I have heard many things about smoking and a main issue as of one being that 2nd hand smoking is worse than 1st hand smoking itself? (I do not smoke I am just around someone who does smoke)

Is this rumor true? If so why is this, and what should I do if I can smell it or if I am around them when they light the cigarette?

  • 2
    Hi fbleb, welcome! Part of SE is providing the source of your information, including what you've found when trying to answer your own question. For future questions, consider that someone answering may want to see where you got that information/rumor. So if you google it and show in your post, that would improve the quality of your question and the potential answer you will get. For future reference, as @Narusan already nailed this answer!
    – DoctorWhom
    Aug 16, 2017 at 16:56

1 Answer 1



Yes, if one was to inhale the same amount of smoke passively as smokers inhale actively, it would be more dangerous. This is hardly the case though, as smokers also inhale parts of second hand smoke, and because as always, dosis facit venenum.

Risk of Second Hand Smoke

Risk of developing cancer

Exposure to secondhand smoke raises the risk -- by as much as 30 percent [1.3 times] -- that others will get lung cancer and many other types of cancer, it can lead to emphysema, and it is bad for your heart.

Source: WebMD, Emphasis Mine, Annotation Mine

The lower risk of developing cancer is because passive smokers don't inhale the same amount of smoke - you usually walk past a smoker and not stand right next to them until they have finished their cigarette.

Inhalation of toxic fumes

There are 2 types of tobacco smoke:

  1. Mainstream smoke, which is directly inhaled through the mouth end of the cigarette
  2. Sidestream smoke, which comes from the burning tip of the cigarette

Second-hand smoke is made up of sidestream smoke and exhaled mainstream smoke, mixed with the surrounding air.

Sidestream smoke is about 4 times more toxic than mainstream smoke, although people inhale it in a more diluted form. This is because sidestream smoke contains much higher levels of many of the poisons and cancer-causing chemicals in cigarettes, including:

  • At least 3 times as much carbon monoxide
  • 10-30 times more nitrosamines
  • Between 15–300 times more ammonia

Source: cancerresearchuk.org

However, the total amount of toxic fumes passive smokers inhale is less than what smokers inhale, because the former are not exposed to smoke as often as the latter.

Risk of Developing Heart Diseases or Strokes

Breathing secondhand smoke can cause coronary heart disease, including heart attack and stroke. Know the facts:

  • Secondhand smoke causes nearly 34,000 early deaths from coronary heart disease each year in the United States among nonsmokers.

  • Nonsmokers who breathe secondhand smoke at home or at work increase
    their risk of developing heart disease by 25–30%.

  • Breathing secondhand smoke interferes with the normal functioning of the heart, blood, and vascular systems in ways that increase your risk of having a heart attack.

  • Even briefly breathing secondhand smoke can damage the lining of blood vessels and cause your blood to become stickier. These changes
    can cause a deadly heart attack.

Source: cdc.gov

Again, the risk is lower than the risk of smokers because it is only an exposure during work or at home and are not expected to inhale the same amount of smoke as bystanders as smokers do.

Risks of First Hand Smoke

Risk of developing cancer

People who smoke cigarettes are 15 to 30 times more likely to get lung cancer or die from lung cancer than people who do not smoke. Even smoking a few cigarettes a day or smoking occasionally increases the risk of lung cancer. The more years a person smokes and the more cigarettes smoked each day, the more risk goes up.

Source: cdc.gov, Emphasis Mine

Toxic fumes

Cigarette smoke is a mixture of over 4000 chemicals, many of which are harmful to the human body. All currently available tobacco products that are smoked deliver substantial amounts of toxic chemicals to their users and those who breathe their smoke.

Of the more than 4000 chemicals present in cigarette smoke, more than 60 have been identified as cancer causing chemicals, 11 of which are known to cause cancer in humans and 8 that probably cause cancer in humans.

With approximately one non-smoker dying due to secondhand smoke exposure for every eight smokers dying of smoking-related disease it is no surprise that secondhand smoke has been designated a known human carcinogen (cancer-causing agent). Further, about half of regular smokers will die of a smoking-related disease and have a reduced life expectancy of about 13 to 16 years as compared with non- smokers.

Source: Australian Department for Health, Emphasis Mine

Risk of Heart Diseases and Strokes

If you smoke, your chance of dying from a heart attack is 2 to 3 times greater than that of a person who does not smoke. About 1 out of 4 heart attacks is believed to be directly related to smoking. Smoking is a much more important risk factor for a heart attack than high cholesterol, obesity, high blood pressure, or stress. A person who smokes is twice as likely to die from a stroke as a person who does not smoke.

Source: WebMD, Emphasis Mine

If you have children

Second hand smoking is especially damaging to children:

Every day millions of children in the UK are exposed to secondhand smoke, which puts them at increased risk of lung disease, meningitis and cot death. Treatment, hospital and GP visits for secondhand smoke related illnesses cost the NHS more than £23.6 million each year.

Source: gov.uk, Emphasis Mine

Early exposure to chemicals is a lot more damaging than during adulthood.

Passive smoking causes lasting damage to children's arteries, prematurely ageing their blood vessels by more than three years, say researchers.

Source: BBC.com

This can lead to early heard attacks and other coronary diseases.

Exposure of unborn children to tobacco smoke may also increase the risk of miscarriage, low birth weight and sudden infant death syndrome (SIDS), or ‘cot death’. There is strong evidence that the babies of mothers who smoke after birth have more lung diseases in their first year of life and have double the normal risk of serious airway infections.

Source: Gov.au

If you have kids, you definitely should follow the advice below.

What you can do

You can protect yourself and your family from secondhand smoke by:

  • Quitting smoking if you are not already a nonsmoker
  • Not allowing anyone to smoke anywhere in or near your home
  • Not allowing anyone to smoke in your car, even with the windows down
  • Making sure your children’s day care center and schools are tobacco-free
  • Seeking out restaurants and other places that do not allow smoking (if your state still allows smoking in public areas)
  • Teaching your children to stay away from secondhand smoke.
  • Being a good role model by not smoking or using any other type of tobacco.

Source: cdc.gov

  • 1
    The answer provides the evidence that second-hand smoking is harmful, but no evidence that it is more harmful than first-hand smoking. You are actually suggesting this in your opening. Even if one inhales the same amount of smoke as an active smoker, it's not the same smoke and no evidence that is more dangerous. I'm not trying to manipulate any definitions here, but if something is dangerous, it needs to be practically dangerous (a higher percent of diseases in passive than in active smokers), not just somehow theoretically more dangerous.
    – Jan
    Apr 13, 2018 at 13:16
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    @Narusan-in-coma How could smokers not inhale SHS? They breath the same air the person standing next to them breaths.
    – Carey Gregory
    Apr 13, 2018 at 15:22
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    @Narusan-in-coma Smokers breathe the ambient air that they just blew clouds of smoke into, and they have a burning cigarette smoldering away in their immediate proximity every second its lit. I'm quite confident that smokers are exposed to far more SHS than non-smokers.
    – Carey Gregory
    Apr 13, 2018 at 23:31
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    @Narusan-in-coma Your own wording: "second hand smoking is more dangerous than first hand smoking, but only if you inhale the same amount of smoke, which you don't." Your words. You said it here and you said it in your article opening: second-hand smoking is not more dangerous than first-hand smoking, because you don't inhale nearly the same amount of smoke as the active smoker.
    – Jan
    Apr 14, 2018 at 8:01
  • 1
    An active smoker smokes a cigarette for 5 minutes, inhaling first-hand and his/her own second-hand smoke. A passive smoker stands nearby inhaling only the second-hand smoke for the same 5 minutes. This is comparable. Second-hand smokE supossedly being 4 times more toxic than first-hand smoke does not automatically make second-hand smokING (time, amount...) more harmful.
    – Jan
    Apr 14, 2018 at 11:06

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