With ether-based oxygenates falling out of favour, ethanol is emerging as one of the most favoured options worldwide. According to H B Mathur, professor emeritus at the Delhi College of Engineering, petrol-ethanol blend can reduce carbon monoxide and hydrocarbon emissions by up to 35-55 per cent. According to Saroj Misra of Winrock International, ethanol has the potential of reducing volatile organic compounds, a significant source of ground level ozone formation, by up to 30 per cent. Ethanol can also be blended with diesel to reduce emissions of carbon monoxide by 27 per cent, nitrogen oxides by five per cent and particulate matter emissions by as much as 41 per cent.

But the sceptics in the government think otherwise. A K Bhatnagar, director (research and development) at the Indian Oil Corporation says ethanol causes increase in aldehyde emissions and when aldehydes react with nitrogen in the air, it results in the formation of peroxy acetyl nitrate, a carcinogen.

But Mathur counters this. He says formaldehydes which are emitted while using mtbe blended petrol are more harmful compared to the acetaldehydes. The US Environmental Protection Agency has already designated formaldehydes as carcinogens.

Since all pollution abatement measures have some attendant risks, the decision needs to rest on the relatively safer option. Even in the us, where mtbe is being substituted by ethanol, health risks of ethanol are under investigation. The California Air Resources Board and the office of Environmental Health Hazard Assessment have been asked to assess the health and environmental impacts of ethanol. The draft analysis has found no significant risks stemming from blending ethanol in petrol.