In the United States, the Environmental Protection Agency (EPA) has developed an Air Quality Index, also known as the AQI, which is used to report daily air quality conditions. It is a tool used by various agencies to provide the public with timely and easy-to-understand information on local air quality and whether air pollution levels pose a health concern.
Increases in air pollution have been linked to decreases in lung function and increases in heart attacks. The AQI tells the public how clean the air is and whether or not they should be concerned for their health. It is focused on health effects that can happen within a few hours or days after breathing polluted air based on the presence of several pollutants. These include ground-level ozone, particulate pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide.
To make it easy to understand, the AQI is divided into six levels of health concern. An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level the EPA has set to protect public health. The higher the AQI value, the greater the level of air pollution and the greater the health concern.
Each of the six AQI categories corresponds to a different level of health concern. They include the following:
• Good – The AQI value for the community is between 0 and 50. Air quality is satisfactory and poses little or no health risk.
• Moderate – The AQI is between 51 and 100. Air quality is acceptable; however, pollution in this range may pose a moderate health concern for a very small number of individuals.
• Unhealthy for Sensitive Groups – When AQI values are between 101 and 150, members of sensitive groups may experience health effects, but the general public is unlikely to be affected.
• Unhealthy – Everyone may begin to experience health effects when AQI values are between 151 and 200. Members of sensitive groups may experience more serious health effects.
• Very Unhealthy – AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects.
• Hazardous – AQI values over 300 trigger health warnings of emergency conditions. The entire population is even more likely to be affected by serious health effects.