Preserving Deciduous Teeth Network (PDTN) 

   HOME | Our Appeal | Our Activities | Sr-90 | Establishing Our Measuring Facility 
Our Supporters | Bibliography | Charts | Message to Children | News | Japanese

What is Strontium 90?

Strontium-90 (Sr-90) behaves very much like calcium when it is inhaled or ingested; it is absorbed into bones and teeth where it accumulates.

When the embryo is about five to six weeks old, tooth buds already begin to appear. The vast majority of babies sprout their first tooth when they are six to eight months old. Sr-90 gets deposited not only in bones, but also in teeth.

Starting at around age six, the full set of 20 baby teeth start to fall out, to be replaced by permanent teeth. Sr-90, owing to its half-life of 29 years, will remain in the shed teeth for a long time. Once the milk teeth are preserved, we can measure contamination-levels of Sr-90 at any time, from which we can determine the level of radiation your child has been exposed to.

Do you know that nuclear weapons tests were performed from the 1950s to the 1960s, especially in the South Pacific area, that caused the release of radionuclides, including Strontium-90? It was carried around the globe by atmospheric circulation and eventually reached Japan. Sr-90 can cause leukemia, immunodeficiency and other non-cancer diseases. That is why Japan conducted surveys across the nation to measure Sr-90 levels in the atmosphere and in milk teeth, as the graph below shows.

''Studies on the Accumulation of Radionuclides (Strontium, Plutonium) in Human Milk Teeth as a Result of the Fukushima No.1 Nuclear Power Plant Accident '' published by Japanese Journal of Clinical Ecology in 2013 (in Japanese )
Authors: Kazuhiko Inoue, Ichiro Yamaguchi

●Large Size

As you can see, the amount of radioactive fallout correlated with Sr90 levels in the milk teeth. Also, Sr90 levels in the teeth differed depending on the type of nutrition the infants received.

As a result of the TEPCO Fukushima Daiichi Power Plant accident, significant amounts of artificial radioactive materials were released into the environment, contaminating the atmosphere, waters (groundwater, rivers, lakes and marshes, oceans), soil, natural ecosystems on a global scale. At the Fukushima site, large amounts of groundwater flow into the damaged containment buildings where it mixes with severely contaminated water and then runs off into the sea.

After the Fukushima catastrophe Japanese researchers conducted surveys on the distribution of artificial radionuclides in animals' bones and deciduous teeth. Results from those surveys showed that high levels of Strontium-90 were present especially in the teeth of young animals, such as cattle, pigs, field mice and monkeys.

We are very much concerned at the strong possibility of the same thing happening to humans. That is why we propose to you to keep your children's shed milk teeth. This is to keep a close watch on the health of your children.

Currently in Japan, there are no facilities available to measure Sr90 levels. Therefore, we are planning to establish such facilities. However, it will take some time till before they will be ready to start up.

From now on we need to cooperate with one another to protect our children.

So, first of all, let's preserve the shed milk teeth together with the personal record cards!