The ABC TV mini-series Devil’s Dust gave an enlightening but frightening history of asbestos-related disease and litigation in Australia, and it made me want to find out more about this wonder material turned bad. What exactly is asbestos, and how does it cause cancer?
Asbestos is a family of fibrous minerals. The most common type mined in Australia, primarily at Wittenoom WA, was blue asbestos, or crocidolite. Its chemical formula is Na2Fe2+3Fe3+2Si8O22(OH)2, which is actually that of an igneous mineral called riebeckite. Riebeckite forms elongated blue crystals, but it’s only considered asbestos when the crystals are fibres with a width of about 1 micrometre or less.
There are five other types of asbestos, mostly minerals with tiny rigid fibres like crocidolite. However, there’s one kind, known as white asbestos or chrysotile, mined primarily in Canada, which has longer, softer fibres.
All kinds of asbestos are resistant to fire, heat and chemical damage, and have been used in various forms for thousands of years. However, it’s probably the flexible white asbestos, chrysotile, which was woven into miraculous cloths that could be cleaned simply by throwing them into the fire. Wily traders tried to convince people these cloths came from the fur of the fireproof salamander, but Marco Polo himself debunked the idea, calling it “fabulous nonsense”.
In Australia, the less flexible blue asbestos was used for decades as a component in building material and insulation, thanks to its good tensile strength. But there have been other uses that seem absolutely crazy in hindsight, such as making filters for cigarettes and gas masks, or even artificial snow.
However, health problems due to over-exposure have been known for hundreds of years, with mentions of lung disease afflicting slaves who worked in asbestos mines. Quite possibly this was asbestosis, which is scarring of the lungs caused by an accumulation of inhaled fibres.
Even scarier though is mesothelioma, a cancer of the mesothelium, or protective lining around organs – primarily the pleura, which lines the lungs.
How asbestos causes cancer – or even how it gets out of the lungs and into the pleura – is not exactly known. There are theories that it causes inflammation, or oxidative stress due to the undigestibility of the fibres, or that it interferes with signalling mechanisms, or even that the fibres get physically tangled and interfere with chromosomes in the cell (Toyokuni S 2009, “Mechanisms of asbestos-induced carcinogenesis”, Nagoya Journal of Medical Science, vol. 7, no. 1, pp. 1-10).
This is because one notable property of asbestos fibres is that, even though they start at a scale of around 1 micrometre, they easily break up into into thinner fibres, getting down to 0.01 micrometres, or 10 nanometres. That’s smaller than the pores in cell nuclei.
Whatever the mechanism, it seems that it can only take one rogue asbestos fibre to give you cancer. So should you panic?
Well, although there are about 600 new cases of mesothelioma diagnosed in Australia every year (based on 2007 data), that doesn’t necessarily reflect the ubiquity of asbestos in the community. Some people contract mesothelioma after minimal exposure, such as washing clothes or being near a building site, but some workers in asbestos plants don’t get the disease. It’s possible that most of the fibres are removed by the human body before they’re able to do lasting damage.
That doesn’t mean you should be too complacent, as mesothelioma can take between 20 and 50 years to develop following exposure. But neither should you panic: when the dangers were first realised, there was a rush to remove asbestos from buildings, but this only led to more fibres being released into the air. So now the recommendation is that, if the asbestos is intact, it’s safer to leave it where it is.
But if you are doing renovations and need to remove it, it’s important to follow appropriate safety precautions, or hire a qualified contractor. You can find information about safe removal of asbestos at Asbestoswise, www.asbestoswise.com.au.
Asbestoswise also recommend not panicking if you accidentally disturb and break some asbestos. Their advice is to wipe up the dust with a damp cloth or paper towel, put the cloth or towel into a plastic bag, tie the plastic bag and put it into another plastic bag, tie up that one and put it in your rubbish bin. Seal any cracks in the panel, or if it’s too damaged, replace the whole thing.
So asbestos is very scary, but you don’t need to panic – just treat it with caution.
You can find out more about mesothelioma from the Cancer Council Victoria.
(This story aired on 29 November 2012 – you can listen to the podcast.)