Heat, sound and radio-active pollution are consequences of excess amount of energy used or generated for some purpose or produced as a byproduct of some form of activity. While the generation of heat and sound energy involves conversion of one form of energy into another, nuclear energy is a consequence of disintegration of unstable nuclei, fission or fusion reaction.
The pollution caused by various physical agents is not of the usual type involving addition of unwanted or harmful factors to the environment; instead it is the excess amount of energy released in the environment which causes the troubles. Though apparently harmless in moderate amounts, heat, sound and radioactivity can cause severe damages to the biosphere if the system is exposed to them for long durations or their intensity is increased.
Many industries use heat for various purposes and need cooling systems which employ water, This results in production of heated waters in large quantities which may be discharged as such in the environment.
Various activities in our cities and most of the industrial establishments generate high levels of noise which not only interfere with hearing but also affect the peace of mind, irritability, health and behaviour of an individual. Radiations from man-made sources threaten to damage not only the existence but the very future of mankind.