Harmful Chemicals in Tobacco Products

Tobacco smoke Cigarettes, cigars, and pipe tobacco are made from dried tobacco leaves. Other substances are added for flavor and to make smoking more pleasant. The smoke from these products is a complex mixture of chemicals produced by burning tobacco and its additives. Tobacco smoke is made up of thousands of chemicals, including at least 70 known to cause cancer. These cancer-causing chemicals are referred to as carcinogens. Some of the chemicals found in tobacco smoke include:

Nicotine (the addictive drug that produces the effect people are looking for and one of the harshest chemicals in tobacco smoke)
Hydrogen cyanide Formaldehyde
Lead
Arsenic
Ammonia
Radioactive elements, such as uranium (see below)
Benzene
Carbon monoxide
Nitrosamines
Polycyclic aromatic hydrocarbons (PAHs)

Many of these substances cause cancer. Some can cause heart disease, lung disease, or other serious health problems, too. Most of the substances come from the burning tobacco leaves themselves, not from additives included in cigarettes (or other tobacco products). 

Radioactive materials in tobacco smoke 

Radioactive materials are in the tobacco leaves used to make cigarettes and cigars. These materials come from the fertilizer and soil used to grow the tobacco leaves, so the amount in tobacco depends on the soil the plants were grown in and the type of fertilizers used. These radioactive materials are given off in the smoke when tobacco is burned, which smokers take into their lungs as they inhale. This may be another key factor in smokers getting lung cancer.

Is cigar smoke different? 

Cigar smoke pretty much has the same toxic and carcinogenic compounds as cigarette smoke, but some of them are present at different levels. Because of the aging process used to make cigars, cigar tobacco has high concentrations of some nitrogen compounds (nitrates and nitrites). When the fermented cigar tobacco is smoked, these compounds give off several tobacco-specific nitrosamines (TSNAs), some of the most potent cancer-causing substances known. Also, because the cigar wrapper is less porous than a cigarette wrapper, the tobacco doesn’t burn as completely. This results in higher concentrations of nitrogen oxides, ammonia, carbon monoxide, and tar – all very harmful substances. Smokeless tobacco products 

Smokeless tobacco products include snuff and chewing tobacco that is put into the mouth or nose but is not burned like cigarettes or cigars. Still, smokeless products in the United States contain a variety of potentially harmful chemicals, including high levels of TSNAs. There are also other cancer-causing agents in smokeless tobacco, such as benzo[a]pyrene and other polycyclic aromatic hydrocarbons (PAHs). These carcinogens are absorbed through the mouth and may be why several types of cancer are linked to the use of smokeless tobacco. Like other forms of tobacco, smokeless tobacco also contains radioactive substances. Snus (pronounced ‘snoose’) is a type of moist snuff that does not require spitting. It was first used in Sweden and Norway, but it is now available in the United States as well. Snus generally has lower levels of nicotine and TSNAs than traditional moist snuff brands, but can still be addictive and has been linked to some types of cancer.

Which is riskier? Smokeless tobacco or cigarette smoking? 

Smokeless tobacco products are less deadly than cigarettes. On average, they kill fewer people than cigarettes. Smokeless products are often promoted as a less harmful alternative to smoking, but they are still linked with cancer and can still be deadly. And they have not been proven to help smokers quit.

E-cigarettes and similar devices 

E-cigarettes and other electronic nicotine delivery systems (ENDS) are often used as substitutes for cigarettes or other tobacco products. Marketers of e-cigarettes and other ENDS often claim the ingredients are safe. But the aerosols these products produce can contain addictive nicotine, flavorings, and a variety of other chemicals, some known to be toxic or to cause cancer. The levels of many of these substances appear to be lower than in traditional cigarettes, but the amounts of nicotine and other substances in these products can vary widely because they are not standardized. The long-term health effects of these devices are not known, but they are being studied.

Source: American Cancer Society 

https://www.cancer.org/cancer/cancer-causes/tobacco-and-cancer/carcinogens-found-in-tobacco-products.html#references

拒      菸

一支燃點著的香煙會釋放出四千多種有害的化學物質，當中以尼古丁、焦油及一氧化碳對身體的影響最大，被稱為香煙三大殺手：

尼 古 丁
	尼古丁是一種烈性的興奮劑，可以刺激中樞神經，令人上癮。
	每支香煙含1 - 1.5毫克的尼古丁，其中有24%由吸煙者在吸煙時直接吸入 (同時吸入60-70毫克的尼古丁會致命)。
	尼古丁對腦部的影響： 當吸入香煙時，尼古丁便會直接湧入肺部。之後便由帶氧的血液經過心臟再轉送到腦部。 在短於十秒的時間內，一股濃縮劑量的尼古丁便傳送到腦部的血管，並產生一種尼古丁效應。
	尼古丁令吸煙者上癮： 經過一段時間後，吸煙者的腦細胞為了適應腦內化學物質的不平衡而要增加 尼古丁的受體，其後，吸煙者的身體已適應定時吸入的尼古丁而對它產生依賴，因而產生了煙癮。
	尼古丁對身體造成的損害： 長期吸入尼古丁會導致腦細胞痲痺，引致失憶、工作能力減低、甚至中風。 同時會令腎上腺素分泌增多，血壓上升、心跳加速 (每支香煙平均會使脈搏加快15-20下)。 另一方面，尼古丁會使血小板黏性提高，加速血液凝固，因而容易造成血凝塊阻塞血管，引起心肌梗塞。
焦 油
	這種啡黃色的黏性物質，當中包含不少致癌物質如硫化氫、二氧化硫、一氧化碳等。
	焦油對身體的損害： 阻塞及刺激氣管及肺部，引起咳嗽。 玷污肺部組織，令其失去彈性，直接影響肺部功能。 當中的多種致癌物質，可導致口腔癌、喉癌、肺癌等。 令吸煙者之手指及牙齒變黃。
一 氧 化 碳
	這種無色無味的有毒氣體，大量生產於汽車廢氣和碳火之中。
	一氧化碳令身體出現缺氧現象： 在身體內，一氧化碳與血紅素的結合力是氧氣的二百倍。所以當一氧化碳進入人體後， 會優先和血紅素結合，血液中的一氧化碳血紅素濃度增加，血液攜氧能力將相對減少， 因而形成缺氧現象。
	一氧化碳對身體的影響： 一般正常人血液中的一氧化碳含量在1%以下，而吸煙者卻可高達15%。 長遠而言，正常血液循環會因而受阻，思維跟判斷力都受到影響，更導致脂肪積聚， 增加患上心臟病和中風的機會。

 吸煙所引起的疾病

腦中風

吸煙會減低腦部循環之氧氣及血液，引致腦部出現血管出血及閉塞，因而導致痳痺、智力衰退及中風。

冠心病

吸煙會引致冠狀動脈心臟病 (冠心病)，25%的冠心病總死亡率是由吸煙所引致的。

肺癌

90%的肺癌總死亡率是由吸煙所引致。而每天吸十支煙，患肺癌比率是不吸煙人士的十倍。

肺氣腫

吸煙會令肺部支氣管內積聚有害的物質，阻礙人體呼吸系統之正常運作，肺部細胞因而膨脹甚至爆裂，導致患者呼吸困難。75%的肺氣腫死亡率是由吸煙引致的。

減低生殖能力

吸煙亦減低男性的生殖能力，引發愛滋病病徵；增加女性患乳癌的機會達80%，同時亦增加了流產的機會。

血管梗塞

吸煙會令血管收縮，減慢血液及氧份循環，最終引致血管出現硬塊。

吸煙對各組別人士的影響

嬰兒 吸煙的母親 女性吸煙者有29%機會流產，較非吸煙人士高出十倍。 吸煙會減低輸送給胎兒之血液與氧份，胎兒的呼吸活動將減慢三分之一。 產時危險 早產--較大機會產前流血，過早或過遲出生。 氧份輸送不足阻礙胎兒正常生長，嬰兒出生時較一般嬰兒體重輕200克，矮1.3公分，並且頭部呎吋較小。 嬰兒成長 體能發展 呼吸糸統疾病(氣管炎及肺炎)患病率高出2倍。 嬰兒的出牙期較遲。 視力問題之患病率高出2倍。 智力發展 閱讀與算術之學習進度慢3至5月。 懷孕期間長期吸入二手煙對嬰兒的病患風險﹕ 嬰兒猝死--高出2.1倍 哮喘(1歲前)--高出2.8倍 入院--高出1.12倍 輕磅--高出1.4倍 中耳炎--高出1.5倍

吸煙對青少年的健康影響 吸煙會刺激哮喘病發及提高感染呼吸系統疾病之機會(例如 : 提高咳嗽機會率達5倍)。 吸煙減低身體的抵抗能力。 吸煙者更容易感到疲倦、勞累、喘氣及腳部酸痛 (每天吸一支煙能使普通人競跑16公里 的速度減慢40秒)。

青少年吸煙對其行為發展的影響 成年人吸煙的習慣早於15、16歲時巳開始。 青少年期間開始吸煙會促成及提高他們對煙草的依賴。 80%有吸煙習慣的青少年，在成長後將會繼續吸煙。 吸食煙草是導致其後濫用藥物之重要導因。青少年吸煙者成為酗酒者的機會較 非吸煙者高出10倍。長期煙民嘗試毒品的機會較非吸煙者高出25倍。

男性與吸煙	女性與吸煙
吸煙直接減弱男性製造正常精子數量的能力，吸煙者精子數量平均較非吸煙者少22%。 吸煙者的精子畸型率(沒有平常活動力)較非吸煙者高出1.2倍。 吸煙者之精子較難與卵子結合(成孕之因素)，每天吸食一包煙能減低受孕機會一半。 吸煙減低荷爾蒙分泌，因而減慢生殖器官之反應(導致性無能的重要原因)。 吸煙令生殖器官之血管收宿，出現性無能的機會比非吸煙者高出50%。 吸煙能減低身體之抵抗能力，而感染愛滋病的發病速度是非吸煙者的1.7倍。	女吸煙者同時使用口服避孕丸與非吸煙者比較，將提高冠心病、中風及其他心血管病症之患病率10倍。 女性20%冠心病死亡個案由吸煙導致。 1993至1994年，在香港女性癌病致命個案中，肺癌病之成因比乳癌高出3倍。 每天抽十支煙以上將提高盤骨炎患病率一倍。每天吸一包煙，將提高關節炎患病率50% 吸煙減低女性苛爾蒙之平衡。使女性較難懷孕及需更長時間，成功機會率亦比非吸煙者低四份一。 吸煙人士的更年期平均提早2至3年。 四十歲前斷經患病率將提高四倍。 五份一的子宮癌病例由吸煙引致，而吸煙者之患病率是非吸煙者的兩倍。

關於二手煙

什麼是二手煙？

「環境煙草煙霧」(Environmental Tobacco Smoke, ETS)，或「二手煙」 (Second-hand Smoke)，是來自香煙、煙斗或雪茄燃燒時所產生、以及吸煙 者在吸煙時呼出的一種混合煙霧。 吸煙者吸啜香煙時吸入肺部後再呼出的煙氣，稱為「主流煙」，主流煙只 佔所有香煙煙霧的15% ; 而煙草燃燒時直接釋放出的煙氣，約佔85%，稱 為「支流煙」。 二手煙主要來自「支流煙」，即燃點香煙時隨著煙霧釋放出來的物質。而 「支流煙」的成份亦包括吸煙者呼出來的煙霧，以及通過煙紙滲透出來的 煙草物質。 二手煙霧中的粒子會與周圍的空氣結合，形成其他化合物 ;「被動吸煙」 是指非吸煙者處於二手煙的環境當中。

二手煙的成份和特性

二手煙霧含有4,000多種的化學粒子和氣體，當中一些有毒氣體的濃度比 吸煙者吸入的主流煙更高。室內吸煙區有接近85%之煙氣由「支流煙」所 組成。 二手煙煙霧中還包括了焦油、尼古丁、苯并芘等粒子，以及有毒氣體如一 氧化碳、亞摩尼亞、甲醛、丙烯醛等。 這些香煙煙霧的物質甚至已被證實帶有刺激性或被列為致癌物質。

資料來源: 國立陽明大學 National Yang-Ming University, Taiwan, ROC

https://www.ym.edu.tw/mto/documents/nosmoking.htm