How Silver Membrane Helps in Cutting the Risks of Silica Dust

^{Photo courtesy of EHS Safety News America.}

Inhalation of respirable crystalline silica (RCS) dust causes debilitating and often fatal lung diseases. Silicosis, its primary manifestation, leads to scarring and hardening of the lungs, which makes it difficult for the affected person to breathe. Exposure occurs when rock-based materials are cut, crushed, or blasted, forming fine particles of RCS. These are typically encountered in the construction, mining, and abrasive blasting industries, to name a few. Consequently, workers from these industries are at high risk from the dangers of inhaling RCS.

Through extensive research, the Occupational Safety and Health Administration (OSHA) published the new RCS Standard under 29 CFR 1910.1053 in 2016. This version sets a lower RCS permissible exposure limit (PEL) of 50 µg/m³, from a previous formula derived PEL of 100 µg/m^3.[1] The lower PEL, along with suitable practices and controls, should help reduce the risks from inhaling RCS dust.^[1][2][3]

Periodical measurement of RCS is at the core of the current regulation to assess compliance with the prescribed PEL. RCS in the workplace should be sampled and analyzed through either NMAM 7500, OSHA ID 142, or MSHA P-2.^[4] X-Ray Diffraction (XRD) is the analytical technique used for these standard methods as it provides high specificity to most forms of crystalline silica.^[5] Before subjecting to XRD, samples are required to be treated and redeposited onto pure silver membrane filters. This is necessary to generate an XRD spectrum with low background noise and distinct diffraction peaks.

Since the update by OSHA, only a few EU countries, some Canadian provinces, and Mexico have published tighter RCS exposure limits.^[6] Australia should soon follow as they are working to lower RCS exposure limits to 20 µg/m³, which came after a local state audit revealing numerous cases of silicosis.^[7][8] Just recently, OSHA intends to further enhance the new RCS Standard by adding safety controls and practices required for the construction industry and extending the scope of compliance for the general and maritime industry.^[9] For details, you can check this OSHA Trade Release. 

On a global scale, most countries do not have similar stringent exposure limits, while some developing countries lack the regulatory limits for RCS.^[6] Given the health concerns highlighted by the OSHA study, it is anticipated that the adoption of more stringent occupational exposure limits and workplace monitoring of RCS dust will become more widespread.