The implosion of the Calgary General Hospital: ambient air quality issues

Our plain-English summary of The implosion of the Calgary General Hospital: ambient air quality issues, by D. Stefani, D. Wardman, T. Lambert (Journal of the Air & Waste Management Association, 2005).

The study

• Authors: D. Stefani, D. Wardman, T. Lambert
• Journal: Journal of the Air & Waste Management Association
• Published: 2005;55(1):52-9
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This paper discusses the implosion of a large inner-city hospital in Calgary, Alberta, Canada, on October 4, 1998. Stationary and mobile air monitoring conducted after the implosion indicated there were several short-term air quality issues, including significant temporal increases in total suspended particles, particulate matter (PM) with aerodynamic diameter less than or equal to 10 microm (PM10), PM with aerodynamic diameter less than or equal to 2.5 microm (PM2.5), asbestos, and airborne and settled lead. In addition, the implosion created a dust cloud that traveled much further than expected, out to 20 km. The ability of an implosion to effectively aerosolize building materials requires the removal of all friable and nonfriable forms of asbestos and all Pb-containing painted surfaces during pre-implosion preparatory work. Public advisories to mitigate personal exposure and indoor migration of the implosion dust cloud constituents should extend to 10 or 20 km around an implosion site. These findings point to a number of complex and problematic issues regarding implosions and safeguarding human health and suggest that implosions in metropolitan areas should be prohibited. Further work to characterize the public health risks of conventional versus implosion demolition is recommended.

In plain English

This study reported air monitoring around the October 4, 1998 implosion of seven Calgary General Hospital (Bow Valley Centre) buildings in Calgary, Alberta. Beforehand, all friable and some nonfriable asbestos had been removed. Samples came from seven fixed stations 50 to 550 m away and a mobile van. Airborne asbestos counted by phase contrast microscopy was compared against 0.01 fibers/cm3, Alberta's indoor clearance criterion after asbestos abatement, which the authors applied to outdoor air. Levels exceeded it at several downwind locations within three hours, reaching 1.88 fibers/cm3 in a 22-minute sample at 550 m. Electron microscopy reanalysis also found elevated asbestos (highest 3-hour average 0.09 fibers/cm3), but calculated 24-hour averages were below the guideline. The article did not name asbestos fiber types. The authors estimated the cancer risk from a 15-minute exposure at about 1.8 in 10 million and called it negligible, but said this conclusion should be viewed very cautiously. The dust cloud affected air quality up to 20 km downwind. The authors concluded that all asbestos and lead-painted surfaces should be removed before implosion, and that implosions in metropolitan areas should be prohibited.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental air monitoring study of a single building implosion. It used fixed and mobile sampling before, during and after the event, with a health risk assessment comparing results to guidelines.
• Who was studied: The air around the Calgary General Hospital, Bow Valley Centre, in a residential community in Calgary, Alberta, Canada. Seven buildings over three stories tall were imploded on October 4, 1998. Samples came from seven fixed stations 50 to 550 m from the site and from a mobile van that tracked the dust cloud out to 25 km.
• Exposure: Dust from the building implosion. Measurements covered total suspended particles, PM10, PM2.5, airborne asbestos (counted by PCM and TEM; fiber types not stated) and airborne and settled lead. All friable and some nonfriable asbestos had been removed beforehand.
• Main results:
  • Airborne asbestos measured by phase contrast microscopy (PCM) during the implosion period (8:00 to 11:00 a.m.) exceeded the comparison criterion at a number of downwind locations. That criterion was 0.01 fibers/cm3, the Alberta indoor air clearance criterion following asbestos abatement, which the authors applied to these outdoor samples. The highest result was 1.88 fibers/cm3 in a 22-minute sample at location 7, 550 m east.
  • The comparison value for PCM asbestos was an indoor clearance criterion used after asbestos abatement.
  • A subset of samples was reanalyzed by transmission electron microscopy (TEM). TEM asbestos was elevated at downwind locations for the 3 hours after the implosion, with a maximum 3-hour average of 0.09 TEM fibers/cm3. All calculated 24-hour averages were below the guideline.
  • The authors estimated the public cancer risk from a 15-minute asbestos exposure near the site at 1.8 x 10^-7 (about 1.8 in 10 million), which they considered negligible. They accepted, 'with reservation', the hypothesis that there was no elevated asbestos health risk within 1 km.
  • The dust cloud affected air quality 20 km downwind, well beyond the 1-km advisory zone.
  • Estimated PM2.5 exposures above the authors' proposed 15-minute public health guideline occurred out to 4 or 5 km.
  • The 24-hour average airborne lead was elevated compared with background but was not above the 24-hour guideline. Lead in settled dust at location 6 (50 m south) was considered elevated under the HUD criterion, and the area was washed down with fire hoses.
• The authors' conclusion: The authors concluded that all nonfriable and friable asbestos and all lead-containing surfaces should be removed before an implosion. They also concluded that public advisory zones should extend 10 or 20 km, and that the difficulty of protecting the public suggests implosions in metropolitan areas should be prohibited.
• Limitations the authors state:
  • There is no established method to assess cancer risk from a brief asbestos exposure. The authors stated that spreading a short exposure over a lifetime is not appropriate, so the 'negligible risk' conclusion should be viewed very cautiously.
  • Movement of airborne lead and asbestos into homes, and tracking of outdoor surface contamination indoors, were not assessed.
  • The particulate exposure estimates assumed that the 15-minute exposure at 500 m applied further downwind. They also extrapolated instantaneous van readings to 15-minute exposures.

Topics

Medical terms in this study, explained in our Lexicon: Air Sampling, Friable.

Related studies

• Occurrence, spatial distribution, seasonal variations, potential sources, and inhalation-based health risk assessment of organic/inorganic pollutants in ambient air of Tehran — M. Kermani, Z. Asadgol, et al. (2021)
• Monitoring of airborne asbestos fibers in an urban ambient air of Shahryar City, Iran: levels, spatial distribution, seasonal variations, and health risk assessment — F. Taghizadeh, A.J. Jafari, et al. (2019)
• Composition of heavy metals and airborne fibers in the indoor environment of a building during renovation — M.T. Latif, N.H. Baharudin, et al. (2011)
• Ambient monitoring of asbestos in selected Italian living areas — A.F. Gualtieri, D. Mangano, et al. (2009)
• Indoor air quality differences between urban and rural preschools in Korea — C. Yoon, K. Lee, et al. (2011)
• Airborne asbestos concentrations in buildings — G.J. Burdett, S.A. Jaffrey (1986)

Browse more research in Journal of the Air & Waste Management Association, or return to medical research.