BioEd Online

George Bush's presidency has suffered a rash of accusations that he is either ignoring or manipulating science. Democratic rival John Kerry, meanwhile, pledges to follow impartial scientific advice - but observers say that they are yet to be persuaded.

The idea that Bush discounts scientific opinion dogged his first few years in office, but the evidence was largely anecdotal. Then in June 2003, a front-page article in The New York Times detailed attempts by White House officials to play down the human causes of climate change by doctoring a report from the Environmental Protection Agency. Eventually, the whole section was removed from the report by the agency's researchers, who were unhappy with the rewrite.

The article was followed by several comprehensive reports accusing the White House of meddling in science. One, released by the Union of Concerned Scientists (UCS) in February 2004 and which gained a lot of publicity, documented dozens of examples in which scientific findings seemed to have been suppressed or changed to suit political ideology.

The UCS accused White House officials of stacking advisory panels with members who shared their political views, altering websites, and editing or quashing scientific reports on a range of issues. In one example, the UCS say that administration officials asked the Centers for Disease Control and Prevention to remove a website that discussed safe sex rather than abstinence. "The administration has continued to undermine the integrity of science in policy-making seemingly unchecked," the UCS said in a follow-up report later in the year.

Bush's science adviser, John Marburger, fired back in April. In an official rebuttal, he called the UCS report "wrong and misleading". He also defended the administration's scientific integrity, and said that policy decisions must take into account many factors besides scientific fact, and so may not always meet scientists' expectations.

Kerry has made the most of the controversy. In a position paper released in June, he called the Bush White House "one of the most anti-science administrations in our nation's history". By contrast, he pledged to "embrace empirical science based on facts, not ideology".

The two camps have different attitudes towards the value of science, says Michael Oppenheimer who studies science policy at Princeton University, New Jersey, and has advised Kerry on global warming. "The current administration seems unwilling to let the experts and the agencies present an independent judgment," he says. "I feel fairly confident that Kerry wouldn't try to torque the science."

But some sceptics remain to be convinced that the Democratic candidate will make a clear distinction between science and policy. "The temptation to inject politics into science is always there," says UCS spokeswoman Lexi Shultz based in Washington DC. "This administration has succumbed, and it's possible the next one will too."