Pollutants are substances or forms of energy that contaminate the environment and adversely affect living organisms, ecosystems, and human health. In human ecology, pollutants are studied as significant environmental stressors that influence the biological adaptation, cultural practices, and survival of human populations. Human activities such as industrialization, urbanization, agriculture, mining, transportation, and improper waste disposal have greatly increased the quantity and diversity of pollutants in the environment. Pollutants may be classified into physical, chemical, and biological categories. Physical pollutants include noise, heat, radiation, and particulate matter that alter environmental quality without necessarily involving chemical reactions. Chemical pollutants consist of toxic substances such as pesticides, heavy metals, fertilizers, plastics, petroleum products, and industrial chemicals. Biological pollutants include pathogenic microorganisms such as bacteria, viruses, fungi, parasites, and allergens that spread diseases among humans and other organisms. Another common classification distinguishes biodegradable and non-biodegradable pollutants. Biodegradable pollutants, such as