Date of Award

January 2024

Document Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Kai Chen

Abstract

A growing body of literature is finding that air pollution exposure may contribute to disease onset of certainbrain disorders, including mental disorders such as depression, through mechanisms of neuroinflammation and oxidative stress1. However, even as there is increasing attention on the impacts of air pollution and mental illnesses, most studies focus on mental illness outcomes that might not represent severe or life-threatening symptoms (such as self-harm)2–7 , while a majority of studies focused on intentional self-harm assess the relationship between short-term air pollution exposure (as opposed to chronic and cumulative exposure) and self-harm outcomes8–13 . Given the barriers to treatment that some populations face, choosing an extreme outcome such as intentional self-harm to study the mental health impacts of long-term air pollution exposure may reveal more nuanced understandings of the detrimental impacts of air pollution, but few studies have taken this approach. To the best of our knowledge, this is the first prospective cohort study of an adult population that investigates the impacts of ambient fine particulate matter pollution (PM2.5 ) exposure on risk of intentional self-harm. We observed a statistically significant 37% (95%CI: 15-64%), 43% (95%CI: 18-74%), 54% (95%CI: 24-92%) increased risk of intentional self-harm for participants living in areas with PM2.5 concentrations in the 2nd quartile, 3rd quartile, and 4th quartile, respectively (relative to the 1st quartile of ambient PM2.5 , all p-values <0.001), after adjusting for potential confounding variables. The exposure-response curve appears mostly linear for PM2.5 concentrations above and below 10μg/m3 , with a steeper slope below 10μg/m3 , and the curve potentially suggests a non-linear relationship around 10 μg/m3 . Our results show that long-term exposure to ambient PM2.5 concentrations is associated with increased risk of inpatient intentional self-harm. This evidence suggests that long-term air pollution exposure may increase the risk of severe clinical outcomes of poor mental health, regardless of the type of mental illness or a formal diagnosis of mental illness. These findings have implications for population wellbeing - especially in contexts of accelerating urban development - in populations that face the burden of disproportionate air pollution, those at-risk of or experiencing poor mental health, and those suffering from a lack of adequate mental health and wellbeing services. Climate mitigation and adaptation policy and efforts to reduce exposure to air pollution should be considered in relation to mental health and wellbeing planning and services.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 05/07/2026

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