More than 300 public health scientists, doctors and occupational safety experts have written to President Obama to urge him to intervene personally to move along a proposed rule on crystalline silica that has been under review within his Administration for nearly a year.

The letter, dated Jan. 25, asks Obama to direct the Office of Management and Budget (OMB) to complete its review of a proposal to regulate silica sent to it by OSHA on Feb. 14, 2011.