WASHINGTON -- Conceding there's no way to know what life will be like in a million years, the Environmental Protection Agency nevertheless proposed limits yesterday on how much radiation a person should be exposed to from a nuclear waste dump in that distant time.
The guidelines would limit exposure near the proposed Yucca Mountain facility in Nevada to 15 millirems a year for 10,000 years into the future, but then increase the allowable level to 350 millirems for up to 1 million years.
That higher level is more than three times what is allowed from nuclear facilities today by the Nuclear Regulatory Commission.
A standard chest X-ray is about 10 millirems.
Asked whether there was any way to assure such a standard would be relevant or be met that far in the future, the EPA's Jeffrey Holmstead replied, ''We do the best job given all the science we have."
The radiation exposure issue has threatened to cripple the government's plans to bury 77,000 tons of highly radioactive waste -- mostly used reactor fuel rods now at commercial power plants -- beneath a volcanic ridge at Yucca Mountain in the Nevada desert 90 miles from Las Vegas.
A year ago a federal court said the EPA standard, which is supposed to ensure nearby residents won't be harmed by leaking radioactivity from the dump, was inadequate because it didn't establish exposure limits beyond 10,000 years.
Yesterday, the EPA announced a revised standard that reaches out to a million years.
''That's longer, many times longer than human history," said Holmstead, adding that he's certain the rule will protect the public. Once the standard is made final after a comment period, the Nuclear Regulatory Commission will decide whether the Yucca facility's design is adequate to meet it.
''We're setting a standard that not only protects our children, our grandchildren . . . it will protect the next 25,000 generations," said Holmstead.
But opponents of the Yucca waste project, including state officials in Nevada, saw it differently.
''In short they've decided to kill a few people," said Joe Egan, an attorney who represented Nevada in the court fight over the project. ''This is an obvious effort to give the project a pass" after the 10,000-year period.
Egan said the standard would allow as much as 700 millirem of radiation exposure a year, when added to the 350 millirem of natural background radiation in the Yucca area. The NRC, which must still approve a permit for the Yucca waste site, limits public radiation exposure from nuclear facilities it licenses to no more than 100 millirems per year.
Holmstead, who is the EPA's head of air and radiation office, said a person living near the Yucca site will not be subjected to radiation ''higher than people are routinely exposed to throughout the country" from natural background sources.
But Arjun Makhijani, a nuclear physicist who has been critical of the Yucca project and other government nuclear programs, called the standard ''lax" and too vague and said to link Yucca Mountain exposure standards to background radiation is misleading if -- as the EPA does -- one includes radiation from naturally occurring radon.