The implications of the re-evaluation can run deep for countries like India which are both populous and at a stage of rapid industrialisation, says environmental scientist Kalpana Balakrishnan.

With the World Health Organisation (WHO) raising the status of outdoor air pollutants from background threat for cancers to a definite risk, the implications of the re-evaluation can run deep for countries like India which are both populous and at a stage of rapid industrialisation, says environmental scientist Kalpana Balakrishnan.

Dr. Balakrishnan was part of the global panel of scientists convened by WHO’s International Agency for Research on Cancer (IARC) for formulating the Monograph (Vol. 109) on Ambient Air Pollution at Lyon, France.

The IARC had concluded that ambient air pollution was class 1 carcinogen after drawing from compelling evidence that exposure to outdoor pollutants caused lung cancer.

The evidence also indicated a positive association with an increased risk of bladder cancer.

“What brings an urgency to activate policy to scale down vehicular and industrial emissions and exposure levels in India is the fact that the WHO’s global assessment was driven by significant subsets of data on exposure levels from this country along with the broader Asian region,” said Dr. Balakrishnan, who is Professor and Head of the WHO Collaborating Centre at Sri Ramachandra University.

The IARC evaluation showed an increasing risk of lung cancer with increasing levels of exposure to particulate matter and air pollution. Although the composition of air pollution and levels of exposure can vary dramatically between locations, the conclusions of the WHO’s working group apply to all regions of the world. In fact, most recent data indicated that three years ago, nearly 2,23,000 deaths from lung cancer worldwide resulted from air pollution.

Though previously many individual chemicals and specific mixtures in ambient air such as diesel engine exhaust, solvents, metals, and dusts have come under scrutiny, this was the first time that experts unequivocally pinned down outdoor air pollution as a cause of cancer based on exposure, epidemiological evidence and toxicology criteria.

The IARC listed as some of the predominant sources of outdoor air pollution urban transportation, stationary power generation, industrial and agricultural emissions and residential heating and cooking.

According to Dr. Balakrishnan, the classification of outdoor air pollution as a ‘Group 1’ agent shifts risk perception about pollutants and cancers from a scenario of the plausible to the realm of a definitive correlation. And this holds serious implications for South Asia and India.

“In fact, India is dealing with a formidable double burden … of ambient air pollution and the well established health risks from household air pollution through the use of solid fuels … household air pollution was classified by IARC as a probable human carcinogen in 2006,” she said.

Identify hot spots

Dr. Balakrishnan advocated measures to identify hot spots of vehicular and industrial air pollution and populations at highest risk due to exposures.

The ambient air quality monitoring systems should also be strengthened to provide for detailed profiling of air toxics together with routine data on particulate matter, and integrated with cancer registries to help deduce differential prevalence rates across exposure levels, she said.

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