Study affirms diesel emissions technology, boosting efforts to replace old engines

Two decades ago, environmentalists slapped a controversial ad on the back of a public transit bus in New York City: “Standing behind this bus could be more dangerous than standing in front of it.” Part of the Dump Dirty Diesels Campaign, it was a blunt accusation that breathing diesel exhaust fumes could lead to death.

That campaign helped launch a nationwide effort to clean up diesel engines — those that power everything from heavy-duty pickup trucks to mammoth big rig trucks — by changing the composition of the fuel, changing the combustion process and attaching emissions control technology that, in theory, trapped soot and other chemicals.  

Just last month, the first study on this combination of fixes, put in place at the tail end of the Clinton administration, confirmed the new generation of diesel engines are indeed substantially cleaner. The findings by the Health Effects Institute found no evidence of cancer from a lifetime of exposure to the diesel fumes from engines meeting the more stringent U.S. Environmental Protection Agency standards.

The Boston-based research institute — a collaboration of the EPA, U.S. Federal Highway Administration, California Air Resources Board and stakeholders in the vehicle industry — also found a 98 percent reduction in emissions from older diesel engine models. 

The findings could dramatically shift public perceptions of the threats that diesel traffic can pose to dense urban areas, while bolstering those encouraging accelerated replacements and retrofits of older engines. 

“It’s a game-changing study,” said Frank O’Donnell, president of the Clean Air Watch, a nonprofit environmental advocacy group based in Washington D.C. “It absolutely confirms that modern pollution controls can convert the dirty diesel engine into something really clean and civilized.” 

Laboratory tests that experimented with diesel used to get a good laugh out of Mr. O’Donnell.

“The punchline was: The rat always died,” Mr. O’Donnell said. “Finally, we’re seeing a situation where the rat lives — and so do people.”

A need to study

The precise cancer risk of diesel exhaust has long been subject to debate. The level of risk has been tough to quantify, even among health agencies.

The World Health Organization classifies diesel emissions as a “known” carcinogen. The EPA concluded that diesel exhaust is “likely” to be carcinogenic to humans, but did not have enough evidence to express the risk as a specific value.

In 2013, an environmental threats assessment from the University of Pittsburgh found Allegheny County’s air quality was among the worst in the country, largely due to diesel exhaust.

“The Downtown area appears to be especially problematic because emissions from buses and trucks can become trapped in the ‘canyons’ formed by tall buildings,” the report noted.

EPA rules approved in 2001 called for all heavy-duty truck engines beginning with the 2007 model year to include a filter that removes soot and particulate matter.

By the 2011 model, the rules called for a catalyst device that removes nitrogen oxides before releasing nitrogen and water into the air. The rules also mandated that refineries remove from 97 percent of sulfur content from diesel fuel, since the substance would clog the filter.

Health Effects Institute President Dan Greenbaum said the industry had asked the institute for a comprehensive study on the 2007 engines, in part to affirm their investments but also to see if the changes would inadvertently result in any unforeseen emissions.

Researchers randomly selected tractor-trailer engines from four manufacturers and exposed fumes from those vehicles to a species of rat that had been exposed to older diesel in previous studies. The study exposed the animals to 16 hours of fumes per day, five days a week, for up to 30 months.

The entire study — including examinations of both the 2007-compliant and 2010-compliant engines, the 30-month rat exposure study on the 2007-complaint engine, and then a detailed peer review of the findings — took five and a half years.

“We actually bent over backwards to make this a tougher study,” Mr. Greenbaum said. “We wanted to make sure people could trust this information.”

Although the study and the associated EPA rules apply only to trucks classified as heavy-duty, the implications extend to other industries, said Allen Schaeffer, executive director of the Diesel Technology Forum, an industry group advocating the importance of diesel engines, fuel and technology. 

Diesel engines power freight locomotives and marine work boats, 90 percent of commercial trucks, 75 percent of transit buses and about two-thirds of all farm and construction equipment, according to data collected by the forum. 

“I think some were leery that the industry could meet such a systematic, aggressive challenge,” Mr. Schaeffer said. “The highway trucks were the pioneers.”

The cost of compliance is likely in the billions for the four or five major manufacturers of emissions control systems, said John Wall, vice president of technology development for Cummins engine Inc., a manufacturer in Columbus, Ind. 

The company spends about half of its annual $750 million research and development budget on developing more efficient technologies that can meet the standard at a lower cost, he said.

“When I saw those [study] results, man, that was a big day,” Mr. Wall said. “It’s wonderful to see the fruits of your labor worth it.”

A need to replace

Because the tougher EPA rules apply only to new heavy-duty truck engines, clean air advocates say the challenge becomes how to encourage the replacement or retrofitting of older trucks that are remarkably long-lasting.

Today, about 30 percent of trucks on U.S. roads are using 2007-or-later model year engines, and about 15 percent use the even further upgraded engine required in 2011 models. In Pennsylvania, about 36 percent of trucks on the road have the 2007 engines, and 18 percent have 2011-compliant engines. 

Mr. Wall looks at the rate of replacement as one of mileage, not number of trucks.

Long-haul trucks are typically re-sold within five years to smaller operators who drive them much shorter distances, he said, meaning the older, pre-2007 diesel engines are being driven fewer miles overall as the long-haul trucks are replaced with clean engines. Mr. Wall estimated more than half of all miles driven by trucks today are achieved using the new engines. 

Truck manufacturers also have gradually worked out some kinks, such as increasing fuel economy by 5 percent to 8 percent, Mr. Schaeffer said. But trucks today still cost as much as $15,000 more than those with the older engines. Achieving clean diesel engines on a local level will require a mix of mandated and voluntary initiatives, said Rachel Filippini, executive director of Group Against Smog and Pollution, a group concerned with air quality in southwestern Pennsylvania.

For more than a decade, the group has promoted rules against the unnecessary idling of vehicles and pushed for legislation, approved in 2011 by the Pittsburgh City Council, that require projects receiving at least $250,000 in public money to use a percentage of cleaner construction equipment.

Congress in 2005 established the Diesel Emissions Reduction Act, or DERA, to provide grant money for diesel retrofits and replacements, but that money has shrunk in recent years. The 2015 Obama administration budget proposal includes $10 million — a “drop in the bucket” of what’s needed, said Mr. O’Donnell of Clean Air Watch.  

The Allegheny County Health Department currently funds a grant program called “Build It with Clean Diesel” that provides up to $100,000 for small construction companies with at least half of their contracts in Allegheny County to upgrade their equipment with emissions control technologies, including the installation of filters and catalyst devices. “Really, it’s the economic drivers that will suggest how fast these new engines get into the population,” Mr. Schaeffer said. “There’s a cost for clean air, and it’s evident in these new trucks.”

Begun more than three years ago with $1 million, the program currently has about $600,000 in unallocated funds, according to the program administrator.  

A second county grant program offers to cover the full cost of purchasing and installing filters and catalysts for diesel fleets operating on Neville Island. 

 “In our region, we know that [diesel exhaust] is one of the greatest inhaled air toxic cancer risks,” she said. “It’s good to see a study come out that underscores the need to clean up fleet.”

Ms. Filippini hopes the HEI study’s results can encourage more funding for incentive programs and more state-level mandates.