GlossaryHeading	GlossaryDetails
National Ambient Air Quality Standards (NAAQS)	An air quality standard set by the US EPA as required by the Clean Air Act. The primary standard for a pollutant is the maximum concentration of that pollutant (over a specified averaging period) that should be observed within a community for the protection of human health. The secondary standard is designed to protect the community welfare.
Natural gas	It is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes.
Natural resources	A feature or component of the natural environment that is of value in serving human needs (ex: soil, water, plant life, wildlife etc.). Some natural resources have an economic value (ex: timber) while others have uneconomic value (ex: scenic beauty).
Nausea	An unpleasant sensation with a tendency to vomit.
Necrosis	It is a form of cell injury that results in the premature death of cells in living tissues by autolysis.
Non renewable resources	Resources not capable of perpetuating themselves (ex: coal, oil and minerals). Resource that exists in a fixed amount (stock) in various places in the earth’s crust and has potential for renewal only by geological, physical and chemical processes taking place over hundreds of millions of years. These are exhaustible because we are extracting and using them at a much faster rate than they were formed.
Non-Point Sources	Diffuse pollution sources that are not recognized to have a single point of origin.
Noxious gases	are very harmful, poisonous, or very unpleasant.