Malignant Mesothelioma Among Employees of a Connecticut Factory That Manufactured Friction Materials Using Chrysotile Asbestos: An Update

There is an ongoing argument about the potency of chrysotile asbestos to cause malignant mesothelioma. Authors of chrysotile risk assessments have relied upon the results of an epidemiologic study, published in 1984, to state that there were no mesotheliomas found among workers at a Connecticut friction products plant. McDonald reported the first two cases in 1986. In 2010, we reported the work histories and pathologic reports of five individuals from the Connecticut plant who were diagnosed with mesothelioma. Despite this, a review of the health effects of chrysotile published in 2018 continued to state that there were no cases of mesothelioma from this plant. We report here two new cases that were diagnosed after the publication of our previous report, bringing the current total to nine cases. We also discuss the results of previously unpublished air sampling data from the plant. Chrysotile, mainly from Canada, was the only asbestos fiber type used until 1957 when some anthophyllite was added in making paper discs and bands. Beyond this original description of the anthophyllite usage from McDonald, there is a dearth of information about the amount of anthophyllite used in the plant, the frequency of its use, and the specific departments where it was used. For over 30 years in the published literature, this factory has alternatively been described as a 'chrysotile' or 'predominantly chrysotile' factory. While it is clear that some anthophyllite was used in the factory (in addition to 400 pounds of crocidolite in the laboratory), given the volume, frequency, and processes using chrysotile, it still seems satisfactory to describe this cohort as a predominantly, but not exclusively, chrysotile-exposed cohort.