The November-2016 smog incident in Delhi, when air contamination had hit perilous levels, might have temporarily activated a “spike” in the rate of death in the nationwide capital, according to specialists.

In the first week of November last year, Delhi’s air excellence had plunged, as the toxic smoke of the Diwali rockets and the hostile weather conditions, trapped the pollutants, which in turn shrouded the city, severely affecting even visibility.

A boffin with the Delhi-based CSIR- Institute of Genomics and Integrative Biology said the situation could very well have been like London’s Great Smog of 1952, which had caused at least 4,000 deaths.

“There could have been a spike. Throughout the London smog there was a big hurdle in the rate of death. But we don’t have a scheme where we maintain a proper and full-proof record of deaths happening in the city,” he told PTI.

But how will one establish causality i.e. how will it be possible to link the temporary spike in death rate, if any, to rise in pollution levels?

Who focuses on the biological and clinical features of respiratory diseases, explained how the London death statistics were arrived at and said the same process can be applied here.

He said two sets of data: The actual death rate experiential during the smog episode, and b) the death rate logged during the corresponding period the previous year when pollution levels remained low, would have to be factored in.

“You extrapolate the preceding year’s death rate as the baseline death rate. Then the actual death rate observed during the corresponding period will have to deduct from the baseline rate. The result would be the excess death rate.

“This is primarily, because the climatological conditions in the two cities vary widely. There may have been a spurt in breathing diseases, but one cannot say the same around deaths.

The November spell of smog remained such that for the chief time in history of the city, schools had to be shut; coal- based power plants were closed, as part of a raft of emergency measures declared by the Delhi government.

The Centre for Science and Setting (CSE) had described the situation as disturbing and the smog episode as the nastiest.