Air pollution is the fifth leading cause of death in India, with 620,000 premature deaths in 2010. It comes after indoor air pollution, tobacco smoking, high blood pressure, childhood underweight, low nutritional status, and alcohol use. World Health Organisation, says air pollution has become one of the top 10 killers in the world. GBD tracks deaths and illnesses from all causes across the world.

The expanded form of DDT  is dichloro diphenyl trichloroethane. This is the first modern insecticide in the year 1940 's.

In normal adults, the enzyme which catalyses conversion of MHb into Hb is MHb reductase enzyme. MHb is inactive forms that is converted into Hb that carries oxygen in blood.

Noise pollution is a kind of air pollution that may cause permanent impairment of hearing ability of human beings if its loudness is equal to or more than 150 dB.

As per supreme court guidelines 2005, a loud speaker or a public address system are not permitted at night between 10:00 pm to 6:00 am except in closed premises for communication within, like auditorium, conference room, community halls and banquet halls. Under the Environment (Protection) Act, 1986, rules for noise pollution level are framed for ambient air quality standards of noise for different areas/ zones.

Nitrogen oxides is released by lightening, fluorides from coal burning, PCBs from burning plastics and chlorofluorocarbons from jet aeroplanes emissions.

Methyl mercury is the neurotoxic form of Mercury, which can be directly absorbed by fishes. From fishes they enter to food chain and to human body causing  bio-magnification.

Oil splits over the water bodies prevents the oxygenation of water. The dissolved oxygen in water is used by aquatic organisms for respiration. It is physical pollutant.

A number of organisms grow in polluted water. The species whose concentration is highest in polluted water is called as index species as this species indicate the presence of particular kinds of pollutant in water.

Dystrophic lake have too low accumulation of dissolved nutrients to support abundant plant life so, they have very low productivity.