Dawn air most toxic, stay away from morning walks

Subhro Niyogi, Prithvijit Mitra, TNN, KOLKATA: Your morning walk, the high point of thousands of Calcuttans’ daily exercise regime, may have become the unhealthiest part of the day, thanks to the city’s stratospheric pollution levels that tend to peak every morning.

Climate analysts and physicians warn that the air at that morning walkers breathe is the most toxic and advise people not to venture out till at least 7.30am when the pollution begins to dissipate as the sun warms the earth.

Particulate matter and noxious fumes have made Kolkata’s air during the early hours of the day more unhealthy to breathe than ever before, say doctors. Trapped in the early morning fog, the pollutants hang low and can infiltrate your bloodstream through the lungs if you venture out before 7am, they warn. Precautions like using a mask can protect you to an extent, but there are no fool-proof measures against pollution.

While the pollution count is high in the early mornings every winter, it has been particularly bad this year with the ultra-fine particulate matter of size 2.5 µg/m3 (PM 2.5) hovering over the 400 mark consistently between midnight and 6 am. Last month, too, it was consistently over the 300 mark, higher than the corresponding figure of November 2017.

“The concentration of PM 2.5—the finest particulate matter—has been alarmingly high early in the morning. This is due to the fact that the moisture level remains low in the early hours and traps the pollutants. It is imperative to take precautions while going out of home in the morning, though nothing can guarantee immunity from pollution,” said pulmonologist Ranjan Das.

What’s even more alarming is the expansion of the peak pollution hours from 9pm to 2am (5 hours) recorded on December 5 and 6 to 9pm to 9am (12 hours) on December 6-7. It expanded further —10 pm to 11 am— on December 7-8.

Noon to 6pm safest for outdoor activities’

An analysis of the hourly PM2.5 data at the automatic air quality monitoring stations at RBU and Victoria Memorial in the past three days shows that air is most toxic between 9 pm and 11am.

“People should walk in the afternoon now to reduce exposure to high PM 2.5 concentration. The data shows that it’s in the afternoon when PM 2.5 count is the lowest,” said cardiologist Amitava Basu.

“If you’re planning a picnic or insist on exercising outside, you’re usually best off doing it between noon and 6 pm,” he added. Though the PM 2.5 count is still five-times the safe limit of 60 during this period, it is far better than night and early morning when it reaches eight-times the safe limit.

Businessman Rajeev Lohia, who is at Rabindra Sarobar every morning, says he had felt the difference as did many others. “The air feels heavier. Around a decade ago, one felt more energetic during the early morning walks in winter because unlike summer, one doesn’t perspire. But in recent years, it’s been the other way round,” he said.

Among those who wear masks are engineer Gopal Mitra and his wife, Debrina, a teacher. They first took to wearing masks about five years ago in Delhi when the air took on an ominous gray hue. When they relocated here three years ago, they thought they were leaving the threat behind. But that wasn’t to be.

Tapan Das, a level 2 rowing coach at the lake and an international rower and umpire, says the situation is getting grimmer each winter. “A few days on, there will be a haze over the water that will bring rowing to a grinding halt. You can’t expose the kids to this level of pollution,” he said.