Air Quality Index: Understanding The Types Of Air Pollution

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. It was established by the Environmental Protection Agency (EPA) and measures six major air pollutants: ozone, particle pollution, carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate matter. The AQI is calculated using health-based national air quality standards and the latest scientific information. Measurements are taken daily and reported on an hourly basis, with each AQI value corresponding to a specific colour-coded category to indicate the level of health concern. The AQI is an essential tool for individuals to understand the air quality in their local area and take necessary precautions to protect their health.

Ozone

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. The AQI is used to track ozone (smog) and particle pollution, as well as four other widespread air pollutants. The AQI is measured on a scale of 0 to 500, with 0 representing perfect air quality and 500 representing air pollution levels that pose an immediate danger to the public.

The AQI for ozone is calculated based on the maximum 8-hour average ozone concentration in a 24-hour period. This is because the health effects of ozone exposure are cumulative and can build up over several hours. Prolonged exposure to high levels of ozone can be harmful, particularly for sensitive groups such as children, the elderly, and people with respiratory conditions.

To protect public health, the Environmental Protection Agency (EPA) has set national air quality standards for ozone. These standards aim to limit the concentration of ozone in the ambient air to levels that are considered safe for humans and the environment. When ozone levels exceed these standards, the AQI value rises, indicating that the air quality is unhealthy.

By monitoring the AQI for ozone, individuals can take steps to protect themselves from the harmful effects of ozone pollution. On days when ozone levels are high, people are advised to limit their time outdoors, avoid strenuous activities, and stay away from high-traffic areas. Real-time ozone AQI data is available through various sources, including websites, mobile apps, and interactive maps, allowing individuals to stay informed and take necessary precautions.

Particle pollution

Fine particles, or particulate matter 2.5 (PM2.5), are of particular concern. These particles are 2.5 microns or less in width and can infiltrate deep into the respiratory tract, reaching the lungs. Short-term exposure to high levels of PM2.5 can trigger cardiovascular events, hospitalisations, and even mortality. Long-term exposure can increase the risk of strokes, coronary heart disease, and premature death. It is also associated with respiratory issues, asthma, and reduced lung function.

Nitrogen dioxide

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. The AQI is divided into six colour-coded categories, each representing a range of index values. The higher the AQI value, the greater the level of air pollution and the greater the health risk.

NO2 is one of six widespread air pollutants for which there are national air quality standards to limit their levels in the outdoor air. It is primarily generated during fossil fuel combustion, so thermal power plants, industrial sites, and automobiles are the dominant sources. Trucks, buses, and cars are the largest sources of NO2 emissions, followed by diesel-powered non-road equipment and industrial processes.

Monitors show the highest concentrations of outdoor NO2 in large urban regions, with levels higher on or near heavily travelled roadways. Levels of NO2 are also higher indoors when fuels like wood or gas are burned, and in homes with smokers. Exposure to NO2 has been linked to a range of harmful effects on the lungs, including an increased likelihood of hospital admissions and a greater risk of developing asthma in children.

Efforts to improve air quality have led to a decrease in NO2 emissions in recent years. More protective standards under the federal Clean Air Act, as well as state and federal regulations to reduce NOx emissions, have helped drive down nitrogen dioxide emissions from power plants and vehicles.

Sulfur dioxide

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. It is a tool for communicating about outdoor air quality and health. The AQI is divided into six colour-coded categories, each corresponding to a range of index values. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

The 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 considered satisfactory for almost everyone. When AQI values are above 100, air quality is considered unhealthy, first for certain sensitive groups of people, and then for everyone as AQI values increase.

For example, on a code orange day, which indicates an AQI value between 101 and 150, people with health issues such as asthma, lung disease, diabetes, or cardiovascular disease, as well as children, teens, pregnant women, and the elderly, are advised to avoid long periods of outdoor activity and to stay away from high-traffic areas. On purple or maroon days, which indicate AQI values over 300, the air quality is considered hazardous, and everyone is advised to stay indoors as much as possible.

Carbon monoxide

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. It is based on the measurement of six atmospheric pollutants:

• Particulate matter (PM2.5 and PM10)
• Ozone (O3)
• Nitrogen Dioxide (NO2)
• Sulfur Dioxide (SO2)
• Carbon Monoxide (CO)
• Particle pollution (tiny particles from smoke, power plants, factories, vehicle exhaust, and other sources)

The AQI for carbon monoxide is typically calculated using hourly readings from monitoring stations. An AQI value of 100 generally corresponds to the level of the National Ambient Air Quality Standards (NAAQS) for carbon monoxide, which is set by the Environmental Protection Agency (EPA) in the United States. Values below 100 are considered satisfactory for almost everyone, while values above 100 indicate unhealthy air quality.

As the AQI for carbon monoxide increases, so does the potential for adverse health effects. Carbon monoxide is dangerous because it binds to hemoglobin in the blood, forming carboxyhemoglobin, which prevents oxygen from being transported throughout the body. High levels of carbon monoxide in the air can lead to carbon monoxide poisoning, which can be life-threatening. Symptoms of carbon monoxide poisoning include headaches, dizziness, weakness, nausea, and confusion. Prolonged exposure to elevated levels of carbon monoxide can have serious long-term effects on cardiovascular and neurological health.

To protect public health, the EPA and other governmental bodies provide guidance and recommendations when the AQI for carbon monoxide reaches unhealthy levels. This may include encouraging people to reduce physical activity outdoors, avoid spending extended periods near high-traffic areas, or in some cases, even recommending that individuals stay indoors altogether.

Frequently asked questions