The U.S. EPA Air Quality Index

The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health concerns you should be aware of. The AQI focuses on health effects that can happen within a few hours or days after breathing polluted air. EPA uses the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect against harmful health effects.

 

	PURPLE – Very Unhealthy	Everyone, especially children and seniors, should limit outdoor exertion. People with respiratory disease should avoid and limit outdoor exposure.	200
	RED – Unhealthy	Everyone, especially children and seniors, should limit prolonged outdoor exertion. People with respiratory disease should avoid prolonged outdoor exertion	150
	ORANGE – Unhealthy for Sensitive Groups	Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion.	100
	YELLOW – Moderate	Unusually sensitive people should limit prolonged outdoor exertion.	50
	GREEN – Good	No health impacts are expected within this range.	0
For daily air quality updates, register with the Harris County Office of Emergency Management at www.hcoem.org or call the City of Houston at 713-640-4358.

Each category corresponds to a different level of health concern. For example, when the AQI for a pollutant is between 51 and 100, the health concern is “Moderate.” Here are the six levels of health concern and what they mean:

• Good - The AQI value for your community is between 0 and 50. Air quality is considered satisfactory and air pollution poses little or no risk.
• Moderate - The AQI for your community is between 51 and 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of individuals. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.
• Unhealthy for Sensitive Groups - Certain groups of people are particularly sensitive to the harmful effects of certain air pollutants. This means they are likely to be affected at lower levels than the general public. For example, children and adults who are active outdoors and people with respiratory disease are at greater risk from exposure to ozone, while people with heart disease are at greater risk from carbon monoxide. Some people may be sensitive to more than one pollutant. When AQI values are between 101 and 150, members of sensitive groups may experience health effects. The general public is not likely to be affected when the AQI is in this range.
• Unhealthy - AQI values are between 151 and 200. Everyone may begin to experience health effects. 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.

For more information about the AQI visit http://oaspub.epa.gov/airnow/aqibroch/