Occupational exposure during production of wood pellets in Sweden

Sammanfattning: AbstractKatja Hagström (2008): Occupational expsoure during production of wood pellets in Sweden. Örebro Studies in Environmental Science 11. 75 pp. The aims of the studies underlying this thesis were to assess workers’ air exposure to wood dust and various chemicals, and to evaluate the variability in exposure and occupational dermal exposure to resin acids during the production of wood pellets in Sweden. Personal air measurements of wood dust, monoterpenes, resin acids and nitrogen dioxide (as a marker of diesel exhaust), accompanied by area measurements of these substances, VOCs and carbon monoxide, were performed at up to ten plants. Repeated measurements were also performed to evaluate within- and between-worker variability, determinants of exposure, the probability that a worker’s mean exposure exceeded the occupational exposure limit, OEL (overexposure), and the bias in the exposure-response relationship (attenuation).Dermal exposure was measured at the forehead, neck, forearm and hand using a tape-stripping method, in which a strip of adhesive tape is applied to the skin and then removed along with the outermost layer of the skin and chemicals adsorbed to this layer. The workers’ exposure to wood dust was high (mean: 2.4 mg/m3), with 35?42 % of the measurements above the Swedish OEL of 2 mg/m3. The exposure is also classified as unacceptable due to the calculated levels of overexposure. Exposure to resin acids like 7-oxodehydroabietic acid and dehydroabietic acid was identified, which has not been previously observed in the wood industry, with mean sum levels of 2.4 _g/m3. Levels of monoterpenes, nitrogen dioxide, VOCs and carbon monoxide were all below their Swedish OELs. A factor that influenced the level of exposure to wood dust and resin acids was the nature of the work done, notably cleaning operations, like sweeping, which increased the exposure slightly. The attenuation was high for the individual-based model, and at least 12 repeated measurements were needed to yield a bias in the exposureresponse relationship of _10 %. The results also showed that dermal exposure to resin acids occurs in these plants, which has not been shown before, and provided indications of both increased exposure during a work shift and diffusion into the skin. The main conclusion is that wood dust exposure at these levels is likely to have implications for the workers’ health in the long run, and, therefore, it is important to reduce exposure to wood dust in this industry.Keywords: Occupational hygiene, wood dust, resin acids, variance analyses, determinant of exposure, overexposure, dermal exposure.