ERA Merewether - And asbestos

Our plain-English summary of ERA Merewether - And asbestos, by T. Waldron (Journal of Medical Biography, 2021).

The study

• Author: T. Waldron
• Journal: Journal of Medical Biography
• Published: 2021;29(4):189-195
• Read it: PubMed · Publisher

Abstract

After a succession of posts and studying for the Bar, Edward Merewether joined the Medical Inspectorate of Factories in 1927. Not long thereafter he was asked to undertake a study of the effects of asbestos exposure on the lungs. His results showed that asbestos workers had a significant risk of developing pulmonary fibrosis and this resulted in the promulgation of regulations to limit exposure. Some years later, Merewether showed that asbestos workers also had a higher than expected risk of developing lung cancer, but on this occasion there was no further protective legislation, and the association was not generally accepted until some years later. Merewether's name is inextricably linked with the risks of asbestos exposure but after his death the importance of his efforts was often played down by those who wished to show that the government had not acted quickly enough, or vigorously enough to control the hazard. The contention of this paper is that these criticisms are not justified and that Merewether acted to the best of his ability, given the conditions and knowledge current at the time he was working.

In plain English

This article is a historical biography, not a new study. The author traced the career of Edward Merewether, a British Medical Factory Inspector from 1927, and Merewether's work on asbestos. As the author recounted, Merewether's survey of 363 asbestos workers, reported in 1930 with the engineering inspector Charles Price, found pulmonary fibrosis in 95 men (26.2%). Among men exposed for 20 years or more, the figure was 17 of 21 (81.0%). Re-examining the figures with confidence intervals, the author noted that not every step up in length of exposure made a statistically significant difference, and attributed this to the non-random choice of workers. The Asbestos Industry Regulations 1931 followed the survey. A later survey that Merewether started in 1947 found that 31 of 235 asbestos workers who had died had died of lung cancer. Among silica-exposed workers, 91 of 6884 deaths were from lung cancer. The regulations were not amended in response and were updated only in the 1960s. The author argued that later criticism of Merewether is not justified given what was known at the time. The author also stated that the Home Office ought to have reconsidered the regulations in light of the 1947 lung cancer 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: historical biographical article (a biography of a medical factory inspector, including the author's re-examination of figures from historical surveys); not an original study
• Who was studied: The life and work of Edward Merewether, a UK Medical Factory Inspector (appointed 1927, retired 1957). The article describes Merewether's 1928 to 1930 survey of 374 asbestos workers, 363 of whom were analysed, and a 1947 survey of deaths among asbestos workers from 1924 to 1946.
• Exposure: Asbestos dust in UK asbestos factories. Processes named include preparing and handling raw asbestos, carding, weaving, mattress making and spinning. The 1947 survey compared asbestos workers with workers exposed to silica. Specific fiber types are not named for these surveys.
• Main results:
  • In Merewether's survey, as reported in this article, 95 of 363 asbestos workers had pulmonary fibrosis, a prevalence of 26.2% (95% confidence interval 21.9 to 30.9).
  • Prevalence by years of exposure (Table 1): 0 of 89 for under 5 years. For 5 to under 10 years, 36 of 141 (25.5%, 95% CI 19.1 to 33.3). For 10 to under 15 years, 27 of 84 (32.1%, 23.1 to 42.7). For 15 to under 20 years, 15 of 28 (53.6%, 35.8 to 70.5). For 20 years or more, 17 of 21 (81.0%, 60.0 to 92.3).
  • The author's re-examination found no statistically significant difference between the 5-year and 10-year exposure groups, nor between the 15-year and 20-plus-year groups. There was a significant difference between those exposed 5 to 10 years and those exposed 15 years or more.
  • Of 133 workers X-rayed in Merewether's survey, 62 were judged to have definite pulmonary fibrosis, 10 of them as a result of other dusty trades. The author gives a prevalence of definite fibrosis of 39.1% (95% CI 31.2 to 47.6).
  • In the 1947 survey Merewether initiated, 31 of 235 asbestos workers who died between 1924 and 1946 had died of lung cancer (22 of 128 males, 9 of 107 females). Among silica-exposed workers who died from 1930 to 1946, 91 of 6884 deaths were from lung cancer. The proportions were 13.2 (95% CI 9.5 to 18.1) for asbestos workers and 1.3 (95% CI 1.1 to 1.6) for silica workers, p less than 0.0001.
  • According to the author, the lung cancer findings did not lead the Ministry of Labour to amend the Asbestos Industry Regulations, and the regulations were not updated until the 1960s.
• The authors' conclusion: The author concluded that criticism of Merewether is not justified, and that Merewether should not be blamed for not acting on information that later critics had. The author also stated that the Home Office ought to have reconsidered the regulations after the 1947 lung cancer data.
• Limitations the authors state:
  • The author notes that workers were not selected at random for Merewether's survey; the emphasis was on those exposed 10 years or more and those exposed 5 years or less.
  • The author notes that chest X-rays were offered on the basis of convenience, only to men near large centres with X-ray facilities.
  • The author notes that the sample was probably only about 5% of exposed workers, not the roughly 17% Merewether assumed.
  • The author states that the survey might have been better planned and probably under-estimated the true risk.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pulmonary Fibrosis, Lung Cancer.

Related studies

• Knowledge of the health hazard of asbestos prior to the Merewether and Price report of 1930 — M. Greenberg (1994)
• Penetration of overall hoods by water-borne crocidolite fibres — R. Goode, T. Waldron (1977)

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