Terahertz scanners are not a likely threat to humans

I don't know if anyone has noticed but I have been on a crusade to respond to the enormous numbers of blogs reposting claims that terahertz exposure damages dna. I have reposted Dr. Dan Mittleman's comments found on this blog in responding to these blogs. Tonight I found the article which I repost below. (Perhaps the author read about Dr. Mittleman in my multiple responses?)


Angela Mulholland, CTV.ca News

Date: Sun. Jan. 10 2010 12:45 PM ET
With news this week that full-body scanners will soon be installed in airports across Canada, many are wondering: could the scanners be a risk to my health?

The security devices are designed to keep travellers safe by helping to detect weapons strapped to the bodies of would-be terrorists. Not only can they spot knives and guns hidden under clothes, just as a metal detector can, they can also spot high-density materials, such as plastics and objects used in explosives.

What makes the scanners controversial is that they use radiation to generate their images. And that has some wondering whether they might be dangerous, particularly for children and pregnant women, especially since it's known that exposure to high levels of radiation can cause serious health problems such as cancer.

At least one expert believes there is nothing to worry about.

"I would have no safety concerns about going through one of these scanners at the airport. Not even slightly," Daniel Mittleman, a physics professor in the Electrical and Computer Engineering faculty at Rice University in Houston, Tx. told CTV.ca by phone.

The scanners coming to Canadian airports use a relatively new form of imaging, something called millimeter wave technology (other scanners, using backscatter technology are being used installed some airports in the U.S.).

When a passenger steps into a millimeter wave scanner, extremely high-frequency radio waves pass over the body. As the energy is reflected off the body, it generates a three-dimensional image.

L-3 Communications, the makers of the devices to be used in Canada, says the scanners are safe and harmless, noting that they emit only non-ionizing radiation. Ionizing radiation is the most worrying kind of radiation, and is emitted by such things as X-rays and the ultraviolet light of the sun. That form of radiation, with prolonged exposure, can disrupt DNA and cause tissue damage.

Mittleman, who specializes in a technology with the complicated-sounding name of "terahertz time-domain spectroscopy", points out that radiation is around us in our environment everywhere, from the fusebox in your basement to the computer monitor on which you are reading this.

He doesn't believe that passing through a millimeter wave scanner at the airport would expose travellers to any more radiation than they experience every day.

"Room-temperature objects emit microwave and millimeter waves and terahertz radiation -- just by being at room temperature," he says.

"Just sitting in a room bathes you in terahertz radiation."

What also makes millimeter wave scanners superior to X-rays and other older imaging technologies is the fact that they emit only the tiniest amount of energy -- even lower than your cellphone or your TV's remote control.

"The amount of energy is miniscule," says Mittleman. "It's substantially, substantially less than an X-ray scanner."

Still, even if one pass through the scanners is safe, some worry about the cumulative effects of the machines, particularly for "frequent fliers" who might have to undergo multiple scans a year.

Mittleman says there are plenty of other health worries frequent fliers should be worried about.

"We know that getting on an airplane and flying 40,000 feet in the air that you're being exposed to much higher cosmic radiation than you would on the ground. That can have a cumulative effect. We know for sure there are health effects there, but people get on airplanes every day," he says.

"That's way more dangerous than a millimeter wave scanner -- like, ridiculously more dangerous."

Even standing next to your microwave oven is probably more dangerous than these scanners, he says.

Still, Mittleman says he's not ready to declare with 100 per cent certainty that the scanners are perfectly safe. He notes that the technology is relatively new and so there are still some questions about whether there are any the safety concerns of millimeter wave frequencies.

"My personal opinion is that the answer is no, there aren't. But the research has not been thoroughly done. So I think it's still a little bit of an open question," he said.

"But no one has yet proposed any convincing mechanism that would lead one to suspect that there are safety issues."