ANTROPOGENIC ANTROPOGENIC

AIR AIR

POLLUTIONPOLLUTION

The immediate environment of The immediate environment of man comprises of air on which man comprises of air on which

depends all forms of life. depends all forms of life.

The atmosphere is a complex, The atmosphere is a complex, dynamic natural gaseous dynamic natural gaseous

system, essential to support system, essential to support life on planet Earthlife on planet Earth..

Air is a mechanical mixture of gasesAir is a mechanical mixture of gases..

The normal composition is approximately as The normal composition is approximately as followsfollows: :

- Nitrogen-78%, - Nitrogen-78%, - Oxygen-21%, - Oxygen-21%,

- Carbon dioxide-0.03% - Carbon dioxide-0.03%

andand other gasesother gases – argon, neon, helium – argon, neon, helium, as well , as well as water vapor and suspended matter such as as water vapor and suspended matter such as

dust, bacteria, spores.dust, bacteria, spores.

Apart from Apart from supplying the life-giving oxygensupplying the life-giving oxygen, , air and atmospheric conditions serve several air and atmospheric conditions serve several

functionsfunctions:: The human body isThe human body is cooled by the aircooled by the air contact; contact;

the the sensessenses of hearing and smell function of hearing and smell function through air-transmitted stimuli; through air-transmitted stimuli;

disease agentsdisease agents may be conveyed by air. may be conveyed by air.

Pollution of air by dust, smoke, toxic gases Pollution of air by dust, smoke, toxic gases and chemical vapors could result in sickness and chemical vapors could result in sickness

and death.and death.

The phenomenon called The phenomenon called “pollution”“pollution” is an inescapable is an inescapable consequence of the presence of man and his consequence of the presence of man and his activities. activities.

The term “air pollution”The term “air pollution” signifies the presence in the signifies the presence in the surrounding atmosphere surrounding atmosphere of of chemicalschemicals, , particulate particulate mattermatter, or , or biological materialsbiological materials generated by the generated by the activities of man in activities of man in high enough concentrationshigh enough concentrations that that cause harm or discomfort to humans or other living cause harm or discomfort to humans or other living organisms, or damages the natural environment, organisms, or damages the natural environment, resulting in chemical entering the food chain or resulting in chemical entering the food chain or being present in drinking-water and constituting being present in drinking-water and constituting

additional source of human exposure.additional source of human exposure.

Air pollution is one of the present-day health Air pollution is one of the present-day health problems throughout the world. problems throughout the world.

Abundant amounts of air pollution changes Abundant amounts of air pollution changes natural atmospheric processes, causing natural atmospheric processes, causing acid rainsacid rains, , ozone holeozone hole, and enhancing , and enhancing greenhouse effectgreenhouse effect. . Additionally, it causes Additionally, it causes economic losseseconomic losses. .

The direct effect of air pollutants on plants, The direct effect of air pollutants on plants, animals and soil can influence the structure and function animals and soil can influence the structure and function of ecosystems, including self-regulation ability, thereby of ecosystems, including self-regulation ability, thereby

affecting the quality of life.affecting the quality of life.

An An air pollutantair pollutant is a substance in the air that can is a substance in the air that can

cause harm to humans and the environmentcause harm to humans and the environment..Pollutants Pollutants can be in the formcan be in the form of:of:

- - solid particlessolid particles, , - - liquid dropletsliquid droplets, , - - gasesgases. .

In addition, they may be In addition, they may be naturalnatural or or man-mademan-made..

Examples of Examples of naturalnatural sources sources of air pollution include of air pollution include forest fires, pollen, volcanic emissions, and dust.forest fires, pollen, volcanic emissions, and dust.

Human sourcesHuman sources of air pollutants include of air pollutants include emissions emissions from industry, agriculture, forestry, transportation, from industry, agriculture, forestry, transportation,

power generation, and space heating.power generation, and space heating.

Pollutants are Pollutants are classifiedclassified either as either as primary pollutantsprimary pollutants, or those that , or those that enter the enter the atmosphere directly from various sourcesatmosphere directly from various sources, ,

or as or as

secondarysecondary pollutants pollutants, or those that are , or those that are formed when primary pollutants react with formed when primary pollutants react with each other or with other compounds present each other or with other compounds present

in the atmospherein the atmosphere..

Usually, Usually, primary pollutantsprimary pollutants are substances directly are substances directly emitted from a process, such as ash from a volcanic emitted from a process, such as ash from a volcanic

eruption, the carbon monoxide gas from a motor eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from vehicle exhaust or sulfur dioxide released from

factories.factories.

Secondary pollutantsSecondary pollutants are not emitted directly. Rather, are not emitted directly. Rather, they form in the air when primary pollutants react or they form in the air when primary pollutants react or

interact. interact. An important example An important example of a secondaryof a secondary pollutant ispollutant is ground level ozoneground level ozone - - one of the many one of the many secondary pollutants thatsecondary pollutants that make up make up photochemical photochemical

smog.smog.

Note that some pollutants may be Note that some pollutants may be both primary and both primary and secondarysecondary: that is, they are both emitted directly and : that is, they are both emitted directly and

formed from other primary pollutants.formed from other primary pollutants.

Major primary pollutantsMajor primary pollutants produced by human produced by human

activity includeactivity include::

Nitrogen oxidesNitrogen oxides (NOx) (NOx) - especially - especially nitrogen dioxidenitrogen dioxide are are emitted from high temperature combustion. This reddish-emitted from high temperature combustion. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.one of the most prominent air pollutants.

Sulfur oxidesSulfur oxides (SOx) (SOx) - especially sulfur dioxide. SO - especially sulfur dioxide. SO22 is is produced by volcanoes and in various industrial processes. produced by volcanoes and in various industrial processes. Since Since coal and petroleumcoal and petroleum often contain sulfur compounds, often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of their combustion generates sulfur dioxide. Further oxidation of SOSO22 , usually forms H2SO, usually forms H2SO44, and thus acid rain. This is one of , and thus acid rain. This is one of the causes for concern over the environmental impact of the the causes for concern over the environmental impact of the use of these fuels as power sources. use of these fuels as power sources.

. .

Sulfur and nitrogen oxides from power Sulfur and nitrogen oxides from power

plants, industry, cars and other sources cause plants, industry, cars and other sources cause

rain, snow and fog to become acidicrain, snow and fog to become acidic . .

The most serious damage caused by acid The most serious damage caused by acid

rain today is rain today is acidification of water lakes and acidification of water lakes and

riversrivers. In some cases they become so acidic . In some cases they become so acidic

that they can no longer support fish and their that they can no longer support fish and their

food chains. food chains.

Forest health can also be affected from Forest health can also be affected from

this in areas where the this in areas where the soils are being acidifiedsoils are being acidified..

Major primary pollutantsMajor primary pollutants produced by human activity produced by human activity Carbon monoxideCarbon monoxide - is a colorless, odorless, non-irritating but - is a colorless, odorless, non-irritating but

very poisonous gas. It is a product by incomplete combustion of very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide. major source of carbon monoxide.

Carbon dioxideCarbon dioxide (CO (CO22)) - a - a greenhouse gasgreenhouse gas emitted from emitted from combustion but is also a gas vital to living organisms. It is a combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere.natural gas in the atmosphere.

Volatile organic compounds - VOCsVolatile organic compounds - VOCs are an important outdoor are an important outdoor air pollutant. In this field they are often divided into the separate air pollutant. In this field they are often divided into the separate categories of categories of methanemethane (CH (CH44)) and and non-methanenon-methane (NMVOCs). (NMVOCs).

Methane is an extremely efficient Methane is an extremely efficient greenhouse gasgreenhouse gas which which contributes to enhanced global warming. Within the NMVOCs, contributes to enhanced global warming. Within the NMVOCs, the aromatic compounds the aromatic compounds benzene, toluene and xylenebenzene, toluene and xylene are are suspected carcinogens and may lead to leukemia through suspected carcinogens and may lead to leukemia through prolonged exposure.prolonged exposure.

Major primary pollutantsMajor primary pollutants produced by human produced by human activityactivity

Particulate matter (PM)Particulate matter (PM) - particulates, or fine - particulates, or fine particles, are tiny particles of solid or liquid particles, are tiny particles of solid or liquid suspended in a gas. Sources of particulate matter suspended in a gas. Sources of particulate matter can be man made or natural. can be man made or natural.

Some particulates occur Some particulates occur naturallynaturally, originating , originating from volcanoes, dust storms, forest and from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. grassland fires, living vegetation, and sea spray.

Human activitiesHuman activities, such as the burning of fuels , such as the burning of fuels in vehicles, power plants and various industrial in vehicles, power plants and various industrial processes also generate significant amounts of processes also generate significant amounts of aerosols. aerosols.

Averaged over the globe, anthropogenic Averaged over the globe, anthropogenic aerosols currently account for about 10 percent aerosols currently account for about 10 percent

of the total amount of aerosols in our of the total amount of aerosols in our atmosphere. atmosphere.

Increased levels of fine particles in the air are Increased levels of fine particles in the air are linked to linked to health hazardshealth hazards such as heart disease, such as heart disease,

altered lung function and lung cancer. altered lung function and lung cancer.

Major primary pollutantsMajor primary pollutants produced by produced by human activityhuman activity

Toxic Toxic metalsmetals, such as , such as leadlead, , cadmiumcadmium and and coppercopper. .

Chlorofluorocarbons Chlorofluorocarbons (CFCs)(CFCs) - harmful to the ozone - harmful to the ozone

layer emitted from products currently banned from use. layer emitted from products currently banned from use.

AmmoniaAmmonia (NH3) (NH3) - emitted from agricultural - emitted from agricultural

processes. Ammonia contributes significantly to the processes. Ammonia contributes significantly to the

nutritional needs of terrestrial organisms by serving as a nutritional needs of terrestrial organisms by serving as a

precursor to foodstuffs and fertilizers. Although in wide precursor to foodstuffs and fertilizers. Although in wide

use, ammonia is both caustic and hazardous. use, ammonia is both caustic and hazardous.

Major primary pollutantsMajor primary pollutants

OdorsOdors - such as from garbage, sewage, and - such as from garbage, sewage, and industrial processes industrial processes

Radioactive pollutantsRadioactive pollutants - produced by nuclear - produced by nuclear explosions, war explosives, and explosions, war explosives, and natural natural processesprocesses such as the radioactive decay of such as the radioactive decay of radonradon..

Secondary pollutants includeSecondary pollutants include::

Particulate matterParticulate matter formed from formed from gaseous primary pollutants and gaseous primary pollutants and compounds in photochemical smog. compounds in photochemical smog.

Smog Smog is a kind ofis a kind of air pollution; air pollution; the the wordword "smog" "smog" is a portmanteauis a portmanteau of smoke of smoke and fogand fog. .

IIndustrialndustrial or or graygray smog is considered smog is considered the most serious type of air pollutionthe most serious type of air pollution. .

ClassicClassic smogsmog results from results from ssmoke and moke and oxidesoxides of that are released by of that are released by burning coal burning coal and oil containing minor amounts of sulfurand oil containing minor amounts of sulfur. .

The smoke gives the air a The smoke gives the air a gray colorgray color. . Industrial smog has been known to cause Industrial smog has been known to cause air pollution disasters. One of the worst air pollution disasters. One of the worst occurred in London in December of occurred in London in December of 1952. Five days of stagnant air brought 1952. Five days of stagnant air brought about high-pressure systems caused about high-pressure systems caused between 3,500 and 4,000 deaths.between 3,500 and 4,000 deaths.

ModernModern smog smog does does notnot usually usually come from coal but fromcome from coal but from vehicularvehicular

andand industrial emissionsindustrial emissions that are that are actedacted on in the atmosphere on in the atmosphere by sunlight to by sunlight to form secondary pollutantsform secondary pollutants that also that also

combine with the primary emissions combine with the primary emissions to form to form photochemical smogphotochemical smog (also (also

know as know as brownbrown smog) smog)..

OzoneOzone in the in the upper level in the in the upper level occurs occurs naturally and protects lifenaturally and protects life on earth but on earth but ozone at ozone at ground levelground level is a noxious is a noxious pollutantpollutant..

Ozone (OOzone (O33) is a ) is a key key constituent of the constituent of the tropospheretroposphere (it is also an important (it is also an important constituent of certain regions of the constituent of certain regions of the stratospherestratosphere commonly known as the commonly known as the Ozone layerOzone layer).).

Secondary pollutants includeSecondary pollutants include::

Ground level ozoneGround level ozone (O (O33)) is is secondarysecondary pollutant pollutant formed in the atmosphere through a complex set of formed in the atmosphere through a complex set of chemical reactions involving hydrocarbons, oxides of chemical reactions involving hydrocarbons, oxides of nitrogen, and sunlight.nitrogen, and sunlight. It is the major component of It is the major component of photochemical smogphotochemical smog and presents the most and presents the most intractable urban air quality problem. intractable urban air quality problem.

Photochemical and chemical reactions Photochemical and chemical reactions involving it drive many of the chemical processes that involving it drive many of the chemical processes that occur in the atmosphere by day and by night. occur in the atmosphere by day and by night. The The rate at which the reactions proceed is related to rate at which the reactions proceed is related to both temperature and intensity of the sunlight.both temperature and intensity of the sunlight.

Peroxyacetyl nitratePeroxyacetyl nitrate (PAN) (PAN) - formed from NOx and - formed from NOx and VOCs. VOCs.

Sources of air pollutionSources of air pollution

Sources of air pollution refer to the variousSources of air pollution refer to the various

locations, activities or factors which are locations, activities or factors which are

responsible for the releasing of pollutants in responsible for the releasing of pollutants in

the atmosphere. the atmosphere.

These sources can be classified into These sources can be classified into

two major categoriestwo major categories which are: which are:

Natural sourcesNatural sources Dust Dust from natural sources, usually large from natural sources, usually large

areas of land with little or no vegetation. areas of land with little or no vegetation. MethaneMethane,, emitted by the digestion of emitted by the digestion of

food by animals, for example cattle. food by animals, for example cattle. SmokeSmoke and and carbon monoxidecarbon monoxide from from

wildfires. wildfires. Volcanic activity, which produce Volcanic activity, which produce sulfursulfur, ,

chlorinechlorine, , andand ash particulatesash particulates..

Natural sourcesNatural sources - - Radon gasRadon gas from radioactive decay within the from radioactive decay within the

Earth's crust. Earth's crust. Radon is a colorless, odorless, naturally Radon is a colorless, odorless, naturally

occurring, radioactive noble gas that occurring, radioactive noble gas that is is formed formed from the decay of radiumfrom the decay of radium. It is considered to . It is considered to be a health hazard. Radon gas from natural be a health hazard. Radon gas from natural sources can accumulate in buildings, sources can accumulate in buildings, especially in confined areas such as the especially in confined areas such as the basement and it is the second basement and it is the second most frequent most frequent cause of lung cancercause of lung cancer, after cigarette smoking., after cigarette smoking.

Anthropogenic sourcesAnthropogenic sources (human (human activity) mostly related to burning activity) mostly related to burning different kinds of different kinds of fuelfuel::

"Stationary Sources""Stationary Sources" include include smoke stacks of power plants, smoke stacks of power plants, factories and waste incinerators, as factories and waste incinerators, as well as furnaces and other types of well as furnaces and other types of fuel-burning heating devices.fuel-burning heating devices.

Combustion of fuel to generate heat and Combustion of fuel to generate heat and power produces power produces sulfur dioxidesulfur dioxide, , nitrogen oxidesnitrogen oxides, , hydrocarbonshydrocarbons, , polynuclear aromatic polynuclear aromatic hydrocarbonshydrocarbons, , dustdust, , fly ashfly ash and smoke and the and smoke and the carcinogenic carcinogenic 3,4-benzepyrenes3,4-benzepyrenes. .

Domestic combustionDomestic combustion of coal, wood or oil of coal, wood or oil is also a major source of these pollutants. is also a major source of these pollutants.

Many Many industriesindustries discharge discharge carbon carbon monoxidemonoxide, , carbon dioxidecarbon dioxide, , hydrogen sulfidehydrogen sulfide, , sulfur dioxidesulfur dioxide, , hydrogen fluoridehydrogen fluoride, , hydrochloric hydrochloric

acidacid, , dustdust, , ozoneozone..

Anthropogenic sourcesAnthropogenic sources "Mobile Sources""Mobile Sources" include motor vehicles, include motor vehicles,

marine vessels, aircraft etc. marine vessels, aircraft etc.

AutomobilesAutomobiles are the major source of air are the major source of air pollution in urban areas. They emit hydro-pollution in urban areas. They emit hydro-carbons, carbon monoxide, lead, nitrogen carbons, carbon monoxide, lead, nitrogen oxides and particulate matter. oxides and particulate matter. In strong In strong sunlight and UV-radiation certain of these sunlight and UV-radiation certain of these hydrocarbons and oxides of nitrogen hydrocarbons and oxides of nitrogen may be may be converted in the atmosphere into converted in the atmosphere into “photochemical” pollutants of oxidizing “photochemical” pollutants of oxidizing nature. nature.

-ChemicalsChemicals, , dustdust and and controlled burn controlled burn practicespractices in agriculture and forestry in agriculture and forestry management. Controlled or prescribed management. Controlled or prescribed burning is a techniqueburning is a technique sometimes used in sometimes used in forest management, farming, prairie forest management, farming, prairie restoration. Controlled burning stimulates the restoration. Controlled burning stimulates the germination of some desirable forest trees, germination of some desirable forest trees, thus renewing the forest. thus renewing the forest.

- Fumes from paint, hair spray, varnish, - Fumes from paint, hair spray, varnish, aerosol sprays and other aerosol sprays and other solvents solvents

-- MilitaryMilitary - such as nuclear weapons, toxic - such as nuclear weapons, toxic gases.gases.

• Waste depositionWaste deposition in landfills, which in landfills, which generate methane. generate methane.

MethaneMethane is not toxic; however, it is is not toxic; however, it is highly flammable and may form highly flammable and may form explosive mixtures with air. Methane is explosive mixtures with air. Methane is also an asphyxiant and may displace also an asphyxiant and may displace oxygen in an enclosed space. Asphyxia or oxygen in an enclosed space. Asphyxia or suffocation may result if the oxygen suffocation may result if the oxygen concentration is reduced to below 19.5% concentration is reduced to below 19.5% by displacement.by displacement.

Meteorological factorsMeteorological factors

The level of atmospheric pollution The level of atmospheric pollution at any time depends upon meteorological at any time depends upon meteorological factors, e.g. topography, air movement factors, e.g. topography, air movement and climate. Winds help in the dispersal and climate. Winds help in the dispersal and dilution of pollutants. and dilution of pollutants.

If the If the topographytopography is dominated by is dominated by mountains (or tall buildings) the winds mountains (or tall buildings) the winds become weak and calm, and pollutants become weak and calm, and pollutants tend totend to concentrate in the breathing zoneconcentrate in the breathing zone..

The vertical diffusion of pollutants depends The vertical diffusion of pollutants depends upon the temperature gradientupon the temperature gradient.. When there is a When there is a rapid cooling of lower layers of air rapid cooling of lower layers of air (temperature (temperature inversion)inversion) there is a little vertical motion and the there is a little vertical motion and the pollutants and water vapours remain trapped pollutants and water vapours remain trapped at at the lower levels and the result is the lower levels and the result is “smog“smog”” – this – this way the temperature inversion is a threat to way the temperature inversion is a threat to human health.human health.

All the mentioned factors must be carefully All the mentioned factors must be carefully studied studied prior to locationprior to location of industrial factories of industrial factories near towns and villages and a certain distance near towns and villages and a certain distance should be kept to avoid health problems of the should be kept to avoid health problems of the

residentsresidents..

Effects of air pollutantsEffects of air pollutants

Many urban residents are exposed to air Many urban residents are exposed to air pollution level above the recommended limits. pollution level above the recommended limits. In many developing countries air quality has In many developing countries air quality has deteriorated because of raising industrial deteriorated because of raising industrial activity, increasing power generation and the activity, increasing power generation and the combustion of streets with poorly maintained combustion of streets with poorly maintained automobiles that use leaded fuel. automobiles that use leaded fuel.

Air pollution can affect by two main waysAir pollution can affect by two main ways::

1.1. Health aspects Health aspects.. The health effects The health effects are both are both immediate and delayedimmediate and delayed. .

The The immediateimmediate effects are borne by effects are borne by the respiratory system, the resulting the respiratory system, the resulting state is acute bronchitis. If the air state is acute bronchitis. If the air pollution is intense, it may result even pollution is intense, it may result even immediate death by suffocation. immediate death by suffocation.

The The delayeddelayed effects most commonly effects most commonly are chronic bronchitis, lung cancer, are chronic bronchitis, lung cancer, bronchial asthma and respiratory bronchial asthma and respiratory allergiesallergies. .

Precise Precise estimates of the riskestimates of the risk of air of air pollution to health are difficult to pollution to health are difficult to quantify because of problems in quantify because of problems in estimating the estimating the degree of exposuredegree of exposure of of individuals and the influence of possible individuals and the influence of possible compounding variables such as compounding variables such as nutrition, nutrition, smoking, occupation and climatesmoking, occupation and climate. .

The elderly, children, smokers and The elderly, children, smokers and those with chronic respiratory difficulties those with chronic respiratory difficulties are most vulnerableare most vulnerable..

Major air pollutants, their sources and adverse Major air pollutants, their sources and adverse

effectseffects Noxious agentNoxious agent SourcesSources Adverse effectsAdverse effects

Oxides of nitrogenOxides of nitrogen Automobile exhaust, Automobile exhaust, combustion of fuel to generate combustion of fuel to generate heat and power, gas and wood heat and power, gas and wood stoves, many industriesstoves, many industries

Respiratory tract irritation, Respiratory tract irritation, bronchial hyperactivity, bronchial hyperactivity, impaired lung defences, impaired lung defences, bronchialitis obliteransbronchialitis obliterans

HydrocarbonsHydrocarbons Automobile exhaust, Automobile exhaust, combustion of fuel to generate combustion of fuel to generate heat and power, cigarette heat and power, cigarette smokesmoke

Lung cancerLung cancer

OzoneOzone Automobile exhaust, high Automobile exhaust, high attitude aircraft cabinsattitude aircraft cabins

Cough, substernal discomfort, Cough, substernal discomfort, bronchoconstriction, respiratory bronchoconstriction, respiratory tract irritation tract irritation

Sulfur dioxideSulfur dioxide Combustion of fuel to generate Combustion of fuel to generate heat and power, smelters, oil heat and power, smelters, oil refineriesrefineries

Exacerbation of asthma, Exacerbation of asthma, respiratory tract irritationrespiratory tract irritation

LeadLead Automobile exhaust using Automobile exhaust using leaded gasoline leaded gasoline

Impaired neuropsychological Impaired neuropsychological development in childrendevelopment in children

Effects of air pollutantsEffects of air pollutants2. 2. Social and economic aspects.Social and economic aspects.

Air pollution generates various economic losses Air pollution generates various economic losses but their detailed estimation is extremely difficult. but their detailed estimation is extremely difficult. They may be divided into four groups: They may be divided into four groups:

expenses for air expenses for air quality protectionquality protection; ; expenses generated by the expenses generated by the worse health condition of worse health condition of

the societythe society; ; losses of losses of raw materialsraw materials which become air pollution; which become air pollution; losses caused by the losses caused by the increased corrosionincreased corrosion of machines, of machines,

buildings, buildings, and damage of historical buildings and and damage of historical buildings and monuments. monuments.

Effects of air pollutantsEffects of air pollutantsAnthropogenic global warmingAnthropogenic global warming (AGW), (AGW),

a recent warming of the Earth's lower a recent warming of the Earth's lower

atmosphere as evidenced by the global mean atmosphere as evidenced by the global mean

temperature anomaly trend, is believed to be the temperature anomaly trend, is believed to be the

result of an result of an "enhanced greenhouse effect""enhanced greenhouse effect"

mainly due to human-produced increased mainly due to human-produced increased

concentrations of concentrations of greenhouse gasesgreenhouse gases in the in the

atmosphere and changes in the use of land.atmosphere and changes in the use of land.

The The greenhouse effectgreenhouse effect

refers to the refers to the change in the change in the

steady state temperaturesteady state temperature of of

a planet or moon by the a planet or moon by the

presence of an presence of an atmosphere atmosphere

containing gascontaining gas that that absorbsabsorbs

and and emitsemits infrared infrared

radiationradiation..

Greenhouse gasesGreenhouse gases include include water vaporwater vapor, , carbon dioxidecarbon dioxide andand methanmethane.e.

The greenhouse effectThe greenhouse effect, is , is generally generally believed to believed to come from the build up of carbon come from the build up of carbon dioxide (COdioxide (CO22) gas in the atmosphere) gas in the atmosphere. .

Plants convert carbon dioxide back to Plants convert carbon dioxide back to oxygen, but the release of carbon dioxide from oxygen, but the release of carbon dioxide from human activities is higher than the world's human activities is higher than the world's plants can process. The situation is made plants can process. The situation is made worse since many of the earth's forests are worse since many of the earth's forests are being removed, and plant life is being being removed, and plant life is being

damaged by acid rain.damaged by acid rain.

Basic mechanismBasic mechanism The Earth receives energy from the Sun The Earth receives energy from the Sun

mostly in the form of mostly in the form of visible lightvisible light. The bulk of . The bulk of

this energy is this energy is not absorbednot absorbed by the atmosphere by the atmosphere

since the atmosphere issince the atmosphere is transparenttransparent to visible to visible

light. light.

50% of the sun's energy reaches the 50% of the sun's energy reaches the Earth which is absorbed by the surface as Earth which is absorbed by the surface as heatheat.. Because of its temperature, the Earth's Because of its temperature, the Earth's surface surface radiates energy in infrared rangeradiates energy in infrared range. .

Basic mechanismBasic mechanismThe Greenhouse gases are The Greenhouse gases are not transparentnot transparent

to infrared radiation so they absorb infrared to infrared radiation so they absorb infrared radiation. radiation.

They warm the atmosphere by efficiently They warm the atmosphere by efficiently absorbingabsorbing thermal infrared radiationthermal infrared radiation emitted by emitted by the the Earth’s surfaceEarth’s surface, by the , by the atmosphereatmosphere itself itself, , and by and by cloudsclouds..

As a result of its warmth, the atmosphere As a result of its warmth, the atmosphere also radiates thermal infrared in all directions, also radiates thermal infrared in all directions, including downward to the Earth’s surface. including downward to the Earth’s surface.

Basic mechanismBasic mechanism

Thus, Thus, greenhouse gasesgreenhouse gases trap heattrap heat within the surface-troposphere systemwithin the surface-troposphere system. .

Infrared radiation is absorbed from all Infrared radiation is absorbed from all directions and is passed as heat to all gases directions and is passed as heat to all gases in the atmosphere. The atmosphere also in the atmosphere. The atmosphere also radiates in the infrared range (because of its radiates in the infrared range (because of its temperature, in the same way the Earth's temperature, in the same way the Earth's surface does) and does so in all directions. surface does) and does so in all directions.

The surface and lower atmosphere are The surface and lower atmosphere are warmed because of the greenhouse gases and warmed because of the greenhouse gases and makes our life on earth possiblemakes our life on earth possible. .

In the absence of the greenhouseIn the absence of the greenhouse effect effect and an atmosphere, the Earth's average and an atmosphere, the Earth's average surface temperature of 14 °C (57 °F) could be surface temperature of 14 °C (57 °F) could be as low as −18 °C (−0.4 °F). In our solar as low as −18 °C (−0.4 °F). In our solar system, Mars, Venus, and the moon Titan also system, Mars, Venus, and the moon Titan also exhibit greenhouse effects according to their exhibit greenhouse effects according to their respective environments. In addition, Titan respective environments. In addition, Titan has an anti-greenhouse effect and Pluto has an anti-greenhouse effect and Pluto exhibits behavior similar to the anti-exhibits behavior similar to the anti-

greenhouse effectgreenhouse effect..

This This mechanismmechanism is fundamentally is fundamentally

different different from the mechanism of an from the mechanism of an

actual greenhouse, which instead isolates actual greenhouse, which instead isolates

air inside the structure so that the heat is air inside the structure so that the heat is

not lost by convection and conductionnot lost by convection and conduction. .

Effects of air pollutantsEffects of air pollutantsStratospheric ozone depletionStratospheric ozone depletion due to due to

air pollution has been recognized as a air pollution has been recognized as a threat to human health as well as to the threat to human health as well as to the Earth's ecosystems. Earth's ecosystems.

The ozone layerThe ozone layer in in the stratospherethe stratosphere protects the earth from harmful ultraviolet protects the earth from harmful ultraviolet radiation from the sun. radiation from the sun.

Ozone depletionOzone depletion describes two describes two distinct, but related observations: distinct, but related observations: - - a slow, steady a slow, steady declinedecline of about 4 percent of about 4 percent per decade in the total volume of ozone in per decade in the total volume of ozone in Earth's stratosphereEarth's stratosphere (ozone layer) since the (ozone layer) since the late 1970s, and late 1970s, and - - a a much largermuch larger, , but seasonalbut seasonal, decrease in , decrease in stratospheric ozone stratospheric ozone over Earth's polar over Earth's polar regionsregions during the same period. during the same period.

The latter phenomenon is commonly The latter phenomenon is commonly referred to as the referred to as the ozone holeozone hole. In addition to . In addition to this well-known stratospheric ozone depletion, this well-known stratospheric ozone depletion, there are also there are also tropospheric tropospheric ozone depletion ozone depletion eventsevents, which occur near the surface in polar , which occur near the surface in polar regions during spring.regions during spring.

The detailed mechanism by which the The detailed mechanism by which the polar ozone holes form is different from that polar ozone holes form is different from that for the mid-latitude thinning, but the for the mid-latitude thinning, but the most most important process in both trends is important process in both trends is catalytic catalytic destruction of ozonedestruction of ozone by atomic by atomic chlorinechlorine and and

brominebromine..

The The main sourcemain source of these halogen atoms in the of these halogen atoms in the stratosphere stratosphere is photodissociation of is photodissociation of chlorofluorocarbon chlorofluorocarbon (CFC) compounds(CFC) compounds, , commonly called commonly called freonsfreons,, and of and of bromo-bromo-fluorocarbonfluorocarbon compounds compounds known as known as halonshalons..

These compounds are transported into These compounds are transported into the stratosphere after being emitted at the the stratosphere after being emitted at the surface. They are rsurface. They are releaseeleasedd from aerosol from aerosol sprays, polystyrene containers, refrigerator sprays, polystyrene containers, refrigerator coolant and air conditioning unitscoolant and air conditioning units. . Both ozone Both ozone depletion mechanisms strengthened as depletion mechanisms strengthened as emissions of CFCs and halons increased.emissions of CFCs and halons increased.

CFCs and other contributory substances CFCs and other contributory substances are commonly referred to as are commonly referred to as ozone-depleting ozone-depleting substancessubstances ( (ODSODS). ).

Since the ozone layer prevents most Since the ozone layer prevents most harmful UVB wavelengths (270–315 nm) of harmful UVB wavelengths (270–315 nm) of ultraviolet light from passing through the ultraviolet light from passing through the Earth's atmosphere, observed and projected Earth's atmosphere, observed and projected decreases in ozone have generated worldwide decreases in ozone have generated worldwide concern leading to concern leading to adoption of the Montreal adoption of the Montreal Protocol banning the production of CFCs and Protocol banning the production of CFCs and

halons as well as related ozone depletinghalons as well as related ozone depleting chemicalschemicals such as such as carbon tetrachloridecarbon tetrachloride and and

trichloroethanetrichloroethane..

It is suspected that a variety of It is suspected that a variety of biological consequences such as increases biological consequences such as increases in skin cancer, damage to plants, and in skin cancer, damage to plants, and reduction of plankton populations in the reduction of plankton populations in the ocean's photic zone may result from the ocean's photic zone may result from the increased UV exposure due to ozone increased UV exposure due to ozone depletion.depletion.

Consequences of ozone layer Consequences of ozone layer depletiondepletion

Increased UVIncreased UVAlthough decreases in stratospheric ozone are Although decreases in stratospheric ozone are

well-tied to CFCs and there are good theoretical well-tied to CFCs and there are good theoretical reasons to believe that decreases in ozone will lead reasons to believe that decreases in ozone will lead to to increases in surface UVBincreases in surface UVB, there is no direct , there is no direct observational evidence linking ozone depletion to observational evidence linking ozone depletion to higher incidence of skin cancer in human beings. higher incidence of skin cancer in human beings.

This is partly due to the fact that This is partly due to the fact that UVAUVA, which , which has also been implicated in some forms of skin has also been implicated in some forms of skin cancer, is not absorbed by ozone, and it is nearly cancer, is not absorbed by ozone, and it is nearly impossible to control statistics for lifestyle changes impossible to control statistics for lifestyle changes in the populacein the populace..

Because it is this same UV radiation that Because it is this same UV radiation that creates ozone in the ozone layer from Ocreates ozone in the ozone layer from O22 (regular(regular oxygen) in the first place, oxygen) in the first place, a reduction a reduction in stratospheric ozone would actually tend to in stratospheric ozone would actually tend to increaseincrease photochemical production of photochemical production of ozone at ozone at lower levels (in the tropospherelower levels (in the troposphere)),, although the although the overall observed trends in total column ozoneoverall observed trends in total column ozone still still show a decreaseshow a decrease, largely , largely because ozone because ozone produced lower down has a naturally shorter produced lower down has a naturally shorter photochemical lifetimephotochemical lifetime, so it is , so it is destroyed before destroyed before the concentrations could reach a level which the concentrations could reach a level which would compensate for the ozone reduction would compensate for the ozone reduction higher up.higher up.

Effects of ozone layer depletion on Effects of ozone layer depletion on humanshumans

UVBUVB (the higher energy UV radiation absorbed by (the higher energy UV radiation absorbed by ozone) is generally accepted to be a contributory factor to ozone) is generally accepted to be a contributory factor to skin cancerskin cancer.. In addition, increased surface UV leads to In addition, increased surface UV leads to increased tropospheric ozoneincreased tropospheric ozone, which is a health risk to , which is a health risk to humans. The increased surface UV also represents humans. The increased surface UV also represents an an increase in theincrease in the vitamin D synthetic capacityvitamin D synthetic capacity of the of the sunlight. sunlight.

The cancer preventive effects of vitamin D represent The cancer preventive effects of vitamin D represent a possible beneficial effect of ozone depletion. In terms of a possible beneficial effect of ozone depletion. In terms of health costs, the possible benefits of increased UV health costs, the possible benefits of increased UV irradiance may outweigh the burdenirradiance may outweigh the burden. .

Effects of ozone layer depletion on Effects of ozone layer depletion on humanshumans

1. 1. Basal and Squamous Cell CarcinomasBasal and Squamous Cell Carcinomas The most common forms of skin cancer in humans, The most common forms of skin cancer in humans, have been strongly linked to UVB exposure. The have been strongly linked to UVB exposure. The mechanism by which UVB induces these cancers is mechanism by which UVB induces these cancers is well understood — absorption of UVB radiation well understood — absorption of UVB radiation causes the pyrimidine bases in the DNA molecule causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors to form dimers, resulting in transcription errors when the DNA replicates. By combining when the DNA replicates. By combining epidemiological data with results of animal studies, epidemiological data with results of animal studies, scientists have estimated that a one percent scientists have estimated that a one percent decrease in stratospheric ozone would increase the decrease in stratospheric ozone would increase the incidence of these cancers by 2%.incidence of these cancers by 2%.

2. 2. Malignant MelanomaMalignant Melanoma - Another form of - Another form of

skin cancer, is much lessskin cancer, is much less common but far common but far more dangerous, being lethal in about 15% - more dangerous, being lethal in about 15% - 20% of the cases diagnosed. The relationship 20% of the cases diagnosed. The relationship between malignant melanoma and ultraviolet between malignant melanoma and ultraviolet

exposure is not yet well understood, but itexposure is not yet well understood, but it appears that both UVB and UVA are involved. appears that both UVB and UVA are involved. Experiments on fish suggest that 90 to 95% of Experiments on fish suggest that 90 to 95% of

malignant melanomas may be duemalignant melanomas may be due to UVA to UVA and visible radiation whereas experiments on and visible radiation whereas experiments on opossums suggest a larger role for UVB. opossums suggest a larger role for UVB.

Because of this uncertainty, it is difficult Because of this uncertainty, it is difficult to estimate the impact of ozone depletion on to estimate the impact of ozone depletion on melanoma incidence. One study showed that a melanoma incidence. One study showed that a 10% increase in UVB radiation was 10% increase in UVB radiation was associated with a 19% increase in melanomas associated with a 19% increase in melanomas for men and 16% for women. A study of for men and 16% for women. A study of people in Puntapeople in Punta Arenas, at the southern tip of Arenas, at the southern tip of Chile, showed a 56% increase in melanoma Chile, showed a 56% increase in melanoma and a 46% increase in nonmelanoma skin and a 46% increase in nonmelanoma skin cancer over a period of seven years, along cancer over a period of seven years, along with decreased ozone and increased UVB with decreased ozone and increased UVB levels.levels.

3. 3. Cortical CataractsCortical Cataracts - Studies are - Studies are suggestive of an association between ocular suggestive of an association between ocular cortical cataracts and UV-B exposure.cortical cataracts and UV-B exposure.

4. 4. Increased Tropospheric OzoneIncreased Tropospheric Ozone - - Increased surface UV leads to increased Increased surface UV leads to increased tropospheric ozone. tropospheric ozone. Ground-levelGround-level ozone ozone is is generally recognized to be a generally recognized to be a health riskhealth risk, due , due to its strong to its strong oxidant oxidant propertiesproperties. . At this time, At this time, ozone at ground level is produced mainly by the ozone at ground level is produced mainly by the action of UV radiation on combustion gases action of UV radiation on combustion gases from vehicle exhausts.from vehicle exhausts.

Prevention activitiesPrevention activities

The problem of air pollution is The problem of air pollution is worldwide and transcends national worldwide and transcends national boundaries. boundaries.

Though air pollution is still a serious Though air pollution is still a serious problem, in many countries in the world, problem, in many countries in the world, steps are being taken to stop the steps are being taken to stop the damage to our environment from air damage to our environment from air pollutionpollution. .

Many electric power plants, factories, Many electric power plants, factories, and facilities that burn wastes are and facilities that burn wastes are equipped with equipped with devices called devices called scrubbersscrubbers.. Scrubbers Scrubbers remove sulfur dioxideremove sulfur dioxide and other and other pollutants before the wastes are released pollutants before the wastes are released into the air. into the air.

Also, today's cars are designed to Also, today's cars are designed to create less pollution. Many are equipped create less pollution. Many are equipped with anti-pollution devices called with anti-pollution devices called catalytic catalytic convertersconverters, which reduce the amount of , which reduce the amount of

pollution from automobile engines.pollution from automobile engines.

Most polluted citiesMost polluted citiesAir pollution is usually concentrated Air pollution is usually concentrated

in densely populated metropolitan areas, in densely populated metropolitan areas, especially in developing countries where especially in developing countries where environmental regulations are relatively lax environmental regulations are relatively lax or nonexistent. or nonexistent.

However, even populated areas in However, even populated areas in developed countries attain unhealthy levels developed countries attain unhealthy levels of pollution.of pollution.

Most Polluted World Cities by PM

Particulate matter,μg/m³ (2004)

City

169 Cairo, Egypt

150 Delhi, India

128 Kolkata, India (Calcutta)

125 Tianjin, China

123 Chongqing, China

109 Kanpur, India

109 Lucknow, India

104 Jakarta, Indonesia

101 Shenyang, China

Carbon dioxide emissionsTotal CO2 emissions

106 Tons of CO2 per year:

• United States: 2, 795 • China: 2,680 • Russia: 661 • India: 583 • Japan: 415 • Germany: 356 • Australia: 300 • South Africa: 232 • United Kingdom: 212 • South Korea: 185

Per capita CO2 emissions Tons of CO2 per year per capita:

• Australia: 10

• United States: 8.2

• United Kingdom: 3.2

• China: 1.8

• India: 0.5