Silver Membranes in Monitoring Respirable Crystalline Silica

Crystalline silica, most commonly found in the form of quartz, is a basic component of the earth; it’s found in soil, sand granite, and other minerals. During many industrial processes, crystalline silica is released as particles that are 100 times smaller than beach sand.1 Due to their size, these mineral particles cannot easily be cleared by human lungs. Instead, they persist in the respiratory system and form scar tissue, contributing to serious health problems for those experiencing prolonged exposure. The associated silicosis and other forms of cancer are a threat to workers in mining, construction, and other industrial trades.2

There is a global awareness of this seriousness of this issue, and the World Health Organization has published assessment documents detailing the negative health effects of exposure. Here in the US, the Occupational Safety and Health Administration (OSHA)  released a Final Rule on Occupational Exposure to Respirable Crystalline Silica, to provide guidance for the safety of industrial workers.3 The ruling published in March 2016 puts the responsibility on companies to create a low-risk environment, with enforcement in the form of fines (potentially over $12,000 per day) going into effect for some industries starting in September 2017.3 Beyond recommending proper personal protective equipment, ventilation systems, and replacement of silica when safer materials can be used, this ruling establishes a permissible exposure limit (PEL) at 50 μg/m3. This means that only 1/5th of the previously allowed PEL is now considered safe in the workplace.2

To monitor levels of crystalline silica, employers can take routine samples and have them analyzed in a lab. A portable sampler is used to collect air from the worker’s respirable area during a full shift. The dust captured on the filter is then analyzed using a standard method, such as NIOSH 7500.4 In this method, the filter is then dissolved and redeposited on a 0.45 micron silver membrane for measurement using x-ray diffraction. Silver membranes have become the standard for x-ray diffraction analysis due to their high sample-load capacity and characteristically low background noise during analysis.

The results of these analyses help employers understand whether they need to be taking more action to protect their workers. OSHA estimates that the steps advised in their ruling will save 600 lives and prevent 900 cases of silicosis every year.5 For now, companies in regulated industries are developing control plans and training workers to ensure compliance with the new rules. It remains to be seen what the full impact of enforcement will mean for their employees and their business.

[1] Dangers of Crystalline Silica | Taylor Made Diagnostics. Taylormadediagnosticscom. 2018.
[2] Spafford A. OSHA Silica Dust Permissible Exposure Limit 2016 Update. Pro Tool Reviews. 2018.
[3] Occupational Exposure to Respirable Crystalline Silica. Federal Register. 2018.
[4] Safety and Health Topics. Respirable Crystalline Silica - Sampling and Analysis. Occupational Safety and Health Administration. Oshagov. 2018.
[5] Everything You Need to Know About OSHA's Respirable Crystalline Silica Final Rule. Occupational Health & Safety. Occupational Health & Safety. 2018.