Answer to Question #12592 Submitted to "Ask the Experts"

My cat had radioactive iodine treatment a week ago. She was sleeping on a towel on a chair in my apartment two days after her treatment. Later, I was sitting on this towel. Is this towel radioactive? Did I expose myself to radiation after sitting on it? I am worried.

Let me summarize my response right away by saying that I believe there would be no measurable radiation dose from sitting on a towel upon which your cat sat.

In this "towel scenario," the concern is whether your cat could have deposited a significant enough amount of radioactive materials onto the towel to result in a measurable radiation dose to you. When treating the cat, the facility is required to hold the cat for a number of days to allow most of the radioactive material not taken up by the thyroid to be eliminated by the cat (through the urine). The facility is regulated/licensed by a state or federal entity which requires that they not release the cat until the amount of radioactive materials falls below safe levels.

The amount of time the cat is held will vary significantly based upon the cat's particular medical condition. Some last a couple weeks, others, a few days. Still, they are required to provide the owner with instructions for pet care that will further reduce the potential exposure or contact with radioactive iodine within the cat.

Once released, there will be very small amounts of radioactive materials in the cat's body fluids—primarily in the urine but also in very small amounts in saliva, sweat, blood, etc. I am assuming your cat did not relieve itself on the towel, so let's address those other body fluids.

I am a cat owner and am well aware that they groom themselves constantly, and that they can drool when they are happy. But the radioiodine concentration in saliva will be very, very low after release—probably not even detectable. As for urine, I am sure that the treating facility provided instructions regarding how to handle the urine and regarding washing your hands after cleaning the litter box. That is where you will find the most contamination in the days after your cat was released.

As far as sitting on the towel, the only potential for any measurable radiation dose would be if you were to get the radioactive material into your body through ingestion (hand-to-mouth contact). I am assuming you had clothing on when sitting on the towel but even if you did not, the potential for absorption through the skin is essentially zero due to the low potential amount of material on the towel and low absorption potential.

Radioiodine will be removed from clothes (or the towel itself) through the normal clothes-washing process. I would recommend washing hands after contact with the towel, the cat, and especially the cat's litter box for a week or two after the cat's return home, more as a "prudent avoidance" measure than a belief that there will be significant radiation dose or contamination potential.

So rest assured, the potential for radiation exposure from the towel is very, very low. I hope your cat is doing well after the treatment.

Jeffrey J. Brunette, CHP