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ACES study finds no cancer in rats exposed to exhaust from US 2007 diesel engines

28 January 2015

The Health Effects Institute (HEI) released the final report from the health effects evaluation stage of the Advanced Collaborative Emissions Study (ACES, Phase 3). After a comprehensive evaluation of lifetime exposure of laboratory animals to “new technology diesel exhaust”—i.e., exhaust produced by heavy-duty, onroad diesel engines meeting the US EPA 2007 emission standards—the study found no evidence of carcinogenic lung tumors. The study also confirmed that the concentrations of PM and toxic air pollutants emitted from new technology engines are more than 90% lower than emissions from traditional older diesel engines.

The study exposed laboratory rats 80 hours a week, for up to 30 months, to emissions from a US EPA 2007 heavy-duty diesel engine equipped with a diesel particulate filter (DPF) and other emission control technologies. In contrast to previous health studies of older diesel engines, the ACES study found that lifetime exposure did not induce tumors or pre-cancerous changes in the lung and did not increase diesel emission related tumors in any other tissue. A few mild changes were seen in the lungs, consistent with long-term exposure to NO2, a diesel emission component that has been substantially reduced in US EPA 2010 and later model year engines.

The ACES results are expected to play an important role in future risk reviews of diesel engines by international and US agencies, said the HEI. Health effect studies of diesel emissions from older, uncontrolled diesel engines—involving exposures of both animals and humans—have led to the classification of diesel exhaust as carcinogenic to humans by the International Agency for Research on Cancer (IARC) in 2012.

Diesel particulate filter technology has been used on all diesel engines meeting the US EPA 2007 and later emission standards for heavy-duty onroad engines, as well as on all US EPA Tier 2 and later light-duty diesels. Over 30% of the trucks and buses in use today on US roads meet the new emission standards—said the HEI—and are equipped with DPFs. However, EPA emission regulations have not succeeded in forcing the DPF technology on new nonroad engines, with a large proportion of Tier 4 engine families being certified without DPFs.

The study—HEI Research Report 184: Advanced Collaborative Emissions Study (ACES): Lifetime Cancer and Non-Cancer Assessment in Rats Exposed to New-Technology Diesel Exhaust—was conducted by a team lad by Jacob D. McDonald of the Lovelace Respiratory Research Institute, Albuquerque, New Mexico. The work was overseen by independent experts on the HEI ACES Oversight Committee and reviewed by an expert ACES Review Panel.

ACES is a comprehensive effort, supported by a range of public and private entities, conducted under the oversight of HEI and the Coordinating Research Council. The overall goals of ACES were to test the emissions of new-technology diesel engines to determine whether they are achieving the expected reductions in emissions and health effects, and also whether the new control technologies (that include particulate filters and ultra-low-sulfur diesel fuel) are not resulting in unintended increases in some emission components. Earlier ACES reports found substantial reductions in particulate mass and numbers, as well as in other pollutants in the emissions from both 2007 and 2010 engines.

Source: Health Effects Institute