03/07/2011 - 17:47

Incisors in the heartland

Joseph J. Mangano

Joseph J. Mangano

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Since 1996, supporters have pushed for Senate ratification of the Comprehensive Test Ban Treaty (CTBT), arguing that the treaty would limit nuclear weapons proliferation and deter nuclear war. But the treaty does more than this -- it also has a health benefit. Put quite simply: No more tests, no more fallout.

Precisely calculating health fallout has been a challenge since the atomic age began. Much research has focused on the health consequences from high doses of radiation, but little has concentrated on low doses, like fallout. And though this challenge still exists, some understanding has been gleaned in a rather unlikely place -- baby teeth.

Radioactivity as a neighborhood concern. Soon after large-scale US atmospheric nuclear weapons tests in Nevada and the south Pacific began in 1951, the former US Atomic Energy Commission began testing strontium 90 concentrations in bones obtained from autopsies in the US and Europe; this nascent research found geographic variations and greater concentrations in infants and children. Decades later, the public learned that the commission program violated ethical practices by not requesting permission from families in the United States to test tissue samples from cadavers.

Although strontium 90 is just one of more than 100 radioisotopes in bomb fallout, it quickly became the chemical of choice when researching nuclear effects on humans. Its physical half-life of 28.7 years makes it detectable for a long period after a bone or tooth leaves the body. But strontium 90 was also recognized as harmful, even compared to other fission products. Its beta particles can penetrate into bone marrow, where red and white blood cells crucial to the immune response are formed.

Public concern over strontium 90 rose as testing continued. In 1956, Democratic presidential nominee Adlai Stevenson declared it to be "the most dreadful poison in the world. For only one tablespoon equally shared by all the members of the human race could produce a dangerous level of radioactivity in the bones of every individual."

An article printed in a November 1956 issue of Newsweek stated that "the testing of hydrogen bombs may have already propelled enough strontium 90, the most pernicious aftermath of nuclear fission, into the stratosphere to doom countless of the world's children to inescapable and incurable cancer."

With the Atomic Energy Commission bone program largely unknown to the public, the call for a comprehensive study of human radiation effects was raised. In August 1958, biochemist and federal official Herman Kalckar wrote an article in Nature proposing an international and long-term program using baby teeth. Kalckar noted that young children "take up radioactive strontium and caesium more intensely than adolescents and adults … and … have higher biological radiosensitivity."

Looking for answers in St. Louis. Just months after Kalckar's article, the Greater St. Louis Citizens Committee for Nuclear Information commenced a study of strontium 90 patterns in baby teeth. The non-profit organization not only included people from the area, but scientists from Washington University. Tooth donations were solicited by distributing forms to schools, libraries, churches, dentists, and dental clinics, and through advertisements.

When the study ended in 1970, over 300,000 teeth had been collected. While the US Public Health Service contributed funds, volunteers handed out forms, collected information from parents, and distributed buttons to children stating "I Gave My Tooth to Science."

Lab testing was conducted by the Washington University School of Dentistry, and research results were published in several professional journals. Average strontium 90 levels in St. Louis teeth were higher than in most American and Canadian areas studied, reflecting greater cumulative uptake from all atmospheric tests. The research also suggested that the average St. Louis child born in 1963 had 50 times more strontium 90 in their teeth compared to those born in 1950.

The tooth study entered the policy arena when Washington University physician Eric Reiss presented results in testimony to the US Senate in favor of the 1963 Partial Test Ban Treaty. At this same time, other studies examining strontium 90 in baby teeth were conducted in what was then Czechoslovakia and West Germany, as well as Denmark, Finland, Norway, and the United Kingdom. All countries found sharp increases during nuclear testing and sharp reductions after the treaty went into effect. The US government discontinued funding for the St. Louis study in 1970.

Assessing cancer risk from fallout. The health risk to humans from fallout during the bomb test era -- especially to the baby boomers -- was a concern to many. A 1960 Newsweek article on the St. Louis tooth study asked: "But what about the children who have done their growing while strontium 90 levels were high -- are they liable to develop cancer?" Despite these concerns, the Washington University effort did not use baby teeth to assess health risk from fallout. The only federal studies on the topic, neither of which were published in peer reviewed journals, are a 1999 estimate of 49,000 mostly non-fatal cases of thyroid cancer and a 2002 estimate of 15,000 total cancer deaths nationwide.

In 2001, Washington University professors discovered 85,000 teeth, which were not used in the original study. These teeth, stored in a remote ammunition bunker near St. Louis, were each enclosed in a small envelope, which identified the tooth donor and characteristics of the tooth. The school donated the teeth to the Radiation and Public Health Project, a non-profit organization of which I am the executive director.

Using a sample of teeth from 3,900 donors, our group identified baby boomers born and raised in St. Louis who subsequently developed cancer. A case-control study comparing strontium 90 levels of people with and without cancer in Missouri was conducted: Those baby boomers who had died of cancer by age 50 had more than twice the strontium 90 concentration in their baby teeth than did healthy controls. But these studies are not yet conclusive, and more are planned for the future.

Looking to the future. Calculating how many Americans developed cancer from fallout remains a daunting task.  But health studies of fallout and disease prevention have a current importance even though US atmospheric and underground nuclear tests ceased in 1963 and 1992, respectively. Senators who have opposed ratifying the CTBT, preventing the US from joining the list of 153 ratifying nations, can learn a lesson from tooth studies. Health hazards of nuclear weapons use may be most dangerous during a nuclear war, but also exist when weapons are tested.