Budapest - As air pollution levels reached worryingly high levels, the Budapest Mayor's Office urged citizens of the Hungarian capital to leave their cars at home on Tuesday and said that an official smog warning could be issued on New Year's Day.

With Budapest cloaked in smog, Istvan Bozoky of Hungary's National Meteorological Service told the local news agency MTI that no wind is expected before Thursday, so the situation is unlikely to improve.

The high profile environmental pressure group, the Clean Air Action Group, called on Budapest residents not to wait until the official warning is issued.

"Today the level of the most hazardous type of air pollution ... has risen dangerously, so the Clean Air Action Group asks residents not to linger in the streets and to drive as little as possible," the organization said in a statement.

The level of PM10 particulate matter, the microscopic dust that makes smog, reached 75 micrograms per cubic metre at three locations around Budapest on Monday. New rules mean that a general warning must be issued if this level of air pollution continues for two consecutive days.

By Tuesday afternoon, readings from air quality monitoring stations in Budapest showed that 24-hour average PM10 levels in the city centre were close to, and in one location even exceeded, 100 micrograms.

If the level of particulate matter averages over 100 micrograms on two consecutive 24-hour periods, local regulations mean the authorities in Budapest must issue a full scale smog alert. New anti- smog traffic restrictions could then be put to their be put to their first test.

A city council ruling that came into effect at the beginning of December means that in the event of a full-scale smog alert, half of all cars are automatically banned from the streets of Budapest.

If the smog alert is issued on an odd numbered date, only cars with odd numbered registration plates are permitted to drive in the city. On other dates, only the owners of even numbered vehicles are allowed to continue pumping out their exhaust fumes.

The European Commission has set strict PM10 pollution targets that, even with recent extensions, members must adopt as law by 2011. Levels should not rise above
50 on more than 35 days a year, while the average for the year as a whole must be below 40.

At some locations in Hungary, PM10 levels exceed 50 micrograms per cubic metre on 120 to 150 days, and the European Commission estimates that about 40 per cent of air quality zones in the European Union do not comply with the standard. (dpa)