Kolkata’s air quality index worse than Delhi: How did it become the most polluted city in India?

In the past 72 hours, Kolkata surpassed Delhi in becoming the most polluted metropolitan city in India.

fter Diwali, Delhi’s air quality got worse as the air quality index (AQI) dipped from ‘very poor’ to ‘severe.’ But it turns out, Delhi is not the most polluted city after all.

In the past 72 hours, Kolkata surpassed Delhi in becoming the most polluted metropolitan city.

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.

Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country.

How does the AQI work?

The AQI is divided into six categories.(Image: airnow.gov)

• Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern
• For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality
• An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. AQI values below 100 are generally thought of as satisfactory
• When AQI values are above 100, air quality is considered to be unhealthy

AQI notings over the past week

Two stations of Kolkata were compared to Ashok Vihar, Delhi’s most polluted area which showed that Kolkata’s AQI has been the same as Delhi’s. There are 19 automatic stations in Delhi to monitor the city’s air quality against only two in Kolkata.

On November 15, 2018

Kolkata’s Rabindra Bharti University (RBU) stood at 381 (very poor), Victoria Memorial’s AQI was noted at 310.75 whereas Ashok Vihar’s AQI was recorded at 292.25.

On November 16, 2018

The average AQI at RBU stood at 359.75 while Ashok Vihar’s AQI was recorded at 292.25. An AQI of 288 was registered at Victoria Memorial.

On November 17, 2018

The average AQI at RBU stood at 330.25 when compared to Ashok Vihar, where the AQI was recorded at 293. Victoria Memorial noted an AQI of 242.5.

On November 18, 2018

Kolkata’s air quality improved on Saturday as the AQI at RBU was noted at 355 and 246 at Victoria Memorial. At Ashok Vihar, the AQI was registered at 369.

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.

Application of National Air Quality Standards shows that November onwards, more days fall in the air quality categories of poor, very poor and severe. This enhances public health risk which requires a pollution emergency measure Delhi has started to enforce.

Increase in diesel cars

A study carried out by researchers of the University of Kolkata in 2013 shows that in contrast to the national trend, new diesel cars are 65 per cent of new car sales in Kolkata.

About 99 per cent of commercial vehicles in Kolkata are diesel driven. This is a very serious concern as the world health organisation (WHO) had classified diesel emissions as class 1 carcinogen for its strong link with lung cancer — putting it in the same class as tobacco smoking.

Adverse effects on people

According to the Comprehensive Mobility Plan, around 70 per cent of Kolkata’s 18 million inhabitants suffer from respiratory problems such as asthma and lung cancer, which are caused by pollution from the city’s chaotic transport sector.

Studies carried out by Chittaranjan National Cancer Research Institute have found that more than 60 per cent children in Kolkata were diagnosed with lung function impairments as compared to 24 per cent in cleaner areas.

Healthy individuals and non-smokers have also shown respiratory symptoms and lung function impairment.

Visit Amri Hospital Best Hospital in Kolkata