Why is Air Quality Important?
Local air quality affects how you live and breathe. Like the weather, it can change from day to day or even hour to hour. A key tool in this effort is the Air Quality Index, or AQI.
What is the U.S. Air Quality Index (AQI)?
The U.S. AQI is EPA’s index for reporting air quality. The AQI can provide simple information about your local air quality, how unhealthy air may affect you, and how you can protect your health.
How does the AQI work?
Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality.
For each pollutant an AQI value of 100 generally corresponds to an ambient air concentration that equals the level of the short-term national ambient air quality standard for protection of public health. AQI values at or below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is unhealthy: at first for certain sensitive groups of people, then for everyone as AQI values get higher.
What are the AQI categories?
The AQI is divided into six categories. Each category corresponds to a different level of health concern. Each category also has a specific color. The color makes it easy for people to quickly determine whether air quality is reaching unhealthy levels in their communities.
Categories are Green, Yellow, Orange, Red, Purple and Maroon.
What are the five major air pollutants?
EPA establishes an AQI for five major air pollutants regulated by the Clean Air Act. Each of these pollutants has a national air quality standard set by EPA to protect public health:
- ground-level ozone
- particle pollution (also known as particulate matter, including PM2.5 and PM10)
- carbon monoxide
- sulfur dioxide
- nitrogen dioxide
How Does the PurpleAir Sensor Map work?
Guide to Understand the Air Quality Sensor Map
What is the difference between ozone and particulate matter?
Ozone is a gas found in the air we breathe and depending on where it occurs. Good ozone is present naturally in the Earth’s upper atmosphere. Bad ozone forms near the ground when pollutants (emitted by sources such as cars, power plants, industrial boilers, refineries, and chemical plants) react chemically in sunlight. Ozone pollution is more likely to form in warmer months.
Particulate matter consists of a mixture of solids and liquid droplets. Some particles are emitted directly; others form when pollutants emitted by various sources react in the atmosphere. Particle pollution levels can be very unhealthy and even hazardous during events such as forest fires. Particle levels can be elevated indoors, especially when outdoor particle levels are high.
Fine particles are 2.5 micrometers or smaller, that are generated from motor vehicles, power plants, residential wood burning, forest fires, agricultural burning, some industrial processes, and other combustion processes. Large/Coarse particles are between 2.5 and 10 micrometers, are generated from crushing or grinding operations, and dust stirred up by vehicles traveling on roads.
What are the health impacts from ozone and particulate matter?
Health effects from Bad Ozone consists of:
- Respiratory System Irritation
- Reduced Lung Function
- Permanent Lung Damage
- Asthma
Health effects from Particulate Matter can consist of:
- Chest Pain
- Shortness of breath
- Fatigue
- Increase Susceptibility to Respiratory Infections
- Increased Emergency Room visits for Sensitive Populations