How the Chernobyl nuclear accident affected thyroid health

The state of Hashimoto’s and thyroid conditions 30 years after the radioactive spillage


On April 26th 1986, one of the reactors at the Chernobyl Nuclear Power Plant exploded. One of the nuclear power plant reactors blew up, releasing large amounts of radiation into the atmosphere. Over 100 radioactive elements were scattered over parts of Ukraine, Belarus, Russia, and a wide area of Europe (1, 2). Because of the massive contamination, 200,000 people were evacuated and the area around the nuclear plant is unlivable (1).

An increase in thyroid disorders was one of the most common health problems in areas affected by the Chernobyl radioactive fallout (3).


Radioactive fallout

The explosion at the Chernobyl Nuclear Power Plant was powerful—about 400 times stronger than the Hiroshima atomic bomb (1). It released close to 2 EBq (2000000000000000000 Bq) worth of radioactivity in the air. In a medical context, a maximum therapeutic dose of iodine-131 used in clinics is 7.4 GBq (7400000000). This means the dose of Chernobyl radiation was about 270000000x higher than a therapeutic dose for cancer treatment (1, 4, 5).

Three main radioactive elements were released from the Chernobyl disaster (the halflife is the time it takes for one half of the radioactive elements to disintegrate):

Iodine-131: with a halflife of 8 days, known to lead to thyroid problems.

Strontium-137: with a halflife of 29 years, can cause leukemia.

Cesium-90: with a halflife of 30 years, can harm the entire body—especially the liver and spleen.


Radioactive iodine and the thyroid

Radioactive iodine (I-131) is a by-product of energy production in a nuclear reactor. In the case of the Chernobyl disaster, when I-131 was released in the air it got into the human body through breathing it in, eating contaminated leafy vegetables, or drinking contaminated milk (from cows and goats grazing contaminated grass) (6).

With such an intake, up to a third of all of the radioactive iodine in the body will end up in the thyroid gland. As radioactive iodine decays, it emits radiation and affects the thyroid and the nearby tissue. This process destroys thyroid cells as well as the surrounding capillaries preventing blood supply with oxygen and food. As a result, there are a lot of dying cells that start producing molecules triggering inflammation, this attracts immune cells to the thyroid.

As a consequence, immune cells flock to the thyroid gland to clean up the dead cells. Among the cell debris are parts of TPO and Tg. The entire site of the cell debris becomes inflamed, thus immune cells start their cleanup and from that point on they have a memory of TPO and Tg protein sequences and will attack them as an enemy for years to come (7, 8).

Even though the iodine-131 halflife is short, it was released in high doses from the destroyed nuclear reactor in Chernobyl for about 40 days after the accident. It took about seven months for it to decay to a safe level of radiation, this amount of time was enough to cause problems for thyroid health for years to come (2).

After the Chernobyl disaster, an increase in thyroid nodules elevated anti-TPO and anti-Tg antibodies. More underactive thyroid cases were reported in people living in the most affected areas of Ukraine, Belarus, and Russia (9). Exposure to radioactive fallout from Chernobyl caused a big increase in the number of cases of childhood and adult thyroid cancer in Ukraine, Belarus, and a part of Russia (4, 10 - 12).

Chernobyl and Hashimoto’s

Several reports have shown an increase in anti-TPO and anti-Tg antibodies in people most severely affected by the radioactive fallout. This increase seems to be transient, lasting for a period of up to 15 years. After which it seems the immune system resets, no antibodies are detected, and it’s likely the thyroid gland is no longer attacked (13-18).

Research shows how thyroid health developed in the 30 years after the Chernobyl accident. Many researchers noted autoimmune reaction changes through time and people that were exposed to radiation should be checked throughout the years to see the dynamics of radiation-caused autoimmune response.

Radioactivity doesn’t only turn the immune system against the thyroid, it changes how the immune system interacts with the entire body. It causes long-term inflammation that can severely damage, or even destroy some organs (19-23).

What may help?

Avoiding areas of high radioactivity is the best option, but sometimes—like in the case of the Chernobyl of Fukushima disasters—this isn’t possible.

Potassium iodine (KI) is considered the most effective preventive radiation management when exposed to high doses of iodine-131 radiation (24, 25). Potassium iodine prevents iodine-131 from becoming a building block of T4 and T3 hormones (26, 27). A single dose of potassium iodine helps for 24-36 hours (28-30). Newborn babies and elderly people might experience some side effects of potassium iodine, including upset stomach, digestive problems, rashes, and inflammation (31).

References

  1. International Atomic Agency. Frequently Asked Chernobyl Questions, 2005

  2. Nuclear Energy agency. Chernobyl: Assessment of Radiological and Health Impact 2002 Update of Chernobyl: Ten Years On, 2002

  3. Detours V, et al. Genome-wide gene expression profiling suggests distinct radiation susceptibilities in sporadic and post-Chernobyl papillary thyroid cancers, 2007

  4. Williams D. Twenty years' experience with post-Chernobyl thyroid cancer, 2008

  5. Yama N, et al. A retrospective study on the transition of radiation dose rate and iodine distribution in patients with I-131-treated well-differentiated thyroid cancer to improve bed control shorten isolation periods, 2012

  6. Braverman ER, et al. Managing terrorism or accidental nuclear errors, preparing for iodine-131 emergencies: a comprehensive review, 2014

  7. Yahyapour R, et al. Radiation-induced inflammation and autoimmune diseases, 2017

  8. Yoshida S, et al. Guidelines for iodine prophylaxis as a protective measure: information for physicians, 2014

  9. Pacini F, et al. Thyroid consequences of the Chernobyl nuclear accident, 1999

  10. IAEA 1991. International Chernobyl Project: Technical Report: Assessment of Radiological Consequences and Evaluation of Protective Measures, 2006

  11. UNSCEAR. United Nations Scientific Committee on the Effects of Atomic Radiation, United Nations, 1988

  12. Cardis E, et al. The Chernobyl accident — an epidemiological perspective, 2012

  13. Ito M, et al. Childhood thyroid diseases around Chernobyl evaluated by ultrasound examination and fine needle aspiration cytology, 1995

  14. Vykhovanets EV, et al. 131I dose-dependent thyroid autoimmune disorders in children living around Chernobyl, 1997

  15. Pacini F, et al. Prevalence of thyroid autoantibodies in children and adolescents from Belarus exposed to the Chernobyl radioactive fallout, 1998

  16. Vermiglio F, et al. Post-Chernobyl increased prevalence of humoral thyroid autoimmunity in children and adolescents from a moderately iodine-deficient area in Russia, 1999

  17. Kimura Y, et al. Evaluation of thyroid antibodies and benign disease prevalence among young adults exposed to 131I more than 25 years after the accident at the Chernobyl Nuclear Power Plant, 2016

  18. Agate L, et al. Thyroid autoantibodies and thyroid function in subjects exposed to Chernobyl fallout during childhood: evidence for a transient radiation-induced elevation of serum thyroid antibodies without an increase in thyroid autoimmune disease, 2008

  19. Najafi M, et al. The melatonin immunomodulatory actions in radiotherapy, 2017

  20. Schaue D, et al. Radiation and inflammation, 2015

  21. Zhao W, et al. Inflammation and chronic oxidative stress in radiation-induced late normal tissue injury: therapeutic implications, 2009

  22. Haddadi GH, et al. Hesperidin as radioprotector against radiation-induced lung damage in rat: a histopathological study, 2017

  23. Yahyapour R, et al. Mechanisms of radiation bystander and non-targeted effects: implications to radiation carcinogenesis and radiotherapy, 2017

  24. Le Guen B, et al. Distributing KI pills to minimize thyroid radiation exposure in case of a nuclear accident in France, 2007

  25. Jang M, et al. Age-dependent potassium iodide effect on the thyroid irradiation by 131I and 133I in the nuclear emergency, 2008

  26. Sternthal E, et al. Suppression of thyroid radioiodine uptake by various doses of stable iodide, 1980

  27. Adelstein S. Intervention procedures for radionuclides, 1991

  28. Federal Drug Administration. Guidance potassium iodide as a thyroid blocking agent in radiation emergencies, 2001

  29. WHO . Guidelines for iodine prophylaxis following nuclear accidents: update 1999, 1999

  30. European Commission . Radiation Protection No. 165—medical effectiveness of iodine prophylaxis in a nuclear reactor emergency situation and overview of European practices, 2000

  31. Spallek L, et al. Adverse effects of iodine thyroid blocking: a systematic review, 2012