Now, Kolkata becomes most polluted metro city in India, air quality worse than Delhi

New Delhi, Nov 19: While Delhi, our national capital, always faces the flak for being the most polluted city and a health nightmare for its citizens, but this time the 'city of joy', Kolkata has silently pushed Delhi behind on the air quality index. In the past 72 hours, Kolkata's air quality index (AQI) has has dipped to "very poor" category, crossing levels registered in the national capital, as reported by TOI.

There are 19 automatic stations in Delhi to monitor the city's air quality as compared to only two in Kolkata.

Kolkata became the most polluted city in India:

The National Air Quality Index website showed that the overall PM 2.5 count at Rabindra Bharti University (RBU), one of the two stations in the city, stood at 381 (very poor) on Thursday when compared to Delhi's Ashok Vihar, considered to be the national capital's most polluted zones, where the AQI was recorded at 292.25. The average AQI at Victoria Memorial was noted at 310.75.

Kolkata's air quality index getting worse:

According to a report in the Times of India, Kolkata has only one-fourth of vehicles than in Delhi. A comparison of the pollution data at the two stations in Kolkata- Rabindra Bharti University(RBU) and Victoria Memorial Hall- with Ashok Vihar, on the Delhi's most polluted area, shows that Kolkata's AQI has been constantly that of the national capital's.

Air quality in winters:

Every year pollution levels in Kolkata rise rapidly in winters due to low wind speed, low temperature, and inversion trap pollution. In winters, particulate levels can be as high as four times the standards.

What is the air quality index?

The AQI is an index for reporting daily air quality. It tells how clean or polluted the air is and focuses on health effects one may experience within a few hours or days after breathing polluted air.

Environmental protection agency (EPA) calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide.

For each of these pollutants, EPA has established national air quality standards to protect public health.