How can a substance become pollutant?

A substance becomes a pollutant when it is introduced into the environment in quantities or forms that cause harmful effects on ecosystems, human health, or the climate. This can occur through industrial discharges, agricultural runoff, improper waste disposal, or accidental spills. Additionally, substances that are normally harmless can become pollutants if they exceed safe concentration levels or are released into sensitive environments. Ultimately, the impact of a substance as a pollutant depends on its toxicity, persistence, and the context of its release.