Date of Award

8-2023

Document Type

Project

Degree Name

Master of Science in Environmental Sciences

Department

Chemistry and Biochemistry

First Reader/Committee Chair

Andreas Beyersdorf

Abstract

San Bernardino, California’s poor air quality is a health risk to its population with some of the highest concentrations of ozone and aerosol in the United States. Aerosols are solid or liquid particles suspended in the air. Smaller aerosol particles are the most harmful as they are more likely to penetrate further into the respiratory system. These aerosols can cause respiratory issues and contain toxic compounds. One measure of aerosol toxicity is to study the mutagenicity of the aerosol. To study the mutagenicity of aerosol samples collected in San Bernardino in 2022, fluctuation tests (based on the Ames test for mutagenicity) were used with a modified bacterial strain of Salmonella typhimurium that cannot grow without the addition of histidine. The presence of mutagens in sample extracts cause the bacteria to mutate and grow. This bacteria growth can then be detected based on a change in color of a pH indicator. In addition to the bacterial fluctuation test, heavy metal concentrations in the aerosols were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES). No correlation between mutagenicity and heavy metal concentration was found. There was also not a clear seasonality to the particulate matter concentration and total metal concentration. However, there was a correlation between particulate matter concentration and rates of mutagenicity. From these analyses it was found that a 60% increase in aerosol concentration corresponded to a 92% increase in the rate of mutagenicity.

Due to these measurements, it is believed that metals are not the cause of the mutagenicity. Future studies should include the measure of possible mutagens such as polyaromatic hydrocarbons (PAHs). In addition, analysis of an entire year of samples should be performed so that trends of mutagenicity compared to aerosol concentration can be determined.

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