Indoor ozone exposure and ozone mortality coefficient.
Increases in outdoor ozone concentration have been associated with
short-term mortality. However, differences have been reported for the
increase in short-term mortality associated with a given increase in
ozone concentration (ozone mortality coefficient) between cities.
Although ozone concentrations are monitored at central outdoor
locations, a large fraction of total ozone exposure occurs indoors. Chen
et al (p. 235) studied whether variation in ozone mortality coefficients
among U.S. cities might be partly explained by differences in total
ozone exposure (from both outdoor and indoor exposures) resulting from
the same outdoor ozone concentration. They used average annual air
change rates (the overall rate at Which indoor air is replaced with
outdoor air) to estimate the change in total ozone exposure per unit
change in outdoor ozone exposure (ozone exposure coefficient) for 18
cities that had been included in the National Morbidity and
Mortality' Air Pollution Study (NMMAPS). Associations between both
parameters and ozone mortality coefficients were compared vi h existing
data in the literature. For the 8 NMMAPS cities, the association between
ozone mortality coefficients and ozone exposure coefficients was highly
significant. Similar associations were observed for another 72 NMMAPS
cities. The authors conclude that differences in ozone mortality
coefficients among cities appear to partially reflect differences in
total ozone exposure that result from differences in air change rates
and time spent outdoors.