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Slide 19


    Title: What is the OSHA PEL for Construction?

    • Quartz (respirable dust):
      250 mppcf
      % silica + 5

    • OSHA-adopted conversion factor:
      1 mppcf = 0.1 mg/m3 respirable dust
    [Includes the OSHA logo]

    Speaker Notes:

    What is an overexposure in Construction and Maritime?

    The crystalline silica PELs for Construction and Maritime are found at 29 CFR 1926.55(a) and 1915.1000 respectively. These PELs are expressed in terms of millions of particles per cubic foot (mppcf) and are based on a particle count method that is obsolete.

    OSHA consulted with NIOSH for help in converting sampling results obtained by the contemporary gravimetric method, to mppcf. NIOSH recommended a conversion factor of
    1 mppcf – 0.1 mg/m3 respirable dust.

    A detailed discussion of the use of this conversion factor can be found in Appendix E of the NEP Instruction.