Recognizing and Controlling the Asbestos Hazard of Vermiculite
Insulation in Construction
Vermiculite insulation was commonly
installed as wall and ceiling insulation in a number of commercial and
residential applications. This material is now known to contain a
significant asbestos contamination. Contractors must ensure that any
disturbance of vermiculite insulation is performed with appropriate
precautions to protect their workers, comply with Ministry of Labour
requirements, and avoid liability from the project owner.
Vermiculite
is a mineral mined around the world and used in a variety of commercial
and consumer applications. After crushing and heating to about 1,000
oC, it expands like popcorn to produce fluffy particles. The
exfoliated material is fire-resistant, absorbent, light weight and a
good insulator. Vermiculite had a number of important applications in
construction. It was commonly added as a light weight component in
concrete and plaster mixtures and in sprayed fireproofing. Due to the
binder systems present in these materials, they are unlikely to release
significant asbestos during common disturbances. However, vermiculite
was also frequently used until the early 1990s as loose fill insulation
inside masonry block walls, stove pipe and stack insulation, fire
separations, cold rooms and in walls and attics of buildings, including
homes. These loose fill applications do pose a substantial risk of
asbestos exposure to construction workers and require careful control.
Many vermiculite mines contained varying
amounts of asbestos minerals mixed in the vermiculite deposit. Of
particular importance to Canada was the Libby Montana mine owned by W.R.
Grace, reported by the US Environmental Protection Agency as the source
of as much as 70% of the world’s consumption (and likely 90% of the
North American use) until it closed in 1990. The Libby deposit was
contaminated with an asbestos mineral usually identified as tremolite.
Although W.R. Grace took increasing measures through the history of the
operation to reduce the asbestos content in their products, it is likely
that most of their production contained at least a trace of free
asbestos fibre. Exposure to asbestos for prolonged periods or at high
concentrations increases the risk of lung cancer and other respiratory
diseases and many of the Libby workers and residents have become sick or
died of asbestos disease originating from the mine and milling
operations.
Vermiculite insulation can be readily
identified as a light weight, silvery grey granular material, with
granule sizes of about 2 to 10 millimeters. The visual identification
can be confirmed by testing by a laboratory who should be contacted for
advice on testing and interpretation of results. The laboratory should
be accredited by one of the two US agencies that qualifies laboratories
for the analysis of asbestos in bulk samples.
Obviously a contractor has to protect his
workers and building occupants from any risk of asbestos exposure. If
undisturbed on a project, the material poses no risk. However, even
relatively minor disturbance may generate excessive levels of airborne
asbestos. Although the asbestos concentration in the installed
insulation is relatively low, ranging typically from a trace to up to
5%, it still poses a very serious risk to health if disturbed. Pinchin
Environmental has performed hazard assessments of typical disturbances
of loose fill insulation for the Department of National Defence and is
aware of similar assessments performed in the US. These show that under
conditions that would be common on construction sites (removal of an
insulated ceiling during renovation or demolition, manual removal of
loose fill insulation) airborne asbestos levels may be up to 1700 times
the maximum acceptable exposure level. The owner of the project is
required by the Occupational Health and Safety Act to provide a survey
of all asbestos materials prior to a project. However, contractors
should be aware that the risk of asbestos-contaminated vermiculite has
only recently been identified so that many building owners or their
agent, and especially homeowners, may not be aware of the hazard. In
addition, the vermiculite might only be identified when a wall cavity or
insulated chase is opened. In any event, when loose fill vermiculite is
identified, the contractor must put into place appropriate controls.
Because any disturbance of vermiculite will likely generate exposures in
excess of the provincial limit, all such disturbance should be performed
with Type 2 or Type 3 controls as required by the Ministry of Labour
asbestos in construction regulation. On most projects, this will
generally require a qualified asbestos abatement contractor to carefully
remove the vermiculite before the project can proceed.
Home renovation contractors may be the most
affected by the vermiculite issue. The US EPA has estimated that up to
several million US homes may have asbestos-contaminated vermiculite
attic or wall insulation. Although there are no available Canadian
estimates, we would expect the Canadian number to be upwards to several
hundred thousand homes. Home renovators should carefully inspect their
projects for vermiculite to prevent the serious liability that would
result from asbestos contamination from an uncontrolled disturbance.
For more information on asbestos in
vermiculite building insulation, visit the EPA website at
www.epa.gov/asbestos/insulation.html or the Pinchin Environmental
website,
www.pinchin.com.
Suggested byline:
Bruce Stewart CIH, ROH,
is a Principal with Pinchin Environmental, a Mississauga-based
consulting firm offering environmental and laboratory services across
Canada, and a member of the TCA Environmental Committee. |