Surgeon General C. Everett Koop has joined other federal health officials in trying to assure the public it is safe for children to eat apples.

"I wish to send a message to mothers across the country: `It's OK Mom, apples are good for your kids!' " Koop said in a statement.Last week, officials of the Food and Drug Administration, the Environmental Protection Agency and the Agriculture Department went to Capitol Hill in an effort to calm public fears over the chemical Alar, used by some apple growers to retain the crispness of their fruit.

Many apple growers say they don't use Alar, which has been linked to cancer in animal tests. But the industry is reeling from reaction to a recent private environmental group's report that youngsters are at especially high risk from Alar because they eat more apples than adults.

Trying to allay their fears, Koop said that "in 1988, only 5 percent of the apple crop was treated with Alar. As surgeon general, I support my colleagues in the government and scientific community in the belief that it is safe to eat apples."

FDA Commissioner Frank Young has said that, even in those apples containing Alar, the level is no more than 10 percent the level found acceptable under EPA regulations.