Historical state of knowledge of the health risks of asbestos posed to seamen on merchant ships

Our plain-English summary of Historical state of knowledge of the health risks of asbestos posed to seamen on merchant ships, by D.G. Dodge, B.D. Beck (Inhalation Toxicology, 2016).

The study

• Authors: D.G. Dodge, B.D. Beck
• Journal: Inhalation Toxicology
• Published: 2016;28(14):637-657
• Type of article: Historical article, Review
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We examined the development of knowledge concerning the risks posed by asbestos to seamen working aboard merchant ships at sea (i.e. commercial, rather than naval vessels). Seamen were potentially exposed to "in-place" asbestos on merchant ships by performing intermittent repair and maintenance tasks. We reviewed studies measuring airborne asbestos onboard merchant ships and health outcomes of merchant seamen, as well as studies, communications, and actions of U.S. organizations with roles in maritime health and safety. Up to the 1970s, most knowledge of the health risks of asbestos was derived from studies of workers in asbestos product manufacturing and asbestos mining and milling industries, and certain end-users of asbestos products (particularly insulators). We found that attention to the potential health risks of asbestos to merchant seamen began in the mid- to late 1970s and early 1980s. Findings of pleural abnormalities in U.S. seamen elicited some concern from governmental and industry/labor organizations, but airborne asbestos concentrations aboard merchant ships were found to be <1 f/cc for most short-term repair and maintenance tasks. Responses to this evolving information served to warn seamen and the merchant shipping industry and led to increased precautions regarding asbestos exposure. Starting in the 1990s, findings of modest increases in lung cancer and/or mesothelioma in some epidemiology studies of seamen led some authors to propose that a causal link between shipboard exposures and asbestos-related diseases existed. Limitations in these studies, however, together with mostly unremarkable measures of airborne asbestos on merchant ships, preclude definitive conclusions in this regard.

In plain English

This review traced how knowledge developed about asbestos risks to seamen on merchant (commercial, not naval) ships. The authors reviewed studies, air-sampling reports, government, union and industry documents, and 1980 Congressional hearings. They found maritime health and safety organizations first addressed it in the mid- to late 1970s and early 1980s. The Coast Guard's first official recommended procedures for controlling merchant crews' asbestos exposure came in its 1980 circular NVIC 5-80, which was guidance, not law. Among reviewed studies, Jones et al. (1984) found pleural abnormalities in 12% of over 5000 U.S. marine engineers. A 1981 shipboard repair study's personal samples ranged from non-detect to 3.40 f/cc in the text, but the article's table lists estimated welding results up to 5.0 f/cc. Most cancer studies reviewed found modest, statistically significant increases in lung cancer and/or mesothelioma in some groups of non-U.S. seamen, especially engine room workers. The authors concluded that limitations in these studies, including missing smoking and job histories, preclude concluding a causal link. Both authors disclosed serving as litigation experts. Defendants' law firms funded most of the underlying litigation-related research.

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 historical documents and published studies (a historical state-of-knowledge review)
• Who was studied: Documents covering several decades: scientific literature on merchant seamen's health, studies of airborne asbestos on merchant ships, U.S. government and maritime industry and labor documents, and U.S. Congressional hearing proceedings
• Exposure: 'In-place' asbestos on merchant ships disturbed during intermittent repair and maintenance. Most asbestos used to build and repair U.S. naval and merchant ships was chrysotile and amosite insulation, installed from the early 1930s to the mid- to late 1970s.
• Main results:
  • The authors found that attention to the potential asbestos risks to merchant seamen began in the mid- to late 1970s and early 1980s.
  • The U.S. Coast Guard's Navigation and Vessel Inspection Circular 5-80 (1980) was the first official Coast Guard publication of recommended procedures for controlling asbestos exposure of crew members on merchant vessels.
  • Navigation and Vessel Inspection Circulars provide guidance but do not have the force of law.
  • In the reviewed study by Jones et al. (1984) of chest films of more than 5000 U.S. marine engineers, 12% had pleural abnormalities, including plaques suggestive of past asbestos exposure.
  • In the reviewed MARAD-contracted study (Jones, 1981) of repair and maintenance tasks on ships at sea, the article's text gives personal samples as non-detect to 3.40 f/cc and area samples as non-detect to 70 f/cc. The 70 f/cc reading came from a 4-minute sample taken during brake box cleaning with a blower.
  • The article's Table 5 (adapted from Jones, 1981) lists two personal welding samples, lasting 10 to 16 minutes, at an estimated 2.2 to 5.0 f/cc. This is higher than the 3.40 f/cc upper end of the personal-sample range given in the text.
  • In the reviewed analysis by Murbach et al. (2008), background area samples were taken on operating merchant ships from 1978 to 1992, not during work with asbestos-containing materials. The mean of 1018 area samples was 0.008 f/cc, and 1.4% exceeded 0.1 f/cc.
  • Most of the reviewed lung cancer and mesothelioma studies found a modest but statistically significant increase in one or more categories of seamen, especially engine room workers. The studies that found these increases were all of non-U.S. seamen.
• The authors' conclusion: The authors concluded that many study authors have suggested a causal link between shipboard asbestos exposure and asbestos-related disease in seamen, but that limitations in these studies preclude that conclusion. They also concluded that the scientific literature on U.S. merchant seamen is sparse.
• Limitations the authors state:
  • The authors state that the epidemiology studies they reviewed lacked smoking histories and employment histories, and that there were few studies of U.S. seamen.
  • The authors state that none of the health studies of seamen provided quantitative information on asbestos exposure.
  • The authors state they cannot rule out scenarios with more significant exposure, such as frequent conduct of the dustiest tasks over many years.
  • The authors disclosed that both have served as experts in asbestos litigation.
  • The authors disclosed that the underlying research was mostly done in preparation of experts for litigation, and that this effort was funded by law firms for defendants.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Shipyards and maritime work, The Navy.

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

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