What a CDC nuclear radiation expert says to people who worry about cancer from cellphones and Bluetooth devices

• There is no good evidence that radiation from cell phones causes cancer, but the possibility can't be ruled out.
• Either way, wearing a wired headset or Bluetooth headphones is a good way to reduce radiation.

Radiation biophysicist Armin Ansari is serious about accurately conveying the potentially life-threatening harms of radiation.

He's worked at the US Centers for Disease Control for nearly 20 years, where he leads the team tasked with 'radiological assessment,' preparing best practices and instruction manuals for what to do if a nuclear disaster ever strikes the US.

So when he fields questions from concerned family members about how radiation might affect their cancer risk, as they hold cellphones to their ears and put Bluetooth devices on day after day, he takes their concerns seriously.

The truth is that he can't allay their health fears completely, though he can say that the evidence we have so far suggests these technologies are very safe.

"Can someone say definitively that there's no risk? No, you can't say that," he told Insider during a recent Association of Health Care Journalists fellowship.

"If there is a risk, we do know, based on the studies, that it's really, really low - if there is a risk," he added.

"Sorry, it is not a clear cut answer."

Not all radiation is created equal

Radiation is, by definition, energy traveling through space at the speed of light. But not all radiation is dangerous in the same way.

The frequency of radiation, or how energetic and powerful it is, matters a lot. High frequency radiation, like what's in X-ray machines and (on the very extreme end of the spectrum) nuclear bombs, is considered ionizing radiation because it consists of subatomic particles and electromagnetic waves powerful enough to remove electrons from molecules, and damage our DNA.

Ansari uses this chart to explain the difference between the two kinds of radiation, ionizing and non-ionizing:

"The difference in energy is enormous, looking from one end of the spectrum to the other end," he said. The energy in high frequency ionizing radiation, represented on the right hand side of the spectrum in orange, "is billion, billion, billion times greater than the left side," he said.

Because of this, "the way they interact with biological tissue is very different," he added.

In the most extreme cases, when people are exposed to extremely high doses of high frequency radiation, death is certain and swift, happening within 48 hours. But with non-ionizing radiation, it's still not clear how much risk exists, and whether there's really any to worry about at all.

"With radiation, dose is one of the, if not the most important determinant of the outcome of exposure," Ansari said.

Ionizing radiation from X-rays, space, and radon pose a health danger

Ionizing radiation that doesn't kill us will not make us stronger.

Many forms of ionizing radiation, such as X-rays and high energy UV rays, can increase a person's risk of developing cancer. (Ironically, radiation also comes in handy for attacking and treating cancer too).

Certain people are exposed to ionizing radiation more routinely than others by virtue of their profession. X-ray technicians, as well as pilots, astronauts, and flight attendants (who are exposed to more cosmic ionizing radiation) all have higher than average exposures to high frequency radiation that can put them at risk of long-term health consequences.

Most of us get our biggest doses of ionizing radiation from relatively infrequent medical X-rays. Radon, a naturally occurring radioactive gas, is also a big threat - it's the number one cause of lung cancer in non-smokers. But you can easily test for it at home with an inexpensive kit.

It's hard to say conclusively that cellphone radiation poses any danger to us

It's still not clear whether any of the non-ionizing radiofrequency radiation emitted from your cell phone every day could pose a health risk. Unlike ionizing radiation, radio waves don't have the power to break molecular bonds.

"Mechanistically, it hasn't been shown that it can happen," Ansari said of the idea of non-ionizing radiation causing cancer or other health problems.

He feels confident that the risk, even if it exists by some unknown process, would be extremely low. So low, in fact, that scientists haven't been able to conclusively measure it.

Cellphones have gained widespread popularity in the past two to three decades, and during that time, there have been no notable increases in brain cancer rates.

"That's comforting that at least if there is a risk, the risk is not very high," he said.

Wearing a headset helps reduce your exposure

If you are still concerned and want to reduce your exposure to cell phone radiation, wearing a Bluetooth headset or headphones helps. (Both Ansari and the California Department of Public Health recommend this.)

Wired and wireless headsets emit less radio frequency energy than a cellphone, so if you want to really limit your exposure, keep your phone away from your body in a backpack or purse, and just plug your headphones in when you need to talk.