Session 1 Exercise

For your submission, use the following format: Print or type, in braille, your name, email, and institution in the top right-hand corner in the first space, with runovers in Cell Three. Begin brailling on Line Five.

Submit your braille either via email (if you are using one of the computer-based brailling tools). Electronic braille (Mac/PCBrailler, Duxbury, Edgar, Megadots, Pokadots) should be sent via email to rbroadnax@shodor.org. You can also use the text box at the bottom of this page to submit your work. Simply cut and paste the braille into the box, then click on the "Submit braille" button.

No hardcopy braille is accepted. All submissions must be done electronically, using any of the braille preparation software packages (Duxbury, Megadots, Edgar, Pokadot, etc.)

Atmospheric circulation usually prevents smog from settling. However, stagnant air masses keep ozone from dissipating, creating the potential for serious smog conditions. Sometimes ozone and other pollutants are trapped near the ground by a temperature inversion; a stable layer of cold air trapped under a layer of warmer, less dense air. Rain often improves air quality by both "raining out" pollutants and cooling air temperatures. Often, ozone and ozone precursors produced in one area are transported by winds to another area. For example, pollutants formed in New York City may show up as elevated ozone levels in rural Maine. Geographical conditions, such as mountains, valleys, and bodies of water may also have an effect on the transport of pollutants. For example, mountains often block the transport of air so that stagnant air remains in the valley (as in the Los Angeles basin). In coastal areas, land and sea breezes may transport pollutants offshore during the afternoon (when the land is warmer than the sea) and onshore during the evening (when the sea is warmer than the land).

As we've mentioned several times, ozone is a powerful oxidant. Oxidants cause redox chemical reactions in which one substance is broken down (e.g., iron rusts, silver tarnishes, fabric colors fade) -- usually by the breaking of a chemical bond and the formation of a new bond containing oxygen. When ozone oxidizes another substance, one of the oxygen atoms in ozone chemically combines with that substance, and the ozone is converted to oxygen.

Ozone has widespread harmful effects on the health of humans and animals, vegetation, and materials. Ozone, like many other oxidants, irritates the mucous membranes of the respiratory system, causing coughing, nausea, shortness of breath, pulmonary congestion, and impaired lung function. It aggravates chronic respiratory diseases, such as asthma and bronchitis, and can cause serious health problems for people in weakened health and the elderly. Peroxyacetyl nitrates (PAN) and other oxidants that accompany ozone are powerful eye irritants. Exposure for 6-7 hours or more reduces lung function significantly in healthy people during periods of even moderate exercise.

Ozone damages the leaves of plants and trees. Some plant species, such as tobacco, spinach, tomatoes and pinto beans, are especially sensitive. Damaged plants develop necrotic patterns (brown specks that turn yellow) on the upper surfaces of their leaves. The necrotic patterns on the tobacco strain Bel-W3 may be used as a indicator of ozone levels. Annually, ozone causes millions of dollars in crop loss. It also causes premature leaf drop in trees and reduced growth rates.

Ozone reacts easily with organic materials -- causing weakness, cracking, and other chemical changes. Ozone cracks stretched rubber, reduces the strength of textiles, causes fading in fabrics and dyes (cotton, acetate, nylon, polyester), and causes premature cracking in paint.

Photochemical oxidants were first noticed in the early 1940s in Los Angeles. By 1960, photochemical smog had been identified as a national problem. In 1963 the first Clean Air Act authorized the Public Health Service to study air pollution and provided training to state and local agencies to control it. The Clean Air Act of 1970 strengthened this legislation by creating a partnership between state and federal governments. State and local governments became responsible for preventing and controlling their air pollution. The Environmental Protection Agency (EPA) was established to set national pollution regulations and standards.

In 1979, the EPA established primary and secondary standards for pollutants called "National Ambient Air Quality Standards" (NAAQS). Primary standards protect human health while secondary standards protect crops, livestock, vegetation, and materials. The primary and secondary standards for ozone are 120 parts per billion (ppb). A state is out of compliance if it exceeds the standard more than one day per year over a three-year average. The Clean Air Act of 1990 requires states to submit "State Implementation Plans" outlining how they will comply with these standards.

Reduction of ground-level ozone is a complicated problem with no easy solution. It will require cooperation between government, business and individuals. Methods for controlling industrial and automotive emissions include: conservation, use of alternative fuels, and development of new technologies. Conservation measures include a shift away from the use of automobiles and toward public transportation, carpooling, bicycling, and walking. Conserving energy (electricity, heating, air conditioning) also helps, since most of our energy comes from the burning of fossil fuels (oil, coal, natural gas) that contribute ozone-producing emissions. Alternative fuels include methanol, ethanol, natural gas (methane), and hydrogen. However, their use runs the risk of solving one problem by creating another. New technologies will make it possible to reduce fuel consumption and emissions. Through new technology, the sun could provide non-polluting solar power to heat homes, power cars, or cook meals. The most promising solution to ozone reduction could be a combination of technological, social, and economic changes.