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 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

The Natural Variability is the inconstancy that is inherent or natural to the media, objects, processes, or biota being studied.

A Negative Pressure is a condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas.

A NOCT is Nominal Operating Cell Temperature, the temperature at which Cells in a Module operate under Standard Operating Conditions (SOC), which are: irradiance of 0.8 kW/m², 20_C ambient temperature, and average windspeed of 1 m/s, with the wind oriented parallel to the plane of the array, and all sides of the array fully exposed to the wind.

A Non-Conformity, Minor is an indication or judgment that a process, product, or service has isolated discrepancies from the stated requirements which may or may not significantly impact the product.

Nonliving. compare biotic

Nonparametric Tests are all studies involving ranked data, i.e., data that can be put in order and used when there is no assumption that the population has a normal distribution or when the population is known to have low and high values and valuable in detecting population differences when certain assumptions are not satisfied.

A Nonroad mobile sources is a Mobile sources not found on roads and highways (e.g., airplanes, trains, lawn mowers, construction vehicles, farm machinery).

The Normal Distribution (statistical) is a frequency of data occurrence where most of the data points are located near the mean; seen statistically as a symmetrical bell-shaped curve.