Date of Award

January 2026

Document Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Daniel Carrión

Second Advisor

Sarah Lowe

Abstract

Wildfire activity has intensified across the contiguous United States, making smoke-attributable fine particulate matter (PM2.5) a growing feature of the national air quality landscape. Wildfire smoke PM2.5 is linked to adverse mental health outcomes, but its association with suicide mortality remains under-studied, and prior work has relied largely on single binary exposure definitions that may obscure how risk is structured. This study examined the association between wildfire smoke PM2.5 and suicide mortality across all 3,108 contiguous U.S. counties from 2006 to 2019 using a county-month panel with three-way fixed effects and five complementary monthly smoke metrics: two concentration-based (monthly mean, peak weekly mean) and three exceedance-based (nonzero smoke days, weeks ≥5 µg/m³, smoke-wave events). Three of the five metrics were significantly associated with higher suicide mortality in rural counties, with a 1 µg/m³ increase in monthly mean PM2.5 corresponding to 0.104 additional deaths per million person-months (95% CI: 0.023, 0.185); urban effects were null across all metrics. Subgroup analyses revealed metric-dependent vulnerability patterns: among women, associations surfaced across multiple metrics and strata, while among men, associations surfaced in rural counties with peak weekly smoke episodes. Nonviolent-method suicides aligned with monthly mean concentration and violent-method suicides with smoke-day frequency, though peak weekly mean was significant for both method groups. These findings indicate that exposure-metric choice can materially shape inference about the smoke–suicide relationship and that multi-metric frameworks can surface vulnerability profiles that single-metric designs may miss — a consideration increasingly relevant as wildfire seasons lengthen and smoke becomes a more persistent feature of U.S. ambient air.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 09/16/2027

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