Posts on Apple's own discussion boards suggest the Mac maker knew about potentially toxic odors being linked to its computers as early as December last year. While benzene was not mentioned in the posts, many users complained of experiencing headaches, nausea and dizziness. The smell has been variously described as "new car smell", "musty", "rotting carpet" and even cannabis.

"My entire room smells bad and I have had to resort to a few air fresheners just to be able to work on it," one report read. Another user on Apple's discussion board linked the toxic odour to the death of their bird: "I recently have had a bird die 'mysteriously' which was caged near my MacPro which has had the terrible smell for months. The vet said it was likely he inhaled something toxic!!!" In Liberation's article, written in French, the researcher said his eyes, nose and throat became irritated after 10 days of using the computer.

"The computer emitted fumes which, after a week of use, caused a pronounced irritation of the cornea and respiratory passages," he said. Apple changed the researcher's power supply before replacing the entire computer but the strange smell remained.

He then contacted Greenpeace, which sent the computer to the Analytica lab for analysis. Seven "volatile organic contaminants" were identified, including styrene, benzene and its derivatives. Benzene, a known carcinogen, damages bone marrow and can cause a decrease in red blood cells, leading to leukemia and other blood cancers. It can be found in tobacco smoke, plastics, styrene and products such as glues, paints and detergents. But the chemical's presence in consumer products such as computers has dropped sharply as its severe health consequences have come to light.

Although officially Apple says it has found no evidence of the toxins, its customer support staff have allegedly told some callers that the company was aware of the problem, which concerned Mac Pro computers built before this year. Liberation, which has a daily circulation of about 130,000 copies, reported Apple France as saying its engineers were working on the problem.

Apple's public relations team is notorious for refusing to acknowledge reported faults in its products. But some users on the company's discussion boards have come up with their own solution. Some reports say the smell - apparently caused by a protective resin coating on some of the circuit boards - disappears after an initial "burn-in" period. Others have fixed the problem by removing small plastic strips from the side door of the computer case.