Hyderabad: It is not just the air around us that is polluted with Carbon Monoxide (CO), but even the upper layers of the Troposphere, the first layer of atmosphere that extends up to 16 km from surface of the Earth, is polluted by CO.

A study conducted by five researchers from Physical Research Laboratory, Ahm-edabad, Indian Institute of Technology, Gandhi-nagar and Max-Planck Institute for Chemistry, Germany found high levels of CO as far as 10km from the surface of the earth in the Troposphere in five Indian cities – Ahmedabad, New Delhi, Dibrugarh, Trivandrum and Hyderabad.

The researchers collected values of CO at 200 Hectopacals (hPa), which is around 10 km from the surface and at 900hPa, around 800 meters from the earth's surface over a period of 14 years, from 2001-2014 across four seasons winter, spring, monsoon and autumn. The maximum value of CO, at 200hPa, was found to be highest, at 118 parts per billion volume (ppbv), over Ahmedabad followed by 115ppbv in Hyderabad during the monsoon season.At 900hPa, the maximum CO content in the Troposphere was recorded over Hyderabad at a whopping 228ppbv during winter, higher than New Delhi where it was recorded at 188ppbv.

The normal value for CO in Troposphere is considered to be around 50ppbv. Mr Naveen Chandra, of PRL Ahmedabad, who was part of the study said, "As Carbon Monoxide due to vehicular pollution and other sources is released, it travels upwards. In monsoon as there is a lot of wind, CO particles reach heights of 10 km as quickly as in two hours. That is why in monsoon CO values are the highest in upper layers of the Troposphere. In winter, it is opposite as there is not much wind and the CO particles are closer to the Earth's surface, at 900hPa than at 200hPa."

He further added, "While vehicular pollution is a major source of Carbon Monoxide, a major reason behind CO in troposphere is burning of biomass in African and Southeast Asian countries which releases huge quantities of Carbon Monoxide which is carried by the winds till India. That is the reason that CO levels over New Delhi is lower in some cases than Hyderabad or Dibrugarh in Assam, because the wind pattern is such that it flows over South India and other regions more than the northern parts in the country."

The data for CO by researchers was taken from Measurements of Pollution In The Troposphere (MOPITT) of NASA, USA. MOPITT website states, "Carbon monoxide plays a major role in atmospheric chemistry, and it affects the ability of the atmosphere to cleanse itself of many other polluting gases. In combination with other pollutants and sunshine, it also takes part in the formation of lower-atmospheric (“bad”) ozone and urban smog."