Dr. Kenneth Smith and the J-M Research Center on Free Silica in Finished Products (1958–1959)

Thirteen Johns-Manville papers from January 1958 to July 1959. On January 24, 1958, Dr. Kenneth W. Smith, J-M's medical director, asked the company's Research Center to measure free silica in finished products, since it was believed the silica in them was converted to a combined form, yet dust on plant beams and rafters held "free silica when we would expect none" and "chest x-rays of some employees have uncovered occupational pulmonary disease where it was not expected," among Transite pipe saw and lathe operators, rigid shingle punch press operators, and magnesia finishing and packing workers. The Research Center's confidential report of May 6, 1959, found about 13 percent quartz in Transite pipe and cristobalite in all the Zelienople fire bricks tested, 30 percent or more in three of them.

What it shows

Smith also suspected that clay impurities at the Zelienople, Pennsylvania, brick plant were "converted in the ovens to crystobalite," which "would affect the employees who saw and package the brick." The study took over a year. In July 1959 Hugh M. Jackson, manager of J-M's industrial health program, sent the report on, noting "substantial percentages of crystobalite in each of our types of fire brick products" and recommending that all Zelienople work areas with brick dust be held to 5 million particles per cubic foot, the limit the U.S. Public Health Service had urged for cristobalite-bearing dust (1958 diatomite report), with added attention to tuberculosis in plant examinations. A planned silica dust survey at Zelienople had been put off in 1957 to save money (1957 memo).

In Johns-Manville's chronology

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

On 1/24/58, K.W. Smith requested that J-M R & D investigate the amount of free silica present in J-M finished products. Smith noted that it had been believed that the only silica remaining in J-M finished products was in a combined rather than a free-form but that in-house industrial hygiene surveys had detected free silica on beams and rafters within J-M plants where none would have been expected. Moreover, "physical examinations and chest x-rays of some employees have uncovered occupational pulmonary disease where it was not expected. Typical examples of these operations would be the saw and lathe operators in Transite pipe, the punch-press operators in rigid shingles or finishing and packaging magnesia products. In addition, we suspect that silica occurring as an impurity in some clays used at Zelienople may be converted in the oven to crystobalite. This, of course, would affect the employees who saw and packaged the brick." R & D studies established that certain J-M finished products contain sufficient levels of free silica to warrant monitoring of work stations within J-M and controlling exposures within the then-accepted TLV of 5 mppcf.

Editor's note: J-M's description says the research studies established that certain products held enough free silica to warrant monitoring within the 5 mppcf limit. The Research Center tested Transite pipe, a Transite shingle and Zelienople bricks; the monitoring recommendation came from H. M. Jackson in July 1959 and applied only to Zelienople.

Related documents

• R. H. North to J. Goldfield Cancelling the Zelienople Dust Survey (1957)