Juul executives have said that its nicotine salt gives users an experience similar to conventional cigarettes, which the company says helps smokers quit. But the CDC worries about the effects of nicotine salts on the developing brain in young people.

"Juul products use nicotine salts, which can lead to much more available nicotine," CDC Principal Deputy Director Dr. Anne Schuchat told the House Oversight and Reform Committee's panel on consumer products. She said doctors believe the salts allow nicotine to "cross the blood brain barrier and lead to potentially more effect on the developing brain in adolescents."

WASHINGTON, D.C. — A top U.S. health official told lawmakers Tuesday that e-cigarette market leader Juul uses salts in its vaping devices that she said could be particularly dangerous for teenagers.

Those effects include difficulty with memory, learning and attention, she said. Nicotine addiction can also prime the body to become addicted to other substances, which is "of particular concern," she said at an emergency hearing looking at a recent outbreak of a deadly vaping illness that has caused more than 530 people to fall ill, killing at least nine in the U.S.

"The devices are very easy to conceal, between the high levels of nicotine and discreet use, we think that the use among teens is particularly concerning," she said.

She added that the CDC is particularly worried about flavored e-cigarettes, "and the role that they play in hooking young people to a life of nicotine, and we really want to avoid another generation being addicted to nicotine so addressing flavors directly is a good idea."

She recommended that U.S. consumers avoid all vaping products as U.S. health officials struggle to identify the cause of a deadly vaping illness that's killed nine people and made hundreds more ill in recent months, she said.

"At this point I think caution in all products is recommended. It may not even be the THC or the nicotine. It may be the additives or substances that may be common. It may be the material is not labeled appropriately. I do think consumers need to be quite cautious right now," Schuchat said.