M. Vantongeren et al., EFFICIENCY OF DIFFERENT GROUPING SCHEMES FOR DUST EXPOSURE IN THE EUROPEAN CARBON-BLACK RESPIRATORY MORBIDITY STUDY, Occupational and environmental medicine, 54(10), 1997, pp. 714-719
Objectives-The aim of this study was to assess the theoretical efficie
ncies of different grouping strategies and its effect on the exposure-
response relation in a study of respiratory morbidity associated with
exposure to total inhalable and respirable carbon black dust. Methods-
A large epidemiological study is being undertaken to investigate the r
espiratory health of employees in the European carbon black manufactur
ing industry in relation to exposure to carbon black dust. In phase 2
of the study, repeated measurements of total inhalable and respirable
dust were taken which enabled estimation of various components of vari
ability in the exposure data (within and between worker variance and w
ithin and between group variance). These variance components were used
to calculate the contrast in exposure between the groups in various c
lassification schemes and to calculate the theoretical attenuation of
the exposure-response relation and the standard error (SE) of the slop
e. Results-High contrast in exposure was found when workers were class
ified according to the combination of their factory and job category a
s well as when these combinations were amalgamated into five exposure
groups. Attenuation was minimal with most grouping schemes; only with
the individual based strategy was the attenuation large. The SE of the
theoretically attenuated exposure-response slope was smallest for the
strategy based on individual people followed by the classification sc
heme based on factory and job category. Conclusions-It was concluded t
hat, although some assumptions for the calculations of the attenuation
of the exposure-response slope were not met, the most appropriate cla
ssification scheme of the worker seems to be by the combination of fac
tory and job category.