Vehicle engines, air horns, audio video' systems, trains, low flying aircrafts, factory machines, sirens, motors, drillers and crushers, compressor machines, crackers, explosives and modem supersonic transports are the common sources of noise pollution.

Acid rain is a form of precipitation that contains acidic components, such as sulfuric acid or nitric acid. It damages trees, crops and harms marine animals (coral reefs) and induces corrosion.

Increase in the concentrations of greenhouse gases such as CO₂, methane, nitrous oxide, CFCs, and ozone causes greenhouse effect, warming of the earth, resulting in sea level rise, submerging of islands and sea shores of various parts of the world

CO in the atmosphere interferes with O₂ transport since haemoglobin has greater affinity for carbon monoxide. At low concentration it causes headache and blurred vision. In higher concentration, it can lead to coma and death

(i) Transport sources - cars, buses, airplanes, trucks and trains
(ii) Stationary sources - power plants, incinerators, oil refineries, industrial facilities and factories
(iii) Area sources - agricultural - wood / stubble burning and fireplaces
(iv) Natural sources - wind-blown dust, wildfires and volcanoes.