Effect of outdoor generated pollutants on indoor air quality and health

The significant public health effects of ambient air pollution are mostly caused by exposures in indoor environments, where we spend over 90 % of our time. Indoor concentrations of air pollutants are in general higher than and often also independent of the outdoor air concentrations. In average, urban outdoor air contributes significantly to indoor concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), benzene and some other aromatic VOC:s, ozone (O3), and fine particulate matter (PM2.5), but not to, e.g., most VOCs and carbonyls or to the highest concentrations of CO and PM. Indoor concentrations of pollutants of outdoor or ambient origin, however are at most equal to, (e.g. CO) and for reactive (e.g. O3 and ultrafine particles) significantly lower than the outdoor air levels. PM2.5 is the urban air pollution which causes the biggest mortality, over 300 000 excess deaths annually in Europe. To the vulnerable population groups the current building envelope, ventilation and air conditioning technologies can provide effective and targeted protection against the risks of outdoor air fine PM and O3.