You’ve heard about red, orange, yellow and green days: What do all the colors have to do with ozone and what do they mean for us?
What is ozone?
Ozone is a chemical compound (O3) that occurs as a gas in two areas of the Earth’s atmosphere.
What is the difference between ground-level ozone and the ozone layer?
The ozone layer occurs in the stratosphere, about 10 miles above sea level (for comparison, Kansas City is less than one-fifth of a mile above sea level, about 800 feet in elevation) and stretches around the entire planet. This region contains 90 percent of earth’s ozone and essentially acts as a filter in two ways: 1) by absorbing ultraviolet sunlight (UV-B) before it reaches earth’s surface, thus reducing peoples’ exposure to damaging rays and 2) by keeping the sun’s heat in the stratosphere, which helps keep the planet’s surface temperature cooler.
Source: NOAA Office of Oceanic and Atmospheric Research
Ground-level ozone, which is the exact same chemical compound as ozone in the stratosphere, is found in the troposphere (sea level to about seven miles above). It is a product of chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC).
What causes changes in the amount of ground-level ozone?
Source: US EPA airnow.gov
According to Mid-America Regional Council (MARC), the processes at coal-burning industrial plants and chemical plants increase ground-level ozone, but “more than half of all ozone pollution is caused by everyday people doing everyday things.” The chemical reactions involved in driving internal-combustion powered vehicles and using gas-powered mowers contribute to ground-level ozone. Even fueling a vehicle can release fumes that increases ozone pollution.
How does it affect me?
Ozone is an unstable compound and is highly reactive with other compounds, such as the ones that make up living tissues. Ground level ozone can harm trees, crops, birds and all types of living things. In humans, ozone irritates the lungs and inhibits the respiratory system.
How will I know what my local air quality conditions are?
Source: US EPA airnow.gov
Besides ground-level ozone, particle pollution (particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide are other air pollutants that can affect health. These five pollutants are monitored by the EPA and used to calculate the Air Quality Index, a scale of 0-500 rating the quality of the air. MARC issues a Skycast for the region each day based on the Air Quality Index, with the colors representing quality of the air and a specific set of recommendations on how to protect your health and our air (see the table from MARC below).
| SkyCast | Air Quality | AQI Value | Protect Your Health | AirQ Actions |
| Good | Green (Healthy) | 0–50 | No health impacts expected. | Everyday actions |
| Moderate | Yellow (Elevated ozone concentrations) | 51–100 | Sensitive people, such as those with respiratory ailments or allergies, should consider limiting prolonged outdoor exertion. | Everyday actions |
| Unhealthy for sensitive groups | Orange (Ozone Alert) | 101–150 | Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion. | Ozone Alert actions |
| Unhealthy | Red (Ozone Alert) | 151–200 | Active children and adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else, especially children, should limit prolonged outdoor exertion. | Ozone Alert actions |
