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302 Chapter 12 Air

C H A P T E R121 What Causes Air Pollution?

2 Air, Noise, and LightPollution

3 Acid Precipitation

Before you read this chapter,take a few minutes toanswer the following questions in your EcoLog.

1. Describe the air quality inyour area.

2. If there is air pollution inyour area, what do youthink causes it?

READING WARM-UP

Nagano, Japan, is just one of manycities around the world thatsuffers from unhealthy levels ofair pollution.

Copyright© by Holt, Rinehart and Winston. All rights reserved.

Section 1 What Causes Air Pollution? 303

In Mexico City, children rarely use the color blue when theymake paintings of the sky. This metropolitan area of 20 millionpeople is known as the most dangerous city in the world for chil-dren because of its very polluted air. When pollution levels arehigh, students are banned from playing outdoors until the emer-gency passes.

Clean air consists mostly of nitrogen and oxygen gas, as wellas very small amounts of argon, carbon dioxide, and water vapor.When harmful substances build up in the air to unhealthy levels,the result is Substances that pollute the air can be inthe form of solids, liquids, or gases.

Most air pollution is the result of human activities, but pol-lutants can also come from natural sources. A volcano, forexample, can spew clouds of particles and sulfur dioxide,SO2, into the atmosphere. Natural pollutants also include dust,pollen, and spores.

Primary and Secondary PollutantsA pollutant that is put directly into the air by human activity iscalled a An example of a primary pollutant issoot from smoke. Figure 1 shows some sources of primary air pol-lutants. form when a primary pollutantcomes into contact with other primary pollutants or with natu-rally occurring substances such as water vapor and a chemicalreaction takes place. An example of a secondary pollutant isground-level ozone. Ground-level ozone forms when the emissionsfrom cars, trucks, and natural sources react with the ultravioletrays of the sun and then mix with the oxygen in the atmosphere.

Secondary pollutants

primary pollutant.

air pollution.

Objectives� Name five primary air pollutants,

and give sources for each.� Name the two major sources of air

pollution in urban areas.� Describe the way in which smog

forms.� Explain the way in which a ther-

mal inversion traps air pollution.

Key Termsair pollutionprimary pollutantsecondary pollutantsmogtemperature inversion

S E C T I O N 1

What Causes Air Pollution?

Sources of Primary Air Pollutants in the U.S. (Per Day)

Emis

sio

ns

(in

th

ous

and

s o

f to

ns)

Electricity production Industry Transportation Other sources0

10

20

30

40

50

60

70

80

Source: U.S. Environmental Protection Agency.

Carbon monoxide (CO)

Nitrogen oxides (NOx)

Particulate matter (PM)

Sulfur oxides (SOx)

Volatile organic compounds (VOCs)

Figure 1 � Each day in the UnitedStates, hundreds of thousands oftons of polluting emissions that resultfrom human activity enter the air.


Sources of Primary Air Pollutants As shown in Table 1 above,household products, power plants, and motor vehicles aresources of primary air pollutants such as carbon monoxide,nitrogen oxide, sulfur dioxide, and chemicals called volatileorganic compounds (VOCs). Carbon monoxide gas is animportant component of the exhaust from vehicles. Vehicles arealso a major source of nitrogen oxide emissions. Coal-burningpower plants are another source of nitrogen oxide. Sulfur diox-ide gases are formed when coal and oil, which contain sulfur,are burned. Power plants, refineries, and metal smelters con-tribute much of the sulfur dioxide emissions to the air. Vehiclesand gas station spillage make up most of the human-madeemissions of volatile organic compounds. VOCs are also foundin many household products.

Particulate matter can also pollute the air and is usuallydivided into fine and coarse particles. Fine particles enter the airfrom fuel burned by vehicles and coal-burning power plants.Sources of coarse particles are cement plants, mining operations,incinerators, wood-burning fireplaces, fields, and roads.

304 Chapter 12 Air

Primary Air Pollutants

Pollutant Description Primary Sources Effects

Particulates can form clouds thatreduce visibility and cause a variety ofrespiratory problems. Particulates havealso been linked to cancer. They mayalso corrode metals and erodebuildings and sculptures.

Most particulates comefrom construction,agriculture, forestry, andfires. Vehicles andindustrial processes alsocontribute particulates.

Particulates are tinyparticles of liquid orsolid matter.

Particulatematter(particulatesor PM)

VOCs contribute to smog formationand can cause serious healthproblems, such as cancer. They mayalso harm plants.

VOCs come from burningfuels. Vehicles are a majorsource of VOCs.

VOCs are organicchemicals thatvaporize readily andform toxic fumes.

Volatileorganiccompounds(VOCs)

SO2 contributes to acid precipitationas sulfuric acid. Secondary pollutantsthat result from reactions with SO2

can harm plant life and irritate therespiratory systems of humans.

SO2 comes mostly fromburning fossil fuels.

SO2 is produced bychemical interactionsbetween sulfur andoxygen.

Sulfurdioxide (SO2)

NOx can make the body vulnerable torespiratory infections, lung diseases,and cancer. NOx contributes to thebrownish haze seen over cities and toacid precipitation.

NOx comes from burningfuels in vehicles, powerplants, and industrialboilers.

When combustion(burning) temperaturesexceed 538°C, nitrogenand oxygen combine toform nitrogen oxides.

Nitrogenoxides (NOx)

CO interferes with the blood’s abilityto carry oxygen, slowing reflexes andcausing drowsiness. In highconcentrations, CO can cause death.

Sources of CO are cars,trucks, buses, smallengines, and someindustrial processes.

CO is an odorless,colorless, poisonous gas.It is produced by theincomplete burning offossil fuels.

Carbonmonoxide(CO)

Table 1 �

www.scilinks.orgTopic: Air PollutionSciLinks code: HE4003


The History of Air PollutionAir pollution is not a new phenomenon. Whenever somethingburns, pollutants enter the air. Two thousand years ago, Seneca, aRoman philosopher and writer, complained about the foul air inRome. In 1273, England’s King Edward I ordered that burning aparticularly dirty kind of coal called sea-coal was illegal. One manwas even hanged for disobeying this medieval “clean air act.”

The world air-quality problem is much worse today becausemodern industrial societies burn large amounts of fossil fuels. Asshown in Figure 2, most air pollution in urban areas comes frommotor vehicles and industry.

Motor Vehicle EmissionsAlmost one-third of our air pollution comes from gasoline

burned by vehicles. According to the U.S. Department ofTransportation, Americans drove their vehicles over 2.6 trillionmiles in 1998. Over 90 percent of that mileage was driven bypassenger vehicles. The rest was driven by trucks and buses.

Controlling Vehicle Emissions The Clean Air Act, passed in 1970and strengthened in 1990, gives the Environmental ProtectionAgency (EPA) the authority to regulate vehicle emissions in theUnited States. The EPA required the gradual elimination of lead ingasoline, and as a result, lead pollution has been reduced by morethan 90 percent in the United States. In addition, catalytic con-verters, which are required in automobiles, clean exhaust gases ofpollutants before the pollutants are able to exit the tailpipe. TheEPA estimates that cars and trucks today burn fuel 35 percentmore efficiently and with 95 percent fewer emissions of pollutants,excluding carbon dioxide, than they did 30 years ago.

Section 1 305

Figure 2 � The refinery shown inthis photograph is a source of volatileorganic compounds. The tanker truckin the foreground is emitting nitrousoxide into the atmosphere.

LawConnection to

Off with His Head! Around1300 CE, King Edward II ofEngland forbade the burning ofcoal while Parliament was in ses-sion. “Be it known to all withinthe sound of my voice,” KingEdward II said, “whosoever shallbe found burning coal shall sufferthe loss of his head.”

GeofactSea-Coal In 12th-century London,wood was becoming too scarceand too expensive to use as a fuelsource. Large deposits of coalcalled sea-coal that are found offthe northeast coast of Englandprovided a plentiful alternative.However, this soft coal did notburn efficiently. The sea-coal pro-duced mostly smoke and notmuch heat. The smoke from thecoal emanated from Londonhomes and factories and combinedwith fog to produce smog.


306 Chapter 12 Air

MATHPRACTICEUtility Incentives for Zero-emission Vehicles The Los Angeles Departmentof Water and Power provides discounts of $0.025 per kilowatthour (kWh) for electricity used torecharge electric vehicles. If theenergy charge per kWh is $0.02949and you use 150 kWh hours ofelectricity per month to rechargeyour vehicle, how much moneywould you save on your electric billeach month? each year? How muchwould you save if you had threeelectric cars?

Interior� Car seats may be covered in plastic that contains a volatile organic compound called vinyl chloride.

� Each time an air conditioner is installed in a car, 1.1 kg (2.5 lb) of chlorofluorocarbons (CFCs) are released into the air. Each time an air conditioner is recharged, 0.5 kg (1 lb) of CFCs are released.

Body and Frame� Steel smelters send thousands of metrictons of sulfur dioxide into the air eachyear.

� Many auto factories in Mexico,Eastern Europe, and some Asiancountries lack pollution-con-trol devices.

Fuel Tank� When filling the car withgasoline, VOCs escape intothe atmosphere.

Exhaust� Car exhaust is a major source of nitrogen oxides,carbon monoxide, and hydrocarbons.

� In developing countries, car exhaust may contain over a thousand poisonous substances.

� Each car releases 4.5 metric tons

(5 tons) of carbon dioxideevery year.

Figure 3 � The catalyst material ina catalytic converter (top) causes achemical reaction that changesexhaust emissions to less harmfulsubstances. The bottom illustrationshows a car’s contribution to air pollution.

California Zero-Emission Vehicle Program In 1990, theCalifornia Air Resources Board established the zero-emission vehi-cle (ZEV) program. Zero-emission vehicles are vehicles that haveno tailpipe emissions, no emissions from gasoline, and no emis-sion-control systems that deteriorate over time. Figure 3 illustratesthe catalytic converter emission-control system that is in use todayas well as the ways an automobile contributes to air pollution.

By the year 2016, 16 percent of all vehicles sold in Californiaare required to be zero-emission vehicles. This requirementincludes sports utility vehicles (SUVs), trucks, small vans, andautomobiles. At present, ZEVs such as electric vehicles are for salein California, and vehicles with advanced batteries are beingdemonstrated by the major automakers. Vehicles powered byhydrogen fuel are being developed and will qualify as zero-emissionvehicles. Partial zero-emissions vehicles are also included in the pro-gram. These vehicles include hybrid-electric cars and cars poweredby methanol fuel cells. Zero-emission vehicle programs have alsobeen adopted by Maine, Massachusetts, New York, and Vermont.


Industrial Air PollutionMany industries and power plants that generate our electricitymust burn fuel to get the energy they need. They usually burnfossil fuels. Burning fossil fuels releases huge quantities of sulfurdioxide and nitrogen oxide into the air. Power plants that pro-duce electricity emit at least two-thirds of all sulfur dioxide andmore than one-third of all nitrogen oxides that pollute the air.

Some industries also produce VOCs, which are chemical com-pounds that form toxic fumes. As shown in Figure 4, some of thechemicals used in dry cleaning are sources of VOCs. Oil refiner-ies, chemical manufacturing plants, furniture refinishers, andautomobile repair shops also contribute to the VOCs in the air.When people use some of the products that contain VOCs,more VOCs are added to the air.

Regulating Air Pollution From Industry The Clean Air Actrequires many industries to use scrubbers or other pollution-con-trol devices. Scrubbers remove some of the more harmful sub-stances that would otherwise pollute the air. A scrubber, asshown in Figure 5, is a machine that moves gases through a sprayof water that dissolves many pollutants. Ammonia is an exampleof a pollutant gas that can be removed from the air by a scrubber.

Electrostatic precipitators are machines used in cement factoriesand coal-burning power plants to remove dust particles from smoke-stacks. In an electrostatic precipitator, gas containing dust particles isblown through a chamber containing an electrical current. An elec-trical charge is transferred to the dust particles, which causes themto stick to one another and the sides of the chamber. The clean gas isreleased from the chamber, and the concentrated dust particles canthen be collected and removed. Electrostatic precipitators remove22 million metric tons (20 million tons) of ash generated by coal-burning power plants from the air each year in the United States.

Section 1 What Causes Air Pollution? 307

Figure 4 � In 1996, the federal gov-ernment established standards toreduce emissions of VOC-producingchemicals used in dry cleaning.

EcofactAir Pollution’s Impact on BirdsScientists in Finland have docu-mented the effects of harmfulemissions from a copper smelter inFinland on two species of birdsthat live nearby. The two speciesof birds respond differently to thepollutants containing heavy metalsand acidic substances. One speciesappears to suffer directly from thetoxic effects of the pollutants. Theother species suffers because theamount of insect food for itsnestlings has been reduced. Whenheavy metal emissions from thesmelter decreased, a rapidimprovement in breeding successand decrease in the heavy metalfound in the bones of nestlingswas observed.

Figure 5 � Scrubbers work by spray-ing gases with water, which removesmany pollutants.


Smog When air pollution hangs over urban areas and reduces visi-bility, it is called As you can see in Figure 6, smog results fromchemical reactions that involve sunlight, air, automobile exhaust,and ozone. Pollutants released by vehicles and industries are themain causes of smog. Los Angeles, California, Denver, Colorado,and Phoenix, Arizona, are examples of cities that have smog.

Temperature Inversions The circulation of air in the atmosphereusually keeps air pollution from reaching dangerous levels. Duringthe day, the sun heats the surface of the Earth and the air near theEarth. The warm air rises through the cooler air above and carriespollutants away from the ground and into the atmosphere.

Sometimes, however, pollution is trapped near the Earth’s sur-face by a temperature inversion. Usually, air temperatures decreasewith height, but in an area with a the airabove is warmer than the air below. Figure 7 shows how a tem-perature inversion traps pollutants near the Earth’s surface. Thewarmer air above keeps the cooler air at the surface from movingupward. So, pollutants are trapped below with the cooler air. If acity is located in a valley, the city has a greater chance of experi-encing temperature inversions. Los Angeles, which is surroundedon three sides by mountains, often has temperature inversions thattrap smog in the city.

temperature inversion,

smog.

1. Name five primary air pollutants, and give importantsources for each.

2. Name the two major sources of air pollution in urban areas.

3. Describe the way in which smog forms.

4. Define the term temperature inversion. Explain howtemperature inversion traps pollutants near Earth’ssurface.

CRITICAL THINKING5. Making Decisions Read the passage on the

California Zero-Emission Vehicle Program. Shouldautomobile makers be made to adhere to quotas ofzero-emission vehicles set by states, even if the quotacauses automakers to lose revenue?

6. Analyzing Relationships Can you think of anyother possible type of pollution-control device thatcould be used to remove particulates from smokestacksin a manner similar to an electrostatic precipitator?

READING SKILLS

S E C T I O N 1 Review

Figure 6 � The diagram belowshows how smog is formed. Largecities with dry, sunny climates andmillions of automobiles often sufferfrom smog.

Solarradiation

Normal situation

Cooler air

Cool air

Warm air

Escapingpollutants

Cool air

Warm inversionlayer

Cool air

Temperature inversion

Solarradiation Trapped

pollutants

Figure 7 � Normal air circulationis shown at left, whereas a tempera-ture inversion, in which pollutantsare trapped near the Earth’s surface,is shown at right.

308 Chapter 12 AirCopyright© by Holt, Rinehart and Winston. All rights reserved.

Section 2 Air, Noise, and Light Pollution 309

Air pollution can cause serious health problems. People who arevery young or very old and people who have heart or lung prob-lems can be most affected by air pollutants. Decades of researchhave shown convincing evidence linking air pollution to disease.But because pollution adds to the effects of existing diseases, nodeath certificates list the cause of death as air pollution. Instead,diseases such as emphysema, heart disease, and lung cancer arecited as causes of death. The American Lung Association has esti-mated that Americans pay tens of billions of dollars a year inhealth costs to treat respiratory diseases caused by air pollution.

Short-Term Effects of Air Pollution on HealthMany of the effects of air pollution on people’s health are short-term and are reversible if their exposure to air pollution decreases.The short-term effects of air pollution on people’s health includeheadache; nausea; irritation to the eyes, nose, and throat; tightnessin the chest; coughing; and upper respiratory infections, such asbronchitis and pneumonia. Pollution can also make the conditionof individuals who suffer from asthma and emphysema worse.

Long-Term Health Effects of Air PollutionLong-term effects on health that have been linked to air pollutioninclude emphysema, lung cancer, and heart disease. Long-termexposure to air pollution may worsen medical conditions sufferedby older people and may damage the lungs of children.

Objectives� Describe three possible short-term

effects and long-term effects of airpollution on human health.

� Explain what causes indoor air pol-lution and how it can be prevented.

� Describe three human health prob-lems caused by noise pollution.

� Describe solutions to energy wastecaused by light pollution.

Key Termssick-building syndromeasbestosdecibel (dB)

S E C T I O N 2

Air, Noise, and Light Pollution

Figure 8 � This police officer wearsa smog mask as he directs traffic inBangkok, Thailand.

www.scilinks.orgTopic: Respiratory DisordersSciLinks code: HE4094


Indoor Air PollutionThe quality of air inside a home or a building is sometimes worsethan the quality of the air outside. Plastics and other industrialchemicals are major sources of pollution. These compounds canbe found in carpets, building materials, paints, and furniture, par-ticularly when these items are new. Figure 9 shows examples ofsome indoor air pollutants.

Buildings that have very poor air quality have a conditioncalled Sick-building syndrome is mostcommon in hot places where buildings are tightly sealed to keepout the heat. In Florida, for example, a new, tightly sealed countycourthouse had to be abandoned. Half of the people who workedthere developed allergic reactions to fungi that were growing inthe air-conditioning ducts, ceiling tiles, carpets, and furniture.

Identifying and removing the sources of indoor air pollutionis the most effective way to maintain good indoor air quality.Ventilation, or mixing outdoor air with indoor air, is also neces-sary for good air quality. When activities such as renovation andpainting, which cause indoor air pollution, are undertaken, venti-lation should be increased.

sick-building syndrome.

310 Chapter 12 Air

The Health Effects of Ground-Level Ozone

You have learned that the ozonelayer in the stratosphere shields theEarth from the harmful effects ofultraviolet radiation from the sun.At the surface of the Earth, how-ever, ozone is a human-made airpollutant that at certain concentra-tions may affect human health.

Ozone forms from the reaction ofvolatile organic compounds (VOCs)and nitrogen oxides (NOx) in thepresence of heat and sunlight. Highconcentrations of ozone form in theatmosphere on sunny days that havehigh temperatures in the late spring,summer, and early fall. The sources ofVOCs and NOx emissions are largelymotor vehicles, power plants, gaso-line vapors, and chemical solvents.Most ozone pollution forms in urban

ChemistryConnection to

Formaldehyde Formaldehyde isa colorless gas that has a strongodor. It is a very common indus-trial and commercial chemicalthat is used to make buildingmaterials and household prod-ucts. In the home, significantamounts of formaldehyde arefound in adhesives in plywood,particle board, furniture, and car-pet. Other sources of formalde-hyde may be foam insulation, gasstoves, tobacco smoke, and dry-cleaned clothing. The healtheffects of formaldehyde mayinclude eye irritation, burningsensations in the throat, nausea,and difficulty breathing.

� Children who engage in vigorousoutdoor activities where pollutantconcentrations are often high mayhave a greater risk of developingasthma or other respiratory illnesses.

and suburban areas. However, pollu-tants may be transported hundredsof kilometers from their source.

As ozone concentrations in theatmosphere increase, greater num-bers of people may experienceharmful health effects of ozone onthe lungs. Some of the short-termeffects of ozone on health includeirritation of the respiratory system,a reduction in lung function, theaggravation of asthma, and inflam-mation to the lining of the lungs.Scientists believe that ozone may

have other damaging effects onhuman health. Lung diseases suchas bronchitis and emphysema maybe aggravated by ozone. Scientists



believe that permanent lung injurymay result from repeated short-term exposure to ozone pollution.Children who are regularly exposedto high concentrations of ozone

Those who are most at riskfrom ozone include children, adultswho exercise or work outdoors,older people, and people who sufferfrom respiratory diseases. In addi-tion, there are some healthy individ-uals who have unusually highsusceptibility to ozone.

CRITICAL THINKING

1. Making Decisions Write a briefparagraph explaining whether ornot lung-function tests should bemandatory for children who live inurban areas where high concentra-tions of ozone are frequent.

2. Making Decisions If lung-function tests become mandatory,who will pay for these tests, and whowill provide the equipment? Wouldthese tests be performed at school,in a doctor’s office, or at a hospital?

WRITING SKILLS

may have reduced lung function asadults. Exposure to ozone may alsoaccelerate the natural decline inlung function that is part of theaging process.

� A therapist performs a lung-function test on a patient by usinga machine that measures various aspects of lung function.

Figure 9 � Someindoor air pollutantsand their sources areshown here.


Radon Gas Radon gas is colorless, tasteless, and odorless. It isalso radioactive. Radon is one of the elements produced by thedecay of uranium, a radioactive element that occurs naturally inthe Earth’s crust. Radon can seep through cracks and holes infoundations into homes, offices, and schools, where it adheres todust particles. When people inhale the dust, radon enters theirlungs. In the lungs, radon can destroy the genetic material in cellsthat line the air passages. Such damage can lead to cancer, espe-cially among people who smoke. Radon is the second-leadingcause of lung cancer in the United States.

Asbestos Several minerals that form in long, thin fibers andthat are valued for their strength and resistance to heat are

called Asbestos is primarily used as an insula-tor and as a fire retardant, and it was used exten-

sively in building materials. The U.S.government banned the use of most asbestos

products in the early 1970s. Exposure toasbestos in the air is dangerous. Asbestosfibers that are inhaled can cut and scar thelungs, which causes the disease asbestosis.Victims of the disease have more and more

difficulty breathing and may eventually dieof heart failure. Schools in the United States

have taken this threat seriously. Billions of dol-lars have been spent to remove asbestos from school

buildings. Figure 10 shows asbestos fibers and asbestosremoval from a building.

Noise PollutionA sound of any kind is called a noise. However, some noises areunnecessary and can cause noise pollution. Noise is a pollutantthat affects human health and the quality of human life.Airplanes, construction equipment, city traffic, factories, homeappliances, and lawnmowers are some of the examples of thingsthat make unnecessary sounds that commonly travel through theair. Health problems that can be caused by noise pollution includeloss of hearing, high blood pressure, and stress. Noise can alsocause loss of sleep, which may lead to decreased productivity atwork and in the classroom.

The intensity of sound is measured in units calledThe lowest point on the decibel scale is 0 dB and the highest pointis 180 dB. For each increase in decibel intensity, the decibel level is10 times higher than the previous level. For example, 20 dB is 10times the intensity of 10 dB, 30 dB is 100 times the intensity of 10dB, and 40 dB is 1,000 times the intensity of 10 dB. Table 2 showsthe intensity of some common sounds. A sound of 120 dB is at thethreshold of pain. Permanent deafness may come as a result of con-tinuous exposure to sounds over 120 dB.

decibels (dB).

asbestos.

312 Chapter 12 Air

Figure 10 �Asbestos (right) formsin long, thin fibers. Theworker above is removingdebris from a structure that wasbuilt with asbestos.

Intensity of Common Noises

Noise Intensity (dB)

Rocket engine 180

Jet engine 140

Rock-and-rollconcert 120

Car horn 110

Chainsaw 100

Lawnmower 90

Doorbell 80

Conversation 60

Whisper 30

Faintest sound heard by thehuman ear 0

Table 2 �


Light PollutionUnlike air or water pollution, light pollution does not present adirect hazard to human health. However, light pollution does nega-tively affect our environment. The use of inefficient lighting inurban areas is diminishing our view of the night sky. In urban areas,the sky is often much brighter than the natural sky.

A more important environmental concern of inefficient light-ing is energy waste. For example, energy is wasted when light isdirected upward into the night sky and lost to space, as shown inFigure 11. Examples of inefficient lighting are billboards andother signs that are lit from below, the lighting of building exteri-ors, and poor-quality street lights. One solution to energy wasteincludes shielding light so it is directed downward. Using timecontrols so that light is used only when needed and using low-pressure sodium sources—the most energy-efficient source oflight—wherever possible are two other solutions.


1. Describe the long-term effects and the short-termeffects of air pollution on health.

2. Describe two ways in which indoor air pollution canbe prevented.

3. Describe some of the human health problemscaused by noise pollution.

4. Describe several solutions to the energy waste asso-ciated with light pollution.

CRITICAL THINKING5. Making Comparisons Read the descriptions of

noise and light pollution in this section. Explain waysin which noise pollution and light pollution are similarand ways they are different.

6. Analyzing Relationships Molds can grow in new,tightly sealed buildings where the humidity is high andthe ventilation is poor. Explain how you would controlthe growth of mold in this type of environment.

READING SKILLS


Figure 11 � This view of Seattleshows how lighting in urban areascan cause skyglow, which is an effectof light that can dramatically reduceour view of the night sky.

FIELD ACTIVITY FIELD ACTIVITY Light Pollution At night, inyour neighborhood or from yourfront porch, note any efficient orinefficient uses of light that yousee, and write down your obser-vations in your EcoLog.


314 Chapter 12 Air

Imagine that you are hiking through the forests of the AdirondackMountains in New York. You come to a lake and sit down to rest.You are amazed at how clear the water is; it is so clear that youcan see the bottom of the lake. But after a few minutes you feeluneasy. Something is wrong. What is it? Suddenly, you realize thatthe lake has no fish.

What Causes Acid Precipitation?This lake and thousands of lakes throughout the world are vic-tims of acid precipitation, which is also known as acid rain.

is precipitation such as rain, sleet, or snowthat contains a high concentration of acids. When fossil fuelsare burned, they release oxides of sulfur and nitrogen. Whenthe oxides combine with water in the atmosphere, they formsulfuric acid and nitric acid, which fall as acid precipitation.This acidic water flows over and through the ground, and intolakes, rivers, and streams. Acid precipitation can kill livingthings, and can result in the decline or loss of some local ani-mal and plant populations.

A (power of hydrogen) number is a measure of how acidicor basic a substance is. A pH scale is shown in Figure 12. As youcan see from the scale, the lower the pH number is, the moreacidic a substance is; the higher a pH number is, the more basic a substance is. Each whole number on the pH scale indicates a tenfold change in acidity.

pH

Acid precipitation

Objectives� Explain the causes of acid precipi-

tation.� Explain how acid precipitation

affects plants, soils, and aquaticecosystems.

� Describe three ways that acid pre-cipitation affects humans.

� Describe ways that countries areworking together to solve theproblem of acid precipitation.

Key Termsacid precipitationpHacid shock

S E C T I O N 3

Acid Precipitation

Increasing acidity Increasing basicity

1 2 3 4

4.0

5 6

6.0

8 10 11 129

3.5 5.0

Acid rain(extreme)

Acid rain(average) Rain

Human saliva

Tap water

Householdammonia

Seawater

Humanblood

Tomatojuice

Carbonatedsoftdrink DetergentsMilk

Lemonjuice Vinegar

7

Figure 12 � The pH scale measureshow basic or how acidic a substanceis. Below are the pH measurementsof some common substances.


Pure water has a pH of 7.0. Normal precipitation is slightlyacidic, because atmospheric carbon dioxide dissolves into the pre-cipitation and forms carbonic acid. Normal precipitation has apH of about 5.6. Precipitation is considered acid precipitation ifit has a pH of less than 5.0. Figure 13 shows how acid precipita-tion forms.

The pH of precipitation varies between different geographicareas. For example, Eastern Europe and parts of Scandinavia haveprecipitation with a pH of 4.3 to 4.5, whereas the remainder ofEurope has precipitation with pH values of 4.5 to 5.1. The pH ofprecipitation in the eastern United States and Canada ranges from4.2 to 4.8. The most acidic precipitation in North America occursaround Lake Erie and Lake Ontario. It has a pH of 4.2.

How Acid Precipitation Affects Soils and PlantsPlant communities have adapted over long periods of time to theacidity of the soil in which they grow. Acid precipitation cancause a drop in the pH of soil and water. This increase in theconcentration of acid is called acidification. Acidification changesthe balance of a soil’s chemistry in several ways. When the acidityof soil increases, some nutrients are dissolved and washed awayby rainwater. Increased acidity causes aluminum and other toxicmetals to be released and possibly absorbed by the roots of plants.Aluminum also causes root damage. Sulfur dioxide in water vaporclogs the openings on the surfaces of plants. Figure 14 shows theharmful effects of acid precipitation on trees.

Section 3 Acid Precipitation 315

OzoneO3

Oxygen atomO

OH

Acid precipitation

combines withSO2 + O2

combines withNO2

Sulfuric acidH2SO4

Nitric acidHNO3

Figure 13 � Sulfur oxides and nitro-gen oxides combine with water in theatmosphere to form sulfuric and nitricacids. Rainfall that contains theseacids is called acid precipitation.

Figure 14 � The trees in this forestin Poland show the dramatic effectthat acid precipitation can have onplants. Damage to more than 16 mil-lion acres in nine European countrieshas been linked to acid precipitation.


QuickLABNeutralizing Acid PrecipitationProcedure1. Pour 1/2 Tbsp of vinegar into

one cup of distilled water,and stir the mixture well.Check the pH of the mixtureby using pH paper. The pHshould be about 4.

2. Crush one stick of blackboardchalk into a powder. Pour thepowder into the vinegar andwater mixture. Check the pH ofthe mixture.

Analysis1. Did the vinegar and water mix-

ture become more or less acidicafter the powdered chalk waspoured in?

Acid Precipitation and Aquatic EcosystemsAquatic animals are adapted to live in an environment with aparticular pH range. If acid precipitation falls on a lake andchanges the water’s pH, acid can kill aquatic plants, fish, andother aquatic animals. The change in pH is not the only thingthat kills fish. Acid precipitation causes aluminum to leach out ofthe soil surrounding a lake. The aluminum accumulates in thegills of fish and interferes with oxygen and salt exchange. As aresult, fish are slowly suffocated.

The effects of acid precipitation are worst in the spring, whenacidic snow that accumulated in the winter melts and rushes intolakes and other bodies of water. This sudden influx of acidic waterthat causes a rapid change in the water’s pH is calledThis phenomenon causes large numbers of fish in a population todie, as shown in Figure 15. Acid shock also affects the reproduc-tion of fish and amphibians. They produce fewer eggs, and theseeggs often do not hatch. The offspring that do survive often havebirth defects and cannot reproduce.

To counteract the effects of acid precipitation on aquaticecosystems, some states in the United States and some countriesspray powdered lime (calcium carbonate) on acidified lakes in thespring to help restore the natural pH of the lakes. Because limehas a pH that is basic, the lime raises the pH of the water.Unfortunately, enough lime cannot be spread to offset all aciddamage to lakes.

Acid Precipitation and HumansAcid precipitation can affect humans in a variety of ways. Toxicmetals such as aluminum and mercury can be released into theenvironment when soil acidity increases. These toxic metals canfind their way into crops, water, and fish. The toxins then poisonthe human body.

Acid precipitation can lead to other human health prob-lems. Research has indicated that there may be a correlationbetween large amounts of acid precipitation received by a com-munity and an increase in respiratory problems in the commu-nity’s children.

The standard of living of some people is affected by acidprecipitation. Decreases in numbers of fish caused by the acidifi-cation of lakes and streams can influence the livelihood of com-mercial fisherman and people involved in the sport-fishingindustry. Forestry is also affected when trees are damaged byacid precipitation.

Acid precipitation can dissolve the calcium carbonate incommon building materials, such as concrete and limestone.Some of the world’s most important and historic monuments,including those made of marble, are being affected by acid pre-cipitation. For example, sulfur dioxide has caused black cruststo form on the carbonate stones of historic Greek monuments.

acid shock.

316 Chapter 12 Air

Figure 15 � Fish are vulnerable toacid shock, a sudden influx of acidicwater into a lake or stream thatcauses a rapid change in pH.


International Conflict and CooperationOne problem in controlling acid precipitation is that pollutantsmay be released in one geographical area and fall to the groundhundreds of kilometers away. For example, almost half of theacid precipitation that falls in southeastern Canada results frompollution produced in Ohio, Indiana, Pennsylvania, Illinois,Missouri, West Virginia, and Tennessee. Figure 16 shows areas ofthe world that produce pollutants and areas which are thenaffected by acid precipitation.

Because acid precipitation falls downwind, the problem of solv-ing acid precipitation has been difficult, especially on the interna-tional level. In the spirit of cooperation, Canada and the UnitedStates signed the Canada–U.S. Air Quality Agreement in 1991.Both countries agreed to reduce acidic emissions that flowed acrossthe Canada–U.S. boundary. More international agreements such asthis may be necessary to control the acid-precipitation problem.

Section 3 Acid Precipitation 317

1. Explain how acid precipitation forms.

2. Describe the harmful effects that acid precipitationcan have on plants, soils, and aquatic ecosystems.

3. Describe three ways in which acid precipitation canaffect humans.

4. Describe a way in which countries are workingtogether to solve the problem of acid precipitation.

CRITICAL THINKING5. Inferring Relationships In addition to negatively

affecting forestry and the fishing industry, howmight acid precipitation affect local economies?

6. Analyzing Viewpoints Write a short essay inwhich you discuss whether or not a country thatreleases significant amounts of pollutants into the airthat fall as acid precipitation in another countryshould be expected to pay some of the costs ofcleanup. WRITING SKILLS


www.scilinks.orgTopic: Acid RainSciLinks code: HE4001

Figure 16 � Acid precipitation is aglobal problem.


HighlightsC H A P T E R 12

1 What Causes Air Pollution?

2 Air, Noise, and Light Pollution

3 Acid Precipitation

318 Chapter 12 Highlights

Key Termsair pollution, 303primary pollutant,

303secondary pollutant,

303smog, 308temperature

inversion, 308

Main Ideas� Primary pollutants are pollutants put directlyin the air by human activity.

� Secondary pollutants are formed when a pri-mary pollutant comes into contact with otherprimary pollutants or with naturally occurringsubstances and a chemical reaction takes place.

� Most air pollution comes from vehicles andindustry.

� Air pollution that hangs over cities andreduces visibility is called smog.

� Pollution can be trapped near the surface ofthe Earth by a condition known as temperatureinversion.

sick-buildingsyndrome, 310

asbestos, 312decibel (dB), 312

� Air pollution may have both long- and short-term effects on human health.

� The air indoors may be more polluted thanthe air outside. Plastics, cleaning chemicals,and building materials are major sources ofindoor air pollution.

� Noise is a pollutant that affects humanhealth and the quality of life.

� Inefficient lighting diminishes our view of thenight sky and wastes energy.

acid precipitation,314

pH, 314acid shock, 316

� Acid precipitation is precipitation such asrain, sleet, or snow that contains a high con-centration of acids.

� Acid shock occurs when a sudden influx ofacidic water enters a lake or stream and causesa rapid change in pH that harms aquatic life.

� Pollutants released in one geographical areamay fall to the ground hundreds of kilometersaway as acid precipitation—sometimes inanother country.


Using Key TermsUse each of the following terms in a sentence.

1. air pollution2. smog3. temperature inversion4. sick-building syndrome5. pH

For each pair of terms, explain how the meaningsof the terms differ.

6. primary pollutant and secondary pollutant7. asbestos and radon8. pH and acid precipitation9. acidification and acid shock

Understanding Key Ideas10. Which of the following air pollutants is not

a primary pollutant?a. particulate matterb. ozonec. sulfur dioxided. volatile organic compounds

11. A device used to clean exhaust gases beforethey exit an automobile’s tailpipe is called a(n)a. electrostatic precipitator.b. catalytic converter.c. scrubber.d. None of the above

12. The majority of sulfur dioxide produced byindustry comes froma. oil refineries.b. dry cleaners.c. chemical plants.d. coal-burning power plants.

Review

Chapter 12 Review 319

13. Which of the following substances is notinvolved in the chemical reaction that pro-duces smog?a. sunlightb. particulate matterc. automotive exhaustd. ozone

14. Which of the following respiratory diseasesis considered a long-term effect of air pollu-tion on human health?a. emphysemab. bronchitisc. pneumoniad. all of the above

15. Which of the following substances is a color-less, tasteless, and odorless radioactive gas?a. asbestosb. carbon monoxidec. radond. ozone

16. A sound measuring 40 dB has how manytimes the intensity of a sound that measures10 dB?a. 4 timesb. 30 timesc. 400 timesd. 1,000 times

17. Which of the following choices is not aneffective solution to the energy waste relatedto inefficient lighting?a. using low-pressure sodium lighting sourcesb. pointing lights on billboards and street

signs upwardc. placing light sources on time controlsd. shielding light to direct it downward

18. Which of the following numbers on the pHscale would indicate that a substance isacidic?a. 5.0b. 7.0c. 9.0d. none of the above

19. Normal precipitation has a pH ofa. 7.0.b. 5.6.c. 5.1.d. 4.5.

C H A P T E R 12

Predicting Exam Questions Before you take atest, do you ever attempt to predict what the ques-tions will be? For example, of the 10 multiple-choicequestions that appear on this page, how many wouldyou have predicted to be asked in a review of thischapter? Before your next test, predict and answerpossible exam questions.

STUDY TIP


ReviewShort Answer20. Define the term zero-emission vehicle. What

types of vehicles qualify as zero-emissionvehicles?

21. Identify five indoor air pollutants and exam-ples of sources of each pollutant.

22. Explain the health hazards that radon gasposes for humans.

23. Identify a chemical that is used to counteractthe effects of acid precipitation on aquaticecosystems.

24. Explain why acid precipitation is a source ofinternational conflict and why internationalcooperation is necessary to resolve the problem.

Interpreting GraphicsThe map below shows the pH of precipitationthat has been measured at field stations in thenortheastern United States. Use the map and legend to answer questions 25–26.25. Which area(s) of the northeastern United

States have the most-acid precipitation?26. Are the areas that have the highest pH

located close to or far from major cities?

Concept Mapping27. Use the following terms to create a concept

map: air pollution, primary pollutant, volatileorganic compound, scrubber, secondary pol-lutant, smog, and temperature inversion.

Critical Thinking28. Making Decisions Five states now have zero-

emission vehicle programs in place that willhelp decrease some primary pollutants. Whatwould be the advantages or disadvantages ofa federal program that required automobilemakers to produce a set number of ZEVsnationwide?

29. Making Decisions In some cities, noise-pollu-tion laws, such as restrictions placed on theuse of leaf blowers, have been put in place.Do you think the benefits of noise reductionoutweigh the costs of enforcing the law?

30. Inferring Relationships As you read underthe head “International Conflict andCooperation,” about half of the acid precipi-tation that falls in southeastern Canada is pro-duced by pollutants from the United States.How do the acid pollutants get from theirsources to southeastern Canada?

Cross-Disciplinary Connection31. Health Asbestos, lead paint, tobacco, and

many other products have been linked toadverse effects on human health. Researchone such case that has been brought into thecourts. Describe the allegations and the out-come of the trial and write a paragraph thatexplains whether you agree or disagree withthe decision.

Portfolio Project32. Make a Poster Create a poster similar to the

diagram that appears in Figure 9. This dia-gram may be of your home, your garage, aportion of your school, or a particular class-room in your school. Use the diagram toidentify and label potential sources of indoorair pollutants. Photographs may be used todocument these sources.

WRITING SKILLS

READING SKILLS

C H A P T E R 12

320 Chapter 12 Review

?

? ?


Chapter 12 Review 321

Read the passage below, and then answerthe questions that follow.

Lichens are unique organisms that consist of afungus and microscopic alga that live togetherand function as a single organism. The alga isthe photosynthetic partner, whereas the fungusabsorbs water and minerals and anchors theplant. Lichens form crusts or leafy growths onrocks, trees, and bare ground. Lichens do nothave roots. Instead, they absorb the nutrientsthey need directly from rain. Lichens growvery slowly and can live for centuries. Speciesof lichens have adapted to almost every envi-ronment in the world.

Lichens are sensitive to air pollution, par-ticularly sulfur dioxide. When lichens areexposed to high levels of sulfur dioxide, theyabsorb the sulfur that is contained in rain. Thesulfur destroys chlorophyll and inhibits photo-synthesis. So, lichens are good indicators of airpollution. Lichens usually disappear from areaswhere sulfur dioxide levels are high. Where theair is free of pollutants, a greater number oflichens will usually be present. In areas wheresulfur dioxide pollution is decreasing, lichenswill slowly return and colonize the area.

1. Which of the following statements aboutlichens is true?a. Lichens are present when sulfur diox-

ide levels are high.b. Lichens absorb nutrients through their

root systems. c. Lichens photosynthesize.d. Lichens grow only where the climate is

moderate.

2. Where would you be most likely to seethe greatest number of lichens?a. in areas where sulfur dioxide levels are

highb. in areas where sulfur dioxide levels

are lowc. in areas where sulfur dioxide levels are

decreasingd. in areas where sulfur dioxide is absent

MATH SKILLS

Use the graph below to answer questions 33and 34. 33. Analyzing Data The graph below shows the

change in air-pollution emissions in theUnited States between 1970 and 1997.Excluding NOx, which emissions categoryexperienced the greatest decrease over thisperiod of time?

34. Interpreting Graphics Why is lead, Pb, shownseparately from the other air pollutants?

WRITING SKILLS

35. Outlining Topics Outline the major sourcesof air pollution in the United States. Includeinformation about pollution sources andpollution types.

36. Writing Persuasively Write a letter to a leg-islator that expresses your concern about aparticular aspect of air, noise, or light pollu-tion that is important to you.

CO NOX VOC PM-10 SO2 Pb

Air Pollutants

0

50

100

150

200

250

Emis

sio

ns

(in

th

ous

and

s o

f to

ns)

0

30

60

90

120

150

Emis

sio

ns

(in

mill

ion

s o

f to

ns)

1970

1997

Now that you have read the chapter, take amoment to review your answers to the ReadingWarm-Up questions in your EcoLog. If necessary,revise your answers.

READING FOLLOW-UP


322 Chapter 12 Exploration Lab

The Acid TestAcid precipitation is one of the effects of air pollution. Whenpollutants that contain nitrogen or sulfur react with water vaporin clouds, dilute acid forms. These acids fall to Earth as acidprecipitation.

Often, acid precipitation does not occur in the same placewhere the pollutants are released. The acid precipitation usu-ally falls some distance downwind—sometimes hundreds ofkilometers away. Thus, the sites where pollutants that causeacid precipitation are released may not suffer the effects of acidprecipitation.

Coal-burning power plants are one source of air pollution.These power plants release sulfur dioxide into the air. Sulfurdioxide reacts with the water vapor in air to produce acid thatcontains sulfur. This acid later falls to Earth as acid precipitation.

In this investigation, you will create a chemical reaction thatproduces sulfur dioxide. The same acids that result from coal-burning power plants will form. You will see the effects of acidprecipitation on living things—in this case, plants.

Objectives� Perform a chemical reaction that

produces sulfur dioxide, a compo-nent of acid precipitation.

�Hypothesize what the effects ofacids that contain sulfur on plantswill be.

Materialsbeaker, 50 mLclear plastic bags, large (2)houseplants of the same type,

potted (2)sodium nitrite (2 g)sulfuric acid, 1 M (2 mL)twist tie or tape

USING SCIENTIFIC METHODS

Exploration Lab: MODELINGC H A P T E R 12

Procedure1. Place 2 g of sodium nitrite in a

beaker. Place a plant and thebeaker inside a plastic bag. Donot seal the bag.CAUTION: Steps 2–4 should becarried out only under a fumehood or outdoors.

2. Carefully add 2 mL of a 1 Msolution of sulfuric acid to thebeaker. Immediately seal thebag tightly, and secure the bagwith a twist tie or tape. CAU-TION: Because this reactionproduces sulfur dioxide, a toxicgas, the bag should have noleaks. If a leak occurs, moveaway from the bag until thereaction is complete and the gashas dissipated.

3. Seal the same type of plant inan identical bag that does notcontain sodium nitrite or sulfu-ric acid.

� Step 1 Place a plant and a beakerthat contains sodium nitrite into a plastic bag. Do not seal the bag.


4. After 10 minutes, cut both bags open. Stay at least 5 m fromthe bags as the sulfur dioxide gas dissipates. Keep the plantsand bags under the fume hood.

5. Predict the effects of the experiment on each plant over thenext few days. Record your predictions.

6. Observe both plants over the next three days. Record yourobservations below.

Analysis1. Examining Data How closely did your predictions about

the effects of the experiment on each plant match yourobservations?

2. Explaining Events What does this experiment suggest aboutthe effects of acid precipitation on plants?

Conclusions3. Drawing Conclusions In what ways is this a realistic model

of acid precipitation?4. Drawing Conclusions In what ways is this experiment not a

realistic simulation of acid precipitation?

Chapter 12 Exploration Lab 323

Day Control Plant Experimental Plant

1

2

3 DO NOT WRITE IN THIS BOOK

1. Analyzing Models Would you expect to see similar effectsoccur as rapidly, more rapidly, or less rapidly in the environment? Explain your answer.

2. Building Models Acid precipitation is damaging to plantsbecause the sulfur dioxide contained in the water vaporclogs the openings on the surfaces of plants and interfereswith photosynthesis. What kind of a safe model woulddemonstrate the damaging effects of acid precipitation inthe form of water vapor on plant photosynthesis? Wouldthis model be a realistic simulation of acid precipitation?

Extension


324 Chapter 12 Maps in Action

LIGHT SOURCES

M A P S K I L L S

This map of what the Earth looks like from spaceat night shows light sources that are human in ori-gin. The map is a composite image made fromhundreds of images taken by orbiting satellites.Use the map of light sources on Earth to answerthe questions below.

1. Inferring Relationships Using the brightness ofthe light sources on the map as a key, can youestimate the locations of some of the most denselypopulated areas on Earth? Where are some ofthese areas?

2. Inferring Relationships Some climatic condi-tions on Earth, such as extreme cold, heat, wetness,or a thin atmosphere, make parts of our planet less

habitable than others. Examples of areas on ourplanet that do not support large populationsinclude deserts, high mountains, polar regions, andtropical rain forests. From the map, can you identifyregions of the Earth where climatic conditions maynot be able to support large human populations.What are some of these places?

3. Finding Locations Many large cities are seaportsthat are located along the coastlines of the world’soceans. From the map, can you pick out lightsources along coastlines that might indicate the sitesof large ports? Identify some of these cities by name.

4. Inferring Relationships From the differences inthe density of the light sources, can you pick out anyinternational borders?


Chapter 12 Society and the Environment 325

THE DONORA, PENNSYLVANIA, KILLER SMOG

What Do You Think?Who do you think should beheld responsible for theDonora, Pennsylvania, disas-ter? Explain your answer.Given what you know aboutthe regulation of industrial pol-lutants under the Clean AirAct, do you think another inci-dent such as the Donora killersmog could happen in theUnited States today?

For the residents of the smallMonongahela Valley town ofDonora, Pennsylvania, living withthe smoke that billowed from thelocal zinc smelter was an everydayoccurrence—until October 26,1948. On that night, a temperatureinversion and an absence of windbegan to trap a deadly mixture ofsulfur dioxide, carbon monoxide,and metal dust that would hang inthe valley air for five days. Over thatperiod of time, 20 residents losttheir lives and 7,000 other resi-dents—about half of the town’s pop-ulation—suffered some form ofrespiratory problems.

The Weekend of the Killer SmogBy Saturday afternoon, October 29,1948, the yellowish smog hadbecome so thick that spectators inthe stands at a local high-schoolfootball game could not see theplayers on the field. Only the whis-tles of the referees could be heard.By nightfall, driving was unsafe.This proved to be catastrophicbecause doctors recommended thatany residents who suffered from

respiratory ailments be evacuatedfrom town. In an attempt to allevi-ate the suffering of people who werestruggling to breathe, several localfiremen carried oxygen tanksthrough the streets to differenthomes. Because of the low visibility,the firemen had to feel their wayalong buildings and fences. Becausethe supply of oxygen was limited,only a few breaths of oxygen couldbe given to each person. Eleven peo-ple died that night. A makeshiftmorgue was set up in the local com-munity center.

Even as the killer smog chokedthe valley, the zinc smelter continuedproduction throughout the night.The smelter continued sending moregases and dust into the air overDonora. The smelter was shut downonly when the magnitude of theproblem became apparent—6:00A.M. on Sunday, October 30, 1948.

Later that day, a drizzling rainbegan to fall and washed the pollu-tants from the sky. By the time therain fell, 20 people ages 52 to 85,who suffered from respiratory ail-ments, were dead. Thousands of

other people were at home in bed orwere filling the corridors and exam-ining rooms of the two area hospi-tals. People who were less affectedby the smog suffered from nauseaand vomiting, headaches, andabdominal cramps. Some victimswere choking or coughing up blood.The zinc smelter resumed operationon Monday morning, October 31.

The AftermathThe smog of Donora was one of theUnited States’ most serious environ-mental disasters. Shortly after theincident, investigations were under-taken by the PennsylvaniaDepartment of Health, the U.S.Public Health Service, and otheragencies. This was the first time anorganized attempt was made todocument the effects of air pollutionon health in the United States. Theknowledge that air pollution couldbe linked directly to the deaths ofindividuals resulted in legislation atthe local, regional, state, and federallevels. These laws were set to limitemissions of sulfur dioxide, carbonmonoxide, particulate matter, andother pollutants. The greatest legacyof the Donora tragedy was passageof the Clean Air Act of 1970.

� This historical photo from the Pittsburgh Gazette captures the town of Donora,Pennsylvania, as it is enveloped in smog at noon on Saturday, October 28, 1948.


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