Pollutant

A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oil) or anthropogenic in origin (i.e. manufactured materials or byproducts). Pollutants result in environmental pollution or become public health concerns when they reach a concentration high enough to have significant negative impacts. A pollutant may cause long- or short-term damage by changing the growth rate of plant or animal species, or by interfering with resources used by humans, human health or wellbeing, or property values. Some pollutants are biodegradable and therefore will not persist in the environment in the long term. However, the degradation products of some pollutants are themselves polluting such as the products DDE and DDD produced from the degradation of DDT. Pollution has widespread negative impacts on the environment. When analyzed from a planetary boundaries perspective, human society has released novel entities that well exceed safe levels. Pollutants can be categorized in a variety of different ways. For example, it is sometimes useful to distinguish between stock pollutants and fund pollutants. Another way is to group them together according to more specific properties, such as organic, particulate, pharmaceutical, et cetera. The environment has some capacity to absorb many discharges without measurable harm, and this is called “assimilative capacity (or absorptive capacity); a pollutant actually causes pollution when the assimilative capacity is exceeded. Pollutants, towards which the environment has low absorptive capacity are called stock pollutants. Examples include persistent organic pollutants like PCBs, non-biodegradable plastics and heavy metals. Stock pollutants accumulate in the environment over time. The damage they cause increases as more pollutant is emitted, and persists as the pollutant accumulates.