It’s probably safe to say that as teens we all knew someone who smoked cigarettes, someone who swore they never would, and someone who said they only did it here and there. Just like hookah, smoking cigarettes here and there may seem harmless, but it’s not. Yet many teens believe it is, according to a new study.

“All smoking counts,” said lead author Stephen Amrock, a student of pediatric medicine at New York University School of Medicine, according to HealthDay. “Social smoking has a price, and even the occasional cigarette truly is bad for you. Light and intermittent smokers face tremendous future health risks.”

Cigarettes contain over 7,000 chemicals, with 69 of them known to cause cancer, according to the American Lung Association. Every time a teen drags a cigarette, they’re exposing all the organs in their body to those chemicals — even if it’s their first cigarette in two or three days. Results from the study on 24,658 teens, however, showed that almost a quarter of them felt intermittent smoking caused no harm. Specifically, 35 percent of light smokers (a few cigarettes a day) and 14 percent of intermittent smokers (smoking in intervals; stopping for a few days) said their own levels of tobacco use weren’t harmful, the NY Daily News reported.

That’s not to say these teens were oblivious to the harms of smoking. Roughly 90 percent of them said heavy smoking — defined as 10 cigarettes per day — was very harmful. But as frequency of use dropped, so did teens’ perceptions of the harm; 64 percent said light smoking was very harmful while only 33 percent said intermittent smoking was very harmful.

“Our findings suggest that public health efforts have been working, but that those efforts have likely been incomplete,” Amrock said. “Decades of anti-tobacco work have succeeded in convincing adolescents that heavy smoking patterns are dangerous, but the complete message has not been broadly received.”

The good news is that it could be easier for light and intermittent smokers to quit, Amrock said — these people are likely not yet addicted to nicotine. Helping them quit could be as easy as educating them on the dangers they’re making themselves available to. Getting this done early is crucial to lowering smoking rates, which currently stand at an estimated 46.6 million adults, because 68 percent of smokers began smoking regularly at age 18 or younger.

“Preventing tobacco use is among the most cost-effective things we can do as a health care system,” Amrock said. “Making sure that all teens understand just how dangerous all tobacco is, [is] an important first step in curbing tobacco use nationwide.”

Source: Amrock S, Weitzman M. Adolescents’ Perceptions of Light and Intermittent Smoking in the United States. Pediatrics. 2015.