Organochlorine chemicals and children's health

Prenatal Exposure to Endocrine-disrupting Chemicals in Relation to Autism Spectrum Disorder and Intellectual Disability

BACKGROUND

Exposure to endocrine disruptors is unavoidable. Many such compounds are suspected to impact neurologic development of children, but most studies conducted have considered effects of individual chemicals in isolation. Because exposures co-occur, it is important to consider their health impacts in a single regression framework.

METHODS

We applied Bayesian statistical tools (including shared mean and mixture priors for 25 unique chemicals) to study independent associations of endocrine disruptor biomarkers with autism spectrum disorder (ASD) (n = 491) and intellectual disability (n = 155), compared with 373 general population controls, in the Early Markers for Autism study. We measured biomarkers in maternal serum collected and stored from midpregnancy and considered them individually or as a class (i.e., summed polychlorinated biphenyls). We adjusted all models for original matching factors (child sex and month and year of birth), maternal age, maternal race/ethnicity, parity, and maternal education at the time samples were collected. We estimated the change in the odds of ASD or intellectual disability per 1 SD increase in the z-score of measured biomarker concentration for each chemical.

RESULTS

Odds of ASD and intellectual disability did not change with increasing concentration for any specific endocrine disruptor. The effect estimates for each chemical were centered on or near an odds ratio of 1.00 in both models where we applied a shared mean or a mixture prior.

CONCLUSION

Our mixtures analyses do not suggest an independent relationship with ASD or intellectual disability with any of the 25 chemicals examined together in this mixtures analysis.

Secular Trend of Age at Menarche in Chinese Adolescents Born From 1973 to 2004

OBJECTIVES

To estimate secular trend and factors influencing the age at menarche for Chinese girls born from 1973 to 2004.

METHODS

Data were collected from the China Health and Nutrition Survey, a prospective open cohort and an ongoing nationwide health and nutrition survey, consisting of 3199 apparently healthy Chinese girls aged 6 to 18 years at entry from 1991 to 2011. Average age at menarche and its 95% confidence interval were estimated by weighted means of Kaplan-Meier survival analysis. Cox proportional hazard models were applied to identify the independent predictive factors of age at menarche.

RESULTS

The age at menarche declined from 14.25 in Chinese girls born before 1976 to 12.60 in girls born after 2000, with an estimated decline of 0.51 years per decade (P < .001). The downward trend of age at menarche for rural girls was greater than for urban girls (0.62 vs 0.35 years per decade; P < .001). Girls living in urban areas, living in central areas, with high BMI, and with high-energy diets had a high risk of early menarche, whereas girls living on the east coast who had high-carbohydrate diets had a low risk of early menarche.

CONCLUSIONS

The authors of this study found a continuous downward secular trend of age at menarche for Chinese girls in both urban and rural areas born from 1973 to 2004. Among all variables, urban residency, BMI, and energy intake are negatively associated with age at menarche, whereas carbohydrate intake is positively associated with age at menarche.

Polychlorinated Biphenyl and Organochlorine Pesticide Concentrations in Maternal Mid-Pregnancy Serum Samples: Association with Autism Spectrum Disorder and Intellectual Disability

BACKGROUND

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are neurodevelopmental toxicants, but few studies have examined associations with autism spectrum disorder (ASD).

OBJECTIVES

We aimed to determine whether prenatal exposure to PCBs and OCPs influences offspring risk of ASD and intellectual disability without autism (ID).

METHODS

We conducted a population-based case-control study among Southern California births, including children with ASD (n = 545) meeting Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV-TR) criteria and ID (n = 181), as well as general population (GP) controls (n = 418). Concentrations of 11 PCB congeners and 2 OCPs measured in banked second-trimester serum samples were compared between the diagnostic groups. Logistic regression was used to calculate crude and adjusted odds ratios (AOR) for associations with ASD, and separately for ID, compared with GP controls, by quartiles of analyte concentrations in primary analyses.

RESULTS

Geometric mean levels of several PCB congeners were higher in the ASD group than in the ID and GP groups. ASD risk was elevated for a number of PCB congeners, particularly for the highest vs. lowest quartile of PCB138/158 (AOR = 1.79; 95% CI: 1.10, 2.71) and PCB153 (AOR = 1.82; 95% CI: 1.10, 3.02), and for highest deciles of other congeners in secondary analyses. PCB138/158 was also associated with increased ID (AOR = 2.41; 95% CI: 1.18, 4.91), though no trend was suggested. OCPs were not associated with increased risk of ASD in primary analyses, whereas nonmonotonic increases in risk of ID were found with p,p´-DDE.

CONCLUSIONS

Our results suggest higher levels of some organochlorine compounds during pregnancy are associated with ASD and ID. Citation: Lyall K, Croen LA, Sjödin A, Yoshida CK, Zerbo O, Kharrazi M, Windham GC. 2017. Polychlorinated biphenyl and organochlorine pesticide concentrations in maternal mid-pregnancy serum samples: association with autism spectrum disorder and intellectual disability. Environ Health Perspect 125:474-480; http://dx.doi.org/10.1289/EHP277.

Body burdens of brominated flame retardants and other persistent organo-halogenated compounds and their descriptors in US girls

BACKGROUND

Levels of brominated flame retardants are increasing in US populations, yet little data are available on body burdens of these and other persistent hormonally active agents (HAAs) in school-aged children. Exposures to such chemicals may affect a number of health outcomes related to development and reproductive function.

OBJECTIVE

Determine the distribution of biomarkers of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and organo-chlorinated pesticides (OCPs), such as DDT/DDE, in children, and their variation by key descriptor variables.

METHODS

Ethnically diverse cohorts of girls 6-8 y old at baseline are being followed for growth and pubertal development in a multi-site, longitudinal study. Nearly 600 serum samples from the California and Ohio sites were analyzed for lipids, 35 PCB congeners, 11 PBDE congeners, and 9 OCPs. The biomarker distributions were examined and geometric means compared for selected analytes across categories of age, race, site, body mass index (BMI), parental education, maternal age at delivery, and breast feeding in adjusted models.

RESULTS

Six PBDE congeners were detected among greater than 70% of samples, with BDE-47 having the highest concentration (median 42.2, range 4.9-855 ng/g lipid). Girls in California had adjusted geometric mean (GM) PBDE levels significantly higher than girls in Ohio. Furthermore, Blacks had significantly higher adjusted GMs of all six PBDE congeners than Whites, and Hispanics had intermediate values. GMs tended to be lower among more obese girls, while other variables were not strongly associated. In contrast, GMs of the six PCB congeners most frequently detected were significantly lower among Blacks and Hispanics than Whites. PCBs and the three pesticides most frequently detected were also consistently lower among girls with high BMI, who were not breast-fed, whose mothers were younger, or whose care-givers (usually parents) were less educated. Girls in California had higher GMs than in Ohio for the pesticides and most PCB congeners, but the opposite for CB-99 and -118.

CONCLUSIONS

Several of these potential HAAs were detected in nearly all of these young girls, some at relatively high levels, with variation by geographic location and other demographic factors that may reflect exposure pathways. The higher PBDE levels in California likely reflect differences in fire regulation and safety codes, with potential policy implications.

Racial and ethnic differences in reproductive potential across the life cycle

OBJECTIVE

To review variations in specific reproductive health outcomes by race and ethnicity. A growing number of reports have explored potential gaps in the quality of reproductive health and healthcare across racial and ethnic groups. Diverse results from numerous investigations have made it challenging for practitioners to confirm the significance of these disparities.

METHOD(S)

Three specific areas of the reproductive life cycle were examined: pubertal onset, outcomes from treatment with assisted reproductive technologies (ART), and the menopausal transition. These areas were selected as they encompass a continuum of events across the reproductive life span of women. Outcomes were compared in black, white, Asian, and Hispanic women. Medline searches querying on keywords puberty, IVF, ART, menopause, menopausal symptoms, racial disparity, race, Asian, Japanese, Chinese, African American, black, Hispanic, and Latino were performed to isolate relevant publications for review.

RESULT(S)

Differences across race and ethnicity were noted in each clinical endpoint. The most notable findings included earlier puberty in blacks and Hispanics compared with whites, significantly lower live birth rates after ART in all racial and ethnic groups compared with whites, and differences in perimenopausal symptomatology and possibly timing in various racial/ethnic groups compared with whites. Additional research is needed to completely unravel the full significance and basic underpinnings of these disparities. Some of the limitations of the current state of the literature in drawing conclusions about the independent effect of race/ethnicity on reproductive disparities include small samples sizes in some studies, inconsistencies in the characterization of racial/ethnic groups, and incomplete control of potential confounding.

CONCLUSION(S)

Race and ethnicity appear to be important correlates of outcomes from the initiation of reproduction functioning through to its conclusion. The ultimate goal of identifying racial disparities in reproduction is to isolate the basic determinants of disparities and formulate strategies to improve outcomes for women at risk. The differences demonstrated in this review of the literature could represent environmental, sociocultural, and/or genetic correlates of race that influence these important milestones.

Assessing levels of contaminants in breast milk: methodological issues and a framework for future research

To assess the scale of the possible exposure by the breast-fed infant to potentially harmful substances in breast milk, methodologically robust studies are essential. Many studies in this field, however, do not report details of crucial issues such as recruitment and milk sampling. The aims of the study reported here were to develop robust methods for the study of contaminants in breast milk, and to develop a framework for future research and population monitoring. Three cohorts of women and babies were recruited by midwives from five sites in northern England. Cohort 1 (cross-sectional, n = 322) were asked to provide two milk samples, one at one week following birth and one at a subsequent time point. Cohort 2 (longitudinal, n = 54) were asked to provide five samples at specified time points over the first 12-16 weeks after birth. Cohort 3 (convenience, n = 18), mothers of babies in the Special Care Unit, were asked to donate surplus breast milk. A novel method of analysing fat concentration in small volumes was developed and tested. A randomly selected set of samples from different donors and stages of lactation was screened for organochlorine pesticide residues, polychlorinated biphenyls, dioxins/furans, phthalates and heavy metals. A total of 453 samples were donated. Cohort 3 was the least successful route of recruitment. Cohorts 1 and 2 combined were most representative of the population. Sample collection, transport and storage procedures, and the collection of data on life style and diet, were robust and acceptable to women. Midwifery involvement in recruitment was an essential component. This study offers a framework both for the conduct of future research studies, and for the establishment of regional and national monitoring mechanisms for contaminants in breast milk. Similar work on contaminants in formula as fed to babies is needed to inform risk assessment methods.

Predictors of organochlorines in New York City pregnant women, 1998-2001

Organochlorine compounds (OCs) have been found widely in human tissues. However, levels have been rapidly declining since their virtual ban in the 1970s. We measured 1,1'-dichloro-2,2'-bis(4-chlorophenyl)ethylene (DDE), polychlorinated biphenyls (PCBs), and trans-nonachlor (TN) in 194 pregnant women in New York City and examined demographic and dietary predictors of their levels in serum. Serum OC levels were low (median microg/L: 0.64 DDE, 0.79 PCB); TN was largely below the level of detection (74%). In multivariate models, levels of OCs increased with age; DDE was higher in women not born in the US or Puerto Rico; PCB were higher in women who bought fresh fish and lower in those with higher body mass indices.

Ethnic differences in the presence of secondary sex characteristics and menarche among US girls: the Third National Health and Nutrition Examination Survey, 1988-1994

OBJECTIVE

To assess measures of puberty-presence of pubic hair, breast development, and menarche-for 3 racial/ethnic groups of girls in the United States.

METHODS

Using data from the Third National Health and Nutrition Examination Survey, this study sample was restricted to 1623 girls aged 8 to 16 years (466 non-Hispanic white, 589 non-Hispanic black, and 568 Mexican American) for whom information was available on Tanner stages of pubic hair and breast development. Subsequently, the sample was restricted to 1168 girls aged 10 to 16 years (330 non-Hispanic white, 419 non-Hispanic black, and 419 Mexican American) for whom menarche data were available. Tanner stage II or higher was used to define pubic hair and breast development; menarche status was self-reported. The percentage of girls who had pubic hair and breast development and had achieved menarche was computed by age and race/ethnicity. Probit and failure time models were applied to estimate mean ages at onset of pubic hair, breast development, and menarche. The racial/ethnic differences also were examined after adjustment for social and economic variables and current body mass index.

RESULTS

Black and Mexican American girls had pubic hair and breast development and had achieved menarche at younger ages than white girls. For example, 49.4% of black girls aged 9 years had breast development compared with 24.5% of Mexican American girls and 15.8% of white girls. The mean age at onset of pubic hair, breast development, and menarche was 9.5, 9.5, and 12.1 year for black girls; 10.3, 9.8, and 12.2 years for Mexican American girls; and 10.5, 10.3, and 12.7 years for white girls. These ethnic differences remained even after adjustment for current body mass index and several social and economic variables.

CONCLUSION

Black girls on average enter puberty first, followed by Mexican American and then white girls.