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An Ozone Action Day, which can be declared by a local municipality, county or state, is observed at certain times during the summer months, when weather conditions (such as heat, humidity, and air stagnation) run the risk of causing health problems. Ozone Action Days, alternately called an "Ozone Alert" or a "Clean Air Alert", primarily center in the midwestern portion of the United States; particularly in well-urbanized areas such as Chicago, Cleveland, Detroit, and Indianapolis. ==Surface ozone vs. the ozone layer== Although the ozone found at the Earth's surface is the same chemical species as that found in the ozone layer, they have very different sources, atmospheric chemistry, and affect human health differently as well. The ozone layer protects people from the sun's most damaging ultraviolet rays. Because the ozone layer is located high in the atmosphere, people are not directly exposed to it. Ground-level ozone, however, is a health hazard because people breathe it. It is formed through a complex set of chemical reactions involving hydrocarbons, nitrogen oxides and sunlight on calm summer days where the weather may also be warm and humid.〔()〕 High levels of ground ozone affects the breathing process and aggravates asthma in chronic sufferers. The young, elderly, and those with lung diseases are especially susceptible. Ozone is most likely to exceed safety limits from May through October when seasonal heat and sunlight are at their highest However, similar conditions can occur at other times of the year in specific urbanized areas; namely the Los Angeles area, which is well known for smog formation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ozone Action Day」の詳細全文を読む スポンサード リンク
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