Background: Children may have differing susceptibility to ambient air pollution concentrations depending on various background characteristics of the children. Methods: Using emergency department (ED) data linked with birth records from Atlanta, Georgia, we identified ED visits for asthma or wheeze among children 2 to 16 years of age from 1 January 2002 through 30 June 2010 (n = 109,758). We stratified by preterm delivery, term low birth weight, maternal race, Medicaid status, maternal education, maternal smoking, delivery method, and history of a bronchiolitis ED visit. Population-weighted daily average concentrations were calculated for 1-hour maximum carbon monoxide and nitrogen dioxide; 8-hour maximum ozone; and 24-hour average particulate matter less than 10 microns in diameter, particulate matter less than 2.5 microns in diameter (PM<inf>2. 5</inf>), and the PM<inf>2. 5</inf> components sulfate, nitrate, ammonium, elemental carbon, and organic carbon, using measurements from stationary monitors. Poisson time-series models were used to estimate rate ratios for associations between 3-day moving average pollutant concentrations and daily ED visit counts and to investigate effect-measure modification by the stratification factors. Results: Associations between pollutant concentrations and asthma exacerbations were larger among children bom preterm and among children bom to African American mothers. Stratification by race and preterm status together suggested that both factors affected susceptibility. The largest estimated effect size (for an interquartile range increase in pollution) was observed for ozone among preterm births to African American mothers: rate ratio = 1.138 (95% confidence interval = 1.077-1.203). In contrast, the rate ratio for the ozone association among full-term births to mothers of other races was 1.025 (0.970-1.083). Conclusions: Results support the hypothesis that children vary in their susceptibility to ambient air pollutants.

BACKGROUND: Because ambient air pollution exposure occurs as mixtures, consideration of joint effects of multiple pollutants may advance our understanding of the health effects of air pollution. METHODS: We assessed the joint effect of air pollutants on pediatric asthma emergency department visits in Atlanta during 1998-2004. We selected combinations of pollutants that were representative of oxidant gases and secondary, traffic, power plant, and criteria pollutants, constructed using combinations of criteria pollutants and fine particulate matter (PM2.5) components. Joint effects were assessed using multipollutant Poisson generalized linear models controlling for time trends, meteorology, and daily nonasthma upper respiratory emergency department visit counts. Rate ratios (RRs) were calculated for the combined effect of an interquartile range increment in each pollutant's concentration. RESULTS: Increases in all of the selected pollutant combinations were associated with increases in warm-season pediatric asthma emergency department visits (eg, joint-effect RR = 1.13 [95% confidence interval = 1.06-1.21] for criteria pollutants, including ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and PM2.5). Cold-season joint effects from models without nonlinear effects were generally weaker than warm-season effects. Joint-effect estimates from multipollutant models were often smaller than estimates based on single-pollutant models, due to control for confounding. Compared with models without interactions, joint-effect estimates from models including first-order pollutant interactions were largely similar. There was evidence of nonlinear cold-season effects. CONCLUSIONS: Our analyses illustrate how consideration of joint effects can add to our understanding of health effects of multipollutant exposures and also illustrate some of the complexities involved in calculating and interpreting joint effects of multiple pollutants. Copyright © 2014 by Lippincott Williams & Wilkins.

Serum concentrations of PBDEs were measured using gas chromatography-tandem mass spectrometry in 80 children aged 15-71 months. Demographic and behavioral data were collected on parental questionnaires; a research nurse recorded anthropometric measures and insurance status. For a subset of children (n = 17), PBDEs were measured in house dust and child handwipes sampled during a home visit. In linear and Tobit regression, log-transformed PBDE congeners were modeled as a function of child characteristics, including neighborhood-level socioeconomic indicators. BDE congeners 47, 99, and 100 were highly correlated and summed for analysis; BDE-153 was examined individually. PBDE serum concentrations were associated with socioeconomic factors; for example, a $20,000 increase in median household income in a child's ZIP code was associated with a 34% decrease (95%CI = 14-49%) in BDE-153 and a 26% decrease (95%CI = 6-42%) in -BDE-47,-99,-100. Lower body-mass index (BMI) z-score and household smoking were strong predictors of higher BDE-153 levels. Among children who participated in a home visit, serum PBDE was positively correlated with handwipe PBDE (Spearman r -BDE-47, -99, -100 = 0.48, p = 0.09), but not dust PBDE. Results indicate socioeconomic factors and BMI are strong predictors of serum PBDE levels among young children. PBDEs measured on handwipes are more predictive of serum PBDE levels than vacuum-collected dust.

Background: Estimating the health effects of ambient air pollutant mixtures is necessary to understand the risk of real-life air pollution exposures. Methods: Pediatric Emergency Department (ED) visit records for asthma or wheeze (n = 148,256), bronchitis (n = 84,597), pneumonia (n = 90,063), otitis media (n = 422,268) and upper respiratory tract infection (URI) (n = 744,942) were obtained from Georgia hospitals during 2002–2008. Spatially-contiguous daily concentrations of 11 ambient air pollutants were estimated from CMAQ model simulations that were fused with ground-based measurements. Using a case-crossover study design, odds ratios for 3-day moving average air pollutant concentrations were estimated using conditional logistic regression, matching on ZIP code, day-of-week, month, and year. Results: In multipollutant models, the association of highest magnitude observed for the asthma/wheeze outcome was with “oxidant gases” (O3, NO2, and SO2); the joint effect estimate for an IQR increase of this mixture was OR: 1.068 (95% CI: 1.040, 1.097). The group of “secondary pollutants” (O3 and the PM2.5 components SO4 2−, NO3−, and NH4+) was strongly associated with bronchitis (OR: 1.090, 95% CI: 1.050, 1.132), pneumonia (OR: 1.085, 95% CI: 1.047, 1.125), and otitis media (OR: 1.059, 95% CI: 1.042, 1.077). ED visits for URI were strongly associated with “oxidant gases,” “secondary pollutants,” and the “criteria pollutants” (O3, NO2, CO, SO2, and PM2.5). Conclusions: Short-term exposures to air pollution mixtures were associated with ED visits for several different pediatric respiratory diseases.

Background: Previous studies have reported that hyperthyroid and hypothyroid women experience menstrual irregularities more often compared with euthyroid women, but reasons for this are not well-understood and studies on thyroid hormones among euthyroid women are lacking. In a prospective cohort study of euthyroid women, this study characterised the relationship between thyroid hormone concentrations and prospectively collected menstrual function outcomes. Methods: Between 2004-2014, 86 euthyroid premenopausal women not lactating or taking hormonal medications participated in a study measuring menstrual function. Serum thyroid hormones were measured before the menstrual function study began. Women then collected first morning urine voids and completed daily bleeding diaries every day for three cycles. Urinary oestrogen and progesterone metabolites (estrone 3-glucuronide (E13G) and pregnanediol 3-glucuronide (Pd3G)) and follicle-stimulating hormone were measured and adjusted for creatinine (Cr). Results: Total thyroxine (T4) concentrations were positively associated with Pd3G and E13G. Women with higher (vs lower) T4 had greater luteal phase maximum Pd3G (Pd3G = 11.7 μg/mg Cr for women with high T4 vs Pd3G = 9.5 and 8.1 μg/mg Cr for women with medium and low T4, respectively) and greater follicular phase maximum E13G (E13G = 41.7 ng/mg Cr for women with high T4 vs E13G = 34.3 and 33.7 ng/mg Cr for women with medium and low T4, respectively). Conclusions: Circulating thyroid hormone concentrations were associated with subtle differences in menstrual cycle function outcomes, particularly sex steroid hormone levels in healthy women. Results contribute to the understanding of the relationship between thyroid function and the menstrual cycle, and may have implications for fertility and chronic disease.

Background: Exposure to pollution from motor vehicles in early life may increase susceptibility to common pediatric infections. Methods: We estimated associations between residential exposure to primary fine particulate matter (PM2.5), nitrogen oxides (NOx), and carbon monoxide (CO) from traffic during the first year of life and incident pneumonia, bronchiolitis, and otitis media events by age two years in 22,441 children from the Kaiser Air Pollution and Pediatric Asthma Study, a retrospective birth cohort of children born during 2000-2010 and insured by Kaiser Permanente Georgia. Time to first clinical diagnosis of each outcome was defined using medical records. Exposure to traffic pollutants was based on observation-calibrated estimates from A Research LINE-source dispersion model for near surface releases (RLINE) and child residential histories. Associations were modeled using Cox proportional hazards models, with exposure as a continuous linear variable, a natural-log transformed continuous variable, and categorized by quintiles. Results: During follow-up 2,181 children were diagnosed with pneumonia, 5,533 with bronchiolitis, and 14,373 with otitis media. We observed positive associations between early-life traffic exposures and all three outcomes; confidence intervals were widest for pneumonia as it was the least common outcome. For example, adjusted hazard ratios for a 1-unit increase in NOx on the natural log scale (a 2.7-fold increase) were 1.19 (95% CI 1.12, 1.27) for bronchiolitis, 1.17 (1.12, 1.22) for otitis media, and 1.08 (0.97, 1.20) for pneumonia. Conclusions: Our results provide evidence for modest, positive associations between exposure to traffic emissions and common pediatric infections during early childhood.

INTRODUCTION: We investigated the extent to which associations of ambient air pollutant concentrations and birth weight varied across birth weight quantiles. METHODS: We analyzed singleton births ≥27 weeks gestation from 20-county metropolitan Atlanta with conception dates between 1 January 2002 and 28 February 2006 (N=273,711). Trimester-specific and total pregnancy average concentrations for 10 pollutants, obtained from ground observations that were interpolated using 12-km Community Multiscale Air Quality model outputs, were assigned using maternal residence at delivery. We estimated associations between interquartile range width (IQRw) increases in pollutant concentrations and changes in birth weight using quantile regression. RESULTS: Gestational age-adjusted associations were of greater magnitude at higher percentiles of the birth weight distribution. Pollutants with large vehicle source contributions (carbon monoxide, nitrogen dioxide, PM2.5 elemental carbon, and total PM2.5 mass), as well as PM2.5 sulfate and PM2.5 ammonium, were associated with birth weight decreases for the higher birth weight percentiles. For example, whereas the decrease in mean birthweight per IQRw increase in PM2.5 averaged over pregnancy was −7.8g (95% CI: −13.6g, - 2.0g), the quantile-specific associations were: 10th percentile −2.4g (−11.5g, 6.7g); 50th percentile −8.9g (−15.7g, −2.0g); and 90th percentile −19.3g (−30.6g, −7.9g). Associations for the intermediate and high birth weight quantiles were not sensitive to gestational age adjustment. For some pollutants we saw associations at the lowest quantile (10th percentile) when not adjusting for gestational age. CONCLUSIONS: Associations between air pollution and reduced birth weight were of greater magnitude for newborns at relatively heavy birth weights.

Background: A growing body of evidence has associated maternal exposure to air pollution with adverse effects on fetal growth; however, the existing literature is inconsistent. Objectives: We aimed to quantify the association between maternal exposure to particulate air pollution and term birth weight and low birth weight (LBW) across 14 centers from 9 countries, and to explore the influence of site characteristics and exposure assessment methods on between-center heterogeneity in this association. Methods: Using a common analytical protocol, International Collaboration on Air Pollution and Pregnancy Outcomes (ICAPPO) centers generated effect estimates for term LBW and continuous birth weight associated with PM10 and PM2.5 (particulate matter ≤ 10 and 2.5 μm). We used meta-analysis to combine the estimates of effect across centers (~ 3 million births) and used meta-regression to evaluate the influence of center characteristics and exposure assessment methods on between-center heterogeneity in reported effect estimates. Results: In random-effects meta-analyses, term LBW was positively associated with a 10-μg/m3 increase in PM10 [odds ratio (OR) = 1.03; 95% CI: 1.01, 1.05] and PM2.5 (OR = 1.10; 95% CI: 1.03, 1.18) exposure during the entire pregnancy, adjusted for maternal socioeconomic status. A 10-μg/m3 increase in PM10 exposure was also negatively associated with term birth weight as a continuous outcome in the fully adjusted random-effects meta-analyses (-8.9 g; 95% CI: -13.2, -4.6 g). Meta-regressions revealed that centers with higher median PM2.5 levels and PM2.5:PM10 ratios, and centers that used a temporal exposure assessment (compared with spatiotemporal), tended to report stronger associations. Conclusion: Maternal exposure to particulate pollution was associated with LBW at term across study populations. We detected three site characteristics and aspects of exposure assessment methodology that appeared to contribute to the variation in associations reported by centers.

Background: Numerous studies indicate caesarean delivery is associated with childhood asthma. Sex-specific associations were reported in four of these studies, and in all four studies, the estimated association between caesarean delivery and asthma was of greater magnitude among girls, although most report a lack of evidence of multiplicative interaction. Methods: We assessed potential effect modification by sex, on the additive and multiplicative scales, of the association between caesarean delivery and asthma by ages 2 through 6 in up to 17 075 racially diverse children from a retrospective birth cohort, the Kaiser Air Pollution and Pediatric Asthma (KAPPA) Study. We also conducted a random-effects meta-analysis, combining our sex-stratified results (using the odds ratio for compatibility with previous studies) with previously published results. Results: Adjusted risk differences for caesarean delivery and asthma in the KAPPA cohort were higher among girls than boys at every follow-up age. By age 5, caesarean delivery was associated with an absolute 3.8% (95% confidence interval [CI] 0.4%, 7.3%) higher asthma risk among girls and a 1.9% (95% CI −1.7, 5.4) higher risk among boys. The summary odds ratio from the meta-analysis for caesarean delivery and asthma among girls was 1.26 (95% CI 1.14, 1.39) and 1.08 (95% CI 0.98, 1.20) among boys (P = 0.036). Conclusions: Higher, but imprecise, estimates for females across five studies should motivate investigators to estimate sex-specific associations for caesarean delivery and asthma and to explore biological mechanisms or sex-dependent biases that could explain this possible heterogeneity.

Multipollutant indicators of mobile source impacts are developed from readily available CO, NOx, and elemental carbon (EC) data for use in air quality and epidemiologic analysis. Two types of outcome-based Integrated Mobile Source Indicators (IMSI) are assessed. The first is derived from analysis of emissions of EC, CO, and NOxsuch that pollutant concentrations are mixed and weighted based on emission ratios for both gasoline and diesel vehicles. The emission-based indicators (IMSIEB) capture the impact of mobile sources on air quality estimated from receptor models and their uncertainty is comparable to measurement and source apportionment uncertainties. The IMSIEBhave larger correlation between two different receptor sites impacted by traffic than single pollutants, suggesting they are better indicators of the local impact of mobile sources. A sensitivity analysis of fractions of pollutants in a two-pollutant mixture and the inclusion in an epidemiologic model is conducted to develop a second set of indicators based on health outcomes. The health-based indicators (IMSIHB) are weighted combinations of CO, NOx, and EC pairs that have the lowest P value in their association with cardiovascular disease emergency department visits, possibly due to their better spatial representativeness. These outcome-based, multipollutant indicators can provide support for the setting of multipollutant air quality standards and other air quality management activities. Implications: Integrated mobile source indicators (IMSI) were developed and assessed for use in air quality and epidemiologic analysis. IMSI contribute to fill the gap in the path towards a multipollutant air quality approach in two aspects: IMSI represent an innovative way to identify mixtures of pollutants based on outcomes and constitutes an alternative approach to assess multipollutant health effects. IMSI developed for mobile sources can be easily applied to other sources. Results can support the setting of multipollutant air quality standards. Supplemental Material: Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for materials showing the estimation of uncertainties using propagation of errors, comparison of source impacts from CMB and PMF and wind direction and speed for the Jefferson Street monitoring location in Atlanta.