When a contaminant become a pollutant?

A contaminant becomes a pollutant when it is present in the environment at levels that can cause harm to human health, ecosystems, or the overall quality of the environment. This transition often occurs when the concentration or exposure to the contaminant exceeds natural background levels or safe thresholds. Factors such as toxicity, persistence, and bioaccumulation also play a role in determining whether a contaminant poses a risk and thus qualifies as a pollutant.