Teenagers and young adults in the US are increasingly being diagnosed with skin cancer, according to doctors who warn that the development could lead to an outbreak of deadly aches on the skin as these patients get older. Doctors are especially disturbed by the numbers of younger people they are treating, which suggests that messages about avoiding the sun still aren't getting through and that the tanned skin(晒黑的皮肤) that was made popular by French designer Coco Chanel in the 1920s remains a sought-after look today. Although doctors lack the data to know what exactly is behind the rise in skin cancers among young people, they suggest several factors: more time in the sun, improper use of sunscreens and a rise in tanning salon(阳光浴沙龙) visits. Skin doctors believe that young people are generally spending more time in the sun than their parents did and are either not using enough sunscreen or failing to apply it properly. They also claimed that many Americans, including the young, are spending more vacation hours in sunny climates than in previous decades. In a study published in 1997 in the American Academy of Dermatology, a research team led by Dr June Robinson at Northwestern University Medical School found that during the decade ending in 1996, the number of Americans who reported at least one severe sunburn rose from 30 percent to 39 percent. Doctors feel really worried that ______.