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/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.

Keywords:

• carbon monoxide
• resin acids
• VOCs
• wood dust
• wood pellets

ACKNOWLEDGMENTS

The authors would like to thank all the production plants and workers involved for participating in the study. The authors thank Lena Andersson, Krister Berg, Britt-Marie Isaksson, Carin Norberg, and Mona Svensson for skillful fieldwork and laboratory analysis. Associate Professor Håkan Westberg is gratefully acknowledged for valuable comments during the preparation of the paper.

Financial grants from the Swedish Council for Working Life and Social Research are gratefully acknowledged. The authors acknowledge the Department of Occupational and Environmental Medicine, Örebro University Hospital, and the Department of Occupational and Environmental Medicine, University Hospital of Northern Sweden in Umeå for their financial support.

Notes

^A N was 38 for α -pinene and 39 for nitrogen dioxide; geometric standard deviations: inhalable dust, 2.6; total dust, 2.7; 7OXO, 4.7; DHAA, 3.6; α -pinene, 3.2; nitrogen dioxide, 1.7.

^B Geometric standard deviations: inhalable dust, 3.0; total dust, 2.4; 7OXO, 3.3; DHAA, 3.3; α -pinene, 2.9; nitrogen dioxide, 1.8.

^C 50% or more of the measurements were below the LOQ.

^D Geometric standard deviations: inhalable dust, 2.2; total dust, 2.5; 7OXO, 4.5; DHAA, 3.3; α -pinene, 1.5; nitrogen dioxide, 2.5.

^E N was 66 for α -pinene and 67 for nitrogen dioxide; geometric standard deviations: inhalable dust, 2.6; total dust, 2.6; 7OXO, 4.4; DHAA, 3.4; α -pinene, 3.0; nitrogen dioxide, 1.9.

^A Decane equivalents.

^B N was 20 for α-pinene and 10 for nitrogen dioxide; geometric standard deviations: total dust, 1.2; 7OXO, 2.1; DHAA, 2.1; α-pinene, 1.8; nitrogen dioxide, 1.6; TVOC, 3.1.

^C 50% or more of the measurements were below the LOQ.

^D N was 17 for α-pinene and 11 for nitrogen dioxide; geometric standard deviations: total dust, 6.5; 7OXO, 7.7; DHAA, 4.0; α-pinene, 3.5; nitrogen dioxide, 1.7; TVOC, 2.8.

^E N was 11 for α-pinene and 10 for nitrogen dioxide; geometric standard deviations: total dust, 2.4; 7OXO, 2.7; DHAA, 1.8; α-pinene, 3.1; nitrogen dioxide, 1.8; TVOC, 2.5.

^F N was 6 for nitrogen dioxide; geometric standard deviations: total dust, 3.5; 7OXO, 9.0; DHAA, 3.3; α-pinene, 2.1; nitrogen dioxide, 1.6; TVOC, 2.3.

^G N was 2 for nitrogen dioxide; geometric standard deviations: total dust, 2.4; 7OXO, 1.7; DHAA, 1.6; α-pinene, 2.5; nitrogen dioxide, 2.7; TVOC, 1.9.

^H N was 3 for nitrogen dioxide; geometric standard deviations: total dust, 1.0; 7OXO, 2.3; DHAA, 2.7; α-pinene, 1.2; nitrogen dioxide, 1.5; TVOC, 1.2.

^I N was 68 for α-pinene and 42 for nitrogen dioxide; geometric standard deviations: total dust, 4.0; 7OXO, 5.5; DHAA, 3.1; α-pinene, 5.5; nitrogen dioxide, 1.8; TVOC, 4.2.