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.

Keywords:

• Asthma
• lung function
• occupational exposure
• respiratory symptoms
• rhinitis
• wood dust

Acknowledgements

We would like to thank all workers participating in this study and the production plants for their co-operation. We would also like to acknowledge the work of Lennart Andersson, Sara Axelsson, Krister Berg, Rigmor Fredriksson, Britt-Marie Isaksson, and Birgitta Linder during the field phase and in the laboratory.

Disclosure statement

The authors report no conflicts of interest.

Funding

Financial support was received from the Swedish Energy Agency.

Notes on contributors

Dr Håkan Löfstedt, MD, PhD, is a Consultant Physician, Department of Occupational and Environmental Medicine, Faculty of Medicine and Health Örebro University, Örebro.

Dr Katja Hagström, PhD, is an Occupational Hygienist, Department of Occupational and Environmental Medicine, Faculty of Medicine and Health Örebro University, Örebro.

Ing-Liss Bryngelsson is a Statistician, Department of Occupational and Environmental Medicine, Faculty of Medicine and Health Örebro University, Örebro.

Associate Professor Mats Holmström, MD, PhD, is a Consultant, Division of Ear, Nose and Throat Diseases, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm.

Professor Anna Rask-Andersen, MD, PhD, is a Consultant Physician, Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden.