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June 9, 2003 

Tractors, Bulldozers and other

Tractors, Bulldozers and other

June 9, 2003

Tractors, Bulldozers, and Other "Off-Highway" Diesel Equipment Double Toxic Particulates from Mobile Sources
New Report Finds New York, LA, Houston, Boston, and Chicago Areas Have Greatest Emissions; EPA Proposal Would Cut Off-Highway Diesel Pollution 90 Percent If Turned into Law

BERKELEY, CA, June 9 - In a new analysis released today by the Union of Concerned Scientists (UCS), previously inaccessible emissions data reveal the dramatic impact of off-highway diesel engines—which power tractors, bulldozers, trains, and ships—on each county, major metropolitan area, and state across the country. The New York, Los Angeles, Houston, Boston, and Chicago metropolitan areas top the list for the amount of emissions of particulate matter (PM) from these engines, and the Los Angeles and New York metropolitan areas have the highest emissions of smog-forming nitrogen oxides (NOx). Texas, California, Illinois, Louisiana, and Ohio have the highest PM emissions among the states. Nationwide, emissions from more than six million off-highway engines account for nearly 50 percent of all PM pollution from mobile sources, totaling 255,286 tons—the equivalent of PM emissions from more than 17 million new diesel transit buses.

The new UCS report compiled and analyzed the latest emissions inventory from the Environmental Protection Agency (EPA) and California Air Resources Board. The study found that in the New York metropolitan area, off-highway diesel engines emitted more tons of particulate matter than in any other area evaluated. New York-area off-highway diesel engines emitted 7,623 tons of PM pollution and 76,738 tons of NOx in 1999—amounts equaling particulate emissions from 509,211 new diesel transit buses and nitrogen oxide emissions from 218,139 buses.  Four major metropolitan areas along the East Coast corridor—Boston, New York, Philadelphia, and Washington D.C./Baltimore—have some of the highest concentrations of off-highway diesel emissions in the country.  

"Despite substantial progress in technologies that reduce diesel pollution, a double standard allows off-highway engines to pollute at high levels," said Patricia Monahan, UCS senior analyst and author of the new report, Cleaning up Diesel Pollution: Emissions from Off-Highway Engines by State. "Unlike diesel trucks and buses, construction and agricultural equipment are held to weak standards and public health pays the price. It is imperative that we hold all diesel engines to the same standard."

Small enough to be inhaled deep into the lungs, diesel exhaust particles are linked to cancer and premature death, as well as serious respiratory illness. The dangers of diesel exhaust have led to stricter tailpipe standards for highway trucks and buses over the past thirty years, but off-highway engines are allowed to pollute at much higher levels. As a result, while particulate pollution from highway vehicles has been cut in half over the last two decades, emissions from off-highway engines have increased 23 percent.  Compared to a new highway diesel truck or bus, heavy diesel equipment (50 horsepower or greater) manufactured in 2007 can release 15 to 30 times more particulate matter and about 15 times more nitrogen oxides.

The EPA recently proposed a rule that would reduce PM and NOx emissions from new off-highway diesel engines by 90 percent. Hearings are scheduled in New York City (June 10), Chicago (June 12), and Los Angeles (June 17). Though the current proposal would exclude trains and ships from stricter emission standards, the EPA estimates that by 2030, the rule could prevent 9,600 premature deaths and save $81 billion per year.

"The EPA under Christie Todd Whitman has given us a good proposal—one of the very few environmentally sound actions of the Bush administration," said Kevin Knobloch, executive director of UCS. "But it is still just a proposal. Without Whitman at the helm, there is a considerable chance this rule will be undermined. The stakes for public health are too great to let that happen."

A recent analysis by an association of state air regulators found that diesel exhaust—a mixture of nitrogen oxides, particulate matter, arsenic, dioxin, and mercury—increase the incidence of cancer in the United States by as many as 125,000 additional cases over a 70-year lifetime. California air officials estimate that diesel exhaust causes 70 percent of the state's airborne cancer risk from toxic pollution. Preliminary data released today by Northeast States for Coordinated Air Use Management (NESCAUM), a nonprofit association of the eight Northeast air quality agencies, found that off-highway heavy-duty diesel engines can make surrounding air quality as much as 16 times more polluted, suggesting that the health threats for workers and nearby residents may be even more significant than previously recognized. The interim NESCAUM summary is available at

The UCS study breaks down pollution data on off-highway diesel engines and other mobile sources in all states, counties, and major metropolitan areas. The report also provides a cost analysis of producing cleaner engines, finding that for one to three percent of the cost of equipment, pollution controls for particulate matter and nitrogen oxides can cut emissions by 90 percent or more. For the entire UCS report and local emissions data, see:


The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with citizens across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.

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