Graduation Year


Date of Submission


Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts


Environment, Economics, and Politics (EEP)

Second Department

Environmental Analysis

Reader 1

Katie Purvis-Roberts

Reader 2

Franck Fu


The concentration of three major air pollutants - PM2.5, ozone, and NO2 - during the years 2018 to 2022 were analyzed in Los Angeles County, California and Harris County, Texas to determine the extent to which proximity to highways impacts air quality. Los Angeles County is known for its poor air quality and its traffic congestion. Scientific studies about Harris County were lacking when it came to traffic-related emissions, as most of the documented air quality issues were reported from its petrochemical industry. The study tested for general trends in pollutant concentration in areas close to and away from the highway, which proved to be significantly different in most cases for both counties. PM2.5 was the only pollutant that exhibited concentrations above EPA standards, especially in Los Angeles County with a mean concentration of 12.7 μg/m^3 in areas close to the highway and a mean concentration of 11.4 μg/m^3 in areas away from the highway. Additionally, the study observed seasonal variations, which did not exhibit clear trends for each pollutant since the pollutants had different seasons in which concentrations were higher and lower. However, NO2 concentrations were higher during the winter months and lower during the summer months for both counties and at each distance. Most notably, Los Angeles County had overall higher concentrations of each pollutant regardless of the season and distance from the highway, which may be indicative of the air quality issue in the county. Overall, concentrations of pollutants were generally higher closer to highways than away, which means poor air quality disproportionately impacts those residing within close proximity of highways.

This thesis is restricted to the Claremont Colleges current faculty, students, and staff.