C. L. Sheckler to J. M. Fletcher on Rising Dust Counts at the Advocate Mine (1969)

A two-page memo of January 7, 1969, from C. L. Sheckler of J-M's Environmental Control Department to J. M. Fletcher at the Advocate asbestos mine in Newfoundland, reviewing the mine's 1968 annual industrial hygiene survey. The dust stations above the threshold limit value (TLV) had risen from 10 of 54 in 1965, 8 of 53 in 1966 and 12 of 52 in 1967 to 23 of 53 in 1968. Sheckler gave three possible reasons: a new microscope had replaced the old one, the former industrial hygienist, Mr. Sterland, may have shortened sampling times to finish the survey quickly, or "conditions may have been such that resulted in high counts."

What it shows

Sheckler notes that the counting method itself had not changed and followed the U.S. Public Health Service method. He enclosed J-M's impinger procedure and a draft of the new membrane filter method the company would begin using that year, and suggested that Advocate's engineer train at the Manville area industrial hygiene laboratory so that sampling would be consistent. The memo shows the share of Advocate's stations over the limit more than doubling in a year, with headquarters unsure whether the cause was the counting or the dust. J-M's own engineers recorded the same worry across the company a few months later (Environmental Control Subcommittee, March 1969).

In Johns-Manville's chronology

Johns-Manville's own chronology of what the company knew describes this document as follows:

Memorandum from C.L. Sheckler to J.M. Fletcher (Advocate), regarding Industrial Hygiene Survey for the year 1968, dated 1/7/69. Sheckler reviewed the prior four years of Industrial Hygiene surveys and found that in 1965--10/54 dust stations were above TLV; in 1966--8/53 dust stations were above TLV; in 1967--12/52 dust stations were above TLV; and in 1968--23/53 dust stations were above TLV.

Sheckler offered three possible explanations for the apparent decline in workplace conditions at Advocate: first, the newly purchased microscope might simply have resulted in more accurate current counts; secondly, the former industrial hygienist (Sterland) might have underestimated the earlier levels by allowing too little time for the accurate collecting of samples; or third, workplace conditions might actually have deteriorated. Sheckler noted that Sterland was no longer employed by J-M and suggested that future surveys be more closely coordinated by the Manville laboratory.