30 U.S.C. § 845: Dust standards in presence of quartz

In coal mining operations where the concentration of respirable dust in the mine atmosphere of any working place contains more than 5 per centum quartz, the Secretary of Health and Human Services shall prescribe an appropriate formula for determining the applicable respirable dust standard under this subchapter for such working place and the Secretary shall apply such formula in carrying out his duties under this subchapter.