Victory over one of the most intractable pollutants in the Los Angeles region is close at hand, thanks to a decades-long effort to cut auto exhaust.
Since the first Model Ts rolled off the assembly line, cars and trucks have been veritable carbon monoxide machines. The potentially deadly colorless, odorless gas -- linked to heart attacks, asphyxiation and birth defects -- is a product of inefficient combustion.
Few places in the nation have suffered as severely as the Los Angeles region, home to 10 million vehicles. Despite so much traffic, just one day of unhealthful carbon monoxide has occurred across Los Angeles, Orange, Riverside and San Bernardino counties in the last two years. No violations have been reported so far this winter.
Air quality officials have their fingers crossed. If no more violations occur this year, the region can be removed from the list of cities where the pollutant is a health hazard.
"The reduction of carbon monoxide is really another great success story in air pollution control in Southern California. This is another major pollutant that we have cleaned up on the road to clean air," said Sam Atwood, spokesman for the South Coast Air Quality Management District.
Improved auto emission-control devices and reformulated gasoline, beginning in the late 1980s, have been largely responsible for the reductions.
Although a 2002 poll of Californians found that people believe pollution is getting worse, the Southland's air quality has improved dramatically over the last decade. Carbon monoxide is the fourth major pollutant targeted under the Clean Air Act to be tamed in the Los Angeles Basin. The others are nitrogen dioxide from power plants, factories and auto exhaust; sulfur dioxide, an industrial pollutant; and lead from gasoline.
Nevertheless, the region still has some of the nation's dirtiest air, because of continuing problems with ozone, soot and dust. Those pollutants must be significantly curtailed by 2010, although even that wouldn't completely clean the air.
A generation ago, unhealthful levels of carbon monoxide were present one day in three across a wide swath of the basin. During the mid-1970s, unsafe concentrations of the pollutant spread from Reseda to Costa Mesa, from downtown Los Angeles to San Bernardino. Since then, the pollutant has all but disappeared from Orange County and the San Fernando and San Gabriel valleys.
The only remaining carbon monoxide hot spot is Lynwood, south of downtown Los Angeles. Peculiar circumstances conspire against that community.
Carbon monoxide is unlike other pollutants because it is trouble from the moment it spews out of a tailpipe. Tens of thousands of cars whizzing along the Century Freeway to Los Angeles International Airport or along the Long Beach Freeway bathe Lynwood in emissions.
Also, because of a quirk of human engineering and nature, the concrete-lined Los Angeles River functions as a drainpipe, funneling emissions from traffic in downtown Los Angeles to Lynwood, said Joe Cassmassi, senior meteorologist for the AQMD. Winter is when the worst carbon monoxide pollution occurs, because colder temperatures cause smog-control devices on cars to be less effective, and unusually low atmospheric inversions concentrate pollutants over the central city.
Nevertheless, the pollutant is in rapid retreat even in Lynwood. Only one day of unhealthful pollution occurred there last year, and none was reported in 2001. By contrast, excessive pollution occurred there 30 days annually a decade ago, according to the AQMD.
Calexico, where cars from Mexico that lack up-to-date emission controls are common, is the only other California city to violate the carbon monoxide standard, according to the EPA.
The hard-to-detect gas is what can kill people inside idling cars in garages or when hibachi-style barbecues are used, ill-advisedly, indoors. Unlike other pollutants, it does not directly affect the lungs. Rather, it displaces oxygen in the blood, causing internal asphyxiation. More commonly, it can cause dizziness, chest pain and angina.
One recent study by researchers at UCLA showed that women exposed to high levels of carbon monoxide and ozone were three times more likely to have babies with heart-valve defects than other women. Other studies have found that carbon monoxide can cause angina and irregular heart rhythms in Los Angeles commuters with preexisting heart conditions, said Dr. Henry Gong, professor of preventive medicine at USC.
As cars have become cleaner and cleaner, carbon monoxide levels have fallen throughout California. A new car today produces one gram of carbon monoxide per mile of driving, down from 23 grams in 1970, according to the state Air Resources Board. As more new cars with advanced emission-control systems, running on reformulated fuels, take to the streets, carbon monoxide levels are falling 5% a year in California.