Community health risk assessment after a fire with asbestos containing fallout

Our plain-English summary of Community health risk assessment after a fire with asbestos containing fallout, by S. Bridgman (Journal of Epidemiology and Community Health, 2001).

The study

• Author: S. Bridgman
• Journal: Journal of Epidemiology and Community Health
• Published: 2001;55(12):921-7
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: A factory fire in Tranmere, Merseyside, England, deposited asbestos containing fallout in an urban area. There was considerable community anxiety for months after the incident. Therefore an assessment of the long term health risks of this acute environmental incident were requested by the local health authority.

Methods: The facts of the incident were gathered and appraised from unpublished and press reports, involved personnel, and further analysis of material collected at the time of the incident. The literature on the long term health risks of asbestos was reviewed, and combined with evidence on asbestos exposure to estimate community health risk.

Results: Risk was almost entirely from exposure to fire fallout of chrysotile in asbestos bitumen paper covering the factory roof. Amosite was only detected in a few samples and in trace amounts. The number of people who lived in the area of fallout was 16 000 to 48 000. From a non-threshold model with assumptions likely to overestimate risk, the lung cancer risk is estimated to be undetectably small. Risk of mesothelioma from chrysotile exposure, and risks of lung cancer and mesothelioma from amosite exposure were based on observational studies and were estimated to be even lower than that of lung cancer risk from chrysotile exposure. Academically, there are assumptions that while reasonable cannot be proven, for example, the validity of extrapolating observed risk from much higher exposures to lower exposures, estimates of individual exposure, and that there is no threshold for asbestos to cause cancer.

Conclusions: The author is unaware of a similar study on long term health risks in a community exposed to asbestos in a fire. It is concluded that, using methods that do not underestimate risk, risk is undetectably small. Practical lessons from this methodology and approach to health risk assessment are discussed.

In plain English

This paper assessed the long-term health risks to people living near a fire at a disused leather factory in Tranmere, Merseyside, England, on 22 September 1994. Fallout from the fire contained asbestos. The author gathered facts about the incident, re-analysed fallout samples, and combined estimated exposure with published studies of asbestos-exposed workers. The asbestos in the fallout came mainly from chrysotile in asbestos bitumen paper on the factory roof. A few early samples showed probable amosite, in trace or unquantified amounts. Air samples taken during demolition did not exceed normal background levels. An estimated 16 000, 32 000 and 48 000 people lived in areas of greatest to least fallout density. Because of rain, exposure from fibres released during the fire was assumed to last no more than 48 hours. Fibres could also be released when deposited material was disturbed. A linear non-threshold model assumed exposure at the UK industrial control limit for two days. On that basis, lung cancer risk from chrysotile was estimated to be immeasurably small. Mesothelioma and amosite risks, estimated without good quantitative models, were also judged immeasurably or undetectably small. The author noted there were no accurate individual exposure data.

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: Community health risk assessment that combined information and sample analyses from the incident with a review of published literature on asbestos health risks
• Who was studied: People living in the urban area of fallout from a factory fire in Tranmere, Merseyside, England, on 22 September 1994. Populations were estimated at 16 000, 32 000 and 48 000 for areas of greatest to least density of fallout, based on mapping of 105 telephone calls from the public. In addition, 134 firemen, 19 policemen and about 20 clean-up workers attended the incident.
• Exposure: Fire fallout containing chrysotile from asbestos bitumen paper on the factory roof, estimated at 240 kg of chrysotile. Trace amounts of amphibole, probably amosite, were found in a few samples. Exposure from fibres released during the fire was assumed to last no more than 48 hours. Fibres would also have been released when deposited material was disturbed.
• Main results:
  • Of six fallout samples analysed early by the Health and Safety Executive, all had substantial chrysotile. One had a trace of amosite and two had unquantified amounts of amosite. The author stated these are correctly described as a trace of amphibole asbestos, probably amosite.
  • In the second batch of samples, analysed later, most contained around 50% chrysotile and none contained amosite.
  • All 12 air samples taken during demolition of the factory were below the lowest reliably detectable level above background. The author concluded that airborne asbestos fibre levels did not exceed normal background levels. The counting method could not tell asbestos from non-asbestos fibres.
  • An insignificant number of chrysotile fibres was found in the outer fabric of firemen's tunics, averaging 2.7 fibres per square foot on each of two tunics. No asbestos fibres were found on a policeman's uniform or a fireman's raincoat.
  • The author stated that fibres would have been released both when the roof broke up during the fire and when material deposited in the environment was disturbed.
  • Because of rainfall two days after the fire, exposure from fibres released during the fire was assumed to have lasted no more than 48 hours.
  • The author used the linear non-threshold model and assumed exposure at the UK industrial control limit for two days. On that basis, the long-term lung cancer risk from chrysotile for the exposed communities was estimated to be immeasurably small. In a worked example (0.1 fibres per ml for two days, constant b of 0.0006), about 14 million people would need to be exposed for one extra lung cancer death.
  • Mesothelioma risk from chrysotile was also estimated to be immeasurably small. This was based on Rochdale textile workers, in whom excess mesothelioma risk was 10% to 20% of lung cancer risk. The risk from any amosite exposure in this incident was judged undetectably small.
• The authors' conclusion: The author concluded that the long-term cancer risk from the incident was immeasurably small. The author stated that neither the model nor the exposure assumptions were likely to underestimate risk.
• Limitations the authors state:
  • There were no accurate individual exposure data.
  • The risk models came from past industrial exposures far higher than in this incident. They therefore do not include the low exposure levels they were used to predict.
  • Neither the presence nor the absence of an exposure threshold for asbestos-caused cancer can be proven.
  • How exactly asbestos fibres cause cancer is uncertain.
  • It was difficult to take into account age at exposure, duration of exposure, fibre size, fibre type, cigarette smoking and individual exposure amounts.
  • There were no good quantitative models for mesothelioma from chrysotile or for cancer from amosite, so only qualitative estimates were possible.
  • The only air samples were taken during demolition, and the counting method could not distinguish asbestos from non-asbestos fibres.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Chrysotile, Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Chrysotile, Amosite, Lung Cancer, Mesothelioma.

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