Can iodine purification tablets be used to prevent absorption of radioactive iodine (tetraglycine hydroperiodide, potassium iodide)

Question

Can one use iodine tablets made of tetraglycine hydroperiodide to protect yourself from radiation poisoning in an emergency? If so, how much should one take?

The CDC recommends adults take 130mg of Potassium Iodide in the event of a radioactive emergency to saturate the thyroid with iodine and prevent absorption of radioactive iodine.

KI (potassium iodide) is a salt of stable (not radioactive) iodine that can help block radioactive iodine from being absorbed by the thyroid gland, thus protecting this gland from radiation injury.

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The FDA has approved two different forms of KI (potassium iodide), tablets and liquid, that people can take by mouth after a radiation emergency involving radioactive iodine.

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Adults should take 130 mg (one 130 mg tablet OR two 65 mg tablets OR two mL of solution)

Source: https://www.cdc.gov/nceh/radiation/emergencies/ki.htm

In this treatment, the Potassium in the salt is not relevant.

The CDC also explicitly states that the iodine present in some table salts is not sufficient to provide protection

Table salt and foods rich in iodine do not contain enough iodine to block radioactive iodine from getting into your thyroid gland. Do not use table salt or food as a substitute for KI.

However, the CDC does not mention anything about tetraglycine hydroperiodide, which is readily available as an emergency water purification tablet. These tablets are common household items for backpackers. For example, REI (a popular store for trekking in the US) sells iodine tablets with 20mg of tetraglycine hydroperiodide, 50 tablets per bottle.

Is it safe to use tetraglycine hydroperiodide to flood the thyroid with stable iodine (thereby prevent absorption of radioactive iodine into the thyroid) in a radioactive emergency? If so, what is the recommended dose of tetraglycine hydroperiodide that one should take?

Answer 1

A few thoughts about the dosage:

130 mg KI contain ≈ 780 nmol I (100 mg). One of the linked tablets contains ≈ 94 nmol I (11.9 mg).
So, 8 and 1/3 of the water purification tablets have the same amount of iodine as the 130 mg KI tablet. Do not use flavor enhancing stuff that may be sold together with the water purification tablets, though..

RDI for adults (without nuclear emergency) is in the order of magnitude of 150 μg.

Iodized table salt typically contains in the order of magnitude of very roughly 20 mg I/kg. You'd need to eat 5 kg of iodized table salt to get 100 mg I.

Oxidation state of the iodine bascially does not matter for uptake. The iodine supplementations or treatments range all the way from iodide (-I) over iodine(0) (I_2 ⋅ KI solution, also tetraglycine hydroperiodide is a compound of 16 glycine, 5 I_2 and 4 HI) ) to iodate (+V). The WHO Iodine prophylaxis guide lists both KI (iodide) and KIO_3 (iodate) dosage for nuclear emergency:

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Please also read the counterindications, e.g. for adults > 40 yo, iodine prophylaxis is not as generally recommended due to both higher risk of side effects and lower risk of thyroid cancer (see e.g. the CDC page in the question or the WHO recommendation linked above).

The WHO guideline spells out very clearly that the subpopulation that most importantly needs iodine prophylaxis in a nuclear emergency (newborns) are also most/more difficult to properly dose.

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Also keep in mind that uptake of iodine (radioactive or not) is low if you are not iodine deficient in the first place. The [adult] human body contains about 15 - 20 mg I in total, so 100 days' RDI or 1 - 2 weeks of Japanese daily input. Or purification tablets for 1.5 l water.

Answer 2

The answer is yes. I found a couple of studies looking at hydroperiodide function in the thyroid. Both of them were from the same group of authors and from the military, where use of these sorts of things is relatively common.

One of these studies ¹ (very small, only 14 people, so take with a grain of salt*) looked at how safe it was for people to consume these over a short period, such as when hiking. They found that there was a mild impairment of thyroid function from the uptake of iodine from these tablets:

One week of daily exposure to the iodine load from four tetraglycine hydroperiodide water-purification tablets causes mild impairment of thyroid function in humans.

The second looked at adaption of the thyroid to hydroperiodide uptake from these tablets.². Most relevant to your question, they found:

Radioactive iodine uptake was less than 2% after 7 days and remained below 2% in all subjects at 90 days.

1. Georgitis WJ, McDermott MT, Kidd GS. An iodine load from water-purification tablets alters thyroid function in humans. Mil Med. 1993 Dec;158(12):794-7. PMID: 8108021.

2. LeMar HJ, Georgitis WJ, McDermott MT. Thyroid adaptation to chronic tetraglycine hydroperiodide water purification tablet use. J Clin Endocrinol Metab. 1995 Jan;80(1):220-3. doi: 10.1210/jcem.80.1.7829615. PMID: 7829615.

• pun intended, it just fits nicely with the topic.