It is, of course, common knowledge nowadays that tobacco causes cancer: that that substance is, indeed, one of the most notorious carcinogens known. What I want to know is whether any other recreational drugs - legal or illegal - are known, or at least strongly suspected, to be carcinogenic. I know there’s a lot of controversy over marijuana and its potential to cause lung cancer, and have heard that alcohol has the potential to cause certain types of cancer as well (when taken to excess); does anyone know what the current verdict on these drugs and their respective carcinogenicities (I hope that’s a proper word!) is? And what about other drugs: cocaine, amphetamines etc? Does smoking anything automatically put one at risk of those cancers usually associated with tobacco use, no matter what the smoked substance is? Also, just as a matter of interest, does anyone know why smoking certain drugs (tobacco, opium, heroin, crack, ice, angel dust etc) is even possible? I’d assume the intense heat from the combustion process would destroy the complex (and presumably fragile) molecules that are responsible for most psychoactive (ie mind-altering) substances’ actions.
Those are difficult questions to answer definitively. According to some reports from the medical journals, there is evidence that, yes, the drugs you mention have been found to be associated with elevated risk of cancer. This is supported by multiple studies.
You might want to check the medical journals, and specifically the epidemiology journals, for some answers and you can make up your own mind. Many results of studies are available in the abstracts in PubMed. One citation of note is Fligiel et al. Tracheobronchial histopathology in habitual smokers of cocaine, marijuana, and/or tobacco. Chest 1997; 112:319-326. This study showed more frequent histopath abnormalities like hyperplasia and squamous cell metaplasia in lungs of marijuana smokers and crack cocaine smokers than in the lungs of non-smokers. They also found that the frequency of histopath abnormalities was nearly the same in tobacco smokers and marijuana smokers. Subjects that smoked tobacco+marijuana or tobacco+cocaine had an even higher frequency of histopath abnormalities, suggesting a cumulative effect.
You may be aware that marijuana may contain benzo-alpha-pyrene at concentrations as high as tobacco cigarettes. This is a known carcinogen. There is evidence that smoking may lead to persistent genetic abnormalities such as the loss of chromosomal regions such as tumor-suppressing genes. Cite: Mao et al. Clonal genetic alterations in the lungs of current and former smokers. J National Cancer Inst 1997; 89:857-862. That means that, even if you quit, you may have chromosomal damage that can promote cancer.
One thing that makes measuring cancer risk difficult among drug users is that drug use may be associated with lifestyle and environmental factors that also may elevate cancer risk. That’s a weakness in epidemiology studies and so one must consider that while reading the discussions and results.
IANAChemist so I can’t answer your question about combustion except remember that combustion is just a chemical process. I may also point out that inhaling particulates is an effective drug delivery system. If THC is in the lungs, the alveoli can absorb large amounts and deliver it into the blood stream.
Pretty much, smoking anything is going to up your cancer risk. Lung cancer, mouth cancer, throat cancer…
Esophageal, stomach, and liver cancer are associated with alcoholism
IV drugs themselves may cause liver damage, but beyond that, injection with less than santiary needles can lead to hepatitis - some varieties of which are a major risk factor for liver cancer
Some of the chemicals used for processing drugs (such as cocaine into crack) or cooking them up (like methamphetamines) can cause cancer with extended exposure.
“Huffing” agents (inahlants) may be cancer risks in addition to outright poisons and toxins. I suspect most heavy users die of the neurotoxic or liver/kidney effects before the cancer kicks in.
Beyond that, there just haven’t been many studies done of the effects of illegal drugs on people in regards to cancer risk.
With smoking, I believe that the combustion does destroy a fair amount of the active ingredient. But you’re not only breathing in the smoke from the burnt material - the heat also causes volatile substances to be released from nearby, which get swept into your lungs with the smoke.