What are the potential effects associated with the criteria pollutants if elevated levels are present?
Carbon Monoxide (CO) results from the incomplete combustion of fuel. CO is an odorless, colorless gas that at elevated concentrations can cause headaches and nausea. Consequently, emissions of this gas from major sources (for example motor vehicles) are regulated by federal emission standards.
Volatile Organic Compounds (VOCs) are organic chemicals that easily vaporize at room temperature. VOCs include a wide range of substances, such as hydrocarbons (for example benzene and toluene), halocarbons and oxygenates. The hydrocarbon VOCs are usually grouped into methane and other non-methane VOCs. Methane is an important component of VOCs, its environmental impact principally relates to its contribution to the production of ground level or lower atmosphere ozone. Typical sources of VOC's include incomplete fuel combustion, leakage of natural gas from distribution systems, and atmospheric chemical reactions. The evaporation of solvents can also result in releases of VOCs
Oxides of Nitrogen (NOx) are the total of nitrogen dioxide (NO2) and nitric oxide (NO). When fuel sources such as natural gas, coal, oil and gasoline are combusted, atmospheric nitrogen may combine with molecular oxygen to form NO. NO is colorless and odorless. When NO reacts with ozone (O3), it forms NO2, a reddish-brown haze with a pungent odor. Automobiles, trains and aircraft are sources of NOx. Other common sources include industrial and power plants. Typically, the largest urban source of NOx is emissions from motor vehicles. The human health effects of exposure to nitrogen oxides, such as nitrogen dioxide, are similar to those of ozone. These effects may include:
- Short-term exposure at high concentrations can decrease lung function.
- Lower concentrations can irritate lungs.
- Even low concentrations can affect lung function in asthmatics.
- Long-term lower level exposures can affect lung tissue.
- Children may also be especially sensitive to the effects of nitrogen oxides.
Particulate Matter (PM) are small particles suspended in the air. PM can come from smoke, dust and many types of combustion. They can be course particles (50-100 microns) or very small (0.005 microns). PM10 (10 microns) and smaller PM2.5 (2.5 microns) are important from a public health perspective since they are small enough to penetrate the lungs. High concentrations of PM have been associated with a range of breathing and respiratory symptoms. Currently, the U.S. EPA has a NAAQS for PM10, and for PM2.5 .