Inhalation Doses of Back Carbon at the US-Mexico Port of Entry San Ysidro/El Chaparral

Rita Zurita, Penelope Quintana, Yanis Toledano-Magaña, Fernando Wakida, LUPITA D. MONTOYA, Javier Castillo, Universidad Autónoma de Baja California, México

     Abstract Number: 598
     Working Group: Aerosol Exposure

Abstract
The San Ysidro/El Chaparral Port of Entry (SYPOE) is the most active port in the Western hemisphere. Previous studies have associated high concentrations of ultrafine particles, carbon monoxide (CO), and black carbon (BC) with waiting times during border crossing. BC has been air quality indicator for evaluating the health risks of air quality dominated by primary combustion particles The objective of this study was determined the inhalation dose of BC of pedestrian border crossers and workers at the SYPOE. BC sampling took place between November 2017 and January 2019. The inhalation dose of BC was calculated according to published methods. The highest average daily dose for pedestrians was estimated for autumn 2018 (5.9 μg) corresponding to a 60min waiting time. For the workers, an average daily dose was also estimated based on their individual working schedule, and the highest was in winter 2017 (19 μg for an average of a 10-hr work shift). Diurnal distribution of inhalation dose of BC for workers at the SYPOE showed the highest doses between 7:00 to 9:00 am and 7:00 to 9:00 pm. Decreasing waiting times for pedestrians on days with high air pollution would reduce their inhalation doses. More importantly, limiting doses of workers may require modifying their schedule to decrease their exposure. These recommendations would partially address environmental justice in the border area.