CHEAR Process and Procedures Development

The following are selected examples of the work completed to develop and test The Children’s Health Exposure Analysis Resource (CHEAR) operational and quality control procedures for submission and review of proposals, and coordination and standardization of laboratory and data exposure analyses. CHEAR invited four investigators with ongoing studies of children’s health to submit a proposal to pilot test addition of chemical exposure analysis to their study design. The pilot proposals were submitted to the CHEAR proposal review process, and the post approval process for laboratory and data analyses. The results of these pilot tests are included in our research highlights. The process for harmonization of trace element measurements among CHEAR laboratory hubs is also highlighted.

First trimester maternal exposures to endocrine disrupting chemicals and metals and fetal size in the Michigan Mother-Infant Pairs study

Jaclyn M. Goodrich, Mary E. Ingle, Steven E. Domino, Marjorie C. Treadwell, Dana C. Dolinoy, Charles Burant, John D. Meeker, Vasantha Padmanabhan

M-CHEAR: Michigan Children's Health Exposure Analysis Resource Laboratory Hub

Exposures to endocrine disrupting chemicals and metals are near ubiquitous worldwide, and their potential impact on children is a major public health concern. This pilot study was designed to characterize exposures to phthalates, phenols, and metals among pregnant women in the first trimester, and to examine associations with fetal biometrics and birth weight. Forty-one chemicals and elements were analyzed in urine from 56 mothers with full-term newborns from the Michigan Mother-Infant Pairs (MMIP) study. Bivariate analyses identified predictors of exposure biomarkers. Associations between birth weight, Fenton z-scores, and second trimester fetal biometrics with toxicants were examined via multivariable linear regression. An average of 30 toxicants were detected in maternal urine. Fast food consumption was associated with several phthalate metabolites, phenols and metals, and canned food consumption with bisphenol F (p<0.05). Mono (3-carboxypropyl) phthalate (MCPP) was significantly associated with higher birthweight and Fenton z-score while the opposite was observed for bisphenol S. Estimated femur length from ultrasonography was significantly inversely associated with arsenic, barium, and lead. While limited by sample size, this study is one of the first to evaluate birth outcomes with respect to emerging endocrine-disrupting chemicals and to examine associations between toxicants and fetal biometrics. Exposure assessment was provided by the National Institute of Environmental Health Sciences’ Children’s Health Exposure Analysis Resource (NIEHS CHEAR), a resource available to children’s studies with the goal of combining data across cohorts in an effort to characterize the impact of toxicants on child health from birth and beyond.

This work will be published in Journal of Developmental Origins of Health and Disease.

Urinary polycyclic aromatic hydrocarbon metabolite associations with biomarkers of inflammation, angiogenesis, and oxidative stress in pregnant women

Kelly K. Ferguson, Thomas F. McElrath, Gerry G. Pace, David Weller, Lixia Zeng, Subramaniam Pennathur, David E. Cantonwine, John D. Meeker

M-CHEAR: Michigan Children's Health Exposure Analysis Resource Laboratory Hub

Environmental exposure to polycyclic aromatic hydrocarbons (PAHs) is prevalent and may adversely impact pregnancy and development of the fetus. The purpose of this exploratory study was to examine urinary PAH metabolites in potential association with mediators of these outcomes. To do so, we measured a panel of 12 inflammatory, angiogenic, and oxidative stress biomarkers in plasma or urine from women in their third trimester of pregnancy (n = 200). Urinary PAH metabolites were highly detectable (>88%) in the study population, and most were higher in women who had lower education levels, higher body mass index, and who were African American. Some PAH metabolites showed consistent positive associations with the plasma inflammation marker C-reactive protein (CRP) and the urinary oxidative stress markers 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane. For example, an interquartile range increase in 2-hydroxynapthalene was associated with a 35% increase in CRP (95% confidence interval = -0.13, 83.2), a 14% increase in 8-OHdG (95% confidence interval = 0.59, 30.1), and a 48% increase in 8-isoprostane (95% confidence interval = 16.7, 87.0). These data suggest that exposure to PAHs may cause systemic changes during pregnancy that could lead to adverse pregnancy or developmental outcomes; however, these results should be corroborated in a larger study population.

This work is published in Environmental Science and Technology. 2017;51(8):4652-4660.

Urinary trace metals individually and in mixtures in association with preterm birth

Stephani S. Kim, John D. Meeker, Rachel Carroll, Shanshan Zhao, Michael J. Mourgas, Michael J. Richards, Max Aung, David E. Cantonwine, Thomas F. McElrath, Kelly K. Ferguson

M-CHEAR: Michigan Children's Health Exposure Analysis Resource Laboratory Hub

One in ten infants born in the United States is born preterm, or prior to 37 weeks gestation. Exposure to elevated levels of metals, such as lead and arsenic, has been linked to higher risk of preterm birth (PTB), but consequences of lower levels of exposure and less studied metals are unclear. We examined the associations between 17 urinary trace metals individually and in mixtures in relation to PTB. The LIFECODES birth cohort enrolled pregnant women at <15 weeks gestation at Brigham and Women's Hospital in Boston. We selected cases of PTB (n = 99) and unmatched controls (n = 291) and analyzed urine samples for a panel of trace metals (median: 26 weeks gestation). We used logistic regression models to calculate the odds ratio (OR) for PTB and subtypes of PTB based on presentation at delivery. Subtypes included spontaneous and placental PTB. We used elastic net (ENET) regularization to identify individual metals or pairwise interactions that had the strongest associations with PTB, and principal components analysis (PCA) to identify classes of exposures associated with the outcome. We observed increased odds of PTB (OR: 1.41, 95% Confidence Interval [CI]: 1.12, 1.78) in association with an interquartile range difference in urinary copper (Cu). We also observed an increased OR for selenium (OR: 1.33, 95% CI: 0.98, 1.81). ENET selected Cu as the most important trace metal associated with PTB. PCA identified 3 principal components (PCs) that roughly reflected exposure to toxic metals, essential metals, and metals with seafood as a common source of exposure. PCs reflecting essential metals were associated with increased odds of overall and spontaneous PTB. Maternal urinary copper in the third trimester was associated with increased risk of PTB, and statistical analyses for mixtures indicated that after accounting for correlation this metal was the most important statistical predictor of the outcome.

This work is published in Environment International. 2018;121 (Pt 1):582-590.

Perinatal lead (Pb) exposure’s effect on DNA methylation in human umbilical cord blood

Christine A. Rygiel, Jaclyn M. Goodrich, Wei Perng, Tamara R. Jones, Maritsa Solano, Howard Hu, Martha M. Tellez-Rojo, Karen E. Peterson, Dana C. Dolinoy

M-CHEAR: Michigan Children's Health Exposure Analysis Resource Laboratory Hub

Early life exposure to lead (Pb) can influence health through epigenetic modifications including DNA methylation. The aim of this study is to identify differentially methylated CpG positions associated with prenatal Pb exposure in human cord blood leukocytes. The Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project utilizes a series of longitudinal birth cohorts to examine the impact of Pb exposure during sensitive periods of development. In this study, we selected 97 ELEMENT participants with archived umbilical cord blood samples for methylation analysis via the Infinium MethylationEPIC BeadChip, which quantifies total methylation at >850,000 CpG sites. Maternal blood lead levels (BLLs) at each trimester (T1: 6.56 ± 5.27 ug/dL; T2: 5.89 ± 4.83 ug/dL; T3: 6.20 ± 4.48 ug/dL), umbilical cord BLLs (4.82 ± 3.71 ug/dL) at birth, and patella (9.45 ± 9.96 ug/g) and tibia (7.19 ± 9.61 ug/g) bone Pb levels one-month post pregnancy were measured. Differentially methylated positions (DMPs) by Pb level were identified using linear regression, controlling for sex and estimated umbilical cord cell-type composition. We employed a false discovery rate of 5% (q<0.05) to identify DMPs associated with prenatal Pb exposure. We identified 143 DMPs associated with maternal BLLs during T1, 310 during T2, and 243 during T3. Two of the DMPs (in POMT2 and HIST4H4) were significantly associated with BLLs in all three trimesters. No statistically significant DMPs were identified in analyses with bone or umbilical cord blood lead levels. LRPath pathway analysis revealed >50 significant pathways enriched for differential methylation by maternal BLL in each trimester, including neurological system processes, chemical stimuli in sensory perception, and transmembrane receptor activities. Further studies are needed to quantify gene expression to help determine if methylation alterations are promoting transcriptomic alterations, as well as investigate if these findings are tissue-specific or persistent later in life.

This work will be presented at the 2019 Society of Toxicology Annual Meeting in Baltimore, Maryland.

Harmonization of trace element measurements in clinical matrices: the role of secondary reference materials and proficiency testing among the CHEAR laboratory network

Aubrey L. Galusha, Fida Khatib, Christopher Palmer, Patrick J. Parsons, CHEAR consortia

Wadsworth Center's Children's Health Exposure Assessment

Measurement harmonization among the laboratory hubs is essential to the success of the goal of combining studies within CHEAR. In late 2015, the Wadsworth Center Trace Elements Lab opened up the New York State Biomonitoring Proficiency Testing (PT) Program for Trace Elements to the other CHEAR labs with the goal of improved laboratory performance for trace element analysis of clinical matrices. In 2018, 27 laboratories are enrolled in this international program; thus providing evidence of harmonization of CHEAR with other biomonitoring laboratories. The PT Program operates with three challenges per year and 5 samples per challenge, for each of three matrices: urine, whole blood, and serum. Comparability among the CHEAR labs and with other biomonitoring labs is assessed based on data reported to and collated by PT Program staff. The Trace Elements Lab also produced two levels each of urine and whole blood samples, spiked with up to 25 trace elements, to serve as secondary reference materials for CHEAR and ECHO studies. The PT Program was leveraged to characterize the CHEAR reference materials 13 (whole blood) and 22 (urine) trace elements, such that robust targets and uncertainties could be assigned.