A rise in benzene pollution in the city air has sparked fears of a spurt in various types of cancers associated with exposure to the deadly chemical.
Experts blamed the steadily worsening benzene pollution in the city and the suburbs to the comeback of two-stroke autos that run on noxious katatel and the burgeoning of roadside eateries that rely on coal as fuel.
Data collected by Metro show that the occurrence of cancers said to be associated with benzene exposure have shot up in the city along with the rise in benzene pollution.
Metro has analysed data from the state pollution control board and found that the average benzene level in the city air from January 2012 to mid-February 2012 was 46 micrograms per cubic metre of air.
Though there is no daily or monthly standard, the central environment ministry has fixed 5 micrograms per cubic metre of air as the annual limit.
Benzene, which can trigger a range of malignancies, has always been a part of the cocktail of pollutants in the city air but its concentration has never before been this high.
In the winter of 2006-2007, the benzene level was around 35 micrograms per cubic metre of air. But once the high court’s blanket ban on two-stroke autorickshaws came into effect; the figure plummeted to 19 micrograms in 2008, and dipped even further in 2009.
A study by Jadavpur University had revealed that benzene was one of the main components of katatel, an adulterated version of petrol that most two-stroke autorickshaws used as fuel.
Experts link the recent rise in benzene level with the fumes released by autos still running on katatel.
“Two-stroke autos have not only made a comeback on the fringes like Jadavpur, Behala and Garden Reach, but also in many areas of the city proper just by donning green paint,” said automobile emission expert S.M. Ghosh.
Many of these autos are patronised by influential politicians, alleged sources.
Ghosh said the increase in the number of petrol-driven vehicles on the city roads has also contributed to the increase in benzene pollution.
Apart from automobile-related causes, fumes from petrol pumps and the proliferation of roadside eateries are responsible for benzene pollution, said experts.
“In Calcutta, one possible reason could be the mushrooming of thousands of road side eateries, which mainly run on coal,” said Dipak Chakrabarty, the former chief scientist of the state pollution control board. “The inefficient burning of coal leads to benzene emission.”
Anumita Roy Choudhury, an air pollution expert at the Delhi-based Center for Science and Environment (CSE), said: “Delhi’s benzene pollution is also on the rise and we have found that evaporation of fumes from petrol pumps is the major reason.”
The impact has already been felt in the city.
“According to international agencies for research on cancers and other reports, benzene is a confirmed human carcinogen, which can cause leukaemia (blood cancer), lung cancer, lymphoma and bladder cancer,” said Jaydip Biswas, the director of Chittaranjan National Cancer Institute.
“The increasing level of benzene in the city air and the upsurge of most cancers associated with benzene is of real concern,” Biswas added.
According to data collected in 2009 by the cancer institute, which maintains a Calcutta population-based cancer registry, lung cancer tops the list of cancers in males, with 16.7 per cent of total cases; urinary bladder cancer and lymphoma occupy the fourth and fifth places with 4.4 and 3.7 per cent respectively.
While lung cancer may be triggered by a host of pollutants, including benzene, cancer of the urinary bladder and lymphoma can be related specifically to benzene exposure, said Biswas.
The registry figure shows that both urinary bladder cancer and lymphoma have been consistently rising in the city over the last few years. That benzene may be playing a part is indicated by the fact that these cancers occupy far lower positions in the state cancer registry. The occurrence of leukaemia may be low, but oncologist Partha Basu, the clinical co-ordinator of the Calcutta population-based cancer registry, said leukaemia patients may be far more than what the registry reflects.
“Leukaemia patients often end up in paediatric or haematology departments and not in oncology departments. Hence, they may have gone under-reported in our registry, which primarily collects data from oncology departments and centres,” he said.
Environment activist Subhas Datta on Tuesday accused the transport department of not doing anything to curb night vehicular pollution despite orders from the high court and Supreme Court.
“Because of extreme inaction of the state transport department, the night pollution is increasing,” alleged Datta in a letter to transport minister Madan Mitra.
Datta said the department itself had earlier informed the high court that night pollution in the city sometimes crosses even the daytime levels.
The letter says it had been decided long back to set up 12 weigh-bridge checkposts on highways to monitor overloading, but only one has been set up. Even that is non-functional because of the “non-cooperation of senior transport department officials”.
Minister Mitra hasn’t seen the letter yet. “Overloading is becoming a serious problem. We are devising a strategy to undertake a combined drive of all departments to stop overloading,” he told Metro.