Last week I read with alarm reports that Apple’s mightiest Mac, the Mac Pro desktop, could emit toxic gases.

I am alarmed not only at the notion Apple could have sold a device that -- simply by turning it on -- could damage the health of the user, but because I own a Mac Pro myself.

This news originated with the French newspaper Liberation (available in English via an awkward Google translation), which reported that a molecular biologist working for a French national agency in February 2007 grew suspicious when he noticed an odd smell coming from his new Mac Pro.

After 10 days of using the new Mac, the scientist experienced pronounced eye and throat irritation. He contacted AppleCare, which dispatched a technician to switch the power supply. The odor remained.

Apple even replaced the system with another Mac Pro but that, too, vented the same strange smell.

Finally, the scientist had the gases analyzed by another lab, which detected seven “volatile organic contaminants,” including benzene, a commonly used industrial solvent and a known carcinogen. Prolonged exposure to benzene vapors can cause such illnesses as leukemia and lymphoma.

The scientist sent the lab results to Apple, which characteristically has sat on the information. After he published his report on the Internet, Apple phoned the scientist to tell him it would “resolve the problem within eight days.”

As it turns out, many Mac Pro owners back in 2007 noticed the same unusual odors coming from their computers and were discussing it amongst themselves, including on Apple’s own forums. Browsing through the discussions, its evident that few if any of the Mac Pro owners had any idea how dangerous the gases might be, though some expressed concern.

A reader of ZDNet’s Apple Core blog said AppleCare of France confirmed the problem to him over the phone, but said it affected Mac Pros built before 2008.

The original four-core Mac Pro debuted in August 2006; Apple added an eight-core version in April 2007. Those models were sold through January of this year, when the current version replaced it. That’s a lot of Mac Pros potentially affected.

To my relief, my Mac Pro is an early 2008 model, which Apple has said is safe. Thankfully I’ve never noticed any strange smells coming out of it.

What really bothers me, however, is Apple’s silence on this issue, despite having been made aware of it many months ago.

This is not a trivial matter. This is not about a battery a user can’t remove. This is not about discolored plastic casing on a laptop. This is not about losing access to your e-mail account for several days.

This is literally a life-threatening situation. Owners of these machines are scared and worried. If Apple has proof the smells coming from first-generation Mac Pros are harmless, it needs to make a public announcement to alleviate the concern.

If Apple in fact has learned the fumes are dangerous, it will need to do much more. In either case, keeping silent only makes matters worse.

If there’s even the smallest chance some Mac Pro owners and their families have been exposed to hazardous gases, Apple needs to alert them immediately so they can seek medical attention. And those Mac Pros would need to be recalled.

Over the past couple of years, Apple has improved on its responsiveness to customer complaints and owning up to corporate blunders like the bungled iPhone 3G/MobileMe launch.

But all that pales beside a dire health threat. Apple owes its customers an official explanation on this situation – and fast.

UPDATE: I was remiss in not mentioning that Apple has indeed issued an official statement on this matter, though it's not quite an explanation. As noted by Peter Cohen below, Apple's Bill Evans told Macworld Oct. 1: “We have not found anything that supports this claim, but continue to investigate it for the customer."

Also, it occurs to me that given the time frame involved, this issue -- while serious -- likely affected a relatively small number of users. Otherwise we would have heard much more about it long ago.