Sources and concentrations of indoor nitrogen dioxide in Hamburg (west Germany) and Erfurt (east Germany)

Here we report indoor and outdoor concentrations of NO2 for Erfurt and Hamb urg and assess the contribution of the most important indoor sources (e.g. the presence of gas cooking ranges, smoking) and outdoor sources (traffic e xhaust emissions). We examined the relative contribution of the different s ources of NO2 to the total indoor NO2, levels in Erfurt and Hamburg. NO2 in door concentrations in Hamburg were slightly higher than those in Erfurt (i .e. living room: 15 mu g m(-3) for Erfurt and 17 mu g m-3 for Hamburg). A l inear regression model including the variables, place of residence, season and outdoor NO2 levels, location of the home within the city, housing and o ccupant characteristics accounted for 38% of the NO2 variance. The most imp ortant predictors of indoor NO2 concentrations were gas in cooking followed by other characteristics, such as ventilation or outdoor NO2 level. Reside nces in which gas was used for cooking, or in which occupants smoked, had s ubstantially higher indoor NO2 concentrations (41 or 18% increase, respecti vely). An increase in the outdoor NO2 concentration from the 25th to the 75 th-percentile (17 mu g m(-3)) was associated with a 33% increase in the liv ing room NO2 concentration. Multiple regression analysis for both cities se parately illustrated that use of gas for cooking was the major indoor sourc e of NO,. This variable caused a similar increase in the indoor NO2 levels in each city (43% in Erfurt and 47% in Hamburg). However, outdoor sources o f NO2 (motor vehicle traffic) contributed more to indoor NO2 levels in Hamb urg than in Erfurt. (C) 2000 Elsevier Science B.V. All rights reserved.