Iodine blockade

from Wikipedia, the free encyclopedia

The iodine blockade is one of the possible protective measures in the event of a serious nuclear accident. In this context it is also referred to as "iodine prophylaxis" or simply as "taking iodine tablets". Iodine blockade is the preventive intake of stable (i.e. non-radioactive) iodine to prevent the uptake of radioactive iodine into the thyroid and thus prevent the development of thyroid cancer . It is usually taken in the form of so-called "iodine tablets", which are, strictly speaking, high-dose potassium iodide or potassium iodate tablets .

Iodine blockade after a strong release of radioactive iodine in a nuclear accident or a nuclear weapon explosion is recommended by the radiation protection commission in Germany and by the responsible authorities in many other countries. To ensure the “supply of the population with drugs containing potassium iodide in the event of radiological events”, the Potassium Iodide Ordinance (KIV) was enacted in Germany in 2003 ( Section 1 , Paragraph 1 KIV). The ordinance regulates various exceptions to the Medicines Act . From October 2004, potassium iodide tablets were distributed to the population by pharmacies or central distribution points in the vicinity of German and Belgian nuclear power plants . In addition, potassium iodide tablets are kept in stock.

In Switzerland , the national alarm center at the Federal Office for Civil Protection can radio a request to take iodine tablets. In the immediate vicinity (initially 20 km, since 2014 50 km) around the nuclear power plants, the tablets have been distributed to the population as a precaution every five years since 2004.

In Austria there is an extensive supply of iodine tablets in pharmacies, kindergartens, schools, in the army and in the so-called "Federal Reserve", which is regularly renewed. The health authorities may request distribution and consumption via radio and television.

In the United States , authorities keep iodine tablets available for residents within 10 miles of nuclear power plants.

In Japan , after the Fukushima nuclear disaster, iodine tablets were mostly sold unregulated through pharmacies. Preparations from the state emergency supply were only distributed to around 380,000 residents of the immediate disaster area.

Mode of action

After incorporation by inhalation , radioactive iodine behaves chemically just like stable iodine. After it is distributed in the extravascular space , it is enriched and stored in the thyroid gland. The biological half-life for the stored iodine depends on the age and the hormone turnover . The values ​​assumed for estimating the radiation exposure are shown in the following table:

Assumed biological half-life of iodine (for estimating radiation exposure)
Age group Biological half-life in days
thyroid Rest of the body
0 to 1 year 11.2 01.12
> 1 to 2 years 15th 01.5
> 2 to 7 years 23 02.3
> 7 to 12 years 58 05.8
> 12 to 17 years 67 06.7
> 17 years 80 12

The accumulation of iodine in the thyroid gland results in the thyroid gland's special radiation exposure through incorporated radioactive iodine nuclides. As an example, the following table shows the dose coefficients for the inhalation of 131 I in the form of elemental iodine (I 2 ) for different age groups:

Dose coefficients for the inhalation of 131 I in the form of elemental iodine (I 2 )
Organ / tissue Dose coefficient in Sv / Bq
0 to 1 year > 1 to 2 years > 2 to 7 years > 7 to 12 years > 12 to 17 years > 17 years
thyroid 3.3 · 10 −06 3.2 · 10 −06 1.9 · 10 −06 9.5 · 10 −07 6.2 · 10 −07 3.9 · 10 −07
other 3.4 · 10 −10
to
1.1 · 10 −08 		2.3 · 10 −10
to
8.6 · 10 −09 		1.3 · 10 −10
to
5.0 · 10 −09 		7.3 · 10 −11
to
3.1 · 10 −09 		4.3 · 10 −11
to
2.2 · 10 −09 		3.6 · 10 −11
to
1.8 · 10 −09

In this example, the equivalent dose for the thyroid gland is about 2-4 powers of ten greater than the equivalent dose for other organs or tissues. Children are particularly at risk. For example, the inhalation of 1000 Bq 131 I in the form of elemental iodine (I 2 ) for the thyroid gland of a child up to one year old corresponds to  a subsequent dose of about 3.3  mSv (without iodine blockade).

However, the thyroid's capacity to store iodine is limited. Excess iodine that is not stored in the thyroid is excreted with a biological half-life of a few hours.

Therefore, the storage of radioactive iodine in the thyroid can be largely prevented if a larger amount of stable iodine is administered before the radioactive iodine is absorbed, so that the thyroid's absorption capacity is exceeded. The radioactive iodine that may subsequently be absorbed is then largely not even stored in the thyroid gland, but excreted with a comparatively short biological half-life.

The described mode of action shows that the iodine blockade only protects against the absorption of radioactive iodine into the thyroid gland. On the other hand, it has no influence on the effects of other radioactive substances.

Intervention levels

In Germany, the intervention level for the intake of iodine tablets corresponds to an equivalent dose for the thyroid gland (subsequent organ dose) of

  • 50  mSv in children and adolescents under 18 years of age as well as pregnant women and
  • 250  mSv for people aged 18 to 45 years

from the radioactive iodine inhaled over a period of seven days. (If, in the case of a prolonged release, the period of cloud passage is longer than seven days, then the integration time should be extended accordingly.)

The dose to be compared with the intervention levels is the dose via the exposure pathways against which the measure acts. Accordingly, direct radiation from radioactive substances in the air or on the ground and the inhalation of radionuclides other than iodine are not taken into account when assessing the intake of iodine tablets. In addition, the ingestion of radioactive iodine is not taken into account for the decision on iodine blockade, because this exposure path is better avoided by the supply of uncontaminated food than by taking iodine tablets. The intervention levels therefore apply under the condition that the supply of uncontaminated food is guaranteed.

The dose to be compared with the intervention reference levels is basically the potential and not the actual or even the avoidable dose. In particular, when applying the intervention levels, an uninterrupted stay in the open air for 24 hours per day is assumed in order to be independent of the locally different protective influences.

If the intervention levels are reached, there is a fundamental need for action for radiological reasons. However, intervention levels that are above the intervention reference levels can be justified if the implementation of the measure is associated with major disadvantages or the avoidable dose is low. However, intervention levels that are below the intervention levels cannot be justified for radiological reasons.

dosage

The iodine tablets intended for nuclear disaster control "can be handed in for final consumption in the event of a radiological incident at the instigation of the competent authority [...]." ( Section 1 , Paragraph 2 KIV) In Germany, the tablets can also be purchased without a prescription in the pharmacy for personal storage become. A typical iodine tablet from emergency stocks in the vicinity of nuclear facilities in Germany contains 65 mg potassium iodide (this corresponds to 50 mg iodide). The tablets have a cross-shaped score line on the inside and notches on the outside, which means that they can be divided into equal halves or quarters. Tablets with other quantities (e.g. 130 mg potassium iodide, equivalent to 100 mg iodide) are also available from pharmacies.

These iodine tablets must not be confused with the tablets intended for the prevention of iodine deficiency symptoms or for the treatment of thyroid diseases, as their iodine content is far too low (e.g. 100 µg or 200 µg iodine) to be used for iodine blockade.

The recommendations published by the World Health Organization (WHO) and also valid for Germany provide for a single dose of 100 mg iodide for iodine blockade for adolescents over 12 years of age and adults. This corresponds to a dose of 130 mg potassium iodide. For comparison: this amount is three powers of ten higher than the (normal) daily iodide intake of 150 µg recommended by the WHO for an adult with food. For younger children, depending on age, between 12.5 and 50 mg iodide is recommended, as shown in the following dosage schedule:

Dosing regimen in Germany
Age group Daily dose in mg iodide Daily dose in mg potassium iodide Tablets of 65 mg potassium iodide
<1 month 012.5 016.25 ¼
1–36 months 025th 032.5 ½
3–12 years 050 065 1
13–45 years 100 130 2
> 45 years 00- 00- -

People over 45 years of age should not take iodine tablets because the risk of side effects would be higher than the risk of developing thyroid cancer later. According to the WHO recommendation, this age limit is 40 years. For pregnant women and nursing mothers this age limit does not apply. The same dosage applies to them as to the group of 13 to 45 year olds. The iodine tablets can be swallowed in the specified amount - if possible not on an empty stomach. In particular, to make it easier for children to take, the corresponding amount can also be dissolved in a drink. However, such solutions are not durable and should therefore be drunk immediately. In principle, a single intake of the iodine tablets is assumed to be sufficient. However, depending on the radiological situation (e.g. prolonged or delayed releases), the competent authority could recommend further intake. In this case, other measures (e.g. evacuation ) should be taken to ensure that pregnant women, breastfeeding women and newborns do not have to take a second dose of iodine tablets.

time

Because of their above The mode of action of the iodine blockade is most effective when there is an excess of stable iodine in the thyroid gland before the radioactive iodine is inhaled. The iodine tablets should therefore be taken as soon as possible before the release of radioactive iodine. However, the storage of radioactive iodine in the thyroid gland can still be reduced a few hours after inhalation by taking iodine tablets. After 2 hours the reduction is still about 80%, after 8 hours it is about 40%. If there is a delay of more than 24 hours after inhalation of radioactive iodine has been completed, the iodine blockade no longer has any significant influence on the storage of radioactive iodine in the thyroid, which is why iodine tablets should no longer be taken after this time. If, on the other hand, the iodine blockade occurs too early, the excess of stable iodine may already have been broken down again by the time the radioactive iodine is inhaled due to the relatively short biological half-life for the excess iodine, so that the effectiveness is correspondingly reduced. The decision as to the optimal point in time for the iodine blockade can therefore only be made after assessing the overall situation of the nuclear accident. For this reason, iodine tablets should only be taken when requested by the competent authority and never because of personal concerns.

Contraindications

Potassium iodide tablets must not be used for iodine blockade in:

If there are contraindications to the intake of iodine compounds, perchlorate is best suited for thyroid blockade , as it competitively inhibits the uptake of iodine . For example, sodium perchlorate can be used in the form of Irenat ® drops.

Side effects

If iodine tablets are taken on an empty stomach, irritation of the gastric mucosa may occur. Potassium iodate is more irritating than potassium iodide, which is why potassium iodide tablets are preferred for iodine blockade. In individual cases, an iodine-related hyperthyroidism can occur. Symptoms such as increased heart rate, sweating, insomnia, shakiness, diarrhea and weight loss despite increased appetite can be signs of an overactive thyroid. A previously unknown intolerance to iodine ("iodine allergy") can appear for the first time when taking iodine tablets. Allergic symptoms such as B. reddening of the skin, itching and burning in the eyes, runny nose, dry cough, diarrhea and headache and the like. Ä. Symptoms occur. In order to avoid unnecessarily exposing themselves to the risk of side effects, the population should be made aware that it is useless and even harmful if they initiate iodine blockade on their own, i. H. would perform without a request from the competent authorities.

Chernobyl disaster

During the reactor catastrophe in Chernobyl from April 26, 1986, there was a very strong release of radioactive substances over the course of several days, including in particular radioactive iodine nuclides. An activity of 1.76 · 10 18 Bq was released specifically from the radionuclide 131 I (half-life: 8.02 d) .  

However, the majority of the population immediately affected have not been blocked by iodine. An exception were the inhabitants of Pripyat , who were looked after by local specialists. About 60–70% of the residents of Pripyat took potassium iodide tablets after the accident before the city was evacuated after about 1.5 days.

Iodine tablets were also given to liquidators in the first few weeks after the accident . However, taking it was not mandatory and it was not suggested to everyone. Only an estimated 20% of workers ingested stable iodine before exposure to radioactive iodine.

Poland is the only country to have iodine blockade for almost all (an estimated 98%) children. After radioactive substances were found in the air and milk, a government commission decided to make a mandatory iodine blockade for children and adolescents up to 16 years of age and a voluntary iodine blockade for other people. For this purpose, iodide was not administered in the form of tablets, but in dissolved form according to the following dosage schedule:

Dosing regimen of iodine blockade in Poland
Age group Single dose in mg iodide
0-1 year 15th
2-6 years 30th
7-16 years 60

As of April 29, 1986, a total of around 18 million Poles were given a single dose of potassium iodide. Since the passage of the radioactive cloud was not yet complete at this point in time, a delayed iodine blockage still had a certain effect, as the following table shows:

Estimated Effectiveness of Iodine Blockade in Poland
Time of ingestion Decrease the thyroid dose
April 28, 1986 44%
April 29, 1986 40%
April 30, 1986 26%
May 1, 1986 12%

Web links

Individual evidence

  1. ^ Principles for Intervention for Protection of the Public in a Radiological Emergency . International Commission on Radiological Protection (ICRP), ICRP Publication 63. In: Annals of the ICRP Vol. 22, No. 4, 1991
  2. ^ Criteria for Use in Preparedness and Response for a Nuclear or Radiological Emergency . International Atomic Energy Agency (IAEA), General Safety Guide No. GSG-2, Vienna 2011, ISBN 978-92-0-107410-2
  3. ↑ staedteregion-aachen.de ( Memento of the original from September 15, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed September 18, 2017 @1@ 2Template: Webachiv / IABot / jodtabletten.staedteregion-aachen.de
  4. ↑ Taking iodine tablets. ( Memento of the original from December 20, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. FOCP website, accessed November 19, 2013 @1@ 2Template: Webachiv / IABot / www.naz.ch
  5. ↑ jodtabletten.ch
  6. ↑ Potassium iodide prophylaxis in nuclear power plant accidents . (PDF; 66 kB)  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. Technical information from the Austrian health authorities, 2002@1@ 2Template: Dead Link / www.apotheker.at  
  7. ^ Use of potassium iodide. US Nuclear Regulatory Commission, June 5, 2013
  8. ↑ Embassy in Tokyo supplies Swiss people with iodine tablets. Tagesanzeiger, March 17, 2011
  9. ^ Age-dependent Doses to Members of the Public from Intake of Radionuclides - Part 1 . International Commission on Radiological Protection (ICRP), ICRP Publication 56. In: Annals of the ICRP Vol. 20, No. 2, 1990
  10. ↑ Age-dependent Doses to the Members of the Public from Intake of Radionuclides - Part 5 Compilation of Ingestion and Inhalation Coefficients . International Commission on Radiological Protection (ICRP), ICRP Publication 72. In: Annals of the ICRP , Vol. 26, No. 1, 1995
  11. ↑ Guidelines for the radiation protection adviser of the disaster control management in nuclear emergencies . Radiation Protection Commission (SSK), adopted at the 182nd session of the Radiation Protection Commission on April 4-6. December 2002. In: Reports of the Radiation Protection Commission (SSK) of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety , Issue 37, Urban and Fischer Verlag, Berlin 2004
  12. ↑ a b Framework recommendations for disaster control in the vicinity of nuclear facilities . Radiation Protection Commission (SSK), adopted in the 274th session of the Radiation Protection Commission on 19./20. February 2015, published in BAnz AT 04.01.2016 B4 urn : nbn: de: 101: 1-201512213337
  13. ↑ a b c d Radiological basis for decisions on measures to protect the population in the event of accidental releases of radionuclides . Radiation Protection Commission (SSK), recommendation of the Radiation Protection Commission, editorial revision noted with approval at the 223rd session of the Radiation Protection Commission on May 13, 2008. In: Reports of the Radiation Protection Commission (SSK) of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety , Volume 61, H. Hoffmann Verlag, Berlin 2009, ISBN 978-3-87344-156-9 . Also published as: Radiological basis for decisions on measures to protect the population in the event of accidental releases of radionuclides from October 27, 2008 (GMBl. 2008, No. 62/63, p. 1278)
  14. ↑ a b c Taking iodine tablets as a protective measure in the event of a serious accident in a nuclear power plant - information brochure . Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), December 2010.
  15. ↑ a b c d e f g h i j Use of iodine tablets to block the thyroid gland in the event of a nuclear accident . Radiation Protection Commission (SSK), recommendation of the Radiation Protection Commission, adopted in the 247th session of the Radiation Protection Commission on 24./25. February 2011, administrative regulations-im-internet.de
  16. ↑ Iodine tablets intake brochure. (PDF) Federal Ministry for the Environment, Nature Conservation, Building and Reactor Protection, p. 6 , accessed on April 13, 2017 .
  17. ↑ a b c d e World Health Organization (WHO): Guidelines for Iodine Prophylaxis following Nuclear Accidents , Update 1999, Geneva, WHO / SDE / PHE / 99.6
  18. ↑ Trace elements in human nutrition and health . World Health Organization (WHO), 1996, Geneva, ISBN 92-4-156173-4
  19. ↑ a b c d Potassium iodide "Lannacher" 65 mg tablets, Austrian instructions for use. (PDF) December 3, 2015
  20. ↑ a b c UNSCEAR 2008 Report to the General Assembly with Scientific Annexes , Volume II. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), New York 2011
  21. ↑ M. Balonov, G. Kaidanovsky, I. Zvonova, A. Kovtun, A. Bouville, L. Luckyanov, P. Voillequé: "Contributions of short-lived radioiodines to thyroid doses received by evacuees from the Chernobyl area estimated using early in vivo activity measurements "in: Radiat Prot Dosimetry (2003) 105 (1-4) pp. 593-599
  22. ↑ UNSCEAR 2000 Report to the General Assembly, with scientific annexes , Volume II, Annex J. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), New York 2002
  23. ^ A b Zbigniew Jaworowski: The first four weeks . In: IAEA Bulletin , autumn 1986, pp. 33-34
  24. ^ A b P. Krajewski: Evaluation of equivalent body burden in the thyroid for the people of Poland on results of 131 I absorption after the disaster in Czernobyl. Determination of thyroid blockade with potassium iodide . In: Endokrynologia Polska , 1991, 42 (2), pp. 189-202