LEVELS of air pollution in Oxford soared above Government safety levels during the hottest Easter weekend for 30 years.

Under European Union targets, the level of nitrogen dioxide should not exceed 200 micrograms per cubic metre more than 18 times a year.

But levels reached closer to 300 micrograms per cubic metre in Oxford city centre on Thursday, caused by a combination of high pressure, the hot weather and traffic pollution.

By yesterday as temperatures had dipped from 26C on Saturday to a cooler 22C yesterday, the Department for the Environment, Food and Rural Affairs said that levels in Oxford were back down to being “low” at 59mcg.

It stated that unlike the start of the bank holiday weekend, pollution levels were unlikely to be noticed by asthmatics.

The hot weather sparked the smog alert as sunlight causes the formation of ozone by acting on nitrogen dioxide close to the ground and exhaust emissions from vehicles.

A second form of pollution, in the form of tiny particles known as PM10s, are also emitted by car exhausts and can cause headaches, burning eyes, coughing and an increased risk of heart attacks.

Both types of pollution can cause asthmatics to find breathing more difficult.

The UK will not face fines for the breach of the pollution target, as the EU has given Britain an extension, which means it has until June before it has to start meeting the standards across the country.