What Are Pollutants, Contaminants, and Chemicals of Emerging Concerns (CECs)

The terms contaminant and pollutant are often used interchangeably, and to some degree, they overlap. However, there are essential distinctions between these two terms. Contaminants and pollutants are undesirable substances in the environment above background levels, but only pollutants produce harm. The threshold that determines when a contaminant becomes a pollutant is also nuanced, varying with species and environmental factors, of which there are more combinations than can be thoroughly examined through empirical research. This environmental complexity, coupled with the ever-increasing development and use of new chemicals for human consumption, has led to a relatively new term that describes contaminants in the environment: chemicals of emerging concern. These are chemicals that are known or suspected to be in the environment, but a firm understanding of their presence and impacts is still evolving. The chapter below explains the nuances between contaminants, pollutants, and chemicals of emerging concern in greater detail.