Pollution threat at Olympics

London - London's poor air quality could cause problems for Olympic athletes trying to break world records if a summer heat wave continues, British scientists said on Thursday as levels of pollution hit their highest levels since 2006.

The London Olympics has struggled with an array of teething problems in the run up to the Games, from security and transport concerns to the threat of union strikes. At one stage, even chilly wet weather looked like it might spoil the show.

But on the eve of the Games, temperatures and levels of ozone pollution have soared, breaking a World Health Organisation guideline and potentially causing breathing difficulties for athletes, King's College University researchers said.

"Athletes won't be able to get enough oxygen in the body to perform at the highest level. What that means is they probably won't be breaking any records under these conditions," Professor Frank Kelly, Director of King's College London's Environmental Research Group, told Reuters.

"They're not ideal for athletics and certainly not for long distance events," he added.

The British government issued an air quality warning for ozone levels on Wednesday after ozone concentration in parts of southern England reached over 190 micrograms per cubic metre.

The World Health Organisation guideline is 100.

Athletes are thought to be especially vulnerable because they breathe in lots of air very quickly over many hours, said Dr Gary Fuller, a senior lecturer in air quality measurement at King's College.

Even non-Olympians may notice the pollution levels.

"Probably about 20% of the healthy population will feel some tightening of the chest as they go about daily normal activities," said Kelly.

"If people are involved in any sort of exercise, they're probably going to feel even more effects."

Government officials said most people were not affected by short term peaks in ozone but those with existing heart or lung conditions may experience increased symptoms.

The increase in ozone levels was caused by searing temperatures heating up traffic and industrial pollutants and the hot air re-circulating slowly across densely populated south east England and western Europe.

A cooler front is expected to arrive in Britain in time for the opening ceremony of the Games on Friday.