UC Berkeley

The many successful efforts to reduce air pollution in California since the 1990s through regulations from the California Air Resources Board (CARB) initially targeted on-road vehicles; however, air pollution is not equally distributed, and some populations still experience greater exposure burdens than others. Two populations disproportionately exposed to air pollution were examined in Northern California: communities of Stockton and Fresno, who experience historically poor air quality because of trapped air pollution in the Joaquin Valley; and farmworkers who use off-road diesel-powered agricultural equipment, and whose exposure to carcinogenic diesel exhaust has been poorly characterized. We conducted exposure assessments for three different air pollutants: polycyclic aromatic hydrocarbons (PAHs), nitrogen dioxide (NO2), and diesel particulate matter, measured as black carbon (BC). Participants in Stockton and Fresno were recruited within the San Joaquin Valley Pollution and Health Environmental Research (SPHERE) Study to characterize residential exposures to air pollutants. Additionally, the Agricultural Off-Road Diesel Equipment (ACRE) Pilot Study was funded and conducted as part of this doctoral research. Within the ACRE Pilot Study, we assessed occupational exposure to diesel exhaust, perceptions of work and exposure, and attitudes about report-back of personal exposure results among farmworkers. Our findings demonstrated infiltration of outdoor PAH concentrations into home environments in Stockton and Fresno, which may have been facilitated by opening windows and home type, as well as a seasonal effect with higher outdoor concentrations in the spring compared to summer and fall months. We identified sources of indoor exposure to PAHs, including burning candles, using gas-powered heaters, and smoking or vaping in the home. Older tractors resulted in higher concentrations of measured air pollutants than newer tractors. Results also show that farmworkers may be more highly exposed to diesel exhaust than the general public and farmers and that more training for farmworkers about diesel exhaust and exposure reduction strategies is warranted. Most farmworkers in the study wanted their personal exposure results and reported that a short explanatory video aided in their understanding of report-back documents. This dissertation elucidates sources of exposure and opportunities for exposure reduction in marginalized populations exposed to air pollutants at home and at work.