lead to health effects and the production of tropospheric ozone, its main source in many locations
is emissions from vehicles, and catalytic converters are used to minimize these emissions.
Other high-temperature combustion processes
also contribute. Emissions of NO x can indirectly
lead to acid deposition (or “acid rain”).
Combustion of fossil fuels containing sulfur
leads to emissions of SO 2 . Refining and production
of fuels and minerals (e.g., lead smelting, aluminum refining) also emits substantial amounts of
SO 2 . SO 2 negatively impacts human health, contributes to acid deposition, and can promote aerosol
formation and growth. Sulfate formed from SO 2 is
a major contributor to aerosol mass in some
regions. Aerosol produced through historic emissions of SO 2 is believed to have caused a negative
climate forcing that suppressed temperature rise in
the second half of the last century. Using fuels that
contain only trace amounts of sulfur, such as natural gas, or that contain less sulfur, such as lowsulfur coal, results in less emission of SO 2 . There
are also downstream options such as flue-gas
desulphurization [5].
Tropospheric ozone (O 3 ) is a major irritant to
human health and vegetation. O 3 is a secondary
pollutant, meaning that O 3 is rarely directly emitted
from point sources but is formed via chemical
reactions involving other air pollutants such as
NO x and VOCs.
There is a multitude of volatile organic carbon
(VOC)
species
both
biogenic
and
anthropogenic. Many have been identified as particular hazards, and they are discussed in the section below on HAPs. Some anthropogenic VOCs
have been associated with causing cancer in
humans [9]. Anthropogenic sources include vehicle emissions, petroleum product manufacture
and use, biomass burning, landfill gas, sewage
treatment [10], and off-gassing from building
materials. Biogenic VOCs can be the result of
the natural metabolic processes of life forms [11]
and natural decomposition. VOCs play a crucial
role in the formation of tropospheric ozone [12].
PM (particulate matter) is a term that covers a
wide variety of liquid and solid particles
suspended in the atmosphere. PM is classified
by size (according to aerodynamic diameter) and
various chemical species of PM exist, even
within single particles. Size classifications are
typically given as PM 10 (particles with aerodynamic diameters less than 10 mm), PM 2.5
(particles with aerodynamic diameters less than
2.5 mm), and Ultrafine Particles (UFP, particles
with aerodynamic diameters less than 0.1 mm).
Particulate species include sulfate (SO 4
2À and
containing particles), nitrate (NO 3
À
), ammonium (NH 4
+ ), Organic Matter (OM), and Black
Carbon (BC). Long-term exposure to PM 2.5 is
one of the major immediate human health risks
from air pollution [14]. Specific health effects
are varied but include cardiovascular and pulmonary complications. Other effects of PM include
the ability to alter the radiative balance of the
Earth [15].
What Are the HAPs?
Specific VOCs are very hazardous to human
health. These include benzene, PAHs (polycyclic
aromatic hydrocarbons), 1,3-butadiene, ethane,
propene, and some aldehydes [5]. Hazardous
VOCs share sources with the bulk of VOCs.
Dioxins and furans are chlorine containing
chemicals with similar chemical structural elements [16]. Their health effects can be extreme
and of a wide variety, including cancer and reproductive abnormalities [16]. Dioxins and furans
tend to accumulate in soils and sediments, but
their sources include sources of air pollution
such as municipal waste incinerators [16] and
pyrotechnics [17]. They are bio-accumulative
[18], meaning that they remain within the bodies
of plants and animals that absorb them.
Heavy metals such as arsenic and nickel are not
very prevalent in the atmosphere, other than near
their industrial sources, but even at low concentrations they can produce serious health effects
[5]. These metalloids, metals and their compounds are classified as HAPs. Some lighter
metals are also classified as HAPs such as beryllium and cobalt [4].
Lead (Pb) is a HAP [4] worthy of note for its
relative abundance. Lead emissions are the source
of a wide range of human health problems [19,
20]. While lead as a fuel additive has largely been
phased out in the Western world, there are many
390
Air Pollution Monitoring and Sustainability
is emissions from vehicles, and catalytic converters are used to minimize these emissions.
Other high-temperature combustion processes
also contribute. Emissions of NO x can indirectly
lead to acid deposition (or “acid rain”).
Combustion of fossil fuels containing sulfur
leads to emissions of SO 2 . Refining and production
of fuels and minerals (e.g., lead smelting, aluminum refining) also emits substantial amounts of
SO 2 . SO 2 negatively impacts human health, contributes to acid deposition, and can promote aerosol
formation and growth. Sulfate formed from SO 2 is
a major contributor to aerosol mass in some
regions. Aerosol produced through historic emissions of SO 2 is believed to have caused a negative
climate forcing that suppressed temperature rise in
the second half of the last century. Using fuels that
contain only trace amounts of sulfur, such as natural gas, or that contain less sulfur, such as lowsulfur coal, results in less emission of SO 2 . There
are also downstream options such as flue-gas
desulphurization [5].
Tropospheric ozone (O 3 ) is a major irritant to
human health and vegetation. O 3 is a secondary
pollutant, meaning that O 3 is rarely directly emitted
from point sources but is formed via chemical
reactions involving other air pollutants such as
NO x and VOCs.
There is a multitude of volatile organic carbon
(VOC)
species
both
biogenic
and
anthropogenic. Many have been identified as particular hazards, and they are discussed in the section below on HAPs. Some anthropogenic VOCs
have been associated with causing cancer in
humans [9]. Anthropogenic sources include vehicle emissions, petroleum product manufacture
and use, biomass burning, landfill gas, sewage
treatment [10], and off-gassing from building
materials. Biogenic VOCs can be the result of
the natural metabolic processes of life forms [11]
and natural decomposition. VOCs play a crucial
role in the formation of tropospheric ozone [12].
PM (particulate matter) is a term that covers a
wide variety of liquid and solid particles
suspended in the atmosphere. PM is classified
by size (according to aerodynamic diameter) and
various chemical species of PM exist, even
within single particles. Size classifications are
typically given as PM 10 (particles with aerodynamic diameters less than 10 mm), PM 2.5
(particles with aerodynamic diameters less than
2.5 mm), and Ultrafine Particles (UFP, particles
with aerodynamic diameters less than 0.1 mm).
Particulate species include sulfate (SO 4
2À and
containing particles), nitrate (NO 3
À
), ammonium (NH 4
+ ), Organic Matter (OM), and Black
Carbon (BC). Long-term exposure to PM 2.5 is
one of the major immediate human health risks
from air pollution [14]. Specific health effects
are varied but include cardiovascular and pulmonary complications. Other effects of PM include
the ability to alter the radiative balance of the
Earth [15].
What Are the HAPs?
Specific VOCs are very hazardous to human
health. These include benzene, PAHs (polycyclic
aromatic hydrocarbons), 1,3-butadiene, ethane,
propene, and some aldehydes [5]. Hazardous
VOCs share sources with the bulk of VOCs.
Dioxins and furans are chlorine containing
chemicals with similar chemical structural elements [16]. Their health effects can be extreme
and of a wide variety, including cancer and reproductive abnormalities [16]. Dioxins and furans
tend to accumulate in soils and sediments, but
their sources include sources of air pollution
such as municipal waste incinerators [16] and
pyrotechnics [17]. They are bio-accumulative
[18], meaning that they remain within the bodies
of plants and animals that absorb them.
Heavy metals such as arsenic and nickel are not
very prevalent in the atmosphere, other than near
their industrial sources, but even at low concentrations they can produce serious health effects
[5]. These metalloids, metals and their compounds are classified as HAPs. Some lighter
metals are also classified as HAPs such as beryllium and cobalt [4].
Lead (Pb) is a HAP [4] worthy of note for its
relative abundance. Lead emissions are the source
of a wide range of human health problems [19,
20]. While lead as a fuel additive has largely been
phased out in the Western world, there are many
390
Air Pollution Monitoring and Sustainability