As any urban dweller knows, all traffic is local. But what’s inside its dark spew, and how it affects people nearby, is a mystery. Two new air monitors coming to San Diego will help answer the question: Can living near a major road be dangerous to your health?
The monitors will keep track of nitrogen dioxide (NO₂), for which the Environmental Protection Agency recently tightened outdoor air-quality standards. Big cities like San Diego are part of “near roadway” monitoring, which may expand to include other emissions.
“Ahead of the law, we have to have ideas,” says Mahmood Hossain, chief of the San Diego Air Pollution Control District. The district must submit its plan by mid-2012, and Hossain has several sites in mind. The district now monitors NO₂ and other pollutants — but not by roads, where concentrations peak. Most health effects are seen within several hundred feet of what the EPA calls a “major” or “busy” road.
In San Diego, such roads are hard to avoid.
“Coronado is otherwise Heaven on Earth,” John Sexton says. He moved from a house between two Navy commuter routes to one that “also gets quite a lot of traffic.” He lived 110 feet from the road; according to Caltrans, each day on State Route 282, the highway near his previous home, 33,800 vehicles go by — once on the way to work along 3rd Street, then home on 4th Street in the afternoon.
For about 30 days each year, three ships are in, and “that number more than doubles” the traffic numbers, Sexton says. Most drive solo. “One only needs to stand next to 3rd or 4th Streets to see the very limited number of HOVs.” Ten years ago, Sexton and others began rallying the town on traffic mitigation and citing health studies.
Coronado, population 24,697, shares a traffic corridor with the largest combined military airport and aircraft-carrier berthing facility on the West Coast, according to a study commissioned by the city. The study called 3rd and 4th Streets “San Diego County’s most heavily traveled residential streets.”
“If the Navy had an entrance that only permitted HOV traffic,” Sexton says, it would be “a great incentive to carpool.”
Others have called for stop signs and lights, but these can actually increase emissions. When cars stop and go, the acceleration “changes the patterns of emissions exhaust and pollution-control devices, and levels can be much higher,” says Ed Avol, a professor at USC Keck School of Medicine. Avol, a graduate of UCSD, is part of the National Children’s Health Study, researching the effects of dirty air.
Sexton’s new “quieter” street once rattled with Navy trucks. A former resident, Ricardo Johnson, moved in 2007 to escape the traffic. Finally, the rigs were rerouted…onto congested 3rd Street.
Near the bridge, 70,800 vehicles go by daily from the toll plaza to C Avenue, according to Caltrans. Many then turn off 3rd Street onto Orange Avenue, reducing traffic headed to the base to 33,800. But by the bridge, the road roars; especially when three ships are in; over 140,000 vehicles may pass.
Hundreds of studies have found correlations between traffic emissions and diseases such as asthma, heart and lung ailments, cancer, and more. Recently, researchers at USC found a link between short-term exposure to traffic pollution and brain damage. The list “runs the gamut” of health outcomes, Avol says. He considers a daily volume of about 100,000 vehicles “very high” for a residential street. Health effects in children have been found at less than half that amount.
High-traffic roads are often defined as having more than 50,000 daily vehicles. Other variables count, too: how long the resident lives there; when they’re home; wind direction; distance from lanes; and more. Many pollutants “fall off almost exponentially with distance,” Avol adds. For really busy roads, a few thousand meters “is probably okay.”
“There is an old adage in pollution control about putting some distance between yourself and the source of exposure,” Avol says. Unfortunately, since living near where you work reduces driving emissions, “that [advice] runs exactly counter to the trend toward compact urban development.”
In its 2011 State of the Air Report, the American Lung Association gave San Diego an “F” on ozone and particulates, most of it from traffic.
While not a greenhouse gas, NO₂ leads to the formation of ozone.
Hossain disputes the scarlet letter. “We never agreed with the Lung Association ranking, and we tend to ignore that,” he says. “San Diego has excellent air quality throughout the year.” There may be seasonal increases, with “slightly elevated” ozone levels in summer and particulates in winter. Otherwise, “only one site in San Diego records a bit higher ozone level.”
Debra Kelley of the San Diego chapter of the American Lung Association says the group, which translates EPA data into grades, “uses a very strict standard.” With about half the population “sensitive to bad air,” even a few days of high pollution affects many people. But there are “points of reference,” Kelley admits. “Our air is way cleaner than Los Angeles.”
And Los Angeles air, while unhealthy, is “really good” compared to, say, Mexico City, Avol says.
The air in both cities has improved. Cleaner engines and reformulated gasoline have helped, says Hossain, who has witnessed changes over 29 years with the district. But for those most affected by them, busy streets still mar the picture.
“Regional agencies are supposed to place monitoring stations away from any local source, to get a better sense of what the larger region is exposed to,” Avol says. The new NO₂ rules will change that. In the next few years, near-road monitoring will show “how much we have been missing by only thinking about regional levels.”
For now, Hossain faces a different traffic problem: the safety of his staff. The air monitors must be visited weekly. They’ll sit within 150 feet of a wall of traffic.
“It’s going to be very tricky trying to find a place right next to the freeway.” ■