Exceedance of environmental exposure limits to crystalline silica in communities surrounding gold mine tailings storage facilities in South Africa

Charlene Andraos; Wells Utembe; Mary Gulumian

doi:10.1016/j.scitotenv.2017.11.135

Exceedance of environmental exposure limits to crystalline silica in communities surrounding gold mine tailings storage facilities in South Africa

Sci Total Environ. 2018 Apr 1:619-620:504-516. doi: 10.1016/j.scitotenv.2017.11.135. Epub 2017 Nov 29.

Authors

Charlene Andraos¹, Wells Utembe², Mary Gulumian³

Affiliations

¹ Toxicology Department, National Institute for Occupational Health, PO Box 4788, Johannesburg 2000, South Africa; Haematology and Molecular Medicine Department, University of the Witwatersrand, Private Bag 3, Wits, 2050 Johannesburg, South Africa. Electronic address: charlene.andraos@nioh.nhls.ac.za.
² Toxicology Department, National Institute for Occupational Health, PO Box 4788, Johannesburg 2000, South Africa. Electronic address: wells.utembe@nhls.ac.za.
³ Toxicology Department, National Institute for Occupational Health, PO Box 4788, Johannesburg 2000, South Africa; Haematology and Molecular Medicine Department, University of the Witwatersrand, Private Bag 3, Wits, 2050 Johannesburg, South Africa. Electronic address: mary.gulumian@nioh.nhls.ac.za.

PMID: 29156270
DOI: 10.1016/j.scitotenv.2017.11.135

Abstract

Background: Unlike occupational silica exposures, the association between non-occupational silica exposures and adverse health effects is not well researched, despite its occurrence in communities close to dust-generating sources such as tailings storage facilities (TSFs). Recent studies have shown that communities surrounding TSFs in South Africa often complain about the onset of dust-related health effects. Even though international interim non-occupational crystalline silica limits have been established, South Africa is yet to enforce its own limits for residential areas close to TSF sites.

Objective: The objective of the study was to assess the need to enforce non-occupational crystalline silica limits for South Africa.

Methods: The methods involved (1) Quantifying the silica polymorph content in bulk dust collected from TSFs in South Africa; (2) Assessing the possibility of the dust to reach surrounding communities through ambient and personal filter sampling and; (3) Conducting risk characterisation for both cancer and non-cancer endpoints.

Results: All bulk dust samples consisted mostly of crystalline silica (73.14-87.09%). Large percentages of nanoparticles were identified in all bulk samples (66.8-70.7%) indicating the possibility of the dust to lodge deep within the lungs. The crystalline silica levels obtained from ambient PM₁₀ sampling and personal PM₄ sampling all exceeded the international crystalline silica interim limits and reached maximum levels of 90 and 50.9μg·m^-3, respectively. For three TSFs, sampling sites close to the TSFs showed higher PM₄ silica levels compared to sites further from TSFs. Risk characterisation revealed the possibility of cancer and non-cancer health effects when chronically exposed to silica levels recorded during the study.

Conclusion: The results indicate unacceptable crystalline silica exposures in surrounding communities and the need for enforcement of an ambient silica limit for South Africa.

Keywords: Air pollution; Crystalline silica polymorphs; Exposure limits; Health risk assessment; Mine tailings.

MeSH terms

Air Pollutants / analysis*
Dust
Environmental Exposure / adverse effects*
Gold
Humans
Mining*
Residence Characteristics
Silicon Dioxide / analysis*
South Africa

Substances

Air Pollutants
Dust
Gold
Silicon Dioxide