Anti-diesel rhetoric ignores scientific reality

Published November 1, 2000

The Environmental Protection Agency’s recent proposal for tough new rules on diesel emissions has been applauded by truck, bus, and engine manufacturers as a positive step toward improved air quality in the U.S. According to EPA Administrator Carol Browner, the new standards aim to make diesel trucks and buses “cleaner than the natural gas buses on the road today.”

What’s troubling is the persistence of those who refuse–even after EPA’s announcement–to accept that diesel can be made to burn so clean.

Calling diesel an “inherently dirty” fuel, these naysayers refuse to look beyond their outdated data on diesel emissions. This does a disservice to the environment, as clean diesel can be a large part of the solution to cleaner air.

The anti-diesel partisans also do a disservice to sound science, at times exaggerating the known dangers of diesel in order to support their agenda. No large-scale study with sound data on diesel exposure has ever been conducted. Indeed, only two studies have even purported to measure human exposure levels, and in both of those, mere guesses were made after the fact about exposure levels.

One study compared lung cancer rates among Teamsters who drove trucks and those who did not. During the time period covered by the study, most trucks on the road were fueled by gasoline, not diesel.

The second study, which focused on exposure to diesel emissions among railroad workers, was recently rated by the independent Health Effects Institute as being “of very limited utility.”

The importance of sound science

Finding answers to the questions about diesel emissions will not be easy. It will require further research, including partnerships among industry, labor, academia, and government. The largest such initiative to date–a $15 million study funded by International Truck and Engine Corporation and other engine manufacturers, EPA, and the California Air Resources Board–is now in its feasibility phase.

Diesel appears to have significant environmental advantages over other fuels, making research into its effects on human health even more important.

In research supported by International Truck and Engine, the Harvard Center for Risk Analysis found that natural gas–frequently cited as an alternative to gasoline or diesel–may increase “ultra-fine” particulate emissions in the atmosphere. Because ultra-fine particles may penetrate more deeply than larger particles into the respiratory tract, fuels that emit ultra-fine particles may pose more of a health risk than fuels, like diesel, whose emissions are less fine.

The Harvard study also found that diesel engines emit less carbon dioxide and methane, the principal “greenhouse” gases, than do natural gas-powered engines. In Europe, “green” diesel technology is viewed as an important element in efforts to comply with the Kyoto Protocol, the global warming treaty aimed at stabilizing greenhouse gas emissions.

Diesel fuel also appears to have a safety advantage over natural gas. “Natural gas is highly flammable,” the Harvard study notes, “and explosions are a common fear.” The National Fire Protection Association gives natural gas its highest hazard rating for flammability; diesel is considered only moderately flammable.

Storage of compressed natural gas (CNG) and liquid natural gas (LNG), both of which require extreme pressure and temperature conditions, poses hazards not encountered with diesel. LNG vessels must be equipped with relief valves to prevent an unsafe buildup of pressure that can occur when the LNG warms and changes to a gaseous state.

Diesel: Clean and getting cleaner

As we look for ways to improve air quality in the U.S. beyond, no proven fuel source, including diesel, should be rejected out of hand. International Truck and Engine has been at the forefront of the effort to clean up diesel.

In 1989, International was the first company to demonstrate a truly smokeless diesel engine. In 1996, it became the first engine maker to demonstrate the capability to meet the 2004 emissions standards set by the EPA.

In 1999, International achieved a technology breakthrough, combining cutting-edge engine technology with low-sulfur fuel and after-treatment technology to significantly reduce particulate and hydrocarbon emissions.

Current tests of that approach, called Green Diesel Technology , show it has reduced particulate emissions to a level lower than EPA’s newly proposed regulations for 2007, and 50 percent below the levels achieved by the cleanest natural gas engines available today. Green Diesel engines boast hydrocarbon emissions lower than can be measured using current technology.

All of these innovations, including work done by progressive oil companies such as ARCO to provide ultra-low-sulfur fuel, would not have been possible if the country had given up on the diesel alternative.

Dismissing diesel as “dirty” without conducting the proper research is not just scientifically invalid–it’s dangerous. Such junk science has real-world implications, depriving us of new approaches to diesel that can dramatically improve public health and the environment.

Dr. William B. Bunn is vice president for health, safety and productivity for International Truck and Engine Corporation.