What is Nitrogen and where does it come from?
Nitrogen, is a naturally occurring element essential for growth and reproduction in both plants and animals. Nitrogen is found in amino acids that make up proteins, in nucleic acids that comprise hereditary material and life's blueprint for all cells, and in several other organic and inorganic compounds. Nitrogen gas (N₂), is only directly usable as a biological nitrogen source by a certain group of bacteria.

Atmospheric N₂ is converted to nitrate (NO₃), a biologically important form, by lightning. Volatile organic nitrogen compounds are released to the atmosphere when plants decay. Industrial emissions and fossil fuel combustion contribute gaseous nitrous oxides and nitrate as nitric acid (one component of "acid rain"). Atmospheric nitrogen is delivered to sea and land in rainfall as dissolved compounds, termed "wet" deposition, and as adsorbed compounds on dust particles and leaves, or "dry" deposition. Dry deposition, or air pollution, contributes large amounts of nitrogen to watersheds. Coastal fogs are another source of nitrogen. Where the watershed covers a much larger area than does the estuary, atmospheric deposition onto the land surface rather than the estuary itself is more important.

Pollution of the air we breathe is related to many factors. Climate, humidity, concentration of air pollutants in heavily industrial and densely populated areas, thermal inversion, stagnant air masses, seasonal and perennial airborne pollens, dust, moulds, spores and ozone are a few contributors to the problems we face in the air.

Allergies are pollutants typically caused by naturally occurring airborne particles. For example, pollens in the spring and fall from grasses, weeds, trees and flowers. Allergies can be both seasonal and perennial (chronic ). Perennial or chronic allergies are due to industrial pollutants, dust, dust mites, animal dander and the like.

Ozone is the major contributor to the haze we see over our cities we call smog. Ozone (O₃), a form of oxygen (O₂) is an irritating gas with a distinct odor and is formed naturally in the upper atmosphere by a photochemical reaction with solar ultraviolet radiation or by electric discharge in the air. Ozone is also created from arc welding, flour bleaching, deodorizing, emissions from copying equipment and photochemical air pollution. Ozone is a mucous membrane irritant and causes irritation of the nose, throat, eyes and lungs. It is particularly harmful to children with asthma and to the elderly with chronic obstructive pulmonary disease.