Monthly Archives: July 2014


What Do First Responders Need to Know for Radiation Safety Training?

Dear Dr. Zoomie –

I’m a firefighter and we’re starting to prepare for radiological emergencies. What sort of stuff do we need to know? Is there some sort of accepted standard for training or certification? Where can we get trained?

Tough questions – and a lot of ground to cover. So let’s get started with some of the relatively easy parts and work our way from there.

FDNY EMS Conduct a Dirty Bomb Drill

FDNY EMS Conduct a Dirty Bomb Drill

First, there is no standard at the moment for training emergency responders for radiological emergencies, and there are no certification programs at present. There are a number of on-line training programs that can go over some of the basic information, but that will only take you so far – to really be effective you need to have in-person training that includes hands-on work as well as the classroom stuff. As far as where you can receive this training, Nevada Technical Associates put together a training class for the Fire Department of New York – I’ll describe this in a moment – that went over very well.

As far as what you need to know…since there is no standard at the moment I can only describe the curriculum that was put together for FDNY – since they had a huge input into the training, the curriculum not only covers what NTA felt was important, but also what the firefighters felt needed to be covered. As an aside, this training is similar to training that NTA instructors have given to other emergency responders elsewhere in the US.

FDNY Firefighter

A FDNY firefighter rushes to help victims during a simulated bus bombing, at FDNY Fire Academy on Randall’s Island, N.Y

Any radiation training, no matter who the audience is, has to include radiation fundamentals – what types of radiation are there and what are their properties, how does radiation affect our health, how can we detect it, and so forth. But emergency responders have different information needs than others – a radiation safety officer needs to be able to calculate radioactive decay, for example, but an emergency response isn’t likely to last that long so there’s no need to go through the decay calculations. Similarly, it’s helpful to understand the concepts of time-distance-shielding to reduce radiation dose, but it’s not necessary to go into all the calculations for emergency response efforts. So the “radiation fundamentals” part of the training should concentrate on the basic principles – the practical stuff – but there’s no need to get into the mathematical nitty-gritty.

Another part of the classroom part of the training should involve discussing different types of radiological and nuclear emergencies – what might happen during a dirty bomb attack, what happened at Chernobyl and Fukushima (and what might happen during a US reactor accident), as well as what a responder might see during a small-scale event such as a fire in a hospital’s nuclear pharmacy or during a vehicular accident involving radioactivity. Finally, the different places where radioactivity is used (e.g. industrial radiography) and the types of radioactive sources used in these places can help the responders to understand the risks they might face and how to deal with them. And then, on top of all this, responders should also know which regulations apply to their work and how to comply with them.

Firefighter Decontaminates a Soldier

A firefighter, left, with the Tulsa Fire Department decontaminates a U.S. Soldier assigned to the 63rd Civil Support Team

OK – so that’s the classroom part, but there’s still a practical side of the training as well. Responders have to understand how to use radiation instruments to perform surveys, how they respond to a variety of radioactive sources, how to screen people with both hand-held instruments and portal monitors, how to decontaminate themselves and others, and so forth. And ideally there should be some sort of practical exercise where the responders tackle a simulated radiological emergency – suiting up, conducting surveys, mapping radiation and contamination levels, and so forth; as well as tackling some of the “managerial” decisions such as assigning stay times, determining what sort of protective gear to wear, and so forth.

All of this came out to about 40 hours of training – the same length of time that’s normally spent in the NTA Radiation Safety Officer class.

Is Food Irradiation Safe?

Hey Dr. Zoomie – what’s the big deal with food irradiation? Is it safe, or is going to turn me into a lizard or something?

My mother used to work as an epidemiologist, investigating outbreaks of food poisoning. She told me once that if all food was irradiated her job would be mostly checking up on people who left their potato salad out too long at picnics. Food irradiation has been in use for over a half-century – it looks to be a pretty effective way to help make food safer. But first, let’s back up a little bit to talk about how it works.

Irradiated Fruits & Vegetables

Irradiated Fruits & Vegetables

High levels of radiation are dangerous, not only to humans, but to microbes as well. The idea is that blasting, say, a pound of ground beef with withering doses of radiation should kill off any microbes that might otherwise make us sick. Many microbes are fairly hardy, thought, when it comes to radiation – we have to expose the food to very high doses of radiation to make sure it’s sterilized; doses that would be fatal to humans many times over.

There are a few ways to produce such a high radiation dose. One way is to use extremely high levels of radioactivity and the other is to use very high-energy electrons to create x-rays or to directly irradiate the food. The last of these – directly bombarding food with high-energy electrons – is fairly simple; the electrons hit the microbes and kill them. The problem is that even the highest-energy electrons can only penetrate about a half inch into food – anything that’s more than about an inch thick (since it can be irradiated from both sides) will have area that can’t be reached by the electrons. The other methods – using gamma rays or x-rays – are a bit more effective since these can penetrate all the way through fairly thick foods to reach every bit of them.

Growth of E Coli

Growth of E. Coli Bacteria

So the radiation can penetrate into the food to make it safe, but a lot of people are concerned that the treatment itself might affect the food, making it unsafe. The thing is, these worries are unfounded – the benefit from killing off hostile microbes (such as the E. coli and salmonella that have caused a number of food poisoning outbreaks) far exceeds any negative effects. Here’s why.

First, irradiated food does not become radioactive – in fact, irradiating anything with gamma rays, x-rays, or even electrons is physically unable to cause things to become radioactive. Think about the lights in your home – when you turn the lights off at night your furniture doesn’t glow with the stored energy. And when you get off the table after having an x-ray taken you’re not emitting radiation either – just as food irradiation doesn’t make your food radioactive.

That’s not to say that there aren’t any chemical changes in your food when it’s irradiated. Radiation is known to cause chemical changes – it’s the whole subject of the field of radiochemistry. As one example, radiation exposure can cause chemical bonds to break, turning water into a mixture of hydrogen and oxygen. Other chemicals can form as well – especially in foods that are fatty or oily. But you have to remember that cooking also causes chemical changes in food – especially barbequing and grilling out. So the question shouldn’t be “Does irradiation cause chemical changes in the food” so much as “How do the chemical changes caused by irradiation compare to those caused by cooking?” And when it comes down to it, while food irradiation dose cause small chemical changes in the food, they pale in comparison to what happens when you put food on the grill. The bottom line is that food irradiation has been tested for over a half-century – and has been in use for about that same amount of time – and no credible studies have shown it to be any more dangerous than regular cooking.

It’s easy to say that food something is safe but somewhat more difficult to prove it. In this case, food irradiation has been studied extensively by the International Atomic Energy Agency and by the US General Accountability Office – both reputable organizations. These studies were pretty clear that food irradiation is safe and that the benefits far outweigh the risks. There have been some who have challenged these findings, but the science is not on their side.

Deadly Foodborne Pathogens

31 of the most important known agents of foodborne disease found in foods consumed in the United States each year cause approximately 9.4 million illnesses, 56,000 hospitalizations, and 1,400 deaths each year.

The bottom line is that food poisoning harms and kills people every year. How many times have we heard about illness linked to tainted chicken, ground beef, or farm vegetables, and how many people have died from these outbreaks over the years? By comparison, irradiated food hasn’t killed anybody, and there’s no telling how many people it’s saved.

What is Instrument Calibration?

Dear Dr. Zoomie –

I keep hearing about instrument calibration and don’t quite know what that means. Can you tell me what it is, when we have to do it, and whether it’s something I can do myself or should hire a contractor?

Let’s start off with why we have radiation instruments at all – it’s because we have no way of sensing radiation ourselves. No matter how high the rad levels are, you won’t feel your skin tingle, you won’t get a strange taste in your mouth, and you certainly won’t see or hear anything. That’s why we have instruments – to make up for this deficit in our senses. So if we’re using instruments to tell us whether or not we’re at risk – or even just to meet regulatory requirements – it behooves us to make sure that the instruments are working properly and to make sure we can trust their readings. That’s what calibration is for.

So calibration makes sense from a practical perspective, but it’s also a regulatory requirement – you’re required to perform a yearly calibration on all radiation instruments that are used for health and safety purposes or to perform surveys used to meet regulatory requirements. So every one of your radiation meters that’s used for routine radiation or calibration surveys has got to be calibrated every year. You should also have your instruments calibrated anytime they undergo extensive repairs – changing the batteries or cables is OK, but replacing probes or repairing the inner workings calls for calibration to make sure it’s still working properly.

If you’ve got a lot of radiation meters you might want to calibrate them yourself, but you’ll need to amend your radioactive materials license to let you do so, you’ll need to purchase the appropriate equipment, and you’ll need to get trained up so you can do it properly. Unless you have a few hundred instruments or more it probably doesn’t make sense to go through this process – but if you have a lot of instruments, calibrating them in-house can save you enough money to make it worth considering.

If you only have a few instruments you should send them out for calibration. Here you need to be careful to send them only to a facility that’s licensed to do the calibrations – most of the major instrument manufacturers can do this, but there are a lot of other facilities as well who can help you out. Doing an on-line search for “instrument calibration services” will give you a bunch of options; you can also look through the companies listed under Instrument Calibration Services in the Affiliates section of the Health Physics Society’s website (http://hps.org/aboutthesociety/affiliates/services.html).

One last thing – in addition to the annual calibrations there are quick and simple checks you should be performing every day that you use your instruments. Check to make sure the batteries are charged (many meters have a “Bat Test” button or switch position), make sure the meter’s physical condition is OK, and (for contamination detectors) check the meter for proper response against a check source to make sure your meter reads within 20% of the expected reading. For this one you can purchase a “button source” that can be mounted on the side of the meter; when your instrument is calibrated the calibration certificate will include information on the expected count rate. So, for example, if the expected count rate is 1000 cpm, you should get a reading that’s between 800-1200 cpm when you do the response check.

How Do You Read a Radiation Instrument?

Dear Dr. Zoomie – I bought a radiation meter and I’ve been making some measurements but I have to admit I’m not sure what they mean. The numbers are always going up and down a little bit and I’m not sure why.  When should I be worried? And shouldn’t my meter always read zero unless there’s radiation around somewhere?

You know, you’ve put your finger on one of the most important aspects of using radiation instruments – unless you know what the readings mean you’re just looking at numbers. Sort of like looking at your speedometer and not knowing if it’s reading in miles per hour, kilometers per hour, feet per second, or what.

One thing to remember is that there is always going to be natural background radiation that’s registering on your detector. So you should always get something registering on your meter. If you’re reading radiation dose rate then natural background readings should be anywhere up to about 100 microR/hr (µR/hr) or up to about 0.1 mR/hr – a µR is one millionth of a rad and one thousandth of a milliR (mR). If you’ve got a contamination meter then you’ll be making readings in counts per minute (CPM) or counts per second (CPS). Background count rate can vary a lot depending on what sort of radiation detector you’re using. With a GM it can be as low as just a few tens of CPM (1-2 CPS) or as high as a few hundred CPM (2-3 CPS); with a scintillation detector background count rate can be from several hundred to several thousand CPM (10-100 CPS).

A general rule of thumb is that background radiation levels can vary by up to a factor of 2 or 3 from moment to moment so if you see your count rate or dose rate spike up momentarily it doesn’t necessarily mean anything. Think of when you’re driving with your car on cruise control – if you look carefully at the speedometer (don’t do this unless somebody else is behind the wheel, by the way!) you’ll see that the speed will drift slightly up or down from time to time, but it never drifts very far from the set speed. You don’t worry that your cruise control is broken unless the speed changes considerably or changes for an extended period of time. So if your GM pancake probe has a normal background reading of 50-60 CPM and is fluctuating between, say, 40 and 70 CPM then there’s nothing to be concerned about. But if it goes up to 150 CPM and stays there then you might have found something radioactive. By the same thinking, if you normally see radiation dose rates of, say, 25 µR /hr or so, it’s not surprising to see your readings fluctuate between, say, 10-50 µR /hr. If they go up to 75 or 80 µR R/hr and stay there steadily then, again, you might have found some radioactivity.

Just because you find elevated readings, though, doesn’t put you at risk. In fact, any dose rate that’s in the µR/hr range is going to be fairly harmless, and there are a number of places on Earth where natural radiation levels are hundreds of µR /hr. If dose rates rise into the mR/hr range (remember that 1000 µR = 1 mR) then there’s still very little (if any) risk, but regulations start to come into play – if dose rates reach 2 mR/hr then there has to be some sort of restrictions (barriers, for example) to keep the public out of the area. But radiation dose rates don’t become potentially dangerous until they rise into the R/hr range (1000 mR = 1 R).

Count rate readings can also vary considerably, and they can be fairly high without posing a risk to you. As one example, after the Fukushima reactor accident the Japanese government didn’t require that people be decontaminated until they had over 100,000 CPM of skin contamination. So even if you get a reading of a few hundred CPM, while it might mean that you’ve found some radioactivity, it doesn’t mean that it’s dangerous. But that being said, any count rate that’s more than three times as high as normal – and that remains elevated rather than just spiking and dropping back down again – should be looked into to see if there’s a problem.

What do I do if I see that my readings have changed?

There have been some videos posted online that show people making radiation measurements and commenting on how the radiation levels seem to be increasing. It’s not uncommon for these people to be worried about the increases that they see; even to think that they’re seeing evidence of dangerous levels of radioactivity from the Fukushima reactor plant. In reality, it’s not nearly that dire. For example, some kinds of rock contain higher levels of radiation than others – if you’re walking through a city and walk past a granite building (or if you’re outdoors and walk past a big granite rock) you can see your radiation levels and count rates increase as long as you’re in range of the building or rock formation. And some types of clay contain more radioactivity than others – if the soil you’re walking over has a change in its composition then you can also see your levels increase. And for that matter, since bricks and concrete contain clay, brick walls or buildings – even brick sidewalks – can cause your readings to increase as well. The bottom line is that there are a lot of very innocent reasons for your radiation dose rates and count rates to increase and you don’t necessarily have to worry just because your readings go up a bit.

The thing to do is to try to figure out why they’ve changed. Say, for example, you notice your readings have gone up as you’re walking along outside. Stop and take a careful look at your detector and see if they stay elevated or if they fluctuate up and down. If they stay elevated, take a look around to see if something has changed – maybe you walked from an asphalt road to a concrete stretch of pavement, perhaps you walked next to a granite wall, or maybe you’re near a hospital (many hospitals have nuclear medicine, radiation oncology, and x-ray departments). Walk back the way you came to see about where the rates started to increase, then continue walking the way you were going to see if they start to go down again – by doing this you can figure out where the higher readings are coming from. If you can see a reason for the readings to be higher (different types of buildings, paving materials, etc.) then chances are that you’ve found the reason your readings have gone up. Another reason to see elevated readings would be a nuclear medicine patient close to you – these factors (changes in soil, rock types, buildings, and nuclear medicine patients) account for virtually every change in radiation levels you’re likely to come across.

Finally, remember that having a radiation survey instrument doesn’t mean that you’re a radiation professional. Figuring out exactly what your readings mean can be tricky, and sometimes even experienced professionals can be stumped. If you find elevated readings that you can’t figure out it doesn’t necessarily mean that you’re at risk or that you’ve found evidence of a radiation accident. If you’re confused by your readings you should write down what your readings are and exactly where you got them and then try to get in touch with a radiation safety professional. If you’re near a large teaching hospital or a large university you can contact the radiation safety office; otherwise you can contact your state radiation regulators to let them know what you found. And under no circumstances should you go into an area where the dose rates are higher than 2 mR/hr, nor should you try to recover radioactive materials yourself – these are jobs for radiation safety professionals.