By PAUL KRUGMAN

Last week a quietly scathing report by the inspector general of the Environmental Protection Agency confirmed what some have long suspected: in the aftermath of the World Trade Center's collapse, the agency systematically misled New Yorkers about the risks the resulting air pollution posed to their health. And it did so under pressure from the White House.

The Bush administration has misled the public on many issues, from the budget outlook to the Iraqi threat. But this particular deception seems, at first sight, not just callous but gratuitous. It's only when you look back at budget politics in 2001 that you see the method in the administration's mendacity.

A draft E.P.A. report released last December conceded that 9/11 had led to huge emissions of pollutants. In particular, releases of dioxins — which are carcinogens and can also damage the nervous system and cause birth defects — created "likely the highest ambient concentrations that have ever been reported," up to 1,500 times normal levels. But the report concluded that because the outdoor air cleared after a couple of months, little harm had been done.

In fact, the main danger comes from toxic dust that seeped into buildings and remains in carpets, furniture and air ducts. According to a recent report in Salon, businesses that did environmental assessments of their own premises found alarming levels not just of dioxins but also of asbestos and other dangerous pollutants. So the most shocking revelation from the new report is that under White House direction, the E.P.A. suppressed warnings about indoor pollution. Scattered evidence suggests that as a result, hundreds of cleaning workers and thousands of residents may be suffering chronic health problems.

Why was crucial information withheld from the public? The report mentions "the desire to reopen Wall Street and national security concerns." Maybe — though the national security benefits of failing to remove toxic dust escape me. I suspect that there was another reason: budget politics.