Monthly Archives: October 2016

Dear Dr. Zoomie – I’ve got a hot lab and I was told I need to develop a response plan in case someone gets skin contamination. I was thinking soap and water; is there anything else I should include?

Skin contamination doesn’t happen often but if you work with enough radioactivity – especially in liquid form (as in a hot lab) it’s going to happen from time to time. And it doesn’t mean that people are being careless and sloppy (well…sometimes it does, but not always); sometimes we just make mistakes. I’ve had skin contamination myself at least a couple dozen times – mostly just random splatters here and there – and every time it’s cleaned up fairly quickly with soap and water. But let’s back up a little bit and talk about what goes into dealing with skin contamination. Specifically, you need to have a procedure to follow, you need to know how to clean up the contamination (and how to know when you’re done cleaning up), and you have to know how to tell if any follow-up is required. Let’s take these one at a time.

Commonly missed areas of the hand during decontamination

Your skin contamination procedure doesn’t have to be very complicated; in fact, it only needs to have a couple of parts. It should:

1. Define what’s meant by skin contamination. For example, you might define skin contamination as the presence of any contamination above background or you might decide that contamination levels have to exceed a certain limit (100 cpm above background, for example).
2. Describe the steps to be taken when a person is contaminated. For example:
   1. Contact the Radiation Safety Officer at the earliest opportunity.
   2. Perform a count rate survey over the contaminated area and write down the number of CPM.
   3. Start to clean the contaminated skin in the nearest sink or at the nearest decontamination station.
3. Discuss cleanup techniques (more on this in a moment).
4. Determine when to call for outside assistance and/or follow-up (more on this later as well)
5. Document what’shappened.

Cleaning up contaminate skin isn’t always simple, but it can be. For example, most cases of minor skin contamination can be cleaned up with soap and warm water. In fact, every time I’ve had skin contamination, soap and water has worked for me. It’s also possible to wipe down the contaminated skin with baby wipes or other cleaning-type wipes. Wiping down with a damp rag or sponge will often do the trick as well, and other specific circumstances (or specific compounds that you might be using) might call for more specialized products. No matter how you choose to decontaminate a person there are a few rules of thumb to keep in mind.

• Don’t do anything painful or uncomfortable. For example,
  • Don’t use hot or cold water – keep it cool to warm.
  • Don’t scrub with harsh substances (e.g. steel wool, scrub pads, wire brushes, etc. – and don’t laugh; I’ve seen all of these used).
  • And above all, don’t do anything that will draw blood. Your skin acts as a pretty good barrier, keeping contamination out of your bloodstream – if you do something that breaks the skin then you’re simply scrubbing contamination into the blood, which is never a good idea.
• Count for contamination every several washes or wipes. As long as contamination levels are dropping then whatever you’re doing is working and you should keep doing it. If contamination levels stop dropping then what you’re doing is no longer working and it might be time to try something else.

You also have to understand when it’s time to follow-up or call for help. And “call for help” is not necessarily as dramatic as it might sound – that can simply mean calling a consultant. There are a number of possibilities in this category – here are a few of the more common.

• For example, you might consider performing a thyroid count for every case of skin contamination with radioactive iodine, or performing urine bioassay if skin contamination exceeds, say, 10,000 cpm (you’ll have to determine what these “trigger” levels are for the nuclides you’re using).
• You might also consider contacting a consultant to determine the possibility of uptake and/or to calculate skin dose if skin contamination exceeds a given count rate.
• You (or, more likely, your consultant) might have to calculate radiation dose to the skin if contamination levels are sufficiently high. Duke University has an online calculator to help you with this. For more complicated cases, you can also use a program called Varskin, which is quite possibly the best software available for this purpose.
• You’ll also have to contact your regulators if you (or a consultant) determine that a person has exceeded 50 rem to the skin.

Finally, you’re going to have to document what happened and how you responded to it. Start with a short description of the circumstances causing the skin contamination (e.g. liquid splashed on the skin) and write down the number of counts you measured as well as the instrument used for the measurement (e.g. 45,000 cpm measured with a GM pancake probe). You should also briefly describe the decontamination procedure (e.g. washed with soap and water for five minutes) and the results (e.g. contamination reduced to less than 100 cpm above background). And note any follow-up measures or samples that were taken (e.g. performed urinalysis to check for uptake) and the results.

Finally, let’s put all of this in perspective. There are times that skin contamination can be damaging – the skin can be harmed from a sufficiently high radiation dose. But most of the time skin contamination is more of a nuisance than a risk. You have to take it seriously; you need to decontaminate the affected area, you need to try to get an accurate count rate to see how bad it might be, you need to document everything, and you need to know when to call for someone to give you a hand. But you don’t have to panic! Take a deep breath, break out your procedures and your supplies, and work methodically and you (and the person who was contaminated) should be OK!

Dear Dr. Zoomie – my wife is pregnant and she needs to have an x-ray. Is this going to hurt the baby? Or should she wait until after she delivers? How does radiation affect pregnancy?

My kids look perfectly normal – in my humble opinion maybe even a tad better than normal. This became an issue, actually, in the months following the 2002 arrest of Jose Padilla on charges he was plotting to set off a “dirty bomb.” How it became an issue is that I was interviewed by a reporter interested in the reproductive effects of radiation – she was wondering if we could expect to see legions of children born with birth defects in the aftermath of a radiological attack. I spent a fair amount of time helping her to understand the basic science behind why this was unlikely to happen and then, to lighten the conversation a tad, threw in the line “let’s face it – if parents have strange-looking kids they should probably blame the in-laws and not the radiation.” Guess what quote she used. For a few weeks I was getting e-mails from colleagues around the world asking to see photos of my kids. And I’m happy to say that in spite of my years working around radiation, my kids look perfectly normal. At least as close to normal as we can expect from teens….

The point here is that the reproductive effects of radiation are exaggerated to the point of irrationality – more so than most other reproductive hazards. True – radiation can cause birth defects and it has been shown to induce mutations in animals. But the amount of radiation required to cause birth defects in humans is substantial (at least 5 rem or 50 mSv to the fetus) and the medical literature has not noted a single instance in which pre-conception radiation exposure to humans has caused birth defects when the woman eventually conceives. And if more people – physicians included – really understood these points there would be far fewer worries.

Consider – the BBC documentary Nuclear Nightmares (which was about radiation phobia) stated that the Soviet government performed a few hundred thousand abortions on women exposed to radiation after the accident and others have stated that there were at least 100,000 abortions conducted in Europe due to fears about the reproductive effects of radiation exposure. It is almost certain that few – if any – of these abortions could have been justified by the radiation exposure alone. I understand that the numbers cited are not from the peer-reviewed literature and that they might be high. But the 2006 report by the World Health Organization concluded that after 20 years there had been fewer than 100 deaths attributable to radiation exposure from the accident (including radiation-induced cancers) and projected that as many as 10,000 people might eventually develop cancer from the accident – even if the WHO’s worst-case estimates come to pass and even if the abortion numbers are over-stated by a factor of 10 we will still find that fear, ignorance, and misinformation was deadlier than the accident itself. This is tragic.

As a radiation safety officer I calculated nearly 100 fetal dose estimates, usually when a pregnant woman was involved in a car crash and, while unconscious, received the “trauma series” of x-rays from head to foot, possibly followed by CT or even fluoroscopy. Sometimes when the woman woke up she told the doctor she was pregnant, sometimes she didn’t know this herself for another few weeks. In either case, our policy was that I was to be informed so that I could perform fetal radiation dose calculations and write a letter explaining the results to the woman’s OB/GYN. There was not a single case in which the fetal dose estimate was high enough to warrant taking any actions at all, even though some of the women had been advised they might need to terminate their pregnancies. And I was not alone in this – the Health Physics Society runs a wonderful feature on their website (Ask the Experts) that has a section for radiation and pregnancy. Over the last decade or so they have accumulated hundreds of inquiries on this topic and almost none of them warranted any concerns at all. Sadly, many physicians in the US are taught that radiation can cause problems with pregnancy, some of them might vaguely remember a dose of 5 or 10 rem (50-100 mSv) but don’t know the fetal radiation dose from the radiation they might prescribe, and are then told little more. Is it any wonder they sometimes give bad advice?

For the record, the Centers for Disease Control and Prevention maintains a web page that includes information on the impact of prenatal radiation exposure aimed at parents and at physicians. CDC includes a table that summarizes the impact of prenatal radiation exposure based on the post-conception age and the fetal radiation dose – they conclude that for any radiation exposure that occurs less than 2 weeks into the pregnancy and for any fetal radiation exposure of less than 5 rem (50 mSv) there is no need to take any actions at all. To put this number in perspective, it can take tens of x-rays or a few CT scans that image the uterus (the exact number depends on the x-ray machine being used, the amount of tissue between the x-ray beam and the fetus, and a number of other factors) to reach this level of fetal exposure. And for x-ray exposures that do not image the uterus – a chest or head x-ray for example – the dose is even smaller. But believe it or not, I even took a call from a woman who had dental x-rays wondering if she should take her physician’s advice to have a therapeutic abortion.

Having said all of this I don’t want to make it sound as though I’m advocating throwing caution to the winds – according to the ALARA principle (to keep radiation exposure As Low As Reasonably Achievable) we should not simply run up the dose through unnecessary medical imaging – I agree with the goals of the Image Gently initiative to help reduce pediatric (and prenatal) radiation exposure. But I would suggest that if the mother’s health or life are at stake then physicians should avail themselves of the tools they have without letting unwarranted fears deny them access to valuable diagnostic information. And the physicians need to remember that – before giving any medical advice about the pregnancy – fetal radiation dose should be calculated by a qualified and competent health physicist or medical physicist. Radiation health effects depend on the radiation dose – absent a solid radiation dose estimate it simply is not possible to give good, informed advice to the prospective parents.

The sad fact is that the programs that train our physicians – not just in the US by the way, remember the numbers from Europe – are not doing a good job of teaching their students about the impact of radiation on their patients. I discussed this in an earlier blog, where you can find references on this point. This is ironic given that, according to the National Council on Radiation Protection and Measurements, our exposure to medical radiation had increased dramatically in the last few decades. Given our society’s heavy reliance on radiation in industry, medicine, research as well as our dependence on nuclear power I would like to think that our physicians can be better prepared to give good advice to their patients about the effects of the radiation to which they are unavoidably exposed, just as I would like to think that the public can be provided with solid information so that they can participate more fully in the process of making decisions about radiation exposure.

To wrap this all up – and bring us back to your original question – a single x-ray, even a single CT scan, doesn’t give enough radiation dose to the developing baby to cause birth defects. Remember, too, that there’s a reason the doctor is prescribing an x-ray for your wife – he needs diagnostic information to help keep her healthy. There is a risk to your wife – and your developing child – from not having this information. Since your baby’s health depends on that of your wife, there’s a risk in NOT getting this diagnostic information. Chances are that the risk from not having an x-ray or CT scan (due to lack of diagnostic information) is higher than the risk from the x-ray images. In other words, if the doctor feels that an x-ray is needed then it makes sense to follow the doctor’s advice.