Erin O'Neal has two daughters and a fridge stocked with organic cheese, milk, fruits and vegetables in her Annapolis, Md., home. She is among the increasing number of parents who buy organic to keep their children's diets free of food grown with pesticides, hormones, antibiotics or genetic engineering.

"The pesticide issue just scares me — it wigs me out to think about the amount of chemicals that might be going into my kid," said O'Neal, 36.

Since last year, sales of organic baby food have jumped nearly 18 percent, double the overall growth of organic food sales, according to the marketing information company ACNielsen.

As demand has risen, organic food for children has popped up at more than just natural food stores.

For example, Earth's Best baby food, a mainstay in Whole Foods and Wild Oats markets, just reached a national distribution deal with Toys R Us and Babies R Us. Gerber is selling organic baby food under its Tender Harvest label. Stonyfield Farm's YoBaby yogurt can be found in supermarkets everywhere.

The concern about children is that they are more vulnerable to toxins in their diets, said Alan Greene, a pediatrician in northern California. As children grow rapidly, their brains and organs are forming and they eat more for their size than do grown-ups, Greene said.

"Pound for pound, they get higher concentrations of pesticides than adults do," said Greene, who promotes organic food in his books and on his Web site, http://www.drgreene.com

New government-funded research adds to the concern. A study of children whose diets were changed from regular to organic found their pesticide levels plunged almost immediately. The amount of pesticide detected in the children remained imperceptible until their diets were switched back to conventional food.

"We didn't expect that to drop in such dramatic fashion," said Emory University's Chensheng Lu, who led the Environmental Protection Agency-funded research. Lu's findings will be published in February in the journal Environmental Health Perspectives.

Scientists are still trying to figure out how pesticides affect children, Lu said, but he notes that it took years to prove the health hazards of lead.

Still, the uncertainty is leading parents, especially new or expecting mothers, to switch to organic food. Many are even making their own baby food from organic ingredients.

"Maybe that has the reputation of being difficult, but it doesn't have to be, and once you get into the habit of doing something regularly, it gets to be easier," said Jody Villecco, a nutritionist for Whole Foods.

In a traveling lecture series for Whole Foods and Mothering magazine, Villecco demonstrates by shaving a peeled banana with a knife to make mush — "There, we just made baby food," she said. She recommends people make baby food in big batches and freeze it in ice cube trays.

Eating organic is definitely not cheap. But Green and Lu said parents have options if they can't afford the food or don't want to search for it or make it: Buy fruits and vegetables known to have lower pesticide residues.

The Environmental Working Group, a Washington-based advocacy group, has produced a guide to the pesticide levels in fruits and vegetables commonly sold in grocery stores, basing the findings on data from the Agriculture Department and Food and Drug Administration.

The guide says the lowest pesticide levels are found in asparagus, avocados, bananas, broccoli, cauliflower, sweet corn, kiwi, mangos, onions, papaya, pineapples and sweet peas.

The highest pesticide levels, meanwhile, are found in apples, bell peppers, celery, cherries, imported grapes, nectarines, peaches, pears, potatoes, red raspberries, spinach and strawberries.

The rating system is unnecessary, according to industry representatives who say conventional food is safe and affordable.

"There are some people in the organic food industry and the environmental industry who have unfortunately scared parents into thinking you have to turn to organic sources for baby food, based on claims that have no basis in science or fact," said Jay Vroom, spokesman for CropLife America, an industry group. "The products my industry produces are safe" for everyone.

Beyond baby food, dairy and produce, snacks are also a rapidly growing segment of organic food, according to the Organic Trade Association, an industry group.

Snacks are a priority for Susan Guegan, 44, a mother of four boys in Boulder, Colorado. Guegan made their food from scratch when they were babies. Now she buys organic versions of the cookies and hot dogs they ask for.

"They love Oreos," she said. "They'll say, `Can we get this?' I'm like, `Can you read me the ingredients?' They'll laugh and try to say some of them. I'll say, `You can put that back.'"