Author ORCID Identifier

Date of Award


Degree Type


Degree Name

Master of Public Health (MPH)


Public Health

First Advisor

Ike S. Okosun PhD.

Second Advisor

Christina H. Fuller PhD.

Third Advisor

Ruiyan Luo PhD.


Background: Ambient PM2.5 was ranked the eighth leading risk for mortality in 2017, with a total of 2.94 million associated deaths globally. Numerous studies have reported associations between long-term exposure to PM2.5 and adverse health effects across a broad range of PM2.5 concentrations. However, there is little research on the effect of concentrations below the annual PM2.5 National Ambient Air Quality Standards (NAAQS) of 12 µg/m3.

Objective: Our objective was to assess the association between the levels of ambient PM2.5 below NAAQS and chronic obstructive pulmonary disease (COPD), asthma, myocardial infraction (MI) as captured by hospital admissions; emergency department visits; and mortality.

Methods: We conducted a cross-sectional study on 2014 data from 265 counties of 27 States of the United States (US) retrieved from the Environmental Public Health Tracking Network (EPHTN) of the Centers for Disease Control and Prevention (CDC). We used linear and multiple linear regression models to assess the association using SAS software.

Results: At levels below 12 µg/m3, controlling for heat index, a 1-unit change in annual PM2.5 concentrations was linked with an increase of 2.97 (95%CI: 1.32, 6.69)-unit in COPD hospitalizations, a decrease of 0.95 (95%CI: 0.90, 0.99)-unit in COPD EDV, an increase of 2.75 (95%CI: 1.21, 6.23)-unit in asthma hospitalizations, and an increase of 2.83 (95%CI: 1.34, 5.93)-unit in asthma EDV. Additionally, long-term exposure to PM2.5 was still associated with some outcomes when concentrations were gradually lowered to level below a 9 µg/m3 threshold.

Conclusion: Our results showed the association between long-term exposure to PM2.5 and COPD, asthma, and MI for PM2.5 levels below 12.0 µg/m3. Our findings provide evidence of increase health risk below current regulatory standards.