Potassium Iodide and Radiation Exposure
Fear of radiation exposure in western Canada due to the crisis in Japan has caused the public to flock to pharmacies to purchase potassium iodide, an over-the-counter salt which may be used to prevent the negative impact radiation exposure can have on health.
Here is what you need to know about potassium iodide:
What is Potassium Iodide (KI)?
Potassium iodide (KI) is a salt of NON-radioactive iodine. KI is routinely added to table salt to make it “iodized”.
How does KI work within the body to prevent negative health effects of radiation exposure?
When KI is ingested, it is taken up by the thyroid gland. When KI is taken at the appropriate time, in the appropriate dosage it will saturate the thyroid gland so that inhaled or ingested radioactive iodine will not be accumulated in the thyroid gland.
What is the benefit of taking KI during a radiological accident?
The KI will help to decrease the risk of thyroid damage from radioiodine uptake. The effects from high doses of radioiodine uptake into the thyroid include: thyroididtis, hypothyroidism, thyroid nodules and thyroid cancer.
What are the limitations of using KI during a radiological accident?
KI cannot prevent radioactive iodine from entering elsewhere in the body. KI only protects the thyroid gland. KI also does not affect the absorption of other radioactive elements that are released, such as cesium, which stays in organs, tissue and the environment much longer than iodine.
Can too much KI be harmful?
Yes. Over supplementing with KI can cause damage to a healthy thyroid. The following are ways in which the thyroid can become damaged if too much iodine is taken: goiter, auto-immune thyroiditis, hypothyroidism, hyperthyroidism and myxedema coma.
Taking KI unnecessarily may also cause allergic reactions and side-effects such as nausea and vomiting. If taken in pregnancy, the fetus runs a higher risk of developing goiter or abnormal thyroid function. High levels of potassium in the blood can also cause cardiac arrhythmias.
The normal recommended daily intake of KI is 0.150 mg per day. This number is easily attained by eating a normal diet. The tolerable upper limit per day a healthy person without thyroid issues should consume is 1.1 mg.
The dose for an adult that must be used in the event of an emergency is upwards of 800x that of the normal recommended daily intake. The recommended dosing in the event of an emergency must be followed strictly to prevent overdose and thyroid damage.
What dose of KI would be recommended in the event of an emergency?
Adults 18 years of age and older (or >70 lbs) – 130 mg (2.9 mls of Lugol’s Solution)
(Adults aged 40 and over only require KI if the dose of radiation expected is larger than 500 cGy or 500 REM as the risk of thyroid damage to those aged 40 and older is extremely low)
Pregnant or lactating women – 130 mg (once) (2.9 mls of Lugol’s Solution)
Children aged 3 months -18 years – 65 mg (1.45 mls of Lugol’s Solution)
Infants 1 month – 3 months – 32 mg (0.71 mls of Lugol’s Solution)
Birth – 1 month – 16 mg (0.35 mls of Lugol’s Solution)
NRC recommends only 2 doses of KI be provided per person in the event of an emergency. The liquid or tablets are only to be used if necessary to supplement evacuation or sheltering. The public is advised NOT to take the KI unless advised to do so, due to the limited duration of the protective effect of KI.
How long does the protective effect of the recommended dose of KI last?
The protective effect of the recommended dose of KI will last for ~24-48 hours. Therefore, it is imperative that the KI be taken approximately 1 hour before fallout levels of radiation are encountered and up to 4 hours after. If radioiodine levels are to persist for more than 48 hours, officials may recommend that KI be taken daily for a few days.
Should Canadians take KI to prevent harm from radiation in Japan?
At the current time, the answer is simply, NO. DO NOT USE POTASSIUM IODIDE UNLESS INFORMED TO DO SO BY A PUBLIC HEALTH OFFICIAL.
There is extensive monitoring going on in Japan, internationally and along the west coast of North America. Even though there has been a release of radioactive materials in the immediate area of the nuclear plant in Japan which includes Iodine 131, it is not a radiological health concern. In the event that there is a significant release of radioactive iodine 131, the main impact would be on populations within the vicinity of the reactor in Japan.
At this point in time, Japan has not issued KI to any of its residents and feels sheltering and evacuation of a 20 km radius is enough to protect its residents from harm. Japan has issued KI to crews working on site at the reactor.
Modeling of the most likely scenarios suggest that any release of radiation into the atmosphere would take several days to reach BC, by which time it would be so dispersed as to be not considered a health risk.
What is the best way to protect yourself from radiation exposure?
Do not travel to Japan. In unlikely event that radiation fallout reaches Canada, remain indoors. If it is suspected that you have been exposed to radiation, remove and wash all clothing and have a shower. In the unlikely event of radiation exposure in Canada, use KI only as directed, and only when advised to do so.
Check the Canadian Nuclear Safety Commission’s website at www.nuclearsafety.gc.ca for daily updates on radiation exposure levels in Canada, Japan and potential fallout regions.