Iodine 131 Halflife

Most recent answer: 07/12/2011

How long do doorknobs, faucets, furniture in a home remain radioactive after becoming contaminated from being touched by someone who just received a fairly high dose of radioactive iodine to treat cancer?
- Brenda (age 45)
DesMoines, Iowa, USA
  Those are important questions.

The radioactive isotope  131I  has a half-life of 8.02 days. After 7 half-lives (~56 days), 1/27 of the radiation is left, i.e. a little less than 1%.

There's a reasonable-looking discussion of this very issue on Wikipedia . As non-experts, we can't evaluate its accuracy in detail.

Whoever gave the  131I  therapy ought to know answers to these sorts of questions, since they must deal with them frequently.

Mike W.

(published on 07/12/2011)