Agency for Toxic Substances and Disease Registry
Radiation Exposure from Iodine 131
Treatment and Management (continued)

Acute Exposure

To reduce internal exposure to I-131 by inhalation, residents of communities near a release could stay indoors with the doors and windows closed to keep contaminated air out of their homes. Moist towels can be laid on window sills and at the bottom of doors to reduce air infiltration. The exposure scenario determines the relative significance of the different pathways (Whicker and Pinder 2002).

Prophylactic Administration of Stable Iodine (Potassium Iodide)

• Administration of potassium iodide (KI) can significantly reduce thyroid I-131 uptake.

Potassium iodide (KI) is the preferred form of stable iodine. Thyroid uptake of I-131 can be reduced by more than 90% through an immediate oral dose of KI. Failure to administer KI within 2-4 hours after exposure to I-131 eliminates protection against the risk for adverse health outcomes.

Taking KI just before or within 1 to 2 hours after exposure to I-131 can block more than 90% of the radioactive iodine uptake by the thyroid. This means that public health officials must notify the public and the health professional community of I-131 releases immediately. If KI is taken 3 hours after acute exposure, approximately 50% of the thyroid uptake of I-131 is blocked. When KI is taken 4 hours after acute exposure, only 10% of the I-131 thyroid uptake is blocked. Taking KI more than 4 hours after exposure provides little protection unless the exposure to I-131 continues. Contraindications include allergies to iodine and must be considered before administering KI. Potassium iodate (KIO3) can also be used, although it might be associated with slightly more gastrointestinal irritation. Information on age-specific dosage recommendations is given in Table 2. Precautions and contraindications applicable to KI are found in Food and Drug Administration (FDA) guidelines (FDA 2001). To continue treatment, doses of KI should be administered once each day for 7 to 14 days to prevent recycling of the I-131 into the thyroid.

Table 2. Recommended Single Doses of Potassium Iodide (KI) as a Blocking Agent, by Age Group

For persons older than 40 years of age, the risk for radiation-induced thyroid cancer is extremely low, while the potential side effects of prophylaxis due to preexisting thyroid disease tend to increase. Adults over 40 therefore do not need to take potassium iodide as prophylaxis for exposure to I-131. In the United States, the FDA has recommended prophylaxis with stable iodine when the committed dose equivalent to the adult thyroid is expected to exceed 250 milliSieverts (mSv), the equivalent of 25 rem (Roentgen equivalent in man or mammal) (FDA 2001). Sale or use of KI for this purpose does not require a physician's prescription.

Current Nuclear Regulatory Commission (NRC) policy acknowledges that the use of KI is a protective measure for specific local conditions for populations exposed to I-131. It also states that KI is an inexpensive and reasonable supplement to sheltering and evacuation in case of a nuclear release. NRC policy requires that consideration be given to the use of KI in developing site-specific emergency plans.

If you live within 50 miles of a nuclear facility (Emergency Planning Zones or EPZ) that produces or is capable of releasing I-131, you should work with your medical association, local or state public health department, emergency response organizations, and elected representatives to ensure that a stockpile of KI is available and a distribution plan is in place. Predistribution of sealed packets of KI tablets to residents within the EPZ, combined with educational materials, instructions, and engagement in exercises would enable a significant percentage of the at-risk population to efficiently undergo prophylaxis when so advised by public health officials. However, because predistribution is unlikely to completely reach the target or vulnerable population, supplemental stocks of KI tablets should be stored at strategic locations such as schools, hospitals, pharmacies, fire departments, and police stations. Individually sealed tablets of KI incorporated into a cardlike dose pack will be stable for 5-10 years, or possibly longer.

• The conversion of contaminated milk to powdered milk, cheese, yogurt, or ice cream allows I-131 to decay to lower levels, thus reducing radiation exposure.

The easiest way to reduce or eliminate internal exposure to I-131 during a release is to find an alternate food source of items produced outside the contamination zone. Contaminated milk can be made into cheese, yogurt, or ice cream; it can also be converted to powdered milk that can be used after the I-131 decays away.

Challenge Questions

Communicating about Risks

• Effective risk communication allows the populations affected to improve decision making; it also can relieve tension.
• Perception of risk is affected by many factors and can be unrelated to actual risk.
• Good communicators establish trust by getting factual, timely information to the community and including all stakeholders early in the process.

During the Three Mile Island release in 1979, the population in the area perceived a high risk associated with the release. Poor management of the situation and poor communication with the population in the affected area led to mistrust and increased levels of psychosocial stress that remained elevated for many years.

The field of health risk communication has developed science-based approaches for communicating effectively in high-concern, low-trust, sensitive, or controversial situations. Good risk communication involves a dialogue among all persons and groups concerned to communicate the nature and level of risk and the steps to take to change that level. The goal of risk communication is to increase knowledge and understanding, to enhance trust and credibility, and to resolve conflict.

Risk communication is of critical importance in the evaluation and management of persons with concerns about past exposure to I-131. It involves the characterization of information with the involvement of individuals and communities who might have been exposed. These individuals and communities are stakeholders in the risk communication process. In this process the risks are effectively communicated, relieving tension and anxiety, improving subsequent communications, and increasing the effectiveness of risk management decisions.

The perception of risk by individuals or communities can be affected by several factors other than how the risk is communicated. This includes cultural, social and economic level, geographic location, previous experience, and other variables inherent to the individual, such as personality. In matters of high concern and low trust, perception equals reality. Peter Sandman (1993) developed a framework for dealing with risk. Risks that are

• natural are more readily accepted than those that are man-made
• visible and avoidable are more readily accepted than those that are unseen and imposed by others
• voluntarily assumed are more acceptable than those that are involuntarily imposed
• familiar are more acceptable than risks that are exotic or unfamiliar.

The public might be distrustful and upset because a real threat to their health has occurred. They expect to receive information about the incident, about who is exposed and what dose was received, and about how the exposure will affect their health. The level of trust a source has developed with a community will determine how credible the community will perceive the message to be.

Empathy and caring, dedication and commitment, competence and expertise, and honesty and openness are important trust and credibility factors. Health care providers are among the top third in surveys on trust and credibility on health and environmental issues.

Key issues within communities are health, safety, environment, quality of life, fairness, legality, and economics. The media has an important role in communicating risks to the general public and should be included as partners in a risk communication plan. Government officials and health care and public health professionals often seek out the media, or are sought out by the media, to explain risk resulting from catastrophic events. A communications plan must be in place before such an event to maximize the opportunity to promptly and accurately inform the public.

In communicating information about health risks, it is important for messages to be consistent. Coordinate with your local medical association, local or state public health department, emergency response organizations, and elected representatives to ensure that all segments of the community receive clear and consistent messages.

Persons with concerns about exposure to I-131 might have fear and anger that need to be addressed in a timely manner by health care providers. The health care provider can encourage trust and credibility by getting the facts of the exposure straight, being forthcoming with information that meets the needs of the individuals, coordinating efforts with public health agencies, and avoiding giving mixed messages.

In persons with concerns about I-131 exposure, great uncertainty exists about the risk. Uncertainty exists with respect to previous and present exposures, the dose received by individuals, the clinical significance of exposure and dose, and who might be legally and morally responsible for the financial costs of the exposure. The health care provider needs to anticipate this uncertainty to effectively help the patient recognize the risks. It is important to deal with the uncertainty; listen to and deal with specific concerns; convey the same information to all segments of your audience; and explain risk in language people understand, simplifying language and presentation, but not content.

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