A pharmacokinetic analysis and dietary information are necessary to confirm or reject the hypothesis on persistent organic pollutants causing type 2 diabetes

United States Environmental Protection Agency's Perfluorooctanoic Acid, Perfluorooctane Sulfonic Acid, and Related Per- and Polyfluoroalkyl Substances 2024 Drinking Water Maximum Contaminant Level: Part 2 - Fifteen Misconceptions About the Health Hazards

This paper examines widely held beliefs about the six per- and polyfluoroalkyl substances (PFAS) addressed in the final U.S. Environmental Protection Agency's (EPA) rule on PFAS in drinking water (e.g., the Maximum Contaminant Levels - MCLs). Based on our understanding of the scientific literature and the comments submitted by stakeholders regarding the EPA's regulation that was promulgated in April 2024, we identified 15 misconceptions that had a weak scientific foundation. These are now memoralized in the MCLs for the six PFAS but remain debated due to ongoing ambiguous research findings. Many critics of the MCLs found the EPA's systematic review of the published relevant information, particularly the toxicology of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), to be inadequate. The following seven views are among the most important. First, the EPA asserted that the toxicology of these six chemicals was poorly understood and lacked sufficient data to determine a safe daily intake level for chronic health effects; nonetheless, they promulgated what may be the costliest environmental regulation to date. Notably, adverse effects remain difficult to demonstrate in occupationally exposed individuals even at blood concentrations 50-100 times higher than current background PFAS levels. Second, the Agency indicated that the epidemiology data showed that exposure to PFOA and PFOS caused kidney and potentially other cancers, yet the data were equivocal and do not support that assertion. Third, it was stated that specific non-cancer effects, such as heart disease, would be prevented under the promulgated rule; however, the studies that they relied upon do not show an increased incidence of heart disease even in highly exposed populations. Fourth, the Agency relied on animal data to support its views on the likely toxic effects in humans, despite ample toxicology data that animals, particularly rodents, are poor predictors of the human response to PFAS exposures. Fifth, the EPA predicted a reduction in healthcare expenditures that would offset much of the cost of complying with the MCL, but, they did not have adequate data to support this prediction. Sixth, the EPA suggested that these six PFAS act through a shared mechanism of action (i.e., PPARα pathway induction); however, data indicate that PPARα induction in humans may be 80% less than what is observed in rodents. Also, induction of the PPARα pathway is not a cause of systemic disease. Seventh, the Agency failed to disclose that achieving the new MCL would yield negligible reductions in blood PFAS levels even among highly exposed populations, given drinking water accounts for only 20% or less of total PFAS exposure. The survey that could answer that question, the EPA's fifth Unregulated Contaminant Monitoring Rule, was only 25% complete at the time the MCL was promulgated. Overall, our analysis concluded that while the EPA's intent to regulate these chemicals due to their environmental presence was necessary, the derivation of the MCLs and the alleged health effects was based on the application of the precautionary principle rather than robust scientific evidence.

Health effects associated with measured contaminants in the Arctic: short communication

The Arctic Monitoring Assessment Program Human Health Assessment report 2021 presents a summary of the presence of environmental contaminants in human populations across the circumpolar Arctic and related health effects. Based on this report the objective of this paper is giving a short summary of the health effects related to the current level of persistent organic pollutants (POP) and metals. The overall key findings are as follows: i. metals and POP (polychlorinated biphenyls, per- and polyfluoroalkyl substances (PFAS)) in the Arctic have known adverse health impacts on humans especially on developing foetuses and children. Lifestyle, diet and nutrition and genetics influence the risk; ii. POP and metals negatively impact the brain and immune system, increasing the risk of childhood obesity, type 2 diabetes later in life and negatively affect foetal growth and development: iii. marine food omega-3 fatty acids can diminish adverse effects of high mercury exposure on cardiovascular and neurological outcomes; iv. the interaction of genetic, lifestyle, nutrition status and contaminants can influence the risk of cancer, metabolic disease, nervous system disorders, disruption of reproduction and foetal and child growth. Future investigations must focus on genetically and effect modifiers and mixtures of POP exposures to explore the effect of chemical interaction on health outcomes.

Association between brominated flame retardants and risk of endocrine-related cancer: A systematic review and meta-analysis

BACKGROUND

The incidence of endocrine-related cancer, which includes tumors in major endocrine glands such as the breast, thyroid, pituitary, and prostate, has been increasing year by year. Various studies have indicated that brominated flame retardants (BFRs) are neurotoxic, endocrine-toxic, reproductive-toxic, and even carcinogenic. However, the epidemiological relationship between BFR exposure and endocrine-related cancer risk remains unclear.

METHODS

We searched the PubMed, Google Scholar, and Web of Science databases for articles evaluating the association between BFR exposure and endocrine-related cancer risk. The odds ratio (OR) and its corresponding 95% confidence interval (95% CI) were used to assess the association. Statistical heterogeneity among studies was assessed with the Q-test and I2 statistics. Begg's test was performed to evaluate the publication bias.

RESULTS

We collected 15 studies, including 6 nested case-control and 9 case-control studies, with 3468 cases and 4187 controls. These studies assessed the risk of breast cancer, thyroid cancer, and endocrine-related cancers in relation to BFR levels. Our findings indicate a significant association between BFR exposure in adipose tissue and an increased risk of breast cancer. However, this association was not observed for thyroid cancer. Generally, BFR exposure appears to elevate the risk of endocrine-related cancers, with a notable increase in risk linked to higher levels of BDE-28, a specific polybrominated diphenyl ether congener.

CONCLUSIONS

In conclusion, although this meta-analysis has several limitations, our results suggest that BFR exposure is a significant risk factor for breast cancer, and low-brominated BDE-28 exposure could significantly increase the risk of endocrine-related cancers. Further research is essential to clarify the potential causal relationships between BFRs and endocrine-related cancers, and their carcinogenic mechanisms.

Associations between per- and polyfluoroalkyl substances (PFAS) and diabetes in two population-based cohort studies from Sweden

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) have been suggested to contribute to the development of metabolic diseases such as obesity, diabetes and non-alcoholic fatty liver disease (NAFLD). However, evidence from epidemiological studies remain divergent. The aim of the present study was to evaluate associations between PFAS exposure and prevalent diabetes in a cross-sectional analysis and fasting glucose in a longitudinal analysis.

METHODS

In 2373 subjects aged 45-75 years from the EpiHealth study, three PFAS; perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were analyzed in plasma together with information on prevalent diabetes. Participants in the PIVUS study (n = 1016 at baseline, all aged 70 years) were followed over 10 years regarding changes in plasma levels of six PFAS; PFHxS, PFOA, PFOS, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA), and changes in plasma levels of fasting glucose.

RESULTS

In the EpiHealth study, no overall associations could be observed between the levels of PFOA, PFOS or PFHxS and prevalent diabetes. However, there was a significant sex-interaction for PFOA (p = 0.02), and an inverse association could be seen between PFOA (on a SD-scale) and prevalent diabetes in women only (OR: 0.71, 95% CI: 0.52, 0.96, p-value: 0.02). This association showed a non-monotonic dose-response curve. In the PIVUS study, inverse relationships could be observed between the changes in levels (ln-transformed) of PFOA and PFUnDA vs the change in fasting glucose levels (ln-transformed) over 10 years (p = 0.04 and p = 0.02, respectively). As in EpiHealth, these inverse associations were significant only in women (PFOA: β: -0.03, p = 0.02, PFUnDA: β: -0.03, p = 0.03).

IMPACT

Exposure to per- and polyfluoroalkyl substances (PFAS) has been linked to unfavorable human health, including metabolic disorders such as obesity, diabetes and non-alcoholic fatty liver disease. However, results from in vivo, in vitro and epidemiological studies are incoherent. The aim of the present study was therefore to investigate associations between PFAS and diabetes in a cross-sectional study and glucose levels in a longitudinal study. Results show inverse associations in women only. Results also display non-monotonic dose response curves (i.e., that only low levels of PFOA are related to higher probability of prevalent diabetes). This suggests that sex differences and complex molecular mechanisms may underlie the observed findings. A better understanding of the factors and molecular mechanisms contributing to such differences is recognized as an important direction for future research.

CONCLUSIONS

PFOA was found to be inversely related to both prevalent diabetes and changes in plasma glucose levels among women only. Thus, our findings suggest there are sex differences in the inverse relationship of PFOA and type 2 diabetes and glucose levels.

Exposure to novel brominated and organophosphate flame retardants and associations with type 2 diabetes in East China: A case-control study

The alternative flame retardants, novel brominated flame retardants (NBFRs) and organophosphate flame retardants (OPFRs) are ubiquitous in the environment and biota and may induce endocrine disruption effects. Associations between traditional endocrine-disrupting chemicals and type 2 diabetes have been extensively reported in epidemiological studies. However, the effects of NBFRs and OPFRs in humans have not been reported to date. This paper reports a case-control study of 344 participants aged 25-80 years from Shandong Province, East China, where potential associations between serum NBFR and OPFR concentrations and type 2 diabetes are assessed for the first time. After adjusting for covariates (i.e., age, sex, body mass index, smoking status, alcohol consumption, triglycerides, and total cholesterol), serum concentrations of pentabromotoluene, 2,3-dibromopropyl 2,4,6-tribromophenyl ether, tri-n-propyl phosphate, triphenyl phosphate, and tris (2-ethylhexyl) phosphate were significantly positively associated with type 2 diabetes. In the control group, decabromodiphenyl ethane and triphenyl phosphate were significantly positively associated with fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol. In the quantile g-computation model, significant positive mixture effect was found between the flame retardants mixtures and high-density lipoprotein cholesterol levels, and decabromodiphenyl ethane contributed the largest positive weights to the mixture effect. Overall, these findings suggest that exposure to NBFRs and OPFRs may promote type 2 diabetes.

Association of endocrine active environmental compounds with body mass index and weight loss following bariatric surgery

INTRODUCTION

The objective of this study was to study associations of a wide range of halogenated biphenyls, dibenzo-p-dioxins, dibenzofurans and diphenylethers with body mass index (BMI) and evaluate changes in their concentration following bariatric surgery.

METHODS

Subcutaneous fat, visceral fat and liver tissue samples were collected from 106 patients undergoing Roux-en-Y gastric bypass surgery for weight loss or patients who were undergoing abdominal surgery for nonbariatric reasons. We measured concentrations of an extensive panel of chlorinated and brominated biphenyls, dioxins, and furans, and brominated diphenylethers in the samples. We conducted linear regression to examine associations with BMI, adjusting for age and gender. Changes in concentration for indicator chemicals were evaluated in samples collected following bariatric surgery in a small subpopulation.

RESULTS

After adjustments for age and gender and correction for multiple testing, seven ortho-chlorinated biphenyls, one nonortho-chlorinated biphenyl, four PCDD/Fs and one ortho-brominated biphenyl were associated with BMI. The strongest associations between BMI and lipid-adjusted concentrations were seen with PCB-105 in subcutaneous fat (beta = 16.838 P-val = 1.45E-06) PCB-126 in visceral fat (beta = 15.067 P-val = 7.72E-06) and PCB-118 (beta = 14.101 P-val = 2.66E-05) in liver. The concentrations of sum PCBs, chlorinated toxic equivalent quantity (TEQ's) and brominated compounds increased significantly with weight loss in subcutaneous fat in a group of ten individuals resampled up to five years after bariatric surgery and substantial weight loss.

CONCLUSION

We show that selected polychlorinated biphenyls PCBs and structurally related polychlorinated dibenzo-p-dioxins dibenzofurans (PCDD/Fs) were associated with BMI. Concentrations of these lipophilic compounds in subcutaneous fat increased following bariatric surgery.

Long-term metabolic consequences of acute dioxin exposure differ between male and female mice

Epidemiological studies have consistently shown an association between exposure to environmental pollutants and diabetes risk in humans. We have previously shown that direct exposure of mouse and human islets (endocrine pancreas) to the highly persistent pollutant TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) causes reduced insulin secretion ex vivo. Furthermore, a single high-dose of TCDD (200 µg/kg) suppressed both fasting and glucose-induced plasma insulin levels and promoted beta-cell apoptosis after 7 days in male mice. The current study investigated the longer-term effects of a single high-dose TCDD injection (20 µg/kg) on glucose metabolism and beta cell function in male and female C57Bl/6 mice. TCDD-exposed males displayed modest fasting hypoglycemia for ~4 weeks post-injection, reduced fasting insulin levels for up to 6 weeks, increased insulin sensitivity, decreased beta cell area, and increased delta cell area. TCDD-exposed females also had long-term suppressed basal plasma insulin levels, and abnormal insulin secretion for up to 6 weeks. Unlike males, TCDD did not impact insulin sensitivity or islet composition in females, but did cause transient glucose intolerance 4 weeks post-exposure. Our results show that a single exposure to dioxin can suppress basal insulin levels long-term in both sexes, but effects on glucose homeostasis are sex-dependent.

Persistent Organic Pollutants in Food: Contamination Sources, Health Effects and Detection Methods

Persistent organic pollutants (POPs) present in foods have been a major concern for food safety due to their persistence and toxic effects. To ensure food safety and protect human health from POPs, it is critical to achieve a better understanding of POP pathways into food and develop strategies to reduce human exposure. POPs could present in food in the raw stages, transferred from the environment or artificially introduced during food preparation steps. Exposure to these pollutants may cause various health problems such as endocrine disruption, cardiovascular diseases, cancers, diabetes, birth defects, and dysfunctional immune and reproductive systems. This review describes potential sources of POP food contamination, analytical approaches to measure POP levels in food and efforts to control food contamination with POPs.

Chlorinated persistent organic pollutants and type 2 diabetes - A population-based study with pre- and post- diagnostic plasma samples

BACKGROUND

Persistent organic pollutants (POPs) have been associated with type 2 diabetes (T2D), but causality is uncertain.

OBJECTIVE

Within longitudinal population-based data from northern Sweden, we assessed how POPs associated with T2D prospectively and cross-sectionally, and further investigated factors related to individual changes in POP concentrations.

METHODS

For 129 case-controls pairs matched by age, sex and date of sampling, plasma concentrations of hexachlorobenzene (HCB), dichlorodiphenyl-dichloroethylene (p,p'-DDE), dioxin-like (DL) polychlorinated biphenyl congeners (PCB-118 and PCB-156), and non-dioxin like (NDL-PCB: PCB-74, -99, -138 -153, -170, -180, -183 and PCB-187) were analyzed twice (baseline and follow-up, 9-20 years apart). The cases received their T2D diagnose between baseline and follow-up. Prospective (using baseline data) and cross-sectional (using follow-up data) odds ratios (ORs) for T2D on lipid standardized POPs (HCB, p,p'-DDE, ∑DL-PCBs, ∑NDL-PCBs) were estimated using conditional logistic regression, adjusting for body mass index (BMI) and plasma lipids. The influence of BMI, weight-change, and plasma lipids on longitudinal changes in POP concentrations were evaluated among non-diabetic individuals (n = 306).

RESULTS

POPs were associated with T2D in both the prospective and cross-sectional assessments. Of a standard deviation increase in POPs, prospective ORs ranged 1.42 (95% CI: 0.99, 2.06) for ∑NDL-PCBs to 1.55 (95% CI: 1.01, 2.38) for HCB (p < 0.05 only for HCB), and cross-sectional ORs ranged 1.62 (95% CI: 1.13; 2.32) for p,p'-DDE to 2.06 (95% CI: 1.29, 3.28) for ∑DL-PCBs (p < 0.05 for all POPs). In analyses of non-diabetic individuals, higher baseline BMI, decreased weight and decreased plasma lipid concentrations were associated with a slower decrease of POPs. Cases had, besides a higher BMI, reduced cholesterol and weight gain at follow-up compared to controls, which can explain the higher ORs in the cross-sectional assessments.

DISCUSSION

The association between POPs and T2D was confirmed, but an indication that individuals body fat history might influence POP-T2D associations weakens the epidemiological support for a causal association. It also warrants studies based on other exposure metrics than biomonitoring. In addition, we note that a cross-sectional design overestimates the ORs if T2D cases have successfully intervened on weight and/or blood lipids, as changes in these factors cause changes in POPs.

The Influence of Obesity on the Pharmacokinetics of Dioxin in Mice: An Assessment Using Classical and PBPK Modeling

The effects of body fat mass on the elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was examined in mice. When male C57BL/6J mice are fed a high-fat, simple carbohydrate diet (HFD) for 13 weeks, they develop an obese phenotype. In contrast, A/J mice fed an HFD do not become obese. After 13 weeks on a normal diet (ND) or HFD, male C57BL/6J and A/J mice received a single dose by gavage of 0.1 or 5.0 µg of 2,3,7,8-tetrachloro[1,6-3H] dibenzo-p-dioxin per kg body weight. Using classical pharmacokinetics, the blood elimination half-life of TCDD was approximately 10 and 2 times longer in the C57BL/6J on the HFD compared with the mice on the ND at 0.1 and 5.0 μg/kg doses, respectively. The diet did not increase the blood half-life of TCDD in the A/J mice, which did not get obese. Using a physiologically based pharmacokinetic model for TCDD that incorporated experimentally derived percent body fat mass and tissue partition coefficients, as well as data on hepatic sequestration, did not provide accurate predictions to the data and could not explain the increase in half-life of TCDD in the HFD groups. This work demonstrates that obesity influences the half-life of TCDD, but other undetermined factors are involved in its elimination because the increase in body fat mass, decreases in cytochrome P4501A2, and altered partition coefficients could not completely explain the prolonged half-life.

Perfluoroalkyl substances and risk of type II diabetes: A prospective nested case-control study

BACKGROUND

Perfluoroalkyl substances (PFAS) have drawn much attention due to bioaccumulation potential and their current omnipresence in human blood. We assessed whether plasma PFAS, suspected to induce endocrine-disrupting effects, were prospectively associated with clinical type 2 diabetes (T2D) risk.

METHODS

We established a nested case-control study within the Swedish prospective population-based Västerbotten Intervention Programme cohort. Several PFAS were measured in plasma from a subset of 124 case-control pairs at baseline (during 1990-2003) and at 10-year follow-up. T2D cases were matched (1:1) according to gender, age and sample date with participants without T2D (controls). Conditional logistic regressions were used to prospectively assess risk of T2D by baseline PFAS plasma concentrations. Associations between long-term PFAS plasma levels (mean of baseline and follow-up) and insulin resistance (HOMA2-IR) and beta-cell function (HOMA2-B%) at follow-up were prospectively explored among 178 and 181 controls, respectively, by multivariable linear regressions.

RESULTS

After adjusting for gender, age, sample year, diet and body mass index, the odds ratio of T2D for the sum of PFAS (Σ z-score PFAS) was 0.52 (95% confidence interval, CI: 0.20, 1.36), comparing third with first tertile; and 0.92 (95% CI: 0.84, 1.00) per one standard deviation increment of sum of log-transformed PFAS. Among the controls, the adjusted β of HOMA2-IR and HOMA-B% for the sum of PFAS were -0.26 (95% CI: -0.52, -0.01) and -9.61 (95% CI: -22.60, 3.39) respectively comparing third with first tertile.

CONCLUSIONS

This prospective nested case-control study yielded overall inverse associations between individual PFAS and risk of T2D, although mostly non-significant. Among participants without T2D, long-term PFAS exposure was prospectively associated with lower insulin resistance.

Temporal trends of contaminants in Arctic human populations

The first Arctic Monitoring and Assessment Programme (AMAP) report was published in 1998 and followed by three assessment reports of human health (AMAP 2003, 2009 and 2015). The focus area of the AMAP reports was to monitor levels of environmental contaminants in the Arctic and to assess the health effects connected with detected levels in Arctic countries. This review gives an overview of temporal trends of contaminants and their health effects in humans of the Arctic based on data published by AMAP, as well as Russian scientific literature. Several time series of 31 contaminants in humans of the Arctic from different cohorts are reported. The lengths of time series and periods covered differ from each other. International restrictions have decreased the levels of most persistent organic pollutants in humans and food webs. Percentage changes for contaminants in human biological matrices (blood samples from children, mothers and males and breast milk samples) for the period of sampling showed declining trends in most of the monitored Arctic locations, with the exception of oxychlordane, hexachlorobenzene (HCB), 2,2',4,4',5,5'-hexabromodiphenyl ether (PBDE153) and perfluorinated compounds (PFCs).

Persistent Organochlorine Pollutants in Plasma, Blood Pressure, and Hypertension in a Longitudinal Study

Persistent organochlorine pollutants (POPs) have shown to be involved in the atherosclerotic process and to cause endothelial cell dysfunction. To assess longitudinally whether plasma concentrations of different POPs were associated with blood pressure and risk of hypertension in middle-aged women and men. Study subjects were 850 participants in the VIP (Västerbotten Intervention Programme) with 2 blood samples and blood pressure measurements, 10 years apart, during 1990 to 2003 (baseline) and during 2000 to 2013 (follow-up). Dioxin-like and nondioxin-like polychlorinated biphenyls (DL-PCBs, NDL-PCBs) and p,p'-dichlorodiphenyldichloroethylene (DDE) were measured. Associations were assessed using generalized estimating equations. At baseline sampling 49% and at follow-up 64% had hypertension. DL-PCBs and DDE, but not NDL-PCBs or hexachlorobenzene, were associated with hypertension. Only the association for DL-PCBs remained statistically significant after lipid-standardization and adjustment for body mass index and total serum lipids. The multivariable-adjusted odds ratio of hypertension based on repeated measurements were 1.52 (95% confidence interval, 1.08-2.13) for DL-PCBs (third versus first tertile of lipid-standardized POPs). In stratified adjusted analyses, odds ratio for those born after 1950 increased to 3.99 (95% confidence interval, 2.15-7.43), whereas no association was observed among those born earlier. Based on repeated measurements, the accumulated exposure to DL-PCBs and DDE, although less clear for the latter, may disrupt the normal blood pressure levels and increase the odds of hypertension. Moreover, individuals experiencing early-life POP exposure may be at elevated risk of vascular POP effects.

Human adipose tissue levels of persistent organic pollutants and metabolic syndrome components: Combining a cross-sectional with a 10-year longitudinal study using a multi-pollutant approach

We aimed to assess the influence of long-term exposure to POPs on the risk of metabolic syndrome, combining a cross-sectional with a 10-year longitudinal follow-up design. Residues of eight POPs were quantified in adipose tissue samples from 387 participants recruited between 2003 and 2004 in Granada province (Spain). The outcome ("metabolically compromised") was defined as having ≥1 diagnosis of type 2 diabetes, hypertension, hypertriglyceridemia, and/or low HDL cholesterol. The cross-sectional analysis was conducted in the initial cohort, while the 10-year longitudinal analysis was conducted in those 154 participants free of any of the so-mentioned metabolic diseases and classified as "metabolically healthy" at recruitment. Statistical analyses were performed using single and multi-pollutant approaches through logistic and Cox regression analyses with elastic net penalty. After adjusting for confounders, β-hexachlorocyclohexane (β-HCH) and hexachlorobenzene (HCB) were independently associated with an increased risk of being metabolically compromised (unpenalized ORs=1.17, 95% CI=1.01-1.36 and 1.17, 95% CI=0.99-1.38, respectively). Very similar results were found in the 10-year longitudinal analysis [HRs=1.28, 95% CI=1.01-1.61 (β-HCH); 1.26, 95% CI=1.00-1.59 (HCB)] and were in line with those obtained using elastic net regression. Finally, when the arithmetic sum of both compounds was used as independent variable, risk estimates increased to OR=1.25, 95% CI=1.03-1.52 and HR=1.32, 95% CI=1.02-1.70. Our results suggest that historical exposure to HCB and β-HCH is consistently associated with the risk of metabolic disorders, and that these POPs might be partly responsible for the morbidity risk traditionally attributed to age and obesity.