Toxicological and epidemiological approaches to carcinogenic potency modeling for mixed mineral fiber exposure: the case of fibrous balangeroite and chrysotile

Abstract

Context

Excess mesothelioma risk was observed among chrysotile miners and millers in Balangero, Italy. The mineral balangeroite has been identified in an asbestiform habit from the Balangero chrysotile mine (Italy). Previous studies did not contain a detailed description of the fiber dimensions, thus limiting possible approaches to estimating their carcinogenic potential.

Objectives

To reconstruct excess mesothelioma risk based on characteristics of mixed fiber exposure.

Methods

The lengths and widths of particles from a sample of balangeroite were measured by transmission electron microscopy (TEM). Statistical analysis and modeling were applied to assess the toxicological potential of balangeroite.

Results

Balangeroite fibers are characterized as asbestiform, with geometric mean length of 10 μm, width of 0.54 μm, aspect ratio of 19, and specific surface area of 13.8 (1/μm). Proximity analysis shows dimensional characteristics of balangeroite close to asbestiform anthophyllite. Modeling estimates the average potency of balangeroite as 0.04% (95% CI 0.0058, 0.16) based on dimensional characteristics and 0.05% (95% CI–0.04, 0.24) based on epidemiological data. The available estimate of the fraction of balangeroite in the Balangero mine is very approximate. There were no data for airborne balangeroite fibers from the Balangero mine and no lung burden data are available. All estimates were performed using weight fractions of balangeroite and chrysotile. However, based on reasonable assumptions, of the seven cases of mesothelioma in the cohort, about three cases (43%) can be attributed to fibrous balangeroite.

Conclusion

The presence of different types of mineral fibers in aerosolized materials even in small proportions can explain observed cancer risks.

Keywords:

• Balangeroite mineral group
• balangero
• elongate mineral particles
• asbestiform
• mesothelioma
• lung cancer
• chrysotile

Acknowledgements

The authors are grateful to Dr. Francesco Turci who provided the balangeroite sample for the study. The study also utilized the dimensional database for elongate mineral particles created with a support from National Stone, Sand, and Gravel Association (NSSGA).

Disclosure statement

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. However, National Stone, Sand, and Gravel Association (NSSGA) supported Dr. Andrey Korchevskiy in some of his studies on carcinogenic potency of mineral fibers.

Data availability statement

The data that support the findings of this study are available from the corresponding author, Andrey Korchevskiy, upon reasonable request.

Additional information

Funding

The study also utilized the dimensional database for elongate mineral particles created with a support from National Stone, Sand, and Gravel Association (NSSGA).