There are hundreds of underground mines in more than 20 states that are operational in the United States. Most of the metal and nonmetal mines, if not coal, are equipped with several thousand pieces of diesel equipment that are significantly affecting the health of more than 10,000 workers with diesel particulate matter (DPM), which is the primary air-quality concern in most of these mines. As per the current regulations of the U.S. Mine Safety and Health Administration (MSHA), an interim permissible exposure level (PEL) of 160 μg/m3 of total carbon (TC) has been imposed on mines since 2008. The concern of the International Agency for Research on Cancer (IARC) and other agencies combined with the outcome of one of the most extensive epidemiological studies on underground miners done so far, the Diesel Exhaust in Miners Study (DEMS-2012), jointly conducted by the National Cancer Institute (NCI) and the National Institute for Occupational Safety and Health (NIOSH), was enough to prompt a new series of research, especially, in underground mines. Moreover, recent evidence reports the highest level of exposure for underground mine workers (E.C.: 27-658 μg/m3), amounting to several hundred times of exposure at other occupational environments. Despite technological advances, which have proven successful in reducing DPM emissions to below 90 percent, the persistent problem and ultrafine size of DPM (<1 μm) seem to be undermining such improvements. The present study is a review of developments to date with substantial insight into how a different perspective of DPM can offer possible opportunities to achieve further prevention.
