Assessment of the sensitivity of the relation between current exposure to carbon black and lung function parameters when using different grouping schemes

Background Equations using variance components in exposure data to predict attenuation and standard error of exposure-response slopes have been publis hed recently. However to date, no comparisons have been made between result s of applying these equations to a real data set with the exposure-response relations estimated directly. Methods Data on lung function parameters and personal inhalable and respira ble dust exposure levels from the European carbon black respiratory healthy study were used The predicted attenuation and standard error of the relati on between current inhalable and respirable dust levels and lung function p arameters (FVC and FEV1) were calculated for various exposure grouping sche mes. These results were correlated with the observed exposure-response rela tions. Workers were grouped by Job Category, the combination of factory and Job Category and five a posteriori created Exposure Groups. In addition th e individual approach was also used as exposure data were available for eac h worker. Results The rank orders of the coefficients from the regression analyses us ing the different grouping schemes were similar to those predicted by the e quations although the differences were larger than predicted. When using in halable dust exposure, the predicted standard errors of the exposure-respon se slopes were slightly lower than those estimated directly;for respirable dust the predicted standard errors were about a factor two to three smaller than those from the regression analyses. When considering FVC, the predict ed exposure-response relations were all statistically significant, whilst t he observed relation was only significant when using the five a posteriori Exposure Groups. When reviewing the relations between dust exposure and lev el of FEV1, all relations were statistically significant with the exception of the (observed) relation between respirable dust and FEV1, when the indi vidual approach was used. Conclusions Using different grouping schemes for estimating exposure can ha ve large effects on the slope and standard error of the exposure-response r elation. it is, therefore, important that the effect of the different growi ng schemes on the level and precision of the exposure-response slope be est imated. Despite violation of most of the assumptions when applying the equa tions to predict attenuation and rite standard error of the exposure-respon se slope, the similarities in predicted and observed exposure-response rela tions and standard errors are indicative of the robustness of these equatio ns. Therefore, the equations appear to be a useful tool in establishing the most efficient way of utilizing exposure measurements. Am. J. Ind. Med. 36 :548-556, 1999. (C) 1999 Wiley-Liss, Inc.