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Air Pollution

General

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Definition

Air pollution may be defined as the presencein the air (outdoor atmosphere) ofone ormore contaminants orcombinations

thereofin such quantities and of suchdurations as may be or tend to bein jur ious to human, animal or plant l ife,

or p roperty , or which un reasonably

interferes w ith the com fortableenjoyment o f l ife or p roperty or

conduc t of bus iness.

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Air PollutantIt is a substance or effect dwelling temporarily or

permanently in the air , which adversely alters theenvironment by interfering with the health, the comfort,or the food chain, or by interfering with the propertyvalues of people.

A pollutant can be solid (large or sub-molecular), liquid

or gas .It may originate from a natural or anthropogenic source

(or both).

It is estimated that anthropogenic sources have changedthe composition of global air by less than 0.01%.

However, it is widely accepted that even a small changecan have a significant adverse effect on the climate,ecosystem and species on the planet.

Examples of these are acid rain, ozone in the lower

atmosphere, and photochemical smog.

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Composition of

dry atmosphere, by volume

ppmv: parts per million by volume

Gas Volume

Nitrogen (N2) 780,840 ppmv (78.084%)

Oxygen (O2) 209,460 ppmv (20.946%)

Argon (Ar) 9,340 ppmv (0.9340%)

Carbon dioxide

(CO2)375 ppmv

Neon (Ne) 18.18 ppmv

Helium (He) 5.24 ppmv

Methane (CH4) 1.745 ppmv

Krypton (Kr) 1.14 ppmv

Hydrogen (H2) 0.55 ppmv

Not included in above dry atmosphere:

Water vapor

(highly variable)typically 1%

Mean Atmospheric Water Vapor.

Source for figures above:NASA. Carbon dioxide and methane updated (to 1998) by IPCCTAR table 6.1 [1]. The NASA total was 17 ppmv

over 100%, and CO2 was increased here by 15 ppmv. To normalize, N2 should be reduced by about 25 ppmv and O2 by about 7 ppmv.

Minor components of air not listed above include:

Gas Volume

nitrous

oxide0.5 ppmv

xenon 0.09 ppmv

ozone 0.0 to 0.07 ppmv

nitrogendioxide

0.02 ppmv

iodine 0.01 ppmv

carbon

monoxidetrace

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N ti l A bi t Ai Q lit St d d

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National Ambient Air Quality Standards

Pollutant Primary Stds. Averaging Times SecondaryStds.

9 ppm (10mg/m

3)

8-hour1

NoneCarbon Monoxide

35 ppm(40 mg/m

3)

1-hour1

None

Lead 1.5 g/m3

Quarterly Average Same as

PrimaryNitrogen Dioxide 0.053 ppm

(100 g/m3)

Annual (ArithmeticMean)

Same asPrimary

50 g/m3

Annual2

(Arith.Mean)

Same asPrimary

Particulate Matter(PM10)

150 ug/m3

24-hour1

15.0 g/m3

Annual3

(Arith.Mean)

Same asPrimary

Particulate Matter(PM2.5)

65 ug/m3

24-hour4

Ozone 0.08 ppm 8-hour5

Same as

Primary

0.03 ppm Annual (Arith. Mean) -------

0.14 ppm 24-hour1

-------

Sulfur Oxides

------- 3-hour1

0.5 ppm(1300 ug/m

3)

1Not to be exceeded more than once per year.

2

To attain this standard, the 3-year average of the weighted annual mean PM10 concentration ateach monitor within an area must not exceed 50 ug/m3.

3To attain this standard, the 3-year average of the weighted annual mean PM2.5 concentrations

from single or multiple community-oriented monitors must not exceed 15.0 ug/m3.

4To attain this standard, the 3-year average of the 98th percentile of 24-hour concentrations at

each population-oriented monitor within an area must not exceed 65 ug/m3.

5To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average

ozone concentrations measured at each monitor within an area over each year must not exceed

0.08 ppm.

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Index

Value

PSI

DescriptorGeneral

Health

Effects

Cautionary

Statements

Up to 50 Good None for thegeneral population.

None required.

50 to 100 Moderate Few or none for

the generalpopulation.

None required.

100 to200

Unhealthful Mild aggravation ofsymptoms amongsusceptible people,

with irritationsymptoms in the

healthy population.

Persons withexisting heart orrespiratory

ailments shouldreduce physical

exertion and

outdoor activity.General population

should reducevigorous outdoor

activity.

200 to300

VeryUnhealthful

Significantaggravation of

symptoms anddecreased exercise

tolerance inpersons with heartor lung disease;widespread

symptoms in thehealthy population.

Elderly andpersons with

existing heart orlung disease

should stayindoors and reducephysical activity.General population

should avoidvigorous outdoor

activity.

Over 300 Hazardous Early onset of

certain diseases inaddition to

significantaggravation ofsymptoms and

Elderly and

persons withexisting diseases

should stayindoors and avoidphysical exertion.

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Health Effects of Nitrogen

Oxides Short-term exposure at concentrations greater than

3 parts per million (ppm) can measurably decreaselung function.

Concentrations less than 3 ppm can irritate lungs.

Concentrations as low as 0.1 ppm cause lungirritation and measurable decreases in lung functionin asthmatics.

Long-term lower level exposures can destroy lungtissue, leading to emphysema.

Children may also be especially sensitive to theeffects of nitrogen oxides.

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Other Effects

Seriously injure vegetation at certainconcentrations. Effects include: Bleaching or killing plant tissue.

Causing leaves to fall. Reducing growth rate.

Deteriorate fabrics and fade dyes.

Corrode metals (due to nitrate saltsformed from nitrogen oxides).

Reduce visibility.

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Other Effects (Continued)

Oxides of nitrogen, in the presence of

sunlight, can also react with

hydrocarbons, forming photochemical

oxidants or smog.

Also, NOx is a precursor to acidic

precipitation, which may affect both

terrestrial and aquatic ecosystems.

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Sulfur Dioxide

Ninety-five percent of pollution related sulfuroxide emissions are in the form of sulfurdioxide (SO2), a heavy, colorless gas with anodor like a struck match.

This gas combines easily with water vapor,forming aerosols of sulfurous acid (H2SO3), acolorless, mildly corrosive liquid.

This liquid may then combine with oxygen inthe air, forming the even more irritating andcorrosive sulfuric acid (H2SO4).

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Other sulfur-containing

compounds Hydrogen sulfide (H2S) gas - rotten eggs.

Mercaptans - skunk spray or decayedgarbage. (Added in trace amounts to naturalgas, providing a leak-detecting warning

odor.)

Note: The amount of SO2 released from coalfired power plants depends on the sulfur

content of coal, normally 0.7% to 2% byweight. High sulfur coal sometimes containsas much as 6% sulfur by weight. In India,sulfur content is quite low.

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Health Effects of Sulfur Oxides

Sulfur dioxide not only has a bad odor, it can

irritate the respiratory system.

Exposure to high concentrations for short

periods of time can constrict the bronchi andincrease mucous flow, making breathing

difficult.

Children, the elderly, those with chronic lung

disease, and asthmatics are especially

susceptible to these effects.

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Sulfur dioxide can also:

Immediately irritate the lung and throat atconcentrations greater than 6 parts permillion (ppm) in many people.

Impair the respiratory system's defenses

against foreign particles and bacteria, whenexposed to concentrations less than 6 ppmfor longer time periods.

Apparently enhance the harmful effects of

ozone. (Combinations of the two gases atconcentrations occasionally found in theambient air appear to increase airwayresistance to breathing.)

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Sulfur dioxide tends to have more toxic effects when acidicpollutants, liquid or solid aerosols, and particulates are alsopresent. (In the past, thousands of excess deaths occurred inareas where SO2 concentrations exceeded 1 ppm for a few daysand other pollutants were also high.) Effects are more

pronounced among mouth breathers, e.g., people who areexercising or who have head colds.

These effects include:

Health problems, such as episodes of bronchitis requiringhospitalization associated with lower-level acid concentrations.

Self-reported respiratory conditions, such as chronic cough anddifficult breathing, associated with acid aerosol concentrations.(Asthmatic individuals are especially susceptible to these effects.The elderly and those with chronic respiratory conditions mayalso be affected at lower concentrations than the generalpopulation.)

Increased respiratory tract infections, associated with longerterm, lower-level exposures to SO2 and acid aerosols.

Subjective symptoms, such as headaches and nausea, in theabsence of pathological abnormalities, due to long-termexposure.

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Sulfur oxides Effects on Plants

Sulfur dioxide easily injures many plant species andvarieties, both native and cultivated. Some of themost sensitive plants include various commerciallyvaluable pines, legumes, red and black oaks, white

ash, alfalfa and blackberry. The effects include: Visible injury to the most sensitive plants at

exposures as low as 0.12 ppm for 8 hours.

Visible injury to many other plant types ofintermediate sensitivity at exposures of 0.30 ppm for

8 hours. Positive benefits from low levels, in a very few

species growing on sulfur deficient soils.

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Other Effects

Increases in sulfur dioxide concentrationsaccelerate the corrosion of metals, probablythrough the formation of acids. (SO2 is amajor precursor to acidic deposition.) Sulfur

oxides may also damage stone and masonry,paint, various fibers, paper, leather, andelectrical components.

Increased SO2 also contributes to impairedvisibility. Particulate sulfate, much of whichis derived from sulfur dioxide emissions, is amajor component of the complex totalsuspended particulate mixture.

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Health Effects of Ozone

Ozone acts as a powerful respiratory irritantat the levels frequently found in most of thenation's urban areas during summer months.

Ozone exposure may lead to: Shortness of breath. Chest pain when inhaling deeply.

Wheezing and coughing.

Long-term, repeated exposure to high levels

of ozone may lead to large reductions inlung function, inflammation of the lunglining, and increased respiratorydiscomfort.

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