Air pollutants can come from point source emissions (large stationary such as fossil fuel fired power plants, smelters, industrial boilers, petroleum refineries, and manufacturing facilities) and non-point (area, on-road mobile, non-road mobile, and biogenic) sources. The discharge of these emissions affects the quality of the air and also has effects on human health, plant and animal life, and the aesthetic beauty of Nevada. The pollutants listed below are regulated by both the state and federal agencies.
Criteria Pollutants
The National Ambient Air Quality Standards (NAAQS) consist of six principal pollutants called ““criteria” air pollutants” which are considered harmful to public health and the environment. The Clean Air Act identifies two types of NAAQS. Primary standards, which provide public health protection, including protecting the health of “sensitive” populations such as asthmatics, children, and the elderly. Secondary Standards, which provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.
The six “criteria” air pollutants which are classified under the NAAQS are:
Carbon Monoxide (CO)
Carbon monoxide is produced primarily by motor vehicles. It can reduce a person’s ability to think clearly and causes visual impairment and headaches if high enough concentrations are experienced for a long period of time.
Lead (Pb)
For many years, lead was primarily emitted to the atmosphere from motor vehicles that burned leaded gasoline. Lead can affect the central nervous system and lead to anemia. The young and the elderly are most susceptible to the harmful effects of lead.
Nitrogen Dioxide (NO2)
Nitrogen dioxide, which is a primary component of nitrogen oxides (NOx), is produced when fuel is burned in motor vehicles, power plants, industrial boilers and other sources. Nitrogen dioxide can place a strain on the heart and respiratory system and can increase a person’s susceptibility to respiratory infections.
Ozone (O3)
Ozone is a gas composed of three oxygen atoms. It is formed in a chemical reaction between the diatomic oxygen molecule (O2) and an oxygen atom (O). Since there is abundant O2in the atmosphere, the key to ozone formation is the availability of free oxygen atoms. At ground level, these oxygen atoms are primarily created from the breakup of nitrogen dioxide (NO2) by solar radiation. The amount of NO2 available is regulated by a complex chemistry involving volatile organic compounds (VOCs) and other oxides of nitrogen (NOx) in the presence of heat and sunlight.
In the upper atmosphere (stratosphere), oxygen atoms are created as a result of the breakdown of the oxygen molecule (O2) by ultraviolet radiation.Ozone has the same chemical structure and properties whether it occurs miles above the earth or at ground level; however, ozone has both good and bad effects depending on its location in the atmosphere. Ozone occurs naturally in the stratosphere approximately 10 to 30 miles above the earth’s surface and forms a layer that protects life on earth from the sun’s harmful ultraviolet radiation (good effect). In the lower atmosphere, where natural ozone levels are low, additional ground-level ozone is formed as a result of human emissions of VOCs and NOx. Breathing this ozone can result in damage or irritation to the lungs (bad effect).
Particulate Matter (PM2.5 and PM10)
Particle pollution is the general term used for a mixture of solid particles and liquid droplets found in the air. This pollution, also known as particulate matter, is made up of a number of components, including acids (such as sulfates and nitrates), organic chemicals, metals, soil or dust particles, and allergens (such as fragments of pollen or mold spores.
The size of the particles is directly linked to their potential for causing health problems. Small particles pose the greatest threat. PM5 describes the small particles of concern; they are “fine particles” (such as those found in smoke and haze), which are 2.5 micrometers in diameter or less. “Coarse” particles describe particles greater than 2.5, but less than or equal to 10 micrometers in diameter. PM10 refers to all particles less than or equal to 10 micrometers in diameter. Ten micrometers are about one-seventh the diameter of human hair. Particle pollution originates from many different stationary and mobile sources as well as from natural sources. Fine particles can result directly from emissions of fuel combustion from motor vehicles, power generation and industrial facilities, as well as from residential fireplaces and wood stoves.
Sulfur Dioxide (SO2)
Sulfur dioxide (SO2) is produced by power plants and industries that burn fossil fuels containing sulfur, such as coal and oil, and by the phosphate industry through its production of sulfuric acid. SO2 is irritating to the lungs and can result in a higher incidence of respiratory disease.
Air Toxics
Air toxics (also called hazardous air pollutants) are those air pollutants known or suspected to cause cancer or other serious health effects, such as reproductive and birth defects. The degree to which a toxic air pollutant affects a person’s health depends on many factors including the quantity and toxicity of the pollutant to which the person is exposed as well as the duration and frequency of exposure.
Air toxics can come from natural sources (e.g., radon gas coming up from the ground) or man-made sources such as motor vehicles and industrial processes. Air toxics that deposit onto soil or into lakes and streams can affect ecological systems and eventually human health through consumption of contaminated food.
The federal Clean Air Act targets 188 toxic air pollutants for emissions reduction. Examples include benzene, which is found in gasoline; perchloroethylene, which is emitted from some dry cleaning facilities; and methylene chloride, which is used as a solvent and paint stripper by a number of industries. Other examples are dioxin, asbestos, and metals such as mercury, chromium and lead. The Nevada Division of Environmental Protection ensures that industries in the state comply with the limits on toxic air pollutant emissions established under the Clean Air Act.