People are using a wider variety of tobacco products. Cigarette smoking remains the most common by far, but use of e-cigarettes, hookah and other tobacco products is on the rise (Kasza et al., 2017). Regular use of hookah was 2% among US youth and adults in 2013 and 2014. Hookah use was highest among young adults, at 11%. Among past-30-day users of tobacco products, 38% of adults and 43% of youth had used multiple tobacco products. The most common multiple product use involved cigarettes and one other tobacco product.

We agree with Dr. Jawad that communication about harmful chemicals in cigarette smoke will need to be increasingly mindful of a new tobacco control environment in which multiple product use is fast becoming the norm. Our study focused on cigarettes because the literature was sufficiently large to support a systematic review (Morgan, Byron, Baig, Stepanov, & Brewer, 2017). Reviewing how people think about chemicals in other tobacco products was beyond our scope, and this new literature was too small to support a systematic review.

Understanding how people think about chemicals in other tobacco products is an important area for future research. Dr. Jawad’s hypothesis that saying hookah smoke has more of a given harmful chemical than cigarettes could make cigarettes seem safer intrigues us. This hypothesis merits empirical study. We agree on the importance of assessing unintended consequences of messages and campaigns about harms of tobacco product use. Expanding such research to include communication about marijuana may be sensible because combusted marijuana also contains dangerous chemicals (Moir et al., 2007). We hope behavioral science researchers will consider multiple product use as they explore how people think about harmful chemicals in tobacco products.