ENVIRONMENT AND HEALTH/ part-1

 WATER:

An important cause of the ill health in underdeveloped countries is the lack of safe drinking water.

It should be free from pathogenic agents and harmful chemical substances ,pleasant taste and usable for domestic purpose.

An average daily supply of 150-200 liters per head is considered the optimum quantity.

Sources of water supply:

The two important consideration for selecting a proper source are:

(a) Quality of water must be acceptable

(b) Quantity must be enough to meet the present requirements

Three main sources  of  water are

1. Rain water

2. Surface water

3.Ground water

Rain water: Rain water that sinks into the ground forms ground water, and that runs off to form streams,rivers and tanks.

Surface water: The surface water sources include

  (a) Impounding Reservoirs:

      These are artificial lakes constructed usually of masonry in which large quantities of surface water is stored.

     (b) Rivers: Many rivers provide a dependable source of water. The main drawback of river water is that it is grossly polluted due to dissolved and suspended impurities of all kinds.

 (c) Tanks: These are large excavations which store surface water and form important source of drinking water in village. It is quite dangerous as a source of drinking water and is responsible for spreading of number of disease.

Ground Water: It is the cheapest and comparatively safer means of providing water to communities in villages and small towns.

It is likely to be free from pathogenic contaminants and generally it does not require treatment with disinfectants.

                                              WATER POLLUTION

                                  

Water may contain impurities of different kinds, these are

 1. Dissolved impurities: These include dissolved gases like hydrogen sulphide, ammonia,carbon dioxide and nitrogen and some dissolved minerals like salts of sodium, calcium and magnesium.

2. Suspended impurities: These include fine clay shit,sand and mud and microscopic plants and animals.

3. Water pollution caused by human activities: 

                       (a) Sewage: as it contains decomposable organic matter and pathogenic agents.

                       (b) Industrial and trade waste: which contain toxic substances ranging from metal salts to                                complex synthetic organic chemicals.

                       (c) Agricultural pollutants : Which consists of pesticides and fertilizers .

                        (d) Physical pollutants like heat and radioactive substances.

HAZARDS OF WATER POLLUTION:

Hazards of water pollution can be discussed under two broad groups .

(a) Biological hazards: These consists of water born diseases caused by the presence of an infective agent or an aquatic host in water.

examples: hepatitis,poliomyelitis,cholera,typhoid,bacillary dysentery,amoebiasis

(b) Chemical hazards: These are caused by chemical pollutants derived from industrial or agricultural wastes.

examples: cyanide,heavy metals,organic acids, sulphide,ammonia

                                           PURIFICATION OF WATER

Purification of water plays an important role in community medicine as polluted or contaminated water is responsible  for the spread of a number of infectious disease.

1. Large scale purification of water:

   (a) Storage: Storage of water obtained from proper source excludes further pollution and causes automatic purification during an optimum period. Quality of water improves on storage as suspended impurities settle down and water becomes clearer.

   (b) Filtration: Filtration removes 98-99% of bacteria apart from other impurities.

        Two types of filters are used one is 'slow sand' filter or Biological filter and other is 'rapid sand'               filter or mechanical filter.

 (c) Chlorination: Chlorination is one of the most effective methods of water purification.

       When chlorine is added to water , it leads to formation of hydrochoric and hypochlorous acids.

     The hypocholorous acid is mainly responsible for the disinfectant action of chlorine .

     Chlorine produces it's maximum disinfectant action when the PH of water is around 7.

    The disinfection action of chlorine is based on the following principles:

    1. It is important that the water to be chlorinated should be clear and free from turbidity.

    2. The chlorine demand of water should be estimated prior to large scale chlorination. Chlorine demand  has been defined as the difference between the amount of chlorine added to water and the amount of residual chlorine remaining at the end of specific period of contact.

2. Small scale purification of water:

 (a) For household purification of water ,three methods are most commonly used .

 They are boiling of water-Boiling the water for 5-10 minutes,it will kill bacteria, spores,cysts and ova.

chemical purification - We can remove the temporary hardness of water by adding carbon dioxide and precipitating calcium carbonate.

 filtration- Filtering the water through ceramic filter such as Pasteur Chamberland filter, Berkefield filter and Kayandyn filter.

(b)  Disinfection of wells: Wells are the most common sources of water supply in villages and small towns. The most effective and economical method of disinfecting wells is by bleaching powder.

HEALTH AND AIR:

All forms of life depend on air, in addition to the supply of life-giving oxygen,air and atmoshperic conditions and many other functions. special senses of hearing and smelling function through air transmitted stimuli.

Pollution of air, dust,smoke,toxic gases and chemical vaporous can result in sickness and death.

Air pollution sources are generally classified into four broad categories.

(a) Industrial outlets: Chemical industries,textile industries,metallurgical industries etc contribute to air pollution.

(b)Combustion: Industrial and domestic combustion of coal,oil and other fuel is the source of smoke,dust and sulphur dioxide.

(c) Motors Vehicles: Both heavy and light motor vehicles,trucks,air crafts and trains and other forms of transport contribute to air pollution  by emitting hydrocarbons,carbon monoxide,lead etc.

(d)Miscellaneous: Agricultural activities like crop spraying and pest control,burning of refuse and nuclear energy programmes also contribute to air pollution.

Effect of air pollution on health:

(a) Immediate effects: According to epidemiological studies a sudden increase in air pollution has often been associated with immediate increase in mortality and morbidity. The Bhopal gas tragedy and the Chernobyl disaster of U.S.S.R are the most recent examples.

(b) Delayed effect: The diseases which are generally attributed to air pollution are chronic bronchitis and primary lung cancer.

LIGHT:

Adequate lighting is essential for an efficient vision.For an efficient vision the following criteria of light is usually applied.

(a) Sufficient light: The lighting should be sufficient for the eye to easily discern the object and surrounding with out any strain . An illumination of 15-20 foot candles is accepted as basic minimum for satisfactory vision.

(b) Distribution: The light should be uniformly distributed having the same intensity over the whole field of work.

(c) Absence of Glare: Glare is harsh dazzling light. It is best examplified by automobile head lights at night due to excessive contrast.

(d)Absence of sharp shadows: Shadows should not be present in the field of vision as they cause confusion to the eye.

(e) Steadiness: Light should be projected constantly without any interruption flickering of light causes strain to the eye and may lead to accidents.

(f) Surroundings: For efficient vision , the colors schemes in the rooms and halls is important.

ceilings and roofs should ideally have a reflection factor of 80% ,walls 50 to 60 % and furniture 30to 40%, reflection from floor should be minimum not more than 15-20%.

NOISE:

Sourses:

There are a number of sources of noise which can produce environmental pollution.These includes factories,automobiles,industries,air crafts and domestc appliances like radios,transistors,televisions and stereo systems of high wattage and also the public address systems and loudspeakers etc.

Properties:

Noise has two important properties,loudness and frequency. Loudness or intensity signifies the amplitude of vibrations which initiate the noise.Intensity of sound is measured in terms of decibels(dB)

One decibel is defined as the smallest distingushable noise or the reference sound pressure equal to 0.0002 microbar or dynes/cm2. 

Normal conversation ranges in between 60-65 dB. above 120dB it becomes noise.Most of the people can tolrate noise level uoto 85 dB.

Frequency:Frequency is measured in Hertz(Hz)

One Hz is equal to one wave per second

The human ear can hear frequencies from 20 to 20,000 Hz

Effect of noise:

Auditory effect: Side effects such as whistling and buzzing in the ear generally appears in the 90dB and is maximum at 4000Hz.

Nonauditarory effect:Frequencies causing maximuminterferance with speech lie in the range of 300-500 Hz.

Noise control:

(a)Control of noise at sources

(b)control of transmission of noise

(c)Protection of exposed person

(d)Education