Does anyone go through the newly ubiquitous body scanners at airport security and not wonder whether they are doing damage to themselves? I hope not. Because the short answer is we don't know.

We certainly know what the Transportation Security Administration says: The machines are "safe for all passengers" because they emit low doses of radiation. And while it's probably true — no one has proved anything to the contrary — truth can be a moving target. Today's "safe for all" has more than once become an appalling historical relic to future generations.

Though the machines are designed to check the exterior of the body for foreign objects, Taly Gilat Schmidt, a Marquette University assistant professor of biomedical engineering, wondered how much radiation enters the body during a scan.

She and then-Marquette graduate student Michael Hoppe used a virtual family — an adult male, adult female, male child and female child, all based on anatomies of actual people — broken into 2 millimeter cubes to examine how much radiation specific organs received. Sure enough, they concluded that the machines irradiate much of the body, the amount varying by the density, composition and location of an organ.

"There's a perception that they don't go past the skin," Schmidt said. "Anyone in my field knows that can't be true."

But — and it's a fortunate but — the amount of radiation is below the maximum dose considered safe by the Health Physics Society and American National Standards Institute. Which means we're safe, right?

Well, there's another but: The figures Schmidt and Hoppe plugged into their models were data resulting from federally commissioned studies; lack of access to the machines meant they could not measure the radiation for themselves. Schmidt acknowledges it's a major shortcoming.

"Our conclusions are only a beginning," she said. "Until we have more information, we can't draw comfort or concern. We need validation of the numbers in our model. We need independent physicists to go on site to airports and measure the amount of energy coming from these X-ray machines."

I asked the TSA for comment about Schmidt's call for independent confirmation and was given the following statement: "All the scientific testing done thus far has proved this technology is well within the national standards and safe for all passengers. TSA is committed to exploring options to further prove these machines are safe for all passengers."

Hopefully it happens.

In the meantime, Schmidt said that she submits to the airport scanners when traveling but that she would not let her children pass through. ("That's a decision not as a scientist but as a mom," she said.) And indeed, opting out is always an option. On a recent flight, out of curiosity, I tried it. It was relatively painless.

A TSA agent pulled me aside and, in plain view of fellow passengers, searched me as thoroughly as I've ever been searched. But it was painless because the agent was endlessly professional and courteous, telling me precisely what he would do before he did — such as run his finger around the inside of the waistband of my pants (while wearing rubber gloves). His clear communication, combined with my desire for thorough passenger screening, made the experience seem reasonable, even if it was far more invasive than what we would have experienced at an airport just a few years ago.

Within a couple of minutes, I was on my way, ever slightly less irradiated.