OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

May 1, 1995



SUBJECT:         An error in the 1910.1000 Z-Tables

The Office of Technical Support in Region VII recently brought to our attention possible error in Table Z-3 of the 1910.1000 Z Tables. In Table Z-3 of the 1994 CFR (attached) the formula for the Coal Dust PEL with less than 5% quartz is:

2.4 mg/m(3) ----------- %SiO(2) + 2

While the PEL formula for Coal Dust with Greater than 5% Quartz is:

10 mg/m(3) ------------ %SiO(2) + 2

As written in the current CFR, the coal dust sample with less respirable crystalline silica would have a lower PEL than the sample wit ha higher respirable silica content.

The error appears to have occurred between the 1988 and 1989 editions of the CFRs. In the 1988 edition (attached) the PEL for Coal Dust with less than 5% quartz is listed as 2.4 mg/M(3). Under this PEL there is the work "or" which then refers one to the PEL formula for establishing a PEL where the quartz content is greater than 5%.

Accordingly, the CFR should be changed to list the PEL Coal Dust with less than 5% silica as just 2.4 mg/m(3). The PEL formula for greater than 5% silica would remain the same.

A second error was also noted in the same table. The PELs for crystalline silica list the formula for establishing a PEL as million particles per cubic foot (mppcf) only for a respirable dust sample. The collection method (although no longer used) for determination of mppcf allows only a total dust sample. The PEL is listed as a respirable sample and should be moved over into the total dust position.

Hopefully we can get these two items corrected for the 1995 edition of the CFR. If you have any questions please contact Richard Fairfax of my staff at 219-8036.