Iodine Iodine has been used to disinfect water for nearly a century. It has advantages over chlorine in convenience and probably efficacy; many travelers find the taste less offensive as well. It appears safe for short and intermediate length use (3-6 months), but questions remain about its safety in long-term usage. It should not be used by persons with allergy to iodine, persons with active thyroid disease, or pregnant women. Note that Iodine and other halogens appear to be relatively ineffective at killing cyclospora, a troublesome diarrhea-causing bacteria seen in Nepal only in the late Spring and Summer months. At these times it may be reasonable to pre-filter water to remove the large cyclospora (about the size of Giardia cysts), and then treating with iodine. Iodine is available in numerous forms, which can be confusing to the traveller. A simplified table is presented below; for more complete information refer to (Backer 1995). NOTES: - final drinking concentrations calculated at 8 mg iodine/liter - measure with a tuberculin syringe or dropper: 1 drop = 0.05 ml - In general, if you are in a hurry double the chemical dose and halve the contact time; if you want better flavor halve the dose and double the contact time. - If you believe the water may be heavily contaminated, double the chemical dose or double the contact time. - Iodine Topical Solution and Iodine Tincture also contain 2.4% sodium iodide, Lugols Solution also contains 10% potassium iodide, increasing the dose of iodine ingested. - Povidone is a non-toxic polymer that binds the iodine and allows higher concentrations in a water-based solution. This complex system provides a sustained-release reservoir of free iodine, and makes calculation of the strength of the solution difficult. - A system comprising iodine crystals in plain water is available, and works well. It lasts an extremely long time. I have not shown it here because the amount of iodine dissolved in the water is highly temperature-dependent, and this is problematic in the universally cold environment of the Himalaya. - Addition of a small amount of vitamin C (50 mg) to your water after the contact time with the iodine will render the water nearly flavorless!
Posted on: Fri, 23 Jan 2015 04:06:01 +0000
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