Dr. George W. Wright to Dr. Paul Kotin on Whether Crocidolite Should Be Restricted More Than Other Asbestos (1975)

A three-page memo of February 28, 1975, from Dr. George W. Wright to Dr. Paul Kotin, titled "Should crocidolite be utilized in a more restrictive manner than other forms of asbestos?" Wright reviews the evidence: all types of asbestos had produced lung fibrosis and excess lung cancer, and excess mesothelioma had been reported with every variety except anthophyllite and tremolite. He discusses the cluster of mesothelioma on South Africa's Northwest Cape, Philip Enterline's findings and J. C. Wagner's animal studies, and concludes that the evidence was "inadequate to support a clear statement that crocidolite is more hazardous than other forms of asbestos," but was "provocative and possibly would justify a more rigorous standard" for crocidolite than for chrysotile, with amosite perhaps in between.

What it shows

Wright adds that where crocidolite or amosite was mixed with chrysotile, as in asbestos-cement pipe, a single standard for the mixture would almost certainly be stricter for the minor fiber, and J-M had "some actual dust count evidence" of this in pipe making. Within days J-M told a Canadian government meeting it was giving crocidolite no special handling (March 1975), and in June its Toronto plant argued against Ontario's proposed lower crocidolite limit (B. C. Machin, June 1975). The South African findings Wright weighs began with Wagner, Sleggs and Marchand (1960).

In Johns-Manville's chronology

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

Dr. Wright, in a memorandum to Kotin, 2/28/75, answers the question of whether crocidolite should be utilized in a more restrictive manner than other forms of asbestos? Dr. Wright states that the evidence is inadequate to support a clear statement that crocidolite is more hazardous, but the evidence is provocative and possibly would justify a more rigorous standard for it.