Mineralogical and exposure determinants of pulmonary fibrosis among Québec chrysotile miners and millers.
OBJECTIVE
Lung fibre content was determined for 86 former chrysotile miners and millers in two Québec mining regions: Thetford mines (TM) and the Asbestos region (AR).


METHODS
Fibres were assessed using transmission electron microscopy (TEM) and energy dispersive X-ray spectrometry (EDS). Asbestos body (AB) concentrations were assessed by microscopy of tissue digests. Corresponding histological lung tissue sections were quantitatively graded for the severity of interstitial fibrosis on a 12-point scale. Fibrosis score and its associations with (1) fibre concentrations and fibre dimensions within three fibre length intervals (less than 5 microm, 5-10 microm, and over 10 microm), and (2) several exposure variables were evaluated using correlation coefficients and regression techniques.


RESULTS
Concentration of short (<5 microm) tremolite fibres was the best predictor of fibrosis grade in both mining groups (r=0.44, P<0.01 and r=0.39, P<0.01 for TM and AR, respectively). Chrysotile fibre concentration showed a lower correlation with the fibrosis grade for subjects from TM only. Long (>10 microm) amosite fibre concentration showed a linear relationship with the fibrosis score in miners and millers from AR. Exposure variables, including smoking, had no predictive value for fibrosis grade. Within fibre length categories, fibre dimension was not related to the fibrosis score.


CONCLUSIONS
Lung fibre concentration as measured by TEM/EDS, especially that of short (<5 microm) tremolite fibres, is a better predictor of fibrosis grade in these two groups of chrysotile miners than either the concentration of ABs or the duration of exposure. Due to the limitation of our counting method, almost all fibres longer than 10 microm observed in this study were shorter than 14 microm. Thus, if length plays a role in fibrogenesis, it may be related to fibres of greater length than those covered in this study.
Nayebzadeh
Ataollah
A
McGill University Health Centre, Montréal General Hospital, 1650 Cedar Ave. Suite T6-204, Montréal, QC, Canada H3G 1A4. ataolah.nayebzadeh@mail.mcgill.ca
Case
Bruce W
BW
Massé
Janick
J
Dufresne
André
A
D017636:Asbestos, Amphibole / Q000009:adverse effects; D017632:Asbestos, Serpentine / Q000009:adverse effects*; D019652:Extraction and Processing Industry; D006801:Humans; D008168:Lung / Q000473:pathology; D046529:Microscopy, Electron, Transmission; D009784:Occupational Diseases / Q000139:chemically induced* / Q000473:pathology; D016273:Occupational Exposure / Q000009:adverse effects*; D011658:Pulmonary Fibrosis / Q000139:chemically induced* / Q000473:pathology; D011792:Quebec / Q000453:epidemiology; D013052:Spectrometry, X-Ray Emission
D017636:Asbestos, Amphibole; D017632:Asbestos, Serpentine; C005846:tremolite