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Appendix 1. Glossary - Explanation of Air Quality Terms

Acidification - The process by which rivers, lakes, rain and other natural water features become affected by excess acid. Nitrogen dioxide (NO2) may form toxic organic nitrates which contribute to acid rain and the acidification of ground and surface water.

Aerosol - Liquid or solid particles that are small enough to become airborne. High concentrations of acid aerosols can be irritating to the lungs and have been associated with some respiratory diseases, such as asthma.

Air Quality Index - Standard unit of rating for Particulate Matter (PM) relative to hazard to humans. Rating systems vary depending on particle size. .

Ambient Air - The atmospheric environment, outside of buildings, to which the public has access.

Ambient Air Quality - A physical and chemical measure of pollutant concentrations in the ambient atmosphere, measured over a specific period of time.

Attainment Area - A pollutant is designated attainment if the state or federal NAAQS for that pollutant was not violated at any site in the area during a three-year period. This is a pollutant specific designation meaning that a single area can be designated attainment for one pollutant and non-attainment for another pollutant. Attainment areas are defined using federal pollutant limits set by EPA.

Air Quality Standard – Primary ambient air quality standards define the maximum amount of a pollutant that can be present in outdoor air without harming the public's health. Primary standards include an adequate margin of safety to protect the most sensitive individuals in the population. Secondary ambient air quality standards define levels of air quality necessary to protect the public welfare from any known or anticipated adverse effects of a pollutant. Montana Ambient Air Quality Standards (MAAQS) establish targets for acceptable amounts of air pollutants to protect human health.

Air Toxics - Any air pollutant for which a NAAQS does not exist that may reasonably be anticipated to cause cancer, developmental effects, reproductive dysfunctions, neurological disorders, heritable gene mutations, or other serious or irreversible chronic or acute health effects in humans.

Carbon Dioxide (CO2) - A heavy, colorless, odorless atmospheric gas. Carbon dioxide is produced when any substance containing carbon is burned. It is also a product of breathing and fermentation. Plants absorb carbon dioxide through photosynthesis. Although it is released by human activities through the combustion of fossil fuels, it is also formed by certain natural processes. Carbon dioxide is the principal greenhouse gas that contributes to climate change.

Carbon Monoxide (CO) - Carbon monoxide is an odorless, colorless and toxic gas. Because it is impossible to see, taste or smell the toxic fumes, CO can kill you before you are aware it is in your home. At lower levels of exposure, CO causes mild effects that are often mistaken for the flu. These symptoms include headaches, dizziness, disorientation, nausea and fatigue. The effects of CO exposure can vary greatly from person to person depending on age, overall health and the concentration and length of exposure.

Chemigation/Fertigation - Application of chemicals/nutrients respectively through an irrigation system.

Clean Air Act (CAA) - Originally passed by Congress in 1963 to regulate air quality, the Clean Air Act was greatly changed and strengthened in 1970 and 1977. In 1990, the Clean Air Act Amendments (CAAA) introduced additional programs to deal with non-attainment areas where national ambient air quality standards have been exceeded.

Conservation Management Practices - An activity or practice that land managers will implement on their lands to help reduce dust, particulate matter and other potential air pollutants from getting into the air.

Criteria pollutants - Air pollutants selected based on extensive scientific research showing direct relationship between exposure to pollutants and their short- and long-term effects on human health and the environment. The six criteria air pollutants addressed by NAAQS under Section 109 of the Clean Air Act are: particulate matter (PM2.5 and 10), carbon monoxide (CO), sulfur dioxide (SO2), lead (Pb), nitrogen dioxide (one of the NOx), and ozone (O3). Volatile organic compounds (VOCs) are not regulated directly but efforts to target smog and ozone also targets VOCs for reduction.

Dispersion - The action of the atmosphere that mixes an ambient air pollutant, thereby reducing the concentration of the pollutant.

Exceedence - A period of time where the concentration of a pollutant is greater than, or equal to the appropriate Air Quality Standard.

Fugitive Dust - Dust particles that are introduced into the air through certain activities such as soil cultivation, or vehicles operating on open fields or dirt roadways.

Hydrocarbons (HC) - Compounds that contain mostly carbon and hydrogen. Often used interchangeably with volatile organic compounds (VOCs).

Inversion - A meteorological condition in which the temperature of the atmosphere is warmer with increased elevation instead of cooling causing a stagnant layer of air to be trapped near the ground.

Micrometer - Unit of measurement for particulate matter also referred to as a micron. Equal to one millionth of a meter. A human hair is about 70 micrometers in diameter while a grain of fine beach sand is about 90 micrometers.

Micrograms per Cubic Meter (�g/m3) - A measure of pollutant concentration. Micrograms of pollutant per cubic meter of air.

Mobile Sources - Vehicles that move or can be moved including on-road (those used on roads to move passengers or freight) and non-road (vehicles used in construction, agriculture, transportation and recreation).

Montana Clean Air Act - Adopted in 1968 to require new sources of air pollution to obtain air permits. Enforceable ambient air quality standards were adopted in 1980. The MCAA exceeds the federal law in that fluoride, hydrogen sulfide (H2S), settleable particulate matter, and visibility are added as criteria pollutants under Montana’s Act.

Mulch-Till - These systems involve primary tillage of chisel plows or other non-inversion implements followed by one or more secondary tillage.

National Ambient Air Quality Standards (NAAQS) - Nationally established maximum allowable concentrations of pollutants in the ambient air often referred to the federal health standards. Primary standards are set to protect human life and health. Secondary standards are set to protect vegetation, animals and property. NAAQS regulate six common air pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, sulfur dioxide and particulate matter.

Nitrous Oxides (NOx) - Nitrogen oxides are formed during high temperature combustion processes from the oxidation of nitrogen in the air.

Nonattainment Area - A geographic area within a state that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the state’s primary or secondary ambient air quality standard for the pollutant. Once designated, a pollutant control plan is developed and submitted for inclusion in the State Implementation Plan (SIP).

No-till/Strip-Till - These systems consist of fertilizer and planting operations in narrow strips or slots that involve disturbance of less than one-third of the inter-row area.

Oxides of Nitrogen (NOx/NOx) - Gases that form when nitrogen and oxygen in the atmosphere are burned with fossil fuels at high temperatures. NOx is a precursor to ozone formation.

Particles - Any solid or liquid matter larger than a molecule (>0.0002 micron diameter). It is composed of settleable matter which will settle as dust within a reasonable period of time and suspended matter which remains suspended in the atmosphere until washed out by precipitation, deposition, or some other process.

Point Sources - Large, stationary sources of air pollutants such as factories, power plants and smelters.

Regional Haze Rule - A revision to the federal visibility regulations to integrate certain provisions addressing regional haze impairment that applies to all states. The rule reflects a comprehensive visibility protection program for all Class 1 areas except those on reservations.

Smog - A combination of high concentrations of pollutants under certain atmospheric conditions that can vary from location to location. Smog is most visible when high concentrations of water vapor and certain ambient pollutants (sulfur oxides, particulates, nitrous oxides, etc.) occur in the atmosphere at the same time.

State Implementation Plan (SIP) - A plan containing the strategies to achieve attainment of the NAAQS, and maintain air quality levels once attainment is achieved. SIPs are the regulations used by a state to reduce air pollution. A SIP call area is an area that EPA otherwise declares does not meet the air quality standard for one or more pollutants. The EPA approves all SIPs.

Stationary Sources - Non-moving, fixed site producers of pollution that includes point and area sources of air pollution.

Sulfur Dioxide (SO2) - Sulfur dioxide is an acidic gas, which combines with water vapor in the atmosphere to produce acid rain.

Track-Out - Deposition of mud and soil material carried on tires and undercarriages of vehicles from unpaved roads onto paved roads.

Volatile Organic Carbons (VOCs) - Compounds that contain carbon, oxygen, hydrogen, chlorine and other atoms that can evaporate easily into the atmosphere. They are found in nature as well as in some glues, solvents and paints. They help form O3 near the ground. VOCs vaporize (become a gas) at room temperature. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide array of products numbering in the thousands. Examples include: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions.