What is the unit is usually used to denote the intensity of pollution?

The intensity of pollution is commonly measured in units such as micrograms per cubic meter (µg/m³) for particulate matter and parts per million (ppm) for gases like carbon dioxide or carbon monoxide. Other specific pollutants may have their own units, such as milligrams per liter (mg/L) for waterborne contaminants. These units help quantify the concentration of pollutants in the air, water, or soil.