Pure air is at a premium today. Suppose you live in a city like Delhi. You could find that the atmosphere is hazy throughout the day. The prime reason for the haziness is air pollution.
At the same time, if you move towards the villages, you will find the air clearing up, and you will feel a noticeable difference in the quality of the air you breathe. No wonder Delhi ranks at the top of the list of the most polluted cities in the world.
The statistics can be terrifying. As of September 07, 2021 (18.30 IST), the top five most polluted cities in the world are Krasnoyarsk (Russia), Dubai (UAE), Kabul (Afghanistan), Lahore (Pakistan), and Lima (Peru). Delhi is sixth on the list with an AQI of 127, whereas the Russian city has 187. (Reference – https://www.iqair.com/world-air-quality-ranking)
What is AQI, and how does it determine the air pollution levels?
AQI represents Air Quality Index. It is a compilation of several statistics into one concrete index that we can relate to. It helps judge the quality of air at a particular place at a specific time.
Thus, AQI is a relative index that keeps changing by the minute. However, AQI shows how polluted the air is and the risks associated with each rating.
Therefore, how do you measure AQI and the health impact of a particular rating?
AQI is a complex calculation that considers several factors. Generally, AQI is a measure of impact caused by eight prominent pollutants. They include the following.
- Particulate Matter (PM10)
- Particulate Matter (PM2.5)
- Ozone (O3)
- Sulphur Dioxide (SO2)
- Nitrogen Dioxide (NO2)
- Carbon Monoxide (CO)
- Lead (Pb)
- Ammonia (NH3)
These eight pollutants account for almost all areas. For example, PM10 and PM2.5 are present almost everywhere, even inside our homes. O3 is primarily existent in coastal areas. Pb, SO2 and NO2 are generally industrial pollutants. Lead is also found in many manufactured products, including toys. The primary source of CO and Pb is vehicular pollution. NH3 is more prevalent in rural areas where there is abundant livestock.
Besides these eight common pollutants, there are many more, but they do not impact our health as much as these pollutants do. Now, one should also understand that a specific area will not include all the eight pollutants listed above at a particular time.
Therefore, overall AQI is measured only if data is available for a minimum of three pollutants, one of which should necessarily be PM10 or PM2.5. Secondly, it requires a minimum of 16 hours of data for calculating the sub-indices.
Based on all these calculations and statistics, India’s Central Pollution Control Board has formulated the different levels of AQI and classified them into different categories.
Here are the breakpoints for AQI Scale 0 to 500 – Units – µg/m3, generally unless otherwise mentioned.
|AQI Category (Range)||PM10 24-hr||PM2.5 24-hr||NO2 24-hr||O3 8-hr||CO 8-hr (mg/m3)||SO2 24-hr||NH3 24-hr||Pb 24-hr|
|Good (0 to 50)||0-50||0-30||0-40||0-50||0-1.0||0-40||0-200||0-0.5|
|Satisfactory (51 to 100)||51-100||31-60||41-80||51-100||1.1-2.0||41-80||201-400||0.6-1.0|
|Poor (201 to 300)||251-300||91-120||181-280||169-208||10.1-17||381-800||801-1200||2.1-3.0|
|Very Poor (301-400)||341-430||121-250||281-400||209-748||17.1-34||801-1600||1201-1800||3.1-3.5|
Source – Central Pollution Control Board
Based on the above qualifying standards, India ranks 3rd out of 106 countries in the world in 2020 (worst polluted to the least).
Here are the worst five countries on the list, along with their average AQI in 2020.
|Country||Average US AQI||Category|
|India||141||Unhealthy for Sensitive groups|
|Mongolia||128||Unhealthy for Sensitive groups|
|Afghanistan||128||Unhealthy for Sensitive groups|
Here is a list of the worst ten polluted cities in the world in 2020 (average AQI)
|City||2020 Average US AQI||Category|
|Hotan - China||110.2||Unhealthy – Sensitive groups|
|Ghaziabad – India||106.6||Unhealthy – Sensitive groups|
|Bulandshahr – India||98.4||Unhealthy – Sensitive groups|
|Bisrakh Jalalpur – India||96||Unhealthy – Sensitive groups|
|Bhiwandi – India||95.5||Unhealthy – Sensitive groups|
|Noida – India||94.3||Unhealthy – Sensitive groups|
|Greater Noida – India||89.5||Unhealthy – Sensitive groups|
|Kanpur – India||89.1||Unhealthy – Sensitive groups|
|Lucknow – India||86.2||Unhealthy – Sensitive groups|
|Delhi - India||84.1||Unhealthy – Sensitive groups|
India cuts a dismal picture in air pollution, with nine cities in the world’s worst ten most polluted cities in 2020. If we extend the statistics further to 50 cities, 26 more Indian cities make it a concerning figure of 35 cities in the worst 50 in the world.
Extending the statistics further, here are the worst ten polluted Indian cities on a real-time basis.
|Firozpur Jhirka – Haryana||191||Unhealthy|
|Bathinda – Punjab||162||Unhealthy|
|Jalandhar – Punjab||161||Unhealthy|
|Bawana – Delhi||157||Unhealthy|
|Amritsar – Punjab||153||Unhealthy|
|Narnaul – Haryana||151||Unhealthy|
|Muzaffarnagar – Uttar Pradesh||147||Unhealthy for Sensitive groups|
|Ludhiana – Punjab||145||Unhealthy for Sensitive groups|
|Hisar – Haryana||129||Unhealthy for Sensitive groups|
|Sirsa – Haryana||123||Unhealthy for Sensitive groups|
In contrast, here are the top ten least polluted cities in India on a real-time basis.
|Tarakeswar – West Bengal||2||Good|
|Sivakasi – Tamil Nadu||3||Good|
|Shillong – Meghalaya||7||Good|
|Shirhatti – Karnataka||8||Good|
|Meerut – Uttar Pradesh||9||Good|
|Gadag – Karnataka||10||Good|
|Gorakhpur – Uttar Pradesh||10||Good|
|Agartala – Tripura||12||Good|
|Brajrajnagar – Odisha||12||Good|
|Puducherry – Puducherry||12||Good|
Let us now understand the pollutant constituents and the harm they can cause to human health.
Particulate Matter – PM10 and PM2.5
Particulate Matter does not constitute a single pollutant but a complex mixture comprising solids, liquid droplets, dry solid fragments, aerosols, and solid cores with a liquid coating. Composition-wise, they contain organic and inorganic impurities. Particulate Matter of a diameter of more than 10 microns is trapped into the nasal cavity.
PM10 constitutes particulate Matter with a diameter of up to 10 microns. These pollutants can be inhaled into the lungs. Similarly, PM2.5 comprises particulate Matter with a diameter of up to 2.5 microns. PM2.5 and PM10 have different chemical compositions. Emissions from fuel, wood, petrol, diesel, and other organic compounds constitute PM2.5.
In contrast, dust from construction sites, landfills, bushfires, waste burning, agricultural waste, pollen, industrial emissions, and even wind-blown dust constitute PM10. PM10 and PM2.5 also include gases like NO2, SO2, CO, and organic compounds like camphor, benzene, etc.
Health and Other effects of PM
PM2.5 and PM10 are inhalable into the lungs. Hence, they can cause lung diseases, asthma attacks, chronic bronchitis, and other respiratory problems leading to heart attacks.
Amongst the population, older adults with a history of heart and lung diseases are at greater risk to experience harmful health effects with PM10 and PM2.5 exposure. Similarly, children are also equally vulnerable because they inhale more air pounds of body weight than adults.
Besides health issues, PM affects the environment by reducing visibility. In addition, PM has black carbon impurities that can lead to climate warming. Similarly, nitrate and sulfate constituents can cause climate cooling. Therefore, they affect the overall climate and ecosystem. In addition, PM can infiltrate soil and water and affect plant and animal life.
PM can be found everywhere, including indoors. These microscopic particles can enter houses through windows, doors, leakages in walls, etc. Besides, they can also originate from indoor sources like burning wood fuel, candles, camphor, incense sticks, tobacco, air fresheners, perfumes, etc. You also have other sources of PM like pollen, dust mites, cockroaches, and mold spores.
With India having an undesirable AQI, reducing PM10 and PM2.5 pollution is of paramount importance. One can use eco-friendly fuels to reduce organic emissions from vehicles and other sources.
Switching over to electric vehicles is a welcome step in this regard.
Another positive step in this direction is to stop burning crops and indulging in activities like lighting bonfires or bursting crackers. One should also switch over to LPG or other alternatives instead of burning wood and charcoal for cooking. One can also install air purifiers in homes, offices, and other susceptible areas.
Industrial Pollutants – NO2, SO2, CO, and Pb
The primary industrial pollutants are SO2, nitrogen oxides, and CO, especially if you use coal as fuel. In addition, fly ash and soot from chimneys contain carbon dioxide and carbon monoxide, whereas other emissions include NO2, SO2, Pb, etc.
However, industrial air pollution depends on the nature of industries functioning in the area. For example, cement manufacturing industries have different pollutants from chemical industries and oil refineries. Besides the pollutants listed above, other contaminants include mercury, chlorine, caustic soda, ammonia, etc.
Health effects of industrial pollutants
Inhaling poisonous gases like SO2 and others can cause respiratory issues for all individuals. People with a medical history of chronic ailments and children constitute a high-risk population. These gases can easily enter our lungs and cause diseases like bronchitis, asthma, pneumonia, tuberculosis, etc. In the times of COVID, such complications can prove fatal.
In addition, these industrial pollutants can cause skin infections and fertility issues. Furthermore, they can affect plant and animal life and thus indirectly affect the food chain ecosystem.
Industrial areas should be far from residential locations. Using proper disposal procedures can reduce industrial emissions. Instead of releasing NO2 and SO2, it is possible to convert these fumes into their respective acids and thus enable easy disposal. Industries have a role to play by releasing these gases high into the atmosphere.
Ozone is another common air pollutant found almost everywhere, especially in coastal areas. Three atoms of oxygen constitute ozone, and hence the formula, O3. It is one of the critical ingredients in smog, the smoke-filled environment we encounter in cities almost every day. The ozone concentration in the environment is more in coastal areas.
Ozone has a typical odor, similar to a fishy smell you encounter near the seashores. Humans can detect this smell even in small concentrations.
Ozone is also found in air cleaners indoors. Therefore, one should be careful when purchasing air purifiers. It is advisable to check out whether the purifier emits ozone in any way. Air purifiers using HEPA filters do not produce ozone, but ionizing air purifiers do because of their electric charge. They create oxygen ions that combine to form ozone.
Health effects of inhaling ozone
Ozone can damage your lungs. It can worsen ailments like asthma and compromise the body’s natural ability to fight respiratory infections. Other symptoms of ozone pollution include shortness of breath, chest pain, throat irritation, and coughing.
However, ozone has a tremendous role to play in protecting the Earth from harmful radiation. The ozone layer in the atmosphere prevents harmful radiation from the sun from entering it. Global warming is caused because of holes in the ozone layer created by environmental pollution.
Related: Air Purifier Filters
One should avoid using ionizing air purifiers, especially if there are asthmatic patients in the home.
There is no better feeling than inhaling pure oxygenated air into our lungs. It can enhance oxygen levels in the bloodstream and revitalize our internal organs. As it is, people wear masks during COVID. One should continue using them when venturing into industrial areas or commercial places witnessing high levels of automobile emissions.
As far as indoor air is concerned, air purifiers, especially the HEPA filter-equipped models, do a good job of purifying the air. Therefore, a collective effort is necessary to fight air pollution and make this country better for our future generations.