Learn more physics!
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 131
I 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 http://en.wikipedia.org/wiki/Iodine-131#Post-treatment_isolation
. As non-experts, we can't evaluate its accuracy in detail.
Whoever gave the 131
I therapy ought to know answers to these sorts of questions, since they must deal with them frequently.
(published on 07/12/2011)
Follow-up on this answer.