Editing Cigarette (section)

=== Photodegradation ===
The other process of degradation is [[photodegradation]], which is when a molecular bond is broken by the absorption of photon radiation (i.e. light). Due to cellulose acetate carbonyl groups, the molecule naturally absorbs light at 260&nbsp;nm,<ref>{{Cite journal |author=Hon NS |title=Photodegradation of Cellulose Acetate Fibers |journal=Journal of Polymer Science Part A: Polymer Chemistry |volume=15 |issue=3 |pages=725–744 |date=1977 |doi=10.1002/pol.1977.170150319|bibcode=1977JPoSA..15..725H }}</ref> but it contains some impurities which can absorb light. These impurities are known to absorb light in the far UV light region (< 280&nbsp;nm).<ref>{{Cite journal |vauthors=Hosono K, Kanazawa A, Mori H, Endo T |title=Photodegradation of Cellulose Acetate film in the presence of bensophenone as a photosensitizer |journal=Journal of Applied Polymer Science |volume=105 |issue=6 |pages=3235–3239 |date=2007 |doi=10.1002/app.26386|doi-access=free }}</ref> The atmosphere filters radiation from the sun and allows radiation of > 300&nbsp;nm only to reach the surface. Thus, the primary photodegradation of cellulose acetate is considered insignificant to the total degradation process, since cellulose acetate and its impurities absorb light at shorter wavelengths. Research is focused on the secondary mechanisms of photodegradation of cellulose acetate to help make up for some of the limitations of biodegradation. The secondary mechanisms would be the addition of a compound to the filters that would be able to absorb natural light and use it to start the degradation process. The main two areas of research are in photocatalytic oxidation<ref>{{cite web |url=http://allergyclean.com/news/uvpcoformaldehyde.htm |title=Study on Photocatalytic Oxidation (PCO) Raises Questions About Formaldehyde as a Byproduct in Indoor Air |access-date=May 30, 2015 |archive-url=https://web.archive.org/web/20150426065810/http://allergyclean.com/news/uvpcoformaldehyde.htm |archive-date=April 26, 2015 }}</ref> and photosensitized degradation.<ref>{{cite encyclopedia|url=https://www.britannica.com/EBchecked/topic/458153/photosensitization|title=photosensitization - chemistry|encyclopedia=Encyclopædia Britannica|access-date=May 30, 2015}}</ref> Photocatalytic oxidation uses a species that absorbs radiation and creates hydroxyl radicals that react with the filters and start the breakdown. Photosensitized degradation, though, uses a species that absorbs radiation and transfers the energy to the cellulose acetate to start the degradation process. Both processes use other species that absorbed light > 300&nbsp;nm to start the degradation of cellulose acetate.{{citation needed|date=December 2014}}