Asbestos: toxicology and risk assessment for the general population in The Netherlands

Our plain-English summary of Asbestos: toxicology and risk assessment for the general population in The Netherlands, by G.K. Montizaan, A.G. Knaap, C.A. Van der Heijden (Food and Chemical Toxicology, 1989).

The study

• Authors: G.K. Montizaan, A.G. Knaap, C.A. Van der Heijden
• Journal: Food and Chemical Toxicology
• Published: 1989;27(1):53-63
• Type of article: Review
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Within the scope of the preparation of Integrated Criteria Documents for priority compounds in The Netherlands, the possible health effects of oral and inhalatory exposure to asbestos for the general population were evaluated. It was concluded from the results of experiments in animals that exposure to asbestos by the oral route is not carcinogenic and is not expected to present a health risk to the general population. Inhaled asbestos, however, is distinctly carcinogenic to man, giving rise to lung tumours, and mesotheliomas of the pleura and peritoneum. Chrysotile asbestos appears to be less potent in inducing mesotheliomas than the amphiboles, but all types of asbestos appear to have a similar potency for inducing lung cancer. The risk of mesothelioma is not expected to be influenced by smoking, whereas the risk of lung cancer is expected to be ten times higher in smokers than in non-smokers exposed to the same asbestos concentrations. Risk-assessment models for the inhalatory route, for the general population, are based on linear non-threshold extrapolation of occupational exposure to much lower environmental concentrations. These models give only a rough approximation of the risk of environmental exposure to asbestos. In accordance with the Air Quality Guidelines of the World Health Organization (World Health Organization, 1987), it was estimated that an extra risk of lung cancer of one in 10(6) (in the general population, with 30% smokers) may be presented by lifetime exposure to asbestos fibres longer than 5 microns, measured by electron microscopy, at concentrations of 100-1000/m3. It was further estimated that an extra risk of mesothelioma of one in 10(6) may be presented by lifetime exposure to 10-100 amphibole fibres/m3 or to a range of 100-10000 chrysotile fibres/m3 (fibres longer than 5 microns). From the current asbestos concentrations, the risk of mesothelioma for the general population in The Netherlands appears to be negligible; the extra risk of lung cancer is expected to be higher than 1 in 10(6) near asbestos sources, whereas it appears to be negligible in background areas and in most large cities and industrial areas. However, it must be borne in mind that the validity of the risk figures given is difficult to judge.

In plain English

This review assessed effects of swallowed and inhaled asbestos for the Dutch general population, adopting the World Health Organization's 1987 risk evaluation. Judging drinking-water studies severely biased, the authors concluded from animal experiments that swallowed asbestos is not carcinogenic and not expected to present a health risk. They concluded inhaled asbestos causes lung tumours and pleural and peritoneal mesotheliomas, that chrysotile appears less potent than amphiboles for mesothelioma but similar for lung cancer, and smoking raises lung cancer risk tenfold but not mesothelioma risk. They estimated lifetime exposure to 100-1000 fibres per cubic metre (longer than 5 micrometres, counted by electron microscopy) may add a one-in-a-million lung cancer risk where 30% of people smoke. The same extra mesothelioma risk was estimated for lifetime exposure to 10-100 amphibole or 100-10000 chrysotile fibres per cubic metre, similarly counted. At Dutch air levels, they judged mesothelioma risk negligible, and extra lung cancer risk probably above one in a million near asbestos sources but negligible in background areas and most large cities and industrial areas. They stressed the figures' validity is difficult to judge.

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: Review of published animal, human and laboratory studies, with a risk assessment for the general population based on the WHO Air Quality Guidelines (1987)
• Who was studied: The general population of The Netherlands (no new study subjects). The work was prepared for Dutch Integrated Criteria Documents.
• Exposure: Swallowed and inhaled asbestos (chrysotile and the amphiboles). The estimated Dutch outdoor air concentrations were mainly chrysotile: 255-2575 fibres per cubic metre near asbestos sources, 30-325 in large cities and industrial areas, and 10-100 in background areas.
• Main results:
  • Based on animal experiments, the authors judged that swallowed asbestos is not carcinogenic and is not expected to present a health risk to the general population.
  • Inhaled asbestos was judged carcinogenic to humans, causing lung tumours and mesotheliomas of the pleura and peritoneum.
  • Chrysotile appeared less potent than the amphiboles for mesothelioma, but all asbestos types appeared similar for lung cancer.
  • As a working hypothesis, the authors assumed chrysotile is 20 times less potent than the amphiboles for mesothelioma.
  • Smoking was not expected to influence mesothelioma risk. Lung cancer risk was expected to be ten times higher in smokers than in non-smokers at the same asbestos exposure.
  • The authors took the WHO risk evaluation and translated it into ranges of fibre concentrations giving an extra lifetime risk of one in a million, which they considered acceptable.
  • For a general population with 30% smokers, lifetime exposure to 100-1000 fibres per cubic metre (measured by electron microscopy) was estimated to give an extra lung cancer risk of one in a million.
  • An extra mesothelioma risk of one in a million was estimated for lifetime exposure to 10-100 amphibole fibres or 100-10000 chrysotile fibres per cubic metre (measured by electron microscopy). This estimate applied to both smokers and non-smokers.
  • The main risk from amphibole exposure appeared to be mesothelioma; for chrysotile exposure it appeared to be lung cancer.
  • In The Netherlands, the risk of lung cancer from asbestos was expected probably to be higher than one in a million near asbestos sources. It was expected to be negligible in most large cities and industrial areas and in background areas.
• The authors' conclusion: The authors concluded that, at current Dutch asbestos concentrations, the risk of mesothelioma for the general population appears negligible (lower than one in a million). They concluded that the extra lung cancer risk will probably be higher than one in a million near asbestos sources but appears negligible in background areas and in most large cities and industrial areas.
• Limitations the authors state:
  • The risk models give only a rough approximation of the risk from environmental asbestos exposure.
  • Extrapolating from workplace to environmental exposure is uncertain, more so because past workplace exposures were assessed inaccurately.
  • The estimates vary over many orders of magnitude, and even the validity of a given range is difficult to judge.
  • The workplace data generally lacked smoking information, so the lung cancer assessment had to assume that 30% of the population smoke.
  • All human studies of swallowed asbestos suffered from severe bias, so the oral assessment rested on animal experiments only.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Mesothelioma, Pleura, Peritoneum, Chrysotile, Amphibole Group, Lung Cancer, Occupational Exposure.

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