Substance that causes pollution is called a pollutant.
Pollution is an unwanted change in the physical, chemical and biological characteristics of land, water, and air.
It occurs due to the contamination of the environment through wastes, chemicals and other harmful substances.
Pollution types:
  1. Air pollution
  2. Water pollution
  3. Land or soil pollution
  4. Noise pollution
Air pollution
Air pollution is mainly caused due to the burning of fossil fuels (oil, petrol, coal and natural gas). Fossil fuels are commonly used in industries, power plants, and motor vehicles. Burning fossil fuels release fine particles and toxic gases (ash and soot) into the atmosphere that cause air pollution.
Air pollution is also due to the burning of solid wastes (especially low-grade plastics), factories that release gases or chemicals, and fumes from aerosols (deodorant spray cans) or paints.
Toxic gases that are produced in the industries can mix with raindrops present in the atmosphere. The rain thus becomes acidic, and the phenomena is called as acid rain. Acid rain damages the plants wash nutrients from the soil and also kills fish.
Air pollution is harmful to all the living organisms, including humans. The polluted air affects the skin, eyes and the respiratory system.
Ways to reduce air pollution:

1. Cycling or walking short distances, rather than using a motor vehicle.
2. Travel through public transportation (bus or train)
3. Solid wastes must not be burnt.
4. Fireworks and crackers should be avoided.
Water Pollution
Water pollution occurs when wastes from factories, houses, and farms mixes with water bodies (rivers, lakes, ponds, ocean, groundwater). Contaminated water with chemical can cause and spread diseases.
The significant sources of water pollutants include:

1. Sewage (water used at home for bathing, cleaning, cooking).
2. Industrial effluents (liquid wastes from factories).
3. Agricultural pollutants (chemical pesticides, fertilisers that get washed from farms).
4. Solid waste (wastes dumped in to the water bodies).
Ways to reduce water pollution:
1. Leftover oil, old medicines should not be let down into the drain or toilet.
2. The usage of chemical pesticides and fertilisers supplied for the growth of crops must be reduced.
3. For garden, wastewater must be used in home.
4. Do not litter or dump waste - always use a trash bin or waste bin.
Land or soil pollution
Land or soil pollution takes place when toxic chemicals changes the soil's natural balance. Land pollution results due to farming (excess usage of chemicals - pesticides and fertilisers), mining (digging metals and other materials), factories that release industrial wastes, and the solid waste generated from houses (plastics, broken electronics).
Soil pollution affects plants, animals, and even humans, as the soil (land) acts as a sponge. When there is rain, pollutants present in the soil sinks into the ground. If plants grown in the polluted soils are consumed, these dangerous chemicals get into our food.
Ways to reduce land pollution:
1. First try to reduce waste, then recycle the rest.
2. Always use a waste bin and never litter.
3. Do not burn waste, the ash mixes easily with soil.
Noise pollution
Noise pollution affects the environment. Unpleasant or loud sounds disturbs the environment. Loud
music, sounds of motor vehicles, fireworks, and machines cause noise pollution. Continuous noise disturbs sleep and do not let us study. Noise pollution has been linked to stress and adverse health effects like high blood pressure, hearing loss. Loud noise and loud music damages the ears.
Noise pollution disturbs animals. Birds need to communicate louder so that they can hear in noisy areas. Underwater noise pollution from ships affects the whales as they are unable to use sounds for navigation. Thus, whales lose their way.
Ways to reduce noise pollution:
1. Turn off electronics when not in use.
2. Lower the volume of television when watching or listening to music.
3. Drivers should not use too much of horn.
4. Fireworks must be avoided.
5. All of us (humans) express through speech. We must speak, and not shout.