View source for Cigarette filter

{{Short description|Filter in cigarettes that reduce nicotine, tar and carbon monoxide}}
{{use dmy dates |date=August 2022}}
[[Image:Cigarettefiltar.jpg|thumb|Filters in a new and used cigarette. Filters were designed to turn brown with use to give the illusion that they were effective at reducing the harmfulness.<ref name=nyt_filter>{{Cite news| issn = 0362-4331| last = Kennedy| first = Pagan| title = Who Made That Cigarette Filter?| work = The New York Times| access-date = 2018-09-04| date = 2012-07-06| url = https://www.nytimes.com/2012/07/08/magazine/who-made-that-cigarette-filter.html}}</ref><ref name=filterprob>{{Cite journal| doi = 10.1136/tc.2010.040113| eissn = 1468-3318| issn = 0964-4563| volume = 20| issue = Suppl 1| pages = –10–i16| last = Harris| first = Bradford| title = The intractable cigarette 'filter problem'| journal = Tobacco Control| date = 2011-05-01| pmid = 21504917| pmc = 3088411}}</ref>]]
[[Image:Cigarette diagram.svg|thumb|Components of a filter cigarette: {{ordered list |'''Cigarette filter''' |Imitation cork tip paper |[[Cigarette paper]] |[[Tobacco]]}}]]

A '''cigarette filter''', also known as a '''filter tip''', is a component of a [[cigarette]], along with [[cigarette paper]], capsules and adhesives. Filters were introduced in the early 1950s.<ref name=Monograph13/>

Filters may be made from plastic [[cellulose acetate]] fiber, [[paper]] or [[activated charcoal]] (either as a cavity filter or embedded into the plastic cellulose acetate fibers). Macroporous [[phenol-formaldehyde resin]]s and [[asbestos]] have also been used.<ref>{{citation | author1=Francois de Dardel | author2=Thomas V. Arden | contribution=Ion Exchangers | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–74 | doi=10.1002/14356007.a14_393| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref><ref>{{citation | author=Seymour S. Chissick | contribution=Asbestos | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–18 | doi=10.1002/14356007.a03_151| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref> The plastic cellulose acetate filter and paper modify the particulate smoke phase by particle retention ([[filtration]]), and finely divided [[activated charcoal|carbon]] modifies the gaseous phase ([[adsorption]]).<ref name="tobacco">{{citation | author=T. C. Tso | contribution=Tobacco | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–26 | doi=10.1002/14356007.a27_123| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref>

Filters are intended to reduce the [[Health effects of tobacco|harm caused by smoking]] by reducing harmful elements inhaled by smokers. They have been shown to reduce the risk of lung cancer.<ref>{{cite book |last1=Thomas |first1=N. |last2=Tanner |first2=N.T. |last3=Ward |first3=R. |last4=Rojewski |first4=A. |last5=Gebregziabher |first5=M. |last6=Toll |first6=B. |last7=Silvestri |first7=G.A. |chapter-url=https://doi.org/10.1164/ajrccm-conference.2019.199.1_MeetingAbstracts.A5894 |doi=10.1164/ajrccm-conference.2019.199.1_MeetingAbstracts.A5894 |chapter=Filtered, Unfiltered, Light, Ultralight, Regular or Mentholated: The Effect of Cigarette Type on Lung Cancer Incidence and Mortality in the National Lung Screening Trial |title=D19. Lung Cancer Screening: Novel Insights on Patient Selection and Outcomes |year=2019 |pages=A5894 |s2cid=202823625 }}</ref> While laboratory tests show a reduction of "[[Tar (tobacco residue)|tar]]" and [[nicotine]] smoke, filters are ineffective at removing gases of low molecular weight, such as [[carbon monoxide]].<ref name="etts">{{citation | author=Robert Kapp | contribution=Tobacco Smoke | title=Encyclopedia of Toxicology | edition=2nd | volume=4 | publisher=Elsevier | year=2005 | pages=200–202 | isbn=978-0-12-745354-5}}</ref> Most of these measured reductions{{which|date=December 2022}} occur only when the cigarette is smoked on a smoking machine; when smoked by a human, the compounds are delivered into the lungs regardless of whether or not a filter is used.<ref name="filterprob" />

Most factory-made cigarettes are equipped with a filter; those who roll their own can buy them from a tobacconist.<ref name="filterprob" />

== History ==
In 1925, Hungarian inventor Boris Aivaz patented the process of making a cigarette filter from [[crepe paper]].<ref>{{cite web|url=http://www.tobaccoasia.com/news.asp?id=534|title=The History of Filters|publisher=tobaccoasia.com|access-date=2008-05-18|url-status=dead|archive-url=https://web.archive.org/web/20030824115139/http://www.tobaccoasia.com/news.asp?id=534 |archive-date=August 24, 2003}}</ref>

From 1935, Molins Machine Co Ltd <ref>{{Cite web|url=https://patentimages.storage.googleapis.com/04/20/93/01379c9586c72d/US2156600.pdf|title=Cigarette with Filter tip}}</ref> a British company began to develop a machine that made cigarettes incorporating the tipped filter. It was considered a specialty item until 1954, when manufacturers introduced the machine more broadly, following a spate of speculative announcements from [[physician|doctors]] and researchers concerning a possible link between [[lung diseases]] and smoking. Since filtered cigarettes were considered safer, by the 1960s, they dominated the market. Production of filter cigarettes rose from 0.5 percent in 1950 to 87.7 percent by 1975.<ref>{{citation | editor1=Murray E. Jarvik | editor2=Joseph W. Cullen | editor3=Ellen R. Gritz | editor4=Thomas M. Vogt | editor5=Louis Jolyon West | title=Research on Smoking Behavior | series=NIDA Research Monograph | volume=17 | author=Leonard M. Schuman | contribution=Patterns of Smoking Behavior | pages=36–65 | year=1977 | url=http://archives.drugabuse.gov/pdf/monographs/17.pdf | access-date=2015-10-21 | archive-url=https://web.archive.org/web/20150723034328/http://archives.drugabuse.gov/pdf/monographs/17.pdf | archive-date=2015-07-23 | url-status=dead }}</ref>

Between the 1930s and the 1950s, most cigarettes were {{convert|70|mm|in|frac=4}} long. The modern cigarette market includes mainly filter cigarettes that are {{convert|80|,|85|,|100|, or|120|mm|in|frac=8}}.<ref>{{citation | editor1=John Grabowski | editor2=Catherine S. Bell | author=Lynn T. Kozlowski |contribution=Physical Indicators of Actual Tar and Nicotine Yields of Cigarettes | title=Measurement in the Analysis and Treatment of Smoking Behavior | series=NIDA Research Monograph | volume=48 | year=1983 | publisher=U.S. Dept. of Health and Human Services | pages=50–61 | url=http://archives.drugabuse.gov/pdf/monographs/48.pdf | access-date=2016-03-29 | archive-url=https://web.archive.org/web/20161017002853/http://archives.drugabuse.gov/pdf/monographs/48.pdf | archive-date=2016-10-17 | url-status=dead |pmid=6443144 }}</ref>

Cigarettes filters were originally made of cork and used to prevent tobacco flakes from getting on the smoker's tongue. Many are still patterned to look like cork.<ref name=nyt_filter/>

== Manufacture ==
[[Image:Celluloseacetuar.jpg|thumb|Spent cigarette filter]]
{{quotebox|align=right|width=33%|title=Colour change|quote = 
The cigarette smoking public attaches great significance to visual examination of the filter material in filter tip cigarettes after smoking the cigarettes. A before and after smoking visual comparison is usually made and if the filter tip material, after smoking, is darkened, the tip is automatically judged to be effective. While the use of such colour change material would probably have little or no effect on the actual effectiveness of the filter tip material, the advertising and sales advantages are obvious.
|source= — Claude Teague, the inventor of the colour-changing filter<ref name=filterprob/>}}

Cigarette filters are usually made from plastic [[cellulose acetate]] [[fibre]],<ref name=Monograph13/> but sometimes also from [[paper]] or [[activated charcoal]] (either as a cavity filter or embedded into the cellulose acetate).

[[Cellulose acetate]] is made by [[ester]]ifying [[bleaching|bleached]] [[cotton]] or [[wood pulp]] with [[acetic acid]]. Of the three cellulose hydroxy groups available for esterification, between two and three are esterified by controlling the amount of acid (degree of substitution (DS) 2.35-2.55). The ester is spun into fibers and formed into bundles called [[filter tow]]. Flavors ([[menthol]]), [[sweeteners]], [[Plasticizer|softeners]] ([[triacetin]]), [[flame retardant]]s ([[sodium tungstate]]), breakable capsules releasing flavors on demand, and additives colouring the tobacco smoke may be added to cigarette filters.<ref>{{citation | author1=Ralf Christoph | author2=Bernd Schmidt | author3=Udo Steinberner | author4=Wolfgang Dilla | author5=Reetta Karinen | contribution=Glycerol | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–16 | doi=10.1002/14356007.a12_477.pub2| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref><ref>{{citation | author1=Erik Lassner | author2=Wolf-Dieter Schubert | author3=Eberhard Luderitz | author4=Hans Uwe Wolf | contribution=Tungsten, Tungsten Alloys, and Tungsten Compounds | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–37 | doi=10.1002/14356007.a27_229| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref> The five largest manufactures of filter tow are [[Celanese|Hoechst-Celanese]] and [[Eastman Chemical Company|Eastman Chemicals]] in the United States, Cerdia in Germany, [[Daicel]] and Mitsubishi Rayon in Japan.

[[Starch glue]]s or [[emulsion-based adhesive]]s are used for gluing cigarette seams. [[Hot-melt adhesive|Hot-melt]] and emulsion-based adhesives are used for filter seams. Emulsion-based adhesives are used for bonding the filters to the cigarettes.<ref>{{citation | author1=Werner Haller | author2=Hermann Onusseit | author3=Gerhard Gierenz | author4=Werner Gruber | author5=Richard D. Rich | author6=Günter Henke | author7=Lothar Thiele | author8=Horst Hoffmann | author9=Dieter Dausmann | author10=Riza-Nur Özelli | author11=Udo Windhövel | author12=Hans-Peter Sattler | author13=Wolfgang Dierichs | author14=Günter Tauber | author15=Michael Hirthammer | author16=Christoph Matz | author17=Matthew Holloway | author18=David Melody | author19=Ernst-Ulrich Rust | author20=Ansgar van Halteren | contribution=Adhesives | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | pages=1–70 | doi=10.1002/14356007.a01_221| title-link=Ullmann's Encyclopedia of Industrial Chemistry | isbn=978-3527306732 }}</ref> The tip paper may be coated with [[polyvinyl alcohol]].<ref>{{citation | author=F. L. Marten | contribution=Vinyl Alcohol Polymers | title=Kirk-Othmer Encyclopedia of Chemical Technology | edition=5th | publisher=Wiley | year=2002 | page=26 | doi= 10.1002/0471238961.2209142513011820.a01.pub2| isbn=0471238961 }}</ref>

=== Colour change ===

The tobacco industry determined that the illusion of filtration was more important than filtration itself. It added chemicals in the filter so that its colour becomes darker when exposed to smoke (it was invented in 1953 by Claude Teague working for [[R. J. Reynolds Tobacco Company]]).<ref name=Proctor>{{Cite book |author=Robert N. Proctor |author-link=Robert N. Proctor |title=Golden Holocaust: Origins of the Cigarette Catastrophe and the Case for Abolition |publisher=[[University of California Press]] |location=Berkeley |year=2012 |isbn=9780520270169}}</ref> The industry wanted filters to be seen as effective, for marketing reasons, despite not making [[health effects of tobacco|cigarettes any less unhealthy]].<ref name=Monograph13>{{cite report |work=[[National Cancer Institute]] |url=https://cancercontrol.cancer.gov/brp/tcrb/monographs/monograph-13 |title=Monograph 13: Risks associated with smoking cigarettes with low tar machine-measured yields of tar and nicotine |publisher=[[United States Department of Health and Human Services]] |year=2001 }}</ref>{{Failed verification|date=April 2021}}

== Health risks ==
{{Main|Health effects of tobacco}}
{{more medical citations needed|reason=out-of-date sources, does not reflect the balance of evidence|date=September 2018}}

In the 1970s epidemiologic evidence relative to tobacco-related cancers and data for coronary heart disease indicated a reduced risk among filter smokers for these diseases.<ref>{{citation | editor1=Murray E. Jarvik | editor2=Joseph W. Cullen | editor3=Ellen R. Gritz | editor4=Thomas M. Vogt | editor5=Louis Jolyon West | title=Research on Smoking Behavior | series=NIDA Research Monograph | volume=17 | author=Ernst L. Wynder | contribution=Interrelationship of Smoking to Other Variables and Preventive Approaches | pages=67–95 | year=1977 | issue=17 | url=http://archives.drugabuse.gov/pdf/monographs/17.pdf | access-date=2015-10-21 | archive-url=https://web.archive.org/web/20150723034328/http://archives.drugabuse.gov/pdf/monographs/17.pdf | archive-date=2015-07-23 | url-status=dead |pmid=417264 }}</ref> Between 1970 and 1980 some studies showed a 20-50% reduction in risk of lung cancer for long-term smokers of filtered cigarettes as compared to smokers of non-filtered cigarettes (IARC, 1986) but later studies indicated a similar risk for lung cancer in smokers of filtered and non-filtered cigarettes.<ref name="ehc">{{citation | author=K. Rothwell | title=Health effects of interactions between tobacco use and exposure to other agents | series=[[Environmental Health Criteria]] | issue=211 | publisher=[[World Health Organization]] | year=1999 | url=http://www.inchem.org/documents/ehc/ehc/ehc211.htm|display-authors=etal}}</ref>  The risk reductions depend on different aspects such as the gender or whether a person is athletic, the study location, the age of the person, and when only studies providing both unadjusted and adjusted estimates were considered. Whether or not relative risk estimates are adjusted for cigarette consumption is not crucial to the conclusion of a clear advantage to filter cigarettes and tar reduction.<ref>{{Cite journal |last1=Lee |first1=Peter N. |last2=Sanders |first2=Edward |date=2004-12-01 |title=Does increased cigarette consumption nullify any reduction in lung cancer risk associated with low-tar filter cigarettes? |url=https://pubmed.ncbi.nlm.nih.gov/15513814/ |journal=Inhalation Toxicology |volume=16 |issue=13 |pages=817–833 |doi=10.1080/08958370490490185 |issn=0895-8378 |pmid=15513814|s2cid=22468291 }}</ref>

Various add-on cigarette filters ("Water Pik", "Venturi", "David Ross") are sold as stop-smoking or tar-reduction devices. The idea is that filters reduce tar and nicotine levels, permitting the smoker to be weaned away from cigarettes.<ref>{{citation | editor1=Murray E. Jarvik | editor2=Joseph W. Cullen | editor3=Ellen R. Gritz | editor4=Thomas M. Vogt | editor5=Louis Jolyon West | title=Research on Smoking Behavior | series=NIDA Research Monograph | volume=17 | author=Jerome L. Schwartz | contribution=Smoking Cures: Ways to Kick an Unhealthy Habit | pages=308–336 | year=1977 | url=http://archives.drugabuse.gov/pdf/monographs/17.pdf | access-date=2015-10-21 | archive-url=https://web.archive.org/web/20150723034328/http://archives.drugabuse.gov/pdf/monographs/17.pdf | archive-date=2015-07-23 | url-status=dead }}</ref>

=== Light cigarettes ===
{{Main|Ventilated cigarette}}

The tobacco industry has reduced tar and nicotine yields in cigarette smoke since the 1960s. This has been achieved in a variety of ways, including use of selected strains of tobacco plant, changes in agricultural and curing procedures, use of reconstituted sheets (reprocessed tobacco leaf waste), incorporation of tobacco stalks, reduction of the amount of tobacco needed to fill a cigarette by expanding it (like puffed wheat) to increase its "filling power", and by the use of filters and high-porosity wrapping papers. However, just as a drinker tends to drink a larger volume of beer than of wine or spirits, many smokers tend to inversely modify their smoking pattern according to the strength of the cigarette being smoked. In contrast to the standardized puffing of the smoking machines on which the tar and nicotine yields are based, when a smoker switches to a low-tar, low nicotine cigarette, they smoke more cigarettes, take more puffs and inhale more deeply. Conversely, when smoking a high-tar, high-nicotine cigarette there is a tendency to smoke and inhale less.<ref>{{citation | editor1=Murray E. Jarvik | editor2=Joseph W. Cullen | editor3=Ellen R. Gritz | editor4=Thomas M. Vogt | editor5=Louis Jolyon West | title=Research on Smoking Behavior | series=NIDA Research Monograph | volume=17 | author=Michael A. H. Russell | contribution=Smoking Problems: An Overview | pages=13–34 | year=1977 | url=http://archives.drugabuse.gov/pdf/monographs/17.pdf | access-date=2015-10-21 | archive-url=https://web.archive.org/web/20150723034328/http://archives.drugabuse.gov/pdf/monographs/17.pdf | archive-date=2015-07-23 | url-status=dead }}</ref>

In spite of the changes in cigarette design and manufacturing over the last fifty years, the use of filters and "light" cigarettes neither decreased the nicotine intake per cigarette, nor lowered the incidence of lung cancer ([[National Cancer Institute|NCI]], 2001; IARC 83, 2004; U.S. Surgeon General, 2004).<ref name="epidem">{{citation | editor1=Robert J. Mason | editor2=V. Courtney Broaddus | editor3=Thomas R. Martin | editor4=Talmadge E. King, Jr. | editor5=Dean E. Schraufnagel | editor6=John F. Murray | editor7=Jay A. Nadel | title=Murray and Nadel's Textbook of Respiratory Medicine | author1=Anthony J. Alberg | author2=Jonathan M. Samet | chapter=Epidemiology of Lung Cancer | volume=1 | edition=5th | year=2010 | publisher=Saunders | isbn=978-1-4160-4710-0}}</ref> The shift over the years from higher- to lower-yield cigarettes may explain the change in the pathology of [[lung cancer]]. That is, the percentage of lung cancers that are [[adenocarcinoma]]s has increased, while the percentage of [[squamous cell cancer]]s has decreased. The change in tumor type is believed to reflect the higher [[tobacco-specific nitrosamines|nitrosamine]] delivery of lower-yield cigarettes and the increased depth or volume of inhalation of lower-yield cigarettes to compensate for lower level concentrations of nicotine in the smoke.<ref>{{citation | editor1=Robert J. Mason | editor2=V. Courtney Broaddus | editor3=Thomas R. Martin | editor4=Talmadge E. King, Jr. | editor5=Dean E. Schraufnagel | editor6=John F. Murray | editor7=Jay A. Nadel | title=Murray and Nadel's Textbook of Respiratory Medicine | author1=Neal L. Benowitz | author2=Paul G. Brunetta | chapter=Smoking Hazards and Cessation | volume=1 | edition=5th | year=2010 | publisher=Saunders | isbn=978-1-4160-4710-0}}</ref>

== Safety ==
[[File:Cellulose Acetate.png|thumb|[[Structure formula]] of [[cellulose diacetate]] with one of the acetate groups on the cellulose backbone shown by the red circle.]]

Cellulose acetate is non-toxic, odorless, tasteless, and weakly flammable plastic. It is resistant to weak acids and is largely stable to mineral and fatty oils as well as petroleum. Smoked (i.e., used/discarded) cigarette butts contain 5–7&nbsp;mg (~ 0.08-0.11 gr) of [[nicotine]] (about 25% of the total cigarette nicotine content). Cellulose acetate is hydrophilic and retains the water-soluble smoke constituents (many of which are irritating, including acids, alkali, aldehydes, and phenols), while letting through the lipophilic aromatic compounds.

== Waste==
[[File:CigMacroLitter.JPG|thumb|A cigarette butt littered on the ground]]
{{See also|Plastic pollution|Marine pollution#Plastic debris}}

Cigarette butts are the most littered anthropogenic (man-made) [[litter|waste item]] in the world. Approximately 5.6 trillion cigarettes are smoked every year worldwide.<ref name=IJERPH>{{Cite journal |vauthors=Novotny TE, Lum K, Smith E |title=Cigarettes butts and the case for an environmental policy on hazardous cigarette waste |journal=International Journal of Environmental Research and Public Health |volume=6 |issue=5 |pages=1691–705 |date=2009 |display-authors=etal |doi=10.3390/ijerph6051691|pmid=19543415 |pmc=2697937 |doi-access=free }}</ref> Of these, it is estimated that 4.5 trillion cigarette butts become litter every year.<ref>{{cite web|url=http://blog.chron.com/sciguy/2010/05/the-world-litters-4-5-trillion-cigarette-butts-a-year-can-we-stop-this/|title=The world litters 4.5 trillion cigarette butts a year. Can we stop this?|publisher=[[The Houston Chronicle]]|access-date=2014-09-16|date=2010-05-12}}</ref> The plastic [[cellulose acetate]] in cigarette butts biodegrade gradually, passing through the stage of [[microplastics]].<ref>{{cite web |url=https://www.treehugger.com/are-cigarette-butts-biodegradable-1204105 |title=Are Cigarette Butts Biodegradable?|author= Frederic Beaudry |date=3 July 2019 |work=treehugger.com |access-date=31 August 2022 }}</ref> The breakdown of discarded cigarette butts is highly dependent upon environmental conditions. A 2021 review article cites an experiment where 45-50% of cellulose acetate mass was fully degraded to CO<sub>2</sub> after 55 days of controlled composting and another where negligible degradation took place after 12 weeks in pilot-scale compost.<ref>{{cite journal |title=Degradable or not? Cellulose acetate as a model for complicated interplay between structure, environment and degradation |last1=Yadav |first1=Nisha |last2=Hakkarainen |first2=Minna |year = 2021 |journal=Chemosphere|volume = 265 |page=128731 |doi = 10.1016/j.chemosphere.2020.128731 |pmid=33127118 |bibcode=2021Chmsp.265l8731Y |doi-access=free}}</ref><ref>{{cite web|title=New 'Green' Cigarette Butts Biodegrade Within Days—And Can Even Sprout Into Grass - The company Greenbutts is manufacturing a new filter to address most common litter problem.| url=https://www.alternet.org/2014/02/new-green-cigarette-butts-biodegrade-within-days-and-can-even-sprout-grass/ |date=February 12, 2014 |first=Aaron |last=Cantú |work=[[AlterNet]] }}</ref><ref>{{cite journal |title=Degradation Rates of Plastics in the Environment|last1=Chamas |first1=Ali |year = 2020 |journal=ACS Sustainable Chemistry & Engineering |volume=8 |issue=9 |pages=3494–3511 |doi=10.1021/acssuschemeng.9b06635 |doi-access = free}}</ref>

During the act of smoking, plastic cellulose acetate fibers and tipping paper absorb a wide range of chemicals that are present in tobacco smoke. After cigarette butts are discarded, they can leach toxins including nicotine, arsenic, polycyclic aromatic hydrocarbons and heavy metals into the environment.<ref>{{Cite journal|last1=Moriwaki|first1=Hiroshi|last2=Kitajima|first2=Shiori|last3=Katahira|first3=Kenshi|date=2009|title=Waste on the roadside, 'poi-sute' waste: Its distribution and elution potential of pollutants into environment|url=https://linkinghub.elsevier.com/retrieve/pii/S0956053X08002882|journal=Waste Management|language=en|volume=29|issue=3|pages=1192–1197|doi=10.1016/j.wasman.2008.08.017|pmid=18851907|hdl=10091/3192|hdl-access=free}}</ref> Smoked cigarette butts and cigarette tobacco in butts have been shown to be toxic to water organisms such as the [[marine topsmelt]] (''[[Atherinops affinis]]'') and the freshwater [[fathead minnow]] (''[[Pimephales promelas]]'').<ref>{{Cite journal|vauthors=Slaughter E, Gersberg RM, Watanabe K, Rudolph J, Stransky C, Novotny TE|date=2011|title=Toxicity of cigarette butts, and their chemical components, to marine and freshwater fish|journal=Tobacco Control|volume=20|issue=Suppl_1|pages=25–29|doi=10.1136/tc.2010.040170|pmc=3088407|pmid=21504921}}</ref>

Atmospheric moisture, [[gastric acid]], light, and [[enzyme]]s [[hydrolysis|hydrolyze]] cellulose acetate to [[acetic acid]] and [[cellulose]]. Cellulose may be further hydrolyzed to [[cellobiose]] or [[glucose]] in an acidic medium. Humans cannot digest cellulose and excrete the fibers in feces, because, unlike ruminant animals, [[rabbit]]s, [[rodent]]s, [[termite]]s, and some bacteria and fungi, they lack cellulolytic enzymes such as [[cellulase]].{{citation needed|date=March 2019}}
[[File:Ashtray full of Cigarette butts.png|alt=Ashtray full of Cigarette butts|thumb|Ashtray full of cigarette butts]]
Many governments have sanctioned stiff penalties for littering of cigarette filters; for example [[Washington (state)|Washington]] State imposes a penalty of $1,025 for littering cigarette filters.<ref>{{cite web
| date = 2004-06-01
| url = http://listserv.wa.gov/cgi-bin/wa?A2=ind0406A&L=ecology-news&F=&S=&P=643
| publisher = State of Washington Department of Ecology
| location = Washington
| title = Accidents, fires: Price of littering goes beyond fines
| access-date = 2016-09-19
| archive-url = https://web.archive.org/web/20161017024347/http://listserv.wa.gov/cgi-bin/wa?A2=ind0406A&L=ecology-news&F=&S=&P=643
| archive-date = 2016-10-17
| url-status = dead
}}</ref> Another option is developing better [[biodegradable]] filters. Much of this work relies heavily on the research about the secondary mechanism for photodegradation. However, making a product biodegradable means making it vulnerable to humidity and heat, which does not suit filters made for hot and humid smoke.<ref name=Proctor/> The next option is using cigarette packs with a compartment for discarded cigarette butts, implementing monetary deposits on filters, increasing the availability of [[cigarette receptacle]]s, and expanding public education. It may even be possible to ban the sale of filtered cigarettes altogether on the basis of their adverse environmental impact.<ref name=IJERPH/>

Recent research has been put into finding ways to use the filter waste in order to develop other products. One research group in South Korea have developed a one-step process that converts the cellulose acetate in discarded cigarette filters into a high-performing material that could be integrated into computers, handheld devices, electrical vehicle and wind turbines to store energy. These materials have demonstrated superior performance as compared to commercially available carbon, [[graphene]] and [[carbon nano tube]]s.<ref>{{Cite journal |vauthors=Minzae L, Gil-Pyo K, Hyeon DS, Soomin P, Jongheop Y |title=Preparation of energy storage material derived from a used cigarette filter for a supercapacitor electrode |journal= Nanotechnology|volume=25 |issue=34 |pages=34 |date=2014 |doi=10.1088/0957-4484/25/34/345601 |pmid=25092115 |bibcode=2014Nanot..25H5601L |s2cid=8692351 }}</ref> Another group of researchers has proposed adding tablets of food grade acid inside the filters. Once wet enough the tablets will release acid that accelerates degradation to around two weeks instead of using cellulose triacetate and besides of cigarette smoke being quite acidic.<ref>{{Cite web|date = 2012-08-14|url = http://www.environmentalhealthnews.org/ehs/newscience/2012/06/2012-0725-biodegradable-cigarette-filters|publisher = Environmental Health News|title = No more butts: biodegradable filters a step to boot litter problem}}</ref>

== See also ==
* [[Cigarette#Cigarette butt|Cigarette butt]]
* [[Cigarette holder]]
* [[List of additives in cigarettes]]
* [[Nicotine marketing]]
* [[Tobacco smoking]]

== References ==
{{Reflist|30em}}

{{Cigarettes}}

[[Category:Cigarettes]]
[[Category:Air filters]]
[[Category:Nicotine products with harm-reduction claims]]