The atomic age began with the use of nuclear weapons on Japan during World War II, followed by a race (mostly between the United States and Soviet Union) to develop large stockpiles of weapons. This development included detonation of over 400 bombs into the atmosphere, which ended with the Partial Test Ban Treaty of 1963.
Scientists and political leaders became concerned with accumulating fallout from these tests in human bodies, and the health threats they presented. The initial attempts to test in-body fallout concentrations were measurements of Strontium-90 in human bone by the U.S. government starting in 1953. These attempts were laborious, requiring the securing of bones from autopsy.
Starting in 1957, the U.S. began a program measuring radioactivity in food and water. Samples were relatively easy to collect, but still left the question of how much radioactivity was entering human bodies unanswered.
In 1958, in the midst of large-scale testing, U.S. health official Herman Kalckar wrote an article proposing a “census” of radioactive Strontium-90 in deciduous (baby) teeth to measure fallout. Strontium-90 is only produced after splitting uranium-235 atoms, in bomb tests and nuclear reactors. Similar to calcium, it is taken up in bone and teeth after consumption in food and water.
Sr-90 in teeth became a logical way to measure in-body fallout. It has a half-life of 28.7 years, remaining in the body for a lifetime. Furthermore, baby teeth can be easily accessed through voluntary donations after they are lost, rather than through rigorous processes such as autopsy, biopsy, and blood testing. Finally, Sr-90 can penetrate the bone marrow, where the white and red blood cells crucial to the immune function are formed, making it a risk for all cancers.
During the period of atmospheric testing, studies of Sr-90 in baby teeth were conducted by scientists in several European nations. The largest such study, however, occurred in St. Louis, USA, entitled the Baby Tooth Survey. Starting in late 1958, soon after the Kalckar article, collaboration of Citizens for Nuclear Information and Washington University faculty collected about 320,000 baby teeth, mostly from the St. Louis area, but also from other parts of the U.S.
Study results, which were published in several medical journals, were also an integral part of the 1963 Test Ban treaty. Results were shared with President John F. Kennedy and were included in testimony to the U.S. Senate supporting the treaty. The study found a 50-fold increase in average Sr-90 concentrations in Americans born in 1963 (the height of testing), compared with those born in 1951 (the start of testing). In 1970, after 12 years of work, the study ended.
Background – Baby Tooth Studies Also Used in Tracking Nuclear Plant Emissions
In the mid-1990s, a study measuring radioactivity in baby teeth near the Sellafield nuclear plant in northern England found that plutonium levels were highest in children living nearest the plant, but did not observe such a pattern with Sr-90.
In late 1996, the non-profit New York-based research group Radiation and Public Health Project (RPHP) embarked on a study of Sr-90 in baby teeth called the Tooth Fairy Project. Modeling its project on the St. Louis study, the project tested 5,000 teeth, largely near six U.S. reactors.
Results found average Sr-90 was 30 to 50% higher in children living closest to reactors, and found averages rose 35 to 60% from children born in the early 1980s to the late 1990s. Finally, the group published information showing that Sr-90 trends in baby teeth were similar to trends in cancer diagnosed in pre-school children several years later – the first attempt to assess health effects of in-body radioactivity.
Discovery of Large Collection of Baby Teeth Enables Long-Term Health Studies
In 2001, a group of Washington University officials found about 85,000 baby teeth from the original study in storage. The school donated the teeth to RPHP. Each tooth is secured in a small manila envelope, attached to a 3 x 5 card with information describing the tooth and identifying the tooth donor.
The discovery made national headlines. Articles appeared in numerous publications, including the New York Times and Washington Post. RPHP made clear that its intention was to use the baby teeth to analyze any patterns of disease and death later in life – an area that the original St. Louis study had not explored.
One study of a small sample of teeth was published in a medical journal in 2010. The study showed that the average Sr-90 concentration in teeth of donors who had died of cancer by age 50 was more than double that of donors of the same age who were healthy at age 50.
Current and Future Plans for Baby Tooth Studies
In late 2019, Harvard University secured a five-year grant from the National Institutes of Health to conduct research using the St. Louis baby teeth. RPHP, which retains ownership of the teeth, is a sub-contractor in the grant. Year 1 is dedicated to entering information on the 3 x 5 cards into a computerized spread sheet, making planning future research projects much simpler.
While Harvard’s primary interest is to study later life health hazards from childhood exposure to heavy metals, RPHP remains dedicated to using the teeth to measure health risk from exposure to man-made radioactivity. As of late 2020, planning for research using the teeth is focused on a comparison of Sr-90 in St. Louis teeth (those exposed early in life to bomb fallout) and Sr-90 in current children living near nuclear reactors (those exposed early in life to reactor emissions).
Understanding “Baby Boomer” cancer patterns throughout much of their life (most tooth donors are now age 55 to 65) can be a means of predicting the future cancer burden on today’s children. Plans are also under way to encourage use of the tooth collection by scientists to study effects of in-body toxic chemicals.