Dimensional determinants for the carcinogenic potency of elongate amphibole particles

Abstract

Context

Carcinogenic properties of particulates depend, among other factors, on dimensional characteristics that affect their ability to reach sensitive tissue, to be removed or retained, and to interact with the cells.

Objective

To model mesothelioma and lung cancer potency of amphibole particles based on their dimensional characteristics and mineral habit (asbestiform vs. nonasbestiform) utilizing epidemiological data and detailed size information.

Methods

The datasets from recently created depository of dimensional information of elongate mineral particles were used to correlate mesothelioma and lung cancer potency with the fraction of particles in a specific size range and the ratio of length and width in different powers. In addition, the cancer potency factors were estimated and compared for 30 asbestiform, 15 nonasbestiform, and 10 mixed datasets.

Results

For particles longer than 5 µm, the highest correlation with mesothelioma potency was achieved for width <0.22 µm, and with lung cancer <0.28 µm. The statistical power of the correlation was observed to lose significance at a maximum width of 0.6–0.7 µm. Mesothelioma potency correlated with length in the power of 1.9 divided by width in the power of 2.97, lung cancer potency with length in the power of 0.4 divided by width in the power of 1.17. The predicted cancer potencies of asbestiform, nonasbestiform, and mixed categories were significantly different.

Conclusion

While additional studies in this direction are warranted, this paper should serve as an additional confirmation for the role of fiber dimensions in the carcinogenicity of amphibole elongate mineral particles (EMPs).

Keywords:

• Elongate mineral particles
• asbestiform
• mesothelioma
• lung cancer
• length
• width

Acknowledgments

The authors thank those who made their data sets available to them and especially the National Stone, Sand and Gravel Association for its commitment to worker protection and for enabling the development of the database used in this study.

Disclosure statement

The database utilized in this study was created in the frame of the project “Fibrous minerals database development and statistical analysis of various characteristics relevant for the prediction of toxicity” sponsored by National Stone, Sand and Gravel Association (NSSGA). Professor Ann Wylie has been involved in asbestos litigations as an expert.

RTI: Research Triangle Institute; UMD: University of Maryland; USBM: United States Bureau of Mines; BVNA: Bureau Veritas North America; EPA: US Environmental Protection Agency; OSHA: United States Occupational Safety and Health Administration; MSHA: United States Mining Safety and Health Administration; NIST: National Institute of Standards and Technology; NIEHS: National Institute of Environmental Health Sciences; MRI: Midwest Research Institute; TEM: Transmission Electron Microscopy; SEM: Scanning Electron Microscopy.

Notes

1 The same cannot be assumed about fibers of chrysotile because of its much lower index of refraction and diminished contrast with immersion media in the PCM method used for occupational monitoring.

2 Comparing relative potency for individual particles based on their dimensions does not mean that we assume that one particle can produce the cancer; specific (and usually very substantial) exposure levels would be needed to increase risk of cancer in certain populations. However, exposure to particles of various dimensions will vary in quantitative potency.