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What is it? -

The Air Quality Index (AQI) is a crucial tool for understanding outdoor air safety. Complex air pollution data is condensed into a single number that indicates how polluted the air in an area is. The higher the number, the worse the air.

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The menace of PM2.5 particles -

PM2.5 refers to fine particles in the air, so small that they bypass the body’s defenses to enter the lungs and bloodstream. These particles, which are 30 times smaller than the width of a human hair, have been linked to inflammation, respiratory distress, heart disease, and even mental health conditions.

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Global mobility -

PM2.5 is able to travel thousands of miles on wind currents, capable of crossing continents in days. Whether it originates from vehicle emissions, industrial processes, or even distant wildfires, its wide-ranging effects demand vigilance and proactive measures across demographics.

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Protector and pollutant - On some days, people might see a haze settled across a city. That haze is made up of particulate matter and ozone. In the stratosphere, ozone shields us from ultraviolet radiation, but at the ground level it’s a harmful pollutant. Exposure can lead to respiratory irritation and tissue damage.

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Why does it matter? -

The AQI offers insights into outdoor air quality and potential health risks. Much like monitoring the weather, regularly checking AQI levels ensures timely precautions, particularly during periods of heightened pollution.

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More than one index -

Different countries use their own unique indices to measure air quality. These usually correspond to their particular standards of national air quality. Canada, for example, uses the Air Quality Health Index, while Singapore utilizes the Pollutant Standards Index.

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The European Air Quality Index -

Europe’s AQI integrates data from multiple countries under the European Environment Agency. It monitors pollutants like nitrogen dioxide, sulfur dioxide, and particulate matter, aiming to harmonize air quality reporting across diverse geographic and industrial landscapes.

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Australian wilderness -

Australia’s AQI reflects local environmental challenges such as bushfires and dust storms. It measures six pollutants (compared to five measured in the US) and categorizes air quality from “Good” to “Hazardous.”

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India’s national index -

India’s National Air Quality Index (NAQI) uses an eight-pollutant system and is designed to address pollution from industrial activities, vehicle emissions, and agricultural practices like crop burning. The country is ranked as the third most-polluted in the world.

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The governing agency -

In the United States, the AQI is set by the Environmental Protection Agency (EPA). The EPA's mission is to protect the environment along with human health. The agency conducts environmental research on a constant basis to ensure that environmental laws are enforced.

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How AQI is measured -

To generate the AQI, the EPA gathers data from more than 5,000 air monitors across the US. Typically, they provide two separate AQIs–one for particulate matter, and the other for ozone. Whichever pollutant is higher should always be the one that people focus on.

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What are the levels of air quality? -

The EPA divides the AQI into six categories, ranging in color from green (safe) to maroon (hazardous). This scale guides people in adjusting activities, particularly for sensitive groups. Consulting these measurements can help avoid unnecessary exposure during unhealthy air conditions.

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Green (0–50) -

If an area's AQI sits between 0 and 50, there is good air quality. It’s considered safe for everyone, with no health risks expected. In this case, outdoor activities can proceed as usual.

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Yellow (51–100) -

AQI levels between 51 and 100 are moderate, which means air quality is generally acceptable. However, sensitive groups, such as those with respiratory or heart conditions, may experience slight discomfort with prolonged outdoor activity.

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Orange (101–150) -

When the AQI reaches 101 to 150, air quality poses a risk for sensitive individuals. Children, seniors, and those with preexisting health conditions should limit strenuous outdoor activities, while others can proceed with minor precautions.

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Red (151–200) -

At an AQI of 151 to 200, air quality is unhealthy for all. Sensitive groups should avoid outdoor exertion. The general population should reduce outdoor activities to minimize potential health risks.

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Purple (201–300) -

An AQI between 201 and 300 is reserved for very unhealthy air, warranting action for all groups. Everyone is advised to move activities indoors. Those with health sensitivities should take extra precautions to avoid exposure entirely.

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Maroon (301 and above) -

When an AQI exceeds 300, air quality is hazardous for everyone. Outdoor activities should be avoided entirely. Vulnerable groups should remain indoors with air filtration systems in place to reduce exposure to harmful pollutants.

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Symptoms -

If pollution levels climb in any given area, doctors have urged people to monitor potential symptoms. These include shortness of breath, chest tightness, and coughing, although less obvious symptoms like fatigue, throat irritation, or headaches also warrant attention.

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Special considerations for children -

Children are especially vulnerable to air pollution due to rapid lung growth and faster breathing rates. Monitoring AQI and limiting exposure during developmental years is critical to preventing long-term respiratory and cardiovascular health issues.

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Pregnancy -

Pregnant individuals are also sensitive to pollution, which can affect both their health and fetal development. Using the AQI as a guide, they can take proactive measures to limit exposure and ensure safer environments for their unborn child.

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Managing asthma - People with asthma should have a personalized action plan prepared for high-AQI days. By identifying trigger levels and having medications ready, they can ensure that they are able to respond effectively to any symptoms that may arise from pollution.

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Reducing outdoor exposure -

Cutting outdoor activity time or intensity reduces pollution dosage. For instance, a 15-minute walk instead of 30 minutes can halve exposure. Wearing an N95 mask during high-AQI days further protects against unseen pollutants. Cloth masks have no effect against PM2.5.

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When is pollution at its worst? -

Ozone pollution peaks during warmer months, typically in late afternoons, when sunlight fuels chemical reactions. Understanding these patterns helps in planning outdoor activities during safer times (such as mornings) to avoid prolonged exposure.

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Wildfires -

Wildfires also significantly increase PM2.5 levels, especially during late summer and fall. Staying informed through AQI updates during wildfire season allows for timely action that can protect respiratory health.

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Pollution spikes from daily activities -

Events like barbecues or fireworks temporarily elevate PM2.5 concentrations in certain areas. By raising awareness of these pollution sources, people could potentially plan around them to ensure better air quality in personal spaces.

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Indoor air safety measures -

Staying indoors provides some relief from outdoor air pollution, but additional measures can enhance protection, like using proper ventilation or even an air filtration system.

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The success of air regulations -

Over the last 40 years, stricter environmental regulations have significantly improved air quality around the globe. Cleaner vehicles, power plants, and industrial practices prove that deliberate policy choices can lead to healthier environments.

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Tools for monitoring air quality -

Around the world, there are various resources that can be used to monitor air quality. Between cell phone apps and online websites, many localized places provide detailed information pertaining to air quality, allowing people to make decisions based on current conditions.

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Air quality and the next generation -

Ensuring clean air for children is a societal responsibility. By addressing pollution sources today, we can provide a healthier environment for future generations and foster both their physical and cognitive development.

Sources: (Vox) (IQAir) (European Air Quality Index) (Britannica)

See also: How air pollution is interfering with bee pollination

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