The Other Crisis at the U.S.-Mexico Border: Rising Air Pollution

4 minute read

For years now, there’s been a constant stream of stories about a “crisis” at the border between the U.S. and Mexico as migrants travel north from Central America. Just this week, a quick Google news search shows recent headlines about a “tipping point” and a “humanitarian crisis” at the border. But on a recent trip to San Diego, I learned about another crisis at the southern border that’s threatening lives in local communities and, less directly, around the world: hours-long waits to enter the U.S.

The long wait to cross the border may sound like a minor inconvenience at first glance, but the time it can take vehicles to enter the country means thousands of idling cars and trucks. Having these vehicles sit on the road for hours on end isn’t just a giant waste of time, it also generates considerable air pollution. This in turn harms the health of people who live in border communities and contributes to climate change. “It’s billions and billions of dollars that we’re losing in economic productivity due to the wait times in addition to the emissions that are being generated,” Mario Orso, a project coordinator at Caltrans, the state transit authority, told me as we drove to the border in early February.

Both the solution—reducing wait times at the border—and the knock-on effects—improving the health of tens of thousands of local residents—are classic examples of how climate policy has seeped into everything.

Problems and solutions

Pollution at the border is a classic story of unintended consequences. Following the 9/11 terrorist attacks, the federal government tightened inspections at the border and wait times soared from under 30 minutes to several hours. Today, average wait times at the San Diego-Tijuana border crossing stretch up to two hours.

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In 2009, Casa Familiar, a local community development non-profit began to study how local residents who crossed the border on foot were exposed to air pollution. A cohort of border-crossers were equipped with personal air pollution monitors and researchers set up air quality monitoring devices at the port of entry. The results were upsetting, if not entirely surprising. Levels of particulate matter, a pollutant made of tiny particles of dust, dirt, and smoke, among other things, were ten times higher than in the community less than 10 miles north up the highway elsewhere in San Diego County. Later research conducted by Casa Familiar in partnership with the University of Washington found a direct correlation between the long lines and air pollution levels. “The higher the wait times, the higher the pollution,” says Alejandro Amador, environmental programs manager at Casa Familiar.

All of this has had a devastating effect in San Ysidro, the district of San Diego directly adjacent to the border that is 85% Hispanic and where more than half of residents lack a high school education. Asthma rates and the incidence of cardiovascular ailments are among the highest in the state.

Of course, it’s much more difficult to see the global damage, but keeping tens of thousands of vehicles idling also has implications for the climate. Delays at the border result in 457 metric tons of carbon dioxide emissions being released every day, equivalent to the annual emissions of 100 passenger vehicles, according to data from San Diego’s regional transportation planning agency.

Climate solutions are often difficult to identify and even more difficult to implement. But here the fix—or really the fixes—are easy to pinpoint: the wait time at the border needs to fall. In order to do that, local officials are exploring a range of levers, from expanded bike and pedestrian access to better lane management. During my time in the area, I visited one such lever: an entirely new port of entry under construction that would alleviate congestion. Orso, the project coordinator, zipped me around the 100-acre construction site in his Caltrans truck, driving up close to the border fence. For years, I’ve been writing about how climate change seeps into every aspect of our lives. And while the connection between migration and climate change has been covered in depth—including in this newsletter—I was still surprised to find a climate story in what seemed like the most unexpected place.

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Write to Justin Worland / San Diego at