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ACES Phase 3 study finds few health effects from US 2007 engines

12 April 2012

First results of the final Phase 3 of the Advanced Collaborative Engine Study (ACES)—released today by the Health Effects Institute (HEI)—have found no evidence of gene-damaging effects in animals exposed to emissions from new technology diesel engines, and only a few mild effects on the lungs. The study is exposing rats and mice for 16 hours a day to emissions from a heavy-duty diesel engine meeting US EPA 2007 emission standards. These engines use diesel particulate filter systems that reduce PM emissions by over 90% from levels emitted by older engines.

The study found that exposures lasting one, three, and in some cases up to twelve months had effects on only a few of the many health markers tested. The few effects that were reported for the rats—including mild hyperplasia (cell proliferation) in the lungs and slightly reduced lung function—were most consistent with exposure to nitrogen oxides in the engine exhaust, said the HEI. NOx emissions are being further reduced under US EPA 2010 standards now in effect.

These results are expected to play an important role in upcoming risk reviews by international and US agencies of older and new technology diesel engines, including a review of the carcinogenicity of diesel exhaust in June, 2012 by the International Agency for Research on Cancer (IARC) in Lyon, France. “We will be communicating these results to IARC, the US National Toxicology Program, and US EPA in order to ensure that the significant improvements in emissions and effects for these new diesel technologies are considered and compared with the data on older engines when those agencies reach their conclusions,” said Dan Greenbaum, President of HEI.

The study—HEI Research Report 166: Advanced Collaborative Emissions Study (ACES) Subchronic Exposure Results: Biologic Responses in Rats and Mice and Assessment of Genotoxicity—was conducted by a team of researchers from the Lovelace Respiratory Research Institute (LRRI), Albuquerque, NM; Litron Laboratories, Rochester, NY; and the University of Texas Medical Branch, Galveston. The study was overseen by independent experts on the HEI ACES Oversight Committee and the results were peer-reviewed by a separate ACES Review Panel who had had no part in the conduct of the study. In their Commentary on the study the Review Panel concluded:

“Overall, these results indicate that rats exposed to one of three levels of diesel exhaust from a 2007-compliant engine for up to 12 months, for 16 hours per day, 5 days a week, with use of a strenuous operating cycle that was more realistic than cycles used in previous studies, showed few biologic effects related to diesel exhaust exposure.”

ACES is a comprehensive study of the health effects of exposure to new technology diesel engines, conducted under the independent oversight of HEI and the Coordinating Research Council. The overall goals of ACES are to test the emissions of new technology diesel engines to determine not only whether they are achieving the expected substantial reductions in emissions and health effects, but also whether new control technologies and ultra-low sulfur diesel fuel are resulting in unintended increases in some components of the emissions. The study has been structured into three phases:

In the Phase 3 studies, rats will continue to be exposed for their lifetime. In 2013, these investigators, along with others investigating potential vascular effects, will submit a comprehensive final report for peer review, providing a systematic look at the effects of long-term exposure to diesel exhaust emitted by these new technology diesel engines.

Source: Health Effects Institute