Predictors of Monoterpene Exposure in the Danish Furniture Industry

Abstract

Individuals who work with pine in the furniture industry may be exposed to monoterpenes, the most abundant of which are α-pinene, β-pinene, and Δ(3)-carene. Monoterpenes are suspected to cause dermatitis and to harm the respiratory system. An understanding of the predictors of monoterpene exposure is therefore important in preventing these adverse effects. These predictors may include general characteristics of the work environment and specific work operations. We sought to assess the extent to which workers are exposed to monoterpenes and to identify possible predictors of monoterpene exposure in the pine furniture industry in Denmark. Passive measurements of the levels of selected monoterpenes (α-pinene, β-pinene, and Δ(3)-carene) were performed on 161 subjects from 17 pine furniture factories in Viborg County, Denmark; one sample was acquired from each worker. Additionally, wood dust samples were collected from 145 workers. Data on potential predictors of exposure were acquired over the course of the day on which the exposure measurements were recorded and could be assigned to one of four hierarchic ordered levels: worker, machine, department, and factory. In addition to univariate analyses, a mixed model was used to account for imbalances within the data and random variation with each of the hierarchically ordered levels. The geometric mean (GM) monoterpene content observed over the 161 measurements was 7.8 mg m(-3) [geometric standard deviation (GSD): 2.4]; the GM wood dust level over 145 measurements was 0.58 mg m(-3) (GSD: 1.49). None of the measured samples exceeded the occupational exposure limit for terpenes in Denmark (25 ppm, 150 mg m(-3)). In the univariate analyses, half of the predictors tested were found to be significant; the multivariate model indicated that only three of the potential predictors were significant. These were the recirculation of air in rooms used for the processing of wood (a factory level predictor), the presence of a supplementary cold air intake (departmental level), and the operation of a glue press (machine level). However, only one factory of the 17 examined used a supplementary cold air intake, and while very high monoterpene levels were observed there, this may be due to factors other than the supplementary intake. In contrast to the situation with wood dust, we found that the bulk of the variation in the data (65%) was attributable to variability on the factory level, with comparatively little being due to the departmental (16%) and machine (0.5%) levels. The fixed terms in the model accounted for 31.8% of the total variance. The predictors of monoterpenes are not the same as those for wood dust exposure; this has implications for the implementation of preventative measures in factories. In order to decrease monoterpene exposure, efforts should be focused on minimizing the recirculation of air in rooms used for woodworking and on increasing awareness of the importance of effective ventilation and enclosure when operating a glue press.