Hemmed in by three freeways and backed up against the border and port of entry, San Ysidro residents are exposed to an unceasing stream of air pollution from millions of vehicles passing through the community that is the busiest gateway to Mexico.

Over the years residents have expressed concern about the air pollution, pointing to an unusually high number of asthma cases.

Now, as the U.S. government works to expand the border crossing, San Ysidro residents are bracing for an even busier border – and all the health effects that might come with it.

David Flores, community development officer at the advocacy group Casa Familiar, said there has never been an effort to collect data to determine if the asthma and car exhaust are linked.


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The border expansion has heightened health concerns as calls for an air pollution study of the community have gone unheeded, Flores said. So, San Ysidro residents, led by Casa Familiar, have obtained $229,935 in funding from CalEPA to do their own air-pollution study.

The two-year program will include 12 air pollution monitors being built specifically for the project by University of Washington scientists. The equipment will be placed in different areas of the community to collect air-pollution data.

Sam Delson, spokesman for the state Office of Environmental Health Hazard Assessment, said the study is unique because most air-pollution research is done by industry and government. Delson’s agency, which is part of CalEPA, was designed to assist communities just like San Ysidro. The community, which is 93 percent Hispanic, has the highest population density of the five communities identified as a South Bay Sub-Regional Area, the lowest median household income, at $35,993, and a poverty rate of 25 percent.

Flores said he and others decided to act after getting a disappointing response about their health concerns from the General Services Administration. The federal agency is in charge of the $735 million expansion of the San Ysidro Port of Entry to be completed by 2019.

Customs and Border Protection figures 14.3 million vehicles, 6.6 million pedestrians and 32.8 million total travelers passed through the San Ysidro Port of Entry in fiscal year 2015. The average wait time for cars was 32 minutes, compared with 61 minutes in fiscal year 2010, according to CPB.

The expansion is intended to speed up northbound border crossings for vehicles and pedestrians, and construction on the Mexican side is supposed to facilitate and speed up traffic entering Mexico. The GSA’s Environmental Impact Statement said there would be “no impact related to environmental health and safety risks to children” caused by the expansion.

That conclusion is based on an analysis that found air pollution would rise slightly because of an “increase in daily traffic trips” on the freeways, but pollution from vehicles crossing to and from Mexico would decrease. Queue times at the border crossing will be faster and vehicle idling times shorter when construction is completed, resulting in an overall pollution reduction, the agency said in an emailed statement.

Customs and Border Protection, whose officers man the port, said wait times would likely drop when construction is completed but also predicted an increase in the number of vehicles.

CBP officials said traffic increased by more than 25 percent when the number of lanes grew from 17 to 25 during Phase 1 of the project, which is scheduled for completion this summer. Phases 2 and 3 are set to be completed by fall 2019.

Flores questioned the GSA’s findings that traffic will move faster through the port.

“We believe all this expansion will only result in more vehicles idling at the port. Stopped vehicles produce pollution that on most days blows into San Ysidro. Pollution aggravates respiratory problems, and asthma rates for San Ysidro school kids are already very high,” he said.

Longtime San Ysidro resident Rudy Lopez, 37, whose family has owned a grocery store in the community for decades, has a 4-year-old son who suffers from respiratory ailments, including a chronic cough.

Lopez, who said he is also involved in a business in Tijuana, is a frequent border-crosser and scoffs at GSA claims of shorter wait times when the expansion is completed.

“You’re still going to have cars stopped and engines idling,” he said.

A 2015 study by SANDAG showed that San Ysidro and the South Bay have an asthma rate nearly 18 percent higher than San Diego. The area also has rate of Chronic Obstructive Pulmonary Disease 20 percent greater than San Diego.

A 2003 state law prohibits the building of schools within 500 feet of a freeway or major roadway unless air pollution can be mitigated or space limitations leave no other option. The SANDAG study found that 41 percent of households in San Ysidro lie within 500 feet of a “transportation related air pollution source.” The figure is 12 percent for San Diego.

The study cited research that shows that by age 18, children exposed to higher levels of pollution caused by fossil fuels are five times more likely to have underdeveloped lungs.

The SANDAG study also noted that California has labeled diesel engine exhaust a carcinogen, and the state said diesel engine exhaust accounts for 70 percent of the cancer risk from air pollution. The figure is an ominous one for San Ysidro residents. Thousands of trucks that bring agricultural products and manufactured goods from Mexico use the 905 freeway, which borders San Ysidro to the north.

Other studies have shown a direct link between air pollution and childhood asthma. A 2012 USC study concluded that at least eight percent of childhood asthma cases in Los Angeles County “can be attributed to traffic related pollution at homes within 250 feet of a busy roadway.”

Flores said that studies like the ones conducted by SANDAG and USC have raised the level of concern in San Ysidro over the port expansion. He said temporary monitors placed at the port, 200 feet north of the port and at a “clean site” in Imperial Beach a few years ago showed that pollution was 10 times higher at the port than in Imperial Beach.

The U.S. Environmental Protection Agency and the San Diego County Air Pollution Control District placed an air pollution monitor at the San Ysidro Port in February 2015 for a two-year study. The monitor measures fine particulate matter in real time, but it has been down since last month because of port construction, said district spokesman Bill Brick, chief of monitoring and technical services.

Brick said that so far officials have not seen readings that “have jumped off the page.” The monitor is one of five active monitors maintained by the district throughout the county. He said that when the port monitor registers high pollution, monitors at the other sites usually have high readings too. Brick said this is usually due to pollution blowing in from Los Angeles, or atmospheric conditions.

On days when the port monitor is showing higher readings than other areas in the county, Brick said it is because of pollution moving into the South Bay from Tijuana. The monitor is next to a roadway, noted Brick, which he said is “an extreme case.”

But University of Washington researchers, who are partnering on the new San Ysidro study, said the lone monitor used by county and federal officials at the port of entry is not adequate to measure the effect of air pollution in the community.

The goal of the community study is to measure how air pollution changes over time and space, and identify areas in San Ysidro where pollution is greater. Using information gathered from the 12 monitors, the scientists will assist residents in developing strategies to reduce exposure.

University of Washington scientist Dr. Edmund Seto attended a March 29 community meeting on the study, and said the researchers will partner with the community as it moves forward.

“It’s their study. We’re here to offer technical and scientific advice but they’re going to plan and make decisions about how to proceed,” he said.

    This article relates to: Border, Border Crossing, Environmental Regulation, Must Reads, Science/Environment

    Written by H.G. Reza

    H.G. Reza is a freelance contributor to Voice of San Diego. He worked at the Los Angeles Times for 25 years, covering law enforcement and terrorism.

    4 comments
    Carrie
    Carrie subscribermember

    Kudos to San Ysidro for taking this step. The border entry pollution is only the tip of the iceberg regarding Tijuana as a source of pollution. The brown cloud from Tijuana is obvious and often massive. Is Mexico planning to do anything about it?

    Bill Bradshaw
    Bill Bradshaw subscribermember

    And where, pray tell, was the city council member supposed to represent San Ysidro in this story?  He wasn’t mentioned; is that an oversight?  Seems like a natural for someone who aspired to be mayor recently, a largely Latino community with what appears to be a legitimate gripe about air pollution.


    Here’s the deal:  David Alvarez is owned by organized labor.  Don’t take my word for it; check his campaign contributions at the City Clerk’s web site for confirmation.  The thing is, the unions don’t have much going in San Ysidro, so Alvarez has more important things to do, like lobbying for minimum wage increases, than being concerned with the health of his constituents next to the border.


    The biggest producer of air pollution is the border crossing from Mexico back into the U.S.When both countries agreed to enlarge and modernize their entries, the Mexicans had their’s operating in less than a year.Cars do not pile up at the gates.On the U.S. aside, work is still under way and the waits are as long as ever, often taking an hour or more in line with engines running.THIS is what should be studied for improvement. 

    Derek Hofmann
    Derek Hofmann subscribermember

    Restrict normal vehicles to 1 lane (hybrids, electric cars, and bicycles can use the other lanes), and charge a fee proportional to the number of cars currently waiting in line. Emissions problem solved, and as a bonus it will cut down on time waiting at the border and provide a revenue source to pay hospital bills for respiratory ailments.

    Mike German
    Mike German

    The prevailing winds in this area blow from West to East, off the ocean and into the interior, except when Santa Anas obtain.  I wonder how the air quality is East of SY, near the truck crossing at Siempre Verde and Koll Dr.?  I also wonder how strictly the laws against idling Diesel engines are being enforced, as well as smog checks upon vehicles operating in and through the area, especially those from outside the USA.   We are entirely within our rights in requiring all vehicles, whatever their origin, ownership, or destination, to pass smog tests before being driven on CA's roads and highways.  Once, as I suspect, a lot of the problem is determined to be caused by "unsmogged" cars and trucks registered outside of CA and the USA, we need to ensure that they are properly smogged before being allowed to use our roads again.  And, we should also be monitoring Mexico's enforcement of its own air quality laws.  As close as we are to the border crossings, it can be done economically and unobtrusively by simple observation of how trucks process on the Mexican side of the border.  These factors need to be considered in analyzing and solving this problem as well