Nov. 25, 2017
Respirable Crystalline Silica (RCS): the new “asbestos”?
By Ihor Barwinsky, Safety Manager, Gypsum Drywall Interiors Ltd.
Crystalline Silica is not a new material in the construction industry. In fact, it’s one of the most common substances on this planet. It also goes by another name: dust. But this is different from the household variety. Respirable Silica dust is the airborne matter that is generated by cutting or grinding concrete, demolition of buildings and structure and of great interest to us, drywall dust from sanding our finished product. It is similar in size and jagged spiky structure to asbestos and this is where the problem lies.
The bad news about crystalline silica has been around for over forty years, and now people are connecting the dots.
Exposure leads to silicosis, and decreased pulmonary function. From CAREX:
Silicosis, a non-reversible fibrotic lung disease, is caused by inhaling crystalline silica particles. Silicosis is typically categorized as chronic (> 10 years exposure), accelerated (high concentrations over 5-10 years), or acute (short term exposure at high concentrations). Besides silicosis and lung cancer, occupational silica exposure has also been linked to pulmonary tuberculosis, chronic obstructive pulmonary disease, and rheumatoid arthritis.[8,9]
International Agency for Research on Cancer, IARC, (part of the WHO) cites RCS as a cancer causing agent, also a correlation with stomach cancers. If you get lung cancer, there is a high probability you will not survive. Smoking and exposure have synergistic effects, meaning that they work together and amplify each other’s effects.
So, if you smoke and are a taper, it might be time to think about it.
Under Duties of the Employer: review what we do, with worker input, and if needed, develop practical controls to reduce the level of exposure.
Under Duties of the Employee: work with the employer in making these controls work.
We can’t just say: “wear a mask:
As with all hazards, PPE is the last line of defense and we must do everything we can to get levels down so we don’t need PPE. Will that level actually hit the bottom? Chances are not, but there have been many sites where the dust has been quite low. We need to at least show that we have tried this and have strategies in place. Read the paragraph below from the Manitoba Workplace Safety and Health Regulations (the little book that is with all of our workers):
Personal protective equipment
When an employer is required to implement control measures under this Part to control a worker’s exposure to an airborne chemical or biological substance, the control measures must not include a requirement for a worker to wear or use personal protective equipment to prevent or reduce exposure to a chemical or biological substance unless no other measure is reasonably practicable.
Any personal protective equipment required under subsection (1), including respiratory protective equipment, must meet the requirements of Part 6 (Personal Protective Equipment).
Establishing exposure level at sites/ Monitoring levels: we already know that it will be above threshold limits
Currently, SAFE Work Manitoba is looking for sites to test for base lines,
WSH will come knocking on our doors eventually.
Warn of the hazard: Post signs that silica is present the same way the painters and spray foamers hang signs: alert of the exposure.
Clean and careful taping techniques will reduce the amount that you have to sand. Vacuum sanders also work well to get a lot of it away from the worker. It has been shown, anecdotally and just by observation in some of the work we have done, that we can reduce levels of RCS floating through the air.
How do we reduce the dust?
While sanding: ventilation to outside to disperse the dust, but some thought has to be given to what’s downwind,
Capture it: vacuum sanders, but they must be HEPA, and maintained,
Vacuum what has fallen, again a HEPA vac,
Sweeping compound at scrap out, even then you should be wearing a respirator,
Dust collector filtration: recirculating air with filters (some primes have used these to control dust, and not just dust made by us).
Now, to the PPE:
Currently we are using a N95 disposable. This may not be enough protection once things get tested out, and we will need to do fit testing. Workers’ clothing should not be worn home, leading to exposure of the household (think of the dusty truck).
Move to half mask with P100 filter (HEPA)
Costs the same or a bit less than the disposable N95
A proper fit test means no beard-skin to mask fit
What if the respirator does not fit?
Adjust, better shave, different model or size
This is going to change the way we do things:
Change to work habits always has a cost, and not just in dollars. It takes a bit of work and thinking to adopt new habits and it takes energy to learn how to use new tools, or old tools differently.
This is a change for the better: ensuring the long term health of workers.
Canadian Centre For Occupational Health and Safety: https://www.ccohs.ca/oshanswers/diseases/silicosis
Wikimedia. Wikimedia Commons Photo: A-quartz
International Agency for Research on Cancer (IARC). Monograph summary, Volume 68 (1997) (PDF)
Key-Schwartz, R., et al. and The National Institute for Occupational Safety and Health (NOISH). NIOSH Manual of Analytical Methods: Determination of Airborne Crystalline Silica (2003)
National Toxicology Program (NTP). 14th Report on Carcinogens for Silica, Crystalline (2016) (PDF)
Occupational Safety and Health Administration (OSHA). Fact Sheet: Crystalline Silica Exposure Health Hazard Information (2002) (PDF)
International Agency for Research on Cancer (IARC). Monograph summary, Volume 100 Part C (2009) (PDF)
International Programme on Chemical Safety (IPCS) INCHEM. CICAD Document No. 24: Crystalline Silica, Quartz (2000) (PDF)
G M Calvert, F L Rice, J M Boiano, J W Sheehy, W T Sanderson. "Occupational silica exposure and risk of various diseases: an analysis using death certificates from 27 states of the United States." Occupational & Environmental Medicine 2003;60:122-129.
Parks, C. et al. "Occupational Exposure to Crystalline Silica and Autoimmune Disease." Environmental Health Perspectives 1999;105(7)793-802.
Health Canada. Prioritization of the DSL (2006)
Government of Canada. Challenge to Industry List of Substances (2016)
Environment and Climate Change Canada. CEPA List of Toxic Substances (1999)
Natural Resources Canada. Canadian Minerals Yearbooks: Silica/Quartz (2006)
Mining Association of Canada. Facts & Figures of the Canadian Mining Industry (2014) (PDF)
International Trade Centre. TradeMap (Free subscription required)
Bhagia LJ. "Non-occupational exposure to silica dust." Indian J Occup Environ Med. 2012;16(3):95-100.
US Department of the Interior. Special publication: Crystalline silica primer. Washington, DC, US Department of the Interior, Bureau of Mines. (1992)
Maciejewska, A. "Occupational Exposure Assessment for Crystalline Silica Dust: Approach in Poland and Worldwide." International Journal of Occupational Medicine and Environmental Health 2008;21(1)1-23.