High levels of sleep disturbance across early childhood increases cardiometabolic disease risk index in early adolescence: longitudinal sleep analysis using the Health Outcomes and Measures of the Environment study

STUDY OBJECTIVES

This study examines the impact of sleep duration, bedtime, and sleep disturbance during early childhood on the risk of cardiometabolic disorder (CMD) in early adolescence.

METHODS

Within the Health Outcomes and Measures of Environment Study, we examined sleep patterns of 330 children from ages 2 to 8 years and the relationship of these sleep patterns with cardiometabolic risk measures at age 12 (N = 220). We used a group-based semi-parametric mixture model to identify distinct trajectories in sleep duration, bedtime timing, and sleep disturbance for the entire sample. We then examined the associations between sleep trajectories and CMD risk measures using general linear models using both an unadjusted model (no covariates) and an adjusted model (adjusting for child pubertal stage, child sex, duration of breastfeeding, household income, maternal education, and maternal serum cotinine).

RESULTS

In the unadjusted and adjusted models, we found significant differences in CMD risk scores by trajectories of sleep disturbance. Children in the "high" disturbance trajectory had higher CMD risk scores than those in the 'low' disturbance trajectory (p's = 0.002 and 0.039, respectively). No significant differences in CMD risk were observed for bedtime timing or total sleep time trajectories in the unadjusted or adjusted models.

CONCLUSIONS

In this cohort, caregiver-reported sleep disturbance in early childhood was associated with more adverse cardiometabolic profiles in early adolescence. Our findings suggest that trials to reduce CMD risk via sleep interventions-which have been conducted in adolescents and adults-may be implemented too late.

The U.S. PFAS exposure burden calculator for 2017-2018: Application to the HOME Study, with comparison of epidemiological findings from NHANES

BACKGROUND

The 2017-2018 U.S. PFAS exposure burden calculator was designed to provide a summary exposure score for per- and polyfluoroalkyl substances (PFAS) mixtures using targeted PFAS analyte data. Its aim was to place PFAS burden score estimates onto a common scale based on nationally representative U.S. reference ranges from 2017 to 2018, enabling comparisons of overall PFAS burden scores across studies even if they did not measure the same set of PFAS analytes.

OBJECTIVE

To use the U.S. PFAS exposure burden calculator for comparing the same mixture of PFAS compounds in similarly aged adolescents and their associations with cardiometabolic outcomes in the HOME Study and NHANES between 2015 and 2018.

METHODS

We applied the PFAS burden calculator to 8 PFAS analytes measured in the serum of adolescents from the HOME Study (Cincinnati, Ohio; age range 11-14 years; years: 2016-2019; n = 207) and NHANES (US; age range 12-14 years; years 2015-2018; n = 245). We used the non-parametric Mann-Whitney U test and chi-squared test to compare the two study samples. In both studies, we examined associations of PFAS burden scores with the same cardiometabolic outcomes, adjusted for the same core set of covariates using regression analyses. We conducted sensitivity analyses to verify robustness of exposure-outcome associations, by accounting for measurement error of PFAS burden scores.

RESULTS

PFAS burden scores were significantly different (p = 0.004) between the HOME Study (median: 0.00, interquartile range - 0.37, 0.34) and the NHANES samples (median: 0.04, IQR -0.11, 0.54), while no significant difference was found for PFAS summed concentrations (p = 0.661). In the HOME Study, an interquartile (IQR) increase in PFAS burden score was associated with higher total cholesterol [7.0 mg/dL, 95% CI: 0.6, 13.4]; HDL [2.8 mg/dL, 95% CI: 0.4, 5.2]; LDL [5.9 mg/dL, 95% CI: 0.5, 11.3], insulin [0.1 log(mIU/L), 95% CI: 0.01, 0.2], and HOMA-IR [0.1, 95% CI: 0.01, 0.2]. In NHANES, an IQR increase in PFAS burden score was associated with higher diastolic blood pressure [2.4 mmHg, 95% CI: 0.4, 4.4] but not with other outcomes. Sensitivity analyses in the HOME Study and NHANES were consistent with the main findings.

CONCLUSIONS

Performance of the U.S. PFAS exposure burden calculator was similar in a local versus national sample of adolescents, and may be a useful tool for the assessment of PFAS mixtures across studies.

Fluoride exposure and thyroid hormone levels in pregnancy: The MIREC cohort

BACKGROUND

Fluoride exposure may increase the risk of hypothyroidism, but results from previous studies are inconsistent at low-level fluoride exposure (i.e., ≤0.7 mg/L). Human studies of fluoride and thyroid hormone levels in pregnancy are scarce.

OBJECTIVES

We examined associations between fluoride exposure and maternal thyroid hormone levels in a Canadian pregnancy cohort, with consideration for fetal sex-specific effects.

METHODS

We measured fluoride concentrations in drinking water and spot urine samples collected during each trimester from 1876 pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study. We also measured maternal thyroid stimulating hormone (TSH), free thyroxine (FT4), and total thyroxine (TT4) levels during the first trimester of pregnancy. We used linear and non-linear regression models to estimate associations between fluoride exposure and levels of TSH, FT4, and TT4. We explored effect modification by fetal sex and considered maternal iodine status as a potential confounder.

RESULTS

A 1 mg/L increase in urinary fluoride was associated with a 0.30 (95 %CI: 0.08, 0.51) logarithmic unit (i.e., 35.0 %) increase in TSH among women pregnant with females, but not males (B = 0.02; 95 %CI: -0.16, 0.19). Relative to women with urinary fluoride concentrations in the first quartile (0.05-0.32 mg/L), those with levels in the third quartile (0.49-0.75 mg/L) had higher FT4 and TT4 (i.e., inverted J-shaped associations), but the association was not statistically significant after adjustment for covariates (p = 0.06). Water fluoride concentration showed a U-shaped association with maternal FT4, whereby women with water fluoride concentrations in the second (0.13-0.52 mg/L) and third (0.52-0.62 mg/L) quartiles had significantly lower FT4 compared to those with levels in the first quartile (0.04-0.13 mg/L). Adjustment for maternal iodine status did not change the results.

DISCUSSION

Fluoride exposure was associated with alterations in maternal thyroid hormone levels, the magnitude of which appeared to vary by fetal sex. Given the importance of maternal thyroid hormones for fetal neurodevelopment, replication of findings is warranted.

Prenatal fluoride exposure, offspring visual acuity and autonomic nervous system function in 6-month-old infants

BACKGROUND

Prenatal fluoride exposure can have adverse effects on children's development; however, associations with visual and cardiac autonomic nervous system functioning are unknown. We examined associations between prenatal fluoride exposure and visual acuity and heart rate variability (HRV) in 6-month-old infants.

METHODS

We used data from Canadian mother-infant pairs participating in the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort. We estimated prenatal fluoride exposure using: i) fluoride concentration in drinking water (mg/L), ii) maternal urinary fluoride adjusted for specific gravity (MUFSG; mg/L) and averaged across pregnancy, and iii) maternal fluoride intake (µg/kg/day) from consumption of water, tea, and coffee, adjusted for maternal body weight (kg). We used multivariable linear regression to examine associations between each measure of fluoride exposure and Teller Acuity Card visual acuity scores (n = 435) and assessed HRV (n = 400) using two measures: root mean square of successive differences (RMSSD) and the standard deviation of N-N intervals (SDNN) measured at 6-months of age.

RESULTS

Median (IQR) values for water fluoride, MUFSG, and daily fluoride intake were 0.20 (IQR: 0.13-0.56) mg/L; 0.44 (0.28-0.70) mg/L and 4.82 (2.58-10.83) µg/kg/day, respectively. After adjustment for confounding variables, water fluoride concentration was associated with poorer infant visual acuity (B = -1.51; 95 % CI: -2.14,-0.88) and HRV as indicated by lower RMSSD (B = -1.60; 95 % CI: -2.74,-0.46) but not SDNN. Maternal fluoride intake was also associated with poorer visual acuity (B = -0.82; 95 % CI: -1.35,-0.29) and lower RMSSD (B = -1.22; 95 % CI: -2.15,-0.30). No significant associations were observed between MUFSG and visual acuity or HRV.

CONCLUSION

Fluoride in drinking water was associated with reduced visual acuity and alterations in cardiac autonomic function in infancy, adding to the growing body of evidence suggesting fluoride's developmental neurotoxicity.

Prenatal exposure to replacement flame retardants and organophosphate esters and childhood adverse respiratory outcomes

BACKGROUND

The association of prenatal exposure to organophosphate esters (OPEs) and replacement brominated flame retardants (RBFRs) with respiratory outcomes has not been previously investigated in humans, despite reports that these chemicals can cross the placenta and alter lung development as well as immune functions.

METHODS

In a cohort of 342 pregnant women recruited between 2003 and 2006 in the greater Cincinnati, Ohio Metropolitan area, we measured indoor dust OPEs and RBFRs at 20 weeks of gestation and urinary OPEs at 16 and 26 weeks of gestation and at delivery. We performed generalized estimating equations and linear mixed models adjusting for covariates to determine the associations of prenatal OPEs and RBFRs exposures with adverse respiratory outcomes in childhood, reported every six months until age 5 years and with lung function at age 5 years. We used multiple informant modeling to examine time-specific associations between maternal urinary OPEs and the outcomes.

RESULTS

Dust concentrations of triphenyl phosphate (TPHP) (RR: 1.40, 95% CI: 1.18-1.66), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (RR: 1.51, 95% CI: 1.23-1.85), and bis(2-ethylhexyl) tetrabromophthalate (RR: 1.57, 95% CI: 1.28-1.94) were associated with higher risk of wheezing during childhood. Dust TPHP concentrations were associated with higher risk of respiratory infections (RR: 1.43, 95% CI: 1.08-1.94), and dust tris-(2-chloroethyl) phosphate concentrations were associated with hay fever/allergies (RR: 1.11, 95% CI: 1.01-1.21). We also found that dust tris-(2-chloroethyl) phosphate loadings were associated with lower lung function. Urinary OPEs mainly at week 16 of gestation tended to be associated with adverse respiratory outcome, while bis(1-chloro-2-propyl) phosphate and diphenyl phosphate at delivery were associated with lower risk of hay fever/allergies.

CONCLUSIONS

In-utero exposure to OPEs and RBFRs may be a risk factor for adverse respiratory outcomes in childhood, depending on the timing of exposure.

The Effect of Pesticide Spray Season and Residential Proximity to Agriculture on Glyphosate Exposure among Pregnant People in Southern Idaho, 2021

BACKGROUND

Glyphosate is one of the most heavily used pesticides in the world, but little is known about sources of glyphosate exposure in pregnant people living in agricultural regions.

OBJECTIVE

Our objective was to evaluate glyphosate exposure during pregnancy in relation to residential proximity to agriculture as well as agricultural spray season.

METHODS

We quantified glyphosate concentrations in 453 urine samples collected biweekly from a cohort of 40 pregnant people in southern Idaho from February through December 2021. We estimated each participant's glyphosate exposure as the geometric mean (GM) of glyphosate concentrations measured in all samples (average n = 11 samples/participant), as well as the GM of samples collected during the pesticide "spray season" (defined as those collected 1 May-15 August; average n = 5 samples/participant) and the "nonspray season" (defined as those collected before 1 May or after 15 August; average n = 6 samples/participant). We defined participants who resided < 0.5 km from an actively cultivated agriculture field to live "near fields" and those residing ≥ 0.5 km from an agricultural field to live "far from fields" (n = 22 and 18, respectively).

RESULTS

Among participants living near fields, urinary glyphosate was detected more frequently and at significantly increased GM concentrations during the spray season in comparison with the nonspray season (81% vs. 55%; 0.228 μ g / L vs. 0.150 μ g / L , p < 0.001 ). In contrast, among participants who lived far from fields, neither glyphosate detection frequency nor GMs differed in the spray vs nonspray season (66% vs. 64%; 0.154 μ g / L vs. 0.165 μ g / L , p = 0.45 ). Concentrations did not differ by residential proximity to fields during the nonspray season (0.154 μ g / L vs. 0.165 μ g / L , for near vs. far, p = 0.53 ).

DISCUSSION

Pregnant people living near agriculture fields had significantly increased urinary glyphosate concentrations during the agricultural spray season than during the nonspray season. They also had significantly higher urinary glyphosate concentrations during the spray season than those who lived far from agricultural fields at any time of year, but concentrations did not differ during the nonspray season. These findings suggest that agricultural glyphosate spray is a source of exposure for people living near fields. https://doi.org/10.1289/EHP12768.

Sex difference of pre- and post-natal exposure to six developmental neurotoxicants on intellectual abilities: a systematic review and meta-analysis of human studies

BACKGROUND

Early life exposure to lead, mercury, polychlorinated biphenyls (PCBs), polybromide diphenyl ethers (PBDEs), organophosphate pesticides (OPPs), and phthalates have been associated with lowered IQ in children. In some studies, these neurotoxicants impact males and females differently. We aimed to examine the sex-specific effects of exposure to developmental neurotoxicants on intelligence (IQ) in a systematic review and meta-analysis.

METHOD

We screened abstracts published in PsychINFO and PubMed before December 31st, 2021, for empirical studies of six neurotoxicants (lead, mercury, PCBs, PBDEs, OPPs, and phthalates) that (1) used an individualized biomarker; (2) measured exposure during the prenatal period or before age six; and (3) provided effect estimates on general, nonverbal, and/or verbal IQ by sex. We assessed each study for risk of bias and evaluated the certainty of the evidence using Navigation Guide. We performed separate random effect meta-analyses by sex and timing of exposure with subgroup analyses by neurotoxicant.

RESULTS

Fifty-one studies were included in the systematic review and 20 in the meta-analysis. Prenatal exposure to developmental neurotoxicants was associated with decreased general and nonverbal IQ in males, especially for lead. No significant effects were found for verbal IQ, or postnatal lead exposure and general IQ. Due to the limited number of studies, we were unable to analyze postnatal effects of any of the other neurotoxicants.

CONCLUSION

During fetal development, males may be more vulnerable than females to general and nonverbal intellectual deficits from neurotoxic exposures, especially from lead. More research is needed to examine the nuanced sex-specific effects found for postnatal exposure to toxic chemicals.

Cohort profile update: The Canadian Maternal-Infant Research on Environmental Chemicals Child Development study (MIREC-CD PLUS)

BACKGROUND

The pan-Canadian Maternal-Infant Research on Environmental Chemicals (MIREC) study was established to determine whether maternal environmental chemical exposures were associated with adverse pregnancy outcomes in 2001 pregnant women.

OBJECTIVES

The MIREC-Child Development (CD PLUS) study followed this cohort with the goal of assessing the potential effects of prenatal exposures on anthropometry and neurodevelopment in early childhood.

POPULATION

MIREC families with children between the ages of 15 months and 5 years who had agreed to be contacted for future research (n = 1459) were invited to participate in MIREC-CD PLUS which combines data collected from an online Maternal Self-Administered Questionnaire with biomonitoring and neurodevelopment data collected from two in-person visits.

PRELIMINARY RESULTS

Between April 2013 and March 2015, 803 children participated in the Biomonitoring visit where we collected anthropometric measures, blood, and urine from the children. The Behavioural Assessment System for Children-2, Behaviour Rating Inventory of Executive Function, MacArthur-Bates Communicative Development Inventories and the Communication subscale of the Adaptive Behaviour Scale from the Bayley Scales of Infant and Toddler Development-III are available on close to 900 children. There were 610 singleton children who completed in-person visits for neurodevelopment assessments including the Social Responsiveness Scale, Wechsler Preschool Primary Scale of Intelligence-III and NEuroPSYchological assessments (NEPSY). Currently, we are following the cohort into early adolescence to measure the impact of early life exposures on endocrine and metabolic function (MIREC-ENDO).

CONCLUSIONS

Data collection for the MIREC-CD PLUS study is complete and analysis of the data continues. We are now extending the follow-up of the cohort into adolescence to measure the impact of early life exposures on endocrine and metabolic function (MIREC-ENDO). MIREC-CD PLUS is limited by loss to follow-up and the fact that mothers are predominately of higher socioeconomic status and 'White' ethnicity, which limits our generalizability. However, the depth of biomonitoring and clinical measures in MIREC provides a platform to examine associations of prenatal, infancy and childhood exposures with child growth and development.

Exposure to dust organophosphate and replacement brominated flame retardants during infancy and risk of subsequent adverse respiratory outcomes

BACKGROUND

Children are highly exposed to flame retardants in indoor environments, partly through inhalation. However, the associations of early life exposure to novel organophosphate (OPFRs) and replacement brominated flame retardants (RBFRs) with adverse respiratory outcomes during childhood are unclear.

METHODS

We used a prospective birth cohort of 234 children recruited from the greater Cincinnati, Ohio metropolitan area between 2003 and 2006. OPFRs and RBFRs were analyzed in dust sampled from the homes' main activity room and the children's bedroom floor at child age 1 year. Caregivers reported subsequent respiratory symptoms every six months until child age 5 years and we measured forced expiratory volume in 1 s as well as peak expiratory flow (PEF) at child age 5 years. We performed generalized estimating equations and linear regression modeling adjusted for covariates to examine the exposure-outcome associations.

RESULTS

Geometric means (GMs) (standard error [SE]) for dust concentrations were 10.27 (0.63) μg/g for total OPFRs (ΣOPFRs) and 0.48 (0.04) μg/g for total RBFRs (ΣRBFRs); GMs (SE) for dust loadings were 2.82 (0.26) μg/m2 for ΣOPFRs and 0.13 (0.01) μg/m2 for ΣRBFRs. Dust ∑OPFRs concentrations at age 1 year were associated with higher subsequent risks of wheezing (relative risk [RR]: 1.68, 95% confidence interval [CI]: 1.20-2.34), respiratory infections (RR: 4.01, 95% CI: 1.95-8.24), and hay fever/allergies (RR: 1.33, 95% CI: 1.10-1.60), whereas ∑OPFRs dust loadings at age 1 year were associated with higher risks of subsequent respiratory infections (RR: 1.87, 95% CI: 1.05-3.34) and hay fever/allergies (RR: 1.34, 95% CI: 1.19-1.51). PEF (mL/min) was lower with higher ∑OPFRs dust loadings (β: -12.10, 95% CI: -21.10, -3.10) and with the RBFR bis(2-ethylhexyl) tetrabromophthalate (β: -9.05, 95% CI: -17.67, -0.43).

CONCLUSIONS

Exposure to OPFRs and RBFRs during infancy may be a risk factor for adverse respiratory outcomes during childhood.

Prenatal and concurrent blood mercury concentrations and associations with IQ in canadian preschool children

BACKGROUND

Prenatal and childhood mercury (Hg) exposures have been associated with negative impacts on child neurodevelopment. It is unclear if associations persist at the low Hg exposures typical in Western countries.

OBJECTIVE

To examine associations between prenatal/childhood blood Hg concentrations and child IQ in Canadian male and female children while considering the potential modifying role of prenatal fish consumption.

METHODS

We analyzed data from the Maternal-Infant Research on Environmental Chemicals study. Hg was measured in first trimester (n = 527), cord (n = 430), and child (at 3-4 years of age, n = 355) blood and examined sex-stratified associations between blood Hg and children's Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ), and General Language Composite (GLC) scores (assessed with WPPSI-III). Prenatal Hg analyses were further stratified by prenatal fish consumption (low: 0-2, moderate: 3-7, or high: ≥8 times/month).

RESULTS

Higher cord blood Hg concentrations were associated with lower PIQ (ß = -3.27; 95%CI: 6.44, -0.09) in male children with the lowest prenatal fish consumption. Progressively stronger positive associations were observed with PIQ in male children for moderate (ß = 1.08; 95%CI: 0.10, 2.26) and high (ß = 3.07; 95%CI: 1.95, 4.19) prenatal fish consumption. Cord blood Hg concentrations were positively associated with female children's FSIQ (ß = 1.29; 95% CI: 0.77, 1.81) and PIQ (ß = 2.01; 95% CI: 1.19, 2.83); however, when stratified only in the highest fish consumption subgroup. Among female children, higher child blood Hg concentrations were associated with an approximately 1-point increase in FSIQ, VIQ, and GLC.

CONCLUSIONS

Prenatal exposure to low levels of Hg was associated with lower PIQ scores in male children with low prenatal fish intake. Positive associations between cord and child blood Hg concentrations and IQ were primarily observed in female children and may be due to beneficial effects of prenatal fish intake.

Association between prenatal antibiotic exposure and autism spectrum disorder among term births: A population-based cohort study

BACKGROUND

Prenatal antibiotic exposure induces changes in the maternal microbiome, which could influence the development of the infant's microbiome-gut-brain axis.

OBJECTIVES

We assessed whether prenatal antibiotic exposure is associated with an increased risk of autism spectrum disorder (ASD) in offspring born at term.

METHODS

This population-based retrospective cohort study included everyone who delivered a live singleton-term infant in British Columbia, Canada between April 2000 and December 2014. Exposure was defined as filling antibiotic prescriptions during pregnancy. The outcome was an ASD diagnosis from the British Columbia Autism Assessment Network, with a follow-up to December 2016. To examine the association among pregnant individuals treated for the same indication, we studied a sub-cohort diagnosed with urinary tract infections. Cox proportional hazards models were used to estimate unadjusted and adjusted hazard ratios (HR). The analysis was stratified by sex, trimester, cumulative duration of exposure, class of antibiotic, and mode of delivery. We ran a conditional logistic regression of discordant sibling pairs to control for unmeasured environmental and genetic confounding.

RESULTS

Of the 569,953 children included in the cohort, 8729 were diagnosed with ASD (1.5%) and 169,922 were exposed to prenatal antibiotics (29.8%). Prenatal antibiotic exposure was associated with an increased risk of ASD (HR 1.10, 95% confidence interval [CI] 1.05, 1.15), particularly for exposure during the first and second trimesters (HR 1.11, 95% CI 1.04, 1.18 and HR 1.09, 95% CI 1.03, 1.16, respectively), and exposure lasting ≥15 days (HR 1.13, 95% CI 1.04, 1.23). No sex differences were observed. The association was attenuated in the sibling analysis (adjusted odds ratio 1.04, 95% CI 0.92, 1.17).

CONCLUSIONS

Prenatal antibiotic exposure was associated with a small increase in the risk of ASD in offspring. Given the possibility of residual confounding, these results should not influence clinical decisions regarding antibiotic use during pregnancy.

Exogenous oxytocin administration during labor and autism spectrum disorder

BACKGROUND

Oxytocin is a neuropeptide hormone that plays a key role in social behavior, stress regulation, and mental health. Synthetic oxytocin administration is a common obstetrical practice, and importantly, previous research has suggested that intrapartum exposure may increase the risk of neurodevelopmental disorders, such as autism spectrum disorder.

OBJECTIVE

This study aimed to examine the association between synthetic oxytocin exposure during labor and autism spectrum disorder diagnosis in the child.

STUDY DESIGN

This population-based retrospective cohort study compared 2 cohorts of children: (1) all children born in British Columbia, Canada between April 1, 2000 and December 31, 2014 (n=414,336 births), and (2) all children delivered at Soroka University Medical Center in Be'er-Sheva, Israel between January 1, 2011 and December 31, 2019 (n=82,892 births). Nine different exposure groups were examined. Cox proportional hazards models were used to estimate crude and adjusted hazard ratios of autism spectrum disorder in both cohorts on the basis of induction and/or augmentation exposure status. To further control for confounding by indication, we conducted sensitivity analyses among a cohort of healthy, uncomplicated deliveries and among a group that was induced only for postdates. In addition, we stratified our analyses by infant sex to assess for potential sex differences.

RESULTS

In the British Columbia cohort, 170,013 of 414,336 deliveries (41.0%) were not induced or augmented, 107,543 (26.0%) were exposed to oxytocin, and 136,780 (33.0%) were induced or augmented but not exposed to oxytocin. In the Israel cohort, 51,790 of 82,892 deliveries (62.5%) were not induced or augmented, 28,852 (34.8%) were exposed to oxytocin, and 2250 (2.7%) were induced or augmented but not exposed to oxytocin. On adjusting for covariates in the main analysis, significant associations were observed in the Israel cohort, including adjusted hazard ratios of 1.51 (95% confidence interval, 1.20-1.90) for oxytocin-augmented births and 2.18 (95% confidence interval, 1.32-3.57) for those induced by means other than oxytocin and not augmented. However, oxytocin induction was not significantly associated with autism spectrum disorder in the Israel cohort. In the Canadian cohort, there were no statistically significant adjusted hazard ratios. Further, no significant sex differences were observed in the fully adjusted models.

CONCLUSION

This study supports that induction of labor through oxytocin administration does not increase the risk of autism spectrum disorder in the child. Our international comparison of 2 countries with differences in clinical practice regarding oxytocin administration for induction and/or augmentation suggests that previous studies reporting a significant association were likely confounded by the underlying indication for the induction.

Prenatal exposure to legacy PFAS and neurodevelopment in preschool-aged Canadian children: The MIREC cohort

BACKGROUND

Exposure to perfluoroalkyl substances (PFAS) has been shown to be neurotoxic in experimental studies, but epidemiological evidence linking prenatal PFAS exposure to child neurodevelopment is equivocal and scarce.

OBJECTIVE

To quantify associations between prenatal exposure to legacy PFAS and children's intelligence (IQ) and executive functioning (EF) in a Canadian pregnancy and birth cohort and to determine if these associations differ by child sex.

METHODS

We measured first-trimester plasma concentrations of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexanesulfonic acid (PFHxS) in the Maternal-Infant Research on Environmental Chemicals (MIREC) study and assessed children's full-scale (n = 522), performance (n = 517), and verbal (n = 519) IQ using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III). Children's working memory (n = 513) and ability to plan and organize (n = 514) were assessed using a parent-reported questionnaire, the Behavior Rating Inventory of Executive Function - Preschool Version (BRIEF-P). We quantified associations between individual log2-transformed PFAS exposure and children's IQ and EF using multiple linear regression analyses and evaluated effect modification by child sex. We also used Repeated Holdout Weighted Quantile Sum (WQS) regression models with effect modification by child sex to quantify the effect of combined exposure to all three PFAS chemicals on IQ and EF. All models were adjusted for key sociodemographic characteristics.

RESULTS

Geometric mean plasma concentrations (IQR) for PFOA, PFOS and PFHxS were 1.68 (1.10-2.50), 4.97 (3.20-6.20) and 1.09 (0.67-1.60) μg/L respectively. We found evidence of effect modification by child sex in all models examining performance IQ (p < .01). Specifically, every doubling of PFOA, PFOS, and or PFHxS was inversely associated with performance IQ, but only in males (PFOA: B = -2.80, 95% CI: -4.92, -0.68; PFOS: B = -2.64, 95% CI: -4.77, -0.52; PFHxS: B = -2.92, 95% CI: -4.72, -1.12). Similarly, every quartile increase in the WQS index was associated with poorer performance IQ in males (B = -3.16, 95% CI: -4.90, -1.43), with PFHxS contributing the largest weight to the index. In contrast, no significant association was found for females (B = 0.63, 95% CI: -0.99, 2.26). No significant associations were found for EF in either males or females.

CONCLUSIONS

Higher prenatal PFAS exposure was associated with lower performance IQ in males, suggesting that this association may be sex- and domain-specific.

Early-life exposure to a mixture of organophosphate esters and child behavior

Organophosphate esters (OPEs), widely used as flame retardants and plasticizers for commercial and residential purposes, are suspected of being neurotoxic. We aimed to assess exposure to an OPE mixture in early life and its relationship to parent-reported child behavior. We measured urinary concentrations of three OPE metabolites, bis-2-chloroethyl phosphate (BCEP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), and diphenyl phosphate (DPHP), at pregnancy (16 and 26 weeks of gestation and delivery) and postnatal time points (ages 1, 2, 3, and 5 years) in the Health Outcomes and Measures of the Environment Study, a longitudinal pregnancy and birth cohort in Cincinnati, Ohio, USA (enrolled 2003-2006, n = 219). We used latent variable analysis in structural equations models and quantile g-computation to investigate associations of a mixture of the three OPE metabolites with parent-reported child behaviors at 3 and 8 years, measured using the Behavioral Assessment System for Children, Second Edition. Higher log-transformed urinary OPE latent variable values at 16 weeks were associated with fewer externalizing problem behaviors (ß = -5.74; 95% CI = -11.24, -0.24) and fewer overall behavioral problems at age 3 years (ß = -5.26; 95% CI = -10.33, -0.19), whereas having higher OPEs at delivery was associated with poorer overall behavioral problems at age 3 years (ß = 2.87; 95% CI = 0.13, 5.61). OPE latent variable values at 16 weeks, 26 weeks, and delivery were not associated with child behavior at 8 years. However, higher OPE latent variable values at 3 years were associated with fewer externalizing behaviors at 8 years (ß = -2.62; 95% CI = -5.13, -0.12). The quantile g-computation estimates had directions largely consistent with the latent variable analysis results. Pregnancy and postnatal urinary OPE metabolite mixtures were associated with child internalizing, externalizing, and overall negative behaviors at 3 and 8 years, but we did not identify a consistent pattern in terms of the direction of the effects or a particularly sensitive time point.

Fluoride exposure and hypothyroidism in a Canadian pregnancy cohort

BACKGROUND

While fluoride can have thyroid-disrupting effects, associations between low-level fluoride exposure and thyroid conditions remain unclear, especially during pregnancy when insufficient thyroid hormones can adversely impact offspring development.

OBJECTIVES

We evaluated associations between fluoride exposure and hypothyroidism in a Canadian pregnancy cohort.

METHODS

We measured fluoride concentrations in drinking water and three dilution-corrected urine samples and estimated fluoride intake based on self-reported beverage consumption. We classified women enrolled in the Maternal-Infant Research on Environmental Chemicals Study as euthyroid (n = 1301), subclinical hypothyroid (n = 100) or primary hypothyroid (n = 107) based on their thyroid hormone levels in trimester one. We used multinomial logistic regression to estimate the association between fluoride exposure and classification of either subclinical or primary hypothyroidism and considered maternal thyroid peroxidase antibody (TPOAb) status, a marker of autoimmune hypothyroidism, as an effect modifier. In a subsample of 466 mother-child pairs, we used linear regression to explore the association between maternal hypothyroidism and child Full-Scale IQ (FSIQ) at ages 3-to-4 years and tested for effect modification by child sex.

RESULTS

A 0.5 mg/L increase in drinking water fluoride concentration was associated with a 1.65 (95 % confidence interval [CI]: 1.04, 2.60) increased odds of primary hypothyroidism. In contrast, we did not find a significant association between urinary fluoride (adjusted odds ratio [aOR]: 1.00; 95%CI: 0.73, 1.39) or fluoride intake (aOR: 1.25; 95%CI: 0.99, 1.57) and hypothyroidism. Among women with normal TPOAb levels, the risk of primary hypothyroidism increased with both increasing water fluoride and fluoride intake (aOR water fluoride concentration: 2.85; 95%CI: 1.25, 6.50; aOR fluoride intake: 1.75; 95%CI: 1.27, 2.41). Children born to women with primary hypothyroidism had lower FSIQ scores compared to children of euthyroid women, especially among boys (B coefficient: -8.42; 95 % CI: -15.33, -1.50).

DISCUSSION

Fluoride in drinking water was associated with increased risk of hypothyroidism in pregnant women. Thyroid disruption may contribute to developmental neurotoxicity of fluoride.

Individual, Independent, and Joint Associations of Toxic Metals and Manganese on Hypertensive Disorders of Pregnancy: Results from the MIREC Canadian Pregnancy Cohort

BACKGROUND

Toxic metals, such as lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg), may be associated with a higher risk of gestational hypertension and preeclampsia, whereas manganese (Mn) is an essential metal that may be protective.

OBJECTIVES

We estimated the individual, independent, and joint associations of Pb, Cd, As, Hg, and Mn on the risk of developing gestational hypertension and preeclampsia in a cohort of Canadian women.

METHODS

Metal concentrations were analyzed in first and third trimester maternal blood (n=1,560). We measured blood pressure after 20 wk gestation to diagnose gestational hypertension, whereas proteinuria and other complications defined preeclampsia. We estimated individual and independent (adjusted for coexposure) relative risks (RRs) for each doubling of metal concentrations and examined interactions between toxic metals and Mn. We used quantile g-computation to estimate the joint effect of trimester-specific exposures.

RESULTS

Each doubling of third trimester Pb (RR=1.54; 95% CI: 1.06, 2.22) and first trimester blood As (RR=1.25; 95% CI: 1.01, 1.58) was independently associated with a higher risk of developing preeclampsia. First trimester blood As (RR=3.40; 95% CI: 1.40, 8.28) and Mn (RR=0.63; 95% CI: 0.42, 0.94) concentrations were associated with a higher and lower risk, respectively, of developing gestational hypertension. Mn modified the association with As such that the deleterious association with As was stronger at lower concentrations of Mn. First trimester urinary dimethylarsinic acid concentrations were not associated with gestational hypertension (RR=1.31; 95% CI: 0.60, 2.85) or preeclampsia (RR=0.92; 95% CI: 0.68, 1.24). We did not observe overall joint effects for blood metals.

DISCUSSION

Our results confirm that even low blood Pb concentrations are a risk factor for preeclampsia. Women with higher blood As concentrations combined with lower Mn in early pregnancy were more likely to develop gestational hypertension. These pregnancy complications impact maternal and neonatal health. Understanding the contribution of toxic metals and Mn is of public health importance. https://doi.org/10.1289/EHP10825.

Association between toxic metals, vitamin D and preterm birth in the Maternal-Infant research on environmental chemicals study

BACKGROUND

Toxic metals, like lead, are risk factors for preterm birth (PTB), but few studies have examined low levels found in most Canadians. Vitamin D, which may have antioxidant activity, protects against PTB.

OBJECTIVES

In this study, we investigated the impact of toxic metals (lead, mercury, cadmium and arsenic) on PTB and examined if maternal plasma vitamin D concentrations modify these associations.

METHODS

We investigated whether concentrations of metals in whole blood measured in early and late pregnancy were associated with PTB (<37 weeks) and spontaneous PTB in 1851 live births from the Maternal-Infant Research on Environmental Chemicals Study using discrete time survival analysis. We also investigated whether the risk of PTB was modified by first-trimester plasma 25-hydroxyvitamin D (25OHD) concentrations.

RESULTS

Of 1851 live births, 6.1% (n = 113) were PTBs and 4.9% (n = 89) were spontaneous PTB. A 1 μg/dL increase in blood lead concentrations during pregnancy was associated with an increased risk of PTB (relative risk [RR] 1.48, 95% confidence interval [CI] 1.00, 2.20) and spontaneous PTB (RR 1.71, 95% CI 1.13, 2.60). The risk was higher in women with insufficient vitamin D concentrations (25OHD <50 nmol/L) for both PTB (RR 2.42, 95% CI 1.01, 5.79) and spontaneous PTB (RR 3.04, 95% CI 1.15, 8.04). However, an interaction on the additive scale was not present. Arsenic was associated with a higher risk of PTB (RR 1.10, 95% CI 1.02, 1.19) and spontaneous PTB (RR 1.11, 95% CI 1.03, 1.20) per 1 μg/L.

CONCLUSIONS

Gestational exposure to low levels of lead and arsenic may increase the risk of PTB and spontaneous PTB; individuals with insufficient vitamin D may be more susceptible to the adverse effects of lead. Given our relatively small number of cases, we encourage testing of this hypothesis in other cohorts, especially those with vitamin D-deficient populations.

Urinary concentrations and determinants of glyphosate and glufosinate in pregnant Canadian participants in the MIREC study

BACKGROUND

Glyphosate is the most widely applied herbicide in agriculture. Glufosinate is a broad spectrum herbicide used to manage glyphosate-resistant weeds. Despite the widespread use of these herbicides, biomonitoring data - which inform risk assessment and management - are sparse.

OBJECTIVES

To identify determinants of urinary concentrations of these herbicides and their metabolites in pregnancy.

METHODS

We measured urinary concentrations of glyphosate, glufosinate, and their primary metabolites aminomethylphosphonic acid (AMPA) and 3-methylphosphinicopropionic acid (3-MPPA) in a single spot urine specimen collected during the first trimester of pregnancy from the Maternal-Infant Research on Environmental Chemicals (MIREC) study. MIREC recruited about 2000 pregnant women from 10 Canadian cities between 2008 and 2011. We used UItra-Performance Liquid Chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) with sensitive limits of detection to quantify analyte concentrations. We examined urinary concentrations according to maternal sociodemographics, sample collection characteristics, reported pesticide use, and consumption of fruits, vegetables, legumes, and grain products. We used ANOVA models with specific gravity-standardized chemical concentrations as the dependent variable to determine associations with maternal and sample determinants.

RESULTS

Among women with biobanked urine samples (n = 1829-1854), 74% and 72% had detectable concentrations of glyphosate and AMPA, respectively. In contrast, one and six percent of women had detectable concentrations of glufosinate and 3-MPPA, respectively. The specific gravity-standardized geometric mean (95% CI) concentrations of glyphosate and AMPA were 0.112 (0.099-0.127) μg/L and 0.159 (0.147-0.172) μg/L, respectively. We observed a dose-response relationship between consumption of whole grain bread and higher urinary glyphosate concentrations. Season of urine collection and self-reported pesticide use were not associated with increased concentrations of any analyte.

CONCLUSIONS

We detected glyphosate and AMPA in the majority of pregnant women from this predominantly urban Canadian cohort. Diet was a probable route of exposure.

Leaded aviation gasoline exposure risk and child blood lead levels

Lead-formulated aviation gasoline (avgas) is the primary source of lead emissions in the United States today, consumed by over 170,000 piston-engine aircraft (PEA). The U.S. Environmental Protection Agency (EPA) estimates that four million people reside within 500m of a PEA-servicing airport. The disposition of avgas around such airports may be an independent source of child lead exposure. We analyze over 14,000 blood lead samples of children (≤5 y of age) residing near one such airport-Reid-Hillview Airport (RHV) in Santa Clara County, California. Across an ensemble of tests, we find that the blood lead levels (BLLs) of sampled children increase in proximity to RHV, are higher among children east and predominantly downwind of the airport, and increase with the volume of PEA traffic and quantities of avgas sold at the airport. The BLLs of airport-proximate children are especially responsive to an increase in PEA traffic, increasing by about 0.72 μg/dL under periods of maximum PEA traffic. We also observe a significant reduction in child BLLs from a series of pandemic-related interventions in Santa Clara County that contracted PEA traffic at the airport. Finally, we find that children's BLLs increase with measured concentrations of atmospheric lead at the airport. In support of the scientific adjudication of the EPAs recently announced endangerment finding, this in-depth case study indicates that the deposition of avgas significantly elevates the BLLs of at-risk children.

Childhood urinary organophosphate esters and cognitive abilities in a longitudinal cohort study

The use of organophosphate esters (OPEs) as flame retardants, which has increased over the past two decades, raises concerns that OPEs may be harmful to humans, especially children. Animal studies and some human studies have reported that OPEs may adversely impact brain development, but few human studies evaluated OPE exposure during early childhood and neurodevelopmental outcomes. We aimed to fill this knowledge gap with the present study on urinary OPE metabolite concentrations at ages 1-5 years and cognitive abilities at 8 years. We used data of 223 children from the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort in Cincinnati, Ohio. The point estimates for bis-2-chloroethyl-phosphate (BCEP) and bis(1,3-dichloro-2-propyl)-phosphate (BDCIPP) in association with IQ tended to be small and positive, while the point estimates for diphenyl-phosphate (DPHP) were small and negative, with 95% CIs including the null. However, we did find that socioeconomic status (SES) variables modified associations between OPEs and child IQ, with adverse OPE-IQ associations being stronger in socioeconomically disadvantaged children than in others. We identified an additional 1- to 2-point decrease in Full Scale IQ for every log-unit increase in BDCIPP, BCEP, and DPHP among those with lower maternal education, non-white race, lower income, or living in more deprived neighborhoods. We observed similar results for the Perceptual Reasoning, Verbal Comprehension, and Working Memory Index Scores. We suspect that there is residual confounding related to socioeconomic disadvantage, which was not captured with the available SES variables typically used in epidemiologic studies.

The association between prenatal greenspace exposure and Autism spectrum disorder, and the potentially mediating role of air pollution reduction: A population-based birth cohort study

BACKGROUND

Autism spectrum disorder (ASD) incidence has increased in past decades. ASD etiology remains inconclusive, but research suggests genetic, epigenetic, and environmental contributing factors and likely prenatal origins. Few studies have examined modifiable environmental risk factors for ASD, and far fewer have examined protective exposures. Greenspace has been associated with positive child development, but very limited greenspace research has examined ASD risk or prenatal exposures. Only one ecological study in 2017 has evaluated the association between greenspace and ASD, observing protective benefits. Greenspace may have direct effects on ASD risk and indirect effects by reducing air pollution exposure, a growing suspected ASD risk factor.

OBJECTIVES

To measure the association between prenatal greenspace exposure and ASD risk and examine if reduced air pollution levels in areas of higher greenspace mediate this association.

METHODS

We linked a population-based birth cohort of all deliveries in Metro Vancouver, Canada, from 2004 to 2009, with follow-up to 2014. Diagnoses were based on Autism Diagnostic Observation Schedule and Autism Diagnostic Interview-Revised instruments. Greenspace was quantified as the average of the annual mean Normalized Difference Vegetation Index (NDVI) within a 250 m buffer of a residential postal code. Air pollutant exposures-particulate matter with a diameter less than 2.5 µm (PM_2.5), nitric oxide (NO), and nitrogen dioxide (NO₂)-were derived from previously developed and temporally adjusted land use regression models. We estimated air pollutant exposures as the mean concentration per month during pregnancy. We calculated odds ratios (ORs) using logistic regression per NDVI interquartile range (IQR) increase, adjusting for child sex, birth month and year, maternal age and birthplace, and neighborhood-level urbanicity and income. To estimate the health impact of greenspace on ASD at the population level, we used the logistic regression model and marginal standardization to derive risk differences (RDs). Lastly, to quantify the mediating effect of greenspace on ASD risk through air pollution reduction, we used marginal structural models and a potential outcomes framework to calculate marginal risk differences (RDs) to decompose the total effect of greenspace on ASD into natural direct and indirect effects.

RESULTS

Of 129,222 births, 1,921 (1.5 %) children were diagnosed with ASD. The adjusted OR for ASD per NDVI IQR (0.12) increase was 0.96 (95 % CI: 0.90, 1.02) in 250 m buffer zones and 0.94 (95 % CI: 0.89, 1.00) in 100 m buffer zones. On the additive scale, the adjusted RDs were null. Natural direct, natural indirect, and total effect RDs were null for PM_2.5, NO, and NO₂ mediation models.

CONCLUSION

Prenatal greenspace exposure was associated with reduced odds of ASD, but in the additive scale, this effect was null at the population level. No mediating effect was observed through reduced air pollution, suggesting that air pollution may act as a confounder rather than as a mediator.

Autism Risk and Perinatal Antibiotic Use

OBJECTIVES

Antibiotics are commonly administered during labor and delivery, and research has suggested that fetal exposure to antibiotics can increase risk for autism spectrum disorder (ASD). We assessed whether antibiotic exposure during labor and delivery increased the risk of ASD in the offspring.

METHODS

This retrospective cohort study included everyone who delivered a live singleton-term infant in British Columbia, Canada, between April 1, 2000, and December 31, 2014. This cohort included 569 953 deliveries. To examine the association among pregnant individuals being treated for the same indication, we studied a subcohort of those who tested positive for group B Streptococcus. Cox proportional hazards models were used to estimate unadjusted and adjusted hazard ratios in both cohorts. A sensitivity analysis was conducted using length of first stage of labor as a proxy measure for dose to assess for a dose-response relationship.

RESULTS

In this population-based study, antibiotic use during labor and delivery was not associated with an increased risk of ASD in offspring. The unadjusted and adjusted hazard ratios were 1.29 (95% confidence interval, 1.24-1.35) and 0.99 (0.94-1.04), respectively; and 1.07 (0.90-1.27) and 0.88 (0.74-1.05), respectively, in the group B Streptococcus-positive cohort. We observed no substantial difference in the association between antibiotic exposure and ASD depending on length of the first stage of labor.

CONCLUSIONS

Our findings suggest that concern for ASD should not factor into the clinical decision on whether to administer antibiotics during labor and delivery. Future research is needed to examine longer durations of prenatal antibiotic exposure.

Associations of maternal urinary arsenic concentrations during pregnancy with childhood cognitive abilities: The HOME study

Arsenic exposure during pregnancy may increase the risk for intellectual deficits in children, but limited data exist from prospective epidemiologic studies, particularly at low arsenic exposure levels. We investigated the association between prenatal maternal urinary arsenic concentrations and childhood cognitive abilities in the Health Outcomes and Measures of the Environment (HOME) Study. We used anion exchange chromatography coupled with inductively coupled plasma mass spectrometry detection to measure arsenic species content in pregnant women's urine. The summation of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) refers to ∑As. We assessed children's cognitive function (n = 260) longitudinally at 1-, 2-, and 3-years using Bayley Scales of Infant and Toddler Development, at 5 years using Wechsler Preschool and Primary Scale of Intelligence, and at 8 years using Wechsler Intelligence Scale for Children. We observed a modest decrease in mental development index and full-scale intelligence quotient at ages 3 and 5 years with each doubling of ∑As with estimated score (ß) differences and 95% confidence interval (CI) of -1.8 from -4.1 to 0.5 and -2.5 from -5.1 to 0.0, respectively. This trend was stronger and reached statistical significance among children whose mothers had lower iAs methylation capacity and low urinary arsenobetaine concentrations. Our findings suggest that arsenic exposure levels relevant to the general US population may affect children's cognitive abilities.

Blood metals and vitamin D status in a pregnancy cohort: A bidirectional biomarker analysis

Low 25-hydroxyvitamin D (25OHD), a biomarker of vitamin D status, is associated with reduced immune function and adverse pregnancy outcomes, such as preterm birth. Observational studies indicate that long-term, high level exposure to metals such as cadmium (Cd) and lead (Pb) can impact a person's vitamin D status. However, the directionality of the association is uncertain, particularly for low-level exposures. We used three distinct longitudinal data analysis methods to investigate cross-sectional, longitudinal and bidirectional relationships of Cd and Pb biomarkers with 25-hydroxyvitamin D (25OHD) in a Canadian pregnancy cohort. Maternal whole blood Cd and Pb and plasma 25OHD concentrations were measured in the 1st (n = 1905) and 3rd (n = 1649) trimester and at delivery (25OHD only, n = 1542). Our multivariable linear regression analysis showed weak inverse associations between Cd and 25OHD concentrations cross-sectionally and longitudinally while the latent growth curve models showed weak associations with Pb on the 25OHD intercept. In the bidirectional analysis, using cross lagged panel models, we found no association between 1st trimester metals and 3rd trimester 25OHD. Instead, 1st trimester 25OHD was associated with 9% (-15%, -3%) lower 3rd trimester Cd and 3% (-7, 0.1%) lower Pb. These findings suggest the 25OHD may modify metal concentrations in pregnancy and demonstrates the value of controlling for contemporaneous effects and the persistence of a biomarker over time, in order to rule out reverse causation.

Association between objective measures and parent-reported measures of child tobacco smoke exposure: A secondary data analysis of four trials

INTRODUCTION

Tobacco smoke exposure (TSE) harms children and adults. Studies of childhood TSE exposure often relies on parental reports, but may benefit from objective measures. The objective of our study was to study the relationship between reported and objective measures of TSE.

METHODS

We analyzed data from four intervention trials, conducted in clinical or community settings, to identify objective measures most closely associated with parent-reported measures and the optimal set of parent-reported measures for predicting objective measures. We also assessed whether there was a learning curve in reported exposure over time, and the importance of replicate biomarker measures.

RESULTS

Correlations between objective and parent-reported measures of child TSE were modest at best, ranging from zero to 0.41. Serum cotinine and urinary cotinine were most strongly associated with parental reports. Parental questions most closely related to biomarkers were number of cigarettes and home smoking rules; together these formed the best set of predictive questions. No trial included all objective measures and all questions, precluding definitive statements about relative advantages. Within-subject repeatability of biomarker measures varied across studies, suggesting that direct pilot data are needed to assess the benefit of replicate measurements.

CONCLUSIONS

Improvements in objective and parent-reported child exposure measurements are needed to accurately monitor child TSE, evaluate efforts to reduce such exposure, and better protect child health.

Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys' Intelligence

In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys' and girls' intelligence. We used data from 366 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children's full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride's neurotoxicity in boys.

Development and Validation of the Prevention of Toxic Chemicals in the Environment for Children Tool: A Questionnaire for Examining the Community's Knowledge of and Preferences Toward Toxic Chemicals and Children's Brain Development

Early-life exposures to toxic chemicals can adversely impact brain development. Understanding people's knowledge of the impact of toxic chemicals on brain development is critical to reduce widespread exposure to chemicals. Yet it is unknown what people know about risks of toxic chemicals and how to reduce exposures. We developed and validated the questionnaire, PRevention of Toxic chemicals in the Environment for Children Tool (PRoTECT), to examine people's knowledge and attitudes about the influence of toxic chemicals on child development. We used best practices for developing and validating scales. First, we drafted items to assess knowledge of the impact of toxic chemicals on brain development, levels of concern regarding exposures, and preferences for prevention of neurodevelopmental disorders. Second, we received feedback on item clarity from five focus groups consisting of 46 community participants. In addition, 17 experts completed a content validity scale for each item and provided qualitative feedback. We administered the revised 18-item questionnaire to 190 participants of child-bearing age for scale development, and using exploratory factor analysis, we found evidence for a four-factor model of PRoTECT, RMSR = 0.05, of which 16 of the 18 items had adequate content validity with loadings >0.40 on a derived factor. We discuss future directions and applications of PRoTECT.

Pollution and health: a progress update

The Lancet Commission on pollution and health reported that pollution was responsible for 9 million premature deaths in 2015, making it the world's largest environmental risk factor for disease and premature death. We have now updated this estimate using data from the Global Burden of Diseases, Injuriaes, and Risk Factors Study 2019. We find that pollution remains responsible for approximately 9 million deaths per year, corresponding to one in six deaths worldwide. Reductions have occurred in the number of deaths attributable to the types of pollution associated with extreme poverty. However, these reductions in deaths from household air pollution and water pollution are offset by increased deaths attributable to ambient air pollution and toxic chemical pollution (ie, lead). Deaths from these modern pollution risk factors, which are the unintended consequence of industrialisation and urbanisation, have risen by 7% since 2015 and by over 66% since 2000. Despite ongoing efforts by UN agencies, committed groups, committed individuals, and some national governments (mostly in high-income countries), little real progress against pollution can be identified overall, particularly in the low-income and middle-income countries, where pollution is most severe. Urgent attention is needed to control pollution and prevent pollution-related disease, with an emphasis on air pollution and lead poisoning, and a stronger focus on hazardous chemical pollution. Pollution, climate change, and biodiversity loss are closely linked. Successful control of these conjoined threats requires a globally supported, formal science-policy interface to inform intervention, influence research, and guide funding. Pollution has typically been viewed as a local issue to be addressed through subnational and national regulation or, occasionally, using regional policy in higher-income countries. Now, however, it is increasingly clear that pollution is a planetary threat, and that its drivers, its dispersion, and its effects on health transcend local boundaries and demand a global response. Global action on all major modern pollutants is needed. Global efforts can synergise with other global environmental policy programmes, especially as a large-scale, rapid transition away from all fossil fuels to clean, renewable energy is an effective strategy for preventing pollution while also slowing down climate change, and thus achieves a double benefit for planetary health.

0189 High Levels of Sleep Disturbance across Early Childhood Increases Cardiometabolic Disease Risk Index in Early Adolescence: Longitudinal Sleep Analysis Using the HOME Study

Introduction

Sleep is a predictor of cardiometabolic disease (CMD) risk, and new evidence links early childhood sleep to later CMD risk. This study examines the impact of early childhood sleep duration, bedtime timing, and sleep disturbance on a CMD risk score in early adolescence.

Methods

Within the Health Outcomes and Measures of Environment (HOME) Study, a prospective pregnancy and birth cohort study, we assessed sleep patterns among 346 children using the Children’s Sleep Habits Questionnaire from ages 2 to 8 years. We calculated cardiometabolic risk scores ate age 12 for 183 of these children from visceral adiposity area, blood pressure, fasting serum triglyceride, high density lipoprotein, leptin, and adiponectin concentrations. We used a group-based semi-parametric mixture model to identify distinct trajectories in sleep duration, bedtime timing, and sleep disturbance for the entire sample. We then examined the associations between sleep trajectories and CMD risk score using general linear models for children with a CMD risk score, using both an unadjusted model (no covariates) and an adjusted model (adjusting for child pubertal stage, child sex, duration of breastfeeding, household income, and maternal education).

Results

Three sleep trajectories emerged for bedtime timing (late timing, medium timing, and early timing) and for sleep disturbance (high, medium, and low), and two for sleep duration (high and low). In the unadjusted model, we found significant differences in CMD risk scores by trajectories of sleep disturbance. Children in the ‘high’ trajectory had higher CMD risk scores (Least Square Mean=1.51; 95% CI: 0.39, 2.64) than those in the ‘low’ trajectory (Least Square Mean =-0.51; 95% CI: -1.16, 0.15; p=.002) and ‘medium’ trajectory (Least Square Mean=-0.15; 95% CI: -1.14, 0.85; p=.03). These findings only approached significance after adjusting for covariates. No significant differences in CMD risk were observed for bedtime timing or total sleep time trajectories in the unadjusted or adjusted models.

Conclusion

In this cohort, parent-reported sleep disturbance in early childhood was associated with more adverse cardiometabolic profiles in early adolescence. Our findings suggest that trials to reduce CMD risk via sleep interventions – which have been conducted in adolescents and adults – may be implemented too late.

Support (If Any)

National Institute of Environmental Health Sciences grants PO1 ES11261, R01 ES014575, R01 ES020349, R01 ES027224, R01 ES025214.

Maternal fluoride exposure, fertility and birth outcomes: The MIREC cohort

OBJECTIVE

Fluoride exposure >1.5 mg/L from water has been associated with adverse pregnancy and birth outcomes. Little is known, however, about the effect of fluoride at levels consistent with water fluoridation (i.e., 0.7 mg/L) on pregnancy and birth outcomes. We examined the relationship between maternal fluoride exposure, fertility, and birth outcomes in a Canadian pregnancy cohort living in areas where municipal drinking water fluoride concentrations ranged from 0.04 to 0.87 mg/L.

METHODS

Using data from the Maternal-Infant Research on Environmental Chemicals (MIREC) study, we estimated fluoride exposure during pregnancy using three different metrics: (1) maternal urinary fluoride concentrations standardized for specific gravity (MUF_SG) and averaged across all three trimesters (N = 1566), (2) water fluoride concentration (N = 1370), and (3) fluoride intake based on self-reported consumption of water, coffee, and tea, adjusted for body weight (N = 1192). Data on fertility, birth weight, gestational age, preterm birth, and small-for-gestational age (SGA) were assessed. We used multiple linear regression to examine associations between fluoride exposure, birth weight and gestational age, and logistic regression to examine associations with fertility, preterm birth, and SGA, adjusted for relevant covariates.

RESULTS

Median (IQR) MUF_SG was 0.50 (0.33-0.76) mg/L, median water fluoride was 0.52 (0.17-0.64) mg/L, and median fluoride intake was 0.008 (0.003-0.013) mg/kg/day. MUF_SG, water fluoride concentrations, and fluoride intake were not significantly associated with fertility, birth weight, gestational age, preterm birth, or SGA. Fetal sex did not modify any of the associations.

CONCLUSION

Fluoride exposure during pregnancy was not associated with fertility or birth outcomes in this Canadian cohort.

A Benchmark Dose Analysis for Maternal Pregnancy Urine-Fluoride and IQ in Children

As a guide to establishing a safe exposure level for fluoride exposure in pregnancy, we applied benchmark dose modeling to data from two prospective birth cohort studies. We included mother-child pairs from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort in Mexico and the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort in Canada. Maternal urinary fluoride concentrations (U-F, in mg/L, creatinine-adjusted) were measured in urine samples obtained during pregnancy. Children were assessed for intelligence quotient (IQ) at age 4 (n = 211) and between six and 12 years (n = 287) in the ELEMENT cohort, and three to four years (n = 407) in the MIREC cohort. We calculated covariate-adjusted regression coefficients and their standard errors to assess the association of maternal U-F concentrations with children's IQ measures. Assuming a benchmark response of 1 IQ point, we derived benchmark concentrations (BMCs) and benchmark concentration levels (BMCLs). No deviation from linearity was detected in the dose-response relationships, but boys showed lower BMC values than girls. Using a linear slope for the joint cohort data, the BMC for maternal U-F associated with a 1-point decrease in IQ scores was 0.31 mg/L (BMCL, 0.19 mg/L) for the youngest boys and girls in the two cohorts, and 0.33 mg/L (BMCL, 0.20 mg/L) for the MIREC cohort and the older ELEMENT children. Thus, the joint data show a BMCL in terms of the adjusted U-F concentrations in the pregnant women of approximately 0.2 mg/L. These results can be used to guide decisions on preventing excess fluoride exposure in pregnant women.

The impact of clinical and population strategies on coronary heart disease mortality: an assessment of Rose's big idea

BACKGROUND

Coronary heart disease (CHD), the leading cause of death worldwide, has declined in many affluent countries but it continues to rise in industrializing countries.

OBJECTIVE

To quantify the relative contribution of the clinical and population strategies to the decline in CHD mortality in affluent countries.

DESIGN

Meta-analysis of cross-sectional and prospective studies.

DATA SOURCES

PubMed and Web of Science from January 1, 1970 to December 31, 2019.

METHOD

We combined and analyzed data from 22 cross-sectional and prospective studies, representing 500 million people, to quantify the relative decline in CHD mortality attributable to the clinical strategy and population strategy.

RESULT

The population strategy accounted for 48% (range = 19 to 73%) of the decline in CHD deaths and the clinical strategy accounted for 42% (range = 25 to 56%), with moderate inconsistency of results across studies.

CONCLUSION

Since 1970, a larger fraction of the decline in CHD deaths in industrialized countries was attributable to reduction in CHD risk factors than medical care. Population strategies, which are more cost-effective than clinical strategies, are under-utilized.

Comparing adolescent self staging of pubertal development with hormone biomarkers

OBJECTIVES

Physical examinations to characterize pubertal maturation may be unacceptable for children enrolled in research studies. Studies confirm the utility of pubertal self staging for research, but there has been limited comparison of self examination with hormone biomarkers. Our objective was to assess concordance of pubertal self staging with hormone biomarkers of puberty.

METHODS

Participants were enrolled in the Health Outcomes and Measures of the Environment Study, a longitudinal pregnancy and birth cohort study. At age 12 years, 139 females and 112 males completed pubertal self staging including breast and pubic hair development in females and pubic hair development in males. No clinical physical examination was performed. Hormone concentrations were measured in 102 females and 96 males including serum dehydroepiandrosterone sulfate, luteinizing hormone, and follicle-stimulating hormone in all; estradiol in females; and testosterone in males.

RESULTS

Estradiol was significantly associated with female breast stage, even when adjusted for BMI, with geometric least squares means (95%CI) of 13.2 (8.7, 20.2), 38.3 (29.9, 49.1), 59.4 (39.8, 88.6), and 81.2 (45.6, 144) pg/mL for breast stage 1-2, 3, 4, and 5, respectively. Testosterone was significantly associated with male pubic hair stage, with adjusted geometric least squares means (95%CI) of 37.6 (19.9, 71.1), 43.4 (27.7, 68.3), 126 (78.4, 203), 275 (146, 521), and 559 (237, 1319) ng/dL for pubic hair stage 1, 2, 3, 4, and 5, respectively.

CONCLUSIONS

Self assessed pubertal development was positively associated with hormonal biomarkers of puberty.

Direct LC-MS/MS and indirect GC-MS/MS methods for measuring urinary bisphenol A concentrations are comparable

BACKGROUND

Bisphenol A (BPA) is typically measured in urine using an indirect method that involves enzymatic deconjugation and extraction. In contrast, the direct method measures free and conjugated BPA concurrently and sums them to estimate urinary BPA concentrations. Statistical comparison of total BPA results using the direct and indirect methods is necessary to accurately interpret biomonitoring data for risk assessments.

OBJECTIVES

To compare urinary BPA concentrations estimated from the indirect and direct methods in duplicate first trimester urine samples collected from 1879 pregnant women from the MIREC Study.

METHODS

For the indirect method, we measured urinary BPA concentrations using GC-MS/MS. For the direct method, we summed free and conjugated BPA concentrations measured using LC-MS/MS. We evaluated deviation between the two methods using the Bland-Altman analysis in the total sample and stratified (1) by specific gravity and (2) at the limit of quantification (LOQ).

RESULTS

Median urinary BPA concentrations for the direct and indirect methods were 0.89 µg BPA equivalents/L and 0.81 µg/L respectively. Concentrations from the direct method were, on average, 8.6% (95% CI: 6.7%, 10.5%) higher than the indirect method in a Bland-Altman analysis. The percent differences between the two methods was 4.0% in urines with specific gravities < 1.02 (n = 1348, 72%) and 20.3% in urine with specific gravity ≥ 1.02. In values below the LOQ (n = 663, 35%), we observed smaller average percent deviation (4.8%) between the two methods but wider limits of agreement.

DISCUSSION

Results from this study, based on the largest statistically rigorous comparison of the direct and indirect methods of BPA measurement, contrast previous findings reporting that the indirect method underestimates total BPA exposure. The difference in urinary BPA concentrations we observed with the indirect and direct methods is unlikely to alter the interpretation of health outcome data.

Association of Epidural Analgesia During Labor and Delivery With Autism Spectrum Disorder in Offspring

IMPORTANCE

Evidence from studies investigating the association of epidural analgesia use during labor and delivery with risk of autism spectrum disorder (ASD) in offspring is conflicting.

OBJECTIVE

To assess the association of maternal use of epidural analgesia during labor and delivery with ASD in offspring using a large population-based data set with clinical data on ASD case status.

DESIGN, SETTING, AND PARTICIPANTS

This population-based retrospective cohort study included term singleton children born in British Columbia, Canada, between April 1, 2000, and December 31, 2014. Stillbirths and cesarean deliveries were excluded. Clinical ASD diagnostic data were obtained from the British Columbia Autism Assessment Network and the British Columbia Ministry of Education. All children were followed up until clinical diagnosis of ASD, death, or the study end date of December 31, 2016.

EXPOSURES

Use of epidural analgesia during labor and delivery.

MAIN OUTCOMES AND MEASURES

A clinical diagnosis of ASD made by pediatricians, psychiatrists, and psychologists with specialty training to assess ASD. Cox proportional hazards models were used to estimate the hazard ratio of epidural analgesia use and ASD. Models were adjusted for maternal sociodemographics; maternal conditions during pregnancy; labor, delivery, and antenatal care characteristics; infant sex; gestational age; and status of small or large for gestational age. A conditional logistic regression model matching women with 2 births or more and discordance in ASD status of the offspring also was performed.

RESULTS

Of the 388 254 children included in the cohort (49.8% female; mean gestational age, 39.2 [SD, 1.2] weeks; mean follow-up, 9.05 [SD, 4.3] years), 5192 were diagnosed with ASD (1.34%) and 111 480 (28.7%) were exposed to epidural analgesia. A diagnosis of ASD was made for 1710 children (1.53%) among the 111 480 deliveries exposed to epidural analgesia (94 157 women) vs a diagnosis of ASD in 3482 children (1.26%) among the 276 774 deliveries not exposed to epidural analgesia (192 510 women) (absolute risk difference, 0.28% [95% CI, 0.19%-0.36%]). The unadjusted hazard ratio was 1.32 (95% CI, 1.24-1.40) and the fully adjusted hazard ratio was 1.09 (95% CI, 1.00-1.15). There was no statistically significant association of epidural analgesia use during labor and delivery with ASD in the within-woman matched conditional logistic regression (839/1659 [50.6%] in the exposed group vs 1905/4587 [41.5%] in the unexposed group; fully adjusted hazard ratio, 1.07 [95% CI, 0.87-1.30]).

CONCLUSIONS AND RELEVANCE

In this population-based study, maternal epidural analgesia use during labor and delivery was associated with a small increase in the risk of autism spectrum disorder in offspring that met the threshold for statistical significance. However, given the likelihood of residual confounding that may account for the results, these findings do not provide strong supporting evidence for this association.

Secondhand tobacco smoke exposure among children under 5 years old: questionnaires versus cotinine biomarkers: a cohort study

OBJECTIVES

Cotinine is the gold standard to estimate prevalence of secondhand tobacco smoke (SHS) exposure, and assay limit of detection (LOD) cut-points are typically used regardless of age. Our aim was to compare the concordance between mother-reported SHS exposure and serum cotinine categorising children as exposed with the assay LOD or age-specific cut-points.

DESIGN

Data from the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort.

SETTING

Hospital or participants' homes.

PARTICIPANTS

389 pregnant women aged 18 years and older, between 13 and 19 weeks of gestation, living in a five-county region of the Cincinnati, Ohio metropolitan area, and with follow-up on their children at birth and ages 12, 24, 36 and 48 months.

PRIMARY AND SECONDARY OUTCOME MEASURES

Children's serum cotinine, mother-reported active smoking and SHS exposure were available at birth and during follow-up visits. We used Cohen's kappa index to assess concordance between maternal self-report and child's serum cotinine concentrations. We estimated optimal age-specific cut-points, their sensitivity-specificity and positive-negative predictive values with receiver operating characteristic curves.

RESULTS

Self-reported exposure and cotinine data were available for 280 women who gave birth to singleton child. When applying the assay LOD (0.015 ng/mL), concordance between maternal report and serum cotinine, without accounting for age, was below 0.23 at all times. When using age-specific cut-points (12 months: 0.11 ng/mL; 24 months: 0.08 ng/mL; 36 months: 0.05 ng/mL and 48 months: 0.04 ng/mL), concordance improved, being low at 12 months (0.39), moderate at 24 and 36 months (0.47 and 0.43) and high at 48 months (0.62).

CONCLUSIONS

Concordance between mother-reported SHS exposure among children under 5 years and serum cotinine improved considerably after applying the cohort-specific and age-specific cut-points. Future studies are necessary to verify these results.

Urinary phthalates and body mass index in preschool children: The MIREC Child Development Plus study

Childhood exposure to phthalates, a class of chemicals with known reproductive and developmental effects, has been hypothesized to increase the risk of obesity, but this association is not well understood in preschool children. We examined the association between urinary concentrations of phthalate metabolites and concurrently measured body mass index (BMI) and skinfolds among children between the ages of two and five years. We collected anthropometric measures and biomonitoring data on approximately 200 children enrolled in the Maternal-Infant Research on Environmental Chemicals Child Development Plus study. We measured 22 phthalate metabolites in children's urine and used the 19 metabolites detected in at least 40% of samples. Our primary outcome was BMI z-scores calculated using the World Health Organization growth standards. Skinfold z-scores were secondary outcomes. We used multivariable linear regression to evaluate the association between tertiles of phthalate concentrations and each anthropometric measure. We also used weighted quantile sum regression to identify priority exposures of concern. Our analytic sample included 189 singleton-born children with complete anthropometric data. Children with concentrations of the parent compound di-n-butyl phthalate (∑DnBP) in the third tertile had 0.475 (95% CI: 0.068, 0.883) higher BMI z-scores than those in the lower tertile. ∑DnBP was identified as a priority exposure in the weighted quantile sum regression BMI model. In this population of Canadian preschool aged children, we identified DnBP as a potential chemical of concern in regard to childhood obesity. Future research with serial phthalate measurements and anthropometric measurements in young children will help confirm these findings.

Per- and polyfluoroalkyl substance mixtures and gestational weight gain among mothers in the Health Outcomes and Measures of the Environment study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent chemicals commonly used in the production of household and consumer goods. While exposure to PFAS has been associated with greater adiposity in children and adults, less is known about associations with gestational weight gain (GWG).

METHODS

We quantified using mass spectrometry perfluorooctanoate (PFOA), perfluorooctanesulfonate (PFOS), perfluorohexanesulfanoate (PFHxS) and perfluorononanoate (PFNA) in maternal serum from 18 ± 5 weeks' gestation (mean ± standard deviation (std)) in a prospective pregnancy and birth cohort (2003-2006, Cincinnati, Ohio) (n = 277). After abstracting weight data from medical records, we calculated GWG from 16 ± 2 weeks' gestation (mean ± std) to the measured weight at the last visit or at delivery, rate of weight gain in the 2nd and 3rd trimesters (GWR), and total weight gain z-scores standardized for gestational age at delivery and pre-pregnancy BMI. We investigated covariate-adjusted associations between individual PFAS using multivariable linear regression; we assessed potential effect measure modification (EMM) by overweight/obese status (pre-pregnancy BMI<25 kg/m2 v. ≥25 kg/m2). Using weighted quantile sum regression, we assessed the combined influence of these four PFAS on GWG and GWR.

RESULTS

Each doubling in serum concentrations of PFOA, PFOS, and PFNA was associated with a small increase in GWG (range 0.5-0.8 lbs) and GWR (range 0.03-0.05 lbs/week) among all women. The association of PFNA with GWG was stronger among women with BMI≥25 kg/m2 (β = 2.6 lbs; 95% CI:-0.8, 6.0) than those with BMI<25 kg/m2 (β = -1.0 lbs; 95% CI:-3.8, 1.8; p-EMM = 0.10). We observed associations close to the null between PFAS and z-scores and between the PFAS exposure index (a combined summary measure) and the outcomes.

CONCLUSION

Although there were consistent small increases in gestational weight gain with increasing PFOA, PFOS, and PFNA serum concentrations in this cohort, the associations were imprecise. Additional investigation of the association of PFAS with GWG in other cohorts would be informative and could consider pre-pregnancy BMI as a potential modifier.

Predictors of Plasma Fluoride Concentrations in Children and Adolescents

Despite increasing concerns about neurotoxicity of fluoride in children, sources of fluoride exposure apart from municipal water fluoridation are poorly understood. We aimed to describe the associations of demographics, drinking water characteristics, diet, and oral health behaviors with plasma fluoride concentrations in U.S. children. We used data from 3928 6–19-year-olds from the 2013–2016 National Health and Nutrition Examination Survey. We used a 24-h dietary recall to estimate recent consumption of fluoridated tap water and select foods. We estimated the associations of fluoridated tap water, time of last dental visit, use of toothpaste, and frequency of daily tooth brushing with plasma fluoride concentrations. The participants who consumed fluoridated (≥0.7 mg/L) tap water (n = 560, 16%) versus those who did not had 36% (95% CI: 22, 51) higher plasma fluoride. Children who drank black or green tea (n = 503, 13%) had 42% higher plasma fluoride concentrations (95% CI: 27, 58) than non-tea drinkers. The intake of other foods and oral health behaviors were not associated with plasma fluoride concentrations. The consumption of fluoridated tap water and tea substantially increases plasma fluoride concentrations in children. Quantifying the contribution of diet and other sources of fluoride is critical to establishing safe target levels for municipal water fluoridation.

Associations between Urinary, Dietary, and Water Fluoride Concentrations among Children in Mexico and Canada

Fluoride, which may be toxic to the developing brain, is added to salt in Mexico and drinking water in Canada to prevent dental caries. We compared childhood urinary fluoride (CUF) concentrations in Mexico City and Canada to characterize patterns of fluoride exposure in these two populations. We also examined associations of CUF with dietary and water fluoride levels in Mexico City and Canada respectively. We included 561 children (ages 4–6; mean age 4.8 years) from the Programming Research in Obesity, Growth, Environment, and Social Stress (PROGRESS) cohort in Mexico City, and 645 children (ages 2–6; mean age 3.7 years) from the Maternal–Infant Research on Environmental Chemicals (MIREC) cohort in Canada. We applied Spearman correlations, T-tests, ANOVA or covariate-adjusted linear regression to examine associations of CUF (mg/L; adjusted for specific gravity) with demographics and dietary or water fluoride concentrations. We used Welch equivalence testing to compare means across cohorts. Mean (SD) CUF was equivalent (t = 4.26, p < 0.001) in PROGRESS: 0.74 (0.42) and fluoridated Canadian communities: 0.66 (0.47), but lower in non-fluoridated Canadian communities: 0.42 (0.31) (t = −6.37, p < 0.001). Water fluoride concentrations were significantly associated with CUF after covariate adjustment for age and sex in MIREC (B = 0.44, 95% CI: 0.30, 0.59, p < 0.001). In contrast, daily food and beverage fluoride intake was not associated with CUF in PROGRESS (p = 0.82). We found that CUF levels are comparable among children in Mexico City and fluoridated Canadian communities, despite distinct sources of exposure. Community water fluoridation is a major source of fluoride exposure for Canadian children.

A Benchmark Dose Analysis for Maternal Pregnancy Urine-Fluoride and IQ in Children

As a safe exposure level for fluoride in pregnancy has not been established, we used data from two prospective studies for benchmark dose modeling. We included mother-child pairs from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort in Mexico and the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort in Canada. Children were assessed for IQ at age 4 (n=211) and between 6 and 12 years (n=287) in the ELEMENT cohort and between ages 3 and 4 years (n=512) in the MIREC cohort. We calculated covariate-adjusted regression coefficients and their standard errors to explore the concentration-effect function for maternal urinary fluoride with children's IQ, including possible sex-dependence. Assuming a benchmark response of 1 IQ point, we derived benchmark concentrations (BMCs) of maternal urinary fluoride and benchmark concentration levels (BMCLs). No deviation from linearity was detected from the results of the two studies. Using a linear slope, the BMC for maternal urinary fluoride associated with a 1-point decrease in IQ scores of preschool-aged boys and girls was 0.29 mg/L (BMCL, 0.18 mg/L). The BMC was 0.30 mg/L (BMCL, 0.19 mg/L) when pooling the IQ scores from the older ELEMENT children and the MIREC cohort. Boys showed slightly lower BMC values compared with girls. Relying on two prospective studies, maternal urine-fluoride exposure at levels commonly occurring in the general population, the joint data showed BMCL results about 0.2 mg/L. These results can be used to guide decisions on preventing excess fluoride exposure in vulnerable populations.

Gestational Pesticide Exposure and Child Respiratory Health

BACKGROUND

Childhood wheeze may be related to pesticide exposure, and diet and genetics (Paroxonase; PON1) may modify the effects of exposure.

METHODS

We analyzed data from the HOME Study, a prospective pregnancy and birth cohort, to examine the association of gestational urinary organophosphate (OP) and pyrethroid (3PBA) metabolite concentrations with child wheeze, forced expiratory volume in one second (FEV1) at ages 4 and 5 years, and wheeze trajectory patterns through age 8 years.

RESULTS

Among 367 singletons, the frequency of wheeze ranged from 10.6% to 24.1% at each measurement age. OP and 3PBA metabolite concentrations were not associated with wheeze at 8 years or from birth to 8 years, but there were three significant interactions: (1) maternal daily fruit and vegetable consumption (less than daily consumption and increasing 3PBA was associated with wheeze at age 8 years, OR = 1.40), (2) maternal PON1-108 allele (CT/TT genotypes and high DE was associated with wheeze at age 8 years, OR = 2.13, 2.74) and (3) PON1192 alleles (QR/RR genotypes with higher diethylphosphate (DE) and dialkyl phosphate (DAP) were associated with wheeze at age 8 years, OR = 3.84). Pesticide metabolites were not consistently related to FEV1 or wheeze trajectory.

CONCLUSIONS

Gestational OP and 3PBA metabolites were associated with child respiratory outcomes in participants with maternal dietary and genetic susceptibility.

Associations Between Early Low-Level Tobacco Smoke Exposure and Executive Function at Age 8 Years

OBJECTIVE

To investigate whether exposure to tobacco smoke during early brain development is linked with later problems in behavior and executive function.

STUDY DESIGN

We studied 239 children in a prospective birth cohort. We measured tobacco exposures by caregiver report and serum cotinine 3 times during pregnancy and 4 times during childhood. We used linear regression to examine the association between prenatal and childhood serum cotinine concentrations and behavior (the Behavior Assessment System for Children-2) and executive function (the Behavior Rating Inventory of Executive Function) at age 8 years while adjusting for important covariates.

RESULTS

Neither prenatal nor child serum cotinine were associated with behavior problems measured by the Behavior Assessment System for Children-2. On the Behavior Rating Inventory of Executive Function, prenatal and childhood exposure was associated with poorer task initiation scores (B = 0.44; 95% CI, 0.03-0.85 and B = 0.69, 95% CI, 0.06-1.32 respectively). Additionally, in a subset of 208 children with nonsmoking mothers, prenatal exposure was associated with task initiation scores (B = 1.17; 95% CI, 0.47-1.87) and additional components of the metacognition index (eg, working memory, B = 1.20; 95% CI, 0.34-2.06), but not components of the behavioral regulation index.

CONCLUSIONS

Tobacco exposures during pregnancy (including low-level second-hand smoke) and childhood were associated with deficits in some domains of children's executive function, especially task initiation and metacognition. These results highlight that decreasing early exposure to tobacco smoke, even second-hand exposure, may support ideal brain functioning.

Gestational Exposures to Phthalates and Folic Acid, and Autistic Traits in Canadian Children

BACKGROUND

The etiology of autism spectrum disorder is poorly understood. Few studies have investigated the link between endocrine-disrupting chemicals and autistic traits. We examined the relationship between gestational phthalates and autistic traits in 3- to 4-y-old Canadian children. We also investigated potential effect modification by sex and folic acid supplementation.

METHODS

We enrolled 2,001 women>18 years of age during the first trimester of pregnancy between 2008 and 2011 from 10 cities in Canada. At 3-4 years of age, 610 children underwent neuropsychological assessments including the Social Responsiveness Scale-II (SRS-2) as a measure of autistic traits and social impairment. We measured 11 phthalate metabolites in maternal first trimester urine samples and assessed folic acid supplementation from reported intakes. We estimated covariate-adjusted differences in SRS-2 T-scores with a doubling in phthalate concentrations in 510 children with complete data.

RESULTS

Mean total SRS T-score was 45.3 (SD=6.1). Children with higher gestational exposure to mono-n-butyl (MBP) and mono-3-carboxypropyl (MCPP) concentrations exhibited significantly higher total SRS T-scores, indicating greater overall social impairment, as well as higher scores on subdomains, indicating deficits in social cognition, social communication, social motivation, and restricted interests/repetitive behaviors. A doubling in MBP or MCPP concentrations was associated with 0.6 (95% CI: 0.1, 1.0) and 0.5 (95% CI: 0.1, 0.8) higher total SRS T-scores. Associations were consistently and significantly stronger in boys (βMBP=1.0; 95% CI: 0.4, 1.6; n=252) compared with girls (βMBP=0.1; 95% CI: -0.6, 0.7; n=258) and among children who had lower prenatal folic acid supplementation (<400μg/d) (βMBP=1.3; 95% CI: 0.4, 2.3; n=59) compared with those who had adequate folic acid supplementation (≥400μg/d) (βMBP=0.4; 95% CI: -0.1, 0.8; n=451).

CONCLUSIONS

Higher gestational concentrations of some phthalate metabolites were associated with higher scores of autistic traits as measured by the SRS-2 in boys, but not girls; these small size effects were mitigated by first trimester-of-pregnancy folic acid supplementation. https://doi.org/10.1289/EHP5621.