WASHINGTON, April 17 (UPI) -- (Editor's note: This is the fourth and final article in a four-part series from United Press International examining some of the scientific issues related to using Nevada's Yucca Mountain as a nuclear waste repository site. Congress has started a 90-legislative-business-day period where it must vote to override the state's objections to continue the project. The House Energy and Commerce Committee is to hold a hearing on the project on April 18.)
Discussions of the proposed nuclear waste storage site at Yucca Mountain throw around a dizzying array of numbers and projections for possible radiation exposures, yet the talk does little to educate the general public, scientists say.
Such an incomplete understanding often leads to the misperception there are such things as "good" and "bad" sources of radiation, said Keith Dinger, a past president of the Health Physics Society.
"The source of radiation is irrelevant to any risk or harm that it might carry," Dinger told United Press International. "The general public readily accepts, for the most part, radiation associated with medical procedures ... and background radiation without question or concern. But if it's from an industrial source, there seems to be a perception that somehow it's riskier or more hazardous than these other sources."
Such perceptions affect public opinion of projects such as Yucca. Nevada Gov. Kenny Guinn, a Democrat whose veto forces Congress to vote to approve or deny the project, told UPI polls in his state consistently have shown about three-quarters of the respondents do not want the site under any circumstances.
"Industrial" sources such as nuclear power plants contribute less than a quarter of the average American's annual radiation dose, Dinger said. Many people are not even aware of their constant exposure to radiation regardless of where they are, he said.
Background radiation levels rise slightly with altitude, including when airplanes fly above the protection of Earth's lowest atmospheric levels. Yet this fact is readily accepted, said Martin Apple, president of the Council of Scientific Society Presidents in Washington.
"(Published reports have) talked about the exposure you get on an airplane trip, and how much that accumulates if you fly coast to coast," Apple told UPI. "It's not zero, and it could accumulate, but I didn't even hear the flight attendants make a fuss over that."
Even people who regularly deal with radiation seem to have an incomplete understanding of the subject, Apple said. An informal survey of dentists and hospital X-ray technicians showed they often are unaware of how much radiation is involved in each image they take, he said.
The common understanding of regulated radiation limits, from sources such as the Environmental Protection Agency, is also skewed, according to Dinger. Such limits are seen as an instant demarcation line between safe and unsafe but they are designed to deal with decades-long exposure scenarios not a one-time event, he said. EPA is trying to protect human life, but its approach does a real disservice to the public, Dinger said.
"They have some publications where you can calculate the chances that a single atom of a certain radioisotope will cause you lung cancer," Dinger told UPI. "The public thinks that if you can put a risk number on it, the number doesn't matter. 'There's a risk and I don't want it.' It's that attitude that (the HPS) thinks is misleading and there isn't any validity in those numbers."
It is the actual amount of radiation received over time or dose that accurately represents the amount of harm an exposure might cause, Dinger said. Ongoing studies support the conclusion among many scientists there is a lifetime dose below which harmful effects cannot be quantified. Assigning a risk to exposures less than that is premature, he said. The dose, 10 rem, is equivalent to decades of normal background exposure.
Department of Energy calculations suggest that even if waste escaped from Yucca into the groundwater at some point, the closest humans would receive a annual dose of about 15 millirem or thousandths of a rem.
Nevada officials, however, said so many uncertainties are involved in DOE's numbers the actual dose could vary from 15 rem to a small fraction of a millirem.
Part of the problem in determining risk is that living organisms, including humans, have developed mechanisms to deal with radiation, said David Bannon, a physics professor at Oregon State University.
"(The skin pigment) melanin is one, then of course the cells have the ability to repair damage," Bannon told UPI. "There's a certain level of radiation that biological systems on Earth are used to dealing with."
These defense mechanisms have helped shape humans into their current evolutionary form, Apple said.
"As with all human properties, there's a distribution curve," Apple said. "Some of us are at one end, where we can sit on a garbage pile of radioactive stuff and nothing will happen; some of us are at the other end."
When considering issues involved with radiation, as with all decisions in life, people should consider the benefits that accompany the risks, said Dr. Henry Royal, president-elect of the Society for Nuclear Medicine who practices nuclear medicine in St. Louis. Discussions on nuclear power and dealing with waste often omit possible benefits, improperly magnifying the risks, he said.
"I don't think the public has made terrible decisions in the past," Royal told UPI. "Nuclear power is an environmentally good way of producing energy. I think the public's resistance to it has been reasonable in that it's much better to encourage conservation than it is to build more plants. But there will come a time when existing plants will have to be replaced or more power is needed. It'll be very interesting to see what happens (to public opinion) when you can't conserve any more."
For people who want more information concerning radiation exposure and its effects, Dinger suggested visiting the HPS Web site at hps.org, where questions are directed to accredited experts in the field. An archive of existing questions and answers also is available, he said. Whenever people seek out such information, they should either find impartial sources or understand the biases of available sources, he said.