Linking expert judgement and trends in occupational exposure into a job-exposure matrix for historical exposure to asbestos in the Netherlands

Our plain-English summary of Linking expert judgement and trends in occupational exposure into a job-exposure matrix for historical exposure to asbestos in the Netherlands, by P. Swuste, M. Dahhan, A. Burdorf (The Annals of Occupational Hygiene, 2008).

The study

• Authors: P. Swuste, M. Dahhan, A. Burdorf
• Journal: The Annals of Occupational Hygiene
• Published: 2008;52(5):397-403
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The aim of this article was to describe the structure and content of a job-exposure matrix (JEM) for historical asbestos exposure in The Netherlands. The JEM contained 309 occupational job title groups in 70 branches of industry during 10 periods of 5 years during 1945-1994, resulting in 3090 evaluations. Dutch sources on asbestos exposure measurements provided quantitative guidance for 69 evaluations (2.2%) in 25 occupational title groups. In addition, three databases from the UK Health and Safety Executive contributed to 222 evaluations (7.2%) and several other sources aided in another 133 evaluations (4.3%). These evaluations resulted in seven categories of exposure levels for all 3090 combinations of occupational title groups and periods. A verification process with five experts was used to adjust the assignments of exposure categories. The trends in exposure patterns over time were described in relation to production activities, operational control measures and the presence of dust control measures. For the majority of asbestos-related diseases in the past decades, reliable information on their historical exposure patterns was lacking. The limited availability of exposure measurements in the past illustrates the need for a structured assessment of historical asbestos exposure through a JEM.

In plain English

The authors built a job-exposure matrix, a tool estimating asbestos exposure by job, for Dutch industry from 1945 to 1994. It covered 309 job title groups in 70 industry branches over ten five-year periods: 3090 evaluations. Dutch measurements guided only 69 evaluations (2.2%); five measured situations were available before 1970. British Health and Safety Executive databases contributed to 222 evaluations (7.2%), other sources to 133 (4.3%). The rest relied on the authors' judgement, using working-condition descriptions, job similarities and extrapolation from more recent data. Five experts reviewed 350 evaluations and changed 15 by one category. Only the asbestos-cement industry had enough Dutch data. In one facility there, average exposure fell over 90% in 20 years from 1970. The authors said controls such as local exhaust ventilation could explain this, but its representativeness is unknown. They noted possible substantial misclassification before 1970. Measurements were mostly of chrysotile, so crocidolite and amosite exposure patterns could not be described. The authors concluded that scarce historical measurements show the need for such a matrix, which should be used with information on work processes.

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: Development of a job-exposure matrix (exposure-estimation tool) combining available measurement data with expert judgement
• Who was studied: 309 occupational job title groups in 70 branches of Dutch industry, each assessed for 10 five-year periods covering 1945 to 1994 (3090 evaluations)
• Exposure: Occupational asbestos exposure, estimated in seven levels of fibres per ml of air (0, 0.01 to 0.5, 0.5 to 1, 1 to 2, 2 to 5, 5 to 10, and 10 or more). The underlying measurements were mostly of chrysotile, and the data were not sufficient to describe crocidolite or amosite exposure separately.
• Main results:
  • Dutch exposure measurement sources provided quantitative guidance for 69 of the 3090 evaluations (2.2%), in 25 occupational title groups
  • Three UK Health and Safety Executive databases contributed to 222 evaluations (7.2%), and several other sources aided in another 133 evaluations (4.3%)
  • Quantitative information before 1970 was scarce, with only five measured situations
  • Without measurements, the matrix relied on experts translating qualitative descriptions of working conditions into expected exposure levels
  • Jobs without exposure information were assigned levels from comparable jobs with measurements in other industries
  • Exposure levels for periods before 1970 were extrapolated from more recent measurement data
  • When the same exposure level was assigned to other jobs in the same exposure group, quantitative information was available for 13.5% of evaluations on occupational exposure groups
  • In the expert verification, 15 of 350 evaluations had their exposure estimate moved up or down by one category
  • In the Dutch asbestos-cement industry during 1970 to 1974, average exposure exceeded 2 fibres per ml in three of six exposure groups. It was highest for jobs handling raw asbestos and finishing dry asbestos-cement products.
  • The asbestos-cement measurements came from one facility, the largest plant in the Netherlands. There, average exposure fell in each period, a total reduction of over 90% during 20 years. The authors said this could be attributed to measures such as local exhaust ventilation, vacuum cleaning, wet finishing and an enclosed bag cutter.
  • The matrix also includes a database of 300 commercially available asbestos products in the Netherlands from 1938 onwards
• The authors' conclusion: The authors concluded that the limited historical measurements show the need for structured assessment through a job-exposure matrix. Because of large uncertainties, its use in research and individual cases should always be accompanied by qualitative information on work processes and techniques.
• Limitations the authors state:
  • Substantial misclassification may be present for periods without measurement data, mainly before 1970, when estimates were extrapolated from later data
  • The asbestos-cement trend came from one facility, and it is unknown whether it represents the Dutch asbestos-cement industry or other industries
  • For the construction industry, only scattered measurements existed, too few to infer a time trend
  • Without information on sampling techniques and strategies, true exposure trends are hard to separate from changes in measurement methods
  • Measurements were mostly of chrysotile, so exposure patterns for crocidolite and amosite could not be described
  • The validity of the matrix is difficult to demonstrate

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Asbestos Exposure, Dust Control.

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