“Pollution refers to any undesirable change in the physical, chemical or biological characteristic of our environment (air, water, soil) that may or will adversely affect human or other species and life-supporting systems of our biosphere directly or indirectly.”
A substance or factor whose presence can damage the usefulness of a resource is called the pollutant.
Large quantities of various gaseous, liquid and solid waste generated by industry and other human activities act as pollutants. These are grouped into two main categories:
- Biodegradable pollutants e.g. human and animal wastes, agro based residues and fertilizers, etc. However, these can be harmful if their input exceeds the decomposing capacity of the ecosystem.
- Non-biodegradable pollutants e.g. heavy metals, D.D.T, pesticides, etc. These enter the food chains and they may be magnified to dangerous levels in higher tropic organisms.
The various categories of common pollutants may be listed as follows.
- Deposited matter (e.g. soot, smoke, tan, dust, grit)
- Gases (e.g. SO2 , CO, CO2, NO, H2 S, ammonia, fluorine, chlorine, etc.)
- Chemical compounds (e.g. aldehydes, arsines, hydrogen, fluorides, phosphogens, detergents, etc.)
- Metals (e.g. Pb, Fe, Zn, Hg, etc.)
- Ecological poisons (e.g. various biocides)
- Radioactive substances
The pollution caused by these pollutants may be classified as air pollution, water pollution and soil pollution.