The monitor measures PM_2.5 (fine particulate matter up to 2.5 microns in diameter) in the form of soot from engine emissions, which can result in negative health effects when inhaled.

EPA provided $110,000 to the SDAPCD for the purchase, installation, and operation of the San Ysidro PM 2.5 monitor.

A 2014 study by researchers from the University of Washington and San Diego State University, published in the journal Atmospheric Environment, found that subject pedestrians who crossed the border at San Ysidro in pedestrian lanes had a 6-fold increase in exposure to 1-nitropyrene (1-NP, a marker for diesel exhaust), a 3-fold increase in exposure to CO, and a 2-fold increase in exposure to gravimetric PM2.5, vs. non-border commuters.

Resources

• V.E. Galaviz, M.G. Yost, C.D. Simpson, J.E. Camp, M.H. Paulsen, J.P. Elder, L. Hoffman, D. Flores, P.J.E. Quintana (2014) “Traffic pollutant exposures experienced by pedestrians waiting to enter the U.S. at a major U.S.-Mexico border crossing,” Atmospheric Environment doi: 10.1016/j.atmosenv.2013.12.042

• Penelope J.E. Quintana, Jill J. Dumbauld, Lynelle Garnica, M. Zohir Chowdhury, José Velascosoltero, Arturo Mota-Raigoza, David Flores, Edgar Rodríguez, Nicolas Panagon, Jamison Gamble, Travis Irby, Cuong Tran, John Elder, Vanessa E. Galaviz, Lisa Hoffman, Miguel Zavala, Luisa T. Molina (2014) “Traffic-related air pollution in the community of San Ysidro, CA, in relation to northbound vehicle wait times at the US–Mexico border Port of Entry,” Atmospheric Environment doi: 10.1016/j.atmosenv.2014.01.009