Tuesday, Feb. 20, 2007 | Each year, about 730,000 diesel-exhaust spewing trucks cross north into San Diego at the Otay Mesa border crossing. Once they’ve cleared customs, they throttle out Otay Mesa Road, a nondescript stretch of asphalt that takes them past open fields — undeveloped tracts of land whose fate the city is currently deciding.

If a group of developers gets its way, those vacant lots would become San Diego’s newest neighborhoods. The developers hope to build thousands of homes directly adjacent to a proposed interstate extension that would carry some of the region’s dirtiest truck traffic.

Seven developers — the Corky McMillin Cos., D.R. Horton, Pardee Homes, Centex Homes, Sunroad Enterprises, Integral Partners and Murphy Development — are pushing to rezone eastern portions of Otay Mesa to make way for up to 9,500 new homes on what is currently designated for industrial and commercial uses.

The homebuilders are funding the studies that accompany the border area’s future development plan. In exchange, their preferred plan has been guaranteed an audience with the City Council, which will consider several blueprints for Otay Mesa in November. The developers’ preferred plan calls for new housing along the interstate extension; other alternatives do not.

If those homes are built, research shows that their residents will be at risk for a host of respiratory illnesses and other ailments. A robust body of scientific evidence shows that living near freeways threatens residents’ health, increasing short-term mortality while reducing children’s lung development. A landmark study released last month shows those effects extend further beyond freeways than once thought. Not heeding that science, several health experts said, would disregard the public’s well-being.

“It would be irresponsible, given what we know now, to put a major artery through a planned residential community,” said Dr. Ira Tager, a professor of epidemiology at the University of California, Berkeley, School of Public Health. “A strong case could be made that this is not the way you should build something like this.”

Historically, when planners have considered building homes near interstates, their primary concern has been noise generated by cars and trucks swishing past. This explains noise-reducing buffers such as sound walls and landscaping. But a growing body of scientific research shows that residents’ lungs — not their ears — should govern decision-making.

A study published Jan. 26 in the British medical journal Lancet says that pollution generated on highways can stunt children’s lung development from as far away as 1,600 feet, farther than once believed. The University of Southern California researchers behind the study call it “the freeway effect.”

Living within 1,600 feet of a freeway — one-third of a mile — was found to adversely affect children’s lung development, increasing their risks of serious respiratory illnesses and cardiovascular disease later in life. Researchers monitored 3,600 Southern California children from age 10 until they turned 18 years old, using tests that measure how fast and how much the lungs exhale. By the end of the 13-year study, researchers found children living within 1,600 feet of freeways exhaled 3 percent less air with 7 percent less force than those living a mile away.

Some discrepancy still exists about where the highest exposures occur, said lead author James Gauderman, a professor of preventative medicine at USC’s Keck School of Medicine. His study showed trends within 3,200 feet of freeways, though the most statistically significant occurred within 1,600 feet.

“This and other studies point to the need to consider health when we plan schools and homes,” Gauderman said.

Developers’ plans for Otay Mesa appear to ignore that recommendation. Two proposed neighborhoods straddle a proposed extension of Interstate 905. Another entire development would fall almost completely within about 1,500 feet of the road — close enough to bear the full brunt of the “freeway effect.”

City planning officials say they’re aware of the science as well as California Air Resources Board guidelines that recommend against building homes within 500 feet of freeways. They say they will incorporate those studies and guidelines in their plans, potentially requiring businesses — not homes — to be built along the freeway.

“We’re looking at those as we develop our urban design guidelines for the urban plan update,” said Mary Wright, a city planning program manager.

Some question whether city officials are sincere and say they would rather see formal policies, not informal promises.

“How is that actually going to get implemented? That hasn’t come out in the process,” said Laura Benson, a policy advocate at the National City-based Environmental Health Coalition. “When you have a totally new community — vacant land — why would you start getting into that mess if you don’t have to?”

The consortium of homebuilders behind the project, known as the Otay Mesa Planning Coalition, said they are prepared to shape their developments to standards that will be outlined in a environmental impact report, which the city and its consultants will prepare during the next year.

David Nielsen, a lobbyist for the coalition, said the California Air Resources Board guidelines, which recommend against building homes 500 feet from freeways, are “much quoted and misquoted” by critics who may try to attack the issue. But he said he doesn’t anticipate projects will have to be scrapped because of truck traffic impacts.

The state has begun addressing the “freeway effect” through regulation. State law restricts the construction of new schools within 500 feet of freeways. But that rule does not extend to homes or daycare providers, and USC’s Gauderman said the rule has no teeth. While it prohibits schools from being built near freeways, it doesn’t prevent freeways from being built near schools.

With California taking some steps toward ensuring schoolchildren’s health, “it seems surprising that that care and planning isn’t translating over into residential settings where people are more likely to be,” said John Spengler, a Harvard University professor of environmental health and human habitation. “This is the time to make a difference in how we plan our infrastructure.”

Emissions from diesel combustion in trucks and buses pose the largest cancer risk in the air around us. The particles are extraordinarily small. The lungs inhale them deeply. What’s worse: Carcinogenic chemicals such as benzene often attach themselves to the particles, lodging themselves deep in the lungs, where they can wreak havoc on lung function.

The homes in the Otay Mesa plan would be built along a uniquely problematic truck traffic corridor. The Otay Mesa border crossing is the region’s major thoroughfare for cargo trucks driving north from Mexico. Those trucks — manufactured and driven in the United States and then handed down — typically produce dirtier emissions than trucks here, because they’re older and have degraded emission-control systems, said Rob Reider, a spokesman for the San Diego County Air Pollution Control District, the local air regulator.

The state is working to address long-term diesel pollution. The California Air Resources Board is developing regulations that would mandate emission controls on those border-crossing trucks. Since October, the state has required all diesel fuel sold to be ultra-low-sulfur, a cleaner burning variety.

USC’s Gauderman said those regulations are a step in the right direction, but noted that diesel trucks are not the sole source of roadway pollution and the “freeway effect.” Further study is needed, he said, to pinpoint the most problematic pollutants.

Staff writer Evan McLaughlin contributed to this story.

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