Residential stability, penetration of outdoor PM and other pollutants indoors, and indoor sources were also not explicitly accounted for.
Next, in order to estimate PM2.5 attributable to solid fuel use, or gas for cooking, it was necessary to adjust these average concentrations of PM2.5 indoors for the effect of other sources, i.e. penetration indoors of outdoor air pollution, and all other indoor sources.
In addition, air pollutant concentrations can be much higher indoors than outdoors for pollutants with predominate indoor sources (e.g. environmental tobacco smoke) and vice versa for pollutants with predominate outdoor sources (e.g. ozone) [ 11, 12].
In general, the largest contribution to the time weighted exposures results from exposures while indoors, which are influenced by the outside air, indoor sources, and attached garages.
The concentration values of NO2 were always lower indoors than outdoors, which indicates that there were no indoor sources.
She stressed, however, that the dangers of peeling paint indoors, where small children spend most of their time, dwarf those from outdoor sources, and that eliminating indoor sources must therefore be the city's priority.
Despite the fact that 4- t-butylphenol and o-phenylphenol are commonly detected indoors, their sources are poorly characterized and 4- t-butylphenol is not identified as an ingredient of commercial products.
Alternatively, observed variation in estimated PM2.5 health effects may result from seasonal or regional differences in human activity patterns, meteorological conditions, penetration of PM2.5 indoors, PM2.5 sources, or other confounders (Peng et al. 2005).
Whether a pollutant has an outdoor or an indoor source, most exposure to the pollutant occurs indoors.
Vehicle exhaust is the main source of outdoor UFPs, which can penetrate indoors where additional sources include environmental tobacco smoke, cooking, burning of candles, and chemical reactions (Abt et al. 2000; Dennekamp et al. 2001; Levy et al. 2000; Long et al. 2000; Ozkaynak et al. 1996).
