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Description
San Ysidro, a border city located just north of Tijuana on the US side of the US-MX border, hosts a land-based Port of Entry (POE) which is the busiest international land border crossing in the world. The community of San Ysidro had concerns about pollution from idling vehicles at the POE as well as pollution from vehicles and burning activities in Mexico. San Ysidro is, for the purposes of SB535, both an environmental justice community and a disadvantaged community due to disparities in air pollution and traffic. For over a year, the US EPA funded a monitor at the POE that measured fine particulate matter (PM2.5), on an hourly basis. This study examined hourly PM2.5 over a 17-month period during 2015 and 2016. Data from this monitor (code SAY and SAY2) was used to look for pollution patterns in relation to wind patterns. The R statistical program and RStudio were used with the openair package to generate wind and pollution roses to analyze seasonal and temporal patterns. HYSPLIT and R were used to generate 24-hour back trajectories for ‘test’ days where the daily average PM2.5 concentrations exceeded the 95th percentile and were higher than a downtown San Diego monitor at Perkins Elementary School (PES) (25 days). Pattern analysis and octant analysis were conducted on 24-hour back trajectories generated for both test and control days. The mean PM2.5 concentration for the study period was 13.4 μg/m3 with the highest levels recorded in February 2015 (20.0 μg/m3) and the lowest in July 2015 (8.3 μg/m3). Although this study determined that winds from Mexico were not the sole influencer on elevated PM2.5 in San Ysidro, patterns indicate that winds from Mexico may elevate pollution in the near border community at night and especially during winter months. In conclusion, this project suggests that elevated PM2.5 is associated with winds southeast and east of the San Ysidro US-MX border, indicating pollution arising in Mexico as a major contributor. Strategies to reduce pollution in the impacted border community should be sought
