Dissertation/Thesis Abstract

Evaluating Effects of Environmental Exposure on Health Outcomes of Children
by Ebisu, Keita, Ph.D., Yale University, 2012, 133; 3535399
Abstract (Summary)

Environmental exposures can cause adverse health outcomes; increasing the risk of mortality or hospital admissions, or triggering asthma symptoms. In general, children are often more likely to be affected by those exposures, because children breathe more air relative to their size than adults do, typically spend more time outside than adults, and can be disproportionately affected by environmental contaminants as their immune defenses are not fully developed. Therefore, it is important to deepen the current understanding of environmental exposure and children's health. This dissertation examined the effects of several environmental exposures on children.

The first chapter investigated how urbanicity near a family's residence is associated with severity of wheeze symptoms among infants, using Connecticut asthma cohort data for 1996-1998. I found that urban land-use was associated with severity of wheeze symptoms in infants: a 10% increase in urban land-use within 1,540m of an infant's residence was associated with 1.09-fold increased risk of wheeze severity (95% confidence interval, 1.02-1.16). Findings indicate that health effect estimates for urbanicity incorporate some effects of traffic-related emissions, but also involve other factors, which may include differences in housing characteristics or baseline healthcare status.

The second project explored whether birth weight at term is affected by particulate matter ≤2.5μm (PM2.5), PM2.5 chemical components, particulate matter ≤10μm (PM10) and gaseous pollutants. The number of studies investigating air pollutants and birth outcomes is growing. Limited studies, however, are available, which explored PM2.5 chemical components' effect on birth outcomes. I estimated the risk of low birth weight by county-level averages of air pollutant exposure using birth certificate data in the northeastern and mid-Atlantic U.S. in 2000-2007. I found that risk increased 4.9% (3.4-6.5%), 4.7% (3.2-6.2%), 5.7% (2.7-8.8%) and 5.0% (3.1-7.0%) per interquartile range increase of PM2.5 aluminum, elemental carbon, nickel, and titanium, respectively. Findings indicate that some PM2.5 components may be more harmful than others.

The third project also investigated gaseous pollutants, PM10, PM2.5, and PM2.5 chemical components' effect on birth weight, but focused on issues of different methods to assign exposure and the implications of choice of buffer sizes. Spatial heterogeneity varies by pollutant, and exposure misclassification is a key challenge in environmental epidemiology. Using Connecticut birth certificate data for 2000-2006, I investigated the association between each pollutant and birth weight using various buffer sizes, including a buffer size I calculated in a systematic way for each pollutant. I found that exposure to NO2, SO2, PM10, PM2.5, and PM2.5 chemical components of ammonium ion, chlorine, elemental carbon, nitrate, organic carbon matter, and sulfate were associated with lower birth weight, based on analysis using the systematically derived buffers. Results indicate that different exposure metrics may be needed for different pollutants.

The results from these projects indicate that environmental exposures affect children's health. Findings could be used by decision makers to protect children's health from environmental conditions, and lay the foundation for future studies and development of statistical approaches.

Indexing (document details)
Advisor: Bell, Michelle
Commitee: Belanger, Kathleen, Holford, Theodore, Leaderer, Brian
School: Yale University
Department: Forestry and Environmental Studies
School Location: United States -- Connecticut
Source: DAI-B 74/05(E), Dissertation Abstracts International
Subjects: Environmental Health, Public health, Epidemiology
Keywords: Air pollution, Children's health, Low birth weight, Particulate matter
Publication Number: 3535399
ISBN: 978-1-267-85679-1
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