A typical day at the San Ysidro Port of Entry | Photo: Elizabeth Hensley Chaney
Californias border with Baja California is a complex region with unique environmental issues. Our Borderlands series takes a deeper look at this region unified by shared landscapes and friendship, and divided by international politics.
Just north of the ramp, one of the last remnants of the old border-crossing footbridge, pedestrians cluster in the shade of a plastic tarp as they wait to enter the San Ysidro Port of Entry Pedestrian Facility. Meters west of the sidewalk is a temporary wall built of OSB and two-by-fours, painted white and coated in grey dust. The wall was installed in 2012 to separate southbound pedestrians from vehicular traffic. On the other side of the buckling temporary wall, 25 lanes of traffic, with vehicles ranging from chocolate autos to diesel buses to street bikes and hybrids, idle as passengers wait to reach the customs inspection booths.
The San Ysidro Port of Entry facility processes around 50,000 private vehicles daily. From 7:00 a.m. to 5:00 p.m. weekdays, wait times range from one to two and a half hours. As the waiting vehicles idle, they produce a copious variety of toxicants. They include nitrogen oxides, which are associated with respiratory ailments benzene, which increases the risk of cancer and other illnesses carbon monoxide, which reduces the oxygen-carrying capacity of blood and particulate matter (a.k.a. soot), known to cause respiratory and cardiovascular disease. Pedestrians waiting on the other side of the OSB wall breathe it all in, for up to four hours at a time.
Three miles north of the San Ysidro Port of Entry, Guillermo Cornejo carries lemons from his backyard tree to the kitchen sink. Washing the lemons has been an everyday ritual in Guillermo's household. The soot that coats them probably comes from diesel vehicles travelling along State Route 905, just a quarter of a mile north of the home. SR 905 travels between Interstate 5 and the Otay Mesa Port of Entry, a checkpoint for commercial traffic going between Baja and Alta California.
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San Ysidro, the community closest to Guillermo's home, is a colonia of San Diego. Though it's 12 miles south of downtown San Diego, with the cities of Chula Vista and National City in between, San Ysidro was annexed by San Diego in 1957. It is a community with two distinct faces. On the one hand, it is seen as a great site for retailers because of its location near the international boundary. At the same time, residents face a whole host of challenges due to the community's location next to the most heavily transited land Port of Entry in the world. These challenges are seldom addressed by decision makers, whether in San Diego, Sacramento, or Washington.
Guillermo and his wife bought their home in 1981, motivated in large part by the property's ample backyard. When Guillermo, a retired engineer, purchased the home, he was aware of the potential inconvenience of living near a highway. But traffic along Interstate 5, which is 50 feet east of his backyard, was then very light. He recalls that in 1982, soon after he moved, an automobile would pass [only] around every 10 or so minutes. That was nothing like today's volumes along the Interstate that extends north from the international boundary, which he describes as a train of cars.
Lemons growing at the Cornejo residence in San Ysidro | Photo: Elizabeth Hensley Chaney
I met Guillermo at a community workshop in late August. The meeting was held to present to community members a set of air quality monitors which will be installed throughout San Ysidro, as part of a two-year study funded by the California Office of Environmental Health Hazard Assessment (OEHHA) and the California Environmental Protection Agency (CalEPA). The San Ysidro Air Quality and Border Traffic Study is conducted by researchers based at the University of Washington School of Public Health and the San Diego State University Graduate School of Public Health in consultation with members of the community of San Ysidro brought together by Casa Familiar, a local community development organization. The study's aim, in the words of the researchers, is to identify the sources and levels of air pollution with the goal of developing mitigation strategies that might reduce exposure in the community. Guillermo serves on the Community Steering Committee, formed to support the study in February 2016.
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He learned about the study and the Committee from a friend who helps coordinate exercise classes he takes at the nearby San Ysidro Civic Center. His interest was piqued at the thought that participating in the study could help him to better understand his worsening allergies. Living near the freeway that leads to and from the most heavily used land Port of Entry, he's frequently exposed to nitrogen oxides. He worries that this exposure has affected his immune system, causing daily allergy attacks.
Guillermo started taking the exercise classes about three years ago, after he retired. The Civic Center, where the classes are held, is a city-owned building leased to Casa Familiar, a few minutes' walk from both I-805 and I-5. The building is also one of 13 sites where the Community Steering Committee has proposed placing one of the air quality monitors employed by the study. Curiously, the City of San Diego won't authorize placing a monitor on the property. At times during his exercise classes, Guillermo senses a faint aroma of gasoline, which he attributes to the location of the building between two busy freeways leading to the Port of Entry. He's concerned about the effect of exposu
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A typical day at the San Ysidro Port of Entry | Photo: Elizabeth Hensley Chaney 
