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Health effects assessment of exposure to particles from wood smoke 9 Gaps of knowledge
As can be seen from the previous chapters in this report, limited data are available for a more precise health impact assessment of wood smoke PM. In this chapter, the most essential data gaps are indicated. 9.1 Characterisation of wood smoke particlesThe information on detailed physical and chemical characterisations of the particle emissions from different combustion technologies, including wood combustion, is still limited. In addition, any specific particle properties or components responsible for the adverse health effects related to the particle emissions have not yet been identified; however, the importance of characterising particle properties other than mass concentration, like chemical composition, particle size, and number concentration, has been emphasised. Furthermore, there is a lack of knowledge on particle properties, including health aspects, in relation to the different phases of the combustion cycle and type of combustion device. Thus, more data are needed in order to provide a more precise characterisation of wood smoke PM in Denmark as well as a more precise characterisation of the wood smoke composition in general. 9.2 Exposure assessmentAt present, the population exposure to wood smoke PM in Denmark cannot be estimated precisely as only few measurements have been conducted in selected residential areas with different kinds of heating. Thus, more studies are needed in order to provide a more precise assessment of the population exposure to wood smoke PM in Denmark. This pertain both to a better description of exposure in areas where wood burning is dominant as well as exposure in areas more distant from the source. In such studies, measurements of chemical markers for wood smoke such as e.g., levoglucosan could be relevant in order to evaluate the contribution of wood smoke PM to the ambient general PM. Since people spend a majority of their time indoors, it is important to investigate indoor exposure to wood smoke particles in order to evaluate the integrated exposure from both in-house combustion devices and background levels. 9.3 Hazard assessment / risk characterisationA number of epidemiological studies, which have evaluated adverse health effects from ambient air pollution in relation to residential wood combustion, indicate an increased risk of experiencing adverse health effects in the respiratory tract from exposure to wood smoke PM. However, no epidemiological data on wood smoke exposure in relation to cardio-vascular diseases, or overall mortality are available. In addition, the available epidemiological studies do not provide a sufficient basis in order to evaluate the lung cancer risk due to exposure to wood smoke PM. Precise characterisations of specific dose-response relationships for the adverse health effects associated with exposure to wood smoke PM cannot be performed based on the available epidemiological studies predominantly because of the uncertainties about the actual contribution of wood smoke PM to ambient PM in general. Similarly, whether differences exist for dose-response relationships for wood smoke PM compared to the known dose-response relationships for ambient PM in general cannot be assessed. Thus, more data are needed in order to provide a more precise assessment of long-term exposure of wood smoke exposure on morbidity and mortality, including a more precise characterisation of specific dose-response relationships for the various adverse health effects. It might thus be relevant to investigate the relationship between exposure to wood smoke PM in a specific residential area with many wood stoves and the health outcomes in the population living in this specific residential area. 9.4 Mode of actionThe underlying mechanisms of particle toxicity are not fully understood; however, the understanding of effects on the respiratory and cardiovascular system and on tumour development has improved during the last years. Thus, there is still a need for further experimental studies aiming at understanding the effects and underlying mechanisms of wood smoke exposure in order to assess human health risks. 9.5 RecommendationsMore information is needed for a more precise health impact assessment of wood smoke PM in Denmark, particularly in relation to assess the exposure to wood smoke PM in the general population as well as to assess the long-term exposure of wood smoke PM on morbidity and mortality including a characterisation of the specific dose-response relationships for the various adverse health effects related to wood smoke PM exposure. It might thus be recommended to conduct one or more studies in a selected residential area with many wood stoves aiming at:
In addition, there is still a need for further experimental studies aiming at:
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