Tests by a privately funded anti-nuclear group found that South Florida children's baby teeth contain concentrations of radioactive Strontium-90 that rival those measured in the early 1960s, when the United States still conducted above-ground nuclear weapons testing, a study released Wednesday says.

The group responsible for the findings, the Radiation and Public Health Project, thinks that emissions from South Florida's two nuclear power plants -- Turkey Point and St. Lucie -- are the only plausible source of the man-made carcinogen. The plants' owners, Florida Power & Light, dispute the study's accuracy.

The study collected 86 baby teeth from Miami-Dade children born between 1980 and 1994. Those teeth showed an average Strontium-90 concentration of 2.21 picocuries per gram of calcium, the highest of six regions that the project has focused on to date. The group plans to turn its attention to other South Florida counties and send letters to 10,000 parents asking them to collect their children's baby teeth for further research.

Dubbed the "Tooth Fairy Project," the study suggested a link between the nuclear power plants' emission levels and subsequent fluctuations in the rates of bone, blood, breast and childhood cancer. Strontium-90 is one of a number of radioactive byproducts produced by nuclear fission. The substance does not occur in nature. It is treated by the body much like calcium, causing it to be taken up into developing bones and teeth.

The nuclear industry responded with swift criticism of the report, accusing its authors of skewing their findings to frighten the public and to further a political agenda. Turkey Point in Homestead is seeking a 20-year renewal of its license, and a decision from the U.S. Nuclear Regulatory Commission is expected in August.

"These are scare tactics, and the agenda is to shut down nuclear power plants when they have been shown to be safe, clean and economical sources of power," said Rachel Scott, a spokeswoman for Florida Power & Light. "The most important issue here is that there is no credible scientific evidence that these levels of Strontium-90 create any ill health effects."

The latest results from the Tooth Fairy Project were released before they were reviewed or accepted by an independent scientific journal. That makes its findings suspect, said Thelma Wiggins, a spokeswoman for the Nuclear Energy Institute, a Washington-based nuclear advocacy group. "Strontium-90 is rare in baby teeth today, and it is unrelated to nuclear power plants," Wiggins said.

The authors of the report include Carter-administration science adviser Jay Gould, Florida International University environmental studies professor Jerry Brown and Ernest Sternglass, an emeritus radiological physics professor at the University of Pittsburgh Medical School.

The authors called on the U.S. Nuclear Regulatory Commission to consider the project's findings before extending the license of Turkey Point or any of the nation's other aging nuclear reactors.

The authors found that the teeth from Miami-Dade County contained 2.21 picocuries of Strontium-90 per gram of calcium, compared to 1.55 picocuries per gram in Westchester County, N.Y., and 1.38 picocuries per gram in Suffolk County, N.Y..

They looked at early childhood cancer rates and found Miami-Dade's were the highest of those areas, as well. There were 25.65 cases of cancer per 100,000 in children under 4 between 1985 and 1996 in Miami-Dade County. The national average during that time was 20.2 cases per 100,000, the authors said.

Further, they tracked a rise and fall in cancer rates that corresponded with the rise and fall of emissions from the reactors.

In 1983 and 1984, when the Turkey Point reactors were mostly closed for repairs, infant deaths in Broward and Dade Counties fell 19.1 percent, compared to a drop of 6.4 percent nationwide, the study reported. The following two years, when Turkey Point returned to full power, the local infant death rate rose 1.2 percent.

In 1983-84, the first two years that the St. Lucie 2 reactor operated, infant deaths in St. Lucie County rose by 35.3 percent, the report found.

The federal government conducted baby tooth testing for Strontium-90 between 1950 and 1970, and smaller scale tests until 1982. Gould called on the government to resume the tests.

Stacey Singer can be reached at ssinger@sun-sentinel.com or 561-243-6616.