varying degrees. Climate change may also affect the depositional environment within
the home resulting in changes to the delivered dose by radon decay products. The
relative concentration of radon to its decay products, and the ability to deliver dose, is
impacted by numerous factors including building ventilation rate, decay product
attachment to aerosols, and particle deposition rate on surfaces (Sun et al. 2010, Sun et
al. 2009, Roos 2002, Nazaroff and Nero 1988). All of these factors could be impacted
by housing as well as behavioral changes driven directly or indirectly by climate change.
For example, the increased use of ceiling fans for cooling would tend to increase
deposition of radon decay products and reduce the delivered radon-related dose to the
lungs (Sun et al. 2010, Sun et al. 2009). Alternatively, increased use of air conditioning,
may reduce the use of ceiling fans, and therefore enhance the delivered dose by radon
progeny.
Increased Air Conditioning and Fan Usage
Increased use of AC, necessitated by increasing temperatures, generally leads to
higher radon concentrations resulting from decreased air exchange rates, particularly
for tightly-sealed homes, and in some cases differences in pressure differentials
between the interior of the home and the soil. As noted above, increases in temperature
will increase the percent of homes with air conditioning as well as the duration of air
conditioning usage. The use of air conditioning contributes to “closed house conditions”
which in turn results in higher radon concentrations. In addition, the use of forced air
HVAC tends to reduce the stratification of radon between floors thus increasing the
radon concentrations on the upper floors where residents spend a greater percentage of
time.
Activity Patterns and Spatial Radon Variation
A study of female Iowa residents (Field et al. 1998) found that only a small
percentage (6.8% of time for two story homes and 3.5% for three story homes) of time
was spent in the basement where the highest radon concentrations generally occur.
However, some Iowa home owners, without air conditioning, reported spending more
time in the basement during warm periods in the summer. The move to cooler areas of
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