Since underground conditions vary between coal mines and metal and nonmetal mines, the regulations take different approaches to reduce DPM exposure to the same level. Following publication of the regulation, metal and nonmetal mines have up to 18 months to reach compliance with the interim concentration limit in their underground operations. These operators have the option of using engineering controls and best practices to reduce DPM to the proper limit. In underground coal mines, the new rule sets a specific emission limit of 2.5 grams per hour of DPM for permissible and non-permissible equipment. These limits will be phased in for an operation's existing equipment inventory over a 48-month period, but new equipment must meet the emission limits sooner.
Annual training is required for all underground miners exposed to diesel emissions.
Workers will be trained on the health risks associated with DPM exposure, control methods being used at the mine, identification of personnel responsible for maintaining those controls, and actions miners must take to ensure the controls operate as intended. MSHA estimates that at least 8.5 cases of lung cancer per year will be avoided as a result of the metal and nonmetal rule, and at least 1.8 cases per year will be avoided as a result of the coal rule. MSHA first proposed regulations regarding diesel emissions in April 1998 for coal mines and October 1998 for metal and nonmetal mines. Public hearings were held in November and December for the coal rule and the following May for the metal and nonmetal rule. Public comments were accepted on the coal rule for 15 months and on the metal and nonmetal rule for nine months.