Description
Traffic-related pollutants associated with the U.S.-Mexico International Port of Entry (POE) present environmental justice concerns through presenting adverse health risks to the surrounding community of San Ysidro, CA. The community is comprised of a mainly low- income and minority population, and has a young median age, and therefore is a vulnerable population. This paper assessed the black carbon (BC) levels in 4 sites in San Ysidro over 3 periods of time ranging for a week to a month in 2017. Measurements were collected at 4 locations in the community (Nicoloff Elementary School [NES], The Front “Arte Cultura” [FRNT], Willow Elementary School [WES], and San Ysidro Middle School [SYMS]) and 1 coastal reference site (Tijuana Estuary Visitor Center [TJRE]). All locations besides TJRE are located near highly trafficked roads, specifically, the Interstate 5, the Interstate-805, California State Route-905, and the U.S.-Mexico International Border. Portable air quality instruments microAeth® AE51 and the Portable Aethalometer® AE42 collected BC data at 1 or 5-minute intervals. Field data from the instruments were collocated and averaged into hourly values for an easier comparison. Urban San Ysidro sites had significantly higher concentrations (p<0.01-0.001) of overall BC hourly means for all snapshots compared to TJRE BC concentrations (1.0 [S1], 0.2 [S2], and 1.9 μg/m3 [S3]). Snapshot 1’s BC concentrations were: 2.1 (WES), 1.8 (FRNT), and 1.7 μg/m3 (NES). Snapshot 2’s concentrations were: 0.3 (WES), 0.2 (FRNT), 0.2 (NES), and 0.4 μg/m3 (SYMS). Snapshot 3’s concentrations were: 1.9 (WES), 3.9 (FRNT), 3.2 (NES), and 3.3 μg/m3 (SYMS). High BC concentrations were observed during winter and spring. Night-time concentrations were also found to be significantly higher (p<0.01-0.001) compared to day-time. Pollution roses of TJRE’s BC concentrations indicated that winds originating from the west were associated with lower BC levels (0-1 μg/m3) while winds from north-east with higher levels (20-30 μg/m3). Results demonstrated that spatial and temporal factors have significant effects on BC concentrations. Sources of BC in San Ysidro should be further investigated so appropriate mitigation and adaptation strategies can be instigated. High levels of exposure to BC in the border community of San Ysidro should be considered an environmental justice issue.
