If you can smell the sweet smell of benzene it means that

Apple is investigating a complaint that its pre-2008 Mac Pros emit fumes from the chemical benzene. One user told Apple that he noticed a strong smell when he unpacked his Mac last year, and that 10 days later, he developed nose and throat irritation, reports the French newspaper Liberation. (A clunky English translation of the report can be found here.)

“We have not found anything that supports this claim, but continue to investigate it for the customer," Apple spokesman Bill Evans said in an email. Evans did not say whether benzene, a solvent used in plastics, is a component of the computer.

Mac Pro users on an Apple discussion board have also complained of "new car smell" and other odors the first time they fired up their units – and, in some cases, when they ran them later.

The company said last year that all of its new products would be free from brominated flame retardants (BFRs) and polyvinyl chloride (PVC), a chlorinated plastic, by the end of this year.

We asked Philip Landrigan, chair of the department of community and preventive medicine at the Mount Sinai School of Medicine in New York, about the potential risks of benzene.

This is an edited transcript of the interview.

What is benzene?

It’s a very widely used chemical, a solvent. It's also used widely as a building block in organic chemistry to create molecules. It's been used for 100 years in an enormous range of plastics. There's some in gasoline — less than there used to be — and it's in jet fuel. It used to be used in dry cleaning.

What does it smell like?

Some would call it sweet, some pungent. It's natural [not an added scent]. It vaporizes easily so if you put it in a dish in a room, you'd smell it instantaneously.

Is benzene dangerous?

Solvent vapors can cause headache and nausea. From a toxic point of view, benzene is a known human carcinogen [according to] the Environmental Protection Agency, the Occupational Safety and Health Administration, the World Health Organization and virtually any regulatory body you could name.

There's some disagreement about how much is needed to cause cancer or what kinds of cancer it causes, but there's no debate about whether it's a carcinogen and it's most closely associated with leukemia and lymphoma. The best scientific opinion says any amount of exposure is dangerous and more exposure is more dangerous. Industry thinks you can expose people to a fair bit safely and environmental scientists are worried about even low levels of exposure.

How would one find out if a computer or other product was emitting benzene?

[An industrial hygienist] would set up an air sampling pump, which pulls air through a filter and measures how much of a contaminant like benzene is in the air. I'd find a room, sample the air for a couple hours and establish a baseline. Then I'd plug in the computer and see if there was an increase in the level of benzene in the air. Then we'd know.

Why might benzene be in a computer, and would it be dangerous?

They probably use it in the manufacturing of the computer as a solvent to clean up components, but you'd think it would vaporize off in the factory. If there were benzene in a computer or the plastic of a computer, as soon as the computer warmed up, it would start to vaporize. If there's any in there, it ought to gas off pretty quickly.

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