The Importance of Temporal Variations of Chemicals and Mold Spores in (Indoor) Air for Health Related Risk Assessment

Abstract

P-306 Introduction and Problem: Indoor air contamination with volatile organic compounds (VOC) and mould experiences an increasing interest with respect to their relevance to health. To assess adverse health effects, epidemiological studies combine the health outcome of individuals with their concomitant exposure. This exposure is observed, for example, during the current month of investigation, whereas the whole study is carried out over a period of e.g. one year. The measured exposure is representative for the measurement period, but health effects might also be the result of long-term exposure. To consider such effects, additional information about the spatiotemporal distribution of exposure is necessary. Method: For that reason the aim is to elucidate these spatial and temporal variations of exposure and to apply it on the risk assessment. For both exposures VOC and mould in a direct comparison of measurements taken during different months the season has to be considered. To do this two ways are possible. One way of doing this might be the introduction of seasonally dependent reference values. Another way is to adjust the measurements, for which purpose a harmonic function has to be fitted to monthly means/medians of concentrations. Results: The findings lead to a seasonal model, fitted to the measurements. Based on the model a procedure for seasonal adjustment was developed, which enabled the roughly estimate of the annual peak concentration utilizing one monthly observation. Combining the temporal patterns of VOCs with the results for the contamination of indoor air with mould, there is strong seasonality of indoor air quality in apartments. Considering spores, two groups were found differing in their spatiotemporal distribution. This behavior can be explained by the predominant origin and growing conditions, indoor-relevant and outdoor-relevant genera. The outdoor-relevant group shows a significant annual cycle. Highest concentrations occurred during the summer months and were about 100 times the winter burden. Regarding to VOC highest concentrations occur during the winter months to approximately 3 times higher than the summer burden. Conclusion: These investigations lead to the conclusion that in an assessment of indoor air quality the season when sampling occurs must be taken into consideration. As an adjustment of the seasonal cycle does not remove the trend over several years, seasonally adjusting a data set will not mask the general trend; the proposed adjustment procedure is therefore applicable to long-term studies.