pollution.　Therefore,　it　is　necessary　to　calculate　the　＂emission　rate＂　to　normalize　the　concentration　of　pollutants　emitted　under　various　experimental　conditions　and　make　the　results　comparable.　This　review　aims　to　increase　the　awareness　regarding　the　harmful　effects　of　the　second-hand　exposure　to　aerosols　coming　from　the　use　of　cigarettes　and　e　-cigarettes,　identify　knowledge　gaps,　and　provide　a　scientific　basis　for　future　policy　interventions　with　regard　to　the　regulation　of　smoking　and　vaping.