Age and sex differences in childhood and adulthood obesity association with phthalates: analyses of NHANES 2007-2010

BACKGROUND

Exposure to environmental chemicals may play a role in the development of obesity. Evidence suggests phthalate exposure may be associated with obesity in children and adults.

OBJECTIVE

To examine the association of ten urinary phthalate metabolites mono-n-butyl phthalate (MnBP), mono-ethyl phthalate (MEP), mono-isobutyl phthalate (MiBP), mono-2-ethyl-5-carboxypentyl phthalate (MECPP), mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono-2-ethylhexyl phthalate (MEHP), mono-benzyl phthalate (MBzP), mono-(carboxylnonyl) phthalate (MCNP), and mono-(carboxyoctyl) phthalate (MCOP) grouped by molecular weight of their parent compounds with body weight outcomes in children, adolescent and adult participants in the National Health and Nutrition Examination Survey (NHANES) 2007-2010.

METHODS

We performed multinomial logistic regression to analyze the association between obesity and urinary phthalate metabolite concentrations in children and adolescents and adults.

RESULTS

Low molecular weight (LMW) phthalate metabolites (MnBP, MEP and MiBP) are significantly (p<0.05) associated with higher odds for obesity in male children and adolescents. High molecular weight (HMW) phthalate metabolites (MECPP, MEHHP, MEOHP, MEHP, MBzP, MCNP, and MCOP) and di-2-ethylhexyl phthalate (DEHP) metabolites (MEHHP, MEOHP, MEHP and MECPP) are significantly (p<0.05) associated with higher OR for obesity in all adults. Additionally, DEHP metabolites are significantly associated with obesity in all female adults; whereas DEHP and HMW metabolites are significantly associated with OR for obesity in males 60 years and older.

CONCLUSIONS

We found age and sex differences in the association between urinary phthalate metabolite concentrations and body weight outcomes. Reverse causation cannot be excluded since overweight and obese people will have more fat mass, they may store more phthalates, thus leading to higher excretion concentrations.

Urinary and blood cadmium and lead and kidney function: NHANES 2007-2012

BACKGROUND

Cadmium (Cd) and lead (Pb) are widespread environmental contaminants that are known nephrotoxins. However, their nephrotoxic effects at low-environmental exposure levels are debated.

OBJECTIVE

We examined the association of blood Pb (B-Pb), blood Cd (B-Cd), urinary Pb (U-Pb) and urinary Cd (U-Cd) with estimated glomerular filtration rate (eGFR) and urinary albumin (ALB).

METHODS

We used multivariate linear regression to analyze the association between B-Pb, B-Cd, U-Pb, and U-Cd with eGFR and ALB in adult participants (≥20 years of age) in NHANES 2007-2012. The dataset was limited to NHANES individuals with both blood and urinary metal measurements.

RESULTS

We found a statistically significant inverse association between eGFR and B-Cd and statistically significant positive associations between eGFR and both U-Cd and U-Pb, as well as statistically significant associations between ALB and the 3rd and 4th quartiles of U-Cd.

CONCLUSIONS

The inverse association between eGFR and B-Cd, in conjunction with positive associations between eGFR and ALB with U-Cd, suggest that U-Cd measurement at low levels of exposure may result from changes in renal excretion of Cd due to kidney function and protein excretion. However, renal effects such as hyperfiltration from Cd-mediated kidney damage or creatinine-specific Cd effects cannot be excluded with this cross-sectional design.

Urinary polycyclic aromatic hydrocarbons and childhood obesity: NHANES (2001-2006)

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are known carcinogens and suspected endocrine disruptors. Prenatal exposure to PAHs has been associated with obesity in early childhood.

OBJECTIVE

We examined the association of urinary PAH metabolites with adiposity outcomes [body mass index (BMI) z-score, waist circumference (WC), and rate of obesity] in children and adolescents.

METHODS

We performed whole-sample analyses of 3,189 individuals 6-19 years of age who participated in the 2001-2006 National Health and Nutrition Examination Survey. We performed multivariate linear and logistic regression to analyze the association of BMI z-score, WC, and obesity with concentrations of single urinary PAH compounds and the sum of PAHs. Furthermore, the analyses were stratified by developmental stage [i.e., children (6-11 years) and adolescents (12-19 years)].

RESULTS

BMI z-score, WC, and obesity were positively associated with the molecular mass sum of the PAHs and the total sum of naphthalene metabolites. Most associations increased monotonically with increasing quartiles of exposure among children 6-11 years of age, whereas dose-response trends were less consistent for adolescents (12-19 years of age). Neither total PAHs nor total naphthalene metabolites were associated with overweight in either age group, and there was little evidence of associations between the outcomes and individual PAHs.

CONCLUSIONS

Total urinary PAH metabolites and naphthalene metabolites were associated with higher BMI, WC, and obesity in children 6-11 years of age, with positive but less consistent associations among adolescents.

CITATION

Scinicariello F, Buser MC. 2014. Urinary polycyclic aromatic hydrocarbons and childhood obesity: NHANES (2001-2006). Environ Health Perspect 122:299-303; http://dx.doi.org/10.1289/ehp.1307234.

Serum Testosterone Concentrations and Urinary Bisphenol A, Benzophenone-3, Triclosan, and Paraben Levels in Male and Female Children and Adolescents: NHANES 2011-2012

BACKGROUND

Exposure to environmental phenols (e.g., bisphenol A, benzophenone-3, and triclosan) and parabens is widespread in the population. Many of these chemicals have been shown to have anti-androgenic effects both in vitro and in vivo.

OBJECTIVE

We examined the association of bisphenol A (BPA), benzophenone-3 (BP-3), triclosan (TCS), and parabens with serum total testosterone (TT) levels in child and adolescent participants (ages 6-19 years) in the National Health and Nutrition Examination Survey (NHANES) 2011-2012.

METHODS

We performed multivariable linear regression to estimate associations between natural log-transformed serum TT and quartiles of urinary BPA, BP-3, TCS, and parabens in male and female children (ages 6-11 years) and adolescents (ages 12-19 years).

RESULTS

BP-3 and BPA were associated with significantly lower TT in male adolescents, and BPA was associated with significantly higher TT in female adolescents. TT was not consistently associated with TCS or total parabens in children or adolescents of either sex.

CONCLUSIONS

To our knowledge, this is the first study to report an association of both BP-3 and BPA with serum TT in adolescents. Associations between BPA and TT differed according to sex in adolescents, with inverse associations in boys and positive associations in girls. BP-3 was associated with significantly lower TT in adolescent boys only. However, because of the limitations inherent to the cross-sectional study design, further studies are needed to confirm and elucidate on our findings. Citation: Scinicariello F, Buser MC. 2016. Serum testosterone concentrations and urinary bisphenol A, benzophenone-3, triclosan, and paraben levels in male and female children and adolescents: NHANES 2011-2012. Environ Health Perspect 124:1898-1904; http://dx.doi.org/10.1289/EHP150.

Blood lead level association with lower body weight in NHANES 1999-2006

BACKGROUND

Lead exposure is associated with low birth-weight. The objective of this study is to determine whether lead exposure is associated with lower body weight in children, adolescents and adults.

METHODS

We analyzed data from NHANES 1999-2006 for participants aged ≥3 using multiple logistic and multivariate linear regression. Using age- and sex-standardized BMI Z-scores, overweight and obese children (ages 3-19) were classified by BMI ≥85 th and ≥95 th percentiles, respectively. The adult population (age ≥20) was classified as overweight and obese with BMI measures of 25-29.9 and ≥30, respectively. Blood lead level (BLL) was categorized by weighted quartiles.

RESULTS

Multivariate linear regressions revealed a lower BMI Z-score in children and adolescents when the highest lead quartile was compared to the lowest lead quartile (β (SE)=-0.33 (0.07), p<0.001), and a decreased BMI in adults (β (SE)=-2.58 (0.25), p<0.001). Multiple logistic analyses in children and adolescents found a negative association between BLL and the percentage of obese and overweight with BLL in the highest quartile compared to the lowest quartile (OR=0.42, 95% CI: 0.30-0.59; and OR=0.67, 95% CI: 0.52-0.88, respectively). Adults in the highest lead quartile were less likely to be obese (OR=0.42, 95% CI: 0.35-0.50) compared to those in the lowest lead quartile. Further analyses with blood lead as restricted cubic splines, confirmed the dose-relationship between blood lead and body weight outcomes.

CONCLUSIONS

BLLs are associated with lower body mass index and obesity in children, adolescents and adults.

Antimony and sleep-related disorders: NHANES 2005-2008

BACKGROUND

Antimony is used as a flame-retardant in textiles and plastics, in semiconductors, pewter, and as pigments in paints, lacquers, glass and pottery. Subacute or chronic antimony poisoning has been reported to cause sleeplessness. The prevalence of short sleep duration (<7h/night) has been reported to be 37.1% in the general US population, and obstructive sleep apnea (OSA) affects 12-28 million US adults. Insufficient sleep and OSA have been linked to the development of several chronic conditions including diabetes, cardiovascular disease, obesity and depression, conditions that pose serious public health threats.

OBJECTIVE

To investigate whether there is an association between antimony exposure and sleep-related disorders in the US adult population using the National Health and Nutrition Examination Survey (NHANES) 2005-2008.

METHODS

We performed multivariate logistic regression to analyze the association of urinary antimony with several sleep disorders, including insufficient sleep and OSA, in adult (ages 20 years and older) participants of NHANES 2005-2008 (n=2654).

RESULT

We found that participants with higher urinary antimony levels had higher odds to experience insufficient sleep (≤6h/night) (OR 1.73; 95%CI; 1.04, 2.91) as well as higher odds to have increased sleep onset latency (>30min/night). Furthermore, we found that higher urinary antimony levels in participants were associated with OSA (OR 1.57; 95%CI; 1.05, 2.34), sleep problems, and day-time sleepiness.

CONCLUSION

In this study, we found that urinary antimony was associated with higher odds to have insufficient sleep and OSA. Because of the public health implications of sleep disorders, further studies, especially a prospective cohort study, are warranted to evaluate the association between antimony exposure and sleep-related disorders.

DDT/DDE and breast cancer: a meta-analysis

The biological basis for investigating dichlorodiphenyltrichloroethane (DDT) exposure and breast cancer risk stems from in vitro and animal studies indicating that DDT has estrogenic properties. The objective of this study was to update a meta-analysis from 2004 which found no association between dichlorodiphenyldichloroethylene (DDE) and breast cancer. We searched PubMed and Web of Science for studies published through June 2012 assessing DDT/DDE exposure and breast cancer. Summary Odds Ratios (ORs) with 95% confidence intervals (CIs) were calculated for the prevalence of breast cancer in the highest versus the lowest exposed groups for DDT and DDE. Difference of means of exposure for cases versus controls was analyzed for DDT and DDE. From the 500 studies screened, 46 were included in the meta-analysis. Slightly elevated, but not statistically significant summary ORs were found for DDE (1.05; 95% CI: 0.93-1.18) and DDT (1.02; 95% CI: 0.92-1.13). Lipid adjusted difference of means analysis found a significantly higher DDE concentration in cases versus controls (11.30 ng/g lipid; p=0.01). No other difference of means analysis found significant relationships. The existing information does not support the hypothesis that exposure to DDT/DDE increases the risk of breast cancer in humans.

Perfluoroalkyl acids, hyperuricemia and gout in adults: Analyses of NHANES 2009-2014

BACKGROUND

Previous studies have reported a positive association of perfluoralkyl acids (PFAAs), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), with hyperuricemia. The objective of the study is to investigate whether there is an association between concurrent serum levels of several PFAAs and gout, serum uric acid (SUA) or hyperuricemia in the U.S. adult population as represented by the National Health and Nutrition Examination Survey (NHANES) 2009-2014 sample (n = 4917). The PFAAs investigated include PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS) and PFOS.

METHODS

This cross-sectional study used multivariate logistic regressions to analyze the association of single PFAAs with hyperuricemia and self-reported gout; the association with SUA was analyzed by multivariate linear regression. Analyses were adjusted for race/ethnicity, age, sex, education, alcohol consumption, smoking, serum cotinine, BMI, diabetes, hypertension, chronic kidney disease, and SUA (for gout only).

RESULTS

Higher quartile values of serum PFOA and PFHxS were associated with increased odds of self-reported gout. There was a positive association of SUA with increased levels of PFOA, PFNA, PFOS, PFHxS and PFDA. Higher quartile values of PFOA, PFNA, and PFHxS were associated with higher odds of hyperuricemia.

CONCLUSIONS

In this population-based cross-sectional analysis, we found an association between selected PFAAs and self-reported gout. We also confirmed previous reports of an association between several PFAAs and hyperuricemia. Our study suggests that exposure to PFAAs may be a risk factor for hyperuricemia and gout.

Association of urinary phenols with increased body weight measures and obesity in children and adolescents

OBJECTIVE

To examine the association of urinary levels of the environmental phenol pesticides 2,5-dichlorophenol, 2,4-dichlorophenol, and triclosan with body weight outcomes in children and adolescent participants in the National Health and Nutrition Examination Survey 2007-2010.

STUDY DESIGN

We performed multivariate linear and multinomial logistic regressions to analyze the association of body mass index (BMI) z-score, waist circumference (WC), and obesity with urinary pesticide concentration in children and adolescents.

RESULTS

After adjustment for covariates, we found a statistically significant positive association (P < .05) between both 2,5-dichlorophenol and 2,4-dichlorophenol with BMI z-score, WC, and obesity in children and adolescents. After stratification by age, the significant associations remained only in adolescents (ages 12-19). No associations were found between triclosan and any of the body weight outcomes.

CONCLUSIONS

We found an association between dichlorophenols and increased body weight measures (BMI z-score, WC, and obesity) in adolescents. However, further studies, such as a longitudinal study, are needed to confirm and elucidate on our findings.

Blood cadmium and depressive symptoms in young adults (aged 20-39 years)

BACKGROUND

Genetic and environmental factors contribute to the risk of depression and several studies have noted an association between tobacco smoke and depression. Cadmium is a neurotoxicant and the main source of non-occupational exposure is tobacco smoke.

METHOD

We conducted a cross-sectional analysis of data from 2892 young adult (aged 20-39 years) participants of the National Health and Nutrition Examination Survey (NHANES) 2007-2010. Multivariate logistic regressions, adjusted for age, sex, race/ethnicity, education, poverty income ratio (PIR), obesity, alcohol intake, blood lead (BPb) and smoking status, were used to analyze the association between blood cadmium (BCd) and depressive symptoms, as determined by the score on the nine-item Patient Health Questionnaire (PHQ-9).

RESULTS

Individuals in the highest BCd quartile had higher odds of having depressive symptoms [odds ratio (OR) 2.79, 95% confidence interval (CI) 1.84-4.25] than those in the lowest BCd quartile. Smoking status, but not BPb, was statistically significantly associated with depressive symptoms. Stratification by smoking status found that BCd was significantly associated with depressive symptoms in both non-smokers (OR 2.91, 95% CI 1.12-7.58) and current smokers (OR 2.69, 95% CI 1.13-6.42).

CONCLUSIONS

This is the first study to report an association between BCd levels and depressive symptoms using a nationally representative sample. The association of cadmium with depressive symptoms was independent of smoking status. If this association is further confirmed, the continued efforts at reducing cadmium exposures, mainly through tobacco smoking cessation programs, may decrease the incidence of depression.

Polychlorinated Biphenyls and Leukocyte Telomere Length: An Analysis of NHANES 1999-2002

Polychlorinated biphenyls (PCBs) induce the expression of the proto-oncogene c-myc which has a role in cellular growth and proliferation programs. The c-myc up-regulates the telomerase reverse transcriptase which adds the telomeres repeating sequences to the chromosomal ends to compensate for the progressive loss of telomeric sequence. We performed multivariate linear regression to analyze the association of PCBs, polychlorinated dibenzo-p-dioxins, and 1,2,3,4,6,7,8-heptachlorodibenzofuran with leukocyte telomere length (LTL) in the adult population (n = 2413) of the National Health and Nutrition Examination Survey 1999-2002. LTL was natural log-transformed and the results were re-transformed and presented as percent differences. Individuals in the 3rd and 4th quartiles of the sum of PCBs were associated with 8.33% (95% CI: 4.08-13.88) and 11.63% (95% CI: 6.18-17.35) longer LTLs, respectively, compared with the lowest quartile, with evidence of a dose-response relationship (p-trend < 0.01). The association of the sum PCBs with longer LTL was found in both sexes. Additionally, 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin were associated with longer LTL. The age independent association between longer LTL and environmental exposures to PCBs, 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin may support a role as tumor promoter of these compounds. Further studies to evaluate the effect of these compounds on LTL are needed to more fully understand the implications of our finding.

Perfluoroalkyl substances and food allergies in adolescents

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of organic compounds that are persistent in the environment due to their stable carbon-fluorine backbone, which is not susceptible to degradation. Research suggests these chemicals may exert an immunotoxic effect. The aim of this study is to investigate the associations between four PFASs - perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS) - with food sensitization and food allergies in adolescent participants (ages 12-19years) in the National Health and Nutrition Examination Survey (NHANES) 2005-2006 and 2007-2010, respectively. We performed multivariate logistic regression to analyze the association between individual PFASs with food sensitization (defined as having at least 1 food-specific IgE level≥0.35kU/L) in NHANES 2005-2006 and food allergies (self-reported) in NHANES 2007-2010. Serum PFOA, PFOS, and PFHxS were statistically significantly associated with higher odds to have self-reported food allergies in NHANES 2007-2010. When using IgE levels as a marker of food sensitization, we found that serum PFNA was inversely associated with food sensitization (NHANES 2005-2006). In conclusion, we found that serum levels of PFASs were associated with higher odds to have self-reported food allergies. Conversely, adolescents with higher serum PFNA were less likely to be sensitized to food allergens. These results, along with previous studies, warrant further investigation, such as well-designed longitudinal studies.

Cadmium, Lead, and Depressive Symptoms: Analysis of National Health and Nutrition Examination Survey 2011-2012

BACKGROUND

Several studies have noted an association between tobacco smoke and depression. Cadmium and lead are neurotoxicant components of tobacco smoke. The objective of the present study is to investigate the potential association between blood cadmium (BCd) and blood lead (BPb) with current depressive symptoms in the US adult population.

METHODS

We conducted cross-sectional analyses of adult participants (≥ 20 years) from the National Health and Nutrition Examination Survey 2011-2012 (N = 3,905). Multivariate logistic regressions were used to analyze the association between BCd and BPb with depressive symptoms; analyses were also stratified on sex and age groups (20-47 years and ≥ 48 years). Presence or absence of depressive symptoms was determined using the Patient Health Questionnaire module.

RESULTS

Individuals in the highest quartile of BCd had higher odds of having depressive symptoms (odds ratio = 1.68; 95% confidence limits: 1.12, 2.51). This association was found only in male participants and, more specifically, in younger adult male participants (20-47 years). We found that BPb, cigarette smoking, and obesity were associated with depressive symptoms in younger female adults.

CONCLUSIONS

In this study, we report associations between BCd and BPb with current depressive symptoms that were modified by age and sex. Reverse causation cannot be ruled out as a possible explanation since depression may lead to behavioral changes that increase exposure to cadmium and lead (ie, tobacco smoke). The continued efforts at reducing cadmium through tobacco smoking cessation programs may decrease the prevalence of current depressive symptoms.

Windows of Sensitivity to Toxic Chemicals in the Development of Cleft Palates

Cleft lip and cleft palate are among the most common birth defects worldwide. There is a genetic component to the development of these malformations, as well as evidence that environmental exposures and prescription drug use may exacerbate or even produce these manifestations. Thus, it is important to understand the underlying mechanisms and when these exposures affect development of the growing fetus. The purpose of this investigation was to critically review the available literature related to orofacial cleft formation following chemical exposure and identify specific time frames for windows of sensitivity. Further, an aim was to evaluate the potential for predicting effects in humans based on animal studies. Evidence indicates that chemical causes of cleft palate development are due to dose and timing of exposure, susceptibility of the species (i.e., the genetic makeup), and mechanism of action. Several studies demonstrated that dose is a crucial factor; however, some investigators argued that even more important than dose was timing of exposure. Data show that the window of sensitivity to environmental teratogens in the development of cleft palates is quite narrow and follows closely the window of palatogenesis in the fetus of any given species.

Perfluoroalkyl substances and anthropomorphic measures in children (ages 3-11 years), NHANES 2013-2014

BACKGROUND

Perfluoroalkyl acids (PFAAs) are man-made compounds that are persistent in the environment and highly bioaccumulative in the body. Humans are exposed to a mixture of these substances, and the effects of these mixtures may be different than the effects noted for individual compounds. Prenatal exposure to PFAAs has been associated with decreased birth weight. The objective of the present study is to evaluate concurrent serum PFAA levels, as single compounds and as mixtures, in relation to anthropomorphic measures in children.

METHODS

Using multivariate linear regression, we evaluated the association between single or PFAA mixtures and with height-for-age (HAZ), weight-for-age (WAZ), and BMI (BMIZ) z-scores in children (ages 3-11 years) participants of the National Health and Nutrition Examination Survey (NHANES) 2013-2014. Analyses were also stratified by sex. The PFAA mixture was based on relative potency factors express in terms of PFOA equivalency (CmixRPFi) or as molar sum of the PFAA congeners (∑molPFAA).

RESULTS

There was a statistically significant association of PFHxS and PFOS with decreased HAZ in boys. The significantly decreased HAZ in boys was also found when the PFAAs were analyzed as mixtures: CmixRPFi (β = -0.33; 95%CI: 0.63, -0.04) or ΣmolPFAAs (β = -0.30; 95%CI: 0.56, -0.04). In boys, PFHxS was also associated with decreased WAZ and BMIZ. The only statistically significant association found in girls was between decreased HAZ and PFHxS.

CONCLUSIONS

We found sex differences in the association between concurrent serum PFAA levels and anthropomorphic measures in children 3-11 years old. PFAA levels, as single congeners or as mixture concentrations were associated with decreased height-for-age z-score in boys.

Urinary antimony and leukocyte telomere length: An analysis of NHANES 1999-2002

Telomeres are repetitive DNA sequences (TTAGGG) at the end of chromosomes. Cells with critically short telomeres enter replicative senescence and apoptosis. Several in vitro studies report that antimony causes cell apoptosis in human leukocyte cell lines. The goal of this analysis was to investigate whether there is an association between antimony exposure and leukocyte telomere length (LTL) among US adults aged 20 and older based on the National Health and Nutrition Examination Survey (NHANES) 1999-2002. We used multivariate linear regression to analyze the association of urinary antimony with LTL. LTL was log-natural transformed and the results were re-transformed and presented as percent differences. After adjustment for potential confounders, individuals in the 3rd and 4th quartiles of urinary antimony had statistically significantly shorter LTL (-4.78%, 95% CI: -8.42,-0.90; and -6.11%, 95% CI: -11.04,-1.00, respectively) compared to the lowest referent quartile, with evidence of a dose-response relationship (p-value for trend =0.03). Shorter LTL with antimony was driven by middle aged (40-59 years) and older (60-85 years) adult groups. The association may be biologically plausible because of reported oxidative stress and apoptosis effects of antimony on blood cells, effects known to shorten telomere length.

Windows of sensitivity to toxic chemicals in the development of the endocrine system: an analysis of ATSDR's toxicological profile database

This review utilizes the robust database of literature contained in toxicological profiles developed by the Agency for Toxic Substances and Disease Registry. The aim was to use this database to identify developmental toxicity studies reporting alterations in hormone levels in the developing fetus and offspring and identify windows of sensitivity. We identified 74 oral exposure studies in rats that provided relevant information on 30 chemicals from 21 profiles. Most studies located provided information on thyroid hormones, with fewer studies on anterior pituitary, adrenal medulla, ovaries, and testes. No studies pertaining to hormones of the posterior pituitary, pancreas, or adrenal cortex were located. The results demonstrate that development of the endocrine system may be affected by exposure to environmental contaminants at many different points, including gestational and/or lactational exposure. Moreover, this review demonstrates the need for more developmental toxicity studies focused on the endocrine system and specifically alterations in hormone levels.

Windows of sensitivity to toxic chemicals in the development of reproductive effects: an analysis of ATSDR's toxicological profile database

Development of the fetus is a complex process influenced by many factors including genetics, maternal health, and environmental exposures to toxic chemicals. Adverse developmental effects on the reproductive system have the potential to harm generations beyond those directly exposed. Here, we review the available literature in Agency for Toxic Substances and Disease Registry toxicological profiles related to reproductive-developmental effects in animals following in utero exposure to chemicals. We attempt to identify windows of sensitivity. In the discussion, we correlate the findings with human development. The endpoints noted are fertility, estrus, anogenital distance, sex ratio, spermatogenesis, and mammary gland development. We identified some windows of sensitivity; however, the results were hampered by chronic-exposure studies designed to detect effects occurring throughout developmental, including multi-generational studies. This paper demonstrates the need for more acute studies in animals aimed at understanding time periods of development that are more susceptible to chemically induced adverse effects.

Evaluation of ATSDR's MRL and EPA's RfCs/RfDs: Similarities, Differences, and Rationales

Objectives

The Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA) derive minimal risk levels (MRLs) and reference concentrations and doses (RfCs and RfDs), respectively, for environmental contaminants to help identify potential health risks to exposed populations. MRLs, RfDs, and RfCs involve similar derivation methods, but the values sometimes differ for the same chemical. The objectives of this manuscript are to quantitatively assess similarities and differences between MRLs, RfCs, and RfDs, qualitatively describe how a number of factors can influence the development of the health guidance values (HGVs) and identify ongoing collaborations and opportunities for increased coordination of efforts.

Materials and Methods

We collected MRLs and RfCs/RfDs, assessment date, and description of the derivation process from ATSDR's toxicological profiles and EPA's Integrated Risk Information System (IRIS) and Office of Pesticide Program (OPP) and identified reasons for differences between MRLs and RfCs/RfDs.

Results

The most frequent types of differences in values that we found in our analysis included use of different methodologies, use of different studies, and/or completion of a more recent chemical evaluation. These can stem from differences in scientific judgement.

Conclusion

To avoid confusion when disparate HGVs occur between government agencies, a keen understanding of these differences can be helpful for appropriate risk characterization and communication when applying HGVs.

Per- and polyfluoroalkyl mixtures toxicity assessment "Proof-of-Concept" illustration for the hazard index approach

The 2018 ATSDR mixture framework recommends three approaches including the hazard index (HI) for environmental mixture toxicity assessment. Per- and polyfluoroalkyls (PFAS) are found in our environment and general populations. Recent experimental mixture toxicity studies of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) and an assessment of 17 PFAS indicate the use of additivity for their joint toxicity assessment. The aim of this investigation was to detail the stepwise procedures and examine the extent and use of the HI approach for PFAS mixture assessment. Using estimated general public lifetime exposures (high, medium, and low), binary mixtures of PFOS and PFOA yielded, respectively, hazard indices (HIs) of 30.67, 8.33, and 3.63 for developmental toxicity; 10.67, 5.04, and 2.34 for immunological toxicity; 3.57, 1.68, and 0.78 for endocrine toxicity; 4.51, 1.73, and 0.79 for hepatic toxicity; and 15.08, 2.29, and 0.88 for reproductive toxicity. A heterogeneous mixture of PFOA, PFAS, dioxin (CDD), and polybrominated compounds (PBDE) for high exposure scenario yielded HIs of 30.99 for developmental, 10.77 for immunological, 3.64 for endocrine, 4.61 for hepatic, and 17.36 for reproductive effects. The HI values are used as a screening tool; the potential concern for exposures rises as HI values increase. For HI values >1, a follow-up including further analysis of specific exposures, use of internal dosimetry, and uncertainty factors is conducted before recommending appropriate actions. The HI approach appears suitable to address present-day PFAS public health concerns for initial assessment of multiple health effects, until further insights are gained into their mechanistic toxicology.The findings and conclusions in this article are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry.