The prevalence of cigarette smoking among youth has dropped from 28 percent in 1991 to 11 percent in 2015, according to the Centers for Disease Control and Prevention (CDC). These findings were recently released in the Youth Risk Behavior Surveillance Report of 2015.

That was the good news. The bad news is that youth still use tobacco products — and the numbers are actually rising. The reason for the increase is that high school students are now using electronic cigarettes at a rate of 24 percent.

The Youth Risk Behavior Surveillance is a survey undertaken every two years at the national, state and local level throughout the United States. The survey monitors high priority health risk behaviors. More than 15,000 high school students took the survey in 2015 with 37 states participating and 19 large urban school districts.

The 2015 survey was the first time there were questions about e-cigarette use. The 2003 survey — taken the year before e-cigarettes emerged in the market — showed an overall smoking rate of 27.5 percent. The 2015 survey showed the rate of the use of tobacco products, which includes cigars, vapor devices, smokeless tobacco and conventional cigarettes, to be 31 percent.

So while the rate of using conventional nicotine cigarettes has decreased, the rate of using nicotine has not.

"Current cigarette smoking is at an all-time low, which is great news," CDC Director Tom Frieden said in a statement. "However, it's troubling to see that students are engaging in new risk behaviors, such as using e-cigarettes. We must continue to invest in programs that help reduce all forms of tobacco use, including e-cigarettes, among youth."

There are several factors that influence the use of e-cigarette products by high school students. A recent study of adolescents found e-cigarette use was strongly associated with a parent using smoking products and lack of participation in e-cigarette educational programs.

Research has also shown the rate of e-cigarette use among high school students is related to the extent of exposure to marketing and advertisements of e-cigarettes and tobacco products. The greater a student's exposure, the greater the rate of use.

The CDC reports that 69 percent of middle and high school students are exposed to e-cigarette advertisements. The exposure comes in many forms and can include retail stores, the internet, magazines, newspapers, television and the movies. They suggest efforts by states and communities must be made to reduce this exposure.

"Health risk behaviors among youth vary over time and across the nation, making the YRBS an important tool to better understand youth. The YRBS helps us identify newly emerging behaviors and monitor long-standing youth risk behaviors over time," said Laura Kann, Ph.D., chief of CDC's School-Based Surveillance Branch.

"While overall trends for the 2015 report are positive, the results highlight the continued need for improvements in reducing risks among teens."

Education is an important tool for prevention when it comes to e-cigarette use. Education messages that emphasize the serious health consequences may be more motivating to high school students than those that discuss the expenses related to using e-cigarettes.

Hearing the negative messages about the harm of e-cigarettes rather than the positive messages that students are exposed to through advertising will help to stop the trend of increased use of e-cigarettes among youth.