Ozone Action Day
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An Ozone Action Day, which can be declared by a local municipality, country 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 affect the breathing process and aggravate 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.
Sources of ground ozone
A major cause of the conditions is due to pollutants in the air released by heavy industry (manufacturing plants, refineries, coal-fired power plants). Therefore, Ozone Action Days occur most frequently in the Midwestern United States. In recent years, many sites have taken steps to help reduce the amount of pollutants they discharge.
Secondary sources include automotive emissions (leaky auto exhaust systems, excessive engine idling) and liberal use of household chemicals or sprays.
Surface Ozone Limits
In 2008, the EPA created “non-attainment areas” for ozone in which ozone levels shall not exceed the federal standard of 75 parts per billion averaged over the course of three years. The EPA put the revised ozone standard into effect on October 1, 2015. This means that high altitude cities will have a more difficult time meeting the new federal standards. This is due to higher ozone concentrations (Denver-metro area) moving to areas of lower ozone concentrations (rural, mountain areas).
For example, the high altitude state of Colorado is working on reducing the overall amount of ozone throughout the state. The Denver Metropolitan and North Front Range areas specifically have violated the national ozone standards in the last several years. All other counties in Colorado are in compliance with the 75 ppb standard set by the EPA in 2015. Denver is currently the 8th most polluted area due to ozone in the United States. In 2015, Denver was ranked the 13th most-polluted city in the United States. Experts cite coal mining, population growth, and the oil and gas industries as potential reasons for the Denver metro area becoming more polluted.
Occupational Safety and Ozone
In order to ensure safe ozone levels in an occupational setting, federal regulations are in place in order to enforce workplace exposure limits for all working men and women. These measures are not implemented as a response to Ozone Action Days but rather they are in place in order to reduce the levels of ozone and contribute to the overall reduction of ground ozone in the environment.
Congress created the Occupational Safety and Health Administration (OSHA) in response to the Occupational Safety and Health Act of 1970. To address the issue of ozone in the work environment, OSHA set a legal airborne permissible exposure limit of 0.1 parts per million (ppm) averaged over an 8-hour work shift.
The National Institute for Occupational Safety and Health (NIOSH) also provides thorough information to ensure a safe working environment by conducting research and making recommendations for the prevention of work-related disease and injury. They recommend an airborne exposure limit for ozone of 0.1ppm, which should not be exceeded at any time.
The American Conference of Government Industrial Hygienists (ACGIH) is a member-based organization of industrial hygienists and individuals in the occupational and environmental health and safety industry. They recommend an airborne exposure limit of 0.05ppm for heavy work, 0.08ppm for moderate work, and 0.1ppm for light work. If work is done for less than two hours the ACGIH recommends an exposure airborne limit of 0.20pmm averaged over an 8-hour work shift.
It is important to note that engineering controls are the most effective way of reducing airborne exposure of ozone (unless the exposure is the result of chemical use, in which exposure can possibly be reduced by substituting a less hazardous chemical). These controls include proper ventilation systems, proper respirators and protective clothing.
Public Health and Ground Ozone
Surface Ozone as Asthma Trigger
Millions suffer from asthma and it is one of the most common long term illnesses of children. It causes wheezing, breathlessness, chest tightness, and coughing. If symptoms get worse, they may end up getting hospitalized. Asthma exacerbations can be triggered by many factors such as tobacco smoke, dust mites, air pollution, pets, and mold. Surface ozone is also one of them. Surface ozone is one of the most common air pollutants and causes airway irritation. It can also reduce lung function. Studies show that areas with higher ozone levels have higher doses of asthma medications and increased emergency room visits, 
Differences in Health Risk After Ozone Exposure
There are differences between groups in both the magnitude of exposure to ozone as well as the ultimate health effects from the exposure. A study of 98 communities found that community characteristics changed the health impacts of ozone exposure. A greater effect of ozone was associated with higher unemployment, increased African American populations, increased public transportation use and use of central air conditioning. This could be due to increased exposure in these communities or other underlying health disparities that are exacerbated by the exposure to ozone.
This differential effect of ozone on health holds true for asthma and ozone exposure as well. In a longitudinal, prospective study, men who were exposed to a 27 parts per billion increase were found to have a 2-fold increase in asthma diagnosis. Although this trend was not found for women, the size of this ozone effect was not diminished when the researchers considered other air pollutants such as (PM10, SO4, NO2, and SO2). Additionally, it was found that after ozone levels equaled or exceeded 0.11 ppm, there was a 37% increase in hospital visits for asthma for African American families in low income areas. These gender, socioeconomic status and race differences need to be investigated further and solidify ozone exposure as a public health problem to be solved in the coming years.
Legalities of States Exceeding EPA Ozone Limits
Colorado is working on reducing the overall amount of ozone throughout the state. The Denver Metropolitan and North Front Range areas specifically have violated the national ozone standards in the last several years. All other counties in Colorado are in compliance with the 75 ppb standard set by the EPA in 2015. Denver is currently the 8th most polluted area due to ozone in the United States (Finley, 2016). In 2015, Denver was ranked the 13th most-polluted city in the United States. Experts cite coal mining, population growth, and the oil and gas industries as potential reasons for the Denver metro area becoming more polluted.
In 2008, the EPA created “nonattainment areas” for ozone in which ozone levels shall not exceed the federal standard of 75 parts per billion averaged over the course of three years.
The EPA put the revised ozone standard into effect on October 1, 2015 (Salley, 2015). This means that high altitude cities will have a more difficult time meeting the new federal standards. This is due to higher ozone concentrations (Denver-metro area) moving to areas of lower ozone concentrations (rural, mountain areas).
State, county, and even local governments can announce Ozone Action Days as much as a day in advance through the monitoring of approaching weather conditions and the air quality index (AQI). The AQI is divided into six levels: the higher the number (on a 0-300 scale), the more severe the ozone threat.
AQI of greater than 101 is considered dangerous for people with asthma, and asthma sufferers can take necessary precautions to avoid attacks. An AQI above 150 is considered unhealthy for all populations. They may check the AirNow EPA current air quality index for the most up to date information.
What can be done
Heavy industries make up a high percentage of pollutants causing ground ozone. Without drastically altering or eliminating industrial production in an area altogether, air quality improvements are very slight, though noticeable. Non-industrial pollutants, while not thought of to be a major pollutant group, can be more controlled with more positive change occurring.
Protection on High Ground Level Ozone Days
Reducing exposure to ground level ozone on days with an AQI greater than 100 cab be achieved by avoiding prolonged exertion outdoors and avoiding heavy exertion outdoors.
Long term ozone action plan
Possible long term solutions to reduce ground level ozone concentrations include Use alternative-fuel vehicles, such as natural gas and hybrid electric, including the possibility of some communities even expanded its line of buses, garbage trucks and even company vehicles, such as UPS trucks, to use alternative fuels. The use of environmentally friendly products, such as reduced volatile organic compounds (VOCs) for paint 
Store and dispose of chemicals correctly
Proper storage and disposal of chemicals can reduce pollutuion. Local groups have chemical round ups. Some waste companies also have disposal options, such as Waste Management. Proper disposal of fridge and air conditioners that contain chemicals. Some energy companies will even pay to take them. For example, Xcel Energy has $50 rebates. 
-  Archived September 29, 2006, at the Wayback Machine
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- Finley, Bruce. "Denver Ranks 8th Most-polluted Due to Ozone Contamination of Air." The Denver Post. The Denver Post, 22 Apr. 2016. Web. 25 Oct. 2016.
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- Bell, Michelle L., and Francesca Dominici. "Effect modification by community characteristics on the short-term effects of ozone exposure and mortality in 98 US communities." American journal of epidemiology 167.8 (2008): 986-997.
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- Smart Communities Network website listing strategies, state ordinances, additional articles and resources
- Vast link page to various worldwide sites on general air pollution, pollution monitoring, and the environment - courtesy Louisville (KY) Metro Air Pollution Control District
- Tulsa's Ozone Alert Oklahoma pollution gallery, alerts, and information
- Ozone Prevention success stories - Georgia-based website