Chapter 19 Air Pollution.

Chapter 19 Air Pollution

Core Case Study: South Asia’s Massive Brown Cloud

Case Study: South Asia’s Massive Brown Cloud
A huge dark brown cloud of industrial smog, caused by wood fires, cars, and coal-burning in countries such as China and India, stretches over much of southeastern Asia. In areas beneath the cloud, photosynthesis is reduced interfering with crop development. Fine particles and droplets in the cloud appear to be changing regional climates (including rainfall). May have contributed to floods in 2002 and 2005 which killed thousands of people in India & Bangladesh

China

India

Chapter Overview Questions
What layers are found in the atmosphere? What are the major outdoor air pollutants, and where do they come from? What are two types of smog? What is acid deposition, and how can it be reduced? What are the harmful effects of air pollutants? How can we prevent and control air pollution?

Case Study: When Is a Lichen Like a Canary?
Lichens can warn us of bad air because they absorb it as a source of nourishment. Figure 19-1

Core Case Study: When Is a Lichen Like a Canary?
Some lichen species are sensitive to specific air-polluting chemicals. After the Chernobyl nuclear power plant explosion (1986), more than 70,000 reindeer had to be killed because they ate highly radioactive lichens. Because lichens are widespread, long-lived, and anchored in place, they can help track pollution to its source.

STRUCTURE AND SCIENCE OF THE ATMOSPHERE
The atmosphere consists of several layers with different temperatures, pressures, and compositions. Figure 19-2

• Mesosphere • Stratosphere • Troposphere •Exosphere •Thermosphere
Atmospheric pressure (millibars) Temperature •Exosphere Pressure •Thermosphere Mesopause Heating via ozone • Mesosphere Altitude (miles) Altitude (kilometers) Stratopause • Stratosphere Figure 19.2 Natural capital: the earth’s atmosphere is a dynamic system that consists of four layers. The average temperature of the atmosphere varies with altitude (red line). Most UV radiation from the sun is absorbed by ozone (O3), found primarily in the stratosphere in the ozone layer 17–26 kilometers (10–16 miles) above sea level. QUESTION: How did living organisms lead to the formation of the ozone layer? Tropopause Ozone “layer” Heating from the earth • Troposphere Pressure = 1,000 millibars at ground level (Sea level) Temperature (˚C) Fig. 19-2, p. 440

STRUCTURE AND SCIENCE OF THE ATMOSPHERE
The atmosphere’s innermost layer (troposphere) is made up mostly of nitrogen (78%) and oxygen (21%), with smaller amounts of argon (0.93%) and CO2 (0.038% = 380 ppm), plus 0.01% to 4% water vapor. Ozone (03) in the atmosphere’s second layer (stratosphere) filters out 95% of the sun’s UV radiation that is harmful to us and most other species.

AIR POLLUTION Some primary air pollutants may react with one another or with other chemicals in the air to form secondary air pollutants (see below). Figure 19-3

Primary Pollutants Secondary Pollutants 3 Sources: Natural Stationary
NOx (NO & NO2) 3 Sources: SO3 Most hydrocarbons H2SO4 HNO3 Most suspended particles H2O2 O3 PANs Natural Most NO3– and SO42– salts Stationary Figure 19.3 Natural capital degradation: sources and types of air pollutants. Human inputs of air pollutants may come from mobile sources (such as cars) and stationary sources (such as industrial and power plants). Some primary air pollutants may react with one another or with other chemicals in the air to form secondary air pollutants. Mobile Fig. 19-3, p. 442

Major Air Pollutants Carbon oxides:
Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials (such as…?) 93% of carbon dioxide (CO2) in the troposphere occurs as a result of the natural carbon cycle. 7% of CO2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels). It is not regulated as a pollutant under the U.S. Clean Air Act.

Carbon Dioxide CO2 Concentration
280 ppm prior to the Industrial Revolution (about 275 years ago) 384 ppm in 2007 Increasing exponentially, currently by 2 ppm per year

Major Air Pollutants Nitrogen oxides and nitric acid:
Nitric oxide (NO) forms when nitrogen and oxygen gas in air react at the high-combustion temperatures in automobile engines and coal-burning plants. NO can also form from lightning and certain soil bacteria. NO reacts with O2 in the air to form NO2. NO2 reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3-) which are components of acid deposition. Together, NO (primary) and NO2 (secondary) are generically labeled as NOx

Major Air Pollutants Sulfur dioxide (SO2) and sulfuric acid:
About one-third of SO2 in the troposphere occurs naturally through the sulfur cycle. Two-thirds come from human sources, mostly combustion of sulfur-containing coal (S+ O2  SO2) and from oil refining and smelting of sulfide ores. SO2 in the atmosphere can be converted to sulfuric acid (H2SO4) and sulfate salts (SO42-) that return to earth as a component of acid deposition.

Major Air Pollutants Suspended particulate matter (SPM):
Consists of a variety of solid particles and liquid droplets small and light enough to remain suspended in the air. The most harmful forms of SPM are fine particles (PM-10), with an average diameter < 10 micrometers, and ultrafine particles (PM-2.5).

Major Air Pollutants Suspended particulate matter (SPM):
According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S. SPM can: irritate nose and throat, damage lungs, and aggravate asthma and bronchitis Toxic particles of lead, cadmium, and PCBs can cause mutations, birth defects, and cancer

Major Air Pollutants Ozone (O3):
Is a highly reactive gas that is a major component of photochemical smog. “Ground level” ozone is a strong oxidizer and damages living tissue when breathed. It can Cause and aggravate respiratory illness. Can aggravate heart disease. Damage plants, rubber in tires, fabrics, and paints.

Major Air Pollutants Volatile organic compounds (VOCs):
Most are hydrocarbons emitted by the leaves of many plants, and methane (CH4). About two thirds of global methane emissions comes from human sources. Other VOCs include industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride. Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.

Major Air Pollutants Radon (Rn):
Radon occurs naturally when Uranium-238 undergoes radioactive decay. Some types of soil and rock, such as granite, are relatively high in U-238 Radon can seep into homes and buildings sitting above these deposits of U-238 containing rocks.

URBAN OUTDOOR AIR POLLUTION
Industrial smog (“gray smog”) is a mixture of sulfur dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted mostly by burning coal. In most developed countries where coal and heavy oil is burned, industrial smog is not a problem due to reasonably good pollution control or with tall smokestacks that transfer the pollutant to rural areas.

Sunlight plus Cars Equals Photochemical Smog
Photochemical smog is a mixture of air pollutants formed by the reaction of nitrogen oxides (NOx) and volatile organic hydrocarbons (VOCs) under the influence of sunlight.

Sunlight plus Cars Equals Photochemical Smog
Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog. Figure 19-4

Factors Influencing Levels of Outdoor Air Pollution
Outdoor air pollution can be reduced by: settling out, precipitation, sea spray, winds, and chemical reactions. Outdoor air pollution can be increased by: urban buildings (slow wind dispersal of pollutants), mountains (promote temperature inversions), and high temperatures (promote photochemical reactions).

Temperature Inversion
Smoke rising in Lochcarron, Scotland is stopped by an overlying layer of warmer air.

Temperature Inversion

Denver: LA: Descending cold air mass Cooler air Inversion layer
Sea breeze Increasing altitude Figure 19.5 Natural capital degradation: two sets of topography and weather conditions that lead to prolonged temperature inversions, in which a warm air layer sits atop a cooler air layer. Air pollutants can build to harmful levels during an inversion. A temperature inversion can occur during cold, cloudy weather in a valley surrounded by mountains (left). Frequent and prolonged temperature inversions can also occur in an area with a sunny climate, light winds, mountains on three sides, and the ocean on the other (right). A layer of descending warm air from a high-pressure system prevents ocean-cooled air near the ground from ascending enough to disperse and dilute pollutants. Because of their topography, Los Angeles, California and Mexico City, Mexico (Figure 19-4) have frequent temperature inversions, many of them prolonged during the summer. QUESTION: Do you live in an area that suffers from fairly frequent thermal inversions? Decreasing temperature Denver: Cold, cloudy, surrounded by mountains LA: Hot, sunny, ocean on one side, mountains on 3 other sides Fig. 19-5, p. 447

Temperature Inversions
Cold, cloudy weather in a valley surrounded by mountains can trap air pollutants (left). Areas with sunny climate, light winds, mountains on three sides & an ocean on the other (right) are also susceptible to inversions. Figure 19-5

ACID DEPOSITION These trees look bad, but…

ACID DEPOSITION …the worst threat of acid deposition is to human health, when toxic metals such as lead & mercury are leached from soils into the water supply, where they threaten: Drinking water Food supplies via biomagnification

ACID DEPOSITION Primary pollutants: Sulfur dioxides (SO2), nitrogen oxides (NOx), and particulates can react in the atmosphere to produce… Secondary pollutants: acidic chemicals that can travel long distances before returning to the earth’s surface. H2SO4, HNO3, and SO42- and NO3- salts Tall smokestacks reduce local air pollution but can increase regional air pollution.

ACID DEPOSITION Acid deposition consists of rain, snow, dust, fog, dew, or gas with a pH lower than 5.6. Figure 19-6

Lakes in deep soil high in limestone are buffered
Wind Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Wet acid deposition (droplets of H2SO4 and HNO3 dissolved in rain and snow) Nitric oxide (NO) Sulfur dioxide (SO2) and NO Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Acid fog Farm Lakes in shallow soil low in limestone become acidic Ocean Figure 19.6 Natural capital degradation: acid deposition, which consists of rain, snow, dust, or gas with a pH lower than 5.6, is commonly called acid rain. Soils and lakes vary in their ability to buffer or remove excess acidity. Lakes in deep soil high in limestone are buffered Fig. 19-6, p. 448

ACID DEPOSITION pH measurements in relation to major coal-burning and industrial plants. Figure 19-7

Effects of Acid Deposition…
Dead or Severely Damaged Forests and Lakes, (especially in the Northeast US and Canada)

More Acid Deposition Damage

H2SO4 Sulfuric Acid Nitric Acid HNO3 SO2 NOx

Acid Rain in the US

Specific Effects of Acid Deposition in a Vermont Lake

Acid Deposition in Western Europe

Effects of Acid Rain on Stone Sculpture

This photo, from 1910, shows the effect of 400 years of weathering on a grotesque which decorates Lincoln Cathedral in England. In 1984, only 74 years later, acid rain and other atmospheric pollution have worn the figure to a barely recognizable remnant.

ACID DEPOSITION Contributes to chronic respiratory disease
Can leach toxic metals (such as lead and mercury) from soils and rocks into acidic lakes used as sources for drinking water.

ACID DEPOSITION Figure 19-8

ACID DEPOSITION Air pollution is one of several interacting stresses that can damage, weaken, or kill trees and pollute surface and groundwater. Figure 19-9

Emissions Lake Groundwater Acid deposition SO2 NOx H2O2 O3 PANs Others
Susceptibility to drought, extreme cold, insects, mosses, & disease organisms Direct damage to leaves & bark Reduced photo-synthesis and growth Soil acidification Tree death Figure 19.9 Natural capital degradation: air pollution is one of several interacting stresses that can damage, weaken, or kill trees and pollute surface and groundwater. Leaching of soil nutrients Release of toxic metal ions Root damage Reduced nutrient & water uptake Acids Lake Groundwater Fig. 19-9, p. 451

Solutions Acid Deposition Prevention Cleanup
Reduce air pollution by improving energy efficiency Add lime to neutralize acidified lakes $$$$$$$$$$$$$! Reduce coal use Increase natural gas use Add phosphate fertilizer to neutralize acidified lakes $$$$$$$$$$$$$! Increase use of renewable energy resources Burn low-sulfur coal Figure 19.10 Solutions: methods for reducing acid deposition and its damage. QUESTION: Which two of these solutions do you think are the most important? Remove SO2 particulates & NOx from smokestack gases (scrubbers) Remove NOx from motor vehicular exhaust Tax emissions of SO2 Fig , p. 452

INDOOR AIR POLLUTION Indoor air pollution usually is a greater threat to human health than outdoor air pollution. According to the EPA, the four most dangerous indoor air pollutants in developed countries are: Tobacco smoke. Formaldehyde (upholstery, paneling, particle board, carpet, and foam insulation) Radioactive radon-222 gas (natural- must be vented) Very small fine and ultrafine particles.

Tobacco Smoke Carbon Monoxide Methylene Chloride
Para-dichlorobenzene Chloroform Tetrachloroethylene TCE Formaldehyde 1, 1, 1- Trichloroethane Styrene Nitrogen Oxides Benzo-a-pyrene Particulates Tobacco Smoke Radon-222 Asbestos See p. 484 Carbon Monoxide Methylene Chloride

INDOOR AIR POLLUTION Household dust mites that feed on human skin and dust, live in materials such as bedding and furniture fabrics. Can cause asthma attacks and allergic reactions in some people. Figure 19-12

Case Study: Radioactive Radon
Radon-222, a radioactive, carcinogenic gas found in some soils and rocks, can seep into some houses and increase the risk of lung cancer. Radon comes from the radiactive decay of Uranium-238 Sources and paths of entry for indoor radon-222 gas. Next

Clothes dryer Sump pump Radon-222 gas
Outlet vents for furnaces and dryers Open window Openings around pipes Cracks in wall Slab joints Wood stove Cracks in floor Clothes dryer Sump pump Furnace Slab Radon-222 gas Uranium-238 Figure 19.13 Science: sources and paths of entry for indoor radon-222 gas. QUESTION: Have you tested the indoor air where you live for radon-222? (Data from U.S. Environmental Protection Agency) Soil Fig , p. 454

HEALTH EFFECTS OF AIR POLLUTION
Your respiratory system can help protect you from air pollution, but some air pollutants can overcome these defenses. Figure 19-14

Goblet cell (secreting mucus)
Epithelial cell Cilia Goblet cell (secreting mucus) Nasal cavity Oral cavity Pharynx (throat) Mucus Trachea (windpipe) Bronchioles Bronchus Alveolar duct Right lung Figure 19.14 Major components of the human respiratory system. Alveoli Alveolar sac (sectioned) Bronchioles Fig , p. 455

HEALTH EFFECTS OF AIR POLLUTION
Normal human lungs (left) and the lungs of a person who died of emphysema (right).

Air Pollution is a Big Killer
Each year, air pollution prematurely kills about 3 million people, mostly from indoor air pollution in developing countries. In the U.S., the EPA estimates that annual deaths related to indoor and outdoor air pollution range from 150,000 to 350,000. According to the EPA, each year more than 125,000 Americans get cancer from breathing diesel fumes.

Air Pollution is a Big Killer
Spatial distribution of premature deaths from air pollution in the United States. Figure 19-16

PREVENTING AND REDUCING AIR POLLUTION
The Clean Air Act (1970, ’77, ‘90) in the United States have greatly reduced outdoor air pollution from six major pollutants: Carbon monoxide CO Nitrogen oxides NOx Sulfur dioxides SO2 Suspended particulate matter (less than PM-10) Lead Pb Ozone O3

Environmental scientists point out several deficiencies in the Clean Air Act: The U.S. continues to rely on cleanup rather than prevention. The U.S. Congress has failed to increase fuel-efficiency standards for automobiles. Regulation of emissions from motorcycles and two-cycle engines remains inadequate. There is little or no regulation of air pollution from oceangoing ships in American ports.

PREVENTING AND REDUCING AIR POLLUTION- Deficiencies in the Clean Air Act of 1970
Airports are exempt from many air pollution regulations. The Act does not regulate the greenhouse gas CO2. The Act has failed to deal seriously with indoor air pollution. There is a need for better enforcement of the Clean Air Act.

Executives of companies claim that correcting these deficiencies would: cost too much harm economic growth and cost jobs.

Using the Marketplace to Reduce Outdoor Air Pollution
To help reduce SO2 emissions, the Clean Air Act authorized an emission trading (cap-and-trade) program. Enables the 110 most polluting power plants to buy and sell SO2 pollution rights. Between , the emission trading system reduced emissions. In 2002, the EPA reported the cap-and-trade system produced less emission reductions than were projected.

Solutions: Reducing Outdoor Air Pollution
There are a number of ways to prevent and control air pollution from coal-burning facilities. Electrostatic precipitator: are used to attract negatively charged particles in a smokestack into a collector. Wet scrubber: fine mists of water vapor trap particulates and convert them to a sludge that is collected and disposed of usually in a landfill.

Electrostatic Precipitator
Clean gas out Negatively charged electrode Positively charged precipitator wall Dirty gas (smoke) in Dust falls off into collector Figure 19.18 Solutions: an electrostatic precipitator (left) and a wet scrubber (right) are used to reduce SO2 and particulate emissions from coal-burning power and industrial plants. Taken to landfill Fig a, p. 460

Electrostatic Precipitator
Can remove 99% of particulate matter Does not remove hazardous ultrafine particles. Produces toxic dust that must be safely disposed of. Uses large amounts of electricity Figure 19-18

Wet Scrubber Clean gas out Separator Liquid water in
Dirty gas (smoke) in Polluted liquid (sludge) out Figure 19.18 Solutions: an electrostatic precipitator (left) and a wet scrubber (right) are used to reduce SO2 and particulate emissions from coal-burning power and industrial plants. Fig b, p. 460

Wet Scrubber Can remove 98% of SO2 and particulate matter.
Not very effective in removing hazardous fine and ultrafine particles. Figure 19-18

Stationary Source Air Pollution
Solutions Stationary Source Air Pollution Prevention Dispersion or Cleanup Burn low-sulfur coal Disperse emissions above thermal inversion layer with tall smokestacks Remove sulfur from coal Remove pollutants after combustion Convert coal to a liquid or gaseous fuel Figure 19.17 Solutions: methods for reducing emissions of sulfur oxides, nitrogen oxides, and particulate matter from stationary sources such as coal-burning electric power plants and industrial plants. QUESTION: Which two of these solutions do you think are the most important? Tax each unit of pollution produced Shift to less polluting fuels Fig , p. 459

In 2003, fourteen states and a number of U.S. cities sued the EPA to block new rules that would allow older coal-burning power plants to modernize without having to install the most advanced air pollution controls.

There are a number of ways to prevent and control air pollution from motor vehicles. Because of the Clean Air Act, a new car today in the U.S. emits 75% less pollution than did pre-1970 cars. There is an increase in motor vehicle use in developing countries and many have no pollution control devices and burn leaded gasoline.

Motor Vehicle Air Pollution
Solutions Motor Vehicle Air Pollution Prevention Cleanup Mass transit Emission control devices Bicycles and walking Less polluting engines Less polluting fuels Car exhaust inspections twice a year Improve fuel efficiency Figure 19.19 Solutions: methods for reducing emissions from motor vehicles. Go to to find out how dirty your car is. QUESTION: Which two of these solutions do you think are the most important? Get older, polluting cars off the road Give buyers large tax write-offs or rebates for buying low-polluting, energy efficient vehicles Stricter emission standards Fig , p. 460

Indoor Air Pollution Little effort has been devoted to reducing indoor air pollution even though it poses a much greater threat to human health than outdoor air pollution. Environmental and health scientists call for us to focus on preventing air pollution (especially indoor) in developing countries.

Use adjustable fresh air vents for work spaces
Solutions Indoor Air Pollution Prevention Cleanup or Dilution Cover ceiling tiles & lining of AC ducts to prevent release of mineral fibers Use adjustable fresh air vents for work spaces Increase intake of outside air Ban smoking or limit it to well ventilated areas Change air more frequently Set stricter formaldehyde emissions standards for carpet, furniture, and building materials Circulate a building’s air through rooftop green houses Figure 19.20 Solutions: ways to prevent and reduce indoor air pollution. QUESTION: Which two of these solutions do you think are the most important? Prevent radon infiltration Use exhaust hoods for stoves and appliances burning natural gas Use office machines in well ventilated areas Install efficient chimneys for wood-burning stoves Use less polluting substitutes for harmful cleaning agents, paints, and other products Fig , p. 461

• Do not buy furniture and other products containing formaldehyde.
What Can You Do? Indoor Air Pollution • Test for radon and formaldehyde inside your home and take corrective measures as needed. • Do not buy furniture and other products containing formaldehyde. • Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides. • Test your house or workplace for asbestos fiber levels and for any crumbling asbestos materials if it was built before 1980. • Don't live in a pre-1980 house without having its indoor air tested for asbestos and lead. • Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage. Figure 19.21 Individuals matter: ways to reduce your exposure to indoor air pollution. QUESTION: Which three of these actions do you think are the most important? • If you smoke, do it outside or in a closed room vented to the outside. • Make sure that wood-burning stoves, fireplaces, and kerosene- and gas-burning heaters are properly installed, vented, and maintained. • Install carbon monoxide detectors in all sleeping areas. Fig , p. 461

Improve energy efficiency to reduce fossil fuel use Reduce poverty
Solutions Air Pollution Outdoor Indoor Improve energy efficiency to reduce fossil fuel use Reduce poverty Distribute cheap & efficient cookstoves or solar cookers to poor families in developing countries Rely more on lower-polluting natural gas Rely more on renewable energy (especially solar cells, wind, & solar-produced hydrogen) Reduce or ban indoor smoking Figure 19.22 Solutions: ways to prevent outdoor and indoor air pollution over the next 30–40 years. QUESTION: Which two of these solutions do you think are the most important? Transfer technologies for latest energy efficiency, renewable energy, & pollution prevention to developing countries Develop simple and cheap tests for indoor pollutants such as particulates, radon, and formaldehyde Fig , p. 462

Updates Online The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at to access InfoTrac articles. InfoTrac: Indoor air pollution. Eva Rehfuess, Carlos Corvalan, Maria Neira. Bulletin of the World Health Organization, July 2006 v84 i7 p508(1). InfoTrac: Risks of cleaning house disclosed. San Jose Mercury News (San Jose, CA), May 23, 2006. InfoTrac: Pollution From Chinese Coal Casts Shadow Around Globe. Keith Bradsher, David Barboza. The New York Times, June 11, 2006 pA1(L). American Industrial Hygiene Association: Do I Work in a Sick Building? PBS: Deadly Smog EPA: Toxic Air Pollutants

Video: Air Pollution This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

Video: Smog Pollution This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. Should carbon dioxide be regulated as an air pollutant? a. No. Because funds are limited, they should be spent on regulating and reducing more toxic air pollutants, such as mercury. b. Yes. Carbon dioxide is a serious greenhouse gas and its emissions must be regulated and reduced.

How Would You Vote? To conduct an instant in-class survey using a classroom response system, access the “Polls Clicker Questions” from the PowerLecture main menu. Should the 1990 U.S. Clean Air Act be strengthened? a. No. Strengthening the Act would be too expensive and would harm the economy. b. Yes. Strengthening the Act would improve the environment and people's health, save energy, and ultimately save money.

How Would You Vote? To conduct an instant in-class survey using a classroom response system, access the “Polls Clicker Questions” from the PowerLecture main menu. Should emissions trading be used to help control emissions of all major air pollutants? a. No. Emissions trading has no system for verifying compliance and eliminating "hot spots" of air pollution. b. Yes. Emissions trading is an efficient and effective way of reducing air pollution.

How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment. Should older coal-burning power and industrial plants have to meet the same air pollution standards as new facilities? a. No. The private sector should not have to upgrade existing facilities every time the regulations change. b. Yes. All facilities should comply with current regulations so that the environment and human health are effectively protected.

Chapter 19 Air Pollution.

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