The re-created compound was applied to wallboard, allowed to dry and then sanded. The dust was shipped to a laboratory near Geneva, where Bernstein supervised a series of rat experiments. Lab workers wore “moon suits” to protect themselves from asbestos fibers.
In a pilot study, the rats were divided into three groups of 14 and confined in tubes for five days, six hours a day. The control group breathed filtered air. The second group breathed chrysotile fibers, the third a mixture of chrysotile and aerosolized joint compound particles.
The rats were killed after exposure and their lungs and pleural tissue were examined. The “chrysotile exposed lungs had the same appearance as the filtered-air controls,” Bernstein and his co-investigators reported. No obvious lung damage, in Bernstein’s view, translated to little or no cancer risk.
In a later experiment, one group of rats inhaled re-created Ready-Mix containing chrysotile. Another group inhaled amosite asbestos, part of the amphibole family. The rats exposed to chrysotile showed “no pathology in either the lung or the pleural cavity,” Holm testified in his deposition. Those that breathed amosite showed “both...