BRATTLEBORO -- Since Entergy learned that a leak of tritiated water has been contaminating groundwater beneath the Vermont Yankee nuclear power plant in Vernon, many people have been wondering just how dangerous tritium is.
Well, that all depends on who you talk to.
Representatives from the Nuclear Regulatory Commission have stated repeatedly that a member of the public has to ingest massive quantities of tritium over a long period of time to be affected by it.
But groups such as the National Physicians for Social Responsibility and Citizen Awareness Network say that tritium, like other radionuclides, is a serious threat to the health of humans and the environment.
Tritium, which is a beta emitter, causes cancer and birth defects, said Ira Helfand, a doctor at Cooley Dickinson in Northampton, Mass., and the co-founder and a former president of National Physicians for Social Responsibility
Helfand's biggest concern is that tritium can cross the placental barrier. This was confirmed in animal studies, as documented by the United Nations Scientific Committee on the Effects of Atomic Radiation.
"Several statistically significant effects were found at various (tritium) levels, in no apparent relationship with dose," it stated. "These included microcephaly (shrunken heads, also observed at Hiroshima), sterility, stunting, reduction of the litter size, ..."
While it's not known for certain whether tritium causes birth defects and cancer in humans, said Helfand, it is well known that enormous amounts of tritium are dangerous and even at the levels detected at Yankee it is dangerous.
"It absolutely can hurt you," he said. "To say it can't hurt you is irresponsible. It indicates the bias and the agenda of our current regulatory agencies -- not to regulate but to promote."
The only way to protect the public at this point, he said, is to shut down the plant and not allow any more tritiated water to escape into the environment.
The Citizen Awareness Network calls the levels of tritium in groundwater at Yankee "alarming."
The levels recorded there are 120 times the EPA's safe drinking water limit.
"As with all ionizing radiation, exposure to tritium increases the risk of developing cancer and genetic effects, including developmental abnormality and reproductive effects," stated CAN.
Of course tritium is hazardous, said John White, Region 1 Branch Chief of the NRC during a conference call with the media, as is any nuclear isotope.
But the question of danger hinges on quantity, he said.
At Yankee, there are very small quantities of tritium involved, said White, adding one picocurie is one-trillionth of a curie. The worldwide production of tritium from natural sources total 4 million curies per year, he said.
The NRC and Entergy have repeatedly stated that the leak discovered at Yankee currently poses no threat to general public because it has not shown up in nearby drinking water wells and no detectable levels of tritium have been found in the Connecticut River.
But if it does, warned the Canadian Coalition for Nuclear Responsibility, the cumulative effects can be hazardous to human health.
"In the case of cancer, leukemia, and genetic damage, the scientific consensus is that every additional exposure to radiation adds to the total risk and therefore to the incidence of these diseases in exposed populations," according to a document produced by the CCNR.
But a local hobbyist, who built his own Geiger counter as a youth and recently purchased a scintillator so he could take radiation readings around the county, said people should be more worried about other sources of radiation in the environment rather than tritium in groundwater.
The human body alone contains 120,000 picocuries of radionuclides, he said, exposing us all to 24 millirems every year, said Ira Wilner, of Putney.
Naturally occurring radiation averages about 360 millirems. Vermonters are exposed to greater amounts of radiation, up to 450 millirems a year, due to radon in granite.
In comparison, if someone was to drink two liters of water with 20,000 picocuries of tritium every day, which is the Environmental Protection Agency's drinking water limit, they would be exposed to 4 millirems a year.
Tritium levels in one of the groundwater monitoring wells at Yankee peaked at 2.5 million picocuries. A steady diet at that level would result in an additional dose of about 520 millirems a year, said Wilner.
"While not in itself a dangerous level, it would in effect be doubling your normal annual background level," said Wilner. "You would want to avoid (drinking it) even though the risks are still very small at that exposure level."
And there are other sources of radioactive materials that humans expose themselves to each day, said Wilner.
A full torso CAT scan for medical diagnostic purposes might expose you to 2,400 millirems in a few minutes from that one procedure alone.
Coal fired plants emit more radioactive dust into the atmosphere than nuclear power plants, including trace amounts of uranium, thorium, potassium and radium, according to the Environmental Protection Agency.
Fly ash, generated by coal-fired power plants, is mildly radioactive and is often used in concrete and asphalt.
Even wood ash from your home fireplace is slightly radioactive. Because of above-ground nuclear weapons testing in the 1950s and 1960s, strontium and cesium settled into topsoil, which was eventually taken up by trees and other forms of vegetation.
Tobacco smoke is also radioactive because the tobacco leaf absorbs minerals from the earth.
"I think we need to keep the tritium leak in perspective," said Wilner. "At this moment it is not great enough to require VY to go off line. But it is of sufficient concern to question the physical integrity of this aging power plant and the integrity of its owner."
Wilner is self educated. He said what he has learned about radiation is available to any member of the public, either on the Internet or in the library.
But a nuclear expert put the danger of tritium into his own perspective.
"I don't think it poses a risk any greater than two or three packs of cigarettes a day," said Paul Blanch, who has worked in the nuclear industry for more than 40 years and opposes the relicensing of Vermont Yankee.
Bob Audette can be reached at firstname.lastname@example.org, or at 802-254-2311, ext. 273.