Air Pollution

Chapter 18

The Asian Brown Cloud

Air Pollution in Shanghai, China, in 2004

The Atmosphere Consists of Several Layers

Atmosphere varies in• Density• Atmospheric pressure• Force, or mass, per unit area of a column of air

Air Movements in the Troposphere Play a Key Role in Earth’s Weather and Climate

Troposphere • 75–80% of the earth’s air mass• Surface to 17 kilometers up• Closet to the earth's surface• Chemical composition of air• 99% is nitrogen (78%) and oxygen (21%)

• Rising and falling air currents: weather and climate

• Involved in chemical cycling

The Stratosphere Is Our Global Sunscreen

Stratosphere• Similar composition to the troposphere, with 2

exceptions• Much less water

• O3, ozone layer, filters UV

• Location• 17 to 48 kilometers up

Natural Capital: The Earth’s Atmosphere Is a Dynamic System with Four Layers

Air Pollution Comes from Natural and Human Sources (1)

Air pollution

Natural sources• Dust blown by wind• Pollutants from wildfires and volcanoes• Volatile organics released by plants • Withdrawing groundwater

Air Pollution Comes from Natural and Human Sources (2)

Human sources: mostly in industrialized and/or urban areas• Stationary sources • Power and industrial plants

• Mobile sources• Motor vehicles

Case Study: Air Pollution in the Past: The Bad Old Days (1)

Discovery of fire

Middle Ages

Industrial Revolution

London, England• 1850s• 1952: yellow fog• Clean Air Act of 1956

Some Pollutants in the Atmosphere Combine to Form Other Pollutants

Primary pollutants• Are harmful chemicals emitted directly into the air from

natural processes and human activities

Secondary pollutants• When a primary pollutant reacts with normal air

components

Air quality improving in developed countries

Much more needs to be done in developing countries• Indoor pollution: big threat to the poor

Sources and Types of Air Pollutants

Indoor Air Pollution

What Are the Major Outdoor Air Pollutants? (1)

Carbon oxides • Carbon monoxide (CO)

• Carbon dioxide (CO2)

• Sources • Human health and environmental impact

What Are the Major Outdoor Air Pollutants? (2)

Nitrogen oxides (NO) and nitric acid (HNO3)

• Sources • Acid deposition• Photochemical smog• Human health and environmental impact

Sulfur dioxide (SO2) and sulfuric acid (H2SO4)

• Sources• Human health and environmental impact

What Are the Major Outdoor Air Pollutants? (3) Particulates

• Suspended particulate matter (SPM)• Consists of a variety of solid particles and liquid droplets small and

light enough to remain suspended in the air for long periods• Fine

• Most harmful• Less than 10 micrometers

• Ultrafine• Diameter less than 2.5 micrometers

• Sources• Dust, wild fires, sea salt• Coal-burning power and industrial plants, motor vehicles,

plowed fields, road construction, unpaved roads, tobacco smoke

• Human health and environmental impact• Mutations, reproductive problems, cancer• 60,000 to 70,000 premature deaths a year

What Are the Major Outdoor Air Pollutants? (4)

Ozone (O3)

• Sources• Human and environmental impact

• Coughing, breathing problems, aggravate lung and heart diseases

Volatile organic compounds (VOCs)• Hydrocarbons and terpenes• Sources

• Plants, wetlands, termites• Rice paddies, landfills, oil and natural gas wells, and cows

• Human and environmental impact• Leukemia, blood disorders

Chemical Reactions That Form Major Outdoor Air Pollutants

Statue Corroded by Acid Deposition and Other Forms of Air Pollution, RI, U.S.

Natural Capital: Lichen Species, Vulnerability to Air Pollutants

Burning Coal Produces Industrial Smog

Chemical composition of industrial smog • Sulfur dioxide, suspended droplets of sulfuric

acid, and solid particles Reduction of this smog in urban cities of the

United States • Large boilers with good pollution control• Tall smokestacks

China and smog• Human deaths (358,000 per year)

How Pollutants Are Formed from Burning Coal and Oil, Leading to Industrial Smog

Sunlight Plus Cars Equals Photochemical Smog Photochemical Smog• Chemical composition• Mixture of primary and secondary pollutants

formed under UV radiation

• Sources• Commuter vehicles releasing NO and VOCs

VOCs + NO2 + Heat + Sunlight yields

• Ground level O3 and other photochemical oxidants

• Aldehydes• Other secondary pollutants

Human health and environmental impact

A Model of How Pollutants That Make Up Photochemicals Are Formed

Global Outlook: Photochemical Smog in Santiago, Chile

Several Factors Can Decrease or Increase Outdoor Air Pollution (1)

Outdoor air pollution may be decreased by• Settling of particles due to gravity• Rain and snow• Salty sea spray from the ocean• Winds • Chemical reactions

Several Factors Can Decrease or Increase Outdoor Air Pollution (2)

Outdoor air pollution may be increased by• Urban buildings• Hills and mountains• High temperatures• Emissions of VOCs from certain trees and plants • Grasshopper effect• Occurs when volatile air pollutants are transported

by evaporation and winds from tropical and temperate areas through the atmosphere to the earth’s polar areas

• Temperature inversions

A Temperature Inversion

Acid Disposition Is a Serious Regional Air Pollution Problem

Acid deposition, acid rain• Formation• Excessive amounts of nitrogen oxides and sulfur

dioxide to the atmosphere• Local versus regional problems• Effects of prevailing winds• Buffers• Where is the worst acid deposition?

Natural Capital Degradation: Acid Deposition, Acid Rain

Current and Possible Future Acid Rain Problem Areas

Acid Deposition Has a Number of Harmful Effects (1)

Human respiratory disorders

Aquatic ecosystems affected

Release of toxic metals• Acid allows metals (lead and mercury) to leach

out into lakes used as water supplies

Acid Deposition Has a Number of Harmful Effects (2)

Leaching of soil nutrients• Allows essential nutrients to leach out and

harmful metals to take their place Loss of crops and trees

Damage to buildings, statues, and monuments

Natural Capital Degradation: Air Pollution Damage to Trees in North Carolina, U.S.

Indoor Air Pollution Is a Serious Problem (1)

Developing countries• Indoor burning• Poor suffer the greatest risk

Developed countries• Indoor air pollution is greater than outdoor air

pollution

Indoor Air Pollution Is a Serious Problem (2)

Why?• 11 of the common air pollutants higher inside

than outside• Greater in vehicles than outside• Health risks magnified: people spend 70–98% of

their time indoors

Indoor Air Pollution Is a Serious Problem (3)

Who are at greatest risk from indoor air pollution?• Children under 5 and the elderly• Sick• Pregnant women• People with respiratory disorders or heart

problems• Smokers• Factory workers

Indoor Air Pollution Is a Serious Problem (4)

Four most dangerous indoor air pollutants• Tobacco smoke• Formaldehyde• Radioactive radon-222 gas• Very small particles

Sources of these pollutants• Radon comes from radioactive decay of uranium,

phosphate, granite, and shale Human health risks

Indoor Air Pollution Is a Serious Problem (5)

Other possible indoor air pollutants• Pesticide residue• Pb particles• Living organisms and their excrements• E.g., Dust mites and cockroach droppings

• Airborne spores of molds and mildews

Sick-building syndrome• Studies have linked various air pollutants found in

buildings to a number of health effects

Some Important Indoor Air Pollutants

Science: Magnified View of a Household Dust Mite in a Dust Ball

Science: Sources and Paths of Entry for Indoor Radon-222 Gas

Your Body’s Natural Defenses against Air Pollution Can Be Overwhelmed

Respiratory system protection from air pollutants• Role of cilia, mucus, sneezing, and coughing

Effect of smoking and prolonged air pollution exposure• Chronic bronchitis• Emphysema

Air Pollution Is a Big Killer

3 Million deaths per year world-wide• Mostly in Asia• Main causes

EPA: proposed stricter emission standards for diesel-powered vehicles

Link between international trade and air pollution• Cargo ships and pollution

Premature Deaths from Air Pollution in the U.S.

Laws and Regulations Can Reduce Outdoor Air Pollution (1) United States• Clean Air Acts: 1970, 1977, and 1990• Enforced by states and major cities

EPA • National ambient air quality standards (NAAQs)

for 6 outdoor criteria pollutants• CO, NO, SO2, suspended particulate matter, ozone,

and lead• Primary standards were set to protect human health• Secondary standards were set to prevent

environmental and property damage

• National emission standards for 188 hazardous air pollutants (HAPs)• Toxic Release Inventory (TRI)

Laws and Regulations Can Reduce Outdoor Air Pollution (2)

Good news in U.S.• Decrease in emissions• Use of low-sulfur diesel fuel• Cuts pollution

Developing countries• More air pollution• Still a major problem

Case Study: U.S. Air Pollution Laws Can Be Improved (1)

Rely on cleanup more than prevention of pollution

Raise fuel-efficiency for cars, SUVs, and light trucks• Far behind European Union, Japan, and China

Better regulation of emissions of motorcycles and two-cycle gasoline engines

Regulate air pollution for oceangoing ships in American ports

Case Study: U.S. Air Pollution Laws Can Be Improved (2)

Why are airports exempt from many regulations?

Regulate greenhouse gas emissions

Ultrafine particles are not regulated

Urban O3 levels too high

Case Study: U.S. Air Pollution Can Be Improved (3)

What about indoor air pollution?

Better enforcement of the Clean Air Acts• Local governments are not getting the federal

funding required to enforce these regulations Is intense pressure needed from citizens to

make improvements?

We Can Use the Marketplace to Reduce Outdoor Air Pollution

Emission trading or cap-and-trade program• Mixed reactions to program

• SO2 emissions down significantly

• NO2 will be tried in the future

There Are Many Ways to Reduce Outdoor Air Pollution

1980 –2006

• SO2 emissions from U.S. electric power plants decreased by 66%

• NOx emissions by 41%

• Particulate emissions by 28%

Older plants not governed by the same regulations

New cars have better emissions

Reducing Indoor Air Pollution Should Be a Priority

Greater threat to human health than outdoor pollution

What can be done? • Prevention• Cleanup

We Need to Put More Emphasis on Pollution Prevention

Output approaches• What can we do about the air pollutants we

produce? New shift to preventing outdoor and indoor

pollution• Pressure from citizens