Claims that Apple's Mac Pros emit benzene are being denied by the company.
A French newspaper called Libération.fr published the results of a study by a researcher at France's INERIS claiming that odors stemming from certain Mac Pros are the result of benzene emissions. Complaints have surfaced in the past about some sort of weird odor coming from Mac Pros, but it was thought the odor was related to small strips of plastic or material around the heatsink on the processor, depending on where you looked.
The study claims that the benzene fumes won't kill you immediately or anything, but could cause health problems such as leukemia over time. Apple, however, told Macworld it has found no evidence of benzene emissions from the Mac Pro, although it continues to look into the issue.