The importance of indoor air pollution to personal exposures in industrialised societies.

Indoor concentrations of a variety of particulate matter and gaseous compounds often exceed outdoor concentrations. We should examine exposures to air pollutants within the important built environments or perhaps on a personal basis. The development of reliable biological markers is still an area of active research. Instruments passively monitoring NO2 exposures over timeperiods ranging from hours to days have been used in several studies in theU.S.