Christie Whitman, administrator of the Environmental Protection Agency, said she was asking the National Academy of Sciences to examine the impact of a range of possible reductions.
Mr. Bush had been under fire from environmentalists and others last month when his EPA killed a Clinton administration regulation that would have tightened the standard to no more than 10 parts of arsenic per billion in drinking water. The current standard, set in 1942, is 50 parts per billion.
Whitman said she wanted a panel of scientists at the academy to examine a standard in the range of 3 to 20 parts per billion.
"The Bush administration is committed to protecting the environment and the health of all Americans," Whitman said in a written statement, promising a final regulation within nine months.
She said the decision to seek a report from the academy would "ensure that a standard will be put in place in a timely manner that provides clean, safe and affordable drinking water for the nation and is based on the best science."
The Bush administration's decision on March 20 to stop the regulation put into place three days before the end of the Clinton presidency created an uproar among environmentalists, congressional Democrats and members of the public.
Whitman argued there was insufficient scientific evidence to justify the $200 million annual cost to municipalities, states and industry of meeting the new Clinton standards by 2006.
"I have said consistently that we will obtain the necessary scientific review ... and that we will establish that standard in a timely manner," she said Wednesday.
The administration plans to issue a new regulation that still meets the same timeframe for compliance as the Clinton standard.
In 1999, the National Academy of Sciences said that arsenic in drinking water can cause bladder, lung and skin cancer, and might cause liver and kidney cancer.
The Clinton EPA had initially proposed setting the standard at 5 parts per billion last year in response to a lawsuit by the Natural Resources Defense Council, but then settled at 10 parts per billion.
Environmentalists, who have argued for years that the arsenic standard should be stricter, criticized the EPA on Wednesday for putting off a final decision.
"We're outraged that this is going to assure a year of delays for protection of public health for millions of Americans," NRDC senior attorney Erik D. Olson said.
He said the parameters set by Whitman are "a pretty clear signal" that the EPA is headed toward settling at 20 parts per billion twice the amount that Clinton would have allowed.
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