Understanding Air Quality: Pollution Index Explained

The Air Quality Index (AQI) is a tool used to communicate the level of outdoor air pollution and its potential health effects. The AQI is based on measurements of six major air pollutants: ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and two sizes of particulate matter (PM2.5 and PM10). These measurements are taken daily and assigned a number on a scale from 0 to 500, with higher values indicating increased levels of air pollution and associated health risks. Each AQI value is colour-coded, ranging from good air quality (below 50) to hazardous air quality (above 300). The AQI is an essential resource for individuals to protect themselves from the harmful effects of air pollution, especially those who are more vulnerable, such as children, the elderly, and people with pre-existing health conditions.

How is the Air Quality Index (AQI) calculated?

The Air Quality Index (AQI) is a representation of air pollution concentration levels. It is a simple and uniform way to communicate about outdoor air quality and health, with higher AQI values indicating greater levels of air pollution and health concerns. The AQI is calculated by converting measured pollutant concentrations to a uniform index based on the health effects associated with a particular pollutant. The United States Environmental Protection Agency (EPA) has established the National Ambient Air Quality Standards (NAAQS) for each pollutant to protect public health.

The AQI includes measures for six major air pollutants: ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and two sizes of particulate matter (PM10 and PM2.5). Each of these pollutants has a separate index value, and the overall index is defined as the maximum value of the index. The AQI is calculated either per hour or per 24 hours, with the final AQI value being the maximum of these six scores. The score for each pollutant is non-linear, as is the final score. For example, an AQI of 300 does not mean twice the pollution of an AQI of 150, nor does it indicate that the air is twice as harmful.

The AQI is divided into six color-coded categories, each indicating increasing levels of health concern. These categories include Good, Satisfactory, Moderate, Poor, Severe, and Hazardous. An AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality. When the AQI value is at or below 100, it is generally considered satisfactory. However, when the AQI value exceeds 100, the air quality is considered unhealthy, initially for certain sensitive groups and then for everyone as the values continue to rise.

The AQI forecasts are influenced by factors such as temperature, precipitation, wind, and cloud cover, which impact the creation and transport of pollution. While the AQI provides valuable information about air pollution and health, it does not account for factors like temperature or pollen levels, which may increase sensitivity to air pollutants. Additionally, the definition and calculation of the AQI can vary between nations, reflecting the discourse surrounding national air quality standards in each country.

What are the AQI bands and their associated health advice?

The Air Quality Index (AQI) is a system used to warn the public about dangerous levels of air pollution. It is an indicator developed by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. The AQI is divided into six categories, each corresponding to a different level of health concern. The higher the AQI value, the greater the level of pollution and the greater the health concern.

The six AQI bands are:

• Low risk: AQI values at or below 100 are considered satisfactory for almost everyone.
• Moderate risk: When AQI values are above 100, air quality is unhealthy.
• High risk: No specific AQI value is mentioned, but this level indicates a further increase in pollution levels and associated health risks.
• Very high risk: No specific AQI value is mentioned, but this level indicates a significant increase in pollution levels and associated health risks.
• Emergency: When the AQI indicates that acute exposure may cause significant harm to public health, agencies may invoke emergency plans that require major emitters to curtail emissions.
• Hazardous: On rare occasions, the amount of air pollution can be abnormally high, resulting in an AQI value that exceeds the maximum of 500, which poses an immediate danger to public health.

The specific health advice associated with each AQI band varies based on the sensitivity of individuals to air pollution. Some general recommendations include:

• For people with asthma or other respiratory conditions, the AQI can guide decisions on adjusting activity levels, particularly outdoors, to reduce exposure to air pollution.
• During periods of high AQI, it is recommended to reduce physical activity outdoors or even avoid going out altogether, especially for children, the elderly, and those with respiratory or cardiovascular issues.
• When wildfires contribute to high AQI levels, the use of masks (e.g., N95 respirators) outdoors and air purifiers with HEPA and activated carbon filters indoors is advised.
• Checking the AQI daily can help individuals understand their sensitivity to air pollution and take appropriate protective measures.

How does the AQI impact human health?

The Air Quality Index (AQI) is a tool used by government agencies to measure and communicate the level of air pollution and its associated health risks. The AQI value rises with increasing air pollution, with higher values indicating greater health concerns. An AQI value of 50 or below represents good air quality, while a value over 300 indicates hazardous air quality.

The impact of air pollution on human health can vary depending on factors such as the concentration and duration of exposure, individual susceptibility, age, location, and underlying health conditions. Prolonged exposure to elevated levels of air pollution can have significant negative consequences for human health, including:

Respiratory Issues

Air pollution can irritate and inflame the respiratory system, leading to chronic coughing, wheezing, throat discomfort, and reduced lung function. Fine particulate matter can penetrate deep into the lungs and even enter the bloodstream, causing or exacerbating respiratory conditions such as asthma, bronchitis, and chronic obstructive pulmonary disease (COPD).

Cardiovascular Diseases

Long-term exposure to air pollution has been linked to an increased risk of cardiovascular diseases, including heart attacks and strokes. Air pollutants can enter the bloodstream and contribute to systemic inflammation, affecting the heart and other organs.

Cancer

Air pollution has been associated with an increased risk of lung cancer, and possibly other types of cancer. Certain pollutants, such as radon and tobacco smoke, are known carcinogens.

Adverse Birth Outcomes

Maternal exposure to air pollution has been linked to adverse birth outcomes, including low birth weight, pre-term birth, and small gestational age births.

Neurological Development

There is growing evidence to suggest that air pollution may impact neurological development in children and increase the risk of diabetes.

It is important to note that the health risks associated with air pollution are not limited to outdoor exposure. Indoor air pollution, from sources such as radon, smoke, lead dust, carbon monoxide, and volatile organic compounds, can also have significant impacts on human health. Checking the AQI daily and taking precautionary measures can help reduce exposure and mitigate potential health risks.

How to protect yourself from unhealthy levels of air pollution?

The Air Quality Index (AQI) is a tool used to communicate about outdoor air quality and health. It is a rating system that shows the severity of pollution in the air on a scale 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 a value over 300 represents hazardous air quality. AQI values at or below 100 are generally considered satisfactory, but it's important to pay attention to how you feel and take protective measures whenever needed.

• Stay informed about the AQI in your area: Check the daily air pollution forecasts in your community. Sources of this information include local radio and TV weather reports, newspapers, and online platforms such as AirNow, which provides real-time air pollution data for over 80 countries.
• Limit outdoor activities when pollution levels are high: Avoid exercising outdoors or reduce the intensity of your outdoor activities. This is especially important for children and individuals who are elderly, pregnant, or have underlying health conditions.
• Wear a mask: When you must go outdoors, consider wearing a mask that provides adequate protection against particle pollution, such as an N95 or P100 respirator.
• Improve indoor air quality: Take steps to ensure the air you breathe indoors is clean. This may include using air purifiers with high clean air delivery rates (CADR) and regularly replacing filters in air conditioners and purifiers.
• Reduce energy use: Lower your energy consumption at home by opting for energy-efficient appliances and renewable energy sources. Generating electricity and using certain energy sources contribute to air pollution.
• Support clean air initiatives: Get involved in efforts to improve air quality and reduce pollution. This can include advocating for renewable energy policies, participating in campaigns for cleaner air, and supporting the transition to cleaner forms of transportation, such as electric buses.

By staying informed, adjusting outdoor activities, improving indoor air quality, reducing energy consumption, and actively supporting clean air initiatives, you can take proactive measures to protect yourself and your loved ones from the potential health risks associated with unhealthy levels of air pollution.

What are the tools to monitor real-time air quality?

Air pollution indices (or air quality indices, AQIs) are based on measurements of various pollutants in the air, including particulate matter (PM2.5 and PM10), Ozone (O3), Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2), and Carbon Monoxide (CO) emissions. These measurements are taken in real-time using a variety of tools and methods, which I will outline below.

One method of monitoring air quality is through the use of sensors and monitoring stations. Companies like PurpleAir and Aeroqual design and deliver integrated sensors that measure particulate pollution, temperature, humidity, and pressure in real-time. These sensors are often placed in monitoring stations or integrated into handheld, portable devices that can be used to measure air quality in different locations. The data from these sensors is then used to create real-time air pollution maps, such as the one provided by the World Air Quality Index project, which covers over 80 countries.

Another tool for monitoring real-time air quality is through the use of mobile applications. The Environmental Protection Agency's (EPA) AirNow app provides air quality readings for almost every corner of the US and offers advance notice of upcoming air quality problems. This app measures seven air quality factors, including CO2, PM2.5, VOCs (volatile organic compounds), and radon. Other apps may also provide similar information, although some simply repackage data from EPA stations without adding much value.

In addition to sensors and apps, there are also more advanced technologies being used for air quality monitoring, such as drones. For example, Prana Air offers a smart city project that utilizes drones, outdoor air purifiers, and data dashboards to improve air quality monitoring and management in urban areas.

These tools and technologies provide valuable data and insights that can help individuals, communities, and organizations make informed decisions to protect human health and the environment from the harmful effects of air pollution.

Frequently asked questions