From Quartz Hazard to Quartz Risk: the Coal Mines Revisited

Abstract

Following the classification of quartz as a human carcinogen by the IARC, many standard-setting committees are currently trying to convert this hazard into their national or EU standards. Since human data to set a safe exposure limit for quartz are limited, we hypothesized that lung burden data on quartz in coal miners' lungs after lifetime exposure could be used to set a non-carcinogenic lung burden of quartz, and that this might be valid for other groups occupationally exposed to quartz. A review of data shows that lungs of coal miners with simple coal workers' pneumoconiosis (sCWP) typically contain up to 30 g of dust, and in one specific study lung burdens between 0.7 and 1.7 g of quartz were associated with macules only, and no sCWP. Assuming independent actions of coal and quartz and no clearance of quartz, and sCWP as a prerequisite for lung cancer due to quartz exposure in coal mine dust, a simple kinetic approach was applied. A no observed adverse effect level (NOAEL) for quartz of between 0.03 and 0.13 mg/m3 (40 yr exposure) is derived, but it is concluded that more refined physiologically based pharmacokinetic modelling is needed for a better estimate, also including interindividual differences in lung clearance. Considering the independent effects of, and the well-known interaction between coal and quartz, these data could be important to other workplaces with usual mixed-dust exposure.

Inflammation and fibrosis in the coal dust-exposed lung described by confocal Raman spectroscopy

“…For example, the collagen fibers of the tissue increased significantly over time, indicating that the lung tissue fibrosis caused by the coal dust progressed slowly, in contrast to that caused by silica, asbestos, and bleomycin ( Cao et al, 2021 ; Watanabe et al, 2021 ). We take 16 mg coal dust to a mouse in a month, which is approximately a miner 10 to 20 years exposure ( Henneberger & Attfield, 1997 ; Borm & Tran, 2002 ). These suggested that the mouse model was constructed in accordance with the development of CWP.…”

An Intratracheal Instillation Bioassay System for Detection of Lung Toxicity Due to Fine Particles in F344 Rats

“…Borm et al. reported a no observed adverse effect level (NOAEL) for quartz of between 0.03 and 0.13 mg/m 3 (40 year exposure) 7 based on an autopsy study for humans showing that lung burdens between 0.7 and 1.7 g of quartz are associated with macules only and not simple coal worker’s pneumoconiosis 8 .…”