Potassium iodide (KI) pills
The Canadian Nuclear Safety Commission (CNSC) provides information on potassium iodide (KI) pills, their use during nuclear emergencies, and how they protect thyroid health.
You may have already received KI pills if you live near a nuclear power plant. But what are they, how do they work and when should you take them? Here’s what you need to know.
What are KI pills?
Potassium iodide (KI) is a salt of stable (non-radioactive) iodine and is not harmful when taken as directed by a medical or public health official. KI pills are used to protect the thyroid gland from radioactive iodine that may be released into the air and the environment in the unlikely event of a nuclear emergency.
KI pills are effective in reducing the risk of thyroid cancer for individuals at risk of inhaling or ingesting radioactive iodine during a nuclear emergency. While KI pills protect the thyroid gland from radioactive iodine, they are not effective against any other radioactive substances.
These pills serve as a protective measure in certain types of emergencies. KI pills can be taken independently or in conjunction with other protective actions, such as evacuating or sheltering in place.
How do KI pills work?
The thyroid gland naturally absorbs iodine from the bloodstream. However, it cannot differentiate between radioactive and non‑radioactive (stable) iodine. If radioactive iodine is present in the body, the thyroid gland will readily absorb it.
KI pills work by saturating the thyroid gland with stable, non‑radioactive iodine. When the thyroid is full of non-radioactive iodine, there is no room left to absorb any radioactive iodine that may be in the bloodstream.
This greatly reduces the amount of radioactive iodine that can enter the thyroid gland, thereby protecting it. The process is called iodine thyroid blocking.
It is important to understand that KI pills are not an antidote to radiation. Their protective action is specific to the thyroid gland and works only against radioactive iodine. Any radioactive iodine that is not absorbed by the thyroid will eventually be eliminated from the body, primarily through urine, as it undergoes radioactive decay.
When to take KI pills
KI pills should be taken only when instructed by medical or public health officials. Follow the directions on the label or those provided by officials.
Note that KI pills are beneficial only if significant amounts of radioactive iodine are present in the environment. Not all nuclear emergencies involve the release of radioactive iodine.
Low risk of health effects
The risk of health effects from taking KI pills is very low for most people with normal thyroid function. Certain individuals may have an increased risk of side effects. This includes people with pre-existing thyroid disorders such as Graves’ disease, Hashimoto’s thyroiditis, or iodine deficiency/sensitivity.
When side effects do occur, they are typically mild and temporary and may include:
- nausea, vomiting or stomach ache
- diarrhea
- skin rash
- headache
Individuals with the following conditions should consult a doctor before taking KI pills if possible:
- a known thyroid disorder
- an allergy to iodine
- a pre-existing medical condition
Individuals over 40 years are less likely to benefit from taking KI pills. They have a much lower risk of developing thyroid cancer and may have other health conditions.
The benefits of taking KI pills during a nuclear emergency far outweigh the risk of any potential side effects for these groups:
- people under 40 years
- women who are pregnant or breastfeeding
- individuals exposed to higher doses
Neonates (birth to 1 month), pregnant and breastfeeding women and older adults (over 60 years), should receive only a single dose of KI pills.
KI pills in Canada
Licensees of nuclear power plants are required to ensure that KI pills are pre-distributed to individuals living or working near a nuclear power plant.
Two provincial organizations have developed a strategy to fulfill this requirement:
- Emergency Management Ontario (EMO)
- New Brunswick Emergency Measures Organization
These provincial organizations work with nuclear plant operators, local municipalities, and public health units to ensure that KI pills are accessible to those who may need them.
What to do in the unlikely event of a nuclear emergency
In the event of a nuclear emergency, there will be prompt notifications:
- Sirens will be heard within 3 km of the nuclear generating station for 3 minutes following a nuclear emergency, alerting residents to return indoors.
- Residents within 10 km of the nuclear generating station will receive an automated telephone message through their landlines and text alerts on cell phones.
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Alert Ready, Canada’s emergency alerting system, will deliver alerts to Canadians who may need to take action.
- These alerts will be sent through television, radio, and LTE-connected and compatible wireless devices.
If you receive an alert:
- Stop and go inside.
- Listen to media reports to stay informed of the situation.
- Follow instructions from the province for the next steps.
During a nuclear emergency, if you are at or nearby the nuclear power plant, you may be asked to shelter in place, evacuate, or take KI pills.
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