ORIGINAL ARTICLE

Cross-shift changes in FEV₁ in relation to wood dust exposure: the implications of different exposure assessment methods

V Schlünssen¹, T Sigsgaard¹, I Schaumburg² and H Kromhout³

¹ Department of Environmental and Occupational Medicine, University of Aarhus, DK-8000 Aarhus C, Denmark
² Department of Occupational and Environmental Medicine, Skive Hospital, Resenvej 25, DK-7800 Skive, Denmark
³ Institute for Risk Assessment Sciences (IRAS), Division of Environmental and Occupational Health, Utrecht University, NL 3512 Utrecht, Netherlands

Correspondence to:
Correspondence to:
Dr V Schlünssen
Department of Environmental and Occupational Medicine, University of Aarhus, DK-8000 Aarhus C, Denmark; vivi_schlunssen{at}dadlnet.dk

Background: Exposure-response analyses in occupational studies rely on the ability to distinguish workers with regard to exposures of interest.

Aims: To evaluate different estimates of current average exposure in an exposure-response analysis on dust exposure and cross-shift decline in FEV₁ among woodworkers.

Methods: Personal dust samples (n = 2181) as well as data on lung function parameters were available for 1560 woodworkers from 54 furniture industries. The exposure to wood dust for each worker was calculated in eight different ways using individual measurements, group based exposure estimates, a weighted estimate of individual and group based exposure estimates, and predicted values from mixed models. Exposure-response relations on cross-shift changes in FEV₁ and exposure estimates were explored.

Results: A positive exposure-response relation between average dust exposure and cross-shift FEV₁ was shown for non-smokers only and appeared to be most pronounced among pine workers. In general, the highest slope and standard error (SE) was revealed for grouping by a combination of task and factory size, the lowest slope and SE was revealed for estimates based on individual measurements, with the weighted estimate and the predicted values in between. Grouping by quintiles of average exposure for task and factory combinations revealed low slopes and high SE, despite a high contrast.

Conclusion: For non-smokers, average dust exposure and cross-shift FEV₁ were associated in an exposure dependent manner, especially among pine workers. This study confirms the consequences of using different exposure assessment strategies studying exposure-response relations. It is possible to optimise exposure assessment combining information from individual and group based exposure estimates, for instance by applying predicted values from mixed effects models.

Abbreviations: AM, arithmetic mean; GM, geometric mean; _BWs_y², between-workers variance; _BGS_y², between-group variance; _WGS_y², within-group variance; GSD, geometric standard deviation; FEV₁, forced vital capacity in one second; SD, standard deviation; SE, standard error; _WWs_g², within-worker variance in each group; _BWs_g², between-workers variance in each group; j, mean number of repeated samples in each group; Bg, weighting factor = (_WWs_g² x (j^–1)) / (_BWs_g² + _WWgs² x (j^–1))

Keywords: exposure assessment; wood dust; lung function

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