Poison in the air and smoking have propelled Calcutta to the top of the list of lung cancer incidence among the metros.
The comparative study on lung cancer, conducted by the Indian Council of Medical Research (ICMR), is part of the National Cancer Registry Programme 2009 and 2011.
The Telegraph had reported on Friday the World Health Organisation’s classification of outdoor air pollution as carcinogenic. The International Agency for Research on Cancer, which functions under the WHO, had set up a panel to review scientific literature on the topic. The experts said there was sufficient evidence to prove that exposure to air pollution causes lung cancer.
The ICMR study found that Calcutta has the highest number of new lung cancer cases among men — 16.8 per one-lakh population, followed by Delhi with 13.9 and Chennai with 12.6. A study in 2006-07 had found 14.9 cases per one lakh men in Calcutta.
“New lung cancer cases continue to be detected in Calcutta at a much faster rate than in the other metros. Two of the most important factors are air pollution and the smoking habit,” said Karabi Dutta, head of the department of epidemiology and bio-statistics at Chittaranjan National Cancer Institute.
Dutta and her colleague Jaydip Biswas, principal investigator and director of the Chittaranjan institute, had conducted the study along with M.N. Bandyopadhyay of the Saroj Gupta Cancer Centre & Research Institute.
The researchers covered a population of 9.42 million — 5.08 million male and 4.34 million female — across 52 wards of the Calcutta Municipal Corporation.
Calcutta topped the number of new lung cancer cases among females, too, with five out of every one lakh women, followed by Bangalore with 4.8 and Delhi and Chennai with 4.2 each.
In 2005, Delhi had topped the list of new cases with 13.5 per one lakh and Calcutta was third with 11.9.
Although the study is conducted every year, the latest available data is from 2009-11 since it takes time to compile and analyse the findings. The data on new cancer cases is collected from hospitals, nursing homes and pathological laboratories, an official of the Chittaranjan institute said.
Doctors blame fine pollutants spewed through automobile exhaust pipes and measuring less than 2.5 micron in diameter for the spurt in lung cancer cases. These pollutants invade the innermost recesses of the lungs.
The concentration of “very fine particulates”, also known as PM (particulate matter) 2.5, in Calcutta’s air is not only well above the national standard but also increasing rapidly. The overall respirable particulate concentration in the city, of which PM 2.5 is a fraction, has long been much above the national limit.
Data available with the state pollution control board show that the average concentration of PM 2.5 was 152 micrograms per cubic meter last December and January. This is more than double the national standard of 60 micrograms. Even more disconcerting is the fact that it is rising — the figure was 128 micrograms per cubic meter the winter before (2011-12).
“It has been proved by research that all particulate matter less than 2.5 microns in size are sucked into the deepest parts of the lungs and are mainly responsible for inducing permanent changes in cellular life cycles,” pulmonologist Asok Sengupta said.
After years of exposure to air pollution, a cell can mutate into a cancer cell. If that isn’t scary, here’s a piece of statistic that drives home the reality: at least 25 per cent of patients who visit clinics with lung disorders are non-smokers.