On the carcinogenicity of marijuana smoke.

Discussion in 'Medicinal Marijuana' started by Ultrouve, Jul 19, 2009.

  1. Ultrouve Ultrouve

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    • Since: Jul 19, 2009
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    On the carcinogenicity of marijuana smoke.
    A hypothetical link between marijuana smoking and cancer has been established based on the following observations: 1. Marijuana smoke contains carcinogenic hydrocarbons; 2. Cannabinoid administration promotes cancer under certain laboratory conditions; 3. Lesions similar to those caused by tobacco smoke are found in the bronchial epithelium of marijuana smokers; 4. Marijuana tar produces tumors when painted on the skin of animals. The best evidence to date on the link between marijuana and cancer, however, derives from large case-control studies -- especially population-based studies. Such studies tend to suggest, if anything, an inverse association between marijuana use and cancers.

    I. Marijuana smoke contains higher levels of carcinogenic polycyclic aromatic hydrocarbons (PAH) than those found in tobacco smoke.
    As a rule, the level of carcinogenic PAHs within a chemical mixture is less important than the overarching influence of the mixture on carcinogenic PAH activation (Mahadevan et al. 2007). Indeed, marijuana smoke is presumed carcinogenic not only because it contains carcinogenic PAHs, but also because cannabinoids, in their own right, influence the cytochrome enzymes (CYP1) that determine carcinogenic PAH activation (Roth et al. 2001). Perhaps due to their phenolic hydrocarbon structure, cannabinoids share the anti-carcinogenic disposition of polyphenols to increase levels of CYP1A1 messenger RNA while competitively reducing CYP1A1 enzyme ativity through aryl hydrocarbon receptor ligation (Ciolino et al. 1998). Not surprisingly, spiking tobacco tar with delta-9 THC markedly reduced carcinogenic activity (Roth et al. 2001).

    II. Cannabinoid administration promotes cancer in mice.
    Intraperitoneal administration of immunosuppressive cannabinoids promotes cannabinoid-resistant lines of cancer in immune-competent strains of mice (Gardner et al. 2003, McKallip et al. 2005, Zhu et al. 2000); however, the preponderance of in vivo studies, have shown that cannabinoid administration -- either locally or systemically -- inhibits the growth of cancer (Aguado et al. 2007, Bifulco et al. 2001, Bifulco et al. 2004, Blazquez et al. 2003, Blazquez et al. 2004, Blazquez et al. 2006, Caffarel et al. 2006, Carracedo et al. 2006, Casanova et al. 2003, Chan et al. 1996, Duntsch et al. 2006, Grimaldi et al. 2006, Ligresti et al. 2006, Massi et al. 2004, McKallip et al. 2002, McKallip et al. 2006, Munson et al. 1975, Pisanti et al. 2007, Preet et al. 2008, Recht et al. 2001, Sanchez et al. 2001). The neoplastic effects of cannabinoids may vary according to the degree of malignancy, which, in turn, may depend on the presence of cannabinoid receptors (Ellert-Miklaszewska et al. 2007, Xu et al. 2006). Cannabinoids may control the growth of human cancers, in part, through the cannabinoid receptor 2 gene (CNR2), which emerged as the best-connected 'super hub' in an inferred large-scale association network for breast cancer data (Schäfer et al. 2005).

    The posological question remains as to whether smoking marijuana produces antineoplastic concentrations of cannabinoids in the exposed tissues of recreational or medicinal users. Perhaps the biggest obstacle to developing chemotherapy for lung cancer is the fact that optimal tissue concentrations cannot asily be reached in the bronchial epithelium, where anti-neoplastic cannabinoids from smoked marijuana naturally concentrate. Inhalation of marijuana smoke was shown to produce 800-1000% higher concentrations of THC in the lungs compared with those found in blood (75 +/- 38 ng/g wet wt tissue vs. 9.2 +/- 2.0 ng/ml: Sarafian et al. 2006). If the bronchial epithelium does, in fact, harbor malignant neovasculature prior to clinical detection, then smoking marijuana may treat lung cancer at its roots early on, while treatment still matters.

    III. Marijuana smokers develop 'precancerous' lesions similar to those caused by tobacco smoke.
    Marijuana smoking causes 'precancerous' epithelial lesions (PEL) such as squamous metaplasia (SM) and other changes associated with respiratory exposure to smoke in general (Barsky et al. 1998). On the one hand, SM not only follows exposure to potent carcinogens in laboratory strains of mice, but it also precedes the development of squamous cell carcinoma of lungs (SCCL) in humans. On the other hand, the multiplicity of SM was higher among SCCL-resistant mice (e. g., C57BL/6J = 5.0 - 6.0: Wang et al. 2004) than it was among SCCL-susceptible mice (e. g., NIH Swiss = 2.1 - 4.9: Wang et al. 2004); in humans, PEL such as SM are generally reversible and often regress spontaneously (Winterhalder et al. 2004).

    As it turns out, PEL may have little, if any, predictive value. In fact, according to recent findings, "Distribution and outcome of preneoplastic lesions have been found to be unrelated to various risk factors such as smoking. . . The 54% regression rate of all preneoplastic lesions, 26% to 39% progression rate to CIS/SCC of individuals with lower-grade dysplasia or severe dysplasia with no significant difference in progression rate and time to progression combined with nostepwise histologic changes unrelated to the initial histologic grading.... The initial WHO classification of any preneoplastic lesion cannot be reliably used for accurate risk assessment of field carciogenesis" (Breuer et al. 2005).

    IV. Marijuana tar produces tumors when painted on the skin of animals.
    Tar from marijuana smoke, like that from tobacco smoke, was shown to produce benign tumors (i.e., squamous-cell papilloma) when painted on the skin of animals (Hoffman et al. 1975); however, tar from tobacco smoke caused frank malignancies (i.e., squamous-cell carcinoma), whereas tar from marijuana smoke did not. In subsequent research on monkeys, prolonged exposure to marijuana smoke failed to produce any carcinogenic effects (Talaska et al. 1992). Interestingly enough, exposure to marijuana smoke was shown to retard the growth of sarcoma in rats (Watson 1989). This inhibition was unrelated to the cannabinoid content of the smoke.

    The appearance of papillomas on the skin indicates that tar from marijuana smoke, like that from tobacco smoke, is an effective initiator of benign tumors; however, the absence of squamous-cell carcinoma is consistent with the observation that cannabinoid administration induces the regression of squamous-cell carcinoma of skin by transforming the vascular hyperplasia of engorged tumors into pallid networks of small, differentiated capillaries (Casanova et al. 2003). Such transformation reflects the tendency of cannabinoids to thwart the neoplastic expression of angiogenic factors (Casanova et al. 2003, Portella et al. 2003).

    To date, no animal study has demonstrated the carcinogenicity of marijuana smoke. Future studies would, ideally, be conducted with animal models that reflect the stages of both initiation and progression observed in human cancer, but no such model currently exists (Khanna et al. 2005). In vivo studies on the neoplastic properties of cannabinoids have typically been conducted with BALB/c, B6C3F1, and C57BL/6 murine strains, which are not susceptible to chemically-induced SCCL. Even the most susceptible strains do not develop SCCL as the result of exposure to tobacco smoke (Wang et al. 2004), the definitive benchmark for human carcinogens.

    Murine SCCL results from exposure to a single carcinogen, whereas human SCCL typically results from exposure to complex mixtures of carcinogens such as those found in smoke. Unlike murine SCCL, adenocarcinoma of the lungs (ACL) in mice results from tobacco smoke exposure (Hutt et al. 2005). Lifetime inhalation of tobacco smoke was recently shown to induce ACL in B6C3F1 mice, which have a low baseline incidence of pulmonary neoplasia.

    The above study is recognized for being the first to adequately demonstrate the cancer-initiating effects of tobacco smoke exposure in the lungs of animals (Hecht 2005), yet it unexpectedly showed an increase in lifespan associated with lifetime tobacco smoke exposure, an observation attributed to reduced caloric intake or bodyweight (Hutt et al. 2005). Reduced caloric intake or bodyweight caused by tobacco smoke exposure may have increased survival in B6C3F1 mice despite the increased burden of tumors. In an earlier study on B6C3F1 mice, a decrease in bodyweight and tumors followed the administration of THC (Chan et al. 1996). Researchers from both of these studies acknowledge the importance of controlling for caloric intake/bodyweight the future studies (Huff et al. 2005, Hutt et al. 2005).

    In contrast to the mice that develop adenocarcinoma from carcinogen exposure, mice implanted with human adenocarcinoma exhibit the metastasis and reduced survival typically observed in humans with adenocacinoma (Meuwissen et al. 2005). While such xenograft models do not fully capture the natural behavior of human cancer (Gutmann et al. 2006), compared with chemically-induced models, they are more practical for evaluating malignant progression.

    In evaluating the carcinogenicity of any type of smoke, it might help to remember that it was epidemiology, rather than animal research, that first incriminated tobacco smoke as a carcinogen (Doll 1988, Proctor 2004). While there have been lurid case-reports of tobacco-related cancers among young and middle-aged marijuana smokers (Sridhar et al. 1994), a large cohort study found no evidence of precocious tobacco-related cancers among middle-aged marijuana smokers (Sidney et al. 1997).

    As tobacco-related cancers develop increasingly with age and exposure, the cohort study did not follow its participants for long enough to ascertain the relationship between marijuana smoking and tobacco-related cancers. Small case-control studies -- especially studies failing to control for the effects of tobacco smoking -- have inconsistently shown an association (Berthiller et al. 2008, Chacko et al. 2006, D'Souza et al. 2007, Hsairi et al. 1993, Llewellyn et al. 2004a, Llewellyn et al. 2004b, Sasco et al. 2002, Voirin et al. 2006, Zhang et al. 1999), whereas large case-control studies -- especially population-based studies -- have, if anything, shown an inverse association (Berthiller et al. 2009, Ford et al. 2001, Hashibe et al. 2006, Liang et al. 2009, Rosenblatt et al. 2004, Zhu et al. 2002).

    Despite their best efforts to prove an association, some authors (viz., Berthiller et al. 2009) apologize for not including sufficient numbers of never tobacco & alcohol users -- which is, of course, absurd -- unless alcohol/tobacco consumption exerts anticarcinogenic effects that mitigate the carcinogenic effects of marijuana consumption. The only way to prove that smoking marijuana does not cause cancer would be if marijuana actually protects against it (Liang et al. 2009).

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  2. nornerator nornerator

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    • Since: Oct 28, 2005
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    While as a scientist I completely understand that it is important to break things down into pieces in order to understand something. In this case I think that confuses the issue a little bit. Also, the research is being done completely backwards.

    The important question is "Does normal marijuana use cause cancer in humans?" Human studies have not shown any link between marijuana use and cancer.

    Research should be conducted like this

    Test if marijuana causes cancer
    if yes, find out exactly how it causes cancer by breaking it down into small pieces.

    Instead they are simply trying to find any evidence that marijuana could be carcinogenic, even though what is really important is whether or not marijuana causes cancer in humans.
  3. Futuregrower Futuregrower

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    • Since: Jun 14, 2009
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    Agreed. This is the " it has never caused cancer so it is good" argument.

    Fact is, they rarely have large case studies of large groups of people who smoke lots of MJ per day, because.....it is illegal in most places. The places where it is legal or no-one cares have nowhere near the group size of cigarette smokers.


    1 pound of tobacco, pushed into filter tubes , makes about 600 cigs., or 3 cartons (30 packs). so 8 ounces = 300 cigs. 4 oz = 150 cigs. 2 oz = 75, 1 oz. = 37.5 cigs. This is about the same weight of tobacco in store-bought brands- in fact a little less, as you typically don't get as much tobacco in a roll-your-own.

    I used to smoke 2 packs of Marlboros a day. this is 40 cigarettes, or over 1 ounce of tobacco.
    Try finding a group of people to study who smoked 1 oz. of MJ a day for 10 years straight. I've never seen a billion-dollar company (RJ Reynolds) market a brand of MJ...........

    If you were to use Tobacco the way most people use MJ, the cancer risk is greatly reduced.

    Does the MJ itself (no smoke, say eating it) cause cancer? doubtful.
    Does smoking anything- MJ, cloves, Djarums, anything where you inhale smoke on purpose cause cancer? Probaly, if only form the particulate matter your lungs must cope with.

    I just hate the studies that use bad science to try to make MJ as good as possible.

    Can MJ cause cancer? yes.
    Have people who smoke only MJ gotten cancer? Yes.
    Can MJ shrink a tumor in a petri dish and still be carcinogenic in the human body, most notably inhaling the vapors/smoke? Absolutely. After all, Diet Coke, in a petri dish, will kill sperm cells. so will milk. This does not mean either of those things will kill sperm cells when you drink them.
    Shrinking tumors in a lab is one thing; killing them in the human body rely on many many factors.
    Not to mention the placebo effect / calming effect. You think it works, so it does = placebo. You like it, it calms you, maybe makes you hungry = helps your own body fight the cancer.

    So, sometimes MJ can be more helpful than harmful . Iv'e said it before- something can be a harm and a help both. A little MJ smoke = a little risk of cancer. But a little MJ smoke can also help with pain/nausea/ mental health, therefore out-weighing the negative effects.

    Sometimes more hurtful than helpful - doing big bong hits and holding them forever even worse than vaporizing the same amount.

    Sorry, but I truly dislike the 'science' that makes MJ out to be perfect/ never a carcinogen. Truth is, MJ Smoke does have carcinogens in it. It's just usually not inhaled in sufficient quantity to be a big risk. Risk, yes. Big risk, no.
    7 people like this.
  4. Herbania Herbania

    • Don't fear the reefer
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    Answer: Voporize
  5. Ss0p Ss0p

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    Nowadays everything causes cancer...
  6. nornerator nornerator

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    • Since: Oct 28, 2005
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    Yes marijuana smoke contains carcinogens, but it also contains many anti-carcinogens. Whether or not marijuana smoke increases your risk of developing a form of cancer is not known, but the human studies done (admittedly not end all be all proof) suggest no link between the development of cancer and marijuana smoke.

    In any event, smoking anything does have detrimental effects on health due to tar accumulation in the lungs and asphyxiation. For medical users with pain that is cannot be handled with vaporized cannabis, health benefits from smoked cannabis can outweigh the detrimental effects.

    If you are concerned about health, vaporize or eat your cannabis.

    The fact is there has been no good evidence that cannabis use increases cancer risk in the human studies done. I agree that we need more and better studies, but I'm not going to think cannabis causes humans to develop cancer when there isn't evidence to support it. It is certainly very plausible that cannabis smoke could cause cancer, but the human studies done simply do not support this.

    For now I'll stick with vapor
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  7. youareloveninja youareloveninja

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    • Since: Jun 26, 2009
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    also, even if all smoking causes cancer, commercial cigarettes also have a bunch of nasty shit aside from tobacco like pesticides which no doubt add in a big way to probably of getting cancer from smoking, i mean tobacco is a poison in most eyes, but i mean, pure synthetic chemicals that kill bugs and trace amounts of fiber glass are also gonna be very detrimental to your lungs, much more so theoretically than some organically grown tobacco.

    weed has none of these craziness its just the plant, sure smoke is not good for the lungs, and contains carcinogens, all smoke is like this because it has carbon from whatever is burning.. but ganj has also been shown to has antioxidants or anticarcinogens (maybe both?) that actually counteract this effect to a large degree, so as long as thats all you're smoking you should be fine, and yeah most people dont smoke an ounce daily

    why would that be a good study?

    its totally unrealistic, smoke an ounce of totally inert matter everyday and ull still have messed up lungs just because anything that is denser and dirtier than pure air and has a bunch of carbon in it is going to be detrimental and cause damage in some way...

    i mean smoking is not really healthy
    but cigarettes are some of the worst things you can smoke just because it combines an already harsh substance for your body (i mean just observe how your throat feels after you smoke or how your body feels an hour or so later..) with a bunch of additives that arent at all meant for human consumption...

    btw smoking an herb called mullein actually helps clear out your lungs and sinuses.. i do this after ive been smoking a lot of cigs, and it helps
  8. Futuregrower Futuregrower

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    • Since: Jun 14, 2009
    • Posts: 338
    Nornerator, I've not said otherwise. It is an example of a little risk overshadowed by a big gain. Someone already has a disease/condition that causes pain and no appitite? Weed, even smoked in big pipes and held in lungs, better than not eating, at least short term.

    There's also no evidence to support MJ smoke cures cancer. It may help relax a patient, make them eat, therefore giving their own body a chance to fight it off.

    I just really, really hate it when I hear "it's just a plant so it must be good" -type of arguments.

    Instead of doing what you do - you at least call for more & better studies/ research, too many people reason it thusly:
    1) I like weed. If MJ caused cancer I would have to stop smoking it.
    2) MJ is good because it doesn't cause cancer and I like smoking it.

    Well,......no. even if the truth turns out to be MJ smoke cures cancer, male pattern baldness, the common cold, poverty, illiteracy, breast cancer, and P.M.S., it is still bad reasoning. I would love for studies to be done.
    Alas, the reason studies aren't done is the very reasoning I hate.......because it is a plant needing no special treatment aside from drying and heat to use. There are lots of studies on the effects of cocaine, because you need a special enviroment (mountains, preferably) and special treatment ( ever see how many steps it takes to refine cocoa into cocaine?) to get cocaine.
    Anyway, I want more and better studies, but agree that MJ is fairly harmless, even more so when eaten or vaporized.

    Youareloveninja, are you sure that weed your smoking doesn't have as many chemicals as Marlboros? You know for a fact its 100% organic?
    It would be a good study because I know of very few people (none) who smoked an 1/8th ounce of tobacco once in a while, the way people do with MJ. if you test head to head, similar doses daily,similar ingestion routes, and 1 group still gets cancer easier, you just proved a theory.
    So, lets say average use for MJ is......arguments' sake, 1/8th oz a day.
    1/8th oz/day of tobacco = about 4.5 cigs a day.

    I know very very few smokers ever stop at 4.5 cigs a day.
    I know very few pot smokers smoking 1/8th oz a day , regularly, day in/out.
    So it could very well be cigs- even 100% organic tobacco- cause cancer easier because of greater use.
    Not healthy in low doses, just worse cos you get people smoking 1 ounce tobacco a day. After all, tobacco is just a plant that grows in the dirt.......
    oops, thats the MJ argument, sorry.

    Oh and Ss0p, according to the state of california, every product known to mankind causes cancer.
  9. Flock_of_Crows Flock_of_Crows

    • New Member
    • Since: Jul 14, 2009
    • Posts: 495
    well heres what i found recently Via fox news:

    While a clear increase in cancer risk was seen among cigarette smokers in the study, no such association was seen for regular cannabis users.
    Even very heavy, long-term marijuana users who had smoked more than 22,000 joints over a lifetime seemed to have no greater risk than infrequent marijuana users or nonusers.
    The findings surprised the study’s researchers, who expected to see an increase in cancer among people who smoked marijuana regularly in their youth.
    “We know that there are as many or more carcinogens and co-carcinogens in marijuana smoke as in cigarettes,” researcher Donald Tashkin, MD, of UCLA’s David Geffen School of Medicine tells WebMD. “But we did not find any evidence for an increase in cancer risk for even heavy marijuana smoking.” Carcinogens are substances that cause cancer. Tashkin presented the findings today at The American Thoracic Society’s 102nd International Conference, held in San Diego.




    Boomers Reaching Cancer Age
    The study population was limited to people who were younger than 60 because people older than that would probably not have used marijuana in their teens and early adult years.
    “People who may have smoked marijuana in their youth are just now getting to the age when cancers are being seen,” Tashkin says.
    A total of 611 lung cancer patients living in Los Angeles County, and 601 patients with other cancers of the head and neck were compared with 1,040 people without cancer matched for age, sex, and the neighborhood they lived in.
    All the participants were asked about lifetime use of marijuana, tobacco, and alcohol, as well as other drugs, their diets, occupation, family history of lung cancer, and socioeconomic status.
    The heaviest marijuana users in the study had smoked more than 22,000 joints, while moderately heavy smokers had smoked between 11,000 and 22,000 joints.
    While two-pack-a-day or more cigarette smokers were found to have a 20-fold increase in lung cancer risk, no elevation in risk was seen for even the very heaviest marijuana smokers.
    The more tobacco a person smoked, the greater their risk of developing lung cancer and other cancers of the head and neck. But people who smoked more marijuana were not at increased risk compared with people who smoked less and people who didn’t smoke at all.

    The THC Connection
    Studies suggest that marijuana smoke contains 50 percent higher concentrations of chemicals linked to lung cancer than cigarette smoke. Marijuana smokers also tend to inhale deeper than cigarette smokers and hold the inhaled smoke in their lungs longer.
    So why isn’t smoking marijuana as dangerous as smoking cigarettes in terms of cancer risk?
    The answer isn’t clear, but the experts say it might have something to do with tetrahydrocannabinol, or THC, which is a chemical found in marijuana smoke.
    Cellular studies and even some studies in animal models suggest that THC has antitumor properties, either by encouraging the death of genetically damaged cells that can become cancerous or by restricting the development of the blood supply that feeds tumors, Tashkin tells WebMD.
    In a review of the research published last fall, University of Colorado molecular biologist Robert Melamede, PhD, concluded that the THC in cannabis seems to lessen the tumor-promoting properties of marijuana smoke.
    The nicotine in tobacco has been shown to inhibit the destruction of cancer-causing cells, Melamede tells WebMD. THC does not appear to do this and may even do the opposite.
    While there was a suggestion in the newly reported study that smoking marijuana is weakly protective against lung cancer, Tashkin says the very weak association was probably due to chance.
    Cancer risk among cigarette smokers was not influenced by whether or not they also smoked marijuana.
    “We saw no interaction between marijuana and tobacco, and we certainly would not recommend that people smoke marijuana to protect themselves against cancer,” he says.

    hope this helps, :)
  10. Vendettagainst Vendettagainst

    • New Member
    • Since: Oct 11, 2008
    • Posts: 84
    The biggest problem with any cannabis research is the fact that you don't know if you're smoking the same thing they were, the same way, et cetera. Not to mention someone might have contaminated weed or they might be smoking less or more, based on how good the quality of their/your bud is.

    The bottom line? Smoking marijuana could cause cancer; however, no link has proven as of yet. While that doesn't mean it's completely safe, it could prove that it is safer than thought of. I find it interesting that it has the chemicals to cause cancer through the carcinogens, but it somehow doesn't cause cancer; the pre-drug for cancer anyone?
  11. buzz buzz

    • New Member
    • Since: Sep 24, 2007
    • Posts: 346
    I got one even better ...My wife makes excellent mini-cupcakes with cannabis oil and marijuana ...pop one before bed....sweet dreams:hail:
    1 people like this.
  12. jokaonfire jokaonfire

    • Guest
    • Since:
    • Posts: 0
    omg that is hard to understand...
    1 people like this.
  13. Futuregrower Futuregrower

    • New Member
    • Since: Jun 14, 2009
    • Posts: 338




    jokaonfire, it seems simple to me.......his wife makes itty-bitty cupcakes with oil that has THC in it, and she adds small amounts of MJ. I'm assuming she grinds it up or something, probably not throwing whole stems and buds in there.

    Buzz then comes along, eats a mini-cupcake right before bed, and he has sweet dreams.

    Hope this helped.




    :D
  14. teyber teyber

    • New Member
    • Since: Aug 8, 2009
    • Posts: 460
    i hate when people say that because i think you are saying we shouldn't worry about anything :rolleyes: with all due respect and not trying to cause a fight.

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