Frumkin, 2e
Part Three: Environmental
Health on the Regional Scale
Chapter 12: Air Pollution
History of Air Pollution
 Since human beings discovered fire, they began to pollute the
air.
 At first, air pollution was a local problem resulting from the
smoke from kilns, hearths, and furnaces.
 However, with the rise of industrialization and the
development of time, air pollution has become a global
problem.
 It came to the forefront of public attention in the form of
severe and fatal episodes, such as that of Donora, PA and the
Meuse Valley in Belgium.
Types of Ambient Air Pollution
 Air pollutants can be categorized by their source or by their physical
and chemical characteristics.
 An air pollutant may be either directly emitted (a primary pollutant)
or formed in the atmosphere through the physical and chemical
conversion of precursors (a secondary pollutant).
 Another important feature of air pollution sources is whether the
emissions are natural (biogenic) or the result of human activity
(anthropogenic).
 Additionally, air pollutants differ in their physical form; they can be
either gases or particles.
 A final way of classifying air pollutants relates to the way they are
legally regulated. Some are criteria pollutants (the major pollutants,
including carbon monoxide, lead, nitrogen, etc.), and others are
hazardous air pollutants, which include a number of volatile organic
chemicals, pesticides, herbicides, and radionuclides.
Studies on Air Pollution and
Health
 Epidemiological studies investigate the relationship between air pollutant
concentrations and health outcomes under the real-world conditions of
exposure, typically in large populations in community settings.
 Herein, data on pollutant concentrations are obtained by air monitoring, and
used as measures of individual exposure.
 However, epidemiological studies can potentially be limited by the inability
to control for other factors, referred to as confounding factors, such as
temperature, weather, population characteristics, and pollutants other than
those being investigated, and by the difficulty of accurately estimating
personal exposure.
 Controlled human exposure studies correct for possible confounds, and
involve exposure of volunteers to a specified concentration of a particular
air pollutant or pollutant mixture in a laboratory setting and then
measurements of their health responses.
Sources of Air Pollution
 There are many sources of air
pollution, including particulate matter,
sulfur dioxide, nitrogen oxides, volatile
organic compounds, tropospheric
ozone, carbon monoxide, lead, and
mercury.
Particulate Matter
 Particulate matter (PM) refers to a generic class of pollution
rather than to a particular, individual pollutant with a specified
chemical structure.
 PM includes solid or liquid particles suspended in air,
regardless of their chemical composition.
 The composition of PM differs by geographic area and can vary
with season, source, and meteorology.
Particulate Matter, con’t
 Particles are generally categorized according to their
size, using a measure called aerodynamic diameter .
This is the diameter of a uniform sphere of unit density
that would attain the same terminal settling velocity as
the particle of interest.
 Ambient levels of PM, have been associated with health
effects including increased hospital and emergency
room admissions, respiratory symptoms, decline in
pulmonary function, exacerbation of chronic respiratory
and cardiovascular diseases, and premature mortality.
Sulfur Dioxide
 Sulfur dioxide, SO2, is a water-soluble gas that is produced from the
combustion of sulfur-containing fuels and materials, such as coal and
metal ores.
 SO2 can be converted to sulfuric acid, and therefore contributes to acid
deposition, which harms vegetation, other materials, and wildlife. SO2
also contributes to the formation of particulate matter.
 Because SO2 is highly soluble in water, most inhaled SO2 is absorbed by
the mucous membranes of the upper airways with little reaching the
lung.
 SO2 exposure has been associated with reduced lung function,
bronchoconstriction (increased airway resistance), respiratory
symptoms, hospitalizations from cardiovascular and respiratory causes,
eye irritation, adverse pregnancy outcomes, and mortality.
Nitrogen Oxides
 Nitrogen oxides, NOx, make up a category of highly reactive
gases containing nitrogen and oxygen, such as nitrogen dioxide
(NO2) and nitrogen oxide (NO).
 NOx are produced through combustion, including fossil fuel
combustion, when the nitrogen that constitutes almost 80
percent of air is oxidized.
 Like ozone, NO2 is nearly insoluble in water and can reach the
lower respiratory tract.
 Health effects of NO2 include irritation of the eyes, nose, and
throat at higher concentrations; short-term decreases in lung
function; and possibly increased respiratory infections and
symptoms for children.
Volatile Organic
Compounds
 Volatile organic compounds (VOCs) are a category of organic
chemicals with a high vapor pressure, which readily evaporate at
normal temperature and pressure.
 They include benzene, chloroform, formaldehyde, isoprene,
methanol, monoterpenes, and hundreds of additional compounds.
 VOCs originate from natural sources (primarily vegetation such as
oak and maple trees); industrial processes involving such things as
chemical processing, use of solvents, and power generation; and
transportation, including motor vehicles and off-road transportation
sources such as aircraft, construction equipment, and lawn mowers.
 VOCs are precursors of ozone but also have independent health
effects, including irritation of the respiratory tract, headaches, and
carcinogenicity.
Tropospheric Ozone
 Ozone (O 3 ), a gas, is present in the troposphere, the lowest
atmospheric layer, which extends from the Earth’s surface to the
stratosphere.
 Stratospheric ozone forms the naturally occurring ozone layer that
protects us from ultraviolet radiation, whereas tropospheric ozone,
sometimes called ground-level ozone, is a harmful pollutant.
 Tropospheric ozone is a colorless gas and a photochemical oxidant
formed through complex, nonlinear chemical reactions involving the
precursors VOCs and NOx in the presence of sunlight.
 Ozone is not highly soluble in water and can thus reach the lower
respiratory tract.
Ozone, con’t
 Because of its oxidant properties, ozone can break
molecular bonds and rapidly damage human
tissue. Short-term exposure to ozone for healthy
adults has been associated with temporarily
decreased lung function, increased airway
resistance, and increased respiratory symptoms,
such as coughing and wheezing.
 Asthmatics are particularly susceptible to health
problems associated with ozone exposure.
Carbon Monoxide
 Carbon monoxide (CO) is a colorless, odorless gas
formed by incomplete combustion of carbonaceous
material, such as gasoline, natural gas, oil, coal,
tobacco, and other organic materials.
 When CO is inhaled, it binds to hemoglobin, with
over 200 times the affinity of oxygen, to form
carboxyhemoglobin (COHb). An increased level of
COHb reduces the transport of oxygen to tissues and
inhibits the release of oxygen, causing problems in
the brain, heart, and respiratory system.
Lead
 Historically, lead in ambient air came largely from leaded fuel,
that is, fuel with lead added as an antiknocking agent.
 Most countries have already phased out leaded gasoline or have
plans to do so. In these areas, nonairborne sources of lead, such as
ingestion of leaded paint, are a larger health concern than airborne
lead.
 Lead can be harmful even at low doses because it accumulates in
the body, mostly in the bones.
 Exposure to lead can cause damage to the nervous system and
kidneys and can interfere with red blood cell formation,
reproductive function, and gastrointestinal function.
Mercury
 Mercury is naturally occurring, but can be released into the
atmosphere, soil, or water through human activities.
 Because mercury commonly contaminates coal, coal-fired
power plants are the largest source of airborne mercury in the
United States.
 Mercury exposure can occur through inhalation, skin contact,
or ingestion, and the health effects of mercury depend on its
chemical form.
 Mercury can be deposited into water bodies and consumed by
fish, presenting the problem of exposure through food intake.
Air Toxics
 Hundreds of other ambient air pollutants exist besides those
just described.
 They include hydrochloric acid, captan, parathion,
naphthalene, biphenyl, vinyl bromide, methyl bromide, dioxin,
and cadmium.
 Exposure to these pollutants can occur through inhalation, but
they also enter other environmental media such as water and
food.
 Health effects of these air toxics include damage to the
neurological, immune, respiratory, and reproductive (for
example, reduced fertility) systems, as well as developmental
problems and some cancers.
Air Pollution Prevention And
Control
 Air quality management approaches include controlling
emissions at the source, by such means as scrubbers at
coal-fired power plants; reducing the volume of
emissions, by such means as increased use of public
transportation to lower vehicular air pollutants or
emissions controls for automobiles; and decreasing
population exposure.
 Reduction of the health effects of air pollution comes
from actions at multiple spatial and institutional levels,
ranging from personal decisions by individuals, to
community and state plans, and to multigovernment
agreements.