Air and Water Pollution
- Pollution is an undesirable change in physical, chemical or biological
characteristics of our air, land or water caused by excessive accumulation
- These changes may affect man directly or indirectly through his supplier
of water and of agricultural and other biological products.
- The air pollution is caused due to dust particles, industrial emission,
automobile exhaust, smoke, dispersion of pesticides and radioactive
- Two major factors responsible for air pollution are population explosion
and productivity increase.
- Air pollutants can be categorised into primary pollutants and secondary
- Primary Air Pollutants and their Effects
Particulate matter comprises of solid and liquid aerosol
suspended in the atmosphere. The particulate matter causes corrosion and erosion
of surfaces and in human beings, it may cause respiratory problems.
Carbon monoxide (CO) is produced mainly by incomplete
combustion of fossil fuels. It is a very poisonous gas. It reduces oxygen
carrying capacity of blood and may also lead to death due to anoxia (oxygen
Hydrocarbons (HCs) or Volatile Organic Carbons
(VOCs) are compounds composed of Biodiversity hydrogen and carbon. They
may be saturated (methane) or unsaturated (ethylene). They cause irritation on
mucous membrane and some may be carcinogenic e.g., formaldehyde.
Sulphur dioxide (SO2) is produced by combustion
of coal and petroleum. In human beings, it causes respiratory problems. It also
produces acid rain.
Nitrogen oxides (NO, N2O) are produced when
nitrogen and oxygen combine together at high temperature in any combustion
process. These gases cause the reddish-brown haze (brown-air) which is
responsible for respiratory diseases in human beings. They also cause acid rain
due to formation of HNO3.
Secondary Air Pollutants and their Effects
Photochemical smog contains pollutants like ozone, oxides of
nitrogen, and peroxylacetyl nitrate (PAN). It is often called brown air
solar radiation is intense. The areas where solar radiation is less, smog
formation is incomplete and the air is called grey air.
- Ozone and PAN are commonly referred as oxidants. Ozone breathing affects
the respiratory and nervous system in human. PAN damages chloroplast in
plant and inhibits electron transport system.
Acid rain includes wet and dry deposition on the earth.
Wet deposition refers to acidic water received through rain,
fog and snow. Dry deposition refers to the wind blown acidic
gases and particles which settle down on the earth. Acid rain damages marble,
metal and stonework.
Control of air pollution
- There are two devices to remove particulate air pollutants, viz.
arresters and scrubbers.
- Electrostatic precipitator (ESP) is most effective
method to remove particulate pollutants.
- Gaseous pollutants are controlled by combustion, absorption and
- Automobile exhaust can be controlled by catalytic converter filters and
by using good quality fuels.
Water pollution may be of following types:
(i) Physical pollution is caused by hot water from
industries, oil spills from oil carriers etc.
(ii) Chemical pollution is caused by organic chemicals e.g.,
biocides, PCBs and inorganic chemicals e.g., phosphates, nitrates, fluoride and
(iii) Biological pollution is caused by pathogens such as
viruses, bacteria, algae, protozoa and helminths.
- Municipal wastewater carries organic wastes which are
biodegradable, and this water is directly discharged into rivers.
- Industrial wastewater is contaminated by a variety of
organic and inorganic pollutants. All the rivers of India are heavily
polluted by the discharge of industrial wastewater.
- Surface runoff from land is contaminated with
pesticide residues and residues of inorganic fertilisers.
- Oil spills from oil carriers and oil refineries mainly
cause oil pollution to marine ecosystem. Effects of Water Pollution
- Organic and inorganic wastes decrease the dissolved O2content of water
bodies and affect aquatic ecosystem.
- The demand for oxygen is directly related to increasing input of organic
wastes and is expressed as biochemical oxygen demand (BOD)
- Chemical oxygen demand (COD) is the measure of
pollution load in water.
- Biological magnification is the phenomenon through
which certain pollutants e.g., DDT, PCB get deposited in tissues in
increasing concentrations along the food chain.
- Eutrophication is the process of nutrient enrichment of
water and consequent loss of species diversity.
- Contaminated water can any germs of water-borne diseases like jaundice,
cholera, typhoid, etc. and thus, may affect human health.
- Mercury poisoning (Minamata disease) was caused due to
consumption of fish captured from Minamata Bay in Japan.
- Cadmium pollution can cause itai-itai disease and
cancer of liver and lung. Ground water Pollution
- Excess nitrate in groundwater drinking water, reacts with haemoglobin
and forms non functional methemoglobin which impairs oxygen transport. This
is called methaemogiobinemia or Mtte-baby syndrome.
- Excessive exposure to arsenic causes black-foot disease.
For improving Water Quality
- Industrial and municipal waste water are treated in Effluent
Treatment Plant (ETP) prior to their disposal in rivers or water
Courtesy: EPA Victoria