Research Hub

Background:
Respiratory distress is the leading cause of neonatal morbidity and mortality worldwide, and prenatal exposure to air pollution is associated with adverse long-term respiratory outcomes; however, the impact of prenatal air pollution exposure on neonatal respiratory distress has not been well studied.
Objectives:
We examined associations between prenatal exposures to fine particular matter (PM2.5) and nitrogen dioxide (NO2) with respiratory distress and related neonatal outcomes.
Methods:
We used data from the Maternal–Infant Research on Environmental Chemicals (MIREC) Study, a prospective pregnancy cohort (𝑛=2,001) recruited in the first trimester from 10 Canadian cities. Prenatal exposures to PM2.5 (𝑛=1,321) and NO2 (𝑛=1,064) were estimated using land-use regression and satellite-derived models coupled with ground-level monitoring and linked to participants based on residential location at birth. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for associations between air pollution and physician-diagnosed respiratory distress in term neonates in hierarchical logistic regression models adjusting for detailed maternal and infant covariates.
Results:
Approximately 7% of newborns experienced respiratory distress. Neonates received clinical interventions including oxygen therapy (6%), assisted ventilation (2%), and systemic antibiotics (3%). Two percent received multiple interventions and 4% were admitted to the neonatal intensive care unit (NICU). Median PM2.5 and NO2 concentrations during pregnancy were 8.81⁢ μ⁢g/m3 and 18.02 ppb, respectively. Prenatal exposures to air pollution were not associated with physician-diagnosed respiratory distress, oxygen therapy, or NICU admissions. However, PM2.5 exposures were strongly associated with assisted ventilation (OR per 1-μ⁢g/m3 increase in PM2.5=1.17; 95% CI: 1.02, 1.35), multiple clinical interventions (OR per 1⁢-μ⁢g/m3 increase in PM2.5=1.16; 95% CI: 1.07, 1.26), and systemic antibiotics, (OR per 1⁢-μ⁢g/m3 increase in PM2.5=1.12; 95% CI: 1.04, 1.21). These associations were consistent across exposure periods—that is, during prepregnancy, individual trimesters, and total pregnancy—and robust to model specification. NO2 exposure was associated with administration of systemic antibiotics (OR per 1-ppb increase in NO2=1.03; 95% CI: 1.00, 1.06).
Discussion:
Prenatal exposures to PM2.5 increased the risk of severe respiratory distress among term newborns. These findings support the development and prioritization of public health and prenatal care strategies to increase awareness and minimize prenatal exposures to air pollution.

Published Jan 25, 2024

Johnson, M., Mazur, L., Fisher, M., Fraser, W. D., Sun, L., Hystad, P., & Gandhi, C. K. (2024). Prenatal Exposure to Air Pollution and Respiratory Distress in Term Newborns: Results from the MIREC Prospective Pregnancy Cohort. Environmental Health Perspectives, 132(1). https://doi.org/10.1289/EHP12880

Air pollution is responsible worldwide for 9-12 million deaths annually. The major contributor to air pollution is particulate matter ≤2.5 µg per cubic meter of air (PM2.5) from vehicles, industrial emissions, and wildfire smoke. United States ambient air standards recommend annual average PM2.5 concentrations of ≤12 μg/m³ while European standards allow an average annual PM2.5 concentration of ≤20 μg/m3. However, significant PM2.5 cardiovascular and pulmonary health risks exist below these concentrations. Chronic PM2.5 exposure significantly increases major cardiovascular and pulmonary event risks in Americans by 8 to more than 20% for each 10-μg/m3 increase in PM2.5. PM2.5-induced increases in lipid peroxidation, induction of vascular inflammation and endothelial cell injury initiate and propagate respiratory diseases, coronary and carotid atherosclerosis. PM2.5 can cause atherosclerotic vascular plaque rupture and myocardial infarction and stroke by activating metalloproteinases. This article discusses PM2.5 effects on the cardiovascular and pulmonary systems, specific PM2.5 pathophysiologic mechanisms contributing to cardiopulmonary disease, and preventive measures to limit the cardiovascular and pulmonary effects of PM2.5.

Published Jan 1, 2024

Henning, R. J. (2024). Particulate Matter Air Pollution is a Significant Risk Factor for Cardiovascular Disease. Current Problems in Cardiology, 49(1), 102094. https://doi.org/10.1016/j.cpcardiol.2023.102094

Elevated exposure to ambient fine particulate matter (PM2.5) has been consistently associated with adverse outcomes on children’s test scores.1 However, previous research has often relied on relatively small or less representative samples and faced challenges in accounting for unobserved confounders at the individual level.2 In this cross-sectional study, we aimed to address these limitations by employing a 2-way fixed-effects model with a large administrative data set in North Carolina.

Published Oct 31, 2023

Lam, P. H., Zang, E., Chen, D., Liu, R., & Chen, K. (2023). Long-Term Exposure to Fine Particulate Matter and Academic Performance Among Children in North Carolina. JAMA Network Open, 6(10), e2340928–e2340928. https://doi.org/10.1001/JAMANETWORKOPEN.2023.40928

Approximately 25 million children ride buses to school in the United States. While school buses are the safest school transport from an accident perspective, older buses often expose students to high levels of diesel exhaust. Because these exposures can adversely impact health, which may lead to more missed school, the US Environmental Protection Agency (EPA) has spent millions of dollars to hasten the transition of school bus fleets to cleaner vehicles. Here, we leveraged the randomized allocation of the EPA’s 2012–2017 School Bus Rebate Program funding to causally assess the district attendance impacts of upgrading buses. Districts randomly selected for funding had greater attendance improvements after the lottery than unselected districts, resulting in over 350,000 estimated additional student days of attendance each year (95% confidence interval = −70,678 to 772,865) due to the use of EPA funds. Attendance improvements were greatest when the oldest buses were replaced and for districts with high ridership on applicant buses. Extrapolating our results nationwide, we expect that the replacement of all pre-2000 model year school buses would lead to more than 1.3 million additional student days of attendance per year (95% confidence interval = 247,443 to 2,406,511). Given the importance of attendance to educational success, we conclude that increasing the pace at which older, highly polluting buses are replaced positively impacts student attendance.

Published Apr 10, 2023

Pedde, M., Szpiro, A., Hirth, R., & Adar, S. D. (2023). Randomized design evidence of the attendance benefits of the EPA School Bus Rebate Program. Nature Sustainability, 6(7), 838–844. https://doi.org/10.1038/S41893-023-01088-7;SUBJMETA

Studies including ours showed that air pollution exposure was associated with increased risks of coronavirus disease (COVID-19) incidence and severity, including COVID-19–related hospitalizations. Most studies were conducted during the early pandemic when COVID-19 vaccination was not administered widely. Few studies have been conducted after the vaccination campaign. It is unknown how COVID-19 vaccination affects the adverse effects of air pollution exposure. This research letter reports findings assessing associations of long- and short-term exposures to three ambient air pollutants: nitrogen dioxide (NO2), fine particles (PM2.5), and ozone (O3) with COVID-19–related hospitalizations during July and August of 2021 when the Delta variant was the dominant strain, COVID-19 vaccines had been distributed over 7 months, and booster vaccines had not yet started; and effect modification with COVID-19 vaccination.

Published Jan 15, 2023

Chen, Z., Sidell, M. A., Huang, B. Z., Chow, T., Martinez, M. P., Lurmann, F., Gilliland, F. D., & Xiang, A. H. (2023). The Independent Effect of COVID-19 Vaccinations and Air Pollution Exposure on Risk of COVID-19 Hospitalizations in Southern California. Https://Doi.Org/10.1164/Rccm.202206-1123LE, 207(2), 218–221. https://doi.org/10.1164/RCCM.202206-1123LE

Growing evidence suggests that fine particulate matter (PM2.5) likely increases the risks of dementia, yet little is known about the relative contributions of different constituents. Here, we conducted a nationwide population-based cohort study (2000 to 2017) by integrating the Medicare Chronic Conditions Warehouse database and two independently sourced datasets of high-resolution PM2.5 major chemical composition, including black carbon (BC), organic matter (OM), nitrate (NO3−), sulfate (SO42−), ammonium (NH4+), and soil dust (DUST). To investigate the impact of long-term exposure to PM2.5 constituents on incident all-cause dementia and Alzheimer’s disease (AD), hazard ratios for dementia and AD were estimated using Cox proportional hazards models, and penalized splines were used to evaluate potential nonlinear concentration–response (C-R) relationships. Results using two exposure datasets consistently indicated higher rates of incident dementia and AD for an increased exposure to PM2.5 and its major constituents. An interquartile range increase in PM2.5 mass was associated with a 6 to 7% increase in dementia incidence and a 9% increase in AD incidence. For different PM2.5 constituents, associations remained significant for BC, OM, SO42−, and NH4+ for both end points (even after adjustments of other constituents), among which BC and SO42− showed the strongest associations. All constituents had largely linear C-R relationships in the low exposure range, but most tailed off at higher exposure concentrations. Our findings suggest that long-term exposure to PM2.5 is significantly associated with higher rates of incident dementia and AD and that SO42−, BC, and OM related to traffic and fossil fuel combustion might drive the observed associations.

Published Dec 27, 2022

Shi, L., Zhu, Q., Wang, Y., Hao, H., Zhang, H., Schwartz, J., Amini, H., van Donkelaar, A., Martin, R. v., Steenland, K., Sarnat, J. A., Caudle, W. M., Ma, T., Li, H., Chang, H. H., Liu, J. Z., Wingo, T., Mao, X., Russell, A. G., … Liu, P. (2022). Incident dementia and long-term exposure to constituents of fine particle air pollution: A national cohort study in the United States. Proceedings of the National Academy of Sciences, 120(1), e2211282119. https://doi.org/10.1073/PNAS.2211282119

Why does growing up in a poor neighborhood impede cognitive development? Although a large volume of evidence indicates that neighborhood poverty negatively affects child outcomes, little is known about the mechanisms that might explain these effects. In this study, we outline and test a theoretical model of neighborhood effects on cognitive development that highlights the mediating role of early life exposure to neurotoxic air pollution. To evaluate this model, we analyze data from a national sample of American infants matched with information on their exposure to more than 50 different pollutants known or suspected to harm the central nervous system. Integrating methods of causal inference with supervised machine learning, we find that living in a high-poverty neighborhood increases exposure to many different air toxics during infancy, that it reduces cognitive abilities measured later at age 4 by about one-tenth of a standard deviation, and that about one-third of this effect can be attributed to disparities in air quality.

Published Nov 30, 2022

Wodtke, G. T., Ard, K., Bullock, C., White, K., & Priem, B. (2022). Concentrated poverty, ambient air pollution, and child cognitive development. Science Advances, 8(48), 285. https://doi.org/10.1126/SCIADV.ADD0285

Background
Emerging studies have investigated the adverse health effects of PM2.5 using data from multiple cohorts, and results often are not generalizable across cohorts. We aimed to assess associations between prenatal PM2.5 and childhood cognition in two U.S. cohorts while accounting for between-site heterogeneity.
Methods
Analyses included 348 mother-child dyads enrolled in the dual site (New York City and Boston) PRogramming of Intergenerational Stress Mechanisms (PRISM) cohort and in the First Thousand Days of Life (FTDL) study (Northern Virginia) participating in the Environmental influences on Child Health Outcomes (ECHO) national consortium. Residential prenatal PM2.5 exposure was estimated using a validated satellite-based model and childhood cognition was measured using the NIH Toolbox Cognition Battery at three to eight years of age. We used a log-linear model applied to contingency tables formed by cross-classifying covariates by site to examine between-site heterogeneity using 3rd trimester PM2.5 exposure, age-corrected cognition scores, and covariates potentially causing heterogeneities. Multivariable linear regression models informed by the combinability analysis were used to estimate the coefficients and 95% confidence intervals (CIs) for the association between 3rd trimester PM2.5 exposure and age-corrected cognition scores (mean = 100, SD = 15).
Results
The log-linear model indicated that inter-study associations were similar between PRISM-NYC and FTDL, which were different from those in PRISM-Boston. Accordingly, we combined the data of PRISM-NYC and FTDL cohorts. We observed associations between 3rd trimester PM2.5 and cognition scores, findings were varying by site, childsex, and test. For example, a 1 μg/m3 increase of 3rd trimester PM2.5 was associated with −4.35 (95% CI = −8.73, −0.25) mean early childhood cognition scores in females in PRISM-Boston. In the pooled NYC + FTDL site, the association between PM2.5 and childhood cognition may be modified by maternal education and urbanicity.
Conclusions
We found associations between prenatal PM2.5 and impaired childhood cognition. Since multi-site analyses are increasingly conducted, our findings suggest the needed awareness of between-site heterogeneity.

Published Nov 1, 2022

Zhang, X., Liu, S. H., Geron, M., Mathilda Chiu, Y. H., Gershon, R., Ho, E., Huddleston, K., Just, A. C., Kloog, I., Coull, B. A., Enlow, M. B., Wright, R. O., & Wright, R. J. (2022). Prenatal exposure to PM2.5 and childhood cognition: Accounting for between-site heterogeneity in a pooled analysis of ECHO cohorts in the Northeastern United States. Environmental Research, 214, 114163. https://doi.org/10.1016/j.envres.2022.114163

The World Health Organization (WHO) recently released new guidelines for outdoor fine particulate air pollution (PM2.5) recommending an annual average concentration of 5 μg/m3. Yet, our understanding of the concentration-response relationship between outdoor PM2.5 and mortality in this range of near-background concentrations remains incomplete. To address this uncertainty, we conducted a population-based cohort study of 7.1 million adults in one of the world’s lowest exposure environments. Our findings reveal a supralinear concentration-response relationship between outdoor PM2.5 and mortality at very low (<5 μg/m3) concentrations. Our updated global concentration-response function incorporating this new information suggests an additional 1.5 million deaths globally attributable to outdoor PM2.5 annually compared to previous estimates. The global health benefits of meeting the new WHO guideline for outdoor PM2.5 are greater than previously assumed and indicate a need for continued reductions in outdoor air pollution around the world.

Published Sep 28, 2022

Scott Weichenthal et al. ,How low can you go? Air pollution affects mortality at very low levels.Sci. Adv.8,eabo3381(2022).DOI:10.1126/sciadv.abo3381

Objectives: This study explored the effects of short-term exposure to air pollution on hospital admissions for autism spectrum disorder (ASD), a proxy for symptom aggravation, among Korean children aged 5–14 years.

Design: Time-series study.

Setting, participants and outcome measures: We used data from the National Health Insurance Service (2011–2015). Daily concentrations of fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ozone (O3) levels in each region were used as exposures. ASD cases were defined based on a principal admission diagnosis of the claims data. We applied distributed lag non-linear models and a generalised difference-in-differences method to the quasi-Poisson models to estimate the causal effects of air pollution for up to 6 days. We also performed weighted quantile sum regression analyses to assess the combined effects of air pollution mixtures.

Results: PM2.5 levels at lag day 1, NO2 levels at lag day 5 and O3 levels at lag day 4 increased the risks of hospital admissions for ASD (relative risk (RR)=1.17, 95% CI 1.10 to 1.25 for PM2.5; RR=1.09, 95% CI 1.01 to 1.18 for NO2 and RR=1.03, 95% CI 1.00 to 1.06 for O3). The mean daily count of hospital admissions for ASD was 8.5, and it would be 7.3, 7.8 and 8.3 when the PM2.5 levels would be decreased by 10.0 µg/m3, NO2 by 10 ppb and O3 by 10 ppb, respectively. The weighted quantile sum index, constructed from PM2.5, NO2 and O3 levels, was associated with a higher risk of hospital admissions for ASD (RR 1.29, 95% CI 1.14 to 1.46), where NO2 was found to contribute to the effects most (the weight of 0.80).

Conclusions: These results emphasise that reduction of air pollution exposure should be considered for ASD symptom management, with important implications for the quality of life and economic costs.

Published Sep 1, 2022

Kim, K. N., Sohn, J. H., Cho, S. J., Seo, H. Y., Kim, S., & Hong, Y. C. (2022). Effects of short-term exposure to air pollution on hospital admissions for autism spectrum disorder in Korean school-aged children: a nationwide time-series study. BMJ Open, 12(9), e058286. https://doi.org/10.1136/BMJOPEN-2021-058286