Of special concern to Verall are the hormones melegestrol acetate, progesterone, testosterone, trenbolone and zeranol. These hormones are known to disrupt the body's natural balance, causing a number of biological effects. "There is clear evidence of the risk to human health posed by these hormones," Verall said, citing research that showed oestradiol is considered to be a cancer risk. Studies show that 97 of every 100,000 U.S. women have breast cancer, whereas only 67 of every 100,000 European women are afflicted.

Verall added that according to recent studies, children are particularly sensitive to these hormones, which can cause "sudden growth or breast development, even at levels which are difficult to detect in the laboratory."

Currently, the European Union prohibits the use of growth or sex hormones to speed the maturity of cattle and fatten them up, but there are doubts as to whether the ban has been enforced, because there is no testing for hormone residue in beef imported to the EU. The U.S. government has attempted to have the ban lifted, a move supported by Prime Minister Tony Blair and his administration.

Mainstream supermarkets, eyeing the success of organic retailers such as Whole Foods, have rushed to meet demand. The Kroger Co., Safeway Inc. and SuperValu Inc., which owns Albertson's LLC, are among those selling their own organic brands. Wal-Mart Stores Inc. said earlier this year it would double its organic offerings.

The number of organic farms - an estimated 10,000 - is also increasing, but not fast enough. As a result, organic manufacturers are looking for ingredients outside the United States in places like Europe, Bolivia, Venezuela and South Africa.

That is no surprise, said Barbara Robinson, head of the Agriculture Department's National Organic Program. The program provides the round, green "USDA Organic" seal for certified products.

Her agency is just now starting to track organic data, but Robinson believes the United States is importing far more organic food than it exports. That's true of conventional food, too.

"That is how you stimulate growth, is imports generally," she said. "Your own industry says we're tired of importing this; why should I pay for imports when I could start producing myself?"

"We're doing a lot of scrambling," said Sheryl O'Loughlin, CEO of Clif Bar Inc. "We have gotten to the point now where we know we can get a call for any ingredient."

The makers of the high-energy, eat-and-run Clif Bar needed 85,000 pounds of almonds, and they had to be organic. But the nation's organic almond crop was spoken for. Eventually, Clif Bar found the almonds - in Spain. But more shortages have popped up: apricots and blueberries, cashews and hazelnuts, brown rice syrup and oats.

Even Stonyfield Farm, an organic pioneer in the United States, is pursuing a foreign supplier; Stonyfield is working on a deal to import milk powder from New Zealand.

"I'm not suggesting we would be importing from all these places," said Gary Hirshberg, president and CEO of Stonyfield Farm Inc. "But for transition purposes, to help organic supply to keep up with the nation's growing hunger, these countries have to be considered."

The dilemma of how to fill the gap between organic supply and demand is part of a long-running debate within America's booming organic industry. For many enthusiasts, organic is about more than the food on their plates; it's a way to improve the environment where they live and help keep small-scale farmers in business.

"If organic is something created in the image of sustainable agriculture, we certainly haven't accomplished that yet," said Urvashi Rangan, a scientist for Consumers Union. "What people do have to understand is if that stuff comes in from overseas, and it's got an organic label on it, it had to meet USDA standards in order to get here."

The issue causes mixed feelings for Travis Forgues, an organic dairy farmer in Vermont.

"I don't like the idea of it coming in from out of this country, but I don't want them to stop growing organic because of that," Forgues said. "I want people to say, 'Let's do that here, give a farmer another avenue to make a livable wage.'"

A member of the farmer-owned Organic Valley cooperative, Forgues got his dairy farm certified nearly 10 years ago. Organic Valley supplies milk to Stonyfield.

Switching to organic is a difficult proposition. Vegetable grower Scott Woodard is learning through trial and error on his Putnam Valley, N.Y., farm. One costly mistake: Conventional farmers can plant seeds when they want and use pesticides to kill hungry insect larvae. If Woodard had waited three weeks to plant, the bugs that ate his seeds would have hatched and left. Organic seeds can be double the price of conventional.

"There's not a lot of information out there," Woodard said. "We try to do the best we can. Sometimes it's too late, but then we learn for next time."

Stonyfield and Organic Valley are working to increase the number of organic farms, paying farmers to help them switch or boost production. Stonyfield, together with farmer-owned cooperative Organic Valley, expects to spend around $2 million on incentives and technical help in 2006, Hirshberg said.

Other companies offer similar help. And the industry's Organic Trade Association is trying to become more of a resource for individual farmers.

Caren Wilcox, the group's executive director, described how an Illinois farmer showed up in May at an industry show in Chicago.

"He said, 'I want to get certified. Help me,'" Wilcox said. "It was a smart thing to do, but the fact that he had to get into his car and go down to McCormick Center says something about the availability of information."

In the meantime, manufacturers like Clif Bar and Stonyfield still prefer to buy organic ingredients, wherever they come from, instead of conventional crops in the U.S.

"Anybody who's helping to take toxins out of the biosphere and use less poisonous chemicals in agriculture is a hero of mine," Hirshberg said. "There's enormous opportunity here for everybody to win, large and small."

Bush has vowed to veto the popular measure, which passed the House by a wide margin last year. If he does, it would be his first veto of legislation from the Republican-led Congress in his five and a half years in office.

Many lawmakers opposed to the research were hoping to avoid that scenario, in part by presenting alternatives that could allow stem-cell research to proceed without destroying human embryos to collect them. Along with the House bill, the Senate will vote on a measure sponsored by Sen. Rick Santorum, R-Pa., that seeks to fund embryo-sparing embryonic-stem-cell research.

But groups both for and against expanding research using existing technology -- the kind requiring destruction of embryos -- say that the alternative is unlikely to attract enough lawmakers to defeat the House bill, known as H.R. 810.

"We are confident that we have the votes to pass 810, and that is the important thing," said Sean Tipton, president of the Coalition for the Advancement of Medical Research, an umbrella group of dozens of organizations backing the repeal.

Conservative opponents of the research say they're counting on Bush to follow through on his threat to veto the measure, even though it remains popular with voters who will soon be casting ballots in mid-term elections.

Douglas Johnson, chief lobbyist for the National Right-to-Life Committee, an anti-abortion group opposing embryonic-stem-cell research, pointed to statements from Sen. Arlen Specter, R-Pa., saying that his bill repealing Bush's policy has the 60 votes it will need to clear the Senate.

"It may well prove to be the case that Specter's correct," he said. "If he is, it'll go to the president. The president has made it very clear he will veto."

Some anti-abortion lawmakers have said they favor repealing the White House stem-cell policy. Most notable among them is Sen. Orrin Hatch, R-Utah, a staunchly anti-abortion lawmaker who strongly favors research on embryos left over from fertilization clinics and slated for destruction.

Wendy Wright, president of Concerned Women for America, a conservative group, said that her group would take lawmakers to task on H.R. 810 and another scheduled bill banning what opponents have dubbed "fetal farming," the so-far theoretical process of creating human embryos or fetuses for the purposes of medical research.

"It will be something in our voter guide, making people aware of how senators voted on it," she said.

Santorum, currently trailing in polls against a Democratic challenger, is the main sponsor of both the alternative embryonic-stem-cell bill and the "fetal farming" measure.

CAMR's Tipton said his group would not oppose the bills but called them a "fig leaf" attempting to give vulnerable lawmakers a way to support stem-cell research without enraging conservatives by supporting backing a repeal of the Bush policy.

"I think it's clear the American public supports stem-cell research, and that creates a political dilemma for a couple people," he said.

"What we're going to do is expose anyone who tried to not support H.R. 810 and still argue that they're pro-patient, pro-research," he said.

He said that while part of the increase may be attributed to natural fluctuations, evidence also links it to the effects of human-induced climate warming.

Scientists have become increasingly concerned in recent years about the amount of carbon dioxide released into the atmosphere by the burning of fossil fuels. Average worldwide temperatures have risen this century as a result of what many believe is a greenhouse effect from that pollution.

The researchers used the files of the U.S. Forest Service and National Park Service to analyze 1,166 fires of more than about 1,000 acres. Their findings are published Thursday in the online edition of the journal Science.

Beginning about 1987, there was a change from infrequent fires averaging about one week in duration to more frequent ones that often burned five weeks or more, they reported. The length of the wildfire season was extended by 78 days.

The researchers said the changes appear to be linked to annual spring and summer temperatures, with many more wildfires burning in hotter years than in cooler years.

They also found a connection between early arrivals of the spring snowmelt in the mountainous regions and the incidence of large forest fires. An earlier snowmelt, they said, can lead to an earlier and longer dry season, which provides greater opportunities for large fires.

"I see this as one of the first big indicators of climate change impacts in the continental United States," said research team member Thomas Swetnam, director of the Laboratory of Tree-Ring Research at the University of Arizona in Tucson. "We're showing warming and earlier springs tying in with large forest fire frequencies. Lots of people think climate change and the ecological responses are 50 to 100 years away. But it's not 50 to 100 years away - it's happening now in forest ecosystems through fire."

The research was supported by the National Oceanic and Atmospheric Administration, the Forest Service and the California Energy Commission.