A "N" in a Million Cancer Risk is a risk level of "N" in a million implies a likelihood that up to "N" people, out of one million equally exposed people would contract cancer if exposed continuously (24 hours per day) to the specific concentration over 70 years (an assumed lifetime).

A NADP is National Atmospheric Deposition Program.

A Narrative Biological Criteria is general statements of attainable or attained conditions of Biological Integrity and water quality for a given designated Aquatic life use.

A National Academy of Sciences (NAS) is the National Academy of Sciences/National Research Council (NRC) performs level 2 peer review to determine if EMAP projects have overall scientific merit and integrate both internally and with other government-sponsored monitoring programs.

- National Air Toxics Assessment (NATA) : A National Air Toxics Assessment (NATA) is EPA's ongoing comprehensive evaluation of Air Toxics in the U.S. These activities include expansion of Air Toxics monitoring, improving and

- National Ambient Air Quality Standards: - National Ambient Air Quality Standards (NAAQS): : A National Ambient Air Quality Standards (NAAQS): is In 1971,

National Primary Drinking Water Regulations are Legally enforceable standards that apply to public water systems.

A National Priorities List (NPL) is EPA"s list of the most serious uncontrolled or abandoned Hazardous Waste sites, identified as candidates for Long-Term Action using money from the

National Recreation Areas are areas of federal land that have been set aside by Congress for recreational use by members of

A National Toxics Inventory is EPA's compilation of quantitative information concerning the mass of Air Toxics emitted into the atmosphere (through smokestacks, tailpipes, vents, etc.