The term criteria pollutant comes from the fact that health‐based criteria were used to establish the National Ambient Air Quality Standards (NAAQS) for these pollutants (USEPA 2009b). The NAAQS for these pollutants are established by EPA to protect public health and welfare.
Table 3.8 Criteria air pollutants.
| EPA criteria air pollutants | ||
| Pollutant | Sources | Health and environmental effects |
| Ozone (O3) ground‐level A colorless gas that forms as a result of chemical reactions between volatile organic compounds (VOCs), nitrogen oxides (NOx), and oxygen in the presence of heat and sunlight. | Motor vehicles, electric utilities, factories, landfills, industrial solvents, and miscellaneous small sources such as gas stations, lawn equipment, etc. | Causes coughing, chest tightness, wheezing and can inflame and damage lung tissue. Aggravates asthma and can even be a cause of asthma. Irritates the respiratory system, reduces lung function, and makes it more difficult to breathe. Aggravates chronic lung diseases and may cause permanent lung damage. May reduce yield of agricultural crops and damages forests and other vegetation. |
| Carbon monoxide (CO) An odorless, colorless gas resulting from incomplete fossil fuel combustion. | Motor vehicles (the majority of CO in NH), small engines, some industrial processes, boilers, and incinerators. High concentrations can be found in confined spaces like parking garages, poorly ventilated tunnels, or traffic intersections especially during peak hours. | Impairs the ability of blood to deliver oxygen to vital tissues affecting the cardiovascular, pulmonary, and nervous systems. Symptoms include dizziness, headaches, nausea, fatigue, memory and visual impairment, and decreased muscular control. |
| Nitrogen dioxide (NO2) A brownish gas that forms quickly when fuel is burned at high temperatures. Contributes to the formation of ground‐level ozone and fine particle pollution. | Motor vehicles, electric utilities, industrial boilers, and off‐road equipment. | Irritates the lungs, may cause lung damage and lower resistance to respiratory infections such as influenza. May adversely affect terrestrial and aquatic ecosystems through regional transport and deposition. |
| Particulate matter (PM) Mixture of solid particles and liquid droplets in the air; particles may be visible or microscopic. | Formed directly from windblown dust, crushing and grinding operations, unpaved roads and construction, fuel combustion (from motor vehicles, power plants, industrial facilities), wood stoves, and agriculture (plowing, burning off fields). May also be formed in the atmosphere from gases such as SO2 and NOx. | Causes eye, nose, and throat irritation, decreased lung function, aggravated asthma, development of chronic bronchitis, irregular heartbeat, nonfatal heart attacks, and premature death in people with heart or lung disease. Serves as a carrier for toxic metals, damages human‐made materials, and is a major cause of reduced visibility in many parts of the United States. |
| Sulfur dioxide (SO2) A highly reactive colorless gas, odorless at low concentrations, but pungent at very high concentrations. | Formed when fuel containing sulfur (mainly oil and coal) is burned in industrial, institutional, utility, and residential furnaces and boilers. Other sources include petroleum refineries, smelters, paper mills, and chemical plants. | May cause breathing problems, respiratory illness, alterations in the lungs defenses, aggravation of existing cardiovascular disease, and permanent damage to lungs. Forms acid aerosols and sulfuric acid, which are associated with acidification of lakes and streams, accelerated corrosion of buildings and monuments, and reduced visibility. |
| Lead A heavy metal found naturally in the environment and in manufactured products. | Soil, dust, paint, etc., transportation sources using lead in their fuels, coal combustion, smelters, car battery plants, and combustion of garbage containing lead products. | Elevated levels can cause brain and other nervous system damage and adversely affect kidney function, blood chemistry, and digestion if ingested or directly inhaled. Children are at special risk due to cumulative effects even at low doses. Lead can also harm wildlife through deposition onto leaves which are a food source for grazing animals. |
Criteria air contaminants (CAC) or criteria pollutants are a set of air pollutants that cause smog, acid rain, and other health hazards. CACs are typically emitted from many sources in industry, mining, transportation, electricity generation, and agriculture. In most cases, they are the products of the combustion of fossil fuels or industrial processes (Table 3.8).
NAAQS have been established for six criteria air pollutants – five primary (meaning emitted directly) and one secondary pollutant (because it is formed in the lower atmosphere by chemical reactions among primary pollutants).
The five primary criteria pollutants are particulate matter less than 10 μm in diameter and particulate matter less than 2.5 μm in diameter (PM −10 and PM −2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and particulate lead (Pb); theReichstein secondary criteria pollutant is ozone (O3). Among these six pollutants, the first four are emitted in the United States (and other large industrialized countries) in quantities measured in millions of metric tons per year and are sometimes called major primary pollutants. Another class of pollutant – VOCs – though not a criteria pollutant, is recognized as a major primary pollutant because of its large emissions (both anthropogenic and biogenic sources) and its importance in the atmospheric reactions that form ground‐level ozone.
Leave a Reply