Answer to Question #11446 Submitted to "Ask the Experts"

Category: Pregnancy and Radiation — Radiation workers/medical technicians

The following question was answered by an expert in the appropriate field:


I work with iodine-131 (131I) administered to cats every two weeks for three days at an animal hospital. My husband and I are planning to get pregnant soon, maybe in a few months or so. Should I stop handling these cats as a precaution before getting pregnant because of the radiation? If so, how long should I stop this work before trying to get pregnant?


I would recommend not working with cats after they have been administered 131I once you become pregnant. In additional information you provided, you indicated that you might administer medications orally, restrain the cat for various reasons, dispose of litter, etc. My concern is the potential for you to accidentally ingest, inhale, or otherwise take some of the iodine internally.

After administration, this type of iodine is in the cat's sweat, dander, hair, saliva, urine, and a little in the feces. In the first 36 hours, most of the radioactivity is excreted via urine so this will all be in the litter.

The concern for you when you become pregnant is that, at about 9–11 weeks, the fetal thyroid is forming and is very sensitive to radioactive iodine. Even a small amount of 131I taken in by the mother can have significant consequence for the fetal thyroid.

If you choose to continue working with these cats, I would recommend you wear full personal protective equipment when handling the cats or litter (or anything the cats have come in contact with). This means gloves (maybe two pair), disposable gown, face mask, and eyewear (mostly to make sure you don't touch your eyes with contaminated gloves rather than to protect your eyes from splashes).

Kelly Classic
Certified Medical Health Physicist

Answer posted on 17 January 2016. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.