New Delhi, Nov. 18: India has revised standards for air quality for the first time in 15 years in a move that environmental experts say will overnight tar more cities and localities across the country as polluted beyond limits.

The new standards notified by the environment ministry have lowered maximum limits for pollutants such as sulphur dioxide and nitrogen oxide that carry the risk of respiratory illness and introduced new limits for pollutants left out earlier.

The limits will be the same across residential, industrial, and rural areas under the new standards, which will end the practice of providing less stringent limits for industrial zones. The new limits, developed by the Central Pollution Control Board in consultation with the Indian Institute of Technology, Kanpur, will replace existing standards notified in 1994.

Environment minister Jairam Ramesh said the new limits will push air quality standards in India to European levels. “But the big question is enforcement of standards. This is going to be a serious issue,” he said.

A senior environment ministry official said more cities and areas within cities are likely to find themselves exceeding the new limits. Data from the Central Pollution Control Board suggests that, even under old standards, two-thirds of 120 cities whose air quality is monitored by the board have higher than permissible levels of particulate matter — tiny particles spewed by motor vehicles and coal-burning plants.

The standards by themselves won’t lead to cleaner air, but could spur action,” officials said. “We’re hoping this will build pressure on city or state authorities to take corrective action to control air quality wherever limits are exceeded,” the official said. “Calcutta has imposed a ban on vehicles older than 15 years. Other cities may have to consider similar options,” he said.

Proposed future actions include the switch to cleaner automobile emissions standards in April 2010 — a responsibility of car manufacturers — in 11 cities across the country. India will introduce mandatory fuel efficiency standards by the end of 2011, Ramesh said. Such standards will compel manufacturers to produce vehicles that perform within the fuel efficiency limits.

An analysis by the non-government group Centre for Science and Environment has shown that in 80 per cent of the 120 cities the value of at least one pollutant exceeds the annual average limit imposed under the new standards.

Several localities — including five in the Calcutta-Howrah region — could be classified as critically polluted for oxides of nitrogen under the new standards, according to the CSE analysis. A site is classified as critically polluted when the level of the pollutant is 1.5 times higher than the maximum permissible limit.

The critically polluted sites are Town Hall and Sarojini Nagar (Delhi), Moulali, Lal Bazaar, Salt Lake and Minto Park (Calcutta), and Naskarpara (Howrah). “In the old standards, we had no area critically polluted,” said Anumita Roychoudhury, head of clean air campaign at the CSE.

“These standards are only a stick for action — future steps would have to come from authorities. We need measures to restrain the use of cars and encourage the use of public transport,” said Sunita Narain, director of CSE.

Environmental experts say India’s steep rise in vehicle population has contributed to growing air pollution. The Society for Indian Automobile Manufacturers has predicted that 50 per cent of cars sales in India will be diesel-run cars by 2010.

The standards have introduced limits for several pollutants not covered in 1994 — benzene, ozone, benzopyrene, arsenic, nickel and ammonia. Benzene may be emitted in vehicle emissions while ozone is produced when sunlight reacts with oxides of nitrogen from vehicle emissions.