Toxikologische Charakterisierung von Feinstäuben aus der Holzverbrennung

In recent years the term “particulate matter” (PM) has increasingly gained public as well as scientific interest. Before industrialization, mainly natural sources, such as volcanoes, erosion, sea salt aerosols or forest fires were the main sources of particulate matter, whereas nowadays anthropogenic sources, such as traffic, industry and combustion processes are the principle source of PM. Due to longer retention times in the atmosphere as well as contamination with various pollutants these emissions are of a high toxicological relevance. Smog catastrophes, such as the Great London Smog in 1952 made people aware of the adverse health effects of such emissions. Moreover, numerous epidemiological studies have demonstrated a correlation between particulate matter exposure and adverse health effects in humans. Subsequently, many countries adopted air quality policies and laws with the aim of decreasing air pollution and the risk for human health. Besides traffic, which is one of the main sources of emissions, the toxic potential of particulate matter derived from biomass combustion is increasingly being discussed. Due to diminishing supplies of fossil fuels, biomass combustion has become an important alternative energy source. Hence, PM emissions from the combustion of wood are increasing and are assumed to be of similar toxicological relevance as PM stemming from traffic. Consequently, the 1st BImSchV (Federal Immission Protection Ordinance) was introduced in Germany in 2010, which provides limit values for particulate matter emissions of small scale combustion appliances. This regulation mainly applies for new furnaces as well as older appliances, which should be technically reconstructed to meet the legislative specifications. Against this background a cooperative project was designed to investigate the emissions of small scale wood combustion appliances and potential mitigations. The present study, as a part of this cooperative project, assessed the toxicological characterization of wood combustion particulate matter. It was the aim of this study to investigate the toxic potential of PM of different qualities (efficient/complete combustion and incomplete combustion) via in vitro test systems (cell culture). The work featured a strong focus on the initial characterization of the PM samples in the submersed exposure culture and emphasis was laid on specific pollutants, namely the polycyclic aromatic hydrocarbons (PAH), which are typical by-products of many combustion processes. Some PAHs are known carcinogens and are thus of relevance for human health. In order to characterize the composition and morphology as well as aggregation potential and particle size distribution of the PM samples in cell culture medium, a range of different methods was applied. Subsequently, the PM samples and their extracts were assessed in different reporter gene assays (Ah receptor-, estrogen- and androgen-receptor interaction) and a cell transformation assay to investigate the PAH bioavailability as well as a possible tumor initiating potential. The in vitro experimental data as well as the data from the particle characterization experiments suggested a correlation between the physico-chemical properties of the different PM samples and the bioavailability of the PAHs. PAH bioavailability could be demonstrated for all PM samples. Interestingly, there seemed to be a higher or similar bioavailability of PAHs in samples from the more efficient combustion, even though these samples generally displayed lower PAH contamination. Further spiking experiments provided insights into the differential PAH bioavailability that was observed in the reporter gene assay via Ah receptor activation. While an estrogen- or androgen receptor activation could not be confirmed with the corresponding bioassays, a tumor initiating potential for some of the samples could be detected.In conclusion, it could be shown that the characterization of PM samples is an important prerequisite for subsequent biological testing and the interpretation of the in vitro experimental data. As observed in this study, the physico-chemical properties strongly influenced the bioavailability of certain contaminants, e.g. PAHs. Hence, a risk assessment based on mere chemical analyses alone is not sufficient for complex mixtures, such as particulate matter. The obtained results show that further in-depth investigation in this field is needed and moreover demonstrated the applicability of in vitro test systems for answering certain questions for use in a rapid and reliable screening of wood combustion PM against the background of fast technical progress