User:Milton Beychok/Sandbox2

A pollutant is a substance that contaminates air, water or soil. Pollutants can be artificial substances, such as pesticides and fossil fuel combustion products, or naturally occurring substances, such as petroleum or carbon dioxide (CO2) that occur in harmful concentrations in a given environment. Heat transmitted to natural waterways through the discharge of warm water from industrial facilities is also considered a pollutant.

Three factors determine the severity of a pollutant: its chemical composition, concentration and persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the long term.

Notable pollutants
Notable pollutants include the following groups:


 * Ambient air quality pollutants such as sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter, carbon monoxide (CO), ozone (O3) and lead (Pb)


 * Greenhouse gases such as water vapor (H2O), ozone, carbon dioxide and methane (CH4)


 * Heavy metals such as arsenic (As), chromium (Cr), lead or mercury (Hg)


 * Persistent organic pollutants such as aldrin, chlordane, DDT, dieldrin, dioxins, endrin, furans, heptachlor, hexachlorobenzene, mirex, polychlorinated biphenyls(PCBs), and toxaphene


 * Polycyclic aromatic hydrocarbons (PAHs) are a large group of chemical compounds consisting of fused aromatic rings such as benzo(a)pyrene, benzanthracene, benzo(b)fluoranthene, fluoranthene, naphthalene to name but a few. They are formed during the incomplete combustion of carbon-containing substances and they are also manufactured for use as dyes, plastics and pesticides


 * Volatile organic compounds (VOCs)

International
Pollutants can cross international borders and therefore international regulations are needed for their control. The Stockholm Convention on Persistent Organic Pollutants, which entered into force in 2004, is an international legally binding agreement for the control of persistent organic pollutants. Pollutant Release and Transfer Registers (PRTR) are systems to collect and disseminate information on environmental releases and transfers of toxic chemicals from industrial and other facilities.

European Union
The European Pollutant Emission Register is a type of PRTR providing access to information on the annual emissions of industrial facilities in the Member States of the European Union, as well as Norway.

United States
The National Ambient Air Quality Standards (NAAQS) are air pollutant concentration standards developed for outdoor air quality. The National Emissions Standards for Hazardous Air Pollutants are emission standards that are set by the Environmental Protection Agency which are not covered by the NAAQS.