Different ways to describe historic fibre exposure from asbestos-conta
ining friction materials were studied and compared for a group of 103
car and bus mechanics with more than 20 years employment and 15 years
of asbestos exposure. A model was constructed to calculate cumulative
asbestos exposure from friction materials including duration, intensit
y and exposure last year. The model is a combination of an additive an
d a multiplicative model, where an asbestos index was constructed that
takes both near field and far field exposure into consideration. The
model was based upon data from the international literature and quanti
tative asbestos measurements performed 1976-1988 in Swedish car repair
workshops. The fibres were counted by phase-contrast microscopy with
fibre criteria of length > 5 mu m and aspect ratio greater than or equ
al to 3:1. The mechanics' fibre exposure at 398 repair workshops durin
g a period of 48 years were calculated using the model. The mean cumul
ative exposure was estimated to be 2.6 f ml(-1) year. The annual cumul
ative exposure was highest for truck mechanics in the early 1960s. The
car mechanics had a time-weighted average fibre exposure range of 0.1
1-0.41 f ml(-1) (mean 0.21 f ml(-1))in 1965 compared to 0.003-0.08 f m
l(-1) (mean 0.021 f ml(-1))in 1985. In order to validate the model, th
e mechanics' fibre exposure estimated using the model were compared wi
th representative asbestos exposure measurements for car mechanics dur
ing the 1960s and the 1970s (correlation coefficient = 0.69). Five lun
g physiological variables (FVC, TLC, FEV(1), TL(co) and CV%) were used
to study exposure-response relationships. None of the exposure parame
ters suggested any significant relationship between exposure and decre
ase in lung function.