What Are the Six Common Air Pollutants

8/6/2019 What Are the Six Common Air Pollutants

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What Are the Six Common Air Pollutants?

The Clean Air Act requires EPA to set National Ambient Air Quality Standards for six common air

pollutants. These commonly found air pollutants (also known as "criteria pollutants") are found all

over the United States. They are particle pollution (often referred to as particulate matter), ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. These pollutants can harm

your health and the environment, and cause property damage. Of the six pollutants, particle pollution

and ground-level ozone are the most widespread health threats. EPA calls these pollutants "criteria"

air pollutants because it regulates them by developing human health-based and/or environmentally-

based criteria (science-based guidelines) for setting permissible levels. The set of limits based on

human health is called primary standards. Another set of limits intended to prevent environmental and

property damage is called secondary standards.

Click on one of the pollutants below for information on sources of the pollutant, why the pollutant is of

concern, health and environmental effects, efforts underway to help reduce the pollutant, and other

helpful resources.

y Ozone

y Particulate Matter

y Carbon Monoxidey Nitrogen Oxides

y Sulfur Dioxide

y Lead

y Ozone (O3) is a gas composed of three oxygen atoms. It is not usually emitted directly into

the air, but at ground-level is created by a chemical reaction between oxides of nitrogen (NOx)and volatile organic compounds (VOC) in the presence of sunlight. Ozone has the same

chemical structure whether it occurs miles above the earth or at ground-level and can be

"good" or "bad," depending on its location in the atmosphere.

y In the earth's lower atmosphere, ground-level ozone is considered "bad." Motor vehicle

exhaust and industrial emissions, gasoline vapors, and chemical solvents as well as natural

sources emit NOx and VOC that help form ozone. Ground-level ozone is the primary

constituent of smog. Sunlight and hot weather cause ground-level ozone to form in harmful

concentrations in the air. As a result, it is known as a summertime air pollutant. Many urban

areas tend to have high levels of "bad" ozone, but even rural areas are also subject to

increased ozone levels because wind carries ozone and pollutants that form it hundreds of

miles away from their original sources.

y "Good" ozone occurs naturally in the stratosphere approximately 10 to 30 miles above the

earth's surface and forms a layer that protects life on earth from the sun's harmful rays. Learn


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more about how ozone can be beneficial up high in the stratosphere but harmful at ground

level.

Basic Information

Ground-level or "bad" ozone is not emitted directly

into the air, but is created by chemical reactions

between oxides of nitrogen (NOx) and volatile

organic compounds (VOC) in the presence of

sunlight. Emissions from industrial facilities and

electric utilities, motor vehicle exhaust, gasoline

vapors, and chemical solvents are some of the major

sources of NOx and VOC.

Breathing ozone, a primary component of smog, can

trigger a variety of health problems including chest

pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma.

Ground-level ozone also can reduce lung function and inflame the linings of the lungs. Repeated

exposure may permanently scar lung tissue.

Ground-level ozone also damages vegetation and ecosystems. In the United States alone, ozone is

responsible for an estimated $500 million in reduced crop production each year.

Under the Clean Air Act, EPA has set protective health-based standards for ozone in the air we

breathe. EPA and others have instituted a variety of multi-faceted programs to meet these health-

based standards. More about EPA s ozone standards andregulatory actions.

Throughout the country, additional programs are being put into place to cut NOx and VOC emissions

from vehicles, industrial facilities, and electric utilities. Programs are also aimed at reducing pollution

by reformulating fuels and consumer/commercial products, such as paints and chemical solvents that

contain VOC. Voluntary and innovative programs also encourage communities to adopt practices, such

as carpooling, to reduce harmful emissions. More about EPAs innovative programs to reduce air

pollution.

Sunlight and hot weather help form ground-level ozone. Both also contribute to global

warming and heat island effect.


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"Particulate matter," also known as particle pollution or PM, is a complex mixture of extremely small

particles and liquid droplets. Particle pollution is made up of a number of components, including acids

(such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles.

The size of particles is directly linked to their potential for causing health problems. EPA is concerned

about particles that are 10 micrometers in diameter or smaller because those are the particles that

generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can

affect the heart and lungs and cause serious health effects. EPA groups particle pollution into two

categories:

y "Inhalable coarse particles," such as those found near roadways and dusty industries, arelarger than 2.5 micrometers and smaller than 10 micrometers in diameter.

y "Fine particles," such as those found in smoke and haze, are 2.5 micrometers in diameter andsmaller. These particles can be directly emitted from sources such as forest fires, or they can

form when gases emitted from power plants, industries and automobiles react in the air.

y Basic Informationy Particle pollution (also called particulate matter or PM) is the term for a mixture of solid

particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or

smoke, are large or dark enough to be seen with the naked eye. Others are so small, they can

only be detected using an electron microscope.

y Particle pollution includes "inhalable coarse particles,"

with diameters larger than 2.5 micrometers and smaller

than 10 micrometers and "fine particles," with diametersthat are 2.5 micrometers and smaller. How small is 2.5

micrometers? Think about a single hair from your head.

The average human hair is about 70 micrometers in

diameter making it 30 times larger than the largest fine

particle.

y These particles come in many sizes and shapes and can

be made up of hundreds of different chemicals. Some

particles, known asprimary particles are emitted directly from a source, such as construction

sites, unpaved roads, fields, smokestacks or fires. Others form in complicated reactions in the

atmosphere of chemicals such as sulfur dioxides and nitrogen oxides that are emitted frompower plants, industries and automobiles. These particles, known as secondary particles,

make up most of the fine particle pollution in the country.

y EPA regulates inhalable particles (fine and coarse). Particles larger than 10 micrometers (sand

and large dust) are not

How Big is Particle

Pollution?


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Health and Environment

The size of particles is directly linked to their potential for causing health problems. Small particles

less than10 micrometers in diameter pose the greatest problems, because they can get deep into your

lungs, and some may even get into your bloodstream.

Exposure to such particles can affect both your lungs and your heart. Small particles of concern

include "inhalable coarse particles" (such as those found near roadways and dusty industries), which

are larger than 2.5 micrometers and smaller than 10 micrometers in diameter; and "fine particles"

(such as those found in smoke and haze), which are 2.5 micrometers in diameter and smaller.

The Clean Air Act requires EPA to set air quality standards to protect both public health and the public

welfare (e.g. crops and vegetation). Particle pollution affects both.

Health Effects

Particle pollution - especially fine particles - contains microscopic solids or liquid droplets that are so

small that they can get deep into the lungs and cause serious health problems. Numerous scientific

studies have linked particle pollution exposure to a variety of problems, including:

y increased respiratory symptoms, such as irritation of the airways, coughing, or difficultybreathing, for example;

y decreased lung function;y aggravated asthma;

y development of chronic bronchitis;

y

irregular heartbeat;y nonfatal heart attacks; and

y premature death in people with heart or lung disease.

People with heart or lung diseases, children and older adults are the most likely to be affected by

particle pollution exposure. However, even if you are healthy, you may experience temporarysymptoms from exposure to elevated levels of particle pollution. For more information about asthma,

visit www.epa.gov/asthma.

Environmental Effects

Visibility reduction

Fine particles (PM2.5) are the major cause of reduced visibility (haze) in parts of the United States,

including many of our treasured national parks and wilderness areas. For more information about

visibility, visit www.epa.gov/visibility.

Environmental damage

Particles can be carried over long distances by wind and then settle on ground or water. The effects of


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this settling include: making lakes and streams acidic; changing the nutrient balance in coastal waters

and large river basins; depleting the nutrients in soil; damaging sensitive forests and farm crops; and

affecting the diversity of ecosystems. More information about the effects of particle pollution and acid

rain.

Aesthetic damage

Particle pollution can stain and damage stone and other materials, including culturally important

objects such as statues and monuments. More information about the effects of particle pollution and

acid rain.

1Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as "oxides of nitrogen,"

or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous acid and nitric acid. While EPAs

National Ambient Air Quality Standard covers this entire group of NOx, NO2 is the component of

greatest interest and the indicator for the larger group of nitrogen oxides. NO2 forms quickly from

emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to

contributing to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with a

number of adverse effects on the respiratory system.

EPA first set standards for NO2 in 1971, setting both a primary standard (to protect health) and a

secondary standard (to protect the public welfare) at 0.053 parts per million (53 ppb), averaged

annually. The Agency has reviewed the standards twice since that time, but chose not to revise the

standards at the conclusion of each review. All areas in the U.S. meet the current (1971)

NO2 standards.

Health

Current scientific evidence links short-term NO2 exposures, ranging from 30 minutes to 24 hours, with

adverse respiratory effects including airway inflammation in healthy people and increased respiratory

symptoms in people with asthma.

Also, studies show a connection between breathing elevated short-term NO2 concentrations, and

increased visits to emergency departments and hospital admissions for respiratory issues, especially

asthma.


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NO2 concentrations in vehicles and near roadways are appreciably higher than those measured at

monitors in the current network. In fact, in-vehicle concentrations can be 2-3 times higher than

measured at nearby area-wide monitors. Near-roadway (within about 50 meters) concentrations of

NO2 have been measured to be approximately 30 to 100% higher than concentrations away from

roadways.

Individuals who spend time on or near major roadways can experience short-term NO2 exposures

considerably higher than measured by the current network. Approximately 16% of U.S housing units

are located within 300 ft of a major highway, railroad, or airport (approximately 48 million people).

This population likely includes a higher proportion of non-white and economically-disadvantaged

people.

NO2 exposure concentrations near roadways are of particular concern for susceptible individuals,

including people with asthma asthmatics, children, and the elderly

The sum of nitric oxide (NO) and NO2 is commonly called nitrogen oxides or NOx. Other oxides of

nitrogen including nitrous acid and nitric acid are part of the nitrogen oxide family. While EPAs

National Ambient Air Quality Standard (NAAQS) covers this entire family, NO2 is the component of

greatest interest and the indicator for the larger group of nitrogen oxides.

NOx react with ammonia, moisture, and other compounds to form small particles. These small

particles penetrate deeply into sensitive parts of the lungs and can cause or worsen respiratory

disease, such as emphysema and bronchitis, and can aggravate existing heart disease, leading to

increased hospital admissions and premature death.

Ozone is formed when NOx and volatile organic compounds react in the presence of heat and sunlight.

Children, the elderly, people with lung diseases such as asthma, and people who work or exercise

outside are at risk for adverse effects from ozone. These include reduction in lung function and

increased respiratory symptoms as well as respiratory-related emergency department visits, hospital

admissions, and possibly premature deaths.

Emissions that lead to the formation of NO2 generally also lead to the formation of other NOx.

Emissions control measures leading to reductions in NO2 can generally be expected to reduce

population exposures to all gaseous NOx. This may have the important co-benefit of reducing the

formation of ozone and fine particles both of which pose significant public health threats.

Sulfur dioxide (SO2) is one of a group of highly reactive gasses known as oxides of sulfur. The

largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other

industrial facilities (20%). Smaller sources of SO2 emissions include industrial processes such as


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extracting metal from ore, and the burning of high sulfur containing fuels by locomotives, large ships,

and non-road equipment. SO2 is linked with a number of adverse effects on the respiratory system.

EPA first set standards for SO2 in 1971. EPA set a 24-hour primary standard at 140 ppb and an

annual average standard at 30 ppb (to protect health). EPA also set a 3-hour average secondary

standard at 500 ppb (to protect the public welfare).

The last review of the SO2 NAAQS was completed in 1996 and the Agency chose not to revise the

standards. In the last review, EPA also considered, but did not set, a five minute NAAQS to protect

asthmatics at elevated ventilation rates from bronchoconstriction and respiratory symptoms

associated with 5-10 minute peaks of SO2.

NATIONAL AMBIENT AIR QUALITY STANDARDS*

PollutantTime WeightedAverage

Concentration in Ambient Air

Industrial AreaResidential, Ruraland other

Sensitive Area

Sulphur Dioxide

(SO2)

Annual

24 hours

80 g/m3

120 g/m3

60 g/m3

80 g/m3

15 g/m3

30 g/m3

Oxides of

Nitrogen (NO2)

Annual

24 hours

80 g/m3

120 g/m3

60 g/m3

80 g/m3

15 g/m3

30 g/m3

Suspended

Particulate Matter(SPM)

Annual

24 hours

360 g/m3

500 g/m3

140 g/m3

200 g/m3

70 g/m3

100 g/m3

Respirable **

Particulate Matter(RPM)

Annual

24 hours

120 g/m3

150 g/m3

60 g/m3

100 g/m3

50 g/m3

75 g/m3

Lead (pb)

Annual

24 hours

1.0 g/m3

1.5 g/m3

0.75 g/m3

1.00 g/m3

0.50 g/m3

0.75 g/m3

Carbon

Monoxide(CO)

8 hours

1 hour

5.0 g/m3

10.0 g/m3

2.0 g/m3

4.0 g/m3

1.0 g/m3

2.0 g/m3

* Ministry of Environment and Forests, Government of India notification,1994

** Particle size less than 10


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Air Pollution

AMBIENT AIR QUALITY STANDARDS (NATIONAL)Pollutants Time-

weightedaverage

Concentration in ambient air Method of measurementIndustrialAreas

Residential,Rural &

other Areas

SensitiveAreas

SulphurDioxide(SO2)

AnnualAverage*

80 g/m3 60 g/m3 15 g/m3 - Improved West and Geake

Method- Ultraviolet Fluorescence

24 hours** 120 g/m3 80 g/m3 30 g/m3

Oxides ofNitrogen as(NO2)

AnnualAverage*

80 g/m3 60 g/m3 15 g/m3 - Jacob & Hochheiser Modified

(Na-Arsenite) Method24 hours** 120 g/m3 80 g/m3 30 g/m3 - Gas Phase

ChemiluminescenceSuspendedParticulate Matter(SPM)

AnnualAverage*

360 g/m3 140 g/m3 70 g/m3 - High Volume Sampling,

(Average flow rate not less than1.1 m3/minute).

24 hours** 500 g/m3 200 g/m3 100 g/m3

RespirableParticulateMatter (RPM) (sizeless than 10 microns)

AnnualAverage*

120 g/m3 60 g/m3 50 g/m3 - Respirable particulate matter

sampler24 hours** 150 g/m3 100 g/m3 75 g/m3

Lead (Pb) AnnualAverage*

1.0 g/m3 0.75 g/m3 0.50 g/m3- ASS Method after sampling

using EPM 2000 or equivalentFilter paper

24 hours** 1.5 g/m3 1.00 g/m3 0.75 g/m3.Ammonia1 Annual

Average*0.1 mg/ m3 0.1 mg/ m3 0.1 mg/m3.

24 hours** 0.4 mg/ m3 0.4 mg/m3 0.4 mg/m3.

CarbonMonoxide(CO)

8 hours** 5.0 mg/m3 2.0 mg/m3 1.0 mg/ m3- Non Dispersive Infra Red(NDIR)

1 hour 10.0 mg/m3 4.0 mg/m3 2.0 mg/m3Spectroscopy

* Annual Arithmetic mean of minimum 104 measurements in a year taken twice aweek 24 hourly at uniform interval.

** 24 hourly/8 hourly values should be met 98% of the time in a year. However, 2% ofthetime, it may exceed but not on two consecutive days.

NOTE:

1. National Ambient Air Quality Standard: The levels of air quality with anadequate margin of safety, to protect the public health,, vegetation andproperty.


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which some 4000 died, were associated with widespread use of dirty polluting fuels.

Since then, many countries have adopted ambient air quality standards to safeguardthe public against the most common and damaging pollutants, which include sulphur

dioxide, suspended particulate matter, ground level ozone, nitrogen dioxide, carbon

monoxide and lead, which are directly or indirectly released by the combustion of

fossil fuels. Although substantial investments in pollution control in some countrieshave lowered the levels of these pollutants in many cities, poor air quality is still a

major concern throughout the industrialized world.

1.1 Indoor Air Pollution

There are four principal sources of pollutants in indoor air viz. combustion, buildingmaterial, the ground under the building and biological agents. As dangerous as

polluted outdoor air can be to health, indoor air pollutants can pose even a greater

health risk. Indoor air pollution is a concern where energy efficiency improvements

sometimes makes the house relatively air tight thereby reducing ventilation andraising indoor pollutant levels. Indoor air pollution is usually associated with

occupational situation particularly through combustion of biomass fuels. The greatest

threat of indoor pollution exists where the people continue to rely on traditional fuelsfor cooking and heating. Burning such fuels produces large amounts of smoke and

other air pollutants in the confined space of home, a perfect recipe for high exposures.

Liquid and gaseous fuels such as kerosene and bottled gas although not completely pollution free is many times less polluting than unprocessed solid fuels (Fig 2). In

these circumstances, exposure to pollutants is often far higher indoors than outdoors.

The health problems due to indoor air pollutants are more widespread than those

caused by outdoor air pollutants for the following reasons.


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y The exposed persons are in close proximity to the source of indoor air

pollutants.

y A recent report of WHO asserts 'the rule of 1000' which states that a pollutant

released indoor is one thousand times more likely to reach the lungs than a

pollutant released outdoors.y Women and children, particularly those in rural sector spend more time

indoors than outdoors.

y In rural areas, indoor air pollution is responsible for much greater mortality

than ambient air pollution.

Epidemiological studies have linked exposure to indoor air pollution from dirty fuels

with at least four major categories of illness. These are:

y acute respiratory infections (ARI) in children

y chronic obstructive pulmonary disease (COPD) such as asthma and bronchitis;y lung cancer and

y pregnancy related problems. Of these, ARI appears to have the greatest health

impact in terms of the number of people affected .

Traditional biomass fuels amount for 80% of domestic energy consumption in ourcountry. When these fuels are burnt in simple cook stoves during meal preparation, air

inside homes get heavily polluted with smoke that contains large amounts of toxic

pollutants such as carbon monoxide, oxides of nitrogen (NOx), sulphur dioxide (SO2),aldehydes, dioxins, polycyclic aromatic hydrocarbons and respirable particulate

matter. The resulting human exposures exceed the permissible norms by a factor inmultiples.

SOME KEY FINDINGS OF INDOOR AIR POLLUTION STUDIES

(ESMAP,World Bank 2000)y Exposure to biomass smoke increases the risk of acute respiratory infection

(chest infection, coughs, colds and middle ear infections). Children in the

Gambia Island found riding on their mother's back, during cooking over smokystoves were more likely to develop Acute Respiratory Infection (ARI) then

unexposed children.

y A study in Tanzania reported that the children below five years age died of

ARI, were more likely to sleep in a room with an open cook stove than healthy

children in the same age group.


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Source: Indoor Air Quality, ESMAP, World Bank, September 2000


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Source: Indoor Air Quality, ESMAP, World Bank, 2000

Major Air Pollution Episodes

MEUSE VALLEY, BELGIUM (1930)

A strong atmospheric inversion got settled over Meuse Valley on December 1, 1930 and remained until

December 5. Effluents from several factories in the valley, chiefly oxides of sulphur, various inorganicacids, metallic oxides, and soot were then trapped in the stable atmosphere. Sixty three people (generally

the old and infirm) died, and several hundred others deemed ill. Although many suspected sulphur oxidesand hydrofluoric acid, the actual lethal substance could not be proved.


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DONORA, PENNSYLVANIA, 1948

Donora, Pennsylvania is an industrial town on the banks of the Monongahela River about 30 miles south

of the heart of Pittsburgh. The major industrial installations were steel and wire mill, a zinc smelter and asulphuric acid plant. During a particularly calm and meteorologically stable period from October 27 to

31, 1948, air pollutants accumulated because of this many people were hospitalized and 20 died. Illnessof several thousand persons was blamed on the episode, and over 130 separate lawsuits were filed. The

causative agent of the deaths and illness could never be determined incontrovertibly but sulphurcompounds were present in the air in abnormally high quantities.

LONDON SMOG, 1952

Historically, the longest record of intermittent air pollution problems belongs to the city of London,England. The notorious pea-soup fogs become especially offensive when mixed with coal smoke. The

word smog (smoke and fog) was coined to describe this foul condition. In 1661, John Evelyn got published his well-known pamphlet, 'Fumifugium: or The Inconvenience of the Air and Smoke of

London Dissipated'. His major recommendation had been the removal of all smoke-producing plantsfrom London. But London did little about it until the famous London smog of December 1952, truly a

major air pollution disaster. The smog lasted 5 days from 5th

to 9thDecember and caused 4000 deaths

(principally among the old, the infirm, and those with respiratory diseases). The onset of fog was

followed by acute respiratory symptoms. Almost exactly ten years later, December 3 to 7, 1962 Londonexperienced another black fog, with 340 excess deaths. The improvement over the 1952 episode was laid

to smoke reduction brought about by the Clean Air Act and public awareness of the harmful effects ofsmog, which restrained many respiratory cripples from going outdoors.

BHOPAL MIC GASTRAGEDY(1984)

The Methyl Isocyanate (MIC) gas leak in Bhopal during 1984 has been regarded the worst industrialaccident in India, which is related to air pollution. Around 2,00,000 people were affected by the leak ofpoisonous Methyl isocyanate gas from a pesticide plant. The actual scenario of what went wrong at the

Bhopal plant just after the midnight on the morning of December 3, 1984 is not exactly known. Butseveral circumstantial evidences point to the total breakdown of the essential safety provisions within the

plant. MIC can react with almost any chemical to generate considerable heat and CO2. The heat releasedaccelerates the reaction and pressure goes on building up till it reaches an explosive level. The gas

emitted from the factory spread over some 40 sq. kms area and affected people seriously as distant as 5kms. MIC is invariably accompanied by Phosgene (COCl2). The toxic effect of MIC is enhanced by

COCl2.

SULPHUR DIOXIDE AND ITS HEALTH EFFECTS

Sulphur dioxide (SO2 ) is a colourless gas readily soluble in water. Natural sources

such as sulphur bacteria activities, volcanoes, forest fires etc. contribute to


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environmental levels of SO2. Man made contributions include the use of sulphur

containing fossil fuels for transportation, domestic purposes and power generation. Ofgreater interest, with respect of outdoor air quality are the effects on health, of the

lower concentration to which human beings may be exposed in the ambient air. The

effects have been studied in a number of different ways, including exposure of

volunteers to sulphur dioxide in the air, which they breath and by examination ofeffects on members of the population who have been exposed to episodes of

atmospheric pollution.

Sulphur dioxide causes its irritant effects by stimulating nerves in the lining of the

nose, throat and the lung airways. This later affects the people suffering from asthma

and chronic lung disease, whose airways get inflamed and easily irritated. Studies of

normal healthy volunteers, exposed to sulphur dioxide in chambers have shown that

measurable narrowing of the airways may occur after breathing the gas for 5 minutesat concentration of 4-5 ppm but the effects were not detectable at concentrations

below 1 ppm. The most common acute exposure to SO2 concentration 0.4 ppm is

indication of broncho-constriction in asthmatics after exposure lasting only 5 minutes.The effects of SO2 on airway of asthmatics are reversible with recovery occurring

within one hour. Exposure at lower levels can cause increased upper respiratory

symptoms such as cough, sore throat and changes in lung function. The morbidityeffects are associated with long-term exposure to particulates and or sulphur dioxide.

The acidic aerosols composed of particulate matter and acids cause inflammation of

airways and lungs and reduce the ability of small airways to clear mucous andparticles. The health morbidity indices are lung function decrement, upper and lower

respiratory disease symptoms, increase in rates for cough, bronchitis and other health

problems.

Table 4 Summary of Health Effects of Basic Air Pollutants

Pollutant Health Effects

Carbon Monoxide Poor reflexes

Ringing in the ears

Headache

Dizziness

Nausea

Breathing Difficulties


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Drowsiness

Reduced work capacity

Comatose state (can lead to death)

Lead (Pb) Kidney Damage

Reproductive system damage

Nervous system damage (including brain dysfunction and

altered neurophysical behaviours)

Oxides of Nitrogen

(NOX )

Increased risk of viral infections

Lung irritation (including pulmonary fibrosis and

emphysema)

Higher respiratory illness rates

Airway resistance

Chest tightness and discomfort

Eye burning

Headache

Ozone (O3) Respiratory system damage (lung damage from freeradicals)

Reduces mental activity

Damage to cell lining (especially in nasal passage)

Reduces effectiveness of the immune system

Headache

Eye irritation

Chest discomfort

Breathing difficulties

Chronic lung diseases ( including asthma and

emphysema)


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Nausea

Sulphur dioxide (SO2) Aggravates heart and lung diseases

Increases the risk for respiratory illness (including

chronic bronchitis, asthma, pulmonary emphysema)

Cancer ( may not show for decades after exposure)

Respirable Particulate

Matter (PM10)

Respiratory illness (including chronic bronchitis,increased asthma attacks, pulmonary emphysema)

Aggravates heart disease

NITROGEN DIOXIDE AND ITS HEALTH EFFECTS

Oxides of nitrogen are released in all the types of combustion as they are formed by

the oxidation of atmospheric nitrogen at high temperature. Nitric oxide usually

emitted from the automobile exhaust is oxidised to nitrogen dioxide (NO2) by reaction

with oxidants (prominently ozone) present in the ambient air. Nitrogen dioxide is a

reddish brown gas with a characteristic pungent odour. It is corrosive and a strong

oxidising agent. Nitrogen dioxide is the predecessor of gaseous nitric acid and nitrateaerosols, which has the biggest health impact. The major sources of NO2 are

combustion-associated processes, such as motor vehicles, power plants as well as anyhigh temperature combustion process used in industrial work. Oxides of nitrogen

particularly nitrogen dioxide are toxic gases. The uptake of these gases in human body

occur during breathing. Large percentage of inhaled NO2 is removed in the respiratory

tract, which depend on mode of breathing, ventilation rate, increased penetration ofNO2 to lower respiratory tract. Some of the major health effects of NO2 exposure are

as follows

Table 5 Average Concentration Levels of Air Pollutants on Exposure Assessment

Pollutant Personal

Exposure

Occupational

Exposure

Residential

Exposure

Ambient Air

Quality

NAA

PM (g/m3) 330 175

(RPM5)

358 187

(RPM5)

308 225

(RPM5)

140 102

(PM10)

100

(PM


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NOx (ppb) 2.4 3.4 2.0 BDL 3.2

CO(ppm) 2.4 3.4 2.0 BDL 3.2

Pb (g/m3) 2.32 1.28 2.6 2.5 2.47 2.16 0.34 0.25 1.0

K(g/m3) 7.7 6.9 7.9 10.71 6.32 2.74 0.54 .042 -

Mn(g/m3) 0.33 0.41 0.55 0.64 0.12 0.13 0.15 0.18 -

Cd (g/m3) 0.15 0.16 0.27 0.39 0.06 0.35 0.017 0.027 -

PAH (ng/m3) 23.83 42.36 5.2 21.2 -

B(a)P(g/m3) 2.69 4.89 0.48 1.4 -

Source: CPCB Report PROBES/77/200-01

Airway Reactivity and Pulmonary Effects

Nitrogen dioxide exposure can cause decrement in lung function (i.e. increased airway

resistance), increased airway responsiveness to broncho-constrictions in healthy

subjects at concentration exceeding 1 ppm. Below 1 ppm level, there are evidences ofchange in lung volume, flow volume, characteristics of lung or airway resistance in

healthy persons. It has been established that continuous exposure with as little as 0.1

ppm NO2 over a period of one to three years, increases incidence of bronchitis,

emphysema and have adverse effect on lung performance.

Respiratory Morbidity in Childern

The dysfunction of host defence, increased susceptibility to infections are generally

caused due to affects on muco-ciliary clearance, functional and bio-chemical activity

of alveolar macrophages and immunological competence. Exposure to excessive NO2,

affect the defence mechanism leaving the host susceptible to respiratory illness.

Chronic Lung Disease

Nitrogen dioxide exposure may lead to chronic lung disease and variety of

structural/morphological changes in lung epithelium conducting airways and air -gas

exchange region. Exposure to high levels (>1.0 ppm) of NO2 cause estuation of

bronchiolar and alveolar epithelium, inflammation of epithelium and definite

emphysema.


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Effects on Immune System and Host Defence

Nitrogen dioxide in large doses can result in dysfunction of host defences by causing

structural alteration in ciliated cells of mucociliary escalator, in alveolar macrophages,decrease in phagocytosis, morphological and metabolic changes. The respiratory tract

provide first time protective barrier against inhaled, viable and non-viable airborneagent. Breaches in defence system might increase the risk of diseases.

CARBON MONOXIDE AND ITS HEALTH EFFECTS

Carbon monoxide (CO) is a colourless, odourless and tasteless gas with relatively

poor solubility in water. Anthropogenic emissions of CO originate primarily from

incomplete combustion of carbonaceous materials. The largest carbon monoxide

emissions are produced as exhaust of internal combustion engines, especially of

vehicles with petrol engines.

The lungs are the only significant routes for CO uptake from the environment. Carbonmonoxide diffuses rapidly across alveolar, capillary and placental membranes. Inhaled

CO has no direct toxic affects on lungs but rather appears to exert its effects by

interfering with oxygen transport through the formation of carboxy-haemoglobin(COHb). Exposure to CO is often evaluated in terms of COHb levels in blood

measured as percentage of total Hb bound CO. Approximately 80% to 90% of

absorbed CO binds with haemoglobin to form carboxy-haemoglobin, which reducethe oxygen carrying capacity of the blood and impair the release of oxygen from

haemoglobin (Table 7). COHb levels in non-smokers range between 0.3% to 0.7%

and 5% to 7% in smokers. COHb levels in excess of 15% in a significant proportionof urban non-smoking populations can be considered as evidence of widespread

exposure to environmental carbon monoxide.

In a study conducted under controlled laboratory conditions, healthy subjects exposed

to CO, sufficient to result in 5% COHb levels exhibited reduced duration of exercise

performance and consumption of oxygen. Studies involving subjects with deficient blood supply to the heart (Ischemic Heart Disease) who were engaged in exercise

during exposures have shown that COHb levels as low as 2.2% can lead to:

a. earlier onset of electrocardiograph change indicative of increased deficiency ofoxygen supply to the heart;

b. earlier onset of chest pain;c. increase in the duration of chest pain; and


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d. decrease in oxygen consumption.

Table 6 Symptoms Based on Blood Carboxy-haemoglobin Levels

Table 7 Symptoms Based on Carbon monoxide in Ambient Air

CO (PPM) Exposure Symptoms

35 8 hours Maximum exposure limit allowed by OSHA in the workplace over an eigperiod.

200 2-3 hours Mild headache, fatigue, nausea and dizziness

400 1-2 hours Serious headache and other symptoms intensify. Life threatening after 3 ho

800 45 minutes Dizziness, nausea and convulsions. Unconscious within 2 hours followed within 2-3 hours

COMMON RESPIRATORY DISEASES RELATED TO AIR POLLUTION

13.1 Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) which encompasses chronic

bronchitis and emphysema is one of the commonest respiratory disease. In the westernworld, COPD is probably the fourth commonest cause of death in middle aged to

elderly men after ischemeic heart disease, lung cancer and cardiovascular disease.According to 'Dutch Hypothesis', asthma, emphysema and chronic bronchitis are

different manifestations of a single disease.

13.1.1 Bronchitis

Bronchitis is a type of swelling in the bronchial tubes which are the air passages

leading from the windpipe to the lungs. When these passages become clogged with

thick mucus that prevent air from flowing freely to and from the lungs the body'snatural reflex is to try to cough up this mucus to clear the airways.

Acute Bronchitis

Acute bronchitis is usually a short, severe illness that may show up along with cold or

follow other viral infections such as measles or whooping cough.


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Chronic Bronchitis

Chronic bronchitis is a long term, serious condition characterized by frequent

coughing and mucus production and often happens along with another lung diseasecalled emphysema. In severe cases, when the bronchial tubes become narrowed and

clogged with mucous, the resulting lack of oxygen in the blood may give the skin abluish colour.

13.1.2 Emphysema

Emphysema is a condition in which there is over inflation of structure in the lungs

known as alveoli or air sacs. This over inflation results from a breakdown of the walls

of the alveoli, which causes a decrease in respiratory function and often

breathlessness. Early symptoms of emphysema include shortness of breath and cancer.

Emphysema begins with the destruction of air sacs (alveoli) in the lungs whereoxygen from the air is exchanged for carbon dioxide in the blood. The walls of the airsacs are thin and fragile. Damage to the air sacs is irreversible and results in

permanent 'holes' in the tissues of the lower lungs. As air sacs are destroyed, the lungs

are able to transfer less and less oxygen to the bloodstream, causing shortness ofbreath. The lungs also loose their elasticity. Emphysema doesn't develop suddenly, it

comes on very gradually, and years of exposure to the air pollutants or cigarette

smoke usually precede the development of emphysema.

13.1.3 Asthma

Asthma is a disease in which the breathing tubes (also known as airways or bronchi)

get narrowed and the person experiences difficulty in breathing. What causes this

process is a biologically active compound called Leukotriene which, in turn is formed

by the oxidation of Arachiodonic acid (AA) . This phenomenon causes the asthmatic

symptoms e.g., wheezing, coughing or difficulty in breathing. Asthma is one of the

biggest worldwide public health problem. As per WHO report 15 to 20 million

Asthmatic cases are in India and over 150 million worldwide. As per WHO reportthere has been about 40% increase in asthma cases during the last decade worldwide.

Although asthma is considered primarily a disease of airways, virtually all aspects of

pulmonary functions are compromised during an acute attack. Common causes ofasthma are:

n Cigarette Smoke

n Wood Smoke


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n Chemical fumes

n Cleaning agents (such as phenyl)

n Perfumes and hair sprays

n Strong odours while cooking, especially frying

n Atmospheric pollution (industrial or through automobile exhaust fumes)

Asthmatics suffer from breathing difficulty associated with whistling or wheezing

sound in breathing. Along with these there is cough and phlegm production and chest

tightness, very often, sleep is disturbed and the patient may have limitation in carrying

out daily activities.

13.2 Respiratory Mechanism

The lungs and skin (including nose and ages) are the organs of first contact for most

of the environmental exposures.

The human body accomplishes 75 percent of its energy requirement through

breathing. By breathing we take in oxygen, the most fundamental unit of fuel. Further

we eliminate 70 percent of toxins via the breath. Oxygen also cleanses the cells byoxidation and enables waste products to be carried back to the lungs via the blood

stream.

Good breathing according to the standards of medical texts and the World HealthOrganization, is about four to six litres air per minute. During attacks, it may go up to

27 litres per minute. The betterment in the breathing patterns means less number of


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breaths per minute. Twelve breaths per minute would be about the upper limit of what

we should be breathing, even less than that is better. Stress, anxiety and emotions allstimulate our breathing rate and heart rate. The strongest immediate stimulus to our

breathing comes through stress, from our sympathetic nervous system.

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What Are the Six Common Air Pollutants

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