Are variance components of exposure heterogeneous between time periods and factories in the European carbon black industry?Citation formats

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Are variance components of exposure heterogeneous between time periods and factories in the European carbon black industry? / Van Tongeren, Martie; Burstyn, Igor; Kromhout, Hans; Gardiner, Kerry.

In: Annals of Occupational Hygiene, Vol. 50, No. 1, 01.2006, p. 55-64.

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Van Tongeren, Martie ; Burstyn, Igor ; Kromhout, Hans ; Gardiner, Kerry. / Are variance components of exposure heterogeneous between time periods and factories in the European carbon black industry?. In: Annals of Occupational Hygiene. 2006 ; Vol. 50, No. 1. pp. 55-64.

Bibtex

@article{027f567906c54b489955d55e3e758496,
title = "Are variance components of exposure heterogeneous between time periods and factories in the European carbon black industry?",
abstract = "Occupational exposure to chemical agents can vary enormously within- and between-workers, even when carrying out the same jobs. When repeated measurements are available, the variance components can be estimated using random- or mixed-effects models. Pooling the variance components across the fixed effects, in mixed-effects models, reduces the complexity of the models; especially, when there are a large number of fixed effects. The analyses presented in this paper tested the assumptions of homogeneity in the variance components between factories and surveys for inhalable dust exposure in the European carbon black manufacturing industry. In total, 5296 measurements from 1771 workers were available collected during two surveys carried out between 1991 and 1995. Workers were grouped into eight job categories, and for each of these separate mixed-effects models were developed, including factory, survey and in some cases the interaction term as the fixed effects. The likelihood ratio test was used to test the assumptions of homogeneity of the variance components. Statistically significant heterogeneity of the variance components was observed for two of the eight job categories, 'Fitter/Welder' and 'Warehouseman'. The heterogeneity was due mainly to differences in variance between the factories. When estimating the probability of overexposure for all the factories combined, there was little difference between the models with and without heterogeneous variance components for 'Fitters/Welders'. For the 'Warehousemen' the probability of overexposure in the last survey changed marginally from 4% in the pooled model to 6% in the heterogeneous model. Larger differences between the models were observed when estimating the probability of overexposure for individual factories, which was due to over- or underestimation of the variance components in the pooled models. In conclusion, for most job categories pooling of the variance components appears to be justified in this database. In addition, no large differences were found when determining the industry-wide probability of 'overexposure' when comparing the pooled with the heterogeneous models. However, when evaluating the factory-specific probability of 'overexposure' or when using the models to provide exposure estimates for epidemiological studies heterogeneity in the variance components should be investigated. {\textcopyright} 2005 British Occupational Hygiene Society.",
keywords = "Exposure modelling, Mixed effects models, Variance compounds",
author = "{Van Tongeren}, Martie and Igor Burstyn and Hans Kromhout and Kerry Gardiner",
year = "2006",
month = jan
doi = "10.1093/annhyg/mei041",
language = "English",
volume = "50",
pages = "55--64",
journal = "Annals of Occupational Hygiene",
issn = "0003-4878",
publisher = "Oxford University Press",
number = "1",

}

RIS

TY - JOUR

T1 - Are variance components of exposure heterogeneous between time periods and factories in the European carbon black industry?

AU - Van Tongeren, Martie

AU - Burstyn, Igor

AU - Kromhout, Hans

AU - Gardiner, Kerry

PY - 2006/1

Y1 - 2006/1

N2 - Occupational exposure to chemical agents can vary enormously within- and between-workers, even when carrying out the same jobs. When repeated measurements are available, the variance components can be estimated using random- or mixed-effects models. Pooling the variance components across the fixed effects, in mixed-effects models, reduces the complexity of the models; especially, when there are a large number of fixed effects. The analyses presented in this paper tested the assumptions of homogeneity in the variance components between factories and surveys for inhalable dust exposure in the European carbon black manufacturing industry. In total, 5296 measurements from 1771 workers were available collected during two surveys carried out between 1991 and 1995. Workers were grouped into eight job categories, and for each of these separate mixed-effects models were developed, including factory, survey and in some cases the interaction term as the fixed effects. The likelihood ratio test was used to test the assumptions of homogeneity of the variance components. Statistically significant heterogeneity of the variance components was observed for two of the eight job categories, 'Fitter/Welder' and 'Warehouseman'. The heterogeneity was due mainly to differences in variance between the factories. When estimating the probability of overexposure for all the factories combined, there was little difference between the models with and without heterogeneous variance components for 'Fitters/Welders'. For the 'Warehousemen' the probability of overexposure in the last survey changed marginally from 4% in the pooled model to 6% in the heterogeneous model. Larger differences between the models were observed when estimating the probability of overexposure for individual factories, which was due to over- or underestimation of the variance components in the pooled models. In conclusion, for most job categories pooling of the variance components appears to be justified in this database. In addition, no large differences were found when determining the industry-wide probability of 'overexposure' when comparing the pooled with the heterogeneous models. However, when evaluating the factory-specific probability of 'overexposure' or when using the models to provide exposure estimates for epidemiological studies heterogeneity in the variance components should be investigated. © 2005 British Occupational Hygiene Society.

AB - Occupational exposure to chemical agents can vary enormously within- and between-workers, even when carrying out the same jobs. When repeated measurements are available, the variance components can be estimated using random- or mixed-effects models. Pooling the variance components across the fixed effects, in mixed-effects models, reduces the complexity of the models; especially, when there are a large number of fixed effects. The analyses presented in this paper tested the assumptions of homogeneity in the variance components between factories and surveys for inhalable dust exposure in the European carbon black manufacturing industry. In total, 5296 measurements from 1771 workers were available collected during two surveys carried out between 1991 and 1995. Workers were grouped into eight job categories, and for each of these separate mixed-effects models were developed, including factory, survey and in some cases the interaction term as the fixed effects. The likelihood ratio test was used to test the assumptions of homogeneity of the variance components. Statistically significant heterogeneity of the variance components was observed for two of the eight job categories, 'Fitter/Welder' and 'Warehouseman'. The heterogeneity was due mainly to differences in variance between the factories. When estimating the probability of overexposure for all the factories combined, there was little difference between the models with and without heterogeneous variance components for 'Fitters/Welders'. For the 'Warehousemen' the probability of overexposure in the last survey changed marginally from 4% in the pooled model to 6% in the heterogeneous model. Larger differences between the models were observed when estimating the probability of overexposure for individual factories, which was due to over- or underestimation of the variance components in the pooled models. In conclusion, for most job categories pooling of the variance components appears to be justified in this database. In addition, no large differences were found when determining the industry-wide probability of 'overexposure' when comparing the pooled with the heterogeneous models. However, when evaluating the factory-specific probability of 'overexposure' or when using the models to provide exposure estimates for epidemiological studies heterogeneity in the variance components should be investigated. © 2005 British Occupational Hygiene Society.

KW - Exposure modelling

KW - Mixed effects models

KW - Variance compounds

U2 - 10.1093/annhyg/mei041

DO - 10.1093/annhyg/mei041

M3 - Article

VL - 50

SP - 55

EP - 64

JO - Annals of Occupational Hygiene

JF - Annals of Occupational Hygiene

SN - 0003-4878

IS - 1

ER -