Do phthalates act as obesogens in humans? A systematic review of the epidemiological literature

Evidence of the Possible Harm of Endocrine-Disrupting Chemicals in Humans: Ongoing Debates and Key Issues

Evidence has emerged that endocrine-disrupting chemicals (EDCs) can produce adverse effects, even at low doses that are assumed safe. However, systemic reviews and meta-analyses focusing on human studies, especially of EDCs with short half-lives, have demonstrated inconsistent results. Epidemiological studies have insuperable methodological limitations, including the unpredictable net effects of mixtures, non-monotonic dose-response relationships, the non-existence of unexposed groups, and the low reliability of exposure assessment. Thus, despite increases in EDC-linked diseases, traditional epidemiological studies based on individual measurements of EDCs in bio-specimens may fail to provide consistent results. The exposome has been suggested as a promising approach to address the uncertainties surrounding human studies, but it is never free from these methodological issues. Although exposure to EDCs during critical developmental periods is a major concern, continuous exposure to EDCs during non-critical periods is also harmful. Indeed, the evolutionary aspects of epigenetic programming triggered by EDCs during development should be considered because it is a key mechanism for developmental plasticity. Presently, living without EDCs is impossible due to their omnipresence. Importantly, there are lifestyles which can increase the excretion of EDCs or mitigate their harmful effects through the activation of mitohormesis or xenohormesis. Effectiveness of lifestyle interventions should be evaluated as practical ways against EDCs in the real world.

Bisphenol a increases risk for presumed non-alcoholic fatty liver disease in Hispanic adolescents in NHANES 2003-2010

BACKGROUND

Bisphenol-A (BPA) is a ubiquitous chemical and recognized endocrine disruptor associated with obesity and related disorders. We explored the association between BPA levels and suspected non-alcoholic fatty liver disease (NAFLD).

METHODS

Unweighted analyses were used to study the relationship between urinary BPA levels and suspected NAFLD (alanine aminotransferase (ALT). > 30 U/L, body mass index (BMI) Z-score > 1.064 and evidence of insulin resistance) using National Health and Nutrition Examination Survey (NHANES) data (2003-2010) on 12-19 year olds. Unweighted and weighted analyses were used to evaluate the risk with only elevated ALT.

RESULTS

We included 944 adolescents with urinary BPA and fasting laboratory tests from a total of 7168 adolescents. Risk of suspected NAFLD was increased in the second quartile of BPA levels (1.4-2.7 ng/mL) when compared to the first (< 1.4 ng/mL) (Odds Ratio (OR) 4.23, 95% Confidence Interval (CI) 1.44-12.41). The ORs for the third and second quartiles were positive but did not reach statistical significance. The association was stronger in Hispanics (n = 344) with BPA levels in the second (OR 6.12, 95% C.I. 1.62-23.15) quartile and when limiting the analyses to overweight/obese adolescents (n = 332), in the second (OR 5.56, 95% C.I. 1.28-24.06) and fourth BPA quartiles (OR 6.85, 95% C.I. 1.02-46.22) compared to the first quartile. BPA levels were not associated with ALT elevation.

CONCLUSIONS

The risk of suspected NAFLD is increased in participants in higher quartiles of BPA exposure, particularly in those of Hispanic ethnicity. Further studies are required to fully understand the potential role of BPA in non-alcoholic fatty liver disease.

The associations between phthalate exposure and insulin resistance, β-cell function and blood glucose control in a population-based sample

In developed countries, phthalate exposure is ubiquitous. Previous studies have shown an association between phthalate levels and health effects. To test associations between phthalate exposures, estimated from urinary phthalate metabolites, and insulin resistance, β-cell function and glucose control. Data were obtained from a cross-sectional, nationally representative study; the Canadian Health Measures Survey (CHMS, 2009-2011). Participants under the age of 12, those with diabetes, who were pregnant or who had not fasted overnight were excluded. Fasting blood glucose, insulin, and glycosylated hemoglobin (HbA_1C) levels were measured in a subset of participants, and urine was collected for creatinine and phthalate metabolites. We tested associations between these variables using linear regression analysis. Of 4437 participants (12-79years old), 2119 had fasting glucose measurements and at least one phthalate metabolite above detection limits. MBzP, MCPP, MEHP, MEHHP, MiBP, and the sum of DEHP metabolites were positively associated with increased HbA_1C (p<0.05). DEHP metabolites were positively associated with increased fasting glucose, insulin, HOMA-IR and HOMA-β. An interquartile increase in the sum of log transformed DEHP metabolites was associated with increases in HOMA-IR and HOMA-β of 0.15 (95% CI 0.04, 0.26) and 10.24 (95% CI 3.71, 16.77) respectively. Increased concentrations of all measured phthalate metabolites were associated with reduced blood glucose control. DEHP metabolites were also associated with increased glucose concentrations, and indicators of β-cell function and insulin resistance. Our results suggest that exposure to phthalates may possibly impair control of blood glucose and thereby predispose to pre-diabetes.

Potential influence of the phthalates on normal liver function and cardiometabolic risk in males

Phthalates are ubiquitous environmental contaminants, massively used in industry as plasticizers and additives in cosmetics, which may impair the human endocrine system inducing fertility problems, respiratory diseases, obesity, and neuropsychological disorders. The aim of this study was to examine the influence of the monoethyl phthalate (MEP) and mono-(2-ethylhexyl) phthalate (MEHP) on the liver function and cardiometabolic risk factors in males. In this research, 102 male participants (51 normal weight and 51 overweight/obese) were enrolled and examined for phthalate metabolites exposure in urine samples after 12 h of fasting. MEP was found in 28.43% (29/102) volunteers, while MEHP was detected among 20.59% (21/102) participants. Statistically significant increment in transaminase serum levels was observed in MEP-positive normal weight subgroup. Linear correlation was obtained between MEP concentration in urine samples and triglyceride (TG) serum levels (r ² = 0.33; p < 0.01), visceral adiposity index (VAI) (r ² = 0.41; p < 0.01), lipid accumulation product (LAP) (r ² = 0.32; p < 0.01), and TG to high-density lipoprotein (HDL) ratio (r ² = 0.40, p < 0.01) among the obese. The MEHP-positive normal weight volunteers had statistically significant increment of body mass index (p = 0.03) compared to MEHP-negative participants. Urine MEHP concentrations were negatively correlated with HDL serum levels (r ² = 0.31; p < 0.05) in the normal weight subgroup. The phthalates exposure may be related to statistically significant ALT and AST serum levels increment as well as with increased BMI, while the phthalate levels in the urine may be correlated with increased TG and decreased HDL cholesterol serum levels and associated with indicators of cardiometabolic risk and insulin resistance as LAP and VAI.

The association between total phthalate concentration and non-communicable diseases and chronic inflammation in South Australian urban dwelling men

OBJECTIVE

To investigate associations between urinary total phthalate concentration, chronic low-grade inflammation and non-communicable diseases in a cohort of South Australian men.

METHODS

1504 men aged 39-84 years who provided a urinary sample at the follow-up visit of the Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) study, a randomly-selected group of urban-dwelling, community-based men from Adelaide, Australia (n = 2038; study participation rate: 78.1%). Total phthalate concentration was quantified in fasting morning urine samples. Chronic diseases were assessed through self-report questionnaire or directly measured using standardised clinical and laboratory procedures. Inflammatory biomarkers were assayed by ELISA or spectroscopy. Multivariable linear and logistic regression models were applied to determine associations of log-transformed urinary phthalate concentration with inflammation and chronic disease.

RESULTS

Total phthalates were detected in 99.6% of urinary samples; geometric mean (95% CI) was 114.1 (109.5-118.9)µg/g creatinine. Higher total phthalate levels were associated with higher levels of hs-CRP, IL-6 (all p < 0.05) and TNF-α but not MPO. Urinary total phthalate concentrations were positively associated with cardiovascular disease, type-2-diabetes and hypertension. Comparing extreme quartiles of total phthalate, prevalence ratios were 1.78 (95% CI 1.17 - 2.71, p-trend = 0.001) for cardiovascular disease and 1.84 (95%CI 1.34 - 2.51, p-trend = 0.001) for type-2-diabetes and 1.14 (95%CI 1.01 - 1.29, p-trend = 0.013) for hypertension. Total phthalates and asthma and depression were not significantly associated.

CONCLUSION

A positive association between total phthalates and cardiovascular disease, type-2-diabetes, hypertension and increased levels of chronic low-grade inflammatory biomarkers was observed in urban-dwelling Australian men.

Emerging exposures of developmental toxicants

PURPOSE OF REVIEW

The purpose of this review is to identify emerging developmental toxicants that are understudied in children's health. Exposures may arise from new products designed to improve utility, to reduce toxicity, or to replace undesirable chemicals. Exposures to less-toxic chemicals may also be significant if they are very commonly used, thereby generating widespread exposure. Sources of exposure include the workplace, personal, home, and office products; food, water, and air.

RECENT FINDINGS

We describe eight exposure categories that contain numerous potential developmental toxicants. References are discussed if reported in PubMed during the past decade at least 10 times more frequently than in 1990-2000. Examples included phthalates, phenols, sunscreens, pesticides, halogenated flame retardants, perfluoroalkyl coatings, nanoparticles, e-cigarettes, and dietary polyphenols. Replacements are often close structural homologs of their precursors. We suggest biomonitoring as preferred means of exposure assessment to emerging chemicals. Some existing analytic methods would require minimal modification to measure these exposures, but others require toxicokinetic and analytic investigation.

SUMMARY

A deliberate strategy for biomonitoring of emerging replacement chemicals is warranted, especially in view of concerns regarding developmental toxicity. To prevent adverse health effects, it is important to characterize such exposures before they become widely disseminated.

Review of reviews on exposures to synthetic organic chemicals and children's neurodevelopment: Methodological and interpretation challenges

Environmental epidemiology data are becoming increasingly important in public health decision making, which commonly incorporates a systematic review of multiple studies. This review addresses two fundamental questions: What is the quality of available reviews on associations between exposure to synthetic organic chemicals and neurodevelopmental outcomes? What is the value (e.g., quality and consistency) of the underlying literature? Published reviews on associations between synthetic organic environmental chemical exposures and neurodevelopmental outcomes in children were systematically evaluated. Seventy-four relevant reviews were identified, and these were evaluated with respect to four methodological characteristics: (1) systematic inclusion/exclusion criteria and reproducible methods for search and retrieval of studies; (2) structured evaluation of underlying data quality; (3) systematic assessment of consistency across specific exposure-outcome associations; and (4) evaluation of reporting/publication bias. None of the 74 reviews fully met the criteria for all four methodological characteristics. Only four reviews met two criteria, and six reviews fulfilled only one criterion. Perhaps more importantly, the higher quality reviews were not able to meet all of the criteria owing to the shortcomings of underlying studies, which lacked comparability in terms of specific research question of interest, overall design, exposure assessment, outcome ascertainment, and analytic methods. Thus, even the most thoughtful and rigorous review may be of limited value if the underlying literature includes investigations that address different hypotheses and are beset by methodological inconsistencies and limitations. Issues identified in this review of reviews illustrate considerable challenges that are facing assessments of epidemiological evidence.

Prenatal phthalate exposure and 8-isoprostane among Mexican-American children with high prevalence of obesity

Oxidative stress has been linked to many obesity-related conditions among children including cardiovascular disease, diabetes mellitus and hypertension. Exposure to environmental chemicals such as phthalates, ubiquitously found in humans, may also generate reactive oxygen species and subsequent oxidative stress. We examined longitudinal changes of 8-isoprostane urinary concentrations, a validated biomarker of oxidative stress, and associations with maternal prenatal urinary concentrations of phthalate metabolites for 258 children at 5, 9 and 14 years of age participating in a birth cohort residing in an agricultural area in California. Phthalates are endocrine disruptors, and in utero exposure has been also linked to altered lipid metabolism, as well as adverse birth and neurodevelopmental outcomes. We found that median creatinine-corrected 8-isoprostane concentrations remained constant across all age groups and did not differ by sex. Total cholesterol, systolic and diastolic blood pressure were positively associated with 8-isoprostane in 14-year-old children. No associations were observed between 8-isoprostane and body mass index (BMI), BMI Z-score or waist circumference at any age. Concentrations of three metabolites of high molecular weight phthalates measured at 13 weeks of gestation (monobenzyl, monocarboxyoctyl and monocarboxynonyl phthalates) were negatively associated with 8-isoprostane concentrations among 9-year olds. However, at 14 years of age, isoprostane concentrations were positively associated with two other metabolites (mono(2-ethylhexyl) and mono(2-ethyl-5-carboxypentyl) phthalates) measured in early pregnancy. Longitudinal data on 8-isoprostane in this pediatric population with a high prevalence of obesity provides new insight on certain potential cardiometabolic risks of prenatal exposure to phthalates.

Pregnancy urinary phthalate metabolite concentrations and gestational diabetes risk factors

BACKGROUND

Epidemiologic studies suggest phthalate metabolite concentrations are associated with type 2 diabetes. GDM is a strong risk factor for type 2 diabetes. Little is known about phthalates and GDM risk factors (i.e. 1st trimester body mass index (BMI), gestational weight gain (GWG), and 2nd trimester glucose levels).

METHODS

A total of 350 women participating in Lifecodes pregnancy cohort (Boston, MA), delivered at term and had pregnancy urinary phthalate metabolite concentrations. Nine specific gravity-adjusted urinary phthalate metabolites were evaluated. General linear regression was used to assess associations between quartiles of phthalate metabolites and continuous 1st trimester BMI and late 2nd trimester blood glucose. Linear mixed models were used for total GWG. Multivariable logistic regression was used for phthalate concentrations and categorized GWG and impaired glucose tolerance defined as glucose≥140mg/dL based on a 50-gram glucose load test. Models were adjusted for potential confounders.

RESULTS

There were no associations between 1st trimester urinary phthalate metabolite concentrations and 1st trimester BMI. Mono-ethyl phthalate concentrations averaged across pregnancy were associated with a 2.17 increased odds of excessive GWG (95% CI: 0.98, 4.79). Second trimester mono-ethyl phthalate was associated with increased odds of impaired glucose tolerance (adj. OR: 7.18; 95% CI: 1.97, 26.15). A summary measure of di-2-ethylhexyl phthalate metabolite concentrations were inversely associated with impaired glucose tolerance (adj. OR: 0.25; adj. 95% CI: 0.08, 0.85).

CONCLUSIONS

Higher exposure to mono-ethyl phthalate, a metabolite of the parent compound of di-ethyl phthalate, may be associated with excessive GWG and impaired glucose tolerance; higher di-2-ethylhexyl phthalate was associated with reduced odds of impaired glucose tolerance.

Human exposure to endocrine disrupting compounds: Their role in reproductive systems, metabolic syndrome and breast cancer. A review

Endocrine disrupting chemicals (EDCs) are released into the environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDCs have major risks for humans by targeting different organs and systems in the body (e.g. reproductive system, breast tissue, adipose tissue, pancreas, etc.). Due to the ubiquity of human exposure to these compounds the aim of this review is to describe the most recent data on the effects induced by phthalates, bisphenol A and parabens in a critical window of exposure: in utero, during pregnancy, infants, and children. The interactions and mechanisms of toxicity of EDCs in relation to human general health problems, especially those broadening the term of endocrine disruption to 'metabolic disruption', should be deeply investigated. These include endocrine disturbances, with particular reference to reproductive problems and breast, testicular and ovarian cancers, and metabolic diseases such as obesity or diabetes.

Infectious and Environmental Influences on the Obesity Epidemic

Over the last two decades, the prevalence of obesity has increased rapidly. While it is intuitively appealing to believe that the causes of obesity are manifestly related to excess dietary intake, combined with a reduced expenditure of energy via a decrease in physical activity, it is also been noted that the evidence for these as the sole causes of the obesity epidemic is incomplete. This has led to the search for other causes of obesity, particularly those which stem from the environment we live in. This review will explore two putative causes of obesity: infections and environmental pollutants. It will focus on the key human infection associated with obesity-human adenovirus 36 (Ad36) and will discuss several environmental pollutants which have been postulated to be involved in the development of obesity: bisphenol A, phthalates and persistent organic pollutants. For each of these, the epidemiology and biological mechanisms underpinning the association of these agents with obesity will be reviewed.

Benzyl butyl phthalate induces epigenetic stress to enhance adipogenesis in mesenchymal stem cells

Endocrine disruptors, phthalates, may have contributed to recent global obesity health crisis. Our study investigated the potential of benzyl butyl phthalate (BBP) to regulate the mesenchymal stem cell epigenome to drive adipogenesis. BBP exposure enhanced lipid accumulation and adipogenesis in a dose-dependent manner compared to control (P < 0.001). Adipogenesis markers, PPARγ (P < 0.001), C/EBPα (P < 0.01), and aP2 (P < 0.001) were significantly upregulated by increasing concentrations of BBP when compared to DMSO. BBP enhanced H3K9 acetylation while decreasing H3K9 dimethylation. Fifty μM BBP increased histone acetyltransferases, p300 (P < 0.05) and GCN5 (P < 0.01) gene expression. Furthermore, histone deacetylases (HDACs), HDAC3 (P < 0.01) and HDAC10 (P < 0.01, 10 μM BBP; P < 0.001, 50 μM BBP) and histone methyltransferases, SETDB1 (P < 0.01) and G9a (P < 0.01), were significantly downregulated by BBP exposure. BBP acts, in part, through PPARγ, as PPARγ knockdown led to decreased H3K9ac and rescued H3K9me2 during BBP exposure. In conclusion, BBP regulated MSCs towards adipogenesis by tipping the epigenomic balance.

Phthalates in neonatal health: friend or foe?

Exposure to environmental chemicals has adverse effects on the health and survival of humans. Emerging evidence supports the idea that exposure to endocrine-disrupting compounds (EDCs) can perturb an individual’s physiological set point and as a result increase his/her propensity toward several diseases. The purpose of this review is to provide an update on di-(2-ethylhexyl) phthalate, the primary plasticizer found in plastic medical devices used in neonatal intensive care units, its effects on the fetus and newborn, epidemiological studies, pharmacokinetics, toxicity and epigenetic implications. We searched the PubMed databases to identify relevant studies. Phthalates are known EDCs that primarily are used to improve the flexibility of polyvinyl chloride plastic products and are called plasticizers in lay terms. Neonates and infants are particularly vulnerable to the effects of phthalates, beginning with maternal exposure and placental transfer during gestation and during infancy following birth. In line with the developmental origins of adult disease, a focus on the effects of environmental chemicals in utero or early childhood on the genesis of adult diseases through epigenome modulation is timely and important. The epigenetic effects of phthalates have not been fully elucidated, but accumulating evidence suggests that they may be associated with adverse health effects, some of which may be heritable. Phthalate exposure during pregnancy and the perinatal period is particularly worrisome in health-care settings. Although the clinical significance of phthalate exposure has been difficult to assess with epidemiologic studies, the evidence that physiological changes occur due to exposure to phthalates is growing and points toward the need for more investigation at a molecular, specifically epigenetic level.

Longitudinal Associations of Phthalate Exposures During Childhood and Body Size Measurements in Young Girls

BACKGROUND

Phthalates are environmental chemicals that may play a role in the development of obesity. Few studies have investigated longitudinal associations between postnatal phthalate exposures and subsequent anthropometric measurements in children.

METHODS

We collected data as part of The Breast Cancer and Environment Research Program at three US sites. A total of 1,239 girls, aged 6-8 years, were enrolled in 2004-2007. We categorized baseline phthalate exposures, assessed from creatinine-corrected urinary concentrations of low-molecular weight phthalate metabolites, as low, <78; medium, 78 to <194; and high, ≥194 μg/g creatinine and of high-molecular weight phthalates as low, <111; medium, 111-278; and high, ≥278 μg/g creatinine. Anthropometric measurements were collected through 2012 (n = 1,017). Linear mixed effects regression estimated how baseline low and high-molecular weight phthalate concentrations related to changes in girls' body mass index (BMI), height, and waist circumference at ages 7-13 years.

RESULTS

Low-molecular weight phthalates were positively associated with gains in BMI and waist circumference. Predicted differences in BMI and waist circumference between girls with high versus low concentrations of low-molecular weight phthalates increased from 0.56 (95% confidence interval [CI]: -0.02, 1.1) to 1.2 kg/m (95% CI: 0.28, 2.1) and from 1.5 (95% CI: -0.38, 3.3) to 3.9 cm (95% CI: 1.3, 6.5), respectively. High-molecular weight phthalates were negatively associated with height but only among girls who were normal weight at baseline (BMI ≤ 85th percentile).

CONCLUSION

Phthalates, specifically low-molecular weight phthalates, have small but detectable associations with girls' anthropometric outcomes. Low-molecular weight phthalates showed stronger associations than other types of phthalates.

Environmental pollutants and child health-A review of recent concerns

In recent years, many new studies have evaluated associations between environmental pollutants and child health. This review aims to provide a broad summary of this literature, comparing the state of epidemiological evidence for the effects of a wide range of environmental contaminants (air pollutants, heavy metals, organochlorine compounds, perfluoroalkyl substances, polybrominated diphenyl ethers, pesticides, phthalates and bisphenol A) on child health outcomes. The review addresses effects on foetal growth and prematurity, neurodevelopment, respiratory and immune health, and childhood growth and obesity. Findings of recent prospective studies and meta-analyses have corroborated previous good evidence, often at lower exposure levels, for effects on foetal growth of air pollution and polychlorinated biphenyls (PCBs), for neurotoxic effects of lead, methylmercury, PCBs and organophosphate pesticides, and for respiratory health effects of air pollution. Moderate evidence has emerged for a potential role of environmental pollutants in attention deficit hyperactivity disorder and autism (lead, PCBs, air pollution), respiratory and immune health (dichlorodiphenyldichloroethylene - DDE - and PCBs), and obesity (DDE). In addition, there is now moderate evidence that certain chemicals of relatively recent concern may be associated with adverse child health outcomes, specifically perfluorooctanoate and foetal growth, and polybrominated diphenyl ethers and neurodevelopment. For other chemicals of recent concern, such as phthalates and bisphenol A, the literature is characterised by large inconsistencies preventing strong conclusions. In conclusion, since most of the recent literature evaluates common exposures in the general population, and not particularly high exposure situations, this accumulating body of evidence suggests that the unborn and young child require more protection than is currently provided. Large, coordinated research efforts are needed to improve understanding of long-term effects of complex chemical mixtures.

Prenatal Phthalate Exposures and Childhood Fat Mass in a New York City Cohort

BACKGROUND

Experimental animal studies and limited epidemiologic evidence suggest that prenatal exposure to phthalates may be obesogenic, with potential sex-specific effects of phthalates having anti-androgenic activity.

OBJECTIVES

We aimed to assess associations between prenatal phthalate exposures and childhood fat mass in a prospective cohort study.

METHODS

We measured phthalate metabolite concentrations in third-trimester maternal urine in a cohort of women enrolled in New York City between 1998 and 2002 (n = 404). Among 180 children (82 girls and 98 boys), we evaluated body composition using a Tanita scale at multiple follow-up visits between ages 4 and 9 years (363 total visits). We estimated associations of standard deviation differences or tertiles of natural log phthalate metabolite concentrations with percent fat mass using linear mixed-effects regression models with random intercepts for repeated outcome measurements. We assessed associations in multiple metabolite models and adjusted for covariates including prepregnancy body mass index, gestational weight gain, maternal smoking during pregnancy, and breastfeeding.

RESULTS

We did not observe associations between maternal urinary phthalate concentrations and percent body fat in models examining continuous exposures. Fat mass was 3.06% (95% CI: -5.99, -0.09%) lower among children in the highest tertile of maternal urinary concentrations of summed di(2-ethylhexyl) phthalate (ΣDEHP) metabolites than in children in the lowest tertile. Though estimates were imprecise, there was little evidence that associations between maternal urinary phthalate concentrations and percent fat mass were modified by child's sex.

CONCLUSIONS

Prenatal phthalate exposures were not associated with increased body fat among children 4-9 years of age, though high prenatal DEHP exposure may be associated with lower fat mass in childhood.

CITATION

Buckley JP, Engel SM, Mendez MA, Richardson DB, Daniels JL, Calafat AM, Wolff MS, Herring AH. 2016. Prenatal phthalate exposures and childhood fat mass in a New York City cohort. Environ Health Perspect 124:507-513; http://dx.doi.org/10.1289/ehp.1509788.

Associations between bone mineral density and urinary phthalate metabolites among post-menopausal women: a cross-sectional study of NHANES data 2005-2010

Bone mineral density (BMD) decreases with age, especially among post-menopausal women. Exposures to endocrine disruptors, such as phthalate diesters, could alter BMD through a variety of unidentified mechanisms. A hypothesis-generating study investigated associations between urinary phthalate metabolites and BMD at the femoral neck and spine in post-menopausal women (n = 480) participating in the National Health and Nutrition Examination Survey, from 2005 to 2010. Mono-ethyl phthalate (MEP), molar sum of low molecular weight metabolites (mono-n-butyl phthalate (MNBP), mono-isobutyl phthalate (MIBP), MEP), molar sum of estrogenic metabolites (MNBP, MIBP, MEP, mono-benzyl phthalate (MBZP)), and an estrogenic equivalency factor were negatively associated with spinal BMD. Some associations were modified by age or BMI. The cross-sectional study design, uncertainty regarding the critical time window of exposure, the potential for exposure misclassification, and residual confounding limit our abilities to draw causal conclusions regarding phthalate metabolites and BMD in post-menopausal women. Future studies should address these limitations.

Temporal trends in bisphenol A exposure in the United States from 2003-2012 and factors associated with BPA exposure: Spot samples and urine dilution complicate data interpretation

Nationally representative data on urinary levels of BPA and its metabolites in the United States from the 2003-2004 to 2011-2012 National Health and Nutrition Examination Surveys (NHANES) were used to estimate daily BPA intakes and examine temporal trends. Additionally, NHANES data on lifestyle/demographic/dietary factors previously reported to be associated with BPA exposures were examined to assess the resiliency of the reported associations (whether the association is maintained across the five surveys). Finally, various approaches for addressing issues with the use of BPA concentration data from spot urine samples were examined for their effect on trends and associations. Three approaches were assessed here: (i) use of generic literature-based 24-h urine excretion volumes, (ii) use of creatinine adjustments, and (iii) use of individual urine flow rate data from NHANES. Based on 2011-2012 NHANES urinary BPA data and assumptions described in this paper, the median daily intake for the overall population is approximately 25 ng/kg day; median intake estimates were approximately two to three orders of magnitude below current health-based guidance values. Estimates of daily BPA intake have decreased significantly compared to those from the 2003-2004 NHANES. Estimates of associations between lifestyle/demographic/dietary factors and BPA exposure revealed inconsistencies related to both NHANES survey year and the three approaches listed above; these results demonstrate the difficulties in interpreting urinary BPA data, despite efforts to account for urine dilution and translation of spot sample data to 24-h data. The results further underscore the importance of continued research on how to best utilize urinary measures of environmental chemicals in exposure research. Until a consensus is achieved regarding the best biomonitoring approaches for assessing exposures to short-lived chemicals using urine samples, research on factors associated with BPA exposures should include - and report results from - assessments using both volume-based urinary BPA and creatinine-adjusted urinary BPA data.

Levels of Phthalate Metabolites in Urine of Pregnant Women and Risk of Clinical Pregnancy Loss

Toxicological studies have shown that phthalate esters (PAEs), a class of widely used and environmentally prevalent chemicals, can increase the abortion rate in animals, but epidemiological evidence is scarce. This study aimed to explore the relationship between the urinary concentration of phthalate metabolites and the risk of clinical pregnancy loss. A total of 132 women who underwent clinical pregnancy loss (cases) and 172 healthy pregnant women (controls) were recruited from Beijing, China. Eight phthalate metabolites in urine were determined by ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Five phthalate metabolites, monomethyl phthalate (MMP), monoethyl phthalate (MEP), monoisobutyl phthalate (MiBP), mono-n-butyl phthalate (MnBP), and mono(2-ethlyhexyl) phthalate (MEHP), were detected in at least 95% of the urine samples, with the highest median concentration of 51.0 μg/g of creatinine for MnBP of all participants. The differences in urinary concentrations of phthalate metabolites between cases and controls were evaluated using the Mann-Whitney U test. The concentrations of MEP (median of 18.7 μg/g of creatinine), MiBP (23.3 μg/g of creatinine), and MnBP (58.2 μg/g of creatinine) detected in the cases were significantly higher than those (15.7 μg/g of creatinine for MEP, 19.4 μg/g of creatinine for MiBP, and 43.9 μg/g of creatinine for MnBP) in the controls (p < 0.05). Increasing risks of clinical pregnancy loss were observed from the first to fourth quartiles of the MEP, MiBP, and MnBP concentrations (p < 0.05 for trend). We concluded that exposure to MEP, MiBP, and MnBP was associated with an increased risk of clinical pregnancy loss.

Lessons learned from the application of BEES-C: Systematic assessment of study quality of epidemiologic research on BPA, neurodevelopment, and respiratory health

Epidemiologic studies evaluating associations between biomarkers of exposure to short-lived chemicals and health endpoints in humans face special challenges. Perhaps the most critical challenges are the need to determine the type and optimal number of samples, and the proper timing of specimen collection. Further, as many short-lived chemicals are ubiquitous in the environment, utmost care is required to avoid sample contamination. A separate set of challenges is associated with appropriate interpretation and reporting of results from multiple simultaneous analyses, which are becoming increasingly feasible. The Biomonitoring, Environmental Epidemiology, and Short-Lived Chemicals (BEES-C) instrument is specifically designed to evaluate the quality of epidemiologic studies that measure biomarkers of chemicals with short physiologic half-lives. The instrument provides systematic guidance for evaluating 14 different aspects of study quality divided into three broad categories: 1) biomarker selection and measurement, 2) strategy and execution of exposure assessment, and 3) general considerations of study design and reporting. We evaluated the utility of the BEES-C instrument using epidemiologic studies of exposure to bisphenol A and its association with neurodevelopmental and respiratory health indicators. Each BEES-C element was assessed with respect to needed modifications and concordance among reviewers using professional, scientific judgment. Based on this first use of the BEES-C instrument, we found that most of its elements were effective in comparing the quality of available studies, with reviews generally concordant and justifications consistent. However, we note that certain elements would be improved with slight adjustments and that one of the elements appeared redundant and should be removed.

The association of socio-demographic status, lifestyle factors and dietary patterns with total urinary phthalates in Australian men

OBJECTIVE

To investigate the associations between socio-demographic status, lifestyle factors, dietary patterns and urinary total phthalate concentration in a cohort of South Australian men.

METHOD

We randomly selected 1527 males aged 39 to 84 from wave two of the Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) study. Total phthalate concentration was examined in fasting morning urine samples. Socio-demographic and lifestyle factors were assessed by questionnaire. Food intake was assessed by food frequency questionnaire (FFQ). Dietary patterns were constructed using factor analysis.

RESULTS

Total phthalates were detected in 99.6% of the urine samples. The overall geometric mean (95% CI) of total phthalate concentration was 112.4 (107.5-117.5) ng/mL. The least square geometric means (LSGMs) of total phthalate concentration were significantly higher among people who were obese (127.8 ng/mL), consuming less than two serves fruit per day (125.7 ng/mL) and drinking more than one can (375mL) of carbonated soft drink per day (131.9 ng/mL). Two dietary patterns were identified: a prudent dietary pattern and a western dietary pattern. Both the western dietary pattern (p = 0.002) and multiple lifestyle risk factors including smoking, obesity, insufficient physical activity and the highest quartile of the western dietary pattern (p<0.001), were positively associated with total phthalate levels. There was no significant relationship between total phthalate concentration and socio-demographic status.

CONCLUSION

Phthalate exposure is ubiquitous and positively associated with lifestyle risk factors in urban dwelling Australian men.

Associations of urinary phthalates with body mass index, waist circumference and serum lipids among females: National Health and Nutrition Examination Survey 1999-2004

BACKGROUND/OBJECTIVES

Exposure to environmental chemicals could be one of the contributors to the increasing obesity epidemic. Very little is known about the association of phthalates, ubiquitous chemicals widely used in consumer products, with obesity and lipid metabolism. This study investigated the association of urinary phthalate metabolites and, for the first time, the ratios of the major metabolites of the most common phthalate, di-2-ethylhexyl phthalate, with body mass index (BMI), waist circumference and serum lipid levels in the US female population.

METHODS

This cross-sectional study used the data from the National Health and Nutrition Examination Survey, 1999-2004 and was restricted to women aged ⩾18 years, who were not pregnant and had no history of diabetes. Using multivariate ordered logistic regression, we examined associations of seven urinary phthalate metabolites and their metabolic ratios with the BMI, waist circumferences, total cholesterol, triglycerides and high- and low-density lipoprotein cholesterol.

RESULTS

BMI was positively associated with monobutyl phthalate (MBP) and mono-2-ethylhexyl phthalate (MEHP) (odds ratio (OR)=1.13; 95% confidence interval (CI), 1.03-1.23 and OR=1.12; 95% CI, 1.03-1.23, respectively). Waist circumference was positively associated with MBP (OR=1.13; 95% CI, 1.03-1.24). A higher ratio of MEHP to mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) was positively associated with both BMI (OR=1.21; 95% CI, 1.09-1.34) and waist circumference (OR=1.20; 95% CI, 1.10-1.31). There were no other significant associations.

CONCLUSIONS

A higher metabolic ratio of MEHP to MEHHP, reflective of slower oxidative conversion of MEHP, is associated with greater BMI and waist circumference.

Improving Concordance in Environmental Epidemiology: A Three-Part Proposal

In observational research, evidence is usually derived from multiple studies, and any single result is rarely considered sufficient for public health decision making. Despite more than five decades of research and thousands of studies published, the ability to draw robust conclusions regarding the presence or absence of causal links between specific environmental exposures and human health remains limited. To develop policies that are protective of public health and can withstand scrutiny, agencies need to rely on investigations of satisfactory quality that follow sufficiently concordant protocols in terms of exposure assessment, outcome ascertainment, data analysis, and reporting of results. Absent such concordance, the ability of environmental epidemiology studies to inform decision making is greatly diminished. Systems and tools are proposed here to improve concordance among environmental epidemiology studies. Specifically, working systems in place in other fields of research are critically examined and used as guidelines to develop analogous policies and procedures for environmental epidemiology. A three-part path forward toward more concordant, transparent, and readily accessible environmental epidemiology evidence that parallels ongoing efforts in medical research is proposed. The three parts address methods for improving quality and accessibility of systematic reviews, access to information on ongoing and completed studies, and principles for reporting. The goals are to increase the value of epidemiological research in public health decision making and to stimulate discussions around solutions proposed herein.

Metabolic syndrome and the environmental pollutants from mitochondrial perspectives

The worldwide epidemic of diabetes and metabolic syndrome in the last few decades cannot be fully accounted for only by changes in the lifestyle factors, such as sedentary lifestyle and overeating. Besides genetic factors, there must be other causes to explain this rapid change. They could not be infectious in nature and induce insulin resistance as key biochemical abnormality. Mitochondrial dysfunction could be underlying mechanism behind the insulin resistance, thus metabolic syndrome. Then there have been increasing number of reports suggesting that chronic exposure to and accumulation of endocrine disrupting chemicals (EDCs), especially so-called the persistent organic pollutants (POPs) within the body might be associated with metabolic syndrome. Combining two concepts, we developed new "EDCs-induced mitochondrial dysfunction hypothesis of metabolic syndrome". In this review we suggest that classifying those chemicals into 5 groups might be clinically useful considering their removal or avoidance; POPs, non-persistent organic pollutants, heavy metals, air pollutants and drugs. We will also discuss briefly how those insights could be applied to clinical medicine.

A proposal for assessing study quality: Biomonitoring, Environmental Epidemiology, and Short-lived Chemicals (BEES-C) instrument

The quality of exposure assessment is a major determinant of the overall quality of any environmental epidemiology study. The use of biomonitoring as a tool for assessing exposure to ubiquitous chemicals with short physiologic half-lives began relatively recently. These chemicals present several challenges, including their presence in analytical laboratories and sampling equipment, difficulty in establishing temporal order in cross-sectional studies, short- and long-term variability in exposures and biomarker concentrations, and a paucity of information on the number of measurements required for proper exposure classification. To date, the scientific community has not developed a set of systematic guidelines for designing, implementing and interpreting studies of short-lived chemicals that use biomonitoring as the exposure metric or for evaluating the quality of this type of research for WOE assessments or for peer review of grants or publications. We describe key issues that affect epidemiology studies using biomonitoring data on short-lived chemicals and propose a systematic instrument--the Biomonitoring, Environmental Epidemiology, and Short-lived Chemicals (BEES-C) instrument--for evaluating the quality of research proposals and studies that incorporate biomonitoring data on short-lived chemicals. Quality criteria for three areas considered fundamental to the evaluation of epidemiology studies that include biological measurements of short-lived chemicals are described: 1) biomarker selection and measurement, 2) study design and execution, and 3) general epidemiological study design considerations. We recognize that the development of an evaluative tool such as BEES-C is neither simple nor non-controversial. We hope and anticipate that the instrument will initiate further discussion/debate on this topic.

Endocrine disruptors: new players in the pathophysiology of type 2 diabetes?

The prevalence of type 2 diabetes (T2D) has dramatically increased worldwide during the last few decades. While lifestyle factors, such as decreased physical activity and energy-dense diets, together with genetic predisposition, are well-known actors in the pathophysiology of T2D, there is accumulating evidence suggesting that the increased presence of endocrine-disrupting chemicals (EDCs) in the environment, such as bisphenol A, phthalates and persistent organic pollutants, may also explain an important part in the incidence of metabolic diseases (the metabolic syndrome, obesity and T2D). EDCs are found in everyday products (including plastic bottles, metal cans, toys, cosmetics and pesticides) and used in the manufacture of food. They interfere with the synthesis, secretion, transport, activity and elimination of natural hormones. Such interferences can block or mimic hormone actions and thus induce a wide range of adverse effects (developmental, reproductive, neurological, cardiovascular, metabolic and immune). In this review, both in vivo and in vitro experimental data and epidemiological evidence to support an association between EDC exposure and the induction of insulin resistance and/or disruption of pancreatic β-cell function are summarized, while the epidemiological links with disorders of glucose homoeostasis are also discussed.

Obesogenic effects of endocrine disruptors, what do we know from animal and human studies?

BACKGROUND

Hormonal actions and activation of receptors involved in adipogenesis and brain development during the prenatal period may be affected by exposure to certain chemicals. Experimental studies have shown that amongst others polychlorinated biphenyl (PCB)-153 and dichlorodiphenyltrichloroethane (DDT) may have obesogenic effects in prenatally exposed mice.

OBJECTIVE

To provide an overview of five classes of chemicals which have frequently been indicated as potential obesogens, and to discuss the evidence available regarding early life exposure to these compounds and overweight later in life.

METHODS

Pubmed was systematically searched for publications which related early life exposure to endocrine disrupting chemicals (EDCs) to growth parameters later in life. We included 19 studies, which were published from 1995 and onwards.

RESULTS

Both positive and negative associations are observed between early life exposure and weight or height at various ages, including as early as 14 months, as well as until 20 years of age. In none of the included studies negative associations between perinatal exposure to EDCs and body mass index (BMI) were found and in several studies a positive association was observed. Dose-response relations appear to be non-monotonic.

CONCLUSION

For certain EDCs, early life exposure may be associated with weight homeostasis later in life, however not necessarily in an obesogenic direction. More sensitive measures of adiposity as well as long-term follow-up are warranted for future studies.