The Dirt on Diesel
By Lily Auliff

We’ve all experienced it. Driving down any Houston highway, you wince as the diesel truck in front you releases a cloud of dense, black smoke. What are the health effects of diesel exhaust, and what is being done in the Houston area to alleviate them?

The Extent of the Problem
In the United States, diesel-powered vehicles release more than two-thirds of all particulates and almost half of all nitrogen oxides (NOx) from transportation, according to the Union of Concerned Scientists (UCS).

Health Effects
Diesel engines release a variety of pollutants, each with its own health effects.

Particulate matter is of utmost concern, as it is known to irritate the eyes and nose, aggravate respiratory problems, and lead to heart problems. Particulates have also been directly associated with an increased risk of premature death. In fact, a somewhat controversial study by the Clean Air Task Force in 2000 credited particulate matter emitted by power plants with 201 premature deaths annually in the Houston region.

NOx is a principal precursor to ground-level ozone smog. Ozone smog causes a variety of respiratory problems, including decreased lung capacity, exacerbation of asthma, inflammation of lung tissue, and secretion of mucus into respiratory passages.

Diesel exhaust also contains 41 chemicals that are identified by the state of California as toxic air contaminants. Their health effects vary, but some are considered potential human carcinogens. High-level exposure to diesel fumes has caused lung tumors in rats, and studies routinely associate them with a greater risk of lung cancer in humans.

Clean Up Options
There are several ways to make diesel burn cleaner, which can be used alone or in various combinations for maximum effect, explains Dewayne Huckabay, former city of Houston employee and air quality expert.

Cleaner burning diesel fuels include diesel emulsions and lower sulfur diesel in various grades. Catalytic converters, some of which require the use of lower sulfur diesel, filter pollutants from the exhaust. A process termed repowering, which recirculates exhaust through combustion, can also achieve significant emissions reductions.

Replacing diesels with cleaner alternative fuel vehicles may be even better. “While improvements to existing diesel engines and fuels are necessary, they are not a long-term solution. Alternative fuels and advanced engines can provide larger gains,” advocates UCS.

Diesel and the SIP
Previous drafts of the State Implementation Plan (SIP) to reduce ground-level ozone in the Houston-Galveston region included several controls on diesel fleets. Those measures would have banned operation of construction equipment in the morning, required the purchase of cleaner off-road diesel equipment earlier than federal law mandates, and required the use of cleaner burning diesel fuel.

However, the 77th Texas Legislature removed these controls, replacing them with Senate Bill 5 and the Texas Emissions Reduction Plan (TERP). TERP is a voluntary program that provides funding for cleaner on- and off-road engines, energy efficiency programs, and the purchase of cleaner fuels, among other pollution reduction strategies. Much of the money to pay for these improvements would come from a tax on cars brought into the state.

Because TERP is a voluntary program, no one is exactly sure how effective it will be. But preliminary funding obstacles indicate it may fall far from meeting its goals. Huckabay projects that only a quarter or possibly a third of the funds proposed in the original legislation may be available, because several car dealerships are suing, saying the new tax would illegally impede interstate commerce.

Huckabay is disappointed that the earlier diesel control measures were not maintained as contingency plans, in case TERP is not effective.

Barriers
Huckabay explains that one of the main barriers to cleaning up diesel has been the lack of affordable and available technology.

Cleaner diesel can cost upwards of $0.25 per gallon.

Catalysts that achieve the pollution reductions that the Houston region is looking for are also difficult to find. “Unfortunately, there isn’t a magic way to deal with both particulates and NOx at the same time easily,” explains Huckabay. “The manufacturers’ research and production have focused on particulate reductions, because that’s where California’s problem is. And they’ve been very effective, but they haven’t put any energy into dealing with NOx, which is Houston’s focus.” Huckabay explains.

Not to mention that discussions with manufacturers still revolve around after-market retrofits. Diesel engines featuring the needed pollution control equipment just don’t come straight off the assembly line.

Luckily, the EPA is moving forward with regulations that are expected to reduce diesel pollution from new heavy-duty trucks and buses by 95 percent. If all goes as planned, these requirements are scheduled to be completely implemented by 2010. That may be too late to help Houston attain federal air quality standards, but the mandate will push manufacturers into providing readily available and reasonably priced technology.

Grassroots Solutions
Until federal regulations kick in, the Texas Campaign for the Environment (TCE), based in Austin, is using public pressure to clean up diesel emissions. “Since last summer, we’ve been educating folks about the health effects and health problems associated with diesel and urging institutions to take steps to clean it up,” says director Robin Schneider.

TCE organized a community letter writing campaign, which has convinced Austin Independent School District to switch to a cleaner burning diesel fuel. Their next target is the Texas Department of Transportation (TxDOT). Already more than 1,000 letters have been sent to TxDOT, which has the largest diesel fleet of any state agency.

A Note on Passenger Cars
Diesel automobiles generally get better gas mileage than their gas counterparts. But, “even in gasoline-powered cars, fuel efficiency does not necessarily mean lower emissions,” explains Schneider.

Efficient diesel engines can reduce greenhouse gas emissions by up to 30 percent over their gas-powered equivalents, but they produce more particulates, nitrogen oxides, and air toxics. Therefore, even though the 2002 diesel Volkswagon Beetles, Golfs, and Jetas all achieve 42 miles per gallon in the city and 49 to 50 miles per gallon on the highway, they all scored the worst possible rating on the EPA Air Pollution Score.

The UCS also warns that developing a diesel market helps automakers easily achieve federal fuel economy standards – and allows them to offset their diesel sales with heavier, high-performance, high-polluting vehicles.

“Car manufacturers should be harshly criticized for making a massive setback in our air quality through the kinds of cars they promote,” Schneider adds.