Why Are Researchers Finding Traces of Radioactive Particles in Baby Teeth?
The meltdown disasters at Fukushima and Chernobyl have solidified the American public's reticence about nuclear energy. The full health significance of these events is still being debated, as government and academic monitoring programs generate a patchwork of data about their impact. And while many studies show that the risks from nuclear power are negligible in the U.S., these two catastrophes continue to raise questions about long-term safety and the cumulative affect of small and large releases of radioactive material. Meanwhile, researchers are attempting to track these contaminants in the food chain, in our bones and even in baby teeth.
Is nuclear power safe? Is it an acceptable alternative to natural gas and petroleum? The answers turn largely on three nagging uncertainties that drive scientists, feed the political debate and worry parents and people who live and work in the shadow of nuclear power plants.
1. Why haven't levels of radioactive contaminants in baby teeth decreased further since the ban on nuclear weapons testing? Strontium 90 is one of hundreds of radioactive byproducts created exclusively by nuclear power generation and the detonation of nuclear weapons. If ingested, it mimics the action of calcium and accumulates in breast milk, human teeth and bones, reaching blood-forming bone marrow where it can damage DNA, blood cells and the immune system. Strontium 90 is a known human carcinogen and has been linked to higher rates of leukemia in people exposed to high doses.
Fallout from nuclear weapons testing in the 1950s and '60s spread Strontium 90 widely throughout the environment. By comparison, nuclear power plants are thought to contribute a minute fraction of this contamination. Public concerns about the health risks ultimately led to the global ban on nuclear weapons testing and an expectation that environmental and human body burdens of Strontium 90 would drop over time.
By 1999, government monitoring programs of Strontium 90 had largely been phased out, based on significant decreases in milk and teeth found in the first four years after the ban went into effect. But a small group of academic researchers conducted followup tests and were surprised to find Strontium 90 in new baby teeth, at levels higher than expected, concluding that there must be some unidentified sources to account for the levels found.
They turned their focus to nuclear power plants. Though tiny by comparison to atomic bomb tests, releases from power plants are not an uncommon result of accidents, planned leaks or releases from incidents the Nuclear Regulatory Commission deems of little consequence.
How much of the Strontium 90 in teeth that comes from these releases and how much is past contamination that’s recycled and further concentrated up the food chain is heavily debated, and the work of the Radiation and Public Health Project has been widely criticized. However, no other studies have been done in the U.S. to challenge the findings which link concentrations in baby teeth to proximity to nuclear power plants.
The studies did not test foods consumed by affected populations and critics point out that FDA’s limited testing as part of national dietary surveys do not find similarly persistent contamination in dairy and other high-calcium foods that were so heavily affected by nuclear weapons tests. So it’s not possible to know how much food accounts for higher levels in baby teeth. Tooth studies in Greece, England and Ukraine also report findings that suggest contributions of Strontium 90 or other radioactive contaminants are coming from sources other than nuclear weapons.
2. Do we know enough about the potential health impacts from recent nuclear plant disasters? Health impacts are determined in two parts—measuring exposure and tracking exposure-related health effects in exposed animal and human populations. These efforts have largely been split among many government agencies and academic institutions, with apparently little integration or coordination. Nuclear plants also conduct limited monitoring that critics consider grossly inadequate. NRC just recently announced plans to revise the regulations for how radiation dose is calculated, how it is measured and how radioactive effluents are reported annually.
National averages reported for foods tested to date are well below quantities that would be considered a health threat. Still, the American Medical Association and other advocates are calling for more comprehensive ongoing tests, both in Japan to characterize fully the health risks from Fukushima and its impact on the Japanese food supply, and in the U.S. to rule out possible pockets of contamination that may emerge from unreported releases from U.S. nuclear power plants or atmospheric drift from the incident in Japan. Recent tests by researchers at Oregon State University have identified minute, but significantly increased levels of radioisotopes in albacore tuna that trace back to the Fukushima reactor meltdown. Researchers are undertaking a larger study.
Tracking levels over time is important since these substances persist in the environment. Results from the baby tooth studies suggest levels are higher in the teeth of children living near nuclear plants and that higher cancer rates track with levels detected. These findings are discounted by some experts who say the study suffers from deficiencies in methods and inadequate peer review. Nonetheless, no published studies have attempted to replicate or challenge these findings. NAS recently established a new comprehensive program to evaluate data and methodologies for assessing health risks from five nuclear plants operating in the U.S. and is scheduling public meetings in the communities being studied to engage local residents.
3. What is the likelihood of more disasters like Fukushima and Chernobyl? Fallout of Strontium 90 aside, experts are split on the question of operating safety of aging plants and whether or not new technology can make future plants free from all possibility of a nuclear meltdown. A notable skeptic is the former head of the Nuclear Regulatory Commission, Gregory Jaczko, who recently argued that future incidents like Fukushima are” inevitable,” unless existing plants undergo major redesign to make sure facilities can contain any releases that might be possible in worst-case scenario accidents.
A similarly cautionary message comes in a new report from the National Academies of Science that examines lessons learned from Fukushima. It makes an urgent call for more pro-active efforts by regulators and operators of licensed reactors to seek out new information on hazards and take aggressive action to start more effective measures to improve safety. Published in July, the congressionally mandated report was particularly critical of failure of existing safety programs to consider unlikely events, known as “beyond design-basis” accidents, deemed a prominent cause of disasters at Fukushima, Chernobyl and other serious accidents examined by the NAS committee. Other recommendations focused on the need for greater offsite emergency response preparations.
Right now, the Nuclear Regulatory Commission is renewing licenses to existing plants that extend their operating life decades beyond their original design and new efforts are underway to win approval to build new plants, both here in the U.S. and elsewhere. The latest research is focused on finding ways to design smaller scale reactors with more safeguards against accidents, and to find ways to lower the amount of waste that’s created and develop more secure containment systems.