Chapter 6: Air
“ I thought I saw a blue jay this morning. But the
smog was so bad that it turned out to be a cardinal
holding its breath.”
Michael J Cohen, Professor of Political Science
Bar Ilan University, Israel
6.1 What Causes Air Pollution?
• In Mexico City, children rarely use the color blue to make
paintings of the sky; it is known as one of the most dangerous
cities in the world for children because the air is so polluted
(nearly 20 million people live there)
• Clean air consists mostly of nitrogen and oxygen gases, along
with small amounts of CO2 and water vapor
• Some areas, like Mexico City, get so polluted they tell kids to stay
home from school; people who go outside must wear dust masks
• When unhealthy substances are in the air it is called air
pollution; most air pollution is a result of human activities;
however, some air pollution comes from natural sources (ex:
volcano will spew clouds of particles and sulfur dioxide into the
atmosphere); other natural pollutants are dust, pollen, spores
The History of Air Pollution
• Air pollution is nothing new; burning fuels put
pollutants into the air [ex: Rome, 2000 years
ago, philosophers complained of the foul air;
England, (circa: 1273) banned burning a
particular coal]
• Air quality is much worse today because modern
industrial societies burn large quantities of fossil
fuels (urban areas are from motor vehicles and
industry)
Primary and Secondary Pollutants
• Primary pollutant is a pollutant that is put
directly into the air by human activity (ex: soot
from smoke)
• Secondary pollutants are formed when a
primary pollutant comes into contact with other
primary pollutants, or with naturally occurring
substances like water vapor and a chemical
reaction takes place (ex: ground-level ozone
forms when the emissions from cars, trucks and
natural sources react with the ultraviolet rays of
the sun and then mix with the oxygen in the
atmosphere)
Sources of Primary Air Pollutants
• Household products, power plants and motor vehicles are
sources of primary air pollutants (carbon monoxide, sulfur
dioxide, nitrogen oxide and chemicals called volatile
organic compounds (VOCs).
• Sources of pollutants: Vehicles: carbon monoxide
(important component of the exhaust), nitrogen oxide and
VOCs; Coal-burning power plants: nitrogen oxide; Coal
and Oil burning, power plants, refineries, metal smelters:
sulfur dioxide
• Particulate matter also pollutes the air; divided into fine
particles (enter from fuel burned by vehicles and coalburning power plants) and coarse particles (cement plants,
mining operations, incinerators, wood-burning fireplaces,
fields and roads)
•
Industrial Air Pollution
• Many industries and power plants generate electricity by
burning fossil fuels
• Burning fossil fuels cause large quantities of oxides to be
released into the air; electric power plants produce at
least 2/3 of all sulfur dioxide, 1/3 of all nitrogen oxides,
and ½ of the particulates
• VOCs (volatile organic compounds) form toxic fumes;
petroleum refineries put VOCs into the air when
converting crude oil into refined fuel (gasoline); auto and
airplane manufacturing release VOCs which vaporize
(spray painting parts)
Regulating Air Pollution From Industry
• Clean Air Act requires industries to use scrubbers or
other pollution control devices
• Scrubbers remove some of the more noxious
substances; gases are moved through a spray of water
that dissolve many pollutants
• Electrostatic precipitators (used in cement factories and
coal burning power plants) remove particulates from
smokestacks; 20 million tons of ash are removed every
year in the US by these electrostatic precipitators
6.2 Motor Vehicle Emissions
• Over 1/3 of our air pollution comes from gasoline
burned in motor vehicles
• Approximately 70% of air pollution comes from
by cars and trucks, the rest by commercial
vehicles; In 1995, US vehicles traveled over 2
trillion miles, by 1998, Americans drove over 2.6
trillion, 90% driven by passenger cars, the rest
by trucks and buses
Controlling Vehicle Emissions
• Clean Air Act (1970, strengthened in 1990) gave the EPA the
authority to regulate automobile emissions
• EPA required gradual elimination of lead in gas, resulting in more
than a 90% drop of lead pollution;
• Catalytic converters (required in automobiles) clean exhaust gases
of pollutants before they are able to exit the tailpipe; EPA estimates
that vehicles burn fuel 35% more efficiently, with 95% fewer
emissions of pollutants (except CO2) than 30 years ago
• Driving less is an effective way of reducing air pollution (ex:
carpooling with one other person would reduce 33 million lbs. of CO2
into the air
• Car manufacturers are making cars to run on fuels which cause less
air pollution (solar, batteries, hydrogen, natural gas)
• Brazil has over 4 million cars that run on ethanol (made from
remnants of sugarcane plants)
• Ethanol is less polluting; burns to form CO2 and H2O
California Zero-Emissions Vehicle Program
• Zero-emission vehicles have no tailpipe emissions, no
emissions from gasoline and no emission-control
systems that deteriorate over time.
• By 2016, California requires 16% of all vehicles sold to
be zero-emission vehicles (SUVs, trucks, sm. vans and
autos); at present, ZEVs (electric vehicles) and
advanced battery vehicles are being demonstrated by
major automobile companies; vehicles powered by
hydrogen are being developed; some partial zeroemission vehicles are included (hybrid-electric, methanol
fuel cells.
• Zero-emission programs have also been adopted in
Maine, Massachusetts, New York and Vermont.
Smog
• When air pollution hangs over urban areas and reduces
visibility, it is called SMOG (smoke and fog); chemical
reaction involving sunlight, nitrogen oxides and
hydrocarbons.
• Pollutants released by automobiles and industries are
the main causes of smog
• Cities, like Los Angeles, Denver and Mexico City, suffer
the most from smog (dry, sunny locations with dense
traffic)
Temperature Inversions
• Air circulation usually keeps air pollution from reaching
dangerous levels (sun heats the surface of the Earth and air
near it, warm air rises through the cooler air, carrying
pollutants away from Earth’s surface)
• Sometimes pollution gets trapped near Earth’s surface
(temperature inversion- air above is warmer than the air below
it); traps the pollutants below with the cooler air. If a city is
located in a valley (Los Angeles), the city has a higher chance
of experiencing temperature inversions
6.3 Air, Noise and Light Pollution
• Air pollution can cause serious health problems;
especially, the very young, the very old and those with
heart or lung problems
• Air pollution aggravates existing diseases; death
certificates indicate emphysema, asthma, lung cancer as
causes rather than air pollution
• Americans pay tens of billions of dollars a year in health
costs to treat respiratory diseases attributed to air
pollution
Short-Term Effects of Air Pollution on Health
• Many of the effects of air pollution on people’s health are
short-term and are reversible IF their exposure
decreases
• Examples of short-term exposure: headache; nausea;
irritation to the eyes, nose and throat; tightness in the
chest; coughing; upper respiratory infections (bronchitis,
pneumonia)
• Pollution can make asthma and emphysema worsen in
individuals with these conditions
Chronic Bronchititis and Asthma
• Chronic Bronchitis is the persistent inflammation of the
bronchial linings; constant coughing weakens the
bronchial tubes and eventually breathing becomes
difficult; particulates, oxides and acids of sulfur and
nitrogen are the main irritants
• Bronchial asthma is a condition in which the bronchial
passages constrict and become blocked with mucus; the
same pollutants mentioned above are largely
responsible for aggravating asthma; asthma is not
caused by air pollution but the air pollutants may worsen
it
Emphysema and Lung Cancer
• Air pollution has been linked to emphysema (air sacs in
the lungs lose their elasticity and can no longer push air
out of the lungs, thus the exchange of oxygen and
carbon dioxide is impaired); sufferers cannot perform
even the simplest of tasks without gasping for air
• Lung cancer is also linked to air pollution; cigarette
smoking is the major cause of lung cancer; automobile
exhaust and particulates also contribute to lung cancer
• Non-smoking city dwellers are 3 to 4 times likely to
develop lung cancer than nonsmoking residents in rural
areas
Indoor Air Pollution
• The air inside buildings is sometime worse than the air
outside (Americans spend 89%of their time indoors)
• Plastic and other industrial compounds are a major source of
pollution (ex: carpet, building material, paint, furniture)
• Buildings that have windows that open allow pollutants to
circulate and pass out of the building; ones that are tightly
closed up, pollutants will accumulate and reach higher levels
than they could outdoors
• Sick-building syndrome (buildings with poor air quality)are
most often found in the desert Southwest, Southern California
and Florida
• Air filters in air-conditioning systems can help relieve indoor
air pollution, but not all can be removed; it is best to ventilate
a building with outdoor air
Asbestos
• Asbestos is the name given to a combination of several
fibers containing silica that are valued for their strength
and resistance to heat (form in long, thin fibers)
• Asbestos was primarily used as an insulator and as a fire
retardant, also used extensively in building materials;
government banned the use of most products in the
early 1970’s
• Also widely used to reinforce cement, make brake
linings, vinyl floor tiles, residential siding, firefighters
clothing, and used in commercial buildings (schools, US
has spent over $40 billion to remove from buildings)
• Asbestos fibers can cut and scar the lungs (asbestosis),
causing victims to have trouble breathing which will lead
to heart failure
6.4
Radon Gas
• Radon gas is invisible, tasteless, and odorless, and it is
also radioactive; second leading cause of lung cancer in
the US
• Produced by radioactive decay of uranium, which occurs
naturally in the Earth
• It is concentrated in porous soil overlying rocks that
contain radon; can enter home, offices and schools by
seeping through cracks and holes in foundations and
adheres to dust particles; when you inhale the dust, it
enters the lungs
• In the lungs, radon releases alpha particles, which
destroy the genetic material in cells lining the air
passages, leading to cancer, especially among smokers
Noise Pollution
• A sound of any kind is called noise; however,
some are unnecessary and can cause noise
pollution (noise that affects human health and
quality of life)
• Examples: airplanes, construction equipment,
city traffic, factories, home appliances,
lawnmowers
• Health problems associated with noise pollution:
loss of hearing, high blood pressure, stress, loss
of sleep (leads to decreases productivity at work
and in the classroom)
Noise Pollution…continued
• Noise is measured in decibels (dB). Lowest point on
decibel scale is 0 dB; highest point if 180 dB; for each
increase in dB intensity, the decibel level is 10 times higher
than the previous level. (ex: 20 dB is 10 times higher the
intensity of 10 dB, 30 dB is 100 times the intensity of 10 dB,
etc.)
• 120 dB is at the threshold of pain; permanent deafness may
come as a result of continuous exposure to sounds over 120
dB
• Ex: rocket engine 180 dB; jet engine 140dB; rock-and-roll
concert 120dB; car horn 110 dB; chainsaw 100 dB;
lawnmower 90dB; doorbell 80 dB; conversation 60 dB;
whisper 30dB
Light Pollution
• Unlike air or water pollution, light pollution does not
present a direct hazard to human health; however, it
does cause negative affects on the environment (ex:
inefficient lighting diminishes our view of the night sky
and in urban areas, is often much brighter than the
natural sky)
• Most important environmental concern of inefficient
lighting is energy waste (ex: light directed upward into
the night sky and lost to space – billboards, other signs
that are lit from below, lighting exteriors of buildings,
poor quality street lights)
• One solution to energy waste: shielding light so it is
directed downward, using time controls, using lowpressure sodium sources (most efficient source of light)
6.5: Acid Precipitation
• Suppose that one day you are hiking in the woods. You
come to a lake and sit down to rest. You are looking at
the lake, amazed at how clear the water is, and then you
realize something is wrong. You realize there are no fish
in the water.
What Causes Acid Precipitation?
• This lake and thousands of lakes throughout the world
are victims of acid precipitation, also known as acid rain.
• Acid precipitation is rain, sleet or snow that contains a
high concentration of acids.
• When fossil fuels are burned, they release oxides of
sulfur and nitrogen; when combined with water in the
atmosphere, they form sulfuric acid and nitric acid
• Acid precipitation falls to Earth, flows over the land, into
lakes, rivers and streams killing living things (both plant
and animal)
pH Level
• A pH (power of hydrogen) number is a measure of how acidic or
basic a substance is
• The lower the pH, the more acidic a substance is; the higher the
pH number is, the more basic the substance is; each whole
number on the pH scale indicates a tenfold change in acidity
• Pure water has a pH of 7.0; normal precipitation has a pH of 5.6;
water is considered acid precipitation if it has a pH below 5.0
• pH of precipitation varies between locations: Scandinavia
ranges between 4.3 to 4.5; Europe between 4.5 and 5.1; eastern
US and Canada ranges between 4.2 and 4.8
• The most acidic precipitation in North America occurs around
Lake Erie and Lake Ontario; pH levels are about 4.2
How Acid Precipitation Affects Soils and Plants
• Plants adapt over long periods of time to the acidity of
the soil they grow in; acid precipitation can cause a drop
in soil and water pH; this increase is call acidification
• Acidification changes the balance of soil’s chemistry;
some nutrients are dissolved and washed away,
aluminum and other toxic metals may be released and
absorbed by roots of plants (root damage); sulfur dioxide
clogs the openings on the surface of plants
Acid Precipitation and Aquatic Ecosystems
• Aquatic animals are adapted to live in water with specific pH
levels; if acid rain falls on a lake, it can change the pH level, thus
killing aquatic plants, animals and fish. Aluminum can also leach
out of the soil surrounding the lake, accumulating in the gills of
the fish, which interferes with the oxygen and salt exchange.
• Worse in the spring when snow melts; creates acid shock (rapid
change in water’s pH) which results in a large number of fish
dying; also affects the reproduction of fish and amphibians
(produce fewer eggs which oftentimes don’t even hatch; offspring
that do survive may have birth defects and cannot reproduce)
• To offset the effects of acid rain, some place in the US and other
countries will spray powdered lime on the lakes to help restore
the natural pH of the water
Acid Precipitation and Humans
• Acid precipitation can affect humans in a variety of ways
• Toxic metals (aluminum and mercury) can be released
into the soil and find their way into crops, water and fish
which are then eaten by humans
• Researchers believe there may be a connection between
acid precipitation and respiratory problems, especially in
children
• Standard of living of some peoples is affected:
commercial fisherman, sport fishing industries, forestry
• Acid precipitation destroys buildings and historic
monuments
International Conflict and Cooperation
• One big problem in controlling acid precipitation is that
pollutants may be released in one geographic location
and fall to the ground in another location (ex: ½ of the
acid rain falling in southeastern Canada results from
pollution produced in Ohio, Indiana, Pennsylvania,
Illinois, Missouri, West Virginia and Tennessee
• Very difficult to solve since acid precipitation falls
downward (Canada-US Air Quality Agreement was
signed in 1991); both countries agreed to reduce acidic
emissions that flowed across the border.