toxins on the track

For years, government scientists who measure air pollution assumed that diesel locomotive engines were relatively clean and emitted far less health-threatening emissions than diesel trucks or other vehicles.

For years, government scientists who measure air pollution assumed that diesel locomotive engines were relatively clean and emitted far less health-threatening emissions than diesel trucks or other vehicles. But not long ago, those scientists made a startling discovery: Because they had used faulty estimates of the amount of fuel consumed by diesel trains, they grossly understated the amount of pollution generated annually. After revising their calculations, they concluded that the annual emissions of nitrogen oxide, a key ingredient in smog, and fine particulate matter, or soot, would be by 2030 nearly twice what they originally assumed.

That means that diesel locomotives would be releasing more than 800,000 tons of nitrogen oxide and 25,000 tons of soot every year within a quarter of a century, in contrast to the Environmental Protection Agency8217;s previous projections of 480,00 tons of nitrogen dioxide and 12,000 tonnes of soot.

Research has linked soot and smog to premature heart attacks, as well as to lung disease and childhood asthma, leading environmental activists to argue that the government has no choice but to impose tighter rules on locomotives.

The EPA announced two years ago that it was drafting rules to clean up trains and marine vessels: Any rule would likely force manufacturers to redesign their engines and install controls on trains8217; exhaust.

According to Association of American Railroads spokesman Tom White, diesel trains are three times as fuel efficient as trucks, having reduced their fuel consumption by 70 percent over the past 25 years, and emit a third of the pollution trucks release when transporting the same weight over a comparable distance. 8220;Today, rail is simply cleaner than trucks,8217;8217; White said. 8220;Nothing that has been said changes that.8217;8217;

Trucks emit more than three times as much soot as trains a year and well over twice as much nitrogen oxide, according to the EPA8217;s most recent data. But locomotives8217; advantage in terms of pollution is expected to erode over time as diesel-powered trucks and buses meet new federal standards. By 2030, trains will emit almost twice as much soot as trucks: 25,000 tonnes to 14,000.

State and local environmental officials say they need tougher pollution curbs on trains as soon as possible to meet the federal air quality standards that will take effect in the next few years.

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Kathleen A. McGinty, head of Pennsylvania8217;s Department of Environmental Protection, said the proposed standards for train emissions are particularly important because train traffic will increase in the coming years. 8220;For us, clean trains is a growth industry,8217;8217; she said.

Communities located near rail yards experience the highest level of pollution. Two years ago, the California Air Resources Board analyzed diesel pollution from the Roseville Rail Yard, the largest service and maintenance rail yard in the West, through which more than 30,000 trains pass each year. The study found that the cancer risk level for as many as 26,000 nearby residents averaged between 100 and 500 in a million, meaning that the exposure nearly doubled the lifetime cancer risk for these residents.

8220;They8217;re breathing in this stuff all the time,8217;8217; said Diane Bailey, a scientist at the advocacy group Natural Resources Defense Council. Bailey added that many trains idle three-quarters of the time they are in rail yards, and that, compared with trucks and buses, locomotives are 8220;lagging so far behind other diesel equipment.8217;8217;

Juliet Eilperin