Air & Air Pollution
mixture of gases that forms a layer about 250 miles thick around the earth
bottom 5 - 11 miles (7 - 16 km) contains most (75%) of the air
Composition of clean, dry air:
presence of chemicals in the atmosphere in quantities and duration that
are harmful to human health and the environment
Types of air pollutants:
Primary pollutants - products of natural events (like fires and volcanic
eruptions) and human activities added directly to the air
Secondary pollutants - formed by interaction of primary pollutants with
each other or with normal components of the air
Major Classes of Air Pollutants:
Carbon oxides (CO & CO2)
sources = incomplete combustion of fossil fuels
transportation, industry, & home heating
CO2 is an important greenhouse gas
CO (carbon monoxide)
the most abundant pollutant know to affect human health
combines with hemoglobin & may create problems for infants, the elderly,
& those with heart or respiratory diseases
Sulfur oxides (mainly SO2, or sulfur dioxide)
source = combustion of coal & oil (esp. coal)
SO2 released in the U.S. comes from:
industrial manufacturing processes 12.7%
industrial combustion 11.6%
other sources 2.5%.
can react with gases in atmosphere to form sulfuric acid ('acid rain')
20 million tons released in U.S. every year
Exposure to SO2 can cause impairment of respiratory
function, aggravation of existing respiratory disease (especially bronchitis),
and a decrease in the ability of the lungs to clear foreign particles.
It can also lead to increased mortality, especially if elevated levels
of particulate matter (PM) are also present. Groups that appear most sensitive
to the effects of SO2 include asthmatics and other
individuals with hyperactive airways, and individuals with chronic obstructive
lung or cardiovascular disease. Elderly people and children are also likely
to be more sensitive to SO2.
Nitrogen oxides - NO (nitric oxide) & NO2
source = motor vehicles & industry (burning fossil fuels)
can react with other gases in atmosphere to from nitric acid (HNO3)
Volatile organic compounds (hydrocarbons) - methane, benzene, propane,
& chlorofluorocarbons (CFC's)
source = motor vehicles (evaporation from gas tanks), industry, & various
18 million tons released each year in U.S.
Concentrations of many VOCs are consistently higher indoors than outdoors.
A study by the EPA, covering six communities in various parts of the United
States, found indoor levels up to ten times higher than those outdoors-even
in locations with significant outdoor pollution sources, such as petrochemical
Eye and respiratory tract irritation, headaches, dizziness, visual disorders,
and memory impairment are among the immediate symptoms that some people
have experienced soon after exposure to some organics. At present, not
much is known about what health effects occur from the levels of organics
usually found in homes. Many organic compounds are known to cause cancer
in animals; some are suspected of causing, or are known to cause, cancer
Suspended particulate matter
solid particles (e.g., dust, soot, & asbestos) & liquid droplets
sources = power plants, iron/steel mills, land clearing, highway construction,
mining, & other activities that disturb or disrupt the earth's surface
act as respiratory irritants; some are known carcinogens (e.g., asbestos)
can aggravate heart/respiratory diseases
trace amounts of at least 600 toxic substances (such as lead and mercury)
produced by human activities
is an element that occurs naturally in the earth’s crust. Most people and
wildlife can generally tolerate the extremely low levels of this naturally
occuring substance. When mercury enters the body it becomes concentrated
in tissue, an effect known as bioaccumulation. Because this element is
toxic at very low concentrations, even slight increases in the minute concentrations
naturally present in the environment can have serious effects on humans
Once mercury enters the water it can be converted to its most toxic
form, methyl mercury, by bacteria or chemical reactions. Methyl mercury
is absorbed by tiny aquatic organisms, which are then eaten by small fish.
The chemical is stored in the fish tissue and is passed on at increasing
concentrations to larger predator fish. People and wildlife at the top
of the food chain are consequently exposed to elevated amounts of methyl
mercury through the contaminated fish they consume.
sources of mercury = burning coal and waste (such as medical wastes)
Because sunlight has a critical role in its formation, ozone pollution
is principally a daytime problem in the summer months. The presence of
hydrocarbons and nitrogen oxide in sunlight with little air movement leads
to the generation of ozone. These two compounds are produced by cars, trucks,
factories, and power-generating plants or wherever gasoline, diesel fuel,
kerosene, oil, or natural gas are combusted. These gases combine together
with sunlight, producing ozone. Urban areas with heavy traffic and large
industrialized communities are primary areas for ozone problems.
The greatest concern about ozone pollution is the potential damage it may
inflict on human health. High concentrations of ozone are especially hazardous
to children, the elderly, and people with respiratory problems. Each year
many food crops are damaged by ozone. Ozone also damages rubber, nylon,
plastics, dyes, and paints.
EPA provides maps showing
levels of ozone pollution:
8-hour Average Concentration
(Yellow = moderate ozone levels;
Orange = Unhealthy for sensitive groups, e.g., those
with respiratory diseases such as asthma)
Wednesday, 25 July 2001
Source: Environmental Protection Agency
Map shows where pollutants exceeded EPA standards in
forms from mixture of primarily nitrogen oxides (from vehicles), volatile
organic compounds, & sunlight
complex mixture of gases but primarily ozone
more common in cities with sunny, dry, warm climates, such as Los Angeles,
Denver, Salt Lake City, Sydney, & Mexico City
Effects of Air Pollution
on Human Health
Much evidence links air pollutants to respiratory & other diseases
Examples of air pollution-related diseases:
Pulmonary irritation & impaired lung function:
Increased susceptibility to disease
Effects of Air Pollution on other animals & plants:
Wild & domestic animals probably affected in the same ways as humans
Plants damaged by ozone, sulfur dioxide, & acids:
ozone - weakens pine needles & makes them more susceptible to insects
sulfur dioxide - suppresses growth
acid - damages leaves & needles & also removes nutrients
Where do acids come from?
Nitric oxide & sulfur dioxide released primarily from electric power
plants & motor vehicles
SO2 + water vapor + ozone ---> H2SO4
NO + sunlight + O2 ---> NO2 +
various atmospheric gases ---> HNO3
Prevailing winds transport the compounds, sometimes hundreds of miles,
across state and national borders.
Average annual pH of rainfall:
The pH scale and acid rain:
Acid rain is measured using a scale called "pH." The lower a substance's
pH, the more acidic it is. Pure water has a pH of 7.0. Normal rain is slightly
acidic because carbon dioxide dissolves into it, so it has a pH of about
5.5. As of the year 2000, the most acidic rain falling in the US has a
pH of about 4.3.
Effects of Acid Deposition
of lakes and streams
Acid rain causes a cascade of effects that harm or kill individual fish,
reduce fish population numbers, completely eliminate fish species from
a waterbody, and decrease biodiversity. As acid rain flows through soils
in a watershed, aluminum is released from soils into the lakes and streams
located in that watershed. So, as pH in a lake or stream decreases,
aluminum levels increase. Both low pH and increased aluminum levels are
directly toxic to fish. In addition, low pH and increased aluminum levels
cause chronic stress that may not kill individual fish, but leads to lower
body weight and smaller size and makes fish less able to compete for food
and habitat. Generally, the young of most species are more sensitive to
environmental conditions than adults. At pH 5, most fish eggs cannot hatch.
At lower pH levels, some adult fish die. Some acid lakes have no fish.
contributes to damage of trees
Acid rain does not usually kill trees directly. Instead, it is more likely
to weaken trees by damaging their leaves, limiting the nutrients available
to them, or exposing them to toxic substances slowly released from the
soil. Quite often, injury or death of trees is a result of these effects
of acid rain in combination with one or more additional threats. Acidic
water dissolves the nutrients and helpful minerals in the soil and then
washes them away before trees and other plants can use them to grow. At
the same time, acid rain causes the release of substances that are toxic
to trees and plants, such as aluminum, into the soil.
Forests in high mountain regions often are exposed to greater amounts of
acid than other forests because they tend to be surrounded by acidic clouds
and fog that are more acidic than rainfall. Scientists believe that when
leaves are frequently bathed in this acid fog, essential nutrients in their
leaves and needles are stripped away. This loss of nutrients in their foliage
makes trees more susceptible to damage by other environmental factors,
particularly cold winter weather.
accelerates the decay of building materials and paints, including irreplaceable
buildings, statues,and sculptures that are part of our nation's cultural
Controlling Acid Deposition
Clean up smokestacks and exhaust pipes
Almost all electricity comes from burning fossil fuels like coal, natural
gas, and oil. Acid deposition is caused by two pollutants that are released
into the atmosphere, or emitted, when these fuels are burned: sulfur dioxide
(SO2) and nitrogen oxides (NOx).
Coal accounts for most U.S. sulfur dioxide (SO2) emissions
and a large portion of NOx emissions. Sulfur is present in coal as an impurity,
and it reacts with air when the coal is burned to form SO2.
In contrast, NOx is formed when any fossil fuel is
Options for reducing SO2 & NOx
using coal containing less sulfur, washing the coal, and using devices
called scrubbers to chemically remove the SO2 from the gases leaving the
Power plants can also switch fuels; for example burning natural gas creates
much less SO2 than burning coal. Certain approaches
will also have additional benefits of reducing other pollutants such as
mercury and carbon dioxide.
catalytic converters reduce NOx emissions from cars.
These devices have been required for over twenty years in the U.S., and
it is important to keep them working properly.
Use alternative energy sources
There are other sources of electricity besides fossil fuels. They include:
hydropower, wind energy, geothermal energy, and solar energy. There are
also alternative energies available to power automobiles, including natural
gas powered vehicles, battery-powered cars, fuel cells, and combinations
of alternative and gasoline powered vehicles.
Take action as individuals
Individuals can contribute directly by conserving energy, since energy
production causes the largest portion of the acid deposition problem. For
example, you can:
Turn off lights, computers, and other appliances when you're not using
Use energy efficient appliances: lighting, air conditioners, heaters, refrigerators,
washing machines, etc.
Keep your thermostat at 68 F in the winter and 72 F in the summer.
Carpool, use public transportation, or better yet, walk or bicycle whenever
Some greenhouse gases occur naturally in the atmosphere, while others result
from human activities. Naturally occuring greenhouse gases include water
vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human
activities, however, add to the levels of most of these naturally occurring
emitted during the production and transport of coal, natural gas, and oil.
Methane emissions also result from the decomposition of organic wastes
in municipal solid waste landfills, and the raising of livestock.
Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), & sulfur hexafluoride
These compounds are potent greenhouse gases. In addition to having high
global warming potentials, SF6 and many HFCs and PFCs have extremely long
atmospheric lifetimes, resulting in their essentially irreversible accumulation
in the atmosphere. Sulfur hexafluoride, itself, is the most potent greenhouse
gas the IPCC has evaluated.
generated in a variety of industrial processes
CO2 levels in the atmosphere have risen substantially
What do we know?
Since 1860, the mean global temperature has risen 0.7 - 1.3 degrees Fahrenheit
10 of the 15 years from 1980 - 1994 were among the hottest in the 113-year
recorded history of temperature measurement
1998 was the warmest year of the last century based on thermometer data
and the warmest of the last millenium based on proxy temperature data.
The IPCC (Intergovernmental Panel on Climate Change) concluded in 1995
that human activities were influencing global climate
In 2001, the IPCC issued its Third Assessment Report stating that "most
of the observed warming over the last 50 years is likely to have been due
to the increase in greenhouse gas concentrations". IPCC points out a number
of features of the climate system, like intensity of rainstorms, that have
already changed and estimates that warming of the coming century will reach
1.4°C-5.8°C (2.5°F-10.4°F) if emissions are not limited.
IPCC finds that warming of between 1°C-2°C (1.8°F-3.8°F)
is likely to pose high risks to unique and threatened ecosystems, and to
lead to increases in the risk of extreme climate events.
Possible Effects of a Warmer World
Changes in food production
Plants and animals generally react to consistently warmer tempartures by
moving to higher latitudes and elevations. Recent studies reveal that some
species have already started to shift their ranges, consistent with warming
trends. Many populations and species may become more vulnerable to declining
numbers or extinction if warming occurs faster than they can respond or
if human development presents barriers to their migration.
Rise in sea level
Warmer temperatures increase melting of mountain glaciers and cause ocean
water to expand. Largely as a result of these effects, global sea level
has risen 4 to 10 inches over the past 100 years. With additional warming,
sea level is projected to rise from half a foot to 3 feet more during the
next 100 years. On average, 50 to 100 feet of beach are lost for every
foot of sea-level rise.
More extreme weather
climate change will lead to more hurricanes, floods, and droughts
Threats to human health
Intergovernmental Panel on Climate Change (IPCC), is a United Nations-sponsored
organization made up of 2,500 scientists from around the world. The IPCC
projects that more frequent and more severe heat waves will be an early
effect of global warming. Events such as the deadly stretch of hot days
that killed 669 people in the Midwest during the summer of 1995 and 250
in the Eastern United States in July 1999 are likely to become more common.
As temperatures rise, disease-carrying mosquitoes and rodents move into
new areas, infecting people in their wake. Global warming will likely put
as much as 65% of the world's population at risk of infection—an increase
of 20%. Scientists at the Harvard Medical School have linked recent U.S.
outbreaks of dengue ("breakbone") fever, malaria, hantavirus and other
diseases to climate change.
Slowing Global Warming
Cut fossil fuel use
Car makers could dramatically increase the fuel economy of their cars and
Most electric utilities still use coal to produce electricity, spewing
millions of tons of carbon dioxide and other pollution into the atmosphere
every year. Part of the problem could be solved by converting these plants
to burn cleaner natural gas.
Improve energy efficiency
Our cars and light trucks, home appliances and power plants could be made
much more efficient by simply installing the best current technology. Energy
efficiency is the cleanest, safest, most economical way to begin to curb
We could do much more to save energy in our homes and office buildings.
More energy efficient lighting, heating and air-conditioning could keep
millions of tons of carbon dioxide out of our air each year.
Reduce deforestation & plant trees
Because global vegetation and soils contain about three times as much carbon
as the planet's atmosphere, terrestrial ecosystems offer an opportunity
to absorb and store (sequester) a significant amount of carbon dioxide
from the atmosphere. By planting trees, preserving forests, and changing
cultivation practices to increase soil carbon, for example, it is possible
to increase the size of carbon sinks.
human population growth
Any progress in meeting these objectives?
Only 4 MDCs (Great Britain, Denmark, Germany, & Norway) have produced
plans to substantially reduce CO2 emissions
CO2 emissions by LDCs are increasing about 5%/year
Overall, global CO2 emissions are still increasing
Greenhouse Gas Emissions in the U.S.
be leading the way to a fundamentally new energy direction based on
clean renewable energy, like wind or solar power. But at present many governments
instead use taxpayers money to support the agenda of the companies which
continue to spend billions of dollars on development of coal, oil or gas
- the climate-damaging fossil fuels.
Climate Ark - The
Premier Climate Change & Renewable Energy Portal
Global Warming Site
Early Warning Signs
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