Depression is a common mental disorder from which nearly one in five Americans suffer (CDC). Depression is also one of the most treatable mental health disorders and is treated by a wide variety of health care specialists including primary care providers. Because many people suffering from depression are frequently under- or mis-diagnosed, a rapid, reliable, and valid screening tool is necessary. The nine-item Patient Health Questionnaire scale (PHQ-9) is a self-assessment completed at primary care clinics that screens and assesses the severity of depressive symptoms. Previous research has established the PHQ-9 diagnostic validity, showing consistency even when an individual is retested (Rahman et al.).|Additionally, previous research has found that life events, physical health, and environment can increase depressive symptoms. Particulate Matter (PM) is an air pollutant that results from many sources including gasoline combustion and wildfire smoke (EPA). PM2.5 is Particulate Matter less than 2.5 micrometers that, when inhaled, can induce adverse health effects including exacerbating symptoms of depression. We examined the correlation between monthly PM2.5 exposure levels and symptoms of depression as measured by the PHQ-9 from patients from the University of Utah and the Intermountain health care systems from 2015-2019. We also investigate how PHQ-9 scores vary by an individual's education, gender, and race/ethnicity. Based on our findings, the average PHQ-9 score for participants was 9 (out of 27), which corresponds with mild depression. We also found that individuals with marginalized identities had higher PHQ-9 scores compared to more socially privileged groups. Additionally, we found that monthly county PM2.5 concentrations showed a small positive correlation with PHQ-9 scores, however more research needs to be completed to investigate this relationship.