Chemistry Reference
In-Depth Information
Indoor air quality has been a public health concern for several decades now.
Indoor air quality is affected both by infiltration of outdoor air in buildings and
indoor sources such as smoking, gas cooking, and use of consumer products [
6
].
Penetration of particles into indoor environments depends on particle size, air
exchange rates, and other factors. Consideration of indoor sources is important
because they may be associated with significant health effects, e.g., environmental
tobacco smoke. Presence of indoor sources may further complicate assessment of the
impact of outdoor air on indoor air. In this chapter we separately describe the impact
of indoor sources and outdoor air on indoor pollution, because health effects of
outdoor and indoor generated particles may differ as their composition differs [
7
].
We focus in this chapter on particles from ambient origin. We first illustrate
differences in outdoor and personal exposure using data on real-time particle number
concentrations (PNC) from a recent study in Augsburg, Germany. We then present a
model of indoor PM concentrations, illustrating the factors that affect indoor air
quality. We summarize empirical studies that have assessed indoor-outdoor
relationships for particle mass, particle number, and specific components of particu-
late matter. The focus is on European studies, but we included key studies from
outside Europe as well. We conclude by comparing the strength of indoor-outdoor
relationships of various particle fractions and components.
2 Example of Outdoor and Indoor Exposure: Augsburg Study
Within the framework of a study conducted in Augsburg, Germany, personal
exposure to UFP has been measured during 2011. The study participants followed
three different scenarios: (A) commute by car to their home, spend the morning
there, and commute back by car; (B) commute by public transport to their home,
spend the morning there, and commute back by public transport; and (C) walk to the
city center, spend about 4-5 h there with at least 2 h outside, and walk back. All
trips started and ended at the study center, located near the central railway station in
the center of Augsburg. The measurements were done by each of the participants on
the same day of the week over 3 consecutive weeks in winter, spring, and summer.
In all three scenarios, the subjects kept a detailed diary and their whereabouts were
recorded with geographic positioning systems (GPS).
In Fig.
1
the average time series of personal and ambient PNC for scenarios A and
B are presented. Between 7:00 and 8:30 as well as after 13.15 the majority of
participants were outdoors traveling between the study center and their home. During
this time the difference between the personal and ambient levels of PNC was rather
small. In contrast large differences between personal and ambient levels of PNC were
observed when participants were in their homes or other indoor microenvironments.
In indoor microenvironments the personal exposure to PNC exceeded significantly
ambient PNC levels. Domestic activities such as cooking or lightning candles were
found to greatly increase personal indoor exposure. Especially cooking (between
12:00 and 13:00) strongly contributed to increases in personal PNC.
