Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance or energy. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants.
Litter on the coast of Guyana
Smog in the center of Moscow, Russia in August 2010
An industrial area, with a power plant, south of Yangzhou's downtown, China
A litter trap catches floating waste in the Yarra River, east-central Victoria, Australia.
Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for both physical body, natural environment, workplace, etc.
Contamination on agar plate