Air Quality Guidelines Global Update 2005 - World Health ...

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AIR QUALITY GUIDELINES
economic development. For example, many eastern European countries use solid
fuels for heating, but with much more sophisticated solid fuel energy technologies
than are available in developing countries. Thus, residents can cook and/or heat
with solid fuels without creating large indoor sources of exposure. In contrast,
people living in poorer households in developing countries, particularly those
living in less permanent structures, generally have much less precise control over
their household ventilation rates. Their households are likely to be very open in
hot weather and as tightly sealed as possible in the winter. Seasonal variations in
household ventilation are therefore likely to be substantial.
The flux of air pollutants penetrating the house increases with the ventilation
rate. The ventilation rate of houses depends on the building characteristics,
weather conditions and the (ventilation) behaviour of the occupants. In very
well-insulated houses, the ventilation rate is low and thus the amount of air pollution
from outside will be lower. In very well-insulated houses, however, pollutants
produced indoors accumulate more and moisture problems may occur.
The ventilation rate will be higher when it is windier outside, when the temperature
difference between indoor and outdoor air is higher, and when the windows
are open for a longer period. In a study in Baltimore (33), for example, personal
exposure to fine PM of outdoor origin in the summer was found to be almost
twice as high for people who had had their windows open for more than 72% of
the time compared with those who had hardly opened their windows (