Date of Award


Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Nicole Deziel


Background: Exposures to certain metals are associated with adverse birth outcomes, including inhibited fetal growth and congenital defects. Previous studies focused on metals such as lead and arsenic, and primarily assessed exposure using biological monitoring, which does not provide insights into sources. Examining exposure to metals via atmospheric pathways is challenging due to a lack of high-resolution air-pollution data. We applied a unique map of atmospheric metal pollution, derived from bio-indicator moss samples, as a screening tool to study neonatal health risks of atmospheric metal pollution in Portland, Oregon, a city of 640,000 people with several metal-emitting industrial sources.

Methods: We used previously collected data of metal concentrations measured in 346 moss samples in December 2013, to which an inverse-distance weighting scheme was applied to map ambient/environmental metal concentrations. Birth records for Portland live births (2008-2014) were obtained from the Oregon Health Authority. Exposure to atmospheric metals was assigned based on mother’s residential address. Metal exposure was evaluated continuously and by quartile. Associations were evaluated for six metals previously identified as metalloestrogens toxic to plant and animal life (arsenic, cadmium, chromium, cobalt, nickel, lead) and two birth outcomes (preterm (weeks), very preterm (weeks)) using logistic regression models with adjustment for birth characteristics and demographic variables.

Results: Results indicate statistically significant associations between chromium exposure and preterm birth (OR=1.10, 95% CI: 1.02, 1.19) and very preterm birth (OR=1.10, 95% CI: 1.01, 1.19). Stratifying metal exposure by quartiles found some evidence of a dose-response effect for arsenic, cobalt and lead, but not for other metals. Stratified analysis by mother’s race (white / non-white) finds that cadmium, chromium and lead are significant risk factors for very preterm birth among non-white women, but not among white women.

Conclusions: Results suggest that atmospheric metal exposure to chromium, measured via bio-indicator moss samples, is associated with an increased risk of preterm and very preterm birth. Exposure to cadmium, chromium and lead is a significant risk factor for very preterm birth among non-white women, indicating an effect due to race; this is an important result that requires further investigation. This novel exposure metric may be useful when bio-monitoring and more invasive/expensive exposure metrics are not feasible.

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