How do the indoor size distributions of airborne submicron and ultrafine particles in the absence of significant indoor sources depend on outdoor distributions?

Abstract

Although almost all epidemiological studies of smaller airborne particles only consider outdoor concentrations, people in Central Europe actually spend most of their time indoors. Yet indoor pollutants such as organic gases, allergens and dust are known to play a prominent role, often affecting human health more than outdoor ones. The aim of this study was to ascertain how the indoor particle size distributions of submicron and ultrafine particles correlate with the outdoor concentrations in the absence of significant indoor sources. A typical indoor particle size distribution pattern has one or two modes. In the absence of significant indoor activities such as smoking, cooking etc., outdoor particles were found to be a very important source of indoor particles. The study shows that in the absence of significant indoor sources, the number of indoor concentrations of particles in this size range are clearly lower than the outdoor concentrations. This difference is greater, the higher the number of outdoor concentrations. However, the drop in concentration is not uniform, with the decrease in concentration of smaller particles exceeding that of larger ones. By contrast, the findings with larger particle sizes (diameter > 1 microm) exhibit rather linear concentration decreases. The non-uniform drop in the number of concentrations from outdoors to indoors in our measurements considering smaller particles ( >0.01 microm) is accompanied by a shift of the concentration maxima to larger particle diameters.

Penetration of freeway ultrafine particles into indoor environments

“…Although comparisons of indoor and outdoor particle size distributions have been conducted and modeled to some extent (Franck et al, 2003;Riley, McKone, Lai, & Nazaroff, 2002;Thatcher, Lunden, Revzan, Sextro, & Brown, 2003), ultrafine particle penetration characteristics have not been well examined. In this study, we examine infiltration of ultrafine particles, whereas in a related work (Kuhn et al, 2004) we investigate volatility properties of ultrafine particles near a freeway.…”

“…For example, Long et al (2001) evaluated penetration efficiencies in only suburban neighborhoods. Franck, Herbarth, Wehner, Wiedensohler, and Manjarrez (2003) studied indoor and outdoor ultrafine particle size distributions at one location with an artificial indoor system. Vette et al (2001) measured indoor and outdoor particle size distributions of a single residence at urban background concentrations.…”

Impact of Indoor Houshold Activities on the Size Distribution of Fine Aerosol Number Concentration and Case Specific Calculated Inhaled Dose

“…Furthermore outdoor-to-indoor concentration ratios vary depending on particle size (Franck et al, 2003). Here we present data for indoor and outdoor aerosol number distributions from a street canyon site prior to and during the partial closure of the major road in front of the measurement site.…”

Human exposure against particles: the indoor-outdoor problem

“…The indoor system was installed in an unoccupied apartment on the second floor of the typical European multi family townhouse with the windows and doors closed and without active ventilation (Franck et al [22]). To minimize the effect of indoor sources (Chao et al [23]) during the experiments, the level of human activity was kept low.…”