Health impacts of passive exposure to alternative tobacco products: a systematic review.

[OBJECTIVES] Electronic nicotine delivery systems (ENDS), waterpipe (hookah), heated tobacco products (HTPs), and bidis are increasingly used worldwide and are known to harm users. However, the health risks of passive (secondhand) exposure to these products remain poorly understood. We aimed to systematically review existing evidence on the health impacts of passive exposure to ENDS, waterpipe, HTPs, and bidis.

[DATA SOURCES] We systematically searched CINAHL, Web of Science, Scopus, PubMed, Cochrane, and Embase (from inception to December 2024) for original human studies reporting clinical or biological effects of passive exposure to these products.

[STUDY SELECTION] Eligible designs included RCTs, cohort, case-control, cross-sectional, and experimental studies.

[DATA EXTRACTION] Two reviewers independently assessed risk of bias using an adapted Newcastle-Ottawa Scale, with study quality rated as good, fair, or poor.

[DATA SYNTHESIS] Of 8810 articles identified, 20 met inclusion criteria (10 cross-sectional, 2 case-control, 7 experimental, 1 cohort). Most studies evaluated passive ENDS (n = 12; 5 good, 3 fair, 4 poor), showing associations with asthma, bronchitis, ear, nose and throat symptoms, mental health problems, and increased inflammatory markers. Waterpipe exposure (n = 6; 3 good, 2 fair, 1 poor) was linked to toxicant biomarkers and increased risk of COPD and childhood cancer. Only one study each (both poor quality) examined passive exposure to bidis (lung cancer) and HTPs (volatile organic compounds).

[CONCLUSIONS] Heterogeneity and study limitations precluded meta-analysis, but available evidence suggests that passive exposure to ENDS, waterpipe, HTPs, and bidis is hazardous. These risks warrant further study and consideration in evidence-based public health decision-making.