⼆⼿煙會導致許多致命的疾病，例如⼼臟病和癌症。正如吸煙的煙霧，⼆⼿煙霧同樣包含超過7000種化學品（如氰化物（即山埃）、砷），而其中⾄少有69 種是致癌物（例如亞硝胺、醛、鉻）。
接觸⼆⼿煙霧的即時影響包括：眼睛不適、咽喉痛、咳嗽。長期接觸⼆⼿煙霧可導致癌症、⼼⾎管疾病、呼吸系統疾病和妊娠併發症等。
三⼿煙是指捲煙熄滅後附在衣服、牆壁、家具、頭髮和⽪膚上的煙霧化學殘留物。
三⼿煙中含有⼤量有毒物質包括用於化學武器用途的山埃、打火機油中的丁烷、油漆稀釋劑中甲苯，此外還有砷、鉛、一氧化碳、甚至是高放射性物質釙-210。這些有毒化學物質會在吸煙後數天甚⾄幾週後仍殘留在室內的家⽤器皿、傢俬、地毯、地板、牆壁、天花板等的表⾯上。充滿好奇心的幼兒喜歡在地上爬行，到處觸碰和將物件放進口中，是特別高危的一群。市面上⼤多數鹼性清潔劑無法去除這些物質，因此完全不吸煙是保護家人的最好⽅法。
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