25 January 2013

Pregnancy to pacemakers: Safety around high magnetic fields

Here's what those gauss lines marked on the floor mean — for you and for the folks allowed inside them.

By Amy Mast, This email address is being protected from spambots. You need JavaScript enabled to view it.

One thing we stress to visitors when they take tours of the lab is the power of our world-unique magnets. High magnetic fields can twist metal, create explosions, send wrenches flying, and in the experiments we conduct, test the limits of the laws of matter.

Gauss linesGauss lines outside a magnet are marked on the floor with yellow tape. It's not surprising, then, that a casual visitor would wonder about how magnetic fields affect the things they're carrying with them, such as cameras, or credit cards, or the things inside them, such as pins, pacemakers and offspring.

First things first: touring the magnet lab is not dangerous, or we would not do it. We always err on the side of caution, and visitors are required to stay inside clearly marked lines. Around each magnet, taped off circles marked the magnet's gauss lines. When the magnets are running, visitors are not allowed inside the gauss lines.

But what about the researchers and Magnet Lab staff who walk past that line every day? Here's what those gauss lines marked on the floor mean — for you and for the folks allowed inside them.

Sweating the small stuff

Lots of us have metal inside us, whether it's a rod inserted to support a bone or fillings from your Pop Rocks days. Do research magnets pose a threat to those bits of metal?

Most pins, fillings and other small metal items you've collected over time aren't going to respond to our magnetic fields. The items are small, the fields are relatively weak, and a tour participant with a pin in his knee won't feel a thing. A Mag Lab employee working inside the gauss lines with the same pin may feel a twinge, but his knee is definitely not going to be drawn to the magnet.

Visitors with pacemakers are asked not to step inside the magnet cells at all. Pacemakers, which regulate the rhythm of the heartbeat using electrical signals, can be vulnerable to fringe fields — rogue bits of weak magnetic field occurring outside the gauss lines. While it's too small to bother anyone else, it could disrupt the operation of such a delicate device.

The lab's resident expert in all things safety, Angela Sutton, says that workers who've been in a machine shop environment for a long time should stay away from operational high-field magnets. Many machinists unknowingly collect very small particles of metal in their eyes over time. Because the eye is so porous and the slivers of metal are so small, a high magnetic field could cause the metal to suddenly, um, dislodge.

Debit-card danger?

Aside from being extra cautious about our visitors' health, another reason we don't like our visitors to step too close to the magnets is because we care about your wallet. That little strip on the back of your credit card — the one that connects you with groceries and gas — is a magnetic strip, and it stores information that makes your purchases possible. High magnetic fields can wipe out that information. Some lab employees, neglecting to remove their wallets from back pockets on a busy day, are on their second, third or even fourth debit card.

Electromagnetic technology is also present in digital and video cameras, and while our visitors are welcome to take all the pictures they like, journalists who venture beyond the gauss lines when a magnet is running must take extra precautions to make sure they don't erase all the pictures they just took. Get too close to a magnet, and you'll actually feel the magnet tugging the camera from your hands.

For that reason, common tools you'd expect around a big, complicated magnet, like wrenches, are conspicuously absent when its field is fired up. You'd have to be pretty close to the magnet to see tools flying, but Magnet Lab employees use extreme caution nonetheless — safety and very expensive equipment are at stake.

Baby on board?

One question I used to get over and over during tours, as I waddled, pregnant, in front of guests, was "Aren't you scared for your baby in the high magnetic fields?"

It hadn't occurred to me to be scared. After all, the fringe fields created by our magnets are clearly marked with tape on the floor, and I wasn't climbing on top of them to eat my lunch or anything. But in the name of caution, I took the question to my doctor, who said she'd research the answer and give me a call.

She called back a week later, offering, "I've got no idea."

Fortunately, the lab has in-house expertise available in the form of Assistant Scholar Scientist Amy McKenna and graduate student Brandi Ermann, both chemists. They women worked repeatedly and in close proximity to high magnetic fields during their pregnancies, though, like all the lab's researchers, they took steps to minimize frequency and duration of exposure. Both women have borne perfectly healthy children.

"I never came across a study that dealt with the magnitude of the magnetic fields that we see here," said Ermann. "One of the things that makes you not as concerned is the shielding that most of the magnets are under. Even though you have a high magnetic field, the amount of exposure that you're coming into is as minimal as it can get."