The latest measurements of ozone damage show it is almost as bad as the worst year recorded.

The British scientist who discovered the Antarctic "ozone hole", Joe Farman, says it is continuing because emissions of ozone-depleting bromine compounds are increasing.

Dr Farman said the damage showed no sign yet of recovery. And he said several new chemicals were not helping to repair the damage.

Dr Farman, who was a British Antarctic Survey scientist when his team detected substantial thinning in stratospheric ozone in 1985, is now a consultant to the European Ozone Research Coordinating Unit, based in Cambridge, UK.

Recovery far off

He told BBC News Online: "Looking at the first week of October, this year emerges as the worst apart from 1993. That was the year when the eruption of Mount Pinatubo had a cooling effect on the stratosphere.

"There's not the slightest sign of recovery in the Antarctic. And it's probably early to be looking for any sign yet.

"Every year is different. The stratosphere is rather like an English summer - you get some rotten years, and some good ones.

"There's no trend yet, because every year since 1989 has been pretty horrible," he said.

"It will probably be mid-century before things return to normal. The evidence is building up that the stratosphere is cooling, and that will probably be statistically certain within a year or two."

In September, the Antarctic ozone hole measured 26 million square kilometres (10 million square miles), slightly less than 2000's record hole of 30 million square kilometres (11.6 million square miles).

Partial limits

The ozone layer protects all living things against harmful ultra-violet radiation from the Sun, which can cause skin cancer, and damage to the eyes and the immune system.

Production and use of the main ozone-depleting gases - chiefly chlorofluorocarbons (CFCs) and halons - are limited under the Montreal Protocol, the international agreement on phasing out ozone depleters.

Dr Farman said: "The protocol has helped: chlorine is under control. But bromine isn't."

Scientists are worried about several new bromine compounds which are not listed in the protocol.

The UN Environment Programme (Unep) ozone secretariat has identified at least four potential problem chemicals. Each has up to 15 names, which complicates monitoring them.

The four suspect chemicals are:

• hexachlorobutadiene, used as a solvent. It is a by-product of chlorinated chemical production;
• n-propyl bromide, a solvent and feedstock. Montreal Protocol scientists estimate current use at 5,000-10,000 tonnes annually, and believe it could be 20,000-60,000 tonnes by 2010;
• 6-bromo-2-methoxyl-naphthalene, used to make methyl bromide, a fumigant controlled under the protocol;
• halon-1202, a highly effective electrical fire extinguisher.

"It's relatively small, and it's not worth making a great song-and-dance about it. But it's an indication of the wrong sort of thinking," he said.

"You might be able to tolerate their effect in 50 years' time, when chlorine is down by half. But you can't tolerate it now."

Images courtesy of M. Guirlet, F. Goutail, C. Schiller and B. Vogel/European Ozone Research Coordinating Unit