Comments on "Dimensions of elongated mineral particles with implications for pathogenicity and classification as asbestiform versus cleavage fragments".

Roggli and Green have reported their study of the dimensions of fibers extracted from the tissues of cases examined in their laboratory, and have drawn conclusions about the pathogenicity of Elongated Mineral Particles and their classification as asbestiform versus cleavage fragments. There are aspects of their methodology and discussion that would benefit from examination. Roggli and Green have relied upon a paper by Harper et al. for their definitions of asbestiform and cleavage fragments. Unfortunately, they have misinterpreted the work of those authors who have concluded that the best criterion is a particle width <1µm. Roggli and Green conclude that 'Our findings demonstrate the lack of pathogenicity of fibers less than 10 µm long or likelihood of cleavage fragments for fibers less than 10µm long and greater than 1.0µm in diameter has little or no effect on the classification of commercial amphibole fibers using our analytical methodology. On the other hand, both lack of pathogenicity and likelihood of cleavage fragments apply to a significant proportion of noncommercial amphiboles identified using our counting scheme.' This is not true. The study of Roggli and Green was a simple fiber counting study with no control population. The design of such a study does not allow the investigator to draw any conclusions about pathogenicity, or lack thereof.

A comparison of asbestos fiber potency and elongate mineral particle (EMP) potency for mesothelioma in humans.

Dr. Garabrant presented a paper concerning a comparison of asbestos fiber potency and elongate mineral particle (EMP) potency for mesothelioma in humans at the Elongate Mineral Particles Conference in Charlottesville, Virginia in 2017. I was a participant at the Conference. Following Dr. Garabrant's talk, I rose in question period to point out that he had not considered information about the occurrence of mesothelioma in several cohorts that was published after the studies that he cited. These additional data were still not addressed in the paper published in your Journal. I believe that your readers would be interested in these, so this letter is written to draw the additional data to their attention.