Civil Engineering Reference
In-Depth Information
Fig. 13.5
CO
2
emissions as a function of average trip speed.
Source
Reference [
29
], p 166, Fig. 3
However, impairment of cognitive skills, vision, and work capacity may occur with
elevated CO levels in healthy individuals [
32
].
2.
Nitrogen Oxides
(
NO
x
)
The group of gases composed of only nitrogen and oxygen, including nitrogen
dioxide (NO
2
) and nitric oxide (NO), which is rapidly converted to nitrogen dioxide
(NO
2
) after emission from vehicles and other sources. Nitrogen Oxides (NO
x
) are
gases produced by fuel combustion. Exposures have been associated with lung
irritation, emergency department visits and hospital admissions for respiratory
conditions. Nitrogen oxides contribute to the formation of ozone.
3.
Volatile Organic Compounds
(
VOC
)
VOCs include a variety of chemicals, some of which may have short- and long-term
adverse health effects. VOCs are a major contributor to Ozone.
Ozone at ground-level is created by a chemical reaction between oxides of
nitrogen (NO
x
) and volatile organic compounds (VOC) in the presence of sunlight.
Ground-level ozone is the primary constituent of smog. Sunlight and hot weather
cause ground-level ozone to form in harmful concentrations in the air. As a result, it
is known as a
summertime air pollutant
.
4.
Particulate Matter
(
PM
)
Particle pollution or
PM
, is a complex mixture of extremely small solid particles
and mists. Particulate pollution is made up of a number of components, including
acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust
particles. Smaller particles of 10 micrometers in diameter or smaller (
PM10
,
PM2.5
, and
UFP
are shown in Fig.
13.6
[
33
]) more easily bypass the natural
defenses of the body, and are more easily inhaled deep into lung tissue, where they
can cause health problems [
30
].
