Effects and Security Screening

Q

I reached into an airport x-ray screener that is used to see in to our carry-on items.  How much radiation exposure did I get?

A

There is nothing for you to worry about. Airport x-ray machines and similar x-ray machines used by federal and state agencies to screen briefcases and packages give much lower doses than x-ray machines in hospitals and medical clinics—almost immeasurable. They are designed this way because they do not have to see as much detail, are not designed for looking into very large objects, and are usually looking for things that really "stand out" on images (like metal).

In all likelihood, your hand was not in the actual beam, making your exposure much lower. Furthermore, the hands and feet are very radiation tolerant relative to the rest of the body.

Q

Does radiation from a security screening device, like those used in airports, affect the items that pass through them such as baby bottles, food items, plants, electronic devices (cell phone), or drug products (like injectable nitroglycerin for a heart condition)?

A

The radiation exposure from these devices is too low to affect any items passing through (other than certain types of camera film which can darken) even from repeated exposures.  Additionally, in case you were wondering, there isn't any residual radiation in exposed materials after the exposure is complete either.

Q

Does airport security x-ray screening have any effect for my pet?

A

The radiation exposure from these devices is too low to affect cats, dogs, birds, or other animals that need to be security screened. If it is just the pet carrier that needs to be screened, you can put the carrier on the conveyor belt and walk or carry your pet through the metal detector portal instead of having the animal go through the x-ray unit if that would make you more comfortable.

Q

Does radiation from a security screening device, like those used in airports, affect clothing if it passes through the screening a lot? I have a Gore-Tex^® jacket that gets screened quite a bit.

A

The amount of radiation to which the clothing, even the Gore-Tex^® jacket, is exposed is too small to degrade the materials. The manufacturers of these scanners indicate the radiation exposure to an item from one scan is about one-tenth the exposure we receive every day from naturally occurring radiation (commonly called background radiation).

Q

Can I put my hand inside a screening x-ray machine to get an x ray to look for injury?

A

No, absolutely not. These systems are not designed for medical diagnosis and will not provide appropriate image detail or contrast. I would suspect that in most states, this would be illegal. X rays of people should only be done with a doctor's order to do so.

Q

If the airport security screener stops the conveyer to observe the x-ray image for a longer time, does that mean the item on the conveyer gets more radiation?

A

The scanners used for hand luggage at most airports take short single-shot images of items. The radiation is turned on for the same fixed amount of time for each item. The images are digital and held on the screen until the next coat, purse, or other item is processed. Thus, if the screeners choose to look at the images for an extended visual analysis, no additional radiation is used. If the item is removed from the scanner and put back onto the belt for a second time, however, it will then receive additional irradiation. In other words, these x-ray scanners are not "fluoroscopic" in nature like the old machines from the mid-20^th century which were used to fit shoes, nor are they like angiographic or surgical x-ray machines. The scans are more similar to simple chest x rays, only performed using less radiation.

Q

Is it true that some walk-through scanners actually use x rays to screen people?

A

Yes, some of these are now being used in large international airports, such as Heathrow in London. There is very little radiation dose for a person passing through the scanner because they are not trying to see the detail of our "soft" tissues as is done in medicine. They are looking for items that will stand out pretty easily.

According to the American National Standards Institute, in its standard N43.17-2002 "Radiation Safety for Personnel Security Screening Systems Using X-Rays," the maximum effective dose an individual could receive when walking through this scanner is 0.01 millirem (a unit of radiation dose commonly abbreviated mrem).  For some perspective on the level of this dose, the annual effective dose each of us receives from background radiation is about 360 mrem; the effective dose from one chest x ray is about 10 mrem.

Q

I travel a lot (at least once or twice a week) and will continue to do so in the foreseeable future.  Obviously, I have to go through the metal detector at least twice for each trip.  What effect does this radiation exposure have on me in the long run?

A

The metal detector does not expose you to ionizing radiation, e.g., x rays; neither do the wands that are used for individual screening.  Metal detectors operate by generating a low-intensity magnetic field that passes from one side of the detector to the other. If metal objects pass through that field, the magnetic field will induce a second field in the metal object. Since that second field is a disruption of the first field, the detector senses the change and sets off an alarm. Magnetic fields are a form of radiation, but they are called "nonionizing" radiation. This means that magnetic fields do not generate additional, damaging radiation the way that ionizing radiation (such as x rays) does. Magnetic fields below a certain intensity are considered to be safe in that they will not cause any biological damage to an individual. As a reference, MRI (magnetic resonance imaging) is considered safe and uses much higher magnetic field intensity than a metal detector. In summary, because of its nonionizing properties, the magnetic field generated in a metal detector will not cause harm to persons even with routine and/or repeated scanning. 

Q

I work for a major airline and will be required to spend eight hours a day near the new baggage x-ray machines (the big ones that I think are CT machines) that TSA (Transportation Security Administration) uses. We have been given a handout saying that TSA has determined that the machines are not dangerous and that we do not need film badges. How can anyone say working near radiation is not dangerous if it is not monitored in any way?

A

Some of the newer x-ray machines used to scan checked luggage use computerized tomography (CT) technology—just like those used in medicine. The main difference between the two types of use (security at airports and medical diagnosis) is that the machines used in airports have more shielding to stop the scattered radiation—nearly the entire luggage belt is shielded where, in medicine, the patient table is not shielded—and they subject the baggage to lower doses because the image does not need to be as clear as it does for a patient.

Someone standing next to the unit in airports would receive little, if any, radiation exposure. Radiation emitted around a piece of equipment when it is operating is determined at the manufacturer and, sometimes, checked by the purchaser. A manufacturer must assure the equipment is operating within federal regulations that govern x-ray equipment, which in this case is 0.5 mR/h at 5 cm from the unit (mR or milliroentgen is a unit of radiation exposure) though performance studies of the equipment indicate that the average exposure rate was about 0.08 μR (microroentgen, one-one thousandth of a milliroentgen) per scan (NCRP Report 95). Purchasers can use the manufacturer's assurance and/or can perform their own surveys on the equipment. The dose to the luggage is very low and there is no detectable radiation outside the machines according to one manufacturer.