The Most Polluted Cities in the World

Delhi is consistently reported to be one of the top polluted cities in the world. According to the World Air Quality Report by Swiss climate group, IQAir, Delhi was the most polluted capital city in the world in 2020 with an average PM2.5 of 84.1 despite lockdowns temporarily improving the air quality. 

Here’s another bummer: 22 out of 30 of the most polluted cities are in India. Neighboring cities of Noida, Ghaziabad, Faridabad, and Gurgaon also made it to the list, with Ghaziabad scoring the second spot overall. In fact, 94 of the 100 most polluted cities are located in India, China, and Pakistan.

Lahore was recently declared the most polluted city in the world when its air quality index (AQI) crossed the 700 mark. It was above 500 for four consecutive days. (Air is considered safe to breathe when the AQI is under 50 and it’s unhealthy for sensitive groups when the mark crosses 100.) On the IQAir World Air Quality Report 2020, it was ranked 18 and it’s the most polluted city in Pakistan.

Hotan topped the IQAir’s charts with a PM2.5 average of 110.2. Frequent and sudden dust storms in Hotan exacerbate the problem that plagues many other Chinese cities (Kashgar, Puyang, Hebi, Anyang, among others). Industrial pollution, emissions from vehicles, and unclean fuel sources are listed as the major causes, but the dust storms are the main culprit that drops visibility to less than 100 meters.

“These huge clouds of both fine and coarse particles make the air extremely polluted and dangerous to breathe, with these materials having many damaging effects to both the lungs and other systems in the body. Scarring of the lung tissue can occur which can lead to many ill health effects, as well as the tiniest particles having the ability to even enter the bloodstream and wreak further havoc on the various systems throughout the body,” according to IQAir.

Named the most polluted country in the world by IQAir, Bangladesh has many cities with unhealthy air quality, including Dhaka, Sreepur, and Manikganj. Throughout the entire month of November, the air quality of Dhaka was unhealthy (above 150). The highly populous city suffers through poor air for most of the year with brief respites during monsoons. It’s also among the top 30 polluted cities according to IQAir (PM2.5 was 77.1 in 2020). Dhaka’s vehicular emissions, brick kilns, and dust concentration are considered to be the main causes of the worsening air pollution problem.

One of the most polluted cities in Europe, Orzesze in the southern part of Poland records high AQI in the winter months. Factories and power plants, burning of fossil fuels, vehicular emissions, and construction sites are reasons that contributed to its status of the number one polluted city in Europe on IQAir’s report (its PM2.5 average in 2020 was 44.1).

The European Environmental Agency (EEA) ranked 323 European cities according to their air quality and the city of Nowy Sącz got the worst spot: 323rd. The data was released in June this year after calculating the average PM2.5 levels over the last two years. Overall, Poland didn’t fair very well–27 Polish cities were placed at the bottom. Nowy Sącz finished last with a PM2.5 score of 27.3.

Cremona, a city in northern Italy, did better than only Nowy Sącz on the EEA’s list—it had the 322nd spot. It was recorded with the PM2.5 value of 25.9, which is way higher than WHO’s old and new limit, but just slightly exceeds the European Union’s upper limit of 25μg/m3.

According to the American Lung Association, 40% of Americans (or 135 million) live in places with unhealthy particle pollution or unsafe ozone levels. The State of the Air data puts Bakersfield on the top of the list of “By Year Round Particle Pollution” out of 199 metropolitan areas, and it ranked second for high ozone days out of 226 metropolitan areas.