Tuesday, Jan. 2, 2007 | Stare down Escondido Boulevard, and the air looks clear. No smokestacks spewing white clouds, no diesel trucks blowing black plumes.
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There’s the Lung Doctor, a local store, but it sells smokes. Rows of taquerias make the street smell like tamales, not toxics.
But this Escondido ZIP code — 92025 — was San Diego County’s largest source of business-produced toxic air pollution in 2004. Blame its gas stations, dry cleaners and body shops. They emitted a total of 40,430 pounds of chemicals in 2004, according to a voiceofsandiego.org analysis of the most recent year’s data maintained by the San Diego Air Pollution Control District.
Poway’s 92064 finished a close second with 40,217 pounds of toxic pollution produced. El Cajon’s 92020 was third (37,875 pounds), San Diego’s 92111, the community of Linda Vista, was fourth (35,844), and Vista’s 92083 was fifth (34,356).
Toxic air pollution is all around us. Regulators describe it as a “toxic urban soup.” It comes from the gas we put in our cars, the paints that body shops use, even from the flickering flames inside crematoriums. While its public health risks vary depending on exposure and toxicity, an examination of the toxic air data opens a window into how we pollute our neighborhoods, the chemicals we’re commonly exposed to and the reasons they’re used.
Air pollution is categorized two ways. By toxics, which pose problems locally, and by the larger, regionally problematic sources of pollution from power plants, landfills and quarries. While the air pollution control district maintains air monitors that check for unhealthy levels of the larger sources, no health standards or monitoring exist for toxic pollutants.
The larger sources of pollution include fine particles such as soot, as well as carbon monoxide and sulfur oxides. They are the pollutants that trigger bad-air days in San Diego County.
Measuring pollution by criteria releases, which come from sources such as landfills, power plants and quarry operations, Carlsbad tops the list as the largest source of pollution. There, the 92008 ZIP code — home to the Encina Power Station — spewed 3.9 million pounds of pollutants into the air in 2004. The aging power plant is the region’s largest stationary source of pollution.
The Miramar landfill is close behind, emitting 3.3 million pounds of pollutants annually. The aging South Bay Power Plant is third (2.3 million pounds), the Sycamore landfill is fourth (2.1 million pounds) and the Otay landfill fifth (989,000 pounds).
|In the Air|
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The two power plants are major sources of carbon monoxide, a colorless, odorless — and poisonous — byproduct of the gas-fired plant’s combustion processes. The landfills are a large source of particle pollution, because trash trucks stir up dust rumbling over the landfill’s unpaved roads. Most particles produced there, however, are less dangerous to human health than the fine particles created from engine and power plant combustion. Because much of the dust is coarse, it does not penetrate deep into the lungs. Smaller particles are able to sneak deeper into the lungs, where they can aggravate asthma and cause chronic bronchitis.
The pollution is measured in pounds because the particles have weight. To understand how much air one pound of carbon monoxide pollutes, imagine this: One pound of carbon monoxide pollution would be enough to violate U.S. EPA ambient air standards in a cube of air that’s 115 feet on each side.
Then consider this: The Encina plant produced 2.9 million pounds of carbon monoxide in 2004 — a 700,000 pound increase from a year earlier. That’s enough to sully the air in 12 Empire State Buildings.
But businesses contribute just a small fraction — about 14 percent — of the region’s air pollution, according to the air pollution control district. Most of it, 76 percent, comes from cars, trucks and trains. Emissions from diesel combustion in trucks and buses poses the largest health risk in the air around us.
“You still have to keep an eye on the big picture,” said Tom Weeks, chief of the air pollution control district’s engineering division. “Most of our air pollution problems in San Diego are from cars and trucks. I don’t think that’s going to change.”
Businesses produce toxic air pollution in many ways. Benzene, a carcinogen, is in the gasoline you put in your car. Perchloroethylene, another carcinogen, is found in the chemicals used to dry clean your clothes. Hexavalent chromium, a carcinogen, is used in plating operations. The chemicals can lead to a variety of illnesses including lung cancer, leukemia and heart disease.
So should Escondido residents be concerned? Should they hold their breath? Or move to Warner Springs, where businesses produced the least pollution in 2004?
Not necessarily. Calculating the effect of exposure is complicated, health experts and regulators say. Because a drop of one chemical can be more dangerous than a gallon of another. And the emissions diffuse and migrate on the wind.
“It’s not an easy question to answer,” said Jenny Quintana, professor of environmental health at San Diego State University, “because it would depend on how long they live there, the hours that they breathe it, where they spend their time.”
The voiceofsandiego.org review found the following facts:
- The largest source of toxic air pollution among the county’s businesses are the hundreds of gas stations under regulation. While they’re required to maintain vapor-recovery systems to reduce emissions, 963 gas stations still emitted 18,000 pounds of benzene, a sweet-smelling chemical solvent that can cause leukemia. But that is a tiny fraction of what is produced when you drive your car. The California Air Resources Board estimates that automobiles produce 2.8 million pounds of benzene annually in San Diego County.
- Pollution from sources like power plants and landfills discriminates against the poor, who tend to live near these large sources. Areas where median household income is below $30,000 produced five times more pollution than areas where income levels exceed $70,000.
- Toxic air pollution, which is not monitored, is ubiquitous. It is distributed almost equally amongst all income levels, in part because gas stations and dry cleaners are common in all neighborhoods.
|The following zip codes recorded the highest amounts of two types of harmful air contaminants in 2004.
“It’s an equal opportunity polluter,” said Annette Kondo, a spokeswoman for the Los Angeles-based Coalition for Clean Air, an advocacy group. “It’s kind of surprising — your neighborhood dry cleaner, your neighborhood gas station.”
Environmental justice advocates note, however, that toxic hotspots can pop up even within ZIP codes that don’t top the most-polluting list.
“It’s important to keep in mind that you’re going to get a different picture if you look at different scales,” said Joy Williams, research director for the Environmental Health Coalition, a National City-based environmental justice nonprofit. Focusing on specific neighborhoods could reveal more localized impacts, she said, such as the auto body shops clustered around homes in National City’s Old Town.
“We should be looking at society-wide how we reduce that burden,” Williams said.
Some question how businesses’ emissions are calculated. City officials say theoretical models make the Miramar landfill appear to be a bigger pollution source than it is. The landfill has a 2.3-mile stretch of unpaved road that trash trucks must traverse to reach the dump’s working face. Linda Giannelli Pratt, chief of the city’s office of environmental protection and sustainability, said she believes it is the longest unpaved road in San Diego.
“If you go to our landfill, there’s not that much dust that you can visibly see,” Pratt said. “What is used in that calculation may not accurately reflect all of the mitigating things we’re doing to reduce the dust.”
The local air pollution control district uses EPA models to calculate emissions, Weeks said. A landfill’s emissions can depend on how dry the soil is, how fast trucks are driving, how many wheels they have.
“How accurate they are, there’s a lot of discussion about that,” Weeks said. “It’s the best science out there for estimating emissions. There’s always questions about how accurate that is, but it’s the best we have.”
San Diego’s air quality has been improving. Since 1989, San Diego County has seen an almost 75 percent cut in toxic air emissions, fueled by tightening state regulations and a growing scientific understanding of their effects. While all dry cleaners once used perchloroethylene, a sweet-smelling solvent, California is phasing it out over the next 10 to 15 years. The use of chlorinated solvents for degreasing in manufacturing and equipment repair has dropped.
Those cuts have helped reduce a lifetime resident’s background risk of developing cancer by about 70 percent — excluding emissions of diesel engines. Diesel emissions still constitute the largest cancer-causing risk in the air.
The air’s toxic pollutants increase lifetime cancer risk by about 520 people in 1 million. Diesel emissions are responsible for 80 percent of that risk.
Only about 2 percent of the risk comes from stationary sources, Weeks noted.
This article relates to: Science/Environment