 While typically used fresh, it is also used dried, although the drying process removes much of the flavor and makes the leaf too brittle to be used as a wrapper.The essential oils within the leaf are rich in safrole, a substance also found in sassafras, which has been shown to be carcinogenic in animals.In 1960, the U.S. Food and Drug Administration banned sassafras bark along with sassafras oil and safrole as flavoring agents because of their carcinogenic properties and the Council of Europe imposed the same ban in 1974, with the EPA classifying the compound as a group B2 probable human carcinogen.