What Is AQI? A Guide to Air Quality Index

No, it is not the Spanish word for “here”. But if you really have no idea what AQI means, first, come out of whatever rock you’ve been living under, and second, read this blog carefully from the start to the end.

If you live in Delhi and suddenly you wake up to see a thick veil of smoke outside, congratulations! Winter is here. Nature is simply throwing back all the pollution you have subjected it to during the rest of the year. We know how powerless we are when nature flexes, so all we can do is measure its severity. Just like we have the Richter Scale for earthquakes, the AQI or Air Quality Index, is a measurement that tells you how deep a grave we’ve dug for ourselves.

Now, you might be thinking, “Yeah, my phone is saying AQI is high, but how does it know whether I need to go out or not?” Well, my friend, AQI does not judge the air of visibility. It takes note of six air pollutants in the index formula, including:

• PM 2.5: Droplets or particle matter that are smaller than or equal to 2.5 microns in width.

• PM 10: Particle matters of 10 microns or less in width.

• Carbon monoxide: An odourless and colourless, non-irritating gas that is called “the Silent Killer”, and for good reasons.

• Sulphur dioxide: A toxic gas that does not need too many steps to make sulphuric acid, the acid that melts metals.

• Nitrogen dioxide: Basically, Nitric Acid on wings. Just add water, and it's enough to burn through your car.

• Ground-level ozone: Let’s just say that it is not your best friend.

Think of the AQI scale as 0-500. As AQI increases, it slowly poses more of a risk. Even though AQI can be more than 500 and that denotes dangerous levels of air pollution. There are six categories into which AQI is divided, each representing a different level of health concern and marked by a specific colour. These colours allow people to identify if the air quality is approaching unhealthy levels easily.

1. Good

• AQI: 0-50

• PM2.5 (μg/m3): 0-9.0

• Green

• Good air quality ranges from 0 to 50 and it denotes little to no risk. If you see that your AQI is in this range in Delhi, check your network.

2. Moderate

• AQI: 51-100

• PM2.5 (μg/m3): 9.1-35.4

• Yellow

• 51-100 denotes moderate risk. To minimise respiratory risks, sensitive groups should significantly reduce outdoor exercise. Keep windows closed and avoid using outdoor air to ventilate indoor spaces to limit exposure to pollutants.

Note: Sensitive groups include children, the elderly, pregnant individuals, and those with heart or lung conditions.

3. Unhealthy for sensitive groups

• AQI: 101-150

• PM2.5 (μg/m3): 35.5-55.4

• Orange

101-150 is unhealthy for sensitive groups. When the air quality is unhealthy for sensitive groups, everyone may experience eye, skin, and throat irritation, along with respiratory issues, and outdoor exertion should be limited.

Sensitive groups face a higher health risk and should avoid outdoor activity entirely, possibly using an air pollution mask if outside is necessary. Ventilation is not recommended, and a high-performance air purifier should be used if indoor air quality is poor.

4. Unhealthy

• AQI: 151-200

• PM2.5 (μg/m3): 55.5-125.4

• Red

• An unhealthy AQI indicates a higher risk of heart and lung issues, with health effects more likely for everyone, especially sensitive groups.

• All individuals should avoid outdoor activities and consider wearing a pollution mask if going outside is necessary. Ventilation should be avoided, and air purifiers should be used indoors.

5. Very unhealthy

• AQI: 201-300

• PM2.5 (μg/m3): 125.5-225.4

• Purple

If you have cardiovascular ailments, don’t go out or stress yourself. If you have your air purifier, keep it on and pray for the number to go down.

6. Hazardous

• AQI: 301-500 or greater

• PM2.5 (μg/m3): 225.5 or greater

• Maroon

“Dilli ki sardi”. Everybody stay inside and do your best to “not breathe”. Anything you breath is going to be harmful.

AQI is a measure of air pollution levels and is indicative of the health risks associated with breathing in the polluted air.

1. Wheezing, coughing, and shortness of breath: If you expose yourself to high-levels of pollutants, your lungs will find it difficult to breathe. Due to that, shortness of breath, coughing, wheezing happens.

2. Respiratory issues: If you have breathing problems, exposure to polluted air can cause sudden bouts of respiratory illnesses.

3. Cardiovascular disease: If the air you are breathing is polluted to the core, your lungs and heart will pump polluted air. This is why air pollution increases the chances of heart attacks and strokes manifolds.

4. Developmental issues: Children's growth depends heavily on the air they breathe. Clean air increases immunity and lung capacity and aids children in their developmental phase. Polluted air, on the other hand, makes it all the more difficult for children to grow up.

5. Low infant birth weight: If mothers are exposed to highly polluted air, it affects the blood circulation and just as pollution affects development in children, it is no different for the foetus.

6. Premature death: if you can’t breathe, you can’t live. It's that simple.

AQI could be high during a combination of factors. However, it is surprising to note that there is some evidence that suggests that air pollution is, in fact, worse in winter. Let’s look into some of the facts that were posted by AccuWeather in 2020.

• In the summer, the air is lighter, so pollution is whisked away. But in winter, cold air stagnates over places, trapping pollutants and locking them in place.

• The advent of Winter in India coincides with the festive season. It means, more pollution from traffic, more pollution from fire crackers, more pollution all around!

AQI is not a measure that only doctors need to consider. It’s time we took our health into our own hands and proactively worked to avoid any health risks. With growing industrialisation and urbanisation, our AQI seems to be hitting a record high every day.

While we may not have a say in reducing it, we can take precautionary measures so we are not as severely impacted by it.