In the atmosphere, some gases like CO2 allow sunlight to reach the
ground but do not allow the heat to escape out of the atmosphere back into
the outer space. This results in increase in temperature of the earth. This
is called the green house effect.
Air Pollutants and their Sources
Oxides of carbon
(CO2 and CO)
Homes, industries, automobiles
Oxides of sulphur
(SO2 and SO3)
Oxides of nitrogen
(NO and NO2)
Aerosol spray, refrigerators, air conditioners
Construction activities, Industries
Water Pollutants and their Sources
Sewage from hospitals, homes, etc.
Insecticides and pesticides
Polychlorinated biphenyls (PCB),
Laboratories, hospitals, atomic reactors
Biological Oxygen Demand (BOD)
BOD is measured by placing a sample of water containing known amount of
oxygen for five days at 20°C in the dusk. After five days, oxygen content of
the sample is measured. A high BOD indicates high level of microbial
The range of normal human
hearing is between 50Hz to 15,000 Hz frequencies.
Frequencies below 50Hz are
called infrasound and above 15,000 Hz are ultrasound.
Prolonged exposure to noise
level of 80 dB or more gradually leads to permanent loss of hearing
Effect of Acid Rain on Human Life
1.Sulphur dioxide and nitrous
oxide from industries and automobile exhauts
combine with rain water in the air to form acidic water called acid rains.
2.Effects of acid rain on human life;
3.Acid rain changes the level of hydrogen ion concenteration
of soil water, and thereby affects the life of plants and aquatic organisms.
4.Acid rain affects agricultural crops and forests.
5.Acid rain affects the buildings, leading to their gradual
6.Acid rain causes decolourising effects
in plants, which in turn reduces their rate of photosynthesis.
8.This is followed by disruption of food chain on which man
depends for his liveliblood.
Effect of Water Pollution of Human Life
1.Water polluted with domestic sewage causes a number of epidemic
diseases like cholera, dysentery, typhoid, jaundice, etc.
2.Depletion of oxygen supply in water due to industrial wastes
kills fishes and other aquatic organisms.
3.The toxic substances present in industrial wastes kill
microorganisms and other aquatic organisms, which are responsible for biopurification of water.
4.The waste from factories endangers the lives of fish, cattle and
even human beings through the food chain.
5.Thermal pollution resulting from the industrial wastes leads to
cause harmful effects on the fishes and other aquatic animals,
and in turn on human too.
6.Eutrophication resulting from the
water pollution reduces the oxygen content in water, rendering it unfit for
fishes and other animals.
Natural and artificially emitted hydrocarbons, in the presence of oxides of
nitrogen, undergo photochemical reactions, which produce a cloud of toxic
chemicals, including ozone and a variety of caustic agents. This process is
powered by sunlight and some of the products, such as ozone, reach a peak
soon after photon flux from the sun reaches a maximum around . The thermal inversions often associated
with some cities can lead to a dangerous buildup of smog in urban areas.
Human deaths have been attributed to photochemical smog since the industrial
revolution in cities such as London and New York.
Para-dichlorodiphenyltrichloroethane was commonly used during the Second
World War. It was used to kill mosquitoes that carried malaria and yellow
fever. It was also used to kill body lice that can transmit typhus. Many
problems have been associated with the use of DDT. Some of these problems are
its bioaccumulation in the food chain, decline of smaller animals, and
softening of birds eggs. In 1973, the EPA banned all
use of DPT, except those essential to public health. DDT is still used in
It is naturally occurring fibrous mineral found in certain types of rock
formations. The primary use of asbestos was as a fireproofing material,
applied to structural steel members in multistory commercial buildings to
attain proper fire protection. With its resistance to heat, asbestos was able
to keep the building structure from bending and warping, if exposed to fire.
After widespread use of asbestos over a 15 to 25 years time span, a pattern
of illness gradually surfaced inin asbestos
workers. Three diseases linked to asbestos exposure are asbestosis, a fibrous
scarring of the lungs, lung cancer, and mesothelioma,
a cancer of the lining of the chest or abdominal cavity.
Ozone O3, is a molecule that consists of three
oxygen atoms bonded together. The ozone layer in the stratosphere absorbs UV
radiation and creates a warm layer of air in the stratosphere, and is,
therefore, responsible for the thermal structure of the stratosphere. Ozone
that is present in the troposphere is mostly a result of anthropogenic
pollution, and therefore, higher concentrations are found in urban areas.
PAN (Peroxyacetyl nitrate)
A class of chemical substances found as a pollutant in the troposphere,
formed by photolysis of natural and manufactured organic chemicals. These
chemicals act as irritants and mutagens in mammals and are toxic to many
The negative logarithm of the hydrogen ion concentration of a solution. It is
the quantitative expression of the acidity and alkalinity of a solution and
has a scale that ranges from about 0 to 14. pH
7 is neutral; <7 is acidic; <7 is alkaline.