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83Preventive Healthcare
iii. Dilution: The method has limited application, particularly
when excessive pollution takes place. Vegetation removes
air pollutants. Developing green belts between industrial
and residential areas is also effective in diluting air
pollution.
iv. Legislation: Enactment and strict enforcement of Air
Control Legislation is the need of the day. The Smoke
Nuisance Act is effective in Kolkata, Mumbai,
Ahmedabad, and Kanpur.
v. International action: WHO has established an inter-
national network of laboratories for the monitoring centers
in London, and Washington; 3 regional centers at Moscow,
Nagpur, and Tokyo; and 20 laboratories in various parts of
the world. These centers would issue warnings of air
pollution whenever necessary.
Noise Pollution
Noise has become a very important ‘stress factor’ in our
environment. It is an unwanted sound that is unpleasant to
the ears. Noise pollution is increasing due to industrialization,
heavy machines, technology, transport vehicles, ceremonies,
festivals, religious and political activities, etc. The unit of
measurement of sound and noise is the decibel (dB). A decibel
is the smallest difference in sound normally audible to the ears.
At 100–120 db noise is uncomfortable and at 130–140 db it is
painful to the ears. The general noise level should not exceed
85 dB. Continued loud noises above 80–90 dB may lead to loss
of hearing. An audiometer is used to measure hearing ability.
Ill-effects of noise pollution
1. General inefficiency results in lower output.
2. Cardiovascular diseases and blood pressure problems.
3. Irritability, nervous tension, and neurosis.
4. Physical and mental fatigue with loss of concentration.
5. Developmental anomalies in the fetus, etc.
6. Sleep cycle disturbances.
7. Noise induced hearing loss (NIHL).
84 Social Pharmacy
Prevention and Control
The following measures can minimize noise pollution:
1. Use of silencing devices at source.
2. Use of sound-absorbing material in machinery.
3. Use of ear plugs or ear muffs by the workers in factories
with more than 100 dB noise.
4. Banning of musical horns and increasing the no horn, or
‘silence zones’ for vehicles.
5. The use of loudspeakers is the most common noise
measure that should be restricted.
6. Roadside houses should have soundproof walls.
7. Heavy vehicular traffic in residential areas should not be
permitted.
8. Development of residential areas around loud noise
factories should be discouraged.
9. Plantation of trees can help reduce noise by 8–10 db.
10. Educating the general public about the importance of noise
as a community hazard.
11. Legislative control.
Sewage and Solid Waste Disposal
The main purpose of disposal of sewage is to convert different
unstable organic matters present in sewage into harmless stable
chemical compounds. Sewage generally contains 99.9% water
plus organic and inorganic impurities. But it is the organic
matter, which imparts offensive nature to the sewage. Either
aerobic or anaerobic processes bring about the decomposition
of organic matter. In the aerobic process, the organic matter is
broken down into simpler compounds like carbon dioxide,
water, ammonia, nitrites, nitrates, and sulfates by the action of
bacteria, fungi, and protozoa. The end products of the anaerobic
process are methane, ammonia, carbon dioxide, and hydrogen.
The disposal of sewage into the watercourse may be carried
out by:
i. dilution (without prior treatment), or
ii. purification (after prior treatment).
85Preventive Healthcare
A. By Dilution
The method consists of diluting sewerage by discharging it into
sea or river water. It can be applied in places near the sea or
the riverside. It must be ensured that the dilution is sufficient.
Disposal of sewage into rivers makes the water polluted and
unsafe for potable purposes.
The best method of sewage disposal is therefore disposal
after purification. The objective is to collect, treat, and dispose
of sewage in such a manner that will protect health, preserve
our natural resources, and prevent nuisance factors and water-
borne diseases.
B. By Purification
Purification is done through either preliminary or secondary
treatment.
i. Preliminary treatment: It removes solids by passing
through screens and grit chambers. Bar screens remove
gross solids like stones, bricks, dead animals, etc. The
screen consists of iron bars 2.5 to 4 cm apart and set at 33
to 60º angles in the direction of sewage flow. Comminutor
may be used in place of screens. Comminutor is a
mechanical grinder, which crushes larger solids to smaller
sizes that can pass through 1 cm apart screens. The grit
chamber consists of a long, narrow, and deep channel. In
this chamber sewage flows at the rate of one foot per
second, the grit settles and sewage passes out. Grit consists
of heavy inorganic material like sand, gravel, glass, etc.,
which, if not removed, causes wear and tear to the plant.
Grit is disposed of by landfilling.
ii. Primary treatment: This is carried out in primary settling
tanks, usually rectangular in design. The sewage passes
through the tank at a slow speed, 1 to 2 feet per minute,
and remains in the tank for 6 to 8 hours. This allows solids
to settle to form sludge at the bottom followed by removal
by sludge collectors. The scum rises at the top and is
removed into a scum-removing trough near the outlet.
iii. Pretreatment removes about 50% of solids and suspended
matter and reduces the coliform bacteria by 30 to 40%. The
86 Social Pharmacy
biological oxygen demand (BOD) of sewage is reduced by
about one-third. BOD is the amount of oxygen needed to
oxidize organic matter in the sewage.
iv. Secondary treatment: This is carried out either by trickling
filter unit or activated sludge unit. Biological action takes
place and organic matter in the sewage is converted into
inorganic nitrates by aerobic bacteria. This reduces the
BOD of sewage by about 90%.
a. Trickling filter unit: After primary treatment, the
sewage effluent is led to trickling filters, which consist
of a bed of crushed stones or clinker, 6 to 100 feet in
diameter and 5 to 6 feet deep. During the passage
through filters, the bacterial flora oxidizes the effluent.
The sewage is then taken to secondary settling tanks
for the settlement of sludge. The resulting effluent is
treated with chlorine and discharged into a river or a
stream.
b. Activated sludge unit: The activated sludge process is
also known as the aeration process. It is the aerobic
process of disposal of sewage and is considered to be
the most satisfactory method of sewage purification. It
is a multi-chamber reactor unit that uses highly
concentrated microorganisms to degrade organics and
remove nutrients from wastewater, producing quality
effluent. The goal is to maintain aerobic conditions and
to keep the activated sludge suspended. The sewage
effluent is mixed (Fig. 2.10) with 15 to 25% of activated
sludge from the secondary settling tanks, mixed with
compressed air, and left in aeration tank for 4 to
8 hours for the biological action. The organic matter in
the sewage is thus converted into a stable inorganic
form. The typhoid and cholera organisms are
destroyed and coliforms are greatly reduced. The
sewage effluent after preliminary treatment and
primary treatment is carried to the mixing chambers of
aeration chambers in which the whole of the sewage is
converted into fine emulsion with the help of
compressed air. The scum is removed from the top and
87Preventive Healthcare
sewage led to mixing chambers. In the mixing cham-
ber, the sewage is mixed with 15 to 25% of activated
sludge obtained from secondary settling tanks.
The mixed sewage is then sent to aeration tanks where it is
agitated by compressed air through diffusers. The aeration
period is 4 to 8 hours. The organic matter breaks up and
ammonia is oxidized to nitrates. Sewage from aeration tanks
flows to secondary settling tanks where coagulated material
settles and forms activated sludge. A portion of this activated
sludge is again used for mixing with sewage in mixing
chambers and the remaining portion is taken for the process of
digestion. The effluent from secondary settling tanks may be
chlorinated to destroy pathogenic organisms and finally
discharged to a water course.
Sludge digestion is the process of sludge fermentation under
anaerobic conditions. This digestion produces (i) inoffensive
sludge, much reduced in amount and easily handled, and
(ii) burnable gas.
A modern sewage treatment plant is shown in Fig 2.11.
SOLID WASTE DISPOSAL AND CONTROL
Waste is the solid and liquid matter from households and
environments, and includes commercial and industrial wastes.
Fig. 2.10: Activated sludge unit
88 Social Pharmacy
Solid waste is also called refuse in cities and litter in villages.
It consists of garbage, ashes and all rubbish discarded from
houses and environments except human excreta.
Liquid waste is from humans and animals, laundry, kitchen,
street, commercial and industrial wastes.
Waste becomes a source of spread of pathogens and diseases
like enteric fever, cholera, bacillary dysentery and amoebic
dysentery, infectious hepatitis, helminthic infections, etc., are
transmitted through human waste. Waste disposal is therefore
important from a public health viewpoint. The objective is to
protect health, preserve our natural resources, maintain a
healthy environment, and prevent nuisance conditions.
(a) Sources of refuse
i. Household refuse includes food waste, dust, ashes, rugs,
papers, animal droppings, etc. Affluent societies in general
produce more and more bulk refuse.
ii. Street refuse includes dust, dung, paper, bird droppings,
animal and vegetable wastes, and other droppings.
iii. Industrial refuse consists of a wide variety of wastes ranging
from inert material like calcium carbonate to highly toxic
and explosive compounds.
Fig. 2.11: Modern sewage treatment
89Preventive Healthcare
iv. Stable refuse is collected from stables and contains waste
straw, dust, dung, etc.
v. Domestic refuse consists of ash, rubbish, and garbage.
Rubbish comprises paper, clothing bits of wood, metal,
glass, dust, and dirt.
vi. Garbage is the waste matter resulting from the preparation,
cooking, and consumption of foods and consists of waste
food, vegetable peelings, and other organic matter.
Garbage ferments on storage hence it must be quickly
disposed of.
(b) Collection and removal of refuse
Sanitary bins should be used for the collection of household
refuse to avoid putrefaction and fly breeding. Street refuse is
collected by conservancy staff. It should be kept in specially
provided public bins. The refuse so collected should be
transported to places of disposal in covered carts or motor vans,
etc.
(c) Disposal of refuse
The following methods are commonly used for disposal of
refuse:
i. Controlled tipping and dumping: Controlled tipping is an
easy and cheap method. The refuse is generally utilized in
filling up clay pits and hollows, in sanitary tanks, or in
reclaiming low-lying lands. Indiscriminate dumping
causes nuisance from fire, flies, rats, and offensive gases.
Dumping sites should be 30–50 meters away from
habitation. Refuse material should be deposited in layers
of about 6' and covered with about 9'’ thick layer of earth.
According to WHO, dumping is a most unsanitary method
that creates public health hazards and leads to pollution of
the environment.
ii. Burning or incineration: It is one of the best methods of
refuse disposal. Burning makes the refuse harmless and
reduces it to 1/4th of its original weight. The mass left
behind is hard clinker, which is used in making roads. The
incineration is carried out in a furnace constructed of
bricks with firebrick lining.
90 Social Pharmacy
iii. Composting: This method is useful in towns where refuse
has to be disposed of with night soil and converted into
compost, which has high manure value. Composting is a
process of changing organic matter into manure with the
help of bacterial action. Excreta, refuse and moisture are
mixed in a suitable proportion to give a carbon: nitrogen
ratio of 30:1. Two-week-old inoculum of bacteria is also
added. The mixture is laid in dug-out trenches (3 deep and
6–8 wide with adjustable length till the layer is 6 to 9
above ground level). Then it is covered with earth.
Composting is completed in 4 to 6 months.
iv. Mechanical composting: This is a popular method of
composting, which is currently practiced in Holland,
Germany, Switzerland, and Israel. Ten mechanical
compost plants were set up in India during 1975–80 under
the Central Scheme of Solid Waste Disposal. The process
consists of first removing salvable materials such as rags,
bones, metal, glass, etc. from refuse. It is then pulverized
to reduce the size of the particles to less than 2'’. The
pulverized refuse is mixed with night soil, sewage, or
sludge in a rotating machine and incubated. The compost
gets ready in 4 to 6 weeks.
v. Pitting: This method is particularly useful in rural areas.
The refuse is dumped into manure pits and covered with
earth. The refuse is converted into valuable manure in
about 6 months.
vi. Burial: In this method, refuse is buried into an excavated
trench of 1.5 meters in width and 2 meters in depth and
covered with 20 to 30 cm of earth at the end of each day.
When the level of dumped material in the trench comes to
40 cm above the ground level, the trench is filled with earth
and composted, and a new trench is excavated.
vii. Disposal in the sea: Refuse at airports can be dumped in
the deep sea, at least 8 to 10 km away from the seashore.
This is an expensive method.
Public education about the importance of refuse disposal
would go a long way in solving the problem. The International
Solid Wastes and Public Cleansing Association assists various
91Preventive Healthcare
countries in the general endeavor to improve sanitary services.
Information about waste disposal can also be obtained from
the WHO International Reference Center in Switzerland.
Occupational Illnesses
An occupational illness is any illness whose cause is associated
with the workplace environment or conditions. These illnesses
can be caused by poor air quality, exposure to chemicals, lack
of sanitation, and several other hazards. Some of the most
commonly contracted occupational illnesses include:
1. Diseases due to physical agents
Common physical agents and the diseases caused by them are
shown in Table 2.6.
Table 2.6: Physical agents and diseases caused by them
Agent Disease
Heat Heat hyperpyrexia, heat exhaustion, heat syncope,
heat cramps, burns and local effects such as prickly
heat.
Cold Trench foot, frostbite, chilblains
Light Occupational cataract, miner’s nystagmus (meaning
dancing eyes)
Pressure Caisson disease, air embolism, blast (explosion)
Noise Occupational deafness
Radiation Cancer, leukemia, aplastic anemia, pancytopenia
Mechanical Injuries, accidents factors
Electricity Burns
2. Diseases due to chemical agents
Common chemical agents and the diseases caused by them are
shown in Table 2.7.
3. Diseases due to biological agents
Work-related exposure to biological agents (viruses, bacteria,
fungi, and parasites) may cause several health problems,
including infectious diseases, cancer, and allergies, e.g.
actinomycosis, tetanus, encephalitis, and fungal infection.
92 Social Pharmacy
4. Occupational cancers
Cancer that is caused wholly or partly by exposure to a
carcinogen at work, e.g., cancer of the skin, lungs, bladder, and
leukemia. Occupational ultraviolet radiation, asbestos, diesel
engine exhaust, pesticides and herbicides, ionizing radiation,
benzene, and second-hand tobacco smoke are some examples
of occupational carcinogens.
5. Occupational dermatosis
Any alteration in the skin or mucosa that is directly or indirectly
caused by agents present in the work environment is called
occupational dermatosis, e.g. dermatitis, eczema. Agents, that
can cause occupational dermatosis include cleaning products,
organic solvents, metalworking fluids, cement, adhesives, and
even certain plants.
6. Diseases of psychological origin
Industrial neurosis, hypertension, peptic ulcer.
Environmental Pollution due to Pharmaceuticals
Active pharmaceutical ingredients (APIs) are the biologically
active ingredients in a pharmaceutical drug. Pharmaceuticals
are biologically active substances that are used for their
pharmacological effects in living organisms. But they also have
an impact on wildlife and the ecosystem, if not treated in an
Table 2.7: Chemical agents and diseases caused by
them
Agent Disease
Gases (CO
2,
CO, HCN) Gas poisoning
Dust Pneumoconiosis
Silica Silicosis
Asbestos Asbestosis, cancer lung
Canefibre Bagassosis
Cotton dust Byssinosis
Tobacco Tobacossis
Coal dust Anthracosis
Iron Siderosis