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Smoking Permanently Damages Your DNA, Study Finds (nbcnews.com)
An anonymous reader quotes a report from NBC News: Smoking scars DNA in clear patterns, researchers reported Tuesday. Most of the damage fades over time, they found -- but not all of it. Their study of 16,000 people found that while most of the disease-causing genetic footprints left by smoking fade after five years if people quit, some appear to stay there forever. The marks are made in a process called methylation, which is an alteration of DNA that can inactivate a gene or change how it functions -- often causing cancer and other diseases. The team examined blood samples given by 16,000 people taking part in various studies going back to 1971. In all the studies, people have given blood samples and filled out questionnaires about smoking, diet, lifestyle and their health histories. They found smokers had a pattern of methylation changes affecting more than 7,000 genes, or one-third of known human genes. Many of the genes had known links to heart disease and cancers known to be caused by smoking. Among quitters, most of these changes reverted to the patterns seen in people who never smoked after about five years, the team reported in the American Heart Association journal Circulation: Cardiovascular Genetics. But smoking-related changes in 19 genes, including the TIAM2 gene linked to lymphoma, lasted 30 years, the team found.
The cytosine methylation signal along a strand of DNA is theoretically heritable, even though it has nothing to do with the actual sequence of bases.
There are vast stretches of junk DNA in the genome, some with old genes for ancient viruses or parasitic sequences like transposons, and the way the cell keeps those parts of DNA away from cell machinery is by methylating the cytosine residues. The methyl groups prevent RNA polymerase from transcribing the DNA and therefore it gets silenced.
When a cell divides, the methyl groups are only on the original strand; the new complimentary strand doesn't have any. The methylation signal has to be actively transcribed from one strand to another; an enzyme runs up the DNA feeling for methylated cytosine residues. When it finds some, it starts methylating any cytosine residues that might be nearby on the opposite strand, to make sure the troublesome regions all stay commented out. That's why it's heritable.
When a cell divides, the methyl groups are only on the original strand; the new complimentary strand doesn't have any. The methylation signal has to be actively transcribed from one strand to another; an enzyme runs up the DNA feeling for methylated cytosine residues. When it finds some, it starts methylating any cytosine residues that might be nearby on the opposite strand, to make sure the troublesome regions all stay commented out. That's why it's heritable.
The methylation inactivation is heritable. The issue, in this case, was erroneous activation or switching of cells to modify protein production.
I suspect that the mechanism involved (they don't say) in the repair of the genes which end up going back to normal is related to the production of O6-methyl-transferase via the MGMT complex sites on the long arm of c21 -- the same thing that results in chemo-resistance to cancers, such as pancreatic cancer or glioblastoma, when combined with the appropriate mutation of the p53 gene on c17.
I think as long as it doesn't involve a long term mutation of a cancer related gene, such that it effect the germ cells, it's not a problem. Since you tend to come pre-packed with all the germ cells you are ever going to have in your lifetime, then the issue will be smoking by pregnant women, and all other damage that results in disease will only be self-inflicted diseases, rather than heritable.
Which still means they've failed to answer the question of whether or not it's heritable, because they've failed to discuss whether or not it impacts germ cells (arguably unlikely, but it'd be nice to have an answer, particularly when making decisions on how and when to regulate smoking, or minimally, smoking in public).
Obviously it's too early to say exactly how safe vaping is, however we know smoking tobacco is incredibly bad for you and we know most of the ingredients in e-liquids are (relatively) safe on their own.
While there have been studies showing negative effects they tend to be rife with methodological flaws (running the e-cigs while dry, not replacing coils at the point they're burnt out, or using unrealistic dosages). I expect these studies get away with questionable methodology because we know how bad cigarettes are and no body wants to risk giving e-cigarettes a pass. Having said that there are some well designed studies which suggest vaping has it's own risks, there was a study showing the immune system of mice is temporarily suppressed by the vapour which seemed pretty solid (although that isn't my area so I may be wrong).
So while it's a mistake to say that vaping is definitely 95% safer than smoking, whatever that actually means, it's sensible to say it's probably significantly safer.
That is just called annoyance, not health risk. The brief few seconds outdoor smell exposure you are talking about is probably something unmeasurably small, like 0.00000000001% the exposure of actual smoking. Once you walk into the building, you probably are breathing a zillion times more contaminates from paints, perfumes, plastics, carpets, wood preservatives, cleaning products, etc., continuously for many hours, day after day.
It's just an annoyance to you, perhaps, but a life-threatening health issue to me and a subset of people with serious respiratory illnesses like athsma and COPD. My airways constrict when exposed to smoke. Paints, perfumes, plastics, etc. are just fine - I have no problem with them. Smoke for some reason is a trigger and people like me are the reason smokers are exiled to the great outdoors. You're welcome.