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

Abstract

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/m3. 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 microg/m3. 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.

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

“…It is, however, better to measure the inhalable fraction since wood dust particle is mainly composed of particles with a median aerodynamic diameter >10 μm (35). Calibration studies have shown that inhalable wood dust concentrations are on average 1.6 to 4 times higher than total wood dust concentrations (1,35–38). The new OEL in Sweden for wood dust is today set to 2 mg/m 3 , indicating that even more of the measurements would have been above today’s OEL if inhalable fraction had been measured.…”

“…Secondly, the industry was relatively new when the study was performed. But since levels are high compared with other wood-working industries, it is possible that health effects (1) can occur after periods of longer exposure. It is therefore important to continue monitoring the industry.…”

“…Personal wood dust exposure levels at wood pellet production plants have been noted to be between <0.60 and 8.0 mg/m 3 as inhalable dust and levels of monoterpene (only α-pinene) were <0.28 to 25 mg/m 3 (1). Standard methods for measuring dust describe average levels of dust in the air during a shift, but no peaks in exposure during the working day.…”

“…Monoterpenes are irritating to skin, eyes, and mucous membranes, and can cause both non-allergic and allergic contact dermatitis (1,19), and consequently woodworkers have a higher risk of developing hand eczema (20). The most abundant monoterpenes in softwood are α-pinene, β-pinene, and Δ 3 -carene (21).…”

Wood Dust Sampling: Field Evaluation of Personal Samplers When Large Particles Are Present

“…The ratios IOM/CFC, IOM/Button, and CFC/Button were 2.16, 3.43, 1.59, respectively, with IOM/CFC and CFC/Button therefore significantly different from the earlier measurements of Harper and Muller (2002) where wall deposits had not been included. Hagström et al (2008) reported that the ratio between IOM and 25-mm open-face cassette (filter-only) ranged from 0.67 to 17 with an average of 3.2 at wood pellets industries. Kauffer et al (2010) reported ratios between selected aerosol samplers including ACCU-CAP™, Button, CIP10-I, and IOM samplers and the CFC (filter-only) in wood product industries and the ratios were 1.68, 1.46, 1.84, and 2.00, respectively.…”