French newspaper Liberation writes some Apple's Mac Pro systems emit toxic gases, including the carcinogenic benzene:
Quoting a story from French paper Libération, the British paper says Mac Pros emit a burnt plastic odor caused partly by benzene fumes. A molecular biologist uncovered the issue and has gotten the attention of both Greenpeace and France's national institute for environmental and industrial risks. Benzene fumes could cause sensitive users to develop leukemias after just two months of daily exposure, says Annie Leszkowicz of the French workplace and environmental safety agency.
There are also some reports from users who noticed weird fumes coming from their Mac Pro:
This user on the MacRumors forums says the smell is "intense, nauseating, and makes you feel funny," while another Mac Pro owner on the official Apple support forums says, "I recently purchased the new 8-core and it emits a very musty odor when powered up. My entire room soon smells bad and I have had to resort to a few air fresheners just to be able to work on it."
MacWorld talked to Apple about this news report and heard the firm hasn't found anything that supports this claim:
While not dismissing the reports, Apple noted that it hadn’t found any evidence to prove the claim.
“We have not found anything that supports this claim, but continue to investigate it for the customer,” Apple spokesman Bill Evans told Macworld.
It's unclear what the root of the problem is and if Mac Pro's are the only systems affected.