Learning objectives
At the end of this lecture student will be able to : 1-Determine functions of air . 2-Identify sources of air impurity . 3-Discuss the self cleansing mechanisms of outdoor air . 4-Describe characteristics of occupied room air & factors affecting comfort feeling of individuals. 5-Specify meteorological factors affecting atmospheric pollution levels . 6-Determine air pollution (definition , sources effect , disinfection methods and preventive & control measures) . To a level accepted to the accreditation standard of the College .Air
*Air is the immediate environment of man ( all forms of life depend on it ). *Functions of Air are:- 1.Respiration Oxygen. 2.Cooling of human body by air contact. 3.Hearing & smell functions stimuli are transmitted through air. 4.Disease agents may be conveyed by air. 5.Air pollution (dust, smoke, toxic agents , chemical vapors) Sickness & Death.
*Human need a continuous supply of air to exist . ( requirement 10 -20 m3 /day). *Air is composed of a mixture of gasses (mechanical mixture) + water vapors ,amonia +suspended matter (dust + m.o.). Nitrogen 78.1% O2 20.93% CO2 0.03% + others. (traces). Sources of air impurity :- 1.Respiration of animals and man . 2.Combustion of fuel. 3.Decomposition of organic material. 4.(Dust ,fumes, vapors and gasses ) from trade , traffic and manufacture.
Self – cleansing mechanisms of out door air:- 1.Wind dilute and sweep away impurities. 2.Sun light oxidize impurities + kill bacteria. 3.Rain remove suspended matter. 4.Plant life utilize CO2 and generate O2. *Health hazard occur when the rate of pollution increase or cleansing process become ineffective.
Air of occupied room
*Human occupancy and activity vitiate air in occupied rooms and give a sense of discomfort. *Changes in air are:- Chemical from metabolic processes O2 CO2. 0.6 per hour Co2 per capita. Physical 1.Temerature : rise from body heat emanation. BTU British Thermal Unit 400 Btu/hour/head.Btu is quantity of heat required to raise the temp. of 1 pound of water 1 degree of Fahrenheit.2.Humidity moisture evaporated from skin and lungs . Expiration air 6% vapour.700 gm/day adult.3. Air movement.4.Arise of unpleasant body odors.(breath , perspiration , bad oral hygiene , dirty clothes … etc).Body odors depends on:Social status – Age – Personal hygiene.
5.Bacterial pollution Saprophytic Pathogenic (Conversation, cough, sneezing, loud talking).
*Unless vitiated air replaced by fresh air ,it may adversely affect the comfort, health and efficiency of occupants a feeling of suffocation or discomfort, headache , drowsiness and inability to concentrate . Prolonged exposure risk of droplet infection + resistance to disease.Discomfort:- subjective sensation which people experience in ill – ventilated and crowded rooms.
It is believed to be due to O2 and CO2. Now it is due to physical changes rather than chemical changes ( temp. , humidity, air movement , heat radiation) .These factors determine cooling power of air with respect to human body.
*The problems of ventilation are physical not chemical.Indices of thermal comfort:-1.Air temperature.2.Air temperature & humidity.3.Cooling power ( temp. , humidity , air movement).Kata thermometerdry Kata of ≥ 6 wet Kata of ≤ 20 Thermal comfort
4.Effective temperature . *It is an arbitrary index which combines into single value the effect of temp., humidity , and interval air movement on the sensation of warmth or cold felt by human body. *The numerical value is that temperature of still, saturated air which induce the same sensation of warmth or cold that experienced in a given condition. *It ignores the effects of a radiation from the surrounding structures.
5.Corrected effective temperature. CET scales deal with air temperature , velocity ,humidity ,and mean radiant heat.
Comfort Zones
The range of effective temperatures over which the majority of adults feel comfortable . *Comfort is quite a complex subjective experience which depends not only on physical, physiological factors , but also on psychological factors which are difficult to determine.Meteorological Factors
*Man is most directly concerned with only (8-10) km of atmosphere. *Level of atmospheric pollution depends up on :- 1.Topography. 2.Air movement. 3.Climate. *Winds dispersal and dilution of pollutants.*Vertical diffusion of pollutants depend on temp. Gradient. Rapid cooling of lower air little vertical motion pollutants + water vapors trapped at lower atmospheric levels smog. *Smog = fog + smoke. *Temperature inversion is a threat to human health. *Indoor air pollution is the most critical problem than outdoor pollution , it contributes to:-
1.Acute respiratory infections in children. 2.Chronic lung diseases and cancer in adult. 3.Adverse pregnancy outcomes in pregnant.
Pollution Air Water Soil
Air pollution
Air pollution is one of the present – day health problems worldwide.Air pollution is an inescapable consequence for the presence of man and his activities.Air pollution
The presence ,in the surrounding atmosphere ,of substances generated by human activities ,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, thereby constituting additional source of human exposure.Direct effect of air pollution on plants , animals and soil can influence self regulation ability, thereby affect quality of life. Sources of air pollution :- 1.Automobiles *Emit hydrocarbons, carbon monoxide , lead , nitrogen oxides , black smoke, malodorous fumes and particulate matter. *Under sunlight certain hydrocarbon and nitrogen oxides converted to photochemical oxidizing agents.
2.Industries Emit large amounts of smoke, sulfur-dioxide, nitrogen fluoride , HCL and organic halides , CO, CO2,ozone and hydrogen sulfide. 3.Domestic sources Combustion of fuel smoke ,dust, sulfur oxide and nitrogen oxides. 4.Tobacco smoke 5.Miscellaneous burning refuse , pesticides, natural sources (e.g. wind, dust, fungi, bacteria), nuclear energy programs.
1.Destruction of plants & Animals. 2.Corrosion of metals. 3.Building damage. 4.Cleaning & maintenance cost. Town visibility. Soil & clothing damage.
Effects of Air Pollution Health Aspects Social & Economic Aspects
Immediate
Delayed(Bronchitis ,suffocation ,death)
(Chronic bronchitis ,lung cancer ,asthma ,Emphysema, respiratory allergies). Lead poisons impaired neuro-psychological development of children school performance + Behavioral difficulties.
It is difficult to estimate precisely the risk of air pollution because of :- 1.Difficult estimation of individuals exposure degree. 2.Multiple confounding variables (smoking, nutrition , occupation , climate ). *Sudden air pollution immediate morbidity and mortality.
Prevention & Control of Air Pollution
The WHO has recommended the following procedures:-1.Containment i.e. prevention of escape of toxic substances into the ambient air.*It can be achieved by a variety of engineering methods such as enclosure, ventilation and air cleaning.*A major contribution is the development of “arresters” for the removal of contaminants .2.Replacement i.e. replacing a technological process causing air pollution by a new process that does not. *Increased use of electricity ,natural gas and central heating in place of coal have greatly helped in smoke reduction. *There is a move now to reduce lead in petrol which is accumulative poison (de-leaded petrol).
3.Dilution It is valid so long as it is within the self – cleaning capacity of the environment.*Some of air pollutants are readily removed by vegetation. The establishment of “green belts“ between industrial and residential areas is an attempt at dilution .*The capacity of dilution is however limited.
Trouble occurs when the atmosphere is over burdened with pollutants. 4.Legislation Air pollution is controlled in many countries by suitable legislation e.g. clean Air Acts. Legislation covers such matters as height of chimneys , powers to local authorities to carry out investigations , research and education concerning air pollution , creation of smokeless zones and enforcement of standard for ambient air quality .
5.International Action WHO has established an international network of laboratories for the monitoring and study of air pollution. * The network consist of two international centers at London & Washington ,three centers at Moscow, Nagour and Tokyo and 20 laboratories in various parts of the world. *These centers will issue warnings of air pollution where and when necessary.
Disinfection of Air : Disinfection methods employed are:- 1.Mechanical Ventilation : It reduces vitiated air and bacterial density. 2.Ultraviolet radiation: It is effective in special situations such as operation theatres and infectious disease wards. *Since direct exposure to ultraviolet rays is a danger to the eyes and skin, ultraviolet lamps are shaded and located in the upper portion of the rooms near the inlet of air. *Ultraviolet rays have proved effective for general use in public assembly and school rooms.
3.Chemical Mists Tri-ethylene glycol found effective bactericide against droplet nuclei and dust. 4.Dust control Application of oil to floors of hospital wards reduces bacterial content of the air . Air disinfection is still in the experimental stage.