WHO sounds alarm: diesel exhaust causes lung cancer

Cities in India have seen an explosion of diesel vehicles in recent years. As the gap between the prices of diesel and petrol widens,the sale of diesel variants has galloped while petrol car inventories have piled up.

IARC,which is a part of WHO,has been evaluating environmental factors associated with cancer since 1971. At a weeklong meeting of international experts that concluded on June 12 in Lyon,the agency decided to upgrade diesel fumes from their 25-year-old risk category of “probable carcinogen” (Group 2A) to “known carcinogen” (Group 1).

Dr Christopher Portier,chairman of the IARC working group,said in a statement,“The scientific evidence was compelling and the working group’s conclusion was unanimous: diesel engine exhaust causes lung cancer in humans.”

The working group’s decision was based on two large epidemiological studies published by the National Cancer Institute in the USA this March.

Scientists who were part of the deliberations said the changed categorisation implies a significant increase in the risk of lung cancer for a bigger population. Dr Robert Baan,senior peer scientist at IARC told The Indian Express,“All the experts were convinced there was at least a 30-40 per cent greater chance of lung cancer with inhalation of diesel fumes than what was believed so far.”

“Also,where we believed heavily exposed occupational groups like mine workers and truck drivers were at risk earlier,now we have extended it to the general population,basically anybody who is within breathing range of the fumes,” Dr Baan said.

The scientist said the group had expedited the decision to notify the risk from diesel fumes because of the lack of “stringent regulations” in developing countries like India.

“The US adopted strict emission and technology standards almost two decades ago,which have since been replicated in Europe. Measures like reducing the sulphur content in fuel,changing engine design to burn diesel fuel more efficiently and reductions in emissions through exhaust control technology have helped. But in countries like India,it will take decades for such measures to come into place,so we needed to issue a warning,” Dr Baan said.

Medical and environmental experts in India said the IARC warning is significant in the context of the “mindless dieselisation” under way in India,especially since the country had produced no research to document the risks of lung cancer from exposure to diesel fumes.

Dr Vinod Raina,head of medical oncology at AIIMS,said,“There has been no scientific study to quantify the association between diesel fumes and lung cancer in our country,though the number of diesel vehicles have increased from 10 per cent a decade ago to over 50 per cent today.”

Dr S K Jindal,head of pulmonary medicine at PGI,Chandigarh,said that diesel fumes have been proven to be associated with risks of cardiovascular ailments and compromised brain function as well.

Anumita Roy Chowdhury of the Centre for Science and Environment said,“Euro IV emission standards are in place in only 13 cities in India; the rest of the country still follows Euro III standards. The USA adopted Euro IV in 2005.” Euro III vehicles use diesel with 350 PPMs of sulphur,the major pollutant in the fuel — the norm in western countries,by contrast,is just 10 PPMs of sulphur.

Roychowdhury said the WHO notification was a “definitive warning”,and policymakers can no longer delay taking steps on the excuse that the toxicity of diesel fumes is not established.

Health ministry officials said the environment ministry had taken vehicular pollution “very lightly”.

“In meetings to discuss the health hazards of toxic fuels,the standard arugment is that vehicular emissions make up barely 20 per cent of the total air pollution. But a study in California in 2005 showed that an 8-12 per cent share in the total air pollution level could contribute to 70 per cent of cancers,” a senior health ministry official said.