WASHINGTON— HOW could the Environmental Protection Agency decide that the life of someone over 70 years old is worth $1.4 million less than the life of a younger person?

Christie Whitman, the E.P.A. administrator, preferred to duck the question, when asked why a cost-benefit analysis of a clean-air proposal valued the life of a person under 70 at $3.7 million, and a person over 70 at $2.3 million. Instead, after protests this spring over the ''senior death discount,'' Ms. Whitman disavowed the numbers and said that henceforth all Americans would be equal in her eyes.

That was an understandable political response, but it dismayed the researchers who divine the precise monetary value of every stage of life. Their number-crunching may seem the modern equivalent of determining how many angels can dance on the head of a pin, but they are far more conscientious than any medieval philosopher. They have spent careers agonizing over every dollar in the estimates buried in the appendices of federal reports. Now, because of political pressure, the E.P.A. is trying to pretend their work doesn't exist.

Give them their due. Let them explain how much your life is worth to you.

Analysts at the E.P.A. once made the uncontroversial assumption that every life saved by cleaning up the environment was equal. To compute the value of each life saved, they relied mainly on studies of how much extra money workers demand for risking their lives in dangerous occupations like mining or fishing.

The methodology is complex, but it goes something like this:

Suppose that a worker digging in a coal mine earns $6,000 more than a comparable worker above ground, and that the miner has a one-in-a-thousand greater risk of dying on the job. So for every worker killed underground, the mining industry pays an extra $6,000 apiece to 1,000 workers, which adds up to $6 million. Economists call this total the ''value of a statistical life'' (even though they know that none of those workers would really agree to die in exchange for $6 million).

That happens to be close to the actual figure -- $6,120,000, to be exact -- that the E.P.A. valued each life that could be saved through the Bush administration's ''Clear Skies'' proposal to reduce pollution from power plants. But the E.P.A. analysts also included an alternative estimate, derived from an international assortment of scientific studies asking consumers how much they would pay for safety.

These consumers, who were given a primer in the statistics of risk, were polled on how much they would pay for an improved air bag, for example, or on whether they would choose a bargain-priced bus or a pricier one with a better safety record. By figuring out precisely how much money consumers would pay for a product that would save 1 of every 1,000 lives, researchers could calculate the value of that statistical life -- on average about $3 million. This is only half the value of the E.P.A.'s traditional calculation using workers' wages.

Another twist lowered the benefits of cleaner air even further. Instead of assuming that all the lives saved were typical middle-aged workers who valued their lives the same, the E.P.A. analysts decided to differentiate by age. After all, surveys in Britain and Canada had shown that people older than 70 were significantly less willing to pay for risk reduction than younger people were. Citing these results, the E.P.A. put a lower value on the lives of the older people.

Environmentalists, who are opposed to any calculation that lowers the value of cleaner air, seized on the ''senior death discount'' and orchestrated protests by the elderly. E.P.A. officials vowed to adhere to the every-life-is-equal estimate, and said the alternative estimate was done only at the behest of the Office of Management and Budget and its regulations chief, John D. Graham, the Harvard risk expert who has been subjecting federal agencies to rigorous cost-benefit analysis.

Dr. Graham, while insisting on the merit of both kinds of estimates, also rejected the $1.4 million elderly discount, but on narrower technical grounds. He said it was now out of date as a result of a new study showing that elderly Americans, unlike the elderly Britons and Canadians in earlier studies, are not significantly more tight-fisted than younger people when it comes to paying for safety.

But even if elderly Americans put a high value on their lives, does this mean that ethical policy makers should value their lives equally? Not necessarily, said the new study's co-author, Alan J. Krupnick, a fellow at Resources for the Future, a Washington research group.

''E.P.A. may want to reconsider the techniques they used to get the $1.4 million figure, but they shouldn't throw out the differential just because it upsets people,'' Dr. Krupnick said. ''This is a teachable moment to move further ahead the debate about how we value programs that save lives. If you ask people on the street whether they prefer a policy that saves the life of a young person or an elderly person, I think most people, including the elderly, would save the young person.''

But not if that person is a politician in Washington.

Drawing (Illustrations by Fred Rix)