Answer to Question #11008 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
My husband keeps a gas mantle in his work van (a maximum of two mantles at any one time) as a check source for radiation detectors. It was wrapped and stored in a corner of the van with his other work tools. Will the mantle emit any radioactive substances and will we get contaminated as:
- My children ride in his van every day to and from the caregiver's house.
- We purchase and transport our groceries and foodstuff home using the van.
- We sometimes eat our meal in the van.
Please advise if the radioactive substance will pass on/transfer from one item to another item (meaning if the item was already contaminated in the van and I brought it home) and what is the best and most efficient way of storing the mantles?
You have nothing to worry about. The trace amount of radioactivity in gas mantles which use thorium is extremely small. However, because of the public's awareness and concerns, truly unwarranted in my opinion, thorium is no longer used in gas mantles, and has since been replaced with other elements such as cerium, which is not radioactive.
We are all exposed to about 3,000 µSv every year from many background sources, such as the sky (cosmic radiation), the ground (radioactivity in rocks and soil such as radioactivity from the decay of naturally occurring uranium and thorium), and even you, from radioactivity within your body. The largest risk from thorium-type radioactivity would be if you somehow ingested it, which is extremely unlikely. There are some gamma-type emissions associated with these types of radioactivity, but quantitatively they range from zero to a fraction of a percent, depending on how long and how close you may be to the source. Without actually knowing the radiation levels, I cannot make any reasonable estimates, but even my worst-case estimates suggest fractions of a daily dose due to background radiation. If you live in Denver, you receive twice as much background radiation than at sea level, and some medical x-ray or nuclear exams give much more than a year's worth of radiation dose, and these are also considered safe for the public.
Your anxiety is really unwarranted.
I am attaching several URLs from several organizations, some of which provide additional links, which may be helpful:
- The U.S. Environmental Protection Agency has an excellent and informative site.
- The U.S. Nuclear Regulatory Commission has a publication NUREG 1717 that discusses such products.
- An interesting site is the Oak Ridge Associated Universities website, which discusses gas mantles in more detail.
- And finally, I will refer you to our own Health Physics Society site.
Search on "gas mantle" for additional answers to your specific questions.
I hope this is useful information.
Orhan H Suleiman, MS, PhD