Posted by: Brian de Alwis | March 18, 2010

The Perils of Houses: Vermiculite and Asbestos

After years of renting, we are finally looking to buy a house. One of our requirements is that the house be within an easy walk of the downtown area and the downtown grocery store, which means that we’re looking at older homes, predominantly built in the early 1900s. Although we’ve been repeatedly cautioned that older homes have issues, we just barely avoided an issue of which we had never been aware.

We recently found an old house that had been beautifully redone by its current owners. It was about 5 minutes further than we wanted, but the house looked to be in excellent shape, was in a very desirable location, and the street was handsome. The owners did mention that the house was insulated with vermiculite, but they had had it tested and the reports found no signs of asbestos. As we had been warned about UFFI (whose risks seem to have been over-blown), but had never heard anything against vermiculite, we thought nothing of it. We made an offer, and after some haggling, came to an agreement. Fortunately we had some warning signs, some inadvertent slips on the part of the owners about the electrical work that had not been disclosed, that put us on our guard.

We’re fortunate to have required an inspection (we may be first-time home-buyers, but we’re not stupid!). Our inspector pointed out a number of issues, including the use of vermiculite, and two locations where vermiculite had leaked. Even more fortunate is that the owners made another slip, revealing that the owners prior had had a positive test to asbestos in the vermiculite.  I glossed over this as my concerns were centred on the new electrical work in the house, which proved to be somewhat dodgy. But our inspector is a bit reserved, and it was only when I pressed him that he listed the vermiculite as being his major concern. I was astonished: I expected that he’d be much more concerned about the mis-grounded wiring or some of the not-up-to-code renovations.

At home, I began scouring the ‘net for vermiculite. It seems that vermiculite is an excellent insulator, and as a bonus is fire-proof. Although vermiculite is found throughout the world, unfortunately the primary source of most of vermiculite used in North America (and perhaps the world) from the 1920s until 1990 came from a particular mine in Libby, Montana, which has been shown to have been contaminated with asbestos. Apparently asbestos and vermiculite develop in similar conditions. More importantly, the asbestos minerals tend to separate and, if disturbed (e.g., from rewiring), can become airborne. Although the contamination issue was known to the mine’s owners and management, this knowledge was suppressed, and this asbestos-contaminated vermiculite has been widely installed under a surprisingly wide variety of brand names.

Not all vermiculite contains asbestos. Since 1990, vermiculite mines now undertake regular testing for the presence of asbestos. Unfortunately because the link between was not known, Zonolite could have been installed along with safe vermiculite. This means that a house with negative tests could still have Zonolite installed in an unsampled area. And as noted in WorkSafe BC’s Safe Work Practices for Handling Asbestos (p5):

Some materials (such as vermiculite) may contain less than 1% asbestos, by weight or volume, and still pose a risk to workers if improperly handled.

Both Health Canada and the US EPA recommend that, if your house has vermiculite, you should assume your house may contain asbestos.

So how bad is asbestos-bearing vermiculite?

Apart from the asbestos industry-funded research, the advice is unequivocal: there is no safe level of exposure to asbestos.

  • World Health Organization: “Asbestos is a proven human carcinogen (IARC Group 1). No safe level can be proposed for asbestos because a threshold is not known to exist.
  • US Environmental Protection Agency: “There is no known safe level of asbestos exposure.
  • US Surgeon-General: “ Most individuals exposed to asbestos, whether in a home, in the workplace, or out-of-doors will not develop disease — but there is no level of asbestos exposure that is known to be safe and minimizing your exposure will minimize your risk of developing asbestos-related disease.
  • UK Health & Safety Executive: “Mesothelioma: There is a lack of scientific consensus as to whether there exists a threshold of exposure to asbestos below which a person is at zero risk of developing mesothelioma. […] For practical purposes HSE does not assume that such a threshold exists. Asbestosis and lung cancer: The situation for lung cancer and asbestosis is uncertain. […] This also suggests that if a threshold for lung cancer does exist for blue and brown asbestos it must be at a very low level indeed.

Sadly Canada is a major exporter of asbestos, and our asbestos industry is sufficiently influential that our government actively spreads misinformation about the effects of asbestos.  This despite the fact that Quebec government is actively ridding itself of all asbestos (the active mines are all in Quebec). But fortunately that should change in the near-term: although the Conservative Party still insists on wrapping the asbestos industry in the flag, the Liberal and NDP parties have finally seen the light (Toronto Star, Oct 5, 2009: “Quebec’s asbestos consensus crumbles; credit:

What should I do?

Health Canada’s advisory has a list of useful tips for minimizing your risk if you have a vermiculite-insulated house. In addition to the obvious (do not disturb or expose yourself to the vermiculite), it also includes:

  • If you plan to remodel or renovate—for instance, by re-insulating your attic—in a manner that would disturb the vermiculite, speak to professionals who are trained and qualified to handle asbestos removal before proceeding with the work to be done.
  • Seal all cracks and holes in the ceilings of the rooms below the insulation (for example, apply caulking around light fixtures and the attic hatch) to prevent insulation sifting through.

If you’re trying to sell a home with vermiculite, you should test multiple samples from throughout the house.  More important, you should have the laboratory come collect the samples.  Having the lab collect the samples not only alleviates any possible concerns about the chain of custody, it also ensures that the samples are taken from the correct location. Our vendors collected the samples themselves from the wrong locations, and as a result their reports were inconclusive (at least they were to us!). Knowing a house has vermiculite will be a major turn-off for many home-buyers (it certainly is for us), and is certain to reduce the potential purchase price; you might be better off paying for its removal and hope to recoup the money in the sale.

For us, after discovering the risks of vermiculite, we walked away from the sale. It hurt: we had already started picturing ourselves in the home, arranging our furniture, and allocating the rooms. But we’re definitely better off having regrets now rather than in ten years!





I’m a bit puzzled by this good news bulletin (“The Good News from EPA”, The Schundler Company) from a vermiculite manufacturer. This good news is based on a US EPA test of several sources of vermiculite showing no asbestos despite the fact that two of the samples were from the Libby mine and should have tested positive for asbestos. Maybe I’m missing something, but that doesn’t seem to be good news.  It may instead be the reason for the US EPA’s caution against testing: “[…] depending on the methods used, [testing] might give you erroneous results.” (“How can I tell if my vermiculite insulation contains asbestos?”)


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s