Glossary

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National Ambient Air Quality Standards (NAAQS)
Standards established by the EPA that apply to outdoor air throughout the country.

National Institute of Occupational Safety and Health (NIOSH)
An agency of the Centers for Disease Control of the Department of Health and Human Services. NIOSH is the research arm of OSHA.

Natural siting criteria
An approach where the locations of roads, buildings, and other structures are selected to be where the geological and biological factors are most favorable; essentially "working with nature" when selecting locations for human-made structures.

Natural Ventilation
The process of air moving into and out of a building through intentional routes (e.g., windows, grilles), without the assistance of mechanical equipment.

Net Present Value
Determination of current value of buildings and components in today's dollars that reflects a stream of current and future benefits and costs; projected future costs and benefits must be discounted to give a fair value in today's dollars.

Neurotoxin
A substance that can cause damage to nerve cells or the nervous system.

Niche
An organisms "occupation," or how it lives.

Nitric Oxide (NO)
A gas formed by combustion under high temperature and high pressure in an internal combustion engine, and then converted by sunlight and photochemical processes in ambient air to nitrogen oxide. Nitric oxide is a precursor of ground-level ozone pollution, or smog.

Nitrogen Oxide (NOx)
The result of photochemical reactions of nitric oxide in ambient air. It is a major component of photochemical smog, a product of combustion from transportation and stationary sources, and a major contributor to the formation of ozone in the lower atmosphere and to acid deposition.

No Observable Adverse Effect Level (NOAEL)
An exposure level at which there are no statistically or biologically significant increases in the frequency or severity of adverse effects between the exposed population and its appropriate control; some effects may be produced at this level, but they are not considered as adverse, or as precursors to adverse effects. In an experiment with several NOAELs, the regulatory focus is primarily on the highest one, leading to the common usage of the term NOAEL as the highest exposure without adverse effects.

Non-Potable Water
Undrinkable water.

Nonhazardous Waste
Waste that is not classified as hazardous.

Nonrenewable Energy
Energy derived from depletable fuels (oil, gas, coal) created through lengthy geological processes and existing in limited quantities on the earth.

Nonrenewable Resource
A resource that cannot be replaced in the environment (i.e., fossil fuels) because it forms at a rate far slower than its consumption.

Nuclear Power
The use of nuclear fission reactions to generate electricity.