Air Quality Alert: Unhealthy Air And You

The Air Quality Index (AQI) is a tool for reporting daily air quality. It tells you how clean or polluted your air is and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days of breathing polluted air. The AQI includes six color-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. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality. When air quality is in the unhealthy range, everyone who is active outdoors may experience effects. Members of sensitive groups are likely to experience more serious effects.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a tool used by the EPA to communicate about outdoor air quality and health. The AQI is a yardstick that runs from 0 to 500, with higher values indicating greater levels of air pollution and health concerns. An AQI value of 50 or below represents good air quality, while a value over 300 indicates hazardous air quality. The AQI is divided into six color-coded categories, each corresponding to a different level of health concern.

The six categories of the AQI are:

• Good: AQI values from 0 to 50 fall into the "good" category, indicating satisfactory air quality and low health risk.
• Moderate: AQI values from 51 to 100 are considered "moderate." While most individuals can tolerate this air quality, some unusually sensitive people may experience health effects, such as those with medical conditions or inherent susceptibility.
• Unhealthy for Sensitive Groups: AQI values from 101 to 150 fall into this category. People with sensitivities, including those with lung diseases or active outdoors, may experience adverse health effects.
• Unhealthy: AQI values from 151 to 200 are considered "unhealthy." Any individual active outdoors may be affected, and members of sensitive groups may experience more severe health impacts.
• Very Unhealthy: AQI values from 201 to 300 indicate "very unhealthy" air quality. At this level, widespread effects are expected among the general population, with more serious consequences for sensitive groups.
• Hazardous: AQI values above 300 represent hazardous air quality, posing significant health risks to the entire population.

The AQI is based on the measurement of several key pollutants, including particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO) emissions. These measurements are taken hourly, providing real-time data for assessing air quality and potential health risks.

Outdoor physical activity

The Air Quality Index (AQI) is a helpful tool to determine whether it's safe to exercise outdoors. The AQI runs from 0 to 500, with higher numbers indicating greater levels of air pollution and health concerns. When the AQI exceeds 100, it's recommended to exercise indoors or limit prolonged and heavy outdoor activity, especially for sensitive groups. Those with pre-existing respiratory or cardiovascular conditions may experience intensified negative impacts of air pollution even during low-intensity activities, so it's important to be cautious.

If you're planning a long run or strenuous hike, check the air quality forecast beforehand. If it's a code orange, consider exercising in the morning when the air quality tends to be better, or opt for a lighter activity. For code red or higher, it's best to move your exercise routine indoors. Additionally, certain times of the day and types of pollutants can impact your exposure to unhealthy air. Summertime, for example, is prime weather for ozone (smog), with higher levels typically in the afternoon.

While it's always exciting to enjoy the outdoors, especially during favourable weather conditions, air pollution can pose serious health risks. Therefore, it's crucial to stay informed about air quality and take necessary precautions to ensure your safety during outdoor physical activity.

Sensitive groups

The Air Quality Index (AQI) is a tool for reporting daily air quality. It tells us how clean or polluted the air is and what associated health effects might be a concern for us. The AQI focuses on health effects that may be experienced within a few hours or days after breathing polluted air. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

When the AQI is in the "Moderate" range (51-100), the air quality is acceptable. However, there may be some health concerns for unusually sensitive individuals. While specific groups of people at greater risk cannot be identified, studies indicate that some individuals experience health effects at moderate levels of outdoor exertion or lower ozone levels than the average person. These individuals may experience effects when the air quality is in the moderate range.

When the AQI is in the "Unhealthy for Sensitive Groups" range (101-150), people in sensitive groups may experience health effects when engaged in outdoor activities. For particle pollution, the sensitive groups include people with heart and lung disease, older adults, children, people with diabetes, and people of lower socioeconomic status. People with lung diseases are included in this group because they often have poorer lung function, and any additional reduction is more likely to result in symptoms. Ozone can also aggravate their underlying diseases. For ozone, the sensitive group also includes children and adults who are active outdoors because they are more likely to be at elevated ventilation rates for long periods when ozone levels are high.

When the AQI is in the "Very Unhealthy" range (201-300), there will be widespread effects among the general population and more serious effects in members of sensitive groups.

You can find air quality forecasts and real-time air quality information on the EPA's AirNow website and mobile app. Local media, such as newspapers, television, and radio, also provide air quality reports, usually with the weather forecast.

Health concerns

The Air Quality Index (AQI) is a tool used to communicate about outdoor air quality and health. The higher the AQI value, the greater the level of air pollution and the more serious the health concern. An AQI value of 50 or below represents good air quality, while an AQI value over 300 is hazardous.

When air quality is moderate (51-100 AQI), the air quality is acceptable, but there may be some health concerns for unusually sensitive individuals. Controlled human exposure studies indicate that some individuals experience health effects at these levels, and they may experience effects when air quality is in the moderate range.

When the AQI is between 101 and 150, the air is considered unhealthy for sensitive groups, including the elderly, children, and people with lung or heart disease. These groups should reduce their outdoor exertion. When the AQI reaches 151-200, the air is considered unhealthy for everyone, with sensitive groups experiencing more serious effects.

At AQI levels of 201-300, the air is very unhealthy, and children, asthmatics, and people with heart or lung conditions should avoid the outdoors. All others should reduce their outdoor exertion.

Ozone, or smog, is one of the least-controlled and most dangerous pollutants in the United States. It is invisible, and it can cause serious health issues, especially for those who are active outdoors, including children and adults, as well as those with lung diseases. Wildfires, flooding, hurricanes, and other natural events can also create unhealthy air, and the cleanup can add to the challenge. Climate change poses grave health threats to everyone, with serious risks to lung health.

Media reports

The primary contributors to declining air quality are human-driven climate change, wildfire smoke, and other climate-influenced factors. The report underscores the urgent need to address both carbon emissions and stringent air pollution regulations simultaneously. Fine particles from pollution sources can infiltrate people's lungs and enter the bloodstream, leading to various health risks.

The Air Quality Index (AQI), a tool used by the EPA to communicate about outdoor air quality and health, provides a yardstick for measuring air pollution levels. Values on the AQI range from 0 to 500, with higher values indicating greater air pollution and health concerns. Values above 300 represent hazardous air quality, while lower values of 50 or below signify good air quality.

Media outlets have also highlighted the disproportionate impact of unhealthy air on communities of color. Research has shown that these communities are more exposed to poor air quality and are more likely to suffer from chronic conditions that increase their vulnerability to air pollution, such as asthma, diabetes, and heart disease. The "State of the Air" report in 2025 noted a shift in the geographic distribution of air pollution, with the East Coast experiencing a resurgence of air quality issues due to a deadly heatwave in Texas and wildfires in Canada.

Frequently asked questions