Read until the end!
SILICOSIS IS IN THE NEWS. SO WHAT IS IT?
“What is silicosis?
Silicosis is a long-term lung disease caused by inhaling unsafe levels of silica dust, usually over a period of many years.
People who work with certain materials may inhale a very fine dust that contains silica. Once inside the lungs, the dust particles can scar the lungs. This scarring is known as silicosis.
Silicosis can lead to breathing problems, a serious lung condition called Progressive Massive Fibrosis (PMF), or lung cancer. There is no cure for silicosis and it can be fatal.” – Healthdirect, Australian Government.
A couple of key points there: DUST, and USUALLY OVER A PERIOD OF MANY YEARS. The article goes on to describe the 3 common types of silicosis, all of which involve the dust.
The disease has got into the news because of its prevalence amongst those who work with stone or concrete, in a way that generates dust, on a day-to-day basis; for instance stonemasons, working in the stone benchtop industry.
Other places where silica dust may occur include certain crystalline concrete additives. More on this shortly.
SO WHAT IS SILICA?
Silica, the molecule, has the full name Silicon Dioxide, SiO2. In nature, it is known as quartz, and comprises more than 10% by mass of the earth’s crust. (Wikipedia) It is the major constituent of sand.
Perhaps surprisingly, it also occurs in plants, particularly rice husks.
This makes it unfortunate that the construction industry in Australasia has flatly equated ‘silica’ with ‘harmful’. We’re surrounded by silica, and it only causes silicosis under specific circumstances – see ‘dust’ and ‘usually over a period of many years’, above. Particularly that bit about ‘dust’.
THERE ARE FORMS OF SILICA WHICH ARE NOT INHERENTLY HARMFUL.
Is sand harmful? Definitely don’t breathe it or get buried under it. Like water, sand can be lethal under some circumstances, but not usually because of its silica content.
Is rice harmful? The silica-rich husks are not regarded as edible by humans, but make good fodder for cattle and other domestic herbivores.
Is colloidal silica harmful? – wait, what’s colloidal silica?
A colloid consists of part-molecules suspended in water – for example, milk. Silica in colloidal form consists of reactive part-molecules suspended in water. Yes, it is completely safe for humans (as long as there’s not enough to drown in). It’s also safe for animals, plants, and sensitive environments.
SILICA AND CONCRETE ADMIXTURES
You’re still with us? Thank you! We’re finally getting to the point.
As noted earlier, ‘silica’ has come to be equated with ‘harmful’ in the construction industry. Now, we totally understand the concern. Where MARKHAM has come up against this issue is in the area of concrete admixtures.
Crystalline silica admixtures – dry powder – are in common use in the industry; and yes, frequent unprotected interaction with these products does pose the risk of silica dust inhalation.
Colloidal silica admixtures – water based liquid – simply do not pose any risk of this sort. There is no dust involved, and no risk of build-up in the lungs. LIQUID COLLOIDAL SILICA IS EXTREMELY SAFE TO USE.
BONUS! Applying the correct colloidal silica treatments to concrete will reduce the risk of concrete dust which usually results from ageing.
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