Peroxyacetyl Nitrate (PAN)A group of compounds formed from the photochemical reactions of nitrogen and organic compounds. PANs are components of smog and known to cause eye irritation.
PersistenceRefers to the length of time a compound stays in the atmosphere, once introduced. A compound may persist for less than a second or indefinitely.
Persistent Organic Pollutants (POPs)They are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of this, they have been observed to persist in the environment, to be capable of long-range transport, bioaccumulate in human and animal tissue, bioaccumulate in food chains, and to have potential significant impacts on human health and the environment.
Photochemical ReactionA term referring to chemical reactions brought about by the light energy of the sun. The reaction of nitrogen oxides with hydrocarbons in the presence of sunlight to form ozone is an example of a photochemical reaction.
Photochemical SmogComplex mixture of air pollutants (oxidants) produced in the atmosphere by the reaction of hydrocarbons and nitrogen oxides under the influence of sunlight. Three of the most harmful photochemical oxidants are ozone (O3), peroxyacetyl nitrate (PAN) and various aldehydes.
PhotolysisChemical decomposition induced by light or other energy.
PlumeA visible or measurable discharge of a contaminant from a given point of origin that can be measured according to the Ringelmann scale.
PM 2.5 (Particulate Matter)Tiny particles with an aerodynamic diameter less than or equal to a nominal 2.5 microns. This fraction of particulate matter penetrates most deeply into the lungs.
PM10A criteria air pollutant consisting of small particles with an aerodynamic diameter less than or equal to a nominal 10 microns (about 1/7 the diameter of a single human hair). Their small size allows them to make their way to the air sacs deep within the lungs where they may be deposited and result in adverse health effects. It also causes visibility reduction .
Point sourceA single identifiable source that discharges pollutants into the atmosphere. Ex: Smokestack of power plant, chimney of a house etc.
PoisoningPoisoning occurs when any substance interferes with normal body functions after it is swallowed, inhaled, injected, or absorbed.
Pollutant Standards Index (PSI)A numerical index formerly used for reporting severity of air pollution levels to the general public. The PSI incorporated the five criteria pollutants -- ozone, PM10, carbon monoxide, sulphur dioxide and nitrogen dioxide -- into one single index. The higher the index, the higher the level of pollutant and the greater likelihood of health effects.
PollutionAddition of some exogenous substances in the environment which are harmful for organisms including human beings.
Pollution cleanupDevices or process that removes or reduces the level of a pollutant after it has been produced or has entered the environment. Ex: Automobile emission control devices.
Pollution preventionDevice, practices or processes that prevent a potential pollutant from forming or from entering the environment or that sharply reduces or minimizes the amounts entering the environment.
Polychlorinated biphenyls (PCBs)Group of 209 different toxic, oily, synthetic chlorinated hydrocarbon compounds that can be biologically amplified in food chains and webs.
Polycyclic Aromatic Hydrocarbons (PAHs)Organic compounds which include only carbon and hydrogen with a fused ring structure containing at least two benzene (six-sided) rings. PAHs may also contain additional fused rings that are not six-sided. The combustion of organic substances is a common source of atmospheric PAHs.
PopulationGroup of individual organisms of the same species living within a particular area
Population densityNumber of organisms in a particular population found in a specified area.
Power plantsA power plant (also referred to as a generating station, power plant, powerhouse or generating plant) is an industrial facility for the generation of electric power. Each power station contains one or more generators, a rotating machine that converts mechanical power into electrical power by creating relative motion between a magnetic field and a conductor. The energy source harnessed to turn the generator varies widely. Most power stations in the world burn fossil fuels such as coal, oil, and natural gas to generate electricity, and some use nuclear power, but there is an increasing use of cleaner renewable sources such as solar, wind, wave and hydroelectric.
PrecipitationWater in the form of rain, sleet, hail and snow that falls from the atmosphere onto the land and bodies of water.
Primary pollutantChemical that has been added directly to the air by natural events or human activities and occurs in a harmful concentration.