Katja Hagström

Exposure to Wood Dust, Resin Acids, and Volatile Organic Compounds During Production of Wood Pellets

The main aim of this study was to investigate exposure to airborne substances that are potentially harmful to health during the production of wood pellets, including wood dust, monoterpenes, and resin acids, and as an indicator of diesel exhaust nitrogen dioxide. In addition, area measurements were taken to assess background exposure levels of these substances, volatile organic compounds (VOCs), and carbon monoxide. Measurements were taken at four wood pellet production plants from May 2004 to April 2005. Forty-four workers participated in the study, and a total of 68 personal measurements were taken to determine personal exposure to wood dust (inhalable and total dust), resin acids, monoterpenes, and nitrogen dioxide. In addition, 42 measurements of nitrogen dioxide and 71 measurements of total dust, resin acids, monoterpenes, VOCs, and carbon monoxide were taken to quantify their indoor area concentrations. Personal exposure levels to wood dust were high, and a third of the measured levels of inhalable dust exceeded the Swedish occupational exposure limit (OEL) of 2 mg/m 3 . Parallel measurements of inhalable and total dust indicated that the former were, on average, 3.2 times higher than the latter. The data indicate that workers at the plants are exposed to significant amounts of the resin acid 7-oxodehydroabietic acid in the air, an observation that has not been recorded previously at wood processing and handling plants. The study also found evidence of exposure to dehydroabietic acid, and exposure levels for resin acids approached 74% of the British OEL for colophony, set at 50 μg/m 3 . Personal exposure levels to monoterpenes and nitrogen dioxide were low. Area sampling measurements indicated that aldehydes and terpenes were the most abundant VOCs, suggesting that measuring personal exposure to aldehydes might be of interest. Carbon monoxide levels were under the detection limit in all area measurements. High wood dust exposure levels are likely to have implications for worker health; therefore, it is important to reduce exposure to wood dust in this industry.

Tape-stripping as a method for measuring dermal exposure to resin acids during wood pellet production

The purpose of this study was to develop a sensitive and specific method for quantifying dermal exposure to the resin acids 7-oxodehydroabietic acid (7-OXO), dehydroabietic acid (DHAA), abietic acid (AA), and pimaric acid (PA). In addition the method was evaluated in occupational settings during production of wood pellets. Tape-strips were spiked with the substances to evaluate the recovery of the acids from the tape. The removal efficiency of the tape was assessed by tape-stripping a specified area on a glass plate spiked with resin acids. The recovery of the acids from human skin in vivo was evaluated by applying acids in methanol onto the skin of volunteers. Occupational dermal exposure to the resin acids was assessed by tape-stripping the skin of workers involved in the production of wood pellets. The resin acids were analyzed by liquid chromatography mass spectrometry (LC-MS). The limit of detection was 15 pg (7-OXO), 150 pg (DHAA), 285 pg (AA) and 471 pg (PA) per injection. The recovery from spiked tapes was in general 100%. The removal efficiency of the tape was 48-101%. Recovery tests from human skin in vivo showed a mean recovery of 27%. Quantifiable amounts of resin acids were observed on four different skin areas with an increase in exposure during a work shift. This study shows that occupational dermal exposure to resin acids can be assessed by tape-stripping and quantified by LC-MS.

Predictors of Monoterpene Exposure in the Danish Furniture Industry

OBJECTIVES 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.

Respiratory symptoms and lung function in relation to wood dust and monoterpene exposure in the wood pellet industry

Abstract Introduction: Wood pellets are used as a source of renewable energy for heating purposes. Common exposures are wood dust and monoterpenes, which are known to be hazardous for the airways. The purpose of this study was to study the effect of occupational exposure on respiratory health in wood pellet workers. Materials and methods: Thirty-nine men working with wood pellet production at six plants were investigated with a questionnaire, medical examination, allergy screening, spirometry, and nasal peak expiratory flow (nasal PEF). Exposure to wood dust and monoterpenes was measured. Results: The wood pellet workers reported a higher frequency of nasal symptoms, dry cough, and asthma medication compared to controls from the general population. There were no differences in nasal PEF between work and leisure time. A lower lung function than expected (vital capacity [VC], 95%; forced vital capacity in 1 second [FEV1], 96% of predicted) was noted, but no changes were noted during shifts. There was no correlation between lung function and years working in pellet production. Personal measurements of wood dust at work showed high concentrations (0.16–19 mg/m3), and exposure peaks when performing certain work tasks. Levels of monoterpenes were low (0.64–28 mg/m3). There was no association between exposure and acute lung function effects. Conclusions: In this study of wood pellet workers, high levels of wood dust were observed, and that may have influenced the airways negatively as the study group reported upper airway symptoms and dry cough more frequently than expected. The wood pellet workers had both a lower VC and FEV1 than expected. No cross-shift changes were found.

Temporal Trend in Wood Dust Exposure During the Production of Wood Pellets

Objective Wood dust data collected in the production of wood pellets during 2001 to 2013 were evaluated to study a temporal trend in inhalation exposure. Methods A linear mixed effects model of natural ln-transformed data was used to express the relative annual difference in inhalation wood dust exposure. Results There was an annual decrease of -20.5% of the geometric mean wood dust exposure during 2001 until 2013. The results were based on 617 inhalable dust samples collected at 14 different production units. The exposure to wood dust at the industrial premises investigated has decreased from a relatively high level of 6.4 mg m-3 in 2001 to 1.0 mg-3 in 2013. The Swedish Occupational Exposure Limit (SOEL) of 2 mg m-3 may still be exceeded. Conclusion Analysis of the temporal trend in soft wood production units revealed declines in exposure of 20.5% per annum. It is important that precautions are taken to protect workers from a hazardous exposure to wood dust at the premises as the SOEL of 2 mg m-3 at some occasions is still exceeded. Additional measurements of wood dust exposure should be carried out on a regular basis in wood pellet production units in Sweden as well in other countries.