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Last updated 2001.

Air travel - radiation dose & measuring device

Radiation and the environment

Monitoring environmental radioactivity

Labelling of radioactive material

Shielding of bremsstrahlung radionuclides

Behaviour of C-14 and H-3 radionuclides

People working with x-rays

Occupational medical exposures

Patient x-ray exposure

X-ray exposure as a patient when pregnant

Radiation training videos

Mobile phones

Electicity transformers and power lines

Potential health effects of metal detector security devices


Air travel - radiation dose & measuring device

I am trying to find a product that could be be worn as a crew member (airline) to measure radiation exposure. Do not even know what you call it, but sure something like this exists somewhere. Any suggestions?? Thank you for your assistance if possible. KJ (USA)

Dear KJ

Thanks for your enquiry. The increase in cosmic radiation at the altitude for long haul flights is about 6 microsieverts per hour. This could be compared to the new lower limits for occupational exposure (recommended by the International Commission for Radiological protection, ICRP) of 20,000 microsieverts in a year. Please note that this is not a "safe" level of exposure, but a level above which the risk becomes unjustifiable year on year. Natural background exposures do vary, however, not only with elevation but also with latitude and most significantly with radon levels at home and at work. (When flying the radon level should be just about as low as you can get!).

Personnel dosimeters are devices used to measure the external dose an individual accumulates over a set period. There are various different types of dosimeter that are available. One that is particularly sensitive would be a "Luxel" - a relatively new device that has been developed by Landauer Inc. You could contact the company for more information by trying their website www.landauerinc.com. Please note that personnel dosimeters are not normally calibrated for cosmic rays, so there may be some problems over accuracy. <<<BACK TO TOP>>>


Radiation and the environment

What are the most harmful effects on the environment, from radiation? JE (USA)

Thank you for your enquiry, J. Quite a big question, short as it is. There are different types of radiation, such as microwaves and radiowaves, but I assume you are interested in ionising radiation. There are also both natural and artificial sources, but again I expect your concern is the latter. As a matter of fact, under normal circumstances, the natural far outweighs the artificial; however, the artificial has the greater potential for extreme concentration.

Artificial ionising radiation, such as from nuclear power, has virtually no effect on the environment itself. That is to say is does not cause the equivalent of acid rain, climate change or ozone depletion. As far as I am aware, the potential harm is really only to human beings - ie health effects. In the short term, harmful effects are mainly going to be those that arise from radiation used for medical exposures. In the long term, it could well be radiation from nuclear power programs. This is because medical exposures use instantaneous x-rays or short-lived radionuclides, whereas nuclear power also produces long half-life materials that therefore have the potential to accumulate. In addition there are the possibilities of accidents - both for medical sources (as has been seen with lost therapy sources), and nuclear power (Chernobyl for example)

Probably the greatest radiation risks to the environment are from nuclear weapons. Apart from their destructive capacity and extremely serious "nuclear winter" effects on the environment, residual radioactivities following detonation, or dispersal of plutonium from accidents, would seriously elevate background levels for many years. As an example, caesium-137 levels from atmospheric testing of nuclear weapons mainly in the fifties and sixties still significantly contribute to the worldwide background.

I hope the above at least partially answers your question. I replied to your email address - but there must have been an error in it , as the email was returned. <<<BACK TO TOP>>>


Monitoring environmental radioactivity

Please advise me how I can purchase a pertable sensitive radio setector for personal home use. I intend to use it to inspect level of radiation in air, food and drinks. Thanks SS (UAE).

Dear SS

Unfortunately it is not easy to look at radioactive contaminants in air, food or water. This is because there are 3 main types of radiation emitted from radioactive materials (alpha, beta and gamma rays) and each requires different detectors. Secondly, there are always natural radioactive materials present - radon daughters in air and potassium-40 in food in particular; this means you need equipment to be able to distinguish between the radiations detected. Lastly, there is the problem that we usually need very sensitive equipment to pick up the normally very low levels of artificial radioactive materials.

All this means that it is beyond what is affordable for use in the home, plus interpretation of results need some experience. There are, however, some simple devices on the market that could be used to look for the gamma from Cs-137 and Cs-134 in food at high levels after a nuclear event. Possibly an air sampler could also be used to draw air through a filter which could then be put on the device (you would have to wait 24 hours for the radon daughters on the filter to decay away). Cost is still quite high at about US$3000 or more. One place to look would be http://www.netechnology.co.uk/mini/html/page19a.htm

Hope the above is of some help. <<<BACK TO TOP>>>


Labelling of radioactive material

Please could you tell me if something containing a small amount of tritium should have a radiation hazard label, if so, what type? Thanks. AS (UK)

Dear AS

Thank you for your enquiry.

Whether labelling, and what kind of labelling, is required will depend on what legislation is applicable. In the UK, probably the most restrictive requirements will be under the Radioactive Substances Act 1993. This will apply to anyone possessing or disposing of tritium. At the present there is no exemption level for artificially produced radionuclides like tritium if they are in aqueous form. (There are Exemption Orders that cover tritium in various devices and at low levels in organic liquids.) Under RSA93, possession of tritum would then require registration and a Registration Certificate normally requires labelling of radionuclide/activity/date/etc and use of the "trefoil" symbol denoting radiation.

Other UK legislation would be the Ionising Radiations Regulations 1999 and the Radioactive Material (Road Transport) Act 1991. Both of these specify exemption levels. Above these levels labelling is required in a manner depending on circumstances. Links to the above organisations and some of the legislation can be found on our sister website www.radiation.org.uk

The above may appear awesome, but with more specific details the requirements may be clearer. <<<BACK TO TOP>>>


Shielding of bremsstrahlung radionuclides

I am looking for some information on shielding requirements for Beta therapeutic nuclides which also include some gamma emission such as Re-188, Re-186 and Sm-153. Can you point me to any literature (printed or web-based) that contains recommendations. Also I would like to know how to estimate how much bremsstrahlung is produce if I know the beta's energy and the Z of the absorber. Is there an equation to calculate this. Thanks for you help. GM (Austria)

Dear GM

There is a publication in English on bremsstrahlung which may be what you are looking for. Details can be found by going to www.hhsc.co.uk/hhscbks.htm (which can also be found on www.radiation.org.uk - one of our websites) and looking at publication 15.

Dose estimation is likely to be complex as thickness will initially increase and then decrease emitted bremsstrahlung. I have seen a report that, contrary to traditional wisdom, Pb impregnated perspex shields are good for nuclides like P-32 (high energy beta - 1.7 MeV max). The Pb encourages bremsstrahlung generation but this is more than compensated by the Pb absorbing the bremsstrahlung better than perspex alone. If you had a similar beta emitter with some LOW energy gamma, then the Pb would consequently be expected to reduce the gamma without increasing the bremsstrahlung. Hope the above is of some help. <<<BACK TO TOP>>>


Behaviour of C-14 and H-3 radionuclides

Where can I find information on which radioisotopes target which specific organs in the human body ? I have had a specific request relating to exposure of female laboratory workers to C-14 and H-3? Do either of these isotopes target the reproductive system specically? Many thanks, KP (UK).

Dear KP

Thanks for your enquiry. Targeting by C-14 and H-3 will depend on the biochemical nature of the compounds they have been used to label. Once the body has broken down these compounds (eg in liver, or cell mitochondria), then the radionuclides may behave in a more "generic" fashion.

If you are concerned about the reproductive system, then you will need to find out (if this is possible) to what degree the H-3/C-14 compounds themselves target the reproductive organs - and how long the compounds are likely to remain there. Once broken down, H-3 and C-14 do not specifically target the reproductive system - although during pregnancy they might be preferentially drawn to areas of high metabolism.

H-3 is usually of very low toxicity because of very low energy beta emmission, and because it generally disperses around the body (hydrogen being the dominant element in the body). However, as an example of targeting, if the H-3 is in use as a label in a DNA seeking compound (eg thymidine) then the beta energy is disproportionately dissipated in cell chromosones - which have a greater sensitivity to ionising radiation. To allow for this, the dose per unit intake for such compounds has sometimes been multiplied by a factor of up to 50. (For C-14, this particular effect is much less important. This is because the beta are more energetic and travel well beyond the cell nucleus - so ionisation across the cell is much more even and the chromosomes do not receive a disproportionate dose.)

For the "generic" behaviour of radionuclides like H-3 and C-14, the International Commission on Radiological protection (ICRP) issue authoritative publications. If you go to our sister website www.radiation.org.uk you will find both ICRP and other sources of information. By clicking on the ICRP logo and then selecting "Publications", you can find how to obtain ICRP68 - which would be the single most useful title. There is also information on a more comprehensive CD-ROM. Try clicking on "Interim Reports" at the bottom of the "Publications" page - you may find something of use for the particular compounds you are using. <<<BACK TO TOP>>>


People working with x-rays

What would you consider to be a safe level of annual exposure to x-ray radiation for people working with equipment emmiting such radiation every day? AMT (Singapore)

Thank you AMT for your question.

There are internationally recognised limits set by a body called the International Commission for Radiological Protection (ICRP) both for persons occupationally exposed and members of the public. These recommended limits were reduced in 1991. Most countries are now applying the new limits. (Both UK and Singapore introduced legislation at the beginning of 2000 to reflect these limits.)

For an occupationally exposed worker the limit for the whole body being exposed is 20,000 microsieverts in a year. (There are higher limits for parts of the body.) This is about 10 times what an average person would get from normal background radiation. However, unfortunately no radiation exposure can be said to be "safe" - just as, for example, there is no safe level for smoking. All we can say is that going over 20,000 microsieverts per year, for year after year, would result in a risk that is too high to expect an employee to take. (The ICRP say the 20,000 microsieverts can actually be averaged over 5 years, with no more than 50,000 microsieverts in any one year.)

Because no level, no matter how small, is totally without risk (nothing we do is totally safe), doses need to be kept as low as they reasonably can below the limits. In some cases x-ray machines can be put in shielded enclosures designed so that accessible areas will have radiation levels well below the annual limits - even if continually used. In other cases this is not possible, but precautions can be taken and operators wear a badge that will tell them how much dose is received. Experience shows that, unless accidents can occur, employees' doses are usually less than 10 % of the annual limits - even when they are working with x-ray equipment every day. <<<BACK TO TOP>>>


Occupational medical exposures

My sister is a Resp. Therapist (20+yrs). She works a 2 hosp. freq. She has to ambu a pt. during CAT. My question is why can she at one hosp. and the other cannot. They have to place the pt on a portable vent. Her eyes have been bothering her for quite some time, and recently found out she has a very over active thyroid. I would like some advice on this, as I am a very concerned sister. C (USA)

Thank you for your enquiry C. Apologies for not replying earlier - we have recently received an increased level of enquiries.

I have some difficulty understanding the question and am not too sure of some of the abbreviations. However, I gather your sister is located close to a patient undergoing CT (computer tomography) at one hospital but not at the other.

There are probably competing considerations which the hospitals have to try and balance (eg what's best for the patient and what's best for the staff). So it is possible different policies result. Also, the circumstances may not be identical. It is difficult to comment without knowing all the facts. You could try talking to the hospital safety office or consider talking to the state radiation control body (contact information may be available through the website www.crcpd.org).

The amount of radiation exposure is not likely to be very high, less than in an operating theatre where x-rays are in use. Frequency of exposure is a factor. If more than an occasional exposure is involved, your sister would benefit from having with a radiation monitoring device and lead apron. Positioning is an important consideration for parts of the body not protected by this apron - the bulk of the radiation is probably scatter from the part of the patient being x-rayed, and the level falls off rapidly with distance.

It is very unlikely that any problem with your sister's eyes are due to radiation. The main effect on the eyes is cataract formation, and this could only occur as a result of extremely high doses accumulated over the years. Latest international dose limits for the eyes are a maximum of 150 mSv in a year. While this is less than the 500 mSv for other single parts of the body, it is higher than the 20 mSv that applies to the body as a whole (mainly the trunk). Similarly, radiation is not likely to result in an overactive thyroid; in fact in severe cases radiation is sometimes used to treat overactive thyroidism.

It is nice that you are concerned for your sister, and it is a pleasure to try and answer some of those concerns. <<<BACK TO TOP>>>


Patient x-ray exposure

I was given around 8 or 9 times of x-ray shots within a year. Is that dangerous or what level will it be dangerous to my health. The x-rays were conducted on my chest and neck. I afraid that these exposures would affect my health. Could you give me some advise. Thanks.....FAZ

Dear FAZ

Thank you for your question.

Any x-ray exposure is assumed to carry with it a very small long term risk of cancer. However, the benefits from an exposure far outweigh the risk. Having 8 or 9 exposures in a year just means that the very small risks add up. If each one is giving you a benefit, therefore, then the number is not important. (For very high doses, as used in therapy rather than diagnosis, then it might be possible to reach thresholds at which short term effects may be seen.)

It is, however, always good practice to try and minimise the dose and area irradiated for each exposure, and to minimise the need for repeats. This is because it makes sense to minimise a risk, if this can reasonably be dose, even when the risk is already very small.

I don't know the conditions and purposes of your x-rays, so don't know the likely doses received. However, typical x-rays might be equivalent to the risk of smoking a few cigarettes, or the same sort of extra dose you get from a few hours of high altitude flying (increased level of cosmic rays). We are probably talking of a level of risk of cancer LESS THAN 1 in 100,000 per x-ray (about 1 in 4 or 5 of us contract cancer during a lifetime).

It is hoped that the above is of help. You may also be able to get further information from some of the links on our other website www.radiation.org.uk <<<BACK TO TOP>>>


X-ray exposure as a patient when pregnant

What would be the effects of exposure to a unborn child? ....... M (USA)

Thank you M for your enquiry.

The dose to a baby while still a foetus depends greatly on the location of the x-ray and the type of procedure, and probably the best person to speak to would be a radiologist. However, generally speaking, apart from when radiation is used to treat (eg radiotherapy) rather than examine a patient - the dose will be very small unless the x-ray beam is actually directed at the abdomen . Even when the beam is directed on the abdomen, the dose is in most cases still very low. (Nevertheless, good practice usually requires consideration of the time of the last period and/or provision of shielding of the abdomen - in order to further minimise the very small risks if there are no disadvantages in doing so.)

Exposure early in pregnancy, before cells have differentiated (fully specialised), may have less effect. Also, natural background exposures are in any case always present - and may vary from place to place by more than the exposure received from an x-ray. <<<BACK TO TOP>>>


Radiation training videos

Where can I find radiation protection training videos - i.e. basic knowledge for Classified Persons and more in depth subject matter for RPS's etc.? I have used the 'Radiation All Around Us' and 'Radiation FX' (with Carol Vorderman) but was looking for something more up to date. Can you provide some pointers please? PR (UK)

Dear PR

With regard to your enquiry on training videos, I would suggest (if you are not already aware of it) HHSC Books at http://www.hhsc.co.uk/hhscbks.htm This is included at the bottom of the list of references in www.radiation.org.uk (an RSS website).

I sometimes still use "Radiation All Around Us", but you are right about being out of date. Pity UKAEA have not made an update! I plan to provide some off-the-shelf training courses on the internet soon - the first (an introduction to radiation safety) will be downloadable free. <<<BACK TO TOP>>>


Mobile phones

Hi, can you tell me if you know anything about the safety of cellphones . Are they safe to use moderately. I know there was a 1992 study and something in 1996. Has there been anything recent? Can you please write back with any information. Thank you, A.

Dear A

Thank you for your question on the safety of cellphones (mobile phones). The World Health Organisation (WHO) is undertaking an "emf" project which covers all radiofrequencies including those of mobile phones. The project gathers data, organises meetings and publishes info. You can see one of their latest reports at http://www.who.int/inf-fs/en/fact193.html

In UK, the NRPB website links to a report issued earlier this year - http://www.iegmp.org.uk/IEGMPsum.htm

The question of how hands-free devices impact on exposure has been debated of late. One report suggests they can make things worse - http://www.emrnews.com/public_relations/hands_free_stories/financial_times_april2000.html while I have recently seen news of an Australian study which contradicts this and says they make things safer. (I can not find this report, but believe it is based on measurements of absorbed energy rather than field strength.)

Some current newspaper reports can be found at :- http://dailynews.yahoo.com/h/nm/20001123/sc/health_mobilephones_dc_1.html and http://dailynews.yahoo.com/h/nm/20001125/sc/health_mobilephones_dc_3.html

I wonder why mobile phones still have the aerial pointing upwards when this places it closer to the brain. Probably it is a hangover from walkie-talkies with their long aerials which had to be directed upwards for better reception. A downward pointing aerial on a mobile phone would be further from the head, and less of the transmitted energy would end up getting absorbed. <<<BACK TO TOP>>>


Electicity transformers and power lines

I need information for protection of my house from electricity transformer in the front of my house. AA (USA)

Dear AA

Thank you for your enquiry about the safety of the transformer in front of your house.

The dangers, if any, are still the subject of investigation. The World Health Organisation (WHO) is gathering data as part of their "International EMF Project". You can visit their site at http://www.who.int/peh-emf/ or you might find a question and answers site for power lines useful - the one they link to is http://iago.lib.mcw.edu/gcrc/cop/powerlines-cancer-FAQ/toc.html

You may also find some information at the National Radiological Protection Board (UK) site, (http://www.nrpb.org.uk). Examples are one dealing with measurements at transformer boundaries http://www.nrpb.org.uk/Nir-is2.htm and comments on a Canadian study http://www.nrpb.org.uk/R5-99.htm and a UK study of cancer in children http://www.nrpb.org.uk/R11-99.htm

I hope the above provides some reassurance. <<<BACK TO TOP>>>


Potential health effects of metal detector security devices

At work we are subjected to walk through a metal detector arbor and are wanded when it beeps, which happens every time. My question to you, is how much radiation is going through these? And shouldn't the company inform us of any health risks prior to making this company policy? Isn't the company who provides this service and the "security guards" who monitor this activity, responsible for the proper information if any questions are asked? I am still in my child bearing years, and I am concerned that I may be affected. If you could send me any information regarding this, I would certainly appreciate it. Thank you, DC (USA).

Dear DC

Thank you for your question. As you know the devices you mention are used routinely on many persons (eg at airports). The difference is, perhaps, that you are subjected to the devices more frequently.

These devices do not emit x-rays. X-ray devices are sometimes used for objects, but not routinely for people. What are produced are magnetic fields. Some information you might find useful is available at a World Health Organisation website dealing with what's known as the "emf project". This can be found at http://www.who.int/peh-emf/index.htm (or you can find it under "International" on our related website www.radiation.org.uk). If you click on "What is emf", you will see something about these security devices just over half way down the page under the heading "Electromagnetic fields in the environment". "Effects on pregnancy outcome" is mentioned about one third of the way down the page. Sources for more detailed information are indicated elswhere on the emf project site and under "static magnetic fields ..." at http://www.mcw.edu/gcrc/cop/static-fields-cancer-FAQ/toc.html

Yes, your employers should tell you if there were to be any recognised dangers. If you have not already done so, may be you can approach them and ask them what they do know. They may refer you to data from the equipment suppliers and/or Government sources. Hope the above is of some help. <<<BACK TO TOP>>>