NIOSH has determined that diesel exhaust is a potential human carcinogen, based on a combination of chemical, genotoxicity, and carcinogenicity data. In addition, acute exposures to diesel exhaust have been linked to health problems such as eye and nose irritation, headaches, nausea, and asthma. Currently, underground miners can be exposed to over 100 times the typical environmental concentration of diesel exhaust and over 10 times that measured in other workplaces. In addition, miner exposure to diesel emissions promises to become more widespread as diesel equipment becomes more popular within the mining community.
http://www.cdc.gov/niosh/mining/topics/topicpage2.htm