Original article

Scand J Work Environ Health 1995;21(5):345-352    pdf

doi:10.5271/sjweh.48

A cohort study of Swedish man-made vitreous fiber (MMVF) production workers, part 1: fiber exposure assessment in the rock/slag wool production industry 1938--1990

by Plato N, Krantz S, Gustavsson P, Smith TJ, Westerholm P

Objective A multiplicative model was developed to assess past exposure to respirable fibers among rock wool and slag wool production workers in Sweden 1938--1990.

Methods Information on job titles, work tasks and employment times of 1487 workers exposed to man-made vitreous fibers was obtained from company records and interviews with older employees. A mathematical model developed earlier for assessing historical fiber exposure, based on factory averages, was further developed. Matrices of multipliers for each plant that were specific for job title were modified to assess fiber exposure with respect to job title and calendar period. The model was based on measurements made in 1977. Two methods of exposure assessment were compared, cumulative exposure based on factory average (Model I), and cumulative exposure based on job title (Model II).

Results The exposure changed considerably in the two factories during the period 1938--1990, and varied also between job titles. The estimated average fiber (f) exposure level at the two plants in the middle of the 1940s was 1.32 f·ml-1 and 0.78 f·ml-1. These values are 26 and 16 times higher, respectively, than the exposure in 1980. Process changes, as well as the addition of binders and oil, reduced the exposure drastically around 1950. The mean cumulative respirable fiber exposure for the 1487 subjects was 1.44 (range 0.05--18.40) f·ml-1·year. The cleaners had 14 times higher annual fiber exposure than preproduction workers. Conclusions Model II was judged to be more valid than Model I in assessing exposure to man-made vitreous fibers.