I've heard that tincture of iodine is only recommended for short-term use that is no longer than 30 days. And also you should know that you shouldn't use iodine if you are pregnant or suffer from a thyroid problem. I don't know maybe bleach is not such a last resort after all since the water I drink from the faucet here is treated with chlorine. It's probably aslo relative to the type of microorganisms that are present... But chlorine is not very strong for field-water disinfection according to Cody Lundin. Hum... Water disinfection is a complex subject.