Why do cigarettes cause cancer?

[bascule]

This seems to be an issue of much confusion, especially since I've heard many trying to claim that nicotine is in and of itself a carcinogen. As far as I can tell these are the primary carcinogens in cigarettes:

 

• Polonium-210 and Lead-210: Radioactive isotopes which emit ionizing alpha radiation, making them extremely mutagenic. They are present in chemical fertilizers enriched with phosphate and comes in the form of either soluble or insoluble compounds. The soluble compounds are removed from the body through natural processes, whereas the insoluable compounds remain in the lungs and bombard lung tissue with ionizing alpha radiation.
   
  According to this site:
   

  Polonium -210 is the only component of cigarette smoke that has produced cancers by itself in laboratory animals by inhalation - tumors appear at a level five times lower than the dose to a heavy smoker.
   
  Lung cancer rates among men kept climbing from a rarity in 1930 (4/100,000 per year) to the No. 1 cancer killer in 1980 (72/100,000) in spite of an almost 20 percent reduction in smoking. But during the same period, the level of polonium -210 in American tobacco had tripled. This coincided with the increase in the use of phosphate fertilizers by tobacco growers - calcium phosphate ore accumulates uranium and slowly releases radon gas.
   
  As radon decays, its electrically charged daughter products attach themselves to dust particles, which adhere to the sticky hairs on the underside of tobacco leaves. This leaves a deposit of radioactive polonium and lead on the leaves. Then, the intense localized heat in the burning tip of a cigarette volatilizes the radioactive metals. While cigarette filters can trap chemical carcinogens, they are ineffective against radioactive vapors.

 

• Nitrosamine: A carcinogenic compound which appears to result primarily from the use of direct fire curing. Nitrosamine used to be found in beer, however beer manufacturers switched to indirect fire curing of barley in the 1980s and reduced the levels of nitrosamine betlow detectability. Some cigarette manufacturers have switched to indirect fire curing, but Marlboros were found to have the highest level of nitrosamine in the world.

 

• Benzopyrene: A carcinogenic compound which appears to arise through the burning of organic matter and is thus a seemingly unavoidable consequence of smoking anything organic.
  

 

I am very curious why the EPA and the rest of the government continue to allow two carcinogens which seem to be direct consequences of the cigarette manufacturing process to remain in cigarettes, especially with the enormous burden cigarette smokers place upon the national healthcare infrastructure. If anyone has knowledge of exactly how carcinogenic these particular chemicals (or any I haven't listed) are in relation to each other I'd certainly like to know (Dr. C. Everett Koop is anecdotally quoted as having said in 1990 on US national television that radioactivity in cigarettes accounts for at least 90 per cent of all smoking related cancers.)

 

Wouldn't requiring organic farming methods for the production of tobacco virtually eliminate the presence of Po-210 and Pb-210, and wouldn't mandating the use of indirect fire curing dramatically reduce nitrosamine levels? Nitrosamine has been virtually eliminated in Snus, a Swedish brand of smokeless tobacco.

 

So, bottom line, would eliminating, or at least dramatically decreasing the levels of Po-210/Pb-210 and nitrosamine in cigarettes dramatically reduce their potential for harm?

[Douglas]

I am very curious why the EPA and the rest of the government continue to allow two carcinogens which seem to be direct consequences of the cigarette manufacturing process to remain in cigarettes, especially with the enormous burden cigarette smokers place upon the national healthcare infrastructure. [/b']

Do you have any data to support the above (highlighted) statement ?

 

The bigger question is....how much does it cost the taxpayer for a person to die ? For example: A smoker may die at age 65 with minimal health care and no burden on the social security system. A non smoker may die at the age of 90, with minimal health care, but 10 years in a publicly funded nursing home and 25 years on the public dole via the SS system.

[blike]

Do you have any data to support the above (highlighted) statement ?

 

The bigger question is....how much does it cost the taxpayer for a person to die ?

That's another good discussion, but I don't think that's where the original poster intended to go with this thread.

[bascule]

Do you have any data to support the above (highlighted) statement ?

 

According to "The Price of Smoking" by Duke University economist Frank Sloan and four colleagues (available through MIT Press) the cost of smoking to "pooled-risk programs like Medicare, Medicaid, group life insurance and sick leave" is estimated to be $1.44/pack, and estimate the lifetime "social cost" of smoking to be $106,000 for women and $220,000 for men.

 

That's another good discussion, but I don't think that's where the original poster intended to go with this thread.

 

No, not at all, and I don't want to see it derailed. Smoking is also the #1 cause of "preventable death" in America. We've tried very very hard to make people stop smoking and prevent new people from starting, but that hasn't worked. However, isn't this a problem that could be dramatically mitigated on the manufacturing side? Wouldn't one of the ways we could dramatically decrease the number of deaths associated with smoking to eliminate all preventable carcinogens?

[lucaspa]

Cigarrette smoke also contains a huge number of reactive oxygen species -- over 200 have been identified if memory serves. These can react with DNA causing mutations.

 

What is the source of Po or Pb? I suspect Po or Pb is in the soil, so organic farming isn't going to change that.

 

As to health care costs, remember that the cigarette smoker does not die immediately and suffers from chronic illness for years before death, including lung cancer (with the associated treatments), heart disease, and other respiratrory ailments. Here are some references where you can start investigating the monetary cost of smoking for the health care system and society. Look up the abstracts in PubMed.

 

1: Minkoff NB.

Analysis of the current care model of the COPD patient: a health outcomes

assessment and economic evaluation.

J Manag Care Pharm. 2005 Jul;11(6 Suppl A):S3-7; quiz S20-2.

PMID: 15998173 [PubMed - in process]

 

2: Centers for Disease Control and Prevention (CDC).

Annual smoking-attributable mortality, years of potential life lost, and

productivity losses--United States, 1997-2001.

MMWR Morb Mortal Wkly Rep. 2005 Jul 1;54(25):625-8.

PMID: 15988406 [PubMed - indexed for MEDLINE]

 

3: Yang MC, Fann CY, Wen CP, Cheng TY.

Smoking attributable medical expenditures, years of potential life lost, and

the cost of premature death in Taiwan.

Tob Control. 2005 Jun;14 Suppl 1:i62-70.

PMID: 15923452 [PubMed - indexed for MEDLINE]

 

4: Max W, Rice DP, Sung HY, Zhang X, Miller L.

The economic burden of smoking in California.

Tob Control. 2004 Sep;13(3):264-7.

PMID: 15333882 [PubMed - indexed for MEDLINE]

 

5: Pauwels RA, Rabe KF.

Burden and clinical features of chronic obstructive pulmonary disease (COPD).

Lancet. 2004 Aug 14-20;364(9434):613-20. Review.

PMID: 15313363 [PubMed - indexed for MEDLINE]

[lucaspa]

There are over 5,000 different chemicals in cigarette smoke, very few of them have been completely identified. These are combustion products. Many of them, however, contain benzene rings, which makes them at least potentially carcinogenic.

[YT2095]

the way I understood it was that it occurs in 2 ways.

each cell has a lifespan with the amount of times it can replace itself, beyond this errors will occur.

the second is that you can cause Direct damage to information that the cell has about itself in order to replicate (knocking out part of the DNA "blue print")

and that also can cause errors when next it replicates, but occasionaly a part of the DNA "blueprint" that tells it that it`s job is done and to stop replicating gets scrubbed or damaged, so it keeps on doing it, and each of those cells carry that same corrupt data and THEY keep on doing it....

 

over simplified I`m sure, but that`s the basics as I rem it

[bascule]

What is the source of Po or Pb?

 

Calcium phosphate contaminated with radon, used in chemical fertilizers (see the above quoted section of the web site I linked)

 

There are over 5,000 different chemicals in cigarette smoke, very few of them have been completely identified. These are combustion products. Many of them, however, contain benzene rings, which makes them at least potentially carcinogenic.

 

But how does that compare to an emitter of ionizing radiation?

[jdurg]

Ionizing radiation can only go so far, and the amounts of radioactive particles in the fertilizers isn't all that great to begin with. (The term chemical fertilizer makes me laugh because all fertilizers are chemicals. If you use 'natural' fertilizers, you will wind up with the same proportion of radioactive particles anyway. I can guarantee you that if you analyze any fruit or vegetable, you'll find radioactive particles in there. It all depends on the sources. Also, radon has a half-life of 2.8 days. It's not going to contribute anything to the radioactivity. Also remember that radon is a noble gas so it will not be chemically bound to anything. I think you are getting radon and radium confused.)

 

Anyway, once ionizing radiation has spent its energy, it can no longer cause any damage. With carcinogenic chemicals, however, the damage can continue to occur once it has affected one 'structure'. In addition, the amount of carcinogens in any type of smoke is gigantic compared to any possible radiation. If a geiger counter can pick up the radiation coming from a cigarette, then yes, you should worry. The thing is, there is simply not enough radioactive material in a cigarette to merit any type of 'fear'.

[bascule]

jdurg, I highly suggest you have a look at this paper and reevaluate your statements:

 

http://www.pnas.org/cgi/content/abstract/80/5/1285

 

Abstract:

 

Radiation Dose at Bronchial Bifurcations of Smokers from Indoor Exposure to Radon Progeny

 

E. A. Martell

 

Synergistic interactions of indoor radon progeny with the cigarette smoking process have been evaluated experimentally. Smoking enhances the air concentration of submicron particles and attached radon decay products. Fractionation in burning cigarettes gives rise to the association of radon progeny with large particles in mainstream cigarette smoke, which are selectively deposited in ``hot spots'' at bronchial bifurcations. Because smoke tars are resistant to dissolution in lung fluid, attached radon progeny undergo substantial radioactive decay at bifurcations before clearance. Radon progeny inhaled during normal breathing between cigarettes make an even larger contribution to the -radiation dose at bifurcations. Progressive chemical and radiation damage to the epithelium at bifurcations gives rise to prolonged retention of insoluble 210Pb-enriched smoke particles produced by tobacco trichome combustion. The high incidence of lung cancer in cigarette smokers is attributed to the cumulative -radiation dose at bifurcations from indoor radon and thoron progeny--218Po, 214Po, 212Po, and 212Bi--plus that from 210Po in 210Pb-enriched smoke particles. It is estimated that a carcinogenic -radiation dose of 80-100 rads (1rad=0.01J/kg=0.01 Gy) is delivered to [math]10^7[/math] cells ( [math]10^6[/math] cells at individual bifurcations) of most smokers who die of lung cancer.

 

But anyway, to respond to your post:

 

Ionizing radiation can only go so far

 

We're talking about particles which are getting deposited directly in contact with lung tissue, so the distance it has to go is roughly from the cell wall to the cell nucleus.

 

and the amounts of radioactive particles in the fertilizers isn't all that great to begin with.

 

They don't have to be. Think of the cumulative effect of smoking a pack a day.

 

Also, radon has a half-life of 2.8 days. It's not going to contribute anything to the radioactivity.

 

What about the rest of the radon decay sequence?

 

radon-222, with a half-life of 3.825 days, emits an alpha particle to become polonium-218.

polonium-218, with a half-life of 3.05 minutes, emits an alpha particle to become lead-214.

lead-214, with a half-life of 26.8 minutes, emits a beta particle and a gamma ray to become bismuth-214.

bismuth-214, with a half-life of 19.7 minutes, emits either an alpha particle or a beta particle and a gamma ray to become either thallium-210 or polonium-214.

polonium-214, with a half-life of a 150 microseconds, emits an alpha particle to become thallium-210.

thallium-210, with a half-life of 1.32 minutes, emits a beta particle to become lead-210.

lead-210, with a half-life of 22 years, emits a beta particle and a gamma ray to become bismuth-210.

bismuth-210, with a half-life of five days, emits a beta particle to become polonium-210.

polonium-210, with a half-life of 138 days, emits an alpha particle and a gamma ray to become lead-206.

lead-206 is a stable isotope of lead.

 

Polonium-210 and Lead-210 are the isotopes found in tobacco, and they have half lives of 22 years and 138 days respectively.

 

Also remember that radon is a noble gas so it will not be chemically bound to anything. I think you are getting radon and radium confused.

 

Please see the paper I linked in regards to radon products found in tobacco.

 

Anyway, once ionizing radiation has spent its energy, it can no longer cause any damage. With carcinogenic chemicals, however, the damage can continue to occur once it has affected one 'structure'.

 

Won't most of these chemicals be flushed out of the lungs through natural processes, as opposed to insoluable Pb210/Po210 compounds which will remain in the lungs and continue to bombard the tissue with ionizing alpha radiation?

 

Anyway, I'd like to see what you have to say about that paper...

[bascule]

Internal memos from Philip Morris from April 1980 indicate that the tobacco companies have been fully aware of radioactivity in cigarettes for over two decades.

 

That phosphate fertilizer (specifically superphosphate fertilizer) contains natural radioactivity is a well established fact.

 

Natural uranium accumulates in the phosphate rock and has been shown to substitute for calcium in the rock structure. Uranium and its daughters are thus carried through the mining and manufacturing process and appear in the commercial product. Soils to which these products are applied show an increase in radioactivity over that naturally present and this increase is a function of the rate of application and the number of years that the fertilizers have been used.

 

M. E. Counts has shown that the specific [radio]activity [...] increases as the particle size of the superphosphate fertilizer decreases. Thus the smaller particles, which would be more likely to be made airborne by normal farming practices, would be expected to settle out on the tobacco leaves during the growing season and/or be more readily taken up by the plant root system.

 

²¹⁰Pb and ²¹⁰Po are present in tobacco and smoke. The Martell "Hot Particle Theory" has been addressed in the past and has apparently lost popularity in the scientific community (lack of recent publicity in this field). For [math]\alpha[/math]-particles from ²¹⁰Po to be the cause of lung cancers is unlikely due to the amount of radioactivity of a particular energy necessary for induction Evidence to date, however, does not allow one to state that this is an impossibility. (Ed: and of course, more recent evidence says just the opposite)

 

The recommendation of using ammonium phosphate instead of calcium phosphate as fertilizer is probably a valid but expensive point. What Martell appears to be suggesting is the purification of phosphate rock to obtain P₂O₅ or H₃PO₄ free of calcium (uranium and daughters) and inert materials. Preparation of ammonium phosphate for fertilizer would then yield a product greatly reduced in or free of the natural radioactivity present in the parent phosphate rock.

[bascule]

There are over 5,000 different chemicals in cigarette smoke, very few of them have been completely identified.

 

I'm under the impression that the combustion products present in cigarette smoke have been studied extensively. Do you have any source to corroborate this statement?

 

Many of them, however, contain benzene rings, which makes them at least potentially carcinogenic.

 

I'm wondering if further discoveries somehow discredited Martell's work, as from his paper it seems pretty clear that your lungs get exposed to a considerable amount of radiation when smoking cigarettes indoors. I really wish someone authoritative would break down the known carcinogens and assess their potential risks statistically in some sort of manner.

[Bio-Hazard]

If I remember right, many people before the nuclear bombs were set off had obtained forms of cancer inside of their body from things such as tobacco. I sometimes wonder if those had some type of addition to the recent forming of cancer in people in the past 50 years.

 

Another thing I question is, "What was inside of their cigarettes they smoked 100 years ago?" Many people argue with the idea that cigarettes don't cause cancer, yet I'm willing to argue that something in coorelation with them does.

 

Either they bring down your resistance to radioactivity in the environment or else the carcinogens in cigarettes. I do believe something is at work though, because the majority of people who smoke will have a type of cancer after smoking for long periods of time.

[bascule]

Another thing I question is, "What was inside of their cigarettes they smoked 100 years ago?" Many people argue with the idea that cigarettes don't cause cancer, yet I'm willing to argue that something in coorelation with them does.

 

Cigarettes from 100 years ago are likely to contain nitrosamine but not polonium-210. This began happening with the use of phosphate fertilizers.

 

Either they bring down your resistance to radioactivity in the environment or else the carcinogens in cigarettes. I do believe something is at work though, because the majority of people who smoke will have a type of cancer after smoking for long periods of time.

 

There are multiple carcinogens in cigarettes. But if we can fix the manufacturing process to eliminate the biggest offenders, wouldn't that dramatically reduce the incidence of cancer associated with smoking?

[bascule]

Wow, this is awesome:

 

http://www.timesonline.co.uk/article/0,,2087-1859508,00.html

 

'Safe cigarette' claimed to cut cancer by 90%

 

BRITISH American Tobacco (BAT) is to launch a controversial “safer cigarette” designed to cut the risk of smoking-related diseases such as cancer and heart failure by up to 90%.

 

The cigarettes use tobacco treated to produce lower levels of cancer-causing chemicals. They also incorporate a new type of filter said to remove more of the remaining toxins.

 

The company wants to launch the cigarettes in 2006 but has kept the move secret, knowing it would infuriate anti-smoking groups.

 

Campaigners will dismiss any attempt to reinvent cigarettes as a less harmful product as a cynical ploy to recruit more smokers when the habit is already killing 114,000 Britons a year and the government is proposing curbs on smoking in public places.

 

Past claims to have found safer forms of smoking, such as the introduction of low-tar cigarettes in the 1970s, have all proven false. They were found to be as harmful as high-tar versions because people smoked more and took deeper drags.

 

Despite this history, BAT executives talk privately of “risk free” or low-risk cigarettes and suggest they might cut the chance of disease by as much as 90%.

 

John Britton, professor of epidemiology at Nottingham University, said: “Anything involving inhaling smoke is unsafe. These new cigarettes could be more like jumping from the 15th floor instead of the 20th: theoretically the risk is less but you still die.”

 

This weekend, BAT confirmed plans for the launch. David Betteridge, a spokesman, said: “They look and taste like normal cigarettes.”

 

Betteridge refused to divulge the name under which the cigarettes would be marketed or give details of how they worked. They were designed by scientists at the firm’s research centre in Southampton.

 

The cigarettes use “trionic” filters with three layers, each of which removes a different set of toxic compounds, while still allowing nicotine — the main addictive element in tobacco — to enter the lungs. The tobacco is also mixed with an inert “chalky” substance to retain more of the toxins in the ash.

 

BAT also claims to have improved the way it dries tobacco leaves to reduce cancer-causing toxins when burnt.

 

Even if they benefit smokers, such cigarettes would not prevent passive smoking. Deborah Arnott, director of Action on Smoking and Health, said: “Cigarette smoke contains about 4,000 different chemicals, many of which are toxic. These filters and tobaccos can make no more than a marginal difference.”

 

BAT will not be making any explicit claims that its cigarettes are safer, but will instead describe the product as “potentially safer”. It is likely to focus its advertising on the new technology, hoping that smokers will assume they are safer.

 

Betteridge said the company accepted there was “no such thing” as a truly safe cigarette and that the best way to minimise risk was to stop smoking.

 

See, that's the really sad thing, anti-smoking groups oppose safer cigarettes because they would weaken their arguments against smoking, so instead they try to spin safer cigarettes AGAINST the companies which wish to make them, claiming they merely want to recruit more smokers...

[ecoli]

I've heard of this company making cigarettes out of lettuce. Doesn't seem too "smooth" to me.

[bascule]

BAT also claims to have improved the way it dries tobacco leaves to reduce cancer-causing toxins when burnt.

 

This part of the article obviously speaks to indirect fire curing...

[Danecookie]

hmmm... nice info but anyway i dont smoke .

 

[sunspot]

I am not sure if it is possible to isolate cigarettes from environmental causes. Back 20-30 years ago smoking in the work place was common. Blue collar workers in factories, with all the chemical presents, such a solvents, machine oils, plastic monomers, etc., smoked these chemicals through the cigarettes. Does anyone know what percent of smokers over the past 50 years survived without cancer? Maybe we need to look at what allows certain people to resist the effects. Maybe one size does not fit all.

[aj47]

Simple question but how are the non radiocative compounds carcinogenic e.g. benzene. What property is it that gives rise to cell mutation ?

[RyanJ]

Carcinogens may cause cancer by altering cellular metabolism or damaging DNA directly in cells, which interferes with normal biological processes. Usually cells are able to detect this and attempt to repair the DNA; if they cannot, they may undergo programmed cell death to protect the organism.

 

I don't think we are really shure exactly how they work but they affect the cellular metabolism and can cause damage to the DNA resulting in loss of functionality and death of the cell or extreme multiplication.

 

Cheers,

 

Ryan Jones