Answer to Question #14261 Submitted to "Ask the Experts"

I lived on Kwajalein from 1957 until 1960 and I have been diagnosed with thyroid cancer. Both of my parents had cancer. Could it have been from radiation from bombs set off in the Marshall atoll?

For your information, I am a trained radiation physicist and I personally lived in the Marshall Islands in the 1990s for the purpose of measuring the residual radiation from the nuclear testing atolls, on all the atolls of the country including Kwajalein.

One of the first important points for you to understand is that radioactive fallout from nuclear testing is a complex mixture of many radioactive substances, each with a different half-life. The half-life indicates how long each radioactive substance will exist and could expose a person. After about three or four half-lives, the radioactive material has largely decayed away. In the case of exposure of the thyroid gland, the most important radioactive substance is iodine-131 (¹³¹I) with a half-life of about eight days. That means after one month, the radioactive iodine would mostly be gone. There is also a small radiation exposure from the other radioactive materials, but I will include all of those in my analysis below.

A second important concept is: Where did the radioactive fallout go from each nuclear test that took place when you lived there? The radiation moves through the air as determined by the direction of the wind. For that reason, Kwajalein only received radiation when the wind was blowing to the south and that was relatively unusual.

To answer your question specifically, there are three important questions: (1) exactly when were you resident on Kwajalein, (2) how old you were at the time you resided there, and (3) when did the nuclear tests take place that might have affected you and where did that fallout radiation go?

According to your letter, you resided in the Marshall Island from 1957 until 1960.

• So, first, I will assume you lived on Kwajalein all of 1957, 1958, and 1959.
• Second, I will assume you were a child then rather than an adult.
• Third, there were no nuclear tests in the Marshall Islands and the last year of testing was 1958. In scientific publications I wrote and published in 2010 in Health Physics, we analyzed the direction of the fallout from each detonation and determined that fallout from only one of the six nuclear tests conducted in 1958 deposited fallout on Kwajalein. That test, named Fir (after the type of tree) took place on 12 May 1958 and was a small nuclear test.

Additionally, we analyzed the radiation dose received by a child on Kwajalein in each year from radioactive fallout from all previous tests (Simon et al., 2010, Fig. 3). If I add the doses received by the thyroid gland of a child on Kwajalein in 1957, 1958, and 1959, I estimate a thyroid dose of about 1.1 mGy.

To give a perspective on what that dose means, it is less than the typical dose received from natural background radiation in one year for people living in, for example, the United States. You should know that in the US, background radiation is higher than in the Marshall Islands because of uranium and other natural elements in the soil (which are very low on the coral atolls of the Marshall Islands). Because the dose I estimated for you is less than the typical dose received in one year in the United States, it is my professional opinion that if you did develop thyroid cancer later in your life, it was not related to exposure you received on Kwajalein from radioactive fallout.

Unfortunately, today there are about 44,000 new cases of thyroid cancer identified in the United States alone in a single year. People develop thyroid cancers, and other types of cancer as well, for many reasons that are not understood. Most, of course, are not related to radiation. I sincerely hope that your thyroid cancer is well controlled.

To determine the chance that any cancer your parents may have developed was related to fallout radiation, I would need additional information about the type of cancer, their age when on Kwajalein, and age when cancer first developed. However, Kwajalein was continually occupied during the nuclear testing period because, in part, it was not located in the typical wind direction from the nuclear test sites on Bikini and Enewetak. For that reason and because of the low recorded fallout on Kwajalein in the years 1957 to 1960, and because cancer occurs at such high rates in people everywhere, I do not consider that your parents were at any high risk from exposure they received while residing on Kwajalein.

I hope this information and analysis is useful.

Steven L. Simon, PhD, FHPS

Reference
Simon S, Bouville A, Land C, Beck H. Radiation doses and cancer risks in the Marshall Islands associated with exposure to radioactive fallout from Bikini and Enewetak nuclear weapons tests: Summary. Health Phys 99:105–123; 2010. doi: 10.1097/HP.0b013e3181dc523c.