二手烟已经被确认对其他人有危害。
He conducted a rigorous experiment on the effect of second hand smoking.他针对吸二手烟的影响进行了一次严谨的实验。
I feel car exhaust, and smoke coming from stir frying vegetables are even more harmful than second hand smoking.我觉得汽车的尾气﹑炒菜的油烟对健康的危害可能比被动吸烟更厉害。