined according to serum dioxin levels.

RESULTS

We found an increased risk of "other liver disorders" among veterans with the highest dioxin levels [adjusted odds ratio (OR) = 1.6, 95% confidence interval (CI) 1.2 to 2.1], due primarily to increased transaminases or LDH (adjusted OR = 2.7, 95% CI 1.4 to 5.1) and to other nonspecific liver abnormalities (adjusted OR = 1.4, 95% CI 1.0 to 2.0).

CONCLUSIONS

Whether the associations observed were causal is unclear from these data.

Occupational and environmental agents as endocrine disruptors: experimental and human evidence

In the last few years great concern has arisen from the description of adverse endocrine effects of several occupational and environmental chemical agents on human and/or wildlife health. Such agents may exert their effects directly, specifically binding to hormone receptors, and/or indirectly, by altering the structure of endocrine glands and/or synthesis, release, transport, metabolism or action of endogenous hormones. Many studies have been focused on the outcomes of the exposure to those chemicals mimicking estrogenic or androgenic actions. Nonetheless, the disruption of other hormonal pathways is not negligible. This paper reviews the experimental and human evidence of the effects of occupational and environmental chemical agents on hypothalamus-pituitary unit, pineal gland, parathyroid and calcium metabolism and adrenal glands.

Psychological effects upon exposure to polyhalogenated dibenzodioxins and dibenzofurans

Thirty workers who had been exposed to combustion products for several years due to testing of flame retarding qualities of building materials and 30 controls from the same facility were investigated. Concentrations found in samples taken from different places of the facility were up to 14,660 microg/kg for polybrominated dibenzofurans and up to 67.1 microg/kg for polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). Physical examination, routine laboratory parameters, and blood fat concentrations of PCDDs and PCDFs revealed normal findings. Neurotoxic symptoms showed a weak tendency of overrepresentation among the exposed workers. The frequency of neurobehavioural symptoms increased significantly with trait anxiety independent of exposure to combustion products.