Why is Chennai Choking?

By: Nityanand Jayaraman

Delhi might have dominated the headlines when it comes to air pollution, but sadly other cities in India seem to be catching up. 

Times of India

Chennai is one such city. The city has seen a spike in the air quality levels. It’s so bad that experts have said breathing in the air in Chennai is equal to smoking 3.5 cigarettes every day. This includes everybody in Chennai even children.  

Here’s how the air pollution story has been unfolding in Chennai. 

I did a bit of data research on the Central Pollution Control Board’s air pollution data –1 specifically PM 2.5 levels – at IIT-Madras, Alandur and Manali monitoring stations for the 365 days ending November 5, 2019.

PM 2.5 refers to microscopic particulate matter that is less than 2.5 micrometers in size. PM 2.5 is a good indicator and measure of pollution as it exerts high toxic effects.

PM 2.5 pollution levels of 61 to 90 ug/m3 is referred to as “moderately polluted”; PM 2.5 levels of 91 to 120 as “Poor”; 121 to 250 as “Very Poor”; and above 250 ug/m3 as “Severe.”

Date  Manali PM 2.5 (ug/m3)Alandur PM 2.5 (ug/m3)IIT-Madras PM 2.5 (ug/m3)
3 November 2019         113  73.6 70
4 November 2019         130112.6113
5 November 2019       114.57126.8116.8

Table: PM 2.5 levels from 1 November to 5 November 2019

If you observe the above table, you’ll notice a spike in PM2.5 from November 3 to November 4. In IIT-Madras and Alandur, for instance, pollution worsened from “Moderately Polluted” to “Poor.” In Manali, it worsened from “Poor” to “Very Poor.”

High pollution levels reduce life years

Even if the air is  “moderately polluted”, it will reduce one’s life years. One study found that average life span increases by four months for every 10 ug/m3 drop in PM 2.5.

The levels recorded in Chennai from November 3 to 5 ranged from “Very Poor” to “Poor”. 

PM 2.5 levels ug/m3Manali station (No. of days)Alandur station (No. of days)IIT-Madras station(No. of days)
61 to 90 (Moderately Polluted)842424
90 to 120 (Poor)2264
120 to 250 (Very Poor)1240
>250 (Severe)140

The above data shows that Manali station had a total of 119 bad air quality days. Of this, 13 were days when PM 2.5 levels ranged from “Very Poor” to “Severe”. Same with Alandur, which recorded four days of “Very Poor” and four days of “Severe” pollution in the last year.

Only one out of four days fell in the last week, and none of the four severely polluted days when air pollution was above 250 ug/m3 fell in the last week. If Alandur, February and March 2019 were the worst months. 

Is North India responsible for air pollution in the south?

Chennai has 3,300 MW of coal-fired thermal power plants and a 10 million tonne per annum petroleum refinery which is enough for severe air pollution to take place.

Even though, pollution plumes may travel and cause a slight decrease in air quality, a noticeable spike in polluted areas like Chennai city is unlikely. Sources of pollution in Chennai have been discharging pollutants for the spike to happen.

I looked at TNPCB’s Care Air Centre real time air monitoring data from NTPC’s Vallur power plant and TANGEDCO’s North Chennai Thermal Power Station. Emissions of oxides of Nitrogen from NTPC Unit 3 and Unit 1 were consistently above the prescribed standard of 300 mg/m3 and ranged between 525 and 620 mg/m3 – more than twice the accepted levels.

NTPC Unit 1 data

NTPC Unit 3 data

Sulphur dioxide levels for the same duration ranged from 910 to 1000 mg/m3 – the maximum recordable by the SO2 sensor – for Unit 3. Meanwhile, Unit 1’s emissions were consistently above the highest detection limit of the sensor and clocked a steady 995.9 mg/m3.

TANGEDCO’s Unit 2 shows particulate matter (PM) at between 125 and 180 mg/m3 against an emission standard of 100 mg/m3. SO2 levels from this unit ranged between 290 and 335 ppm against a standard of 76 ppm. Oxides of nitrogen ranged from 380 to 420 ppm against a threshold of 159 ppm.

TANGEDCO Unit 2 data

TANGEDCO’s Stage 2’s second chimney registered SO2 levels between 320 and 360 ppm against a prescribed threshold of 76 ppm

TANGEDCO Stage 2’s second chimney data

A Pollution Board official in an interview said, “There is nothing to be alarmed of. These levels of PM 2.5 are only temporary due to the weather.”

The official also said that they “are continuously monitoring industries and taking steps to reduce emission levels if they cross levels.”

But where are the results? I just monitored the TNPCB’s monitoring system and found that emission levels have crossed levels, including maxing out at more than 1000 mg/m3 of SO2 at Units 1 and 3 of NTPC’s plant in Vallur (see charts above).

To see if they were continuously monitoring, I looked at the real-time monitoring data from the 43 sensors located atop more than a dozen stacks at the Chennai Petrochemical Ltd’s (CPCL) refinery in Manali. Not a single monitor was working.

So next time, when you feel out of breath in Chennai, like the Pollution Board representative believe that ignorance is bliss.

(The views expressed in the article are the author’s own. Let Me Breathe neither endorses nor is responsible for them.)

Nityanand Jayaraman

Nityanand Jayaraman

Nityanand Jayaraman is a writer and researcher based in Chennai.

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