Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
carried out in 36 randomly chosen households that used biomass as
fuel. It compared concentrations of particles, carbon monoxide,
nitrogen dioxide and formaldehyde inside the home with outdoor
pollution levels.
The mean 24-h concentration of respirable particles was
1400 µg/m 3 , and the estimated levels in areas where cooking and
heating fires were used was 3000-4000 µg/m 3 . Although elevated levels
of carbon dioxide and nitrogen dioxide were found in the homes, the
levels were below those found in previous studies of indoor air
pollution in developing countries. Little correlation was seen between
indoor and outdoor levels, confirming that the source of the excess
levels was combustion.
The excessive levels of particulate, which included a large
concentration of PAHs, suggested that individuals spending a
significant amount of time indoors (e.g., women and small children)
were at greater risk owing to exposure to smoke. Because the levels
observed were homogeneous across the samples, leaving no unexposed
control group, the researchers were unable to reach conclusions about
the effect of the levels on occurrence of acute respiratory
infections.
12.3.6 Assessing ambient pollution impacts indoors
Santiago, Chile, a city of 5.2 million inhabitants in 1997 (40%
of the Chilean population), has chronic high concentrations of certain
air pollutants. For example, in 1995 the Chilean air quality standards
for PM 10 , carbon monoxide and ozone were exceeded on more than
200 days. Annual PM 10 levels surpassed 100 µg/m 3 in the 1990s and
levels of 300 µg/m 3 are common during the winter, especially when an
inversion layer is formed.
In many countries when pollutants in the outdoor air exceed
standards, the population is advised to remain indoors, but if
infiltration occurs and indoor sources are generating pollutants,
indoor air quality (IAQ) might be even worse than outdoors. A study
was designed to evaluate the contribution of outdoor pollution to IAQ
in Santiago and in a small rural town (Curocori). Carbon monoxide,
PM 5 and PAHs were monitored simultaneously indoors and outdoors along
heavy traffic roadways in Curocori and in Santiago. The methodology
used is described in Gil & Adonis (1997).
In downtown Santiago, carbon monoxide concentrations ranged from
1.9 to 73 µg/g outdoors; indoor levels were 0.5-93 µg/g. Although
levels were slightly higher indoors (but not significant, p > 0.05)
than outdoors, changes in outdoor levels (which were always related to
vehicular traffic) simultaneously produced changes in indoor levels. A
typical carbon monoxide profile is shown in Fig. 40 for outdoor and
indoor levels in an office. Outdoor and indoor levels showed a high
correlation ( r = 0.89) with the higher values occurring during the
rush hour.
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