NIOSH Respiratory Diseases Research Program

5.4 Lung Cancer Induced by Diesel Engine Exhaust

 5.3 Silica-Induced Lung Cancer

5.4a) Risk Assessment for Diesel Exhaust 

RDRP scientists drafted a “Current Intelligence Bulletin on Carcinogenic Effects of Exposure to Diesel Exhaust,” which NIOSH published and disseminated in 1988. It included estimates that 1.35 million workers in 80,000 workplaces were then exposed to diesel exhaust, described health effects of exposure, and recommended that whole diesel exhaust be regarded as a potential occupational carcinogen and that reductions in workplace exposure would reduce cancer risks.150 An estimated 34,000 underground miners are potentially exposed to high concentrations (>0.5 mg/m3) of diesel particulate matter and another 200,000 surface mine workers are exposed to lower concentrations (<0.2 mg/m3).

In 2001, MSHA promulgated two “technology forcing” diesel exhaust standards for underground mines, one for coal mines (66 FR 5526 - A5-26) and one for metal and nonmetal mines (66 FR 5706 - A5-27). In coal mines, compliance was to be achieved by limiting exhaust emissions to 2.5 g/hr from heavy-duty equipment and to 5 g/hr from light-duty equipment (with exception for engines certified as EPA off-road Tier II or better). For all other underground mines, MSHA has proposed application of a final PEL of 160 µg/m3 total carbon (the sum of elemental carbon and organic carbon), with a five-year phase-in period of reduced limits starting with an interim limit of 308 µg/m3 elemental carbon (70 FR 53280 - A5-28).

Approximately 70 percent of the personal exposure samples taken in metal mines exceed the final PEL of 160 µg/m3 total carbon, and about 33 percent exceed the interim PEL. With the final PEL now scheduled to go into effect, the mining industry faces substantial challenges in moving to achieve compliance.

As described in more detail below, RDRP scientists have:

• Found diesel exhaust exposure to be a risk factor for lung cancer in coal mines
• Provided evidence to support promulgation by MSHA of a final rule for a diesel exhaust standard
• Helped develop and test a specialized sampler to monitor compliance with MSHA’s diesel exhaust PEL
• Assisted in investigations to demonstrate the feasibility of compliance with the MSHA regulations limiting diesel exhaust in underground mines
• Embarked on a study to understand and solve issues which are hindering proper implementation of controls to limit diesel particulate matter in mines