Carcinogenetic effects of processing non-asbestiform tremolite asbestos mineral

Objectives The cancer risk of elongated mineral particles (EMPs) generated from non-asbestiform asbestos minerals is unclear. Nephrite is regarded as a non-asbestiform asbestos mineral. The objective of this study was to determine the cancer risk of nephrite.
Methods We examined cancer mortality between 1979 and 2011 in Fengtian, where nephrite was mass-produced from 1970 to 1980 and calculated standardised mortality ratios (SMRs). Results: We observed a significantly elevated mortality risk of cancer of the hypopharynx (SMR 2.31; 95% CI: 1.37, 3.65), larynx (SMR 2.51; 95% CI: 1.55, 3.83), oesophagus (SMR 2.04; 95% CI: 1.62, 2.54), and stomach (SMR 1.38; 95% CI: 1.17, 1.63). This study analysed the lengths, widths, structures, chemical compositions, aerodynamic diameters, and distributions of EMPs in airways. The majority of the EMPs (68%) were short (< 5 μm) and thin (< 0.5 µm) and had asbestiform structures. The median aerodynamic diameter of the EMPs was 1.2 μm. The total deposition proportion in airways was 51.3%. The major deposition sites were the head airway (37.5%), followed by the alveolar region (10.6%) and the tracheobronchial region (3.2%).
Conclusion This study provides evidence that short EMPs generated from processing nephrite are carcinogenic, and the fraction deposition of EMPs is associated with the mortality risk of cancer.