pollutant
This term focuses specifically on the agent of contamination rather than the state of being contaminated. While pollution describes the general process or the presence of impurities, a pollutant is the discrete substance, chemical, or particle responsible for the damage. In technical and legal contexts, pollutants are often categorized by their medium of impact, such as air pollutants or water pollutants. The word carries a strong negative connotation, implying a harmful intrusion into a pristine or balanced natural system.
Meanings
A substance or material that contaminates the natural environment, such as air, water, or soil, causing harm to living organisms or the ecosystem.
"Industrial runoff is a major pollutant in the local river system."
A specific chemical or particulate matter that is introduced into the atmosphere or water and causes pollution.
"Carbon monoxide is a dangerous pollutant emitted by vehicle exhausts."