An August 2019 study by the University of California Irvine found that,

“Hookah [Shisha] mainstream smoke - that which is directly inhaled by the user - has many toxic and harmful chemicals, such as nicotine, which can lead to tobacco addiction; irritating carbonyl compounds; and benzine, a known carcinogen … And due to the greater volume inhaled for every puff and the longer duration of a smoking session, the hookah oftentimes delivers a higher dose of those chemicals to the smoker."