Published — February 6, 2012 Updated — May 19, 2014 at 12:19 pm ET

Landmark diesel exhaust study stalled amid industry and congressional objections

Diesel exhaust, which some studies suggest causes lung cancer, spews from a crane loading a ship in Newark, N.J. Mike Derer/AP

Twenty-year investigation of miners exposed to toxic fumes still unpublished


Publication of a landmark government study probing whether diesel engine exhaust causes lung cancer in miners — already 20 years in the making — has been delayed by industry and congressional insistence on seeing study data and documents before the public does.

A federal judge has affirmed the right of an industry group and a House committee to review the materials and has held the Department of Health and Human Services in contempt for not producing all of them.


The much-anticipated study of 12,000 miners exposed to diesel fumes carries broad implications. If the research suggests a strong link between the fumes and cancer, regulation and litigation could ramp up — with consequences not only for underground mining, but also for industries such as trucking, rail and shipping.

Exposure isn’t limited to workers; people who live near ports, rail yards and highways also are subjected to diesel exhaust laced with carcinogens such as benzene, arsenic and formaldehyde.

But for the time being, at least, the results of an $11.5 million investigation by the National Cancer Institute and the National Institute for Occupational Safety and Health are under lock and key.

Richard Clapp, emeritus professor of environmental health at Boston University, is among several public health experts who called the situation unusual.

“I’ve never heard of an industry group demanding manuscripts from a government agency before a study has been accepted for publication,” Clapp said. “My guess is it would give the industry a chance to prepare their rejoinder early. They want to delay anything that’s going to implicate them in liability for lung cancer.”

Andrea Hricko, a professor of clinical preventive medicine at the University of Southern California who has followed the saga for years, suspects industry and Republican members of the House Committee on Education and the Workforce want to soften the blow of a statistically powerful government study that could have far-reaching impacts.

“They feel compelled to challenge it because they don’t want more regulations on mining equipment and locomotives and trucks,” Hricko said.

Henry Chajet, a Patton Boggs lawyer-lobbyist who represents the Mining Awareness Resource Group — known as MARG — declined to comment for this report. But in a recent court filing, Chajet and other lawyers for the group wrote that publication of what they believe to be an “inaccurate and faulty” study, along with government plans to notify the 12,000 subjects of health risks, is “likely to spawn public concerns, regulatory actions, and lawsuits…”

Industry officials say improvements in diesel engine technology are making the issue moot.

“Engine manufacturers have invested enormous resources over the last two decades to reduce emissions from diesel engines by over 99.9 percent,” the president of the Truck & Engine Manufacturers Association wrote in a Jan. 23 letter to leaders of the Education and Workforce Committee expressing support for the committee’s review powers. “As a result, today’s new technology diesel engines produce near-zero levels of particulate matter and toxic air contaminants and, thus, contribute significantly to improving the nation’s air quality.”

Diesel engines are known for their durability, however, and many older ones are still in use.

“It’s alarming that special interests appear to be trying to derail independent, peer-reviewed science,” Rep. George Miller, a California Democrat and ranking member of the Education and Workforce Committee, said in an emailed statement to the Center for Public Integrity. “Politics and profits should never be allowed to meddle with the scientific process, especially when health and safety are at stake.”

The panel’s Republican chairman said there is no such agenda. “The committee’s ongoing interest is to ensure the results of this research are accurate and meet the highest standards of scientific review,” Rep. John Kline of Minnesota said in a statement.

The legal and political tangling over the diesel study began in the mid-1990s, with countless twists and turns since. Last August, MARG won a contempt order against the Department of Health and Human Services, parent of the two institutes that conducted the study. The group alleged that HHS had deliberately withheld study materials from the House committee. U.S. District Judge Richard Haik of Lafayette, La., who had earlier granted the committee, along with mining companies and their scientists, the right to pre-publication review of such materials, agreed.

The Justice Department appealed the contempt order, which required HHS to hand over “all non-confidential documents, data, draft reports, publications, and draft results” associated with the study and to pay the plaintiffs’ court costs and attorneys’ fees. The order is stayed while the New Orleans-based U.S. Court of Appeals for the Fifth Circuit ponders the matter; a decision is expected soon.

All told, government researchers have written seven papers on the study, noteworthy not only for its large number of subjects but also because it controls for factors such as cigarette smoking. Four of the papers — describing only the study’s methodology — were published in the Annals of Occupational Hygiene in 2010. A fifth paper, also dealing with technical matters, has been accepted for publication by the same journal. Papers six and seven, which detail the study’s results, have been accepted by the Journal of the National Cancer Institute.

None of the last three papers can see the light of day until the legal dispute is resolved.

Worst case for the government: Haik’s contempt order stands and publication is postponed indefinitely while the House committee and MARG comb through mountains of documents and data. Best case: The order is overturned and the papers are published as soon as March.

In an affidavit filed with the Fifth Circuit, Dr. Robert Hoover, director of epidemiology and biostatistics at the National Cancer Institute, said it would be “unconscionable that there be further delay in publication” and noted that “several major organizations focused on public health are awaiting the results.”

Among them is the International Agency for Research on Cancer (IARC), an arm of the World Health Organization, which considers diesel exhaust “probably carcinogenic to humans” and is scheduled to revisit the science in June. The HHS study could play a major role in the IARC reassessment – assuming the findings are published by then.

Clapp, of Boston University, said the mining industry has an incentive to keep any bad news about diesel under wraps. “When IARC designates something a known human carcinogen, that changes the balance in these liability cases,” he said. “It makes it harder for industry to win.”

There have long been suspicions about diesel’s cancer-causing properties. A study published in Environmental Health Perspectives in 2004, for example, found elevated lung cancer death rates among U.S. railroad workers. “These results indicate that the association between diesel exhaust exposure and lung cancer is real,” the authors wrote.

John Froines, a professor of toxicology at UCLA and Hricko’s husband, said that more than 90 percent of the particles emitted in diesel exhaust are ultrafine — “smaller than a virus.” These diesel particles, coated with toxic chemicals and metals, can penetrate cells and cause cancer and other diseases, said Froines, director of the Southern California Particle Center, a government-funded research institute. The exhaust also contains vapors with “significant toxicity,” he said.

Industry experts say the evidence against diesel is far from conclusive. A scientist and a physician employed by Navistar, a manufacturer of diesel engines, wrote in a letter to the American Journal of Respiratory and Critical Care Medicine last year that “available data do not quantitatively link occupational [diesel] exposure to increases in lung cancer.”

The HHS study, conceived in 1992, was supposed to help settle the debate. But some early missteps by the government — using what MARG calls three “illegal” advisory groups to design the study, and filing one group’s charter with the wrong House committee — opened the door for a mining industry legal challenge in 1996. MARG is a collection of companies that mine salt, limestone and trona — a mineral used to make soda ash, an ingredient in glass, chemicals and other products.

The Education and Workforce Committee inserted itself into the dispute in 1999, when then-Chairman William Goodling, a Pennsylvania Republican, filed an affidavit with Judge Haik. “We have been concerned about the diesel study for several years,” Goodling said in the affidavit. He asked that the National Institute for Occupational Safety and Health (NIOSH), over which the committee has jurisdiction, be required to submit all data and drafts to members “for review and approval” prior to publication.

Haik granted the request in a 2000 order. The Justice Department appealed, saying Haik had improperly given the committee veto power over a scientific inquiry. The Fifth Circuit sided with the government, finding that Haik “cannot require Committee approval before publication of the study.” Instead, the court said, the committee would have 90 days to review the study data before it could be publicly released. Haik granted MARG the same privilege in a 2001 order.

Last year, as the final three papers were being readied for publication, Kline and another member of the Education and Workforce Committee, Tim Walberg, R-Mich., complained to NIOSH director John Howard that the government wasn’t complying with the 2001 order.

“We are troubled by the continued failure of NIOSH to produce the draft publications, data underlying the research reported in those draft publications, and other documents the Committee should be receiving based on instructions from the court,” Kline and Walberg wrote on July 8.

Rep. Miller, the Democrat, sent his own letter to Howard on Aug. 16. “The requirement for a pre-publication review by an interested party — and the insinuation of a congressional committee in such review — appears to deviate from the normal scientific process and threatens to undermine the integrity of these studies,” Miller wrote.

Two days later Haik granted MARG’s motion for contempt. The judge was unmoved by the Justice Department’s argument that HHS had complied with his 2001 order and that publication of the last three papers could be significantly delayed while “we have to produce [to MARG and the committee] every single piece of paper in the files of the Department of Health and Human Services having to do with that study.”

In a brief filed with the Fifth Circuit in October, the Justice Department characterized the MARG litigation as having been sparked by a “minor, inadvertent violation of the Federal Advisory Committee Act” — filing the HHS advisory panel charter with the wrong House committee — that was quickly corrected.

Compliance with Haik’s contempt order, government lawyers argued, “is a burdensome undertaking that will commandeer scarce resources. It would take [HHS] six months to a year to collect, review, and release the documents and data ordered disclosed. Moreover, disclosing the documents and data required by the court has the risk of foreclosing publication of the final results of the study.”

In his statement to the Center, Rep. Kline said, “In no way have [the committee’s] efforts delayed or compromised the department’s work. The results of these studies could have profound consequences for public policy and worker health, and we have a responsibility to ensure the agency gets it right.”

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