Epidemiological and quantitative relationships between mesothelioma and asbestos on Tyneside

Our plain-English summary of Epidemiological and quantitative relationships between mesothelioma and asbestos on Tyneside, by T. Ashcroft (Journal of Clinical Pathology, 1973).

The study

• Author: T. Ashcroft
• Journal: Journal of Clinical Pathology
• Published: 1973;26(11):832-40
• Cited by: 32 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002378).

Abstract

Thirty-five necropsied cases of diffuse malignant mesothelioma of pleura and six cases of mesothelioma of peritoneum are reported. Occupational histories from 40 cases showed that 32 cases (80%) were definitely exposed to asbestos; six cases (15%) were probably exposed and two (5%) had no known exposure. The mean latent interval was 34 years. Occupational histories of 56 control patients matched in pairs for age and sex with 28 of the mesothelioma cases revealed definite exposure to asbestos in 12 controls (21%), probable exposure in 11 (20%), and no evidence of exposure in 33 (59%). The difference in incidence of exposure between mesotheliomas and controls is statistically highly significant. Six-micron histological sections of lung, available in 39 mesothelioma cases, contained coated asbestos fibres in 36 cases (92%). Sixteen cases of mesothelioma showing fibres were free of asbestosis; asbestosis was slight in 14 cases, moderately severe in five cases, and severe in one case. The incidence of asbestos bodies in sections from mesothelioma cases was significantly higher than in a previously reported series of routine necropsies examined by lung smear. Counts of coated and uncoated asbestos fibres were performed on samples of lung tissue from 33 mesothelioma cases. No fibres were identified in one case and only occasional coated fibres in a second case. The remainder gave counts ranging from 154 thousand to 684 million fibres per gram dry weight. Uncoated fibres were invariably present and usually comprised 50 to 80% of the count. No relationship was found between total fibre count and the latent period of the mesothelioma. Fibre counts were also performed on lung samples from 18 smear-positive and 30 smear-negative routine necropsies. Cases with numerous coated fibres in the smear gave total fibre counts similar to those of mesothelioma cases without asbestosis. Routine cases with only one fibre in the smear usually yielded only occasional fibres on analysis. Coated and uncoated fibres were found in 13 out of 30 smear-negative cases, indicating a true incidence of 56% of exposure to asbestos in the whole necropsy series. When compared with the mesothelioma series the difference in incidence of fibres remains statistically significant. The data suggest that, on Tyneside, exposure to asbestos sufficient to cause an appreciable risk of developing mesothelioma has usually occurred through occupational exposure rather than by general environmental pollution by asbestos.

In plain English

The study examined 41 necropsied (autopsied) cases of diffuse malignant mesothelioma, all but three from the Tyneside area. Thirty-five had pleural and six had peritoneal mesothelioma. Of 40 with occupational histories, 32 (80%) had definite, six (15%) probable and two (5%) no known asbestos exposure. Most of the 32 definitely exposed patients had used asbestos insulation or worked beside insulation workers. The mean time from first exposure to mesothelioma was 34 years. Among 56 age- and sex-matched controls without cancer, 12 (21%) had definite and 23 (41%) definite or probable exposure. This was a statistically highly significant difference from the mesothelioma patients. Coated asbestos fibres appeared in lung sections in 36 of 39 cases. Of 33 cases with lung fibre counts, one had none, one had only occasional fibres, and 31 had 154 thousand to 684 million fibres per gram dry weight. Total fibre count showed no relationship with the latent period. The author estimated that about 56% of routine necropsies had coated fibres, significantly fewer than among mesothelioma cases. The author concluded that on Tyneside, exposure sufficient to cause an appreciable mesothelioma risk had usually come from work rather than general environmental pollution.

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: Case series of necropsied mesothelioma cases, with occupational histories compared against age- and sex-matched controls, lung fibre counts, and comparison with routine necropsies
• Who was studied: 41 necropsied mesothelioma cases (35 pleural, 6 peritoneal; 36 male, 5 female; average age 57, range 42 to 76), found mainly through records of the principal Tyneside hospitals. Three cases came from beyond the Tyneside area. Necropsy records were generally included from 1948 onwards, and collection ceased in September 1969. Comparison groups: 56 control patients matched in pairs for age and sex with 28 mesothelioma cases, and 310 routine necropsies at the Royal Victoria Infirmary examined by lung smear.
• Exposure: Mostly occupational asbestos exposure. Among the 32 definitely exposed patients, most had used asbestos insulation materials or worked beside insulation workers. Only four patients had worked in an asbestos factory. One case was the widow of an asbestos worker who came home with asbestos dust on his hair and shoes. No patient had pure exposure to any one mineral variety of asbestos. The author described dust concentrations as generally low.
• Main results:
  • Of 40 mesothelioma patients with occupational data, 32 (80%) had definite, six (15%) probable, and two (5%) no known asbestos exposure
  • Mean latent interval (first exposure to mesothelioma) was 34 years, range 18 to 58 years
  • Among 56 matched controls, 12 (21%) had definite exposure and 23 (41%) had definite or probable exposure. Among 27 mesothelioma patients, 19 (70%) had definite exposure and 25 (92%) had definite or probable exposure. The difference was statistically highly significant (chi-square 16.6 for definite and 17.8 for definite plus probable, both p less than 0.001).
  • Coated asbestos fibres were found in lung sections in 36 (92%) of 39 mesothelioma cases. Asbestosis was absent in 16 of these, slight in 14, moderate in five and severe in one.
  • In lung fibre counts from 33 mesothelioma cases, one case had no fibres and one had only occasional fibres. Neither had a history of exposure. The remaining 31 ranged from 154 thousand to 684 million fibres per gram dry weight, with uncoated fibres usually 50 to 80% of the count.
  • No relationship was found between total fibre count and latent period in mesothelioma cases
  • Coated fibres were found in lung sections of male mesothelioma cases much more often than in lung smears of male routine necropsies (25%). The difference was statistically highly significant (chi-square 47.8, p less than 0.001).
  • Tissue digestion found fibres in 13 of 30 smear-negative routine necropsies. On this basis the author estimated a true incidence of coated fibres of about 56% in routine necropsies, still significantly lower than in mesothelioma cases.
  • Routine necropsies with numerous coated fibres in smears had fibre counts comparable with most mesothelioma cases. 29 of 31 mesothelioma cases had fibre concentrations at or above that level.
• The authors' conclusion: The author concluded that on Tyneside, asbestos exposure sufficient to cause an appreciable risk of mesothelioma had usually occurred through occupational exposure rather than general environmental pollution. Because Tyneside's mesothelioma cases were fewer than 0.1% of persons apparently at risk from the asbestos content of their lungs, the author also suggested that some other factor besides asbestos may be involved.
• Limitations the authors state:
  • Coated bodies resembling asbestos bodies can form on non-asbestos fibres, so some coated fibres in routine smears might not indicate asbestos, although the author judged most were likely asbestos
  • Six biopsy cases highly suggestive of mesothelioma were excluded because no necropsy was performed
  • Some hospital departments lacked necropsy records before 1958
  • The 30 smear-negative specimens were assumed to be random samples of the necropsies surveyed

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Malignant Mesothelioma, Pleura, Peritoneum, Asbestos Bodies, Autopsy, Occupational Exposure.

Related studies

• Asbestos bodies in routine necropsies on Tyneside: a pathological and social study — T. Ashcroft (1968)
• Occupational exposures and colorectal cancers: a quantitative overview of epidemiological evidence — E. Oddone, C. Modonesi, et al. (2014)
• Pulmonary function and pleural fibrosis: quantitative relationships with an integrative index of pleural abnormalities — R. Lilis, A. Miller, et al. (1991)
• Pleural mesothelioma and occupational and non-occupational asbestos exposure: a case-control study with quantitative risk assessment — D. Ferrante, D. Mirabelli, et al. (2016)
• Quantitative relationships of exposure to chrysotile asbestos and mesothelioma mortality — D. Loomis, D.B. Richardson, et al. (2019)
• Quantitative relationship of fecal asbestos to asbestos exposure — H.M. Cunningham, R.D. Pontefract, et al. (1976)

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