Environmental toxins, a potential risk factor for diabetes among Canadian Aboriginals

Contextualization of Diabetes: A Review of Reviews from Organisation for Economic Co-operation and Development (OECD) Countries

PURPOSE OF REVIEW

The prevalence of diabetes is rising around the world and represents an important public health concern. Unlike individual-level risk and protective factors related to the etiology of diabetes, contextual risk factors have been much less studied. Identification of contextual factors related to the risk of type 1 and type 2 diabetes in Organisation for Economic Co-operation and Development (OECD) countries may help health professionals, researchers, and policymakers to improve surveillance, develop policies and programs, and allocate funding.

RECENT FINDINGS

Among 4,470 potential articles, 48 were included in this review. All reviews were published in English between 2005 and 2023 and were conducted in over 20 different countries. This review identified ten upstream contextual risk factors related to type 1 and type 2 diabetes risk, including income, employment, education, immigration, race/ethnicity, geography, rural/urban status, built environment, environmental pollution, and food security/environment. The ten upstream contextual risk factors identified this review may be integrated into diabetes research, surveillance and prevention activities to help promote better outcomes for people at risk or living with diabetes in OECD countries. Additional research is needed to better quantify the measures of associations between emerging key contextual factors and diabetes outcomes.

Non-persistent exposures from plasticizers or plastic constituents in remote Arctic communities: a case for further research

BACKGROUND

Persistent organic pollutant exposures are well-documented in the Arctic, but fewer studies examined non-persistent chemicals, despite increased market food and consumer product consumption.

OBJECTIVE

To measure phenol, paraben, phthalate, and alternative plasticizer concentrations in Inuit adults.

METHODS

The study included 30 pooled urine samples from Qanuilirpitaa? 2017 Nunavik Inuit Health Survey (Q2017) participants. Creatinine-adjusted geometric mean concentrations (GM) and 95% confidence intervals (CI) were compared across sex, age, and regions, and compared to those in the Canadian Health Measures Survey (CHMS) and the First Nations Biomonitoring Initiative (FNBI).

RESULTS

Q2017 bisphenol-A concentrations were double the CHMS 2018-2019 concentrations [GM (95% CI): 1.98 (1.69-2.31) versus 0.71 (0.60-0.84) µg/g creatinine], but in line with FNBI [1.74 (1.41-2.13) µg/g creatinine]. Several phthalate concentrations were higher in Q2017 versus CHMS, particularly monobenzyl phthalate, which was was 19-fold higher in Q2017 versus CHMS 2018-2019 [45.26 (39.35-52.06) versus 2.4 (2.0-2.9) µg/g creatinine] and four-fold higher than FNBI. There were also four-fold higher concentrations of the two alternate plasticizer 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TIXB) metabolites in Q2017 compared to CHMS 2018-2019. Women and people living in Ungava Bay had generally higher concentrations of non-persistent chemicals.

SIGNIFICANCE

The results suggest higher concentrations of certain non-persistent chemicals in Inuit versus the general Canadian population.

IMPACT

Few studies have explored non-persistent chemical distributions in Northern communities, despite the increasing consumer product and market food consumption. We analyzed 30 pooled samples from the Qanuilirpitaa? Nunavik Inuit Health Survey 2017 to assess exposures to common plasticizes and plastic constituents and compare their levels with the general Canadian population and First Nation groups. We observed particularly higher levels of bisphenol-A, of monobenzyl phthalate, and of two 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) metabolites among Nunavimmiut compared to the general Canadian population, notably among women and Ungava Bay residents. Larger studies are required to confirm our findings and identify potential adverse health effects from these exposures.

Providing culturally safe care to Indigenous people living with diabetes: Identifying barriers and enablers from different perspectives

In recent years, cultural safety has been proposed as a transformative approach to health care allowing improved consideration of Indigenous patient needs, expectations, rights and identities. This community‐based participatory study aimed to identify potential barriers and enablers to cultural safety in health care provided to Atikamekw living with diabetes in Québec, Canada. Based on a qualitative descriptive design, the study uses talking circles as a data collection strategy. Three talking circles were conducted with Atikamekw living with diabetes and caregivers, as well as with health professionals of the family medicine teaching clinic providing services to the community. Two team members performed deductive thematic analysis based on key dimensions of cultural safety. Results highlight four categories of barriers and enablers to cultural safety for Atikamekw living with diabetes, related to social determinants of health (including colonialism), health services organization, language and communication, as well as Atikamekw traditional practices and cultural perspectives of health. This study is one of the few that provides concrete suggestions to address key aspects of diabetes care in a culturally respectful way. Our findings indicate that potential enablers of cultural safety reside at different (from individual to structural) levels of change. Solutions in this matter will require strong political will and policy support to ensure intervention sustainability.

Patient or public contribution

Partners and patients have been involved in identifying the need for this study, framing the research question, developing the data collection tools, recruiting participants and interpreting results.

A State-of-the-Art Review of Indigenous Peoples and Environmental Pollution

Indigenous peoples (IPs) worldwide are confronted by the increasing threat of pollution. Based on a comprehensive review of the literature (n = 686 studies), we present the current state of knowledge on: 1) the exposure and vulnerability of IPs to pollution; 2) the environmental, health, and cultural impacts of pollution upon IPs; and 3) IPs' contributions to prevent, control, limit, and abate pollution from local to global scales. Indigenous peoples experience large burdens of environmental pollution linked to the expansion of commodity frontiers and industrial development, including agricultural, mining, and extractive industries, as well as urban growth, waste dumping, and infrastructure and energy development. Nevertheless, IPs are contributing to limit pollution in different ways, including through environmental monitoring and global policy advocacy, as well as through local resistance toward polluting activities. This work adds to growing evidence of the breadth and depth of environmental injustices faced by IPs worldwide, and we conclude by highlighting the need to increase IPs' engagement in environmental decision-making regarding pollution control. Integr Environ Assess Manag 2020;16:324-341. © 2019 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Cyp2b-null male mice are susceptible to diet-induced obesity and perturbations in lipid homeostasis

Obesity is an endemic problem in the United States and elsewhere, and data indicate that in addition to overconsumption, exposure to specific chemicals enhances obesity. CYP2B metabolizes multiple endo- and xenobiotics, and recent data suggests that repression of Cyp2b activity increases dyslipidemia and age-onset obesity, especially in males. To investigate the role played by Cyp2b in lipid homeostasis and obesity, we treated wildtype and Cyp2b-null mice with a normal (ND) or 60% high-fat diet (HFD) for 10 weeks and determined metabolic and molecular changes. Male HFD-fed Cyp2b-null mice weigh 15% more than HFD-fed wildtype mice, primarily due to an increase in white adipose tissue (WAT); however, Cyp2b-null female mice did not demonstrate greater body mass or WAT. Serum parameters indicate increased ketosis, leptin and cholesterol in HFD-fed Cyp2b-null male mice compared to HFD-fed wildtype mice. Liver triglycerides and liver:serum triglyceride ratios were higher than their similarly treated wildtype counterparts in Cyp2b-null male mice, indicating a role for Cyp2b in fatty acid metabolism regardless of diet. Furthermore, RNAseq demonstrates that hepatic gene expression in ND-fed Cyp2b-null male mice is similar to HFD-fed WT male mice, suggestive of fatty liver disease progression and a role for Cyp2b in lipid homeostasis. Females did not show as demonstrative changes in liver health, and significantly fewer changes in gene expression, as well as gene expression associated with liver disease. Overall our data indicates that the repression or inhibition of CYP2B may exacerbate metabolic disorders and cause obesity by perturbing fatty acid metabolism, especially in males.

High fat diet induced obesity is mitigated in Cyp3a-null female mice

Recent studies indicate a role for the constitutive androstane receptor (CAR), pregnane X-receptor (PXR), and hepatic xenobiotic detoxifying CYPs in fatty liver disease or obesity. Therefore, we examined whether Cyp3a-null mice show increased obesity and fatty liver disease following 8-weeks of exposure to a 60% high-fat diet (HFD). Surprisingly, HFD-fed Cyp3a-null females fed a HFD gained 50% less weight than wild-type (WT; B6) females fed a HFD. In contrast, Cyp3a-null males gained more weight than WT males, primarily during the first few weeks of HFD-treatment. Cyp3a-null females also recovered faster than WT females from a glucose tolerance test; males showed no difference in glucose tolerance between the groups. Serum concentrations of the anti-obesity hormone, adiponectin are 60% higher and β-hydroxybutyrate levels are nearly 50% lower in Cyp3a-null females than WT females, in agreement with reduced weight gain, faster glucose response, and reduced ketogenesis. In contrast, Cyp3a-null males have higher liver triglyceride concentrations and lipidomic analysis indicates an increase in phosphatidylinositol, phosphatidylserine and sphingomyelin. None of these changes were observed in females. Last, Pxr, Cyp2b, and IL-6 expression increased in Cyp3a-null females following HFD-treatment. Cyp2b and Fatp1 increased, while Pxr, Cpt1a, Srebp1 and Fasn decreased in Cyp3a-null males following a HFD, indicating compensatory biochemical responses in male (and to a lesser extent) female mice fed a HFD. In conclusion, lack of Cyp3a has a positive effect on acclimation to a HFD in females as it improves weight gain, glucose response and ketosis.

Association between fish consumption, dietary omega-3 fatty acids and persistent organic pollutants intake, and type 2 diabetes in 18 First Nations in Ontario, Canada

BACKGROUND

First Nations (FNs) populations in Canada experience a disproportionally higher rate of obesity and type 2 diabetes (T2D) compared to the general population. Recent data suggest that a high consumption of fish may help prevent T2D. On the other hand, fish might also be a potential source of environmental contaminants which could potentially be a risk factor for T2D.

OBJECTIVE

To investigate the potential associations between self-reported T2D and consumption of locally-harvested fish, dietary long-chain omega-3 fatty acids (n-3FAs) and persistent organic pollutants intake among adult FNs living on reserve in Ontario.

DESIGN

Data from the First Nations Food Nutrition and Environment Study, which included a cross-sectional study of 1429 Ontario FNs adults living in 18 communities across 4 ecozones in 2012 were analyzed. Social and lifestyle data were collected using household interviews. The consumption of locally-harvested fish was estimated using a traditional food frequency questionnaire along with portion size information obtained from 24hr recalls. Fish samples were analyzed for the presence of contaminants including dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs). Dietary intakes of DDE and PCBs were estimated using community-specific levels of DDE/PCBs in fish species. Multiple logistic regression models adjusted for potential covariates including age, gender, body mass index, physical activity, total energy intake, smoking, and education were developed.

RESULTS

The prevalence of T2D in Ontario FNs was 24.4%. A significant positive association between fish consumption of one portion per week and more and T2D compared to no fish consumption was found (OR=2.5 (95% CI: 1.38-4.58). Dietary DDE and PCBs intake was positively associated with T2D (OR=1.09 (95%CI: 1.05-1.75) for DDE and OR=1.07 (95%CI: 1.004-1.27) for PCBs) per unit increase in DDE/PCBs while n-3-FAs intake, adjusted for DDE/PCBs intake, showed an inverse effect against T2D among older individuals (OR=0.86 (95% CI: 0.46-0.99).

CONCLUSION

Our results support previous findings that exposure to DDE and PCBs may increase the risk of T2D. Elevated levels of contaminants in fish may counteract with potentially beneficial effects of n-3FAs from fish consumption. However, the overall health benefits of high consumption of fish with a high n-3 FAs content may outweigh the adverse effect of contaminants.

Persistent organic pollutants and diabetes among Inuit in the Canadian Arctic

Type 2 diabetes is a chronic metabolic disease that is of increasing concern in Inuit communities. Behavioural factors such as physical inactivity and poor diet are well-known risk factors. Exposure to persistent organic pollutants (POPs) has emerged as an additional factor in the pathogenesis of diabetes. In this study, association between polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) with diabetes in Canadian Inuit was examined. Data from the Adult Inuit Health Survey (2007-2008) of Inuit participants from the Canadian Arctic were analyzed. Self-reported diabetes (excluding gestational diabetes) and clinical measurement of fasting glucose were examined as outcomes. Association with individual PCB congeners, sum of dioxin-like PCBs (∑DL-PCB), non-dioxin-like PCBs (∑NDL-PCB), total PCBs (∑PCB), and p,p'-DDE were investigated using multiple regression models adjusted for confounding factors. Using different methods to incorporate serum lipids, highest vs. lowest quartile exposures to PCB-105, PCB-118, PCB-153, PCB-156, PCB-170, PCB-180, PCB-183, ∑PCB, and p,p'-DDE were associated with increased risk of diabetes. For these PCBs, odds ratios (ORs) ranged from 1.9-3.5 (lower 95% CI: 0.8-1.4, upper 95% CI: 4.4-9.0) and for p,p'-DDE the OR was 2.5 (lower 95% CI: 1.1-1.2, upper 95% CI: 5.9-6.0). The highest vs. lowest quartile exposure to most PCBs and p,p'-DDE were associated with an increase of fasting glucose by 3-7%. PCBs and p,p'-DDE were associated with increased risk of diabetes and higher fasting glucose level in a cross-sectional survey of Canadian Inuit. Cause-effect relationships of PCBs and p,p'-DDE with diabetes and diabetes-related outcomes need to be further investigated in a cohort study.

Association of dioxin and other persistent organic pollutants (POPs) with diabetes: epidemiological evidence and new mechanisms of beta cell dysfunction

The worldwide explosion of the rates of diabetes and other metabolic diseases in the last few decades cannot be fully explained only by changes in the prevalence of classical lifestyle-related risk factors, such as physical inactivity and poor diet. For this reason, it has been recently proposed that other "nontraditional" risk factors could contribute to the diabetes epidemics. In particular, an increasing number of reports indicate that chronic exposure to and accumulation of a low concentration of environmental pollutants (especially the so-called persistent organic pollutants (POPs)) within the body might be associated with diabetogenesis. In this review, the epidemiological evidence suggesting a relationship between dioxin and other POPs exposure and diabetes incidence will be summarized, and some recent developments on the possible underlying mechanisms, with particular reference to dioxin, will be presented and discussed.

Human biological monitoring of suspected endocrine-disrupting compounds

Endocrine-disrupting compounds are exogenous agents that interfere with the natural hormones of the body. Human biological monitoring is a powerful method for monitoring exposure to endocrine disrupting compounds. In this review, we describe human biological monitoring systems for different groups of endocrine disrupting compounds, polychlorinated biphenyls, brominated flame retardants, phthalates, alkylphenols, pesticides, metals, perfluronated compounds, parabens, ultraviolet filters, and organic solvents. The aspects discussed are origin to exposure, metabolism, matrices to analyse, analytical determination methods, determinants, and time trends.

Glucose and lipid homeostasis in adult rat is impaired by early-life exposure to perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS), which belongs to the degradation product of many perfluorinated compounds, is on the list of persistent organic pollutants (POPs) and is currently detected in both wildlife and humans. The consequence of gestational and lactational exposure to PFOS on prediabetes effect in offspring was investigated in rats in the present study. Maternal rats were treated with vehicle, 0.5 mg/kg/day or 1.5 mg/kg/day PFOS respectively from gestation day 0 to postnatal day 21. The glucose and lipid metabolism effects were investigated on the offspring in adulthood. The gestational and lactational exposure to PFOS led to low body weight from birth to weaning, and evoked signs of a prediabetic state, with elevated fasting serum insulin and leptin level, impaired glucose tolerance, though the fasting serum glucose and glycosylated serum protein level were normal. Abnormal lipid homeostasis was also observed by the phenomenon of hepatic steatosis and increased gonadal fat pad weight. However, the circulating serum level of fasting triglyceride and cholesterol level were no different from controls. Our results suggested that developmental exposure to PFOS may contribute to glucose and lipid metabolic disorder in adulthood.

A review of the cardiometabolic risk experience among Canadian Métis populations

Cardiometabolic risk is a growing concern in Western society in which rates of cardiovascular disease, diabetes, and obesity are on the rise. Aboriginal populations currently experience unequal burdens of these chronic conditions. However, limited information regarding the experience of cardiometabolic risk among Métis populations is available. This review sought to evaluate the cardiometabolic risk experience among Métis populations in Canada. Canada's Métis population currently experiences greater burdens of chronic conditions including metabolic syndrome, diabetes, obesity, and cardiovascular disease than that of the non-Aboriginal population. Métis populations also experience poorer life expectancy, education, and employment attainments, and reduced access to health care services compared with non-Aboriginal populations. Interventions addressing the deficiencies in sociodemographic, lifestyle, and social determinants among the Métis population might help combat rising experiences of chronic diseases faced by these people. Though the burden of chronic conditions, sociodemographic, lifestyle challenges, and social determinants of health among Métis populations are generally less than that of First Nations populations, Métis people experience these health challenges and influencing factors are generally more similar to that of First Nations than non-Aboriginal peoples. Subsequently, Métis populations need to be included in plans and strategies to reduce chronic conditions among Aboriginal populations. In conclusion, Métis populations experience greater burden of cardiometabolic risk and its components than the general Canadian population.

Chronic exposure to PCBs (Aroclor 1254) exacerbates obesity-induced insulin resistance and hyperinsulinemia in mice

Evidence from recent epidemiological studies has emerged implicating exposure to environmental toxicants as a novel risk factor for the development of type 2 diabetes (T2D) and the metabolic syndrome in the general population. Humans and other organisms in high trophic levels of the food chain consume persistent organic pollutants (POP) through their diet. Few experimental studies demonstrating cause and effect are available and evidence for a direct association between accumulation of POP and T2D is preliminary; however, the possibility exists that lipophilic chemicals that accumulate in fatty tissue may disrupt cellular function and metabolic homeostasis. Chronic exposure of diabetes-prone C57B/6 mice to a polychlorinated biphenyl (PCB) mixture (Aroclor 1254, 36 mg/kg/wk, 20 wk) alone or in combination with high-fat diet impairs carbohydrate metabolism was compared to vehicle-treated control animals. Specifically, PBC exposure was found to produce hyperinsulinemia in both lean and diet-induced obese mice and exacerbated whole-body insulin resistance in obese mice. These changes in carbohydrate metabolism in response to Aroclor 1254 occurred without marked effect on body weight in both lean and obese mice. Our results demonstrate a causative association between PCB exposure and obesity-induced insulin resistance and hyperinsulinemia independent of body weight changes, an observation that contributes to a growing body of evidence suggesting that exposure to environmental pollutants represents a novel risk factor contributing to the diabetes epidemic.

Indigenous peoples of North America: environmental exposures and reproductive justice

BACKGROUND

Indigenous American communities face disproportionate health burdens and environmental health risks compared with the average North American population. These health impacts are issues of both environmental and reproductive justice.

OBJECTIVES

In this commentary, we review five indigenous communities in various stages of environmental health research and discuss the intersection of environmental health and reproductive justice issues in these communities as well as the limitations of legal recourse.

DISCUSSION

The health disparities impacting life expectancy and reproductive capabilities in indigenous communities are due to a combination of social, economic, and environmental factors. The system of federal environmental and Indian law is insufficient to protect indigenous communities from environmental contamination. Many communities are interested in developing appropriate research partnerships in order to discern the full impact of environmental contamination and prevent further damage.

CONCLUSIONS

Continued research involving collaborative partnerships among scientific researchers, community members, and health care providers is needed to determine the impacts of this contamination and to develop approaches for remediation and policy interventions.

Low levels of arsenic in drinking water and type 2 diabetes in Middle Banat region, Serbia

Arsenic in drinking water presents a serious public health problem in Serbia, but its relationship with diabetes has not been studied previously. The aim of this study was to explore the association between exposure to arsenic in drinking water and the occurrence of type 2 diabetes in Middle Banat region, Serbia. This cross-sectional study comprised two populations. Exposed population in Middle Banat region consumes drinking water with arsenic (mean = 56 μg/L); unexposed population from six regions in Central Serbia consumes arsenic below detection limit (2 μg/L). Newly diagnosed cases of type 2 diabetes were obtained from the National Registry of Diabetes in 2008. The Registry included age, gender, family history of diabetes, presence of overweight, central obesity, cholesterol and triglyceride levels. In addition, the number of cases of diabetes reported in years 2006, 2007 and 2009 was used to calculate standardized incidence rates for both populations. Two populations were comparable by age, family history of diabetes and prevalence of overweight persons. Unexposed population was more likely to have central obesity, and high total cholesterol and triglycerides. Standardized incidence rates of type 2 diabetes were higher in exposed population. Odds ratios for type 2 diabetes were significantly higher for the exposed population, both men and women, in the period from 2006 to 2009, when compared with the unexposed population. The population from Middle Banat region, consuming drinking water with low levels of arsenic, was at higher risk for the occurrence of type 2 diabetes in comparison to the unexposed population in Central Serbia.

Human excretion of bisphenol A: blood, urine, and sweat (BUS) study

BACKGROUND

Bisphenol A (BPA) is an ubiquitous chemical contaminant that has recently been associated with adverse effects on human health. There is incomplete understanding of BPA toxicokinetics, and there are no established interventions to eliminate this compound from the human body. Using 20 study participants, this study was designed to assess the relative concentration of BPA in three body fluids-blood, urine, and sweat-and to determine whether induced sweating may be a therapeutic intervention with potential to facilitate elimination of this compound.

METHODS

Blood, urine, and sweat were collected from 20 individuals (10 healthy participants and 10 participants with assorted health problems) and analyzed for various environmental toxicants including BPA.

RESULTS

BPA was found to differing degrees in each of blood, urine, and sweat. In 16 of 20 participants, BPA was identified in sweat, even in some individuals with no BPA detected in their serum or urine samples.

CONCLUSIONS

Biomonitoring of BPA through blood and/or urine testing may underestimate the total body burden of this potential toxicant. Sweat analysis should be considered as an additional method for monitoring bioaccumulation of BPA in humans. Induced sweating appears to be a potential method for elimination of BPA.

Omega-3 fatty acids and incident type 2 diabetes: the Singapore Chinese Health Study

BACKGROUND

The role of omega-3 (n-3) fatty acids (FAs) in the development of type 2 diabetes is uncertain, especially with regard to any differential influence of α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

OBJECTIVE

The objective was to examine the association between total omega-3 FAs, marine omega-3 (EPA, DHA), nonmarine omega-3 (ALA), and omega-6 (n-6) FAs and omega-6:omega-3 ratio and risk of type 2 diabetes in a Chinese population in Singapore.

DESIGN

The analysis included 43,176 Chinese men and women free of chronic disease, aged 45-74 y, in the Singapore Chinese Health Study. Baseline data collection occurred between 1993 and 1998, with follow-up interviews between 1999 and 2004. Cox regression models were used to examine the associations between FA intakes at baseline and risk of developing diabetes.

RESULTS

Increased intakes of total omega-3 FAs were inversely associated with diabetes incidence [hazard ratio (HR) for the fifth compared with the first quintile: 0.78; 95% CI: 0.65, 0.94; P for trend = 0.02]. Omega-3 FAs from marine sources were not associated with diabetes risk, whereas nonmarine omega-3 FA intake was strongly associated (HR for the fifth compared with the first quintile: 0.79; 95% CI: 0.67, 0.93; P for trend = 0.004). Omega-6 and omega-6:omega-3 ratio were not associated with incidence of type 2 diabetes.

CONCLUSION

Consumption of nonmarine sources (ALA) of omega-3 FAs is associated with a decreased risk of type 2 diabetes in Chinese Singaporeans.

Polychlorinated biphenyls and organochlorine pesticides in plasma predict development of type 2 diabetes in the elderly: the prospective investigation of the vasculature in Uppsala Seniors (PIVUS) study

OBJECTIVE

Persistent organic pollutants (POPs), lipophilic chemicals that accumulate mainly in adipose tissue, have recently been linked to type 2 diabetes. However, evidence from prospective studies is sparse. This study was performed to evaluate prospective associations of type 2 diabetes with selected POPs among the elderly.

RESEARCH DESIGN AND METHODS

Nineteen POPs (14 polychlorinated biphenyl [PCB] congeners, 3 organochlorine pesticides, 1 brominated diphenyl ether, and 1 dioxin) were measured in plasma collected at baseline in 725 participants, aged 70 years, of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS).

RESULTS

After adjusting for known type 2 diabetes risk factors, including obesity, odds ratios (ORs) (95% CIs) for type 2 diabetes at age 75 years (n = 36) according to the quintiles of a summary measure of concentrations of PCBs (vs. the lowest quintile) were 4.5, 5.1, 8.8 (1.8-42.7), and 7.5 (1.4-38.8) (P(trend) <0.01). Among organochlorine pesticides, adjusted ORs across concentrations of trans-nonachlor showed that P(trend) = 0.03. Adjusted ORs (95% CIs) across quintiles of the sum of three organochlorine pesticides were 1.1, 1.6, 1.5, and 3.4 (1.0-11.7) (P(trend) = 0.03). Neither brominated diphenyl ether 47 nor dioxin was significantly associated with incident diabetes. The sum of PCBs improved reclassification significantly when added to traditional risk factors for diabetes.

CONCLUSIONS

Despite the small number of incident cases, this study found that environmental exposure to some POPs substantially increased risk of future type 2 diabetes in an elderly population.

A novel method for reducing the number of agents to be studied in an occupational epidemiologic study

A novel screening tool method to select chemicals for exposure reconstruction was developed and validated using data generated for a hypothetical work force consisting of 10 job classes (ranging from 10,000 to 55,000 person-years). To achieve the required efficiency in the reconstruction of exposures, this method treats each product (defined as a part or process) as an "exposure." Exposure to 10 products was assigned to each job class at random using a computer program. The expected rate of a given disease was assumed to be constant throughout the job classes (tested at five levels), and the observed numbers of cases in the job classes were generated based on neutral deviations from background with error rates of ± 1% to 16%. One job class was assigned to be the "excess-class" and the number of cases in that class was increased by a factor of Q, which was set at levels that ranged from 1.25 to 5. All of the experimental conditions were replicated 10,000 times in a Monte Carlo scheme for scenarios in which each job class had been designated as the excess-class. Following each run, significant excesses (if any) were determined using a modified version of Daniel's method, and the percentages of false positive and false negative identifications were tabulated. We found that the sensitivity of the method is largely dependent on the relative risk (Q) associated with the exposure. Specifically, the results indicate that as the relative risk increases, the percentage of false negative identifications of the excesses is reduced to nearly 0% and the percentage of false positive identifications is approximately 13%. When applied to real data, should an association be detected between any product and a health outcome, this preliminary analysis will yield a reduced "product" set that can then be investigated in detail and the agents involved considered further for quantitative reconstruction. The proposed method is highly efficient and has the potential to benefit future complex exposure reconstruction studies, particularly when there is no predetermined exposure associated with an observed increase in a cause-specific health end point.

Methylmercury-induced neurotoxicity and apoptosis

Methylmercury is a widely distributed environmental toxicant with detrimental effects on the developing and adult nervous system. Due to its accumulation in the food chain, chronic exposure to methylmercury via consumption of fish and sea mammals is still a major concern for human health, especially developmental exposure that may lead to neurological alterations, including cognitive and motor dysfunctions. Mercury-induced neurotoxicity and the identification of the underlying mechanisms has been a main focus of research in the neurotoxicology field. Three major mechanisms have been identified as critical in methylmercury-induced cell damage including (i) disruption of calcium homeostasis, (ii) induction of oxidative stress via overproduction of reactive oxygen species or reduction of antioxidative defenses and (iii) interactions with sulfhydryl groups. In vivo and in vitro studies have provided solid evidence for the occurrence of neural cell death, as well as cytoarchitectural alterations in the nervous system after exposure to methylmercury. Signaling cascades leading to cell death induced by methylmercury involve the release of mitochondrial factors, such as cytochrome c and AIF with subsequent caspase-dependent or -independent apoptosis, respectively; induction of calcium-dependent proteases calpains; interaction with lysosomes leading to release of cathepsins. Interestingly, several pathways can be activated in parallel, depending on the cell type. In this paper, we provide an overview of recent findings on methylmercury-induced neurotoxicity and cell death pathways that have been described in neural and endocrine cell systems.