AIR POLLUTION

AIR POLLUTION

INTRODUCTION

Air

• A mixture of gases that surrounds the earth and makes up our atmosphere

• Human beings need a relatively constant continuous supply of air to exist (10-20 m³ per day)

Air and atmospheric conditions influence our lives in a number of ways.

• Supplies the life giving oxygen

• Contact with air cools the body

• Special senses of hearing and smell function through air transmitted stimuli

• Disease agents may be transmitted through air

• Air pollution results in morbidity and mortality

COMPOSITION

External air consists by volume approximately

• 20.93% Oxygen,

• 78.1% Nitrogen,

• 0.03% of Carbon dioxide plus traces of other substances and gases (e.g.

argon, neon, krypton, helium etc.) both natural and man-made

Composition of outdoor air is kept constant &

cleansed by--Wind, Sunlight, Rain, Plant life

Many activities render the air impure such as

• Respiration by human and animals

• Combustion of coal, gas, oil etc

• Decomposition of organic matter

• Trade, traffic and manufacturing processes giving off dust, fumes, vapours and gases etc.

An imbalance between the rate of pollution and

the cleansing process constitutes a health hazard

AIR OF THE OCCUPIED ROOM

Chemical changes:

The air becomes contaminated by CO₂ (per capita output in a mixed gathering is 0.6 c.ft. per hour) & oxygen content decreases

Physical changes:

• Rise in temperature (400 BTU per hour)

• Increase of humidity (700 gms of water vapour per 24 hours as perspiration at rest)

• Decrease in air movement

• Body odours

• Bacterial pollution: Saprophytic/ Pathogenic

DISCOMFORT

It is a subjective feeling or sensation which people experience in ill ventilated and over-crowded place (Black hole of

Kolkata)

It is physical & not the chemical changes which lead to discomfort (as a result of heat retention)

Physical factors determine the cooling power of the air The problems of ventilation are physical not chemical;

cutaneous not respiratory

INDICES OF THERMAL COMFORT

Air temperature

Air temperature + Humidity

Cooling power: Air temp.+ Humidity + Air movement (measured by Kata thermometer, devised by Hill)

Effective temperature: Arbitrary index that combines temp., humidity & movement of internal air (obtained by special charts)

Corrected effective temperature (CET): Includes

radiant heat along with the above & measured by

Globe thermometer

COMFORT

Complex subjective experience, which depends not only on physical, physiological factors, but also on psychological factors, which are difficult to determine

Comfortable thermal conditions: Under which a person can maintain normal balance between production & loss of heat, at normal body temperature & without sweating

Range of effective temperatures over which the

majority of adults feel comfortable

COMFORT THERMAL ZONES IN INDIA

Pleasant & cool -20 deg. C Comfortable & cool -20-25 deg. C

Comfortable -25-27 deg. C

Hot & uncomfortable -27-28 deg. C

Extremely hot -28+ deg. C

Intolerably hot -30+ deg. C

AIR-POLLUTION

• Signifies the presence in the ambient (surrounding) atmosphere of substances (e.g., gases, mixture of gases and particulated matter) generated by the activities of man in concentrations that interfere with human health, safety or comfort, or injurious to vegetation and animals and other environmental media resulting in chemicals entering the food chain or being present in drinking water and thereby constituting additional source of human exposure

Air pollution may be classified as --

-- Outdoor

Recognizes no geographical or political

boundaries and is currently a global health

problem

DEFINITIONS

Primary air pollutants: Are those that are emitted into the atmosphere from a source such as a factory chimney or exhaust pipe, or through suspension of contaminated dusts by the wind

Secondary air pollutants: Formed within the atmosphere itself;

arise from chemical reactions of primary pollutants Gaseous air pollutants: Present as gases or vapours

Particulate air pollutants: Comprise material in solid or liquid phase suspended in atmosphere

Local scale: Encountered in appreciable concentrations close to where they are emitted

Urban scale: Tend to be present in high conc. throughout the city and at significantly reduced conc. in adjacent rural areas

Regional scale: Fine particles (<2.5 micron) but not ultrafine and some gas phase pollutants such as ozone have atmospheric lifetimes of days or even weeks which permit them to be transported on a regional scale

Hemispheric and global scale: Those associated with green house warming effects (carbon dioxide, nitrous oxide etc.) have atmospheric lifetime of years are capable of distribution throughout a hemisphere and ultimately globally

SOURCES OF AIR POLLUTION

1. Automobiles: Mainly in urban areas; Emit

hydrocarbons, carbon monoxide, lead, nitrogen oxides and particulate matter

2. Industries: Emit smoke, sulphur dioxides, nitrogen oxides, fly ash

3. Domestic sources: Major source of smoke, sulphur dioxides, nitrogen oxides

4. Tobacco smoke:

5. Miscellaneous: Burning refuse, incinerators, pesticide

spraying, wind borne dust, fungi, molds, bacteria and

nuclear energy

AIR POLLUTANTS

It is only the first 30 km of earth’s atmosphere that hold major portion of the atmospheric gases

Man is most directly concerned with only the 8-10 km of atmosphere

May be in the form of solids, liquids (vapours) or gases

Differ greatly from place to place depending on the

specific complex of contaminant source

AIR POLLUTANTS

i. Carbon monoxide

One of the most common and widely distributed air pollutant An odourless gas which when inhaled, reduces the body’s

ability to use oxygen

The principal human source of CO is from incomplete combustion of carbon containing materials such as in automobiles, industrial process, heating facilities and incinerators

CO concentrations are much higher in urban areas due to the petrol powered vehicles

Peak levels coincide with the morning and evening rush hours

ii. Sulphur dioxide:

• Primarily produced by industrial processes (smelting of sulphur- containing ores) and combustion of sulphur containing fossil

fuels

• Chemically transformed in the atmosphere in the presence of other chemicals and sunlight to form acidic pollutants such as sulphuric acid and sulphates

• High levels of exposure to SO₂ - can worsen bronchial asthma and COPD, cardiac diseases

• Safe limit---80 µg/m³

iii. Lead:

• Produced by combustion of alkyl lead additives in motor fuels

• 80-90% of lead in air---due to combustion of leaded petrol

• Children <6 years are at increased risk

iv. Carbon dioxide:

Generated through combustion of coal, oil and gas;

Normally not an air pollutant

Rising above natural level---lead to global warming

v. Hydrocarbons:

Sources include incineration, combustion of coal, wood, processing and use of petrol

Causes photochemical smog

vi. Cadmiuim:

Sources include steel industry, waste incineration, volcanic action and zinc production

Constituent of tobacco---cigarette has 0.5 to 3 µg/g of tobacco

vii. Hydrogen sulphide:

Formed during coke production, in viscose rayon production, waste water treatment plants, wood pulp production, sulphur extraction process, oil refining and tanning industry

Main toxic substance involved in livestock rearing systems

Unpleasant odour, conjunctival irritation, neurological symptoms

viii. Ozone:

Primary component of smog

Differs markedly from the “ozone layer” which shields the earth’s surface from the suns’ intense ultraviolet radiation

Highly reactive - Can injure biological tissues and cells Significantly impair exercise tolerance in healthy adults

ix. Polynuclear aromatic hydrocarbons (PAH):

Large group of organic compounds with two/more benzene rings Formed as a result of pyrolytic processes especially the incomplete combustion of organic materials as well as in carbonization

500 PAH in air; best known is Benzopyrene (Bap) Automobiles, industry, burning wood, charcoal

x. Particulate matter:

Airborne particles are known as “particulate matter” (PM) or simply particles

Complex mixture of inorganic and organic substances The size of particles may range from 0.005µm to 100 µm Particles smaller than 2.5 µm are most dangerous

xi. Oxides of Nitrogen:

Combustion of coal, automobiles, electricity generation

Most common is nitric oxide but most important is nitrogen dioxide

Exacerbation of bronchitis in asthmatic children, reduced lung function growth

WHO guideline: < 40µg/m

(annual mean)

INDOOR AIR POLLUTION

One of the critical global environmental problems

Probably exposes more people worldwide to important air pollutants than does pollution in outdoor air

Rural people in developing countries, women and young children suffer the greatest exposure

Improving indoor air quality in developing countries would avert acute and chronic respiratory diseases by 15% and that of respiratory tract cancer by 10%

Sources: Tobacco smoke, stove, aerosol sprays, gas

heaters, gas cookers, cigarettes, solvents, adhesives, resins

AIR POLLUTION – HEALTH EFFECTS

Immediate effects -

• Principally borne by the respiratory system.

• Intense air pollution can cause immediate death by suffocation E.g. 1952 air pollution epidemic in London.

Delayed effects -

Mainly problems such as chronic bronchitis, lung cancer, bronchial asthma, emphysema, and respiratory allergies.

AIR POLLUTION– ENVIRONMENTAL EFFECTS

Smog:

•

Seen as a yellow brown haze that hangs over many cities in the early mornings or late evenings

•

A major component of smog is ground level ozone

•

Airborne particles such as fine particles or sulphates are also an important component of smog

•

Inhaling smog has adverse and varied consequences for

human health with cardio-respiratory system being the main

target of concern

Acid rain:

•Acid rain can affect lakes, forests, buildings, cars as well as human health

•The health concerns related to acid rain are primarily derived from the precursors- sulphur dioxide and nitrogen oxides

Green house effect:

Caused by the emission of green house gases into the atmosphere

Principal green house gases - Carbon dioxide, methane, chlorofluorocarbons, nitrous oxide, ozone

These gases - Absorb infrared radiation from the sun and trap this energy. The trapping of this heat is known as the greenhouse effect

Currently the large scale combustion of fossil fuels - one of the biggest contributing factor

Global warming of the atmosphere

Could alter the distribution of rainfall in many regions, making some wetter and others drier

Change vector borne disease distributions as well as change the distribution of vegetation

AIR POLLUTION–SOCIAL &

ECONOMIC EFFECTS

Destruction of plant and animal life Corrosion of metals

Damage to buildings

Cost of cleaning and maintenance and repairs and aesthetic nuisance

Reduces visibility in towns and cities which can

precipitate accidents.

AIR POLLUTION – MONITORING

The best indicators of air pollution:

A. Sulphur dioxide: Estimated in all air pollution surveys

B. Smoke or soiling index: Estimation of smoke conc.

in micrograms/cubic metre of air C. Grit and dust measurement:

D. Coefficient of haze: Assessing the amount of smoke or other aerosol in air

E. Air pollution index: Takes into account one or

more air pollutants as a measure of the severity of

air pollution

AIR POLLUTION MONITORING IN INDIA

The Central Pollution Control Board (CPCB) & State Pollution Control Boards (SPCBs) have set up

•

National Ambient Air Quality Monitoring (NAAQM)

network, comprising 290 stations in 92 cities/towns, under the Air (Prevention and Control of Pollution) Act, 1981 National Environmental Engineering Research Institute (NEERI) monitors ambient air quality in 30 stations

covering 10 major cities.

Major industries have also set up monitoring stations.

PREVENTION & CONTROL

Containment : Via enclosure, ventilation and air cleaning Replacement : Of technological process causing air

pollution

Dilution : Establishment of green belts between industrial areas and residential areas

Legislation: Air act 1981 (Prevention and control of pollution)

International action: Network of laboratories for the monitoring and study of air pollution

Disinfection of air : Mechanical ventilation, UV radiation,

chemical mists, dust control

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