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.

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.

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.

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