What is the difference between the smoke coming out of the front of the cigarette and the smoke coming out of the back?
In: 9
A full ELI-PhD article that touches on this question can be found at https://www.ncbi.nlm.nih.gov/books/NBK53014/
Here’s my attempt to ELI5 it 😛
“Sidestream” smoke is what comes out the front, “mainstream” smoke is what you suck out the back.
* Chemicals with a lower boiling point are more likely to be found in the sidestream vs. chemicals with higher boiling point being more likely to be found in the mainstream smoke.
* Sidestream smoke has relatively more
[acetic acid](https://www.gov.uk/government/publications/acetic-acid-properties-uses-and-incident-management/acetic-acid-general-information) (a.k.a vinegar),
[acrolein](https://www.nj.gov/health/eoh/rtkweb/documents/fs/0021.pdf),
[ammonia](https://www.health.ny.gov/environmental/emergency/chemical_terrorism/ammonia_tech.htm),
[aromatic amines](https://www.sciencedirect.com/topics/chemistry/aromatic-amine),
[aza-arenes](https://pubmed.ncbi.nlm.nih.gov/6744247/),
[benzene](https://www.cancer.org/cancer/cancer-causes/benzene.html),
[1,3-butadiene](https://www.epa.gov/sites/default/files/2016-08/documents/13-butadiene.pdf),
[carbon monoxide](https://www.mayoclinic.org/diseases-conditions/carbon-monoxide/symptoms-causes/syc-20370642),
[cresol](https://www.epa.gov/sites/default/files/2016-09/documents/cresol-cresylic-acid.pdf),
[formic acid](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/769719/Formic_acid_PHE_GI_070119.pdf),
[guiacol](https://pubchem.ncbi.nlm.nih.gov/compound/Guaiacol),
[isoprene](https://en.wikipedia.org/wiki/Isoprene),
[nicotine](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4363846/),
[nitrosamines](https://pubs.acs.org/doi/10.1021/acs.est.5b01620),
[PAHs](https://respiratory-research.biomedcentral.com/articles/10.1186/s12931-020-01563-1),
[phenol](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/500822/Phenol_PHE_TO_120216.pdf),
[pyridine](https://nj.gov/health/eoh/rtkweb/documents/fs/1624.pdf),
[toluene](https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=157&toxid=29), and
[xylenols](https://nj.gov/health/eoh/rtkweb/documents/fs/2015.pdf). These are still in mainstream smoke, too, just proportionally less.
* Mainstream smoke has more [catechol](https://www.nwmissouri.edu/naturalsciences/sds/c/Catechol.pdf) and [hydroquinone](https://nj.gov/health/eoh/rtkweb/documents/fs/1019.pdf). These are still in sidestream smoke, too, just proportionally less.
Reasons for the difference are
* temperature (smouldering at about 400°C or puffing at about 900°C)
* which parts of the cigarette burn (smouldering burns the middle more, puffing burns the edges more) There are various reasons why the tobacco is different in different parts of the cigarette, to do with construction and storage.
* oxygen levels (lower in smouldering vs. puffing – this is why the temperature goes up)
* alkalinity (higher in smouldering vs. puffing, mostly due to the ammonia)
* humidity (higher in smouldering vs. puffing)
There are [over 7000 chemicals to be found in cigarette smoke, over 250 of them known to be harmful](https://www.cancer.gov/about-cancer/causes-prevention/risk/tobacco/cessation-fact-sheet)
I was surprised to see that sidestream smoke seems to be worse than mainstream smoke by quite a margin, meaning that the effects on those around the smoker are worse than would otherwise be the case 🙁
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