Air Pollution in the Mid-Atlantic Region


Ozone Effects on Health and the Environment

Ozone is the major component of summertime smog in the Mid-Atlantic Region. Ozone in the upper atmosphere is beneficial to life, shielding the earth from harmful ultraviolet radiation from the sun. In contrast, a high concentrati on of ozone in the air we breathe is a major health and environmental concern.

Ozone is formed by the reaction of gases called nitrogen oxides and volatile organic compounds. In the presence of sunlight, these gases react to form ozone.

Ozone irritates the mucus membranes of the respiratory system. High levels of ozone can cause coughing, pain when taking a deep breath, and reduced oxygen uptake. Ozone can reduce resistance to colds and pneumonia, and ozone aggravates existing respirat ory conditions such as asthma, chronic obstructive pulmonary disease, and chronic bronchitis.

Ozone also injures agricultural crops, trees, and native vegetation. High levels of ozone can reduce the growth capacity of plants and increase their susceptibility to insects and diseases. The variety or species of plant as well as other environmental factors influence the plant's sensitivity to ozone.

Ozone also damages certain fabrics, dyes, rubber, and synthetic materials such as styrene, isoprene, and butadiene. Incorporating antioxidants into the production of materials can reduce their susceptibility to damage from ozone.

Nitrogen dioxide, one of the gases that helps cause ozone pollution, also contributes to water pollution in the Mid-Atlantic Region. Nitrogen levels in coastal bays are too high. Over 25% of the nitrogen entering the Chesapeake Bay is deposited from the air. Air deposition of nitrogen to other Mid-Atlantic coastal bays ranges from 15% for the Delaware Bay to 44% for Albermarle-Pamlico Sounds at Cape Hattaras, North Carolina, according to estimates reported in 1996 by NOAA.

Because of these harmful effects to public health and the environment, ozone pollution is one of the highest priorities for pollution control in the Mid-Atlantic Region.

Sources: EPA (1996), Air Quality Criteria for Ozone and Related Photochemical Oxidants.
EPA (1994), National Air Quality and Emissions Trends Report, 1993.
R.A. Valigura, W.T. Luke, R.S. Artz, and B.B. Hicks (1996) Atmospheric Nutrient Input to Coastal Areas, Reducing the Uncertainties, National Oceanic and Atmospheric Administration (NOAA Coastal Ocean Program De cision Analysis Series No. 9).

Ozone Nonattainment Areas

Metropolitan areas where air quality does not meet national health standards for several years are designated as nonattainment areas. The following map shows the designated ozone nonattainment areas in the Mid-Atlantic Region.

Ozone nonattainment designations generally cover the entire metropolitan area, since emissions from throughout the area contribute to violations. Ozone violations occur in broad, multi-state regions.

Ozone nonattainment areas in the Mid-Atlantic Region are classified according to the severity of the ozone problem as marginal, moderate, serious, or severe nonattainment areas. Severe nonattainment areas have experienced the highest concentrations of oz one.

Map: Ozone Nonattainment Areas

Formation and Transport of Ozone

The Mid-Atlantic Region reaches from the Atlantic Coastal Plain through the rolling hills of the Piedmont into the Appalachian Mountains. The natural environment influences the formation of ozone pollution and affects the accumulation and removal of ozon e in the air.

Ozone is formed when sunlight provides energy for chemical reactions between airborne volatile organic compounds and nitrogen oxides. Often, these "precursor" gases are emitted in one area, but since the chemical reactions forming ozone take some time, t he highest ozone concentrations occur in areas different than the areas with the highest precursor emissions. Emissions can be carried hundreds of miles from their origins, forming high ozone concentrations over very large regions.

In the center of the Region, the highest ozone levels tend to be associated with slow moving or stagnant high-pressure systems. Winds at the surface tend to be light and highly variable. At the same time, upper-air patterns bring pollution into the Regi on from the west and northwest. This polluted air flows down the eastern slope of the mountains to combine with pollutants formed locally.

Several studies have demonstrated transport of polluted air into the Mid-Atlantic Region from the west or northwest. This flow of polluted air across the Appalachians is one example of what meteorologists call "synoptic" flow. In addition, pollution is transported within and out of the MARAMA Region, particularly from the southwest to the northeast along the eastern side of the Appalachian Mountains. Meteorologists call this flow along the mountains "channeled" flow (intra-regional transport of hundred s of kilometers in less than a day).

Sources: W.F. Ryan, B.G. Doddridge, and R.R. Dickerson (1996), "Observations of O3 and its Precursors During the Severe O3 Event of July 12-15, 1995 in the Baltimore-Washington Metropolitan Areas," A&WMA Annual Meeting, June 23-28.
L.A. Moy, R.R. Dickerson, and W.F. Ryan (1994), "Relationship between Back Trajectories and Tropospheric Trace Gas Concentrations in Rural Virginia," Atmospheric Environment, Vol. 28, No. 17, pp. 2789-2800.
Poulida, K.L. Civerolo, and R.R. Dickerson (1994), "Observations and tropospheric photochemistry in central North Carolina," Journal of Geophysical Research, Vol. 99, No. D5, pp. 10553-10563.
EPA, National Air Quality and Emissions Trends Report, 1995, (1996), EPA 454/R-96-005, October.
D. Blumenthal, R. Londergan, (1997), "NARSTO-Northeast Initial Results on Transport Regimes, Preliminary Material for Presentation to the Ozone Transport Commission," January 28

Map: Air Movement and Transport During the 1995 Ozone Episodes

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Last revised: 11/17/98