{{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.<ref name=nyt_filter>{{Cite news| issn = 0362-4331| last = Kennedy| first = Pagan| title = Who Made That Cigarette Filter?| work = The New York Times |url=https://www.nytimes.com/2012/07/08/magazine/who-made-that-cigarette-filter.html |access-date=24 October 2024 |date=2012-07-08 |archive-url=https://web.archive.org/web/20180314202327/https://www.nytimes.com/2012/07/08/magazine/who-made-that-cigarette-filter.html |archive-date=14 March 2018}}</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 tobacco, cigarette paper, capsules and adhesives. Modern 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).<ref>{{Cite web |title=Construction of cigarettes and cigarette filters |url=https://stacks.cdc.gov/view/cdc/45938/cdc_45938_DS1.pdf |access-date=2025-12-31}}</ref> Macroporous phenol-formaldehyde resins 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=978-3-527-30673-2 }}</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=978-3-527-30673-2 }}</ref> The plastic cellulose acetate filter and paper modify the particulate smoke phase by particle retention (filtration), and finely divided 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=978-3-527-30673-2 }}</ref>
Filters are intended to reduce the harm caused by smoking by reducing harmful chemicals inhaled by smokers. While laboratory tests show a reduction of tar and nicotine in cigarette 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 a filter is used.<ref name="filterprob" /><ref name=":0">{{Cite web |title=Risks Associated with Smoking Cigarettes with Low Machine Measured Yields of Tar and Nicotine |url=https://cancercontrol.cancer.gov/sites/default/files/2020-06/m13_complete.pdf |access-date=2026-05-22}}</ref>
Most factory-made cigarettes are equipped with a filter; users who roll their own can buy them from a tobacconist.<ref name="filterprob" />
In North America, the common name for the remains of a cigarette after smoking is a ''cigarette butt''. In Britain, it is also called a ''dog-end'' or a ''fag end''.<ref>The Nelson Contemporary English Dictionary - Page 187, W. T. Cunningham - 1977</ref><ref>{{Cite web |url=https://www.lamontagne.fr/gueret-23000/actualites/litting-cigarette-butts-beware-the-fine_11613266 |title=Littering cigarette butts: beware the fine! |work=La Montagne |date=2015-10-07 |access-date=2025-11-23}}</ref>
== 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|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 announcements from doctors and researchers concerning a possible link between lung diseases and smoking. Since filtered cigarettes were considered safer,<ref name=":0" /> 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 }}</ref>
Between the 1930s and the 1950s, most cigarettes were {{convert|70|mm|in|frac=4}} long. In the 1980s, many were {{convert|80|,|85|,|100|, or|120|mm|in|frac=8}} long.<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 |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 == thumb|Spent cigarette filter|alt=Spent cigarette filter Cigarette filters are usually made from plastic cellulose acetate fibre,<ref name=Monograph13/> but sometimes also from paper<ref>{{Cite web |title=Construction of cigarettes and cigarette filters |url=https://www.tobaccoinaustralia.org.au/chapter-12-tobacco-products/12-8-construction-of-cigarettes-and-cigarette-filters |access-date=2025-12-31}}</ref> or activated charcoal (either as a cavity filter or embedded into the cellulose acetate).<ref>{{Cite web |title=Cigarette Filters |url=https://lake.wateratlas.usf.edu/upload/documents/Cigarette%20Filters.pdf |access-date=2025-12-31}}</ref> Glycerol triacetate may be used as a softener.<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=978-3-527-30673-2 }}</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=0-471-23896-1 }}</ref>
=== Colour change === The tobacco industry determined that the illusion of filtration was more important than filtration itself. The pH of the cellulose acetate used is modified, so that its colour becomes darker when exposed to smoke (this was invented in 1953 by Claude Teague,<ref name=nyt_filter/> 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=978-0-520-27016-9}}</ref> The industry wanted filters to be seen as effective for marketing reasons, despite not making smoking 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> Teague said that:
{{blockquote|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.<ref name=filterprob/>}}
== Health risks == {{Main|Health effects of tobacco}}Public-health researchers have argued that cellulose acetate cigarette filters do not protect people who smoke from smoking-related harms and function primarily as a marketing tool.<ref>{{Cite web |title=Cellulose acetate cigarette filter is hazardous to human health |url=https://tobaccocontrol.bmj.com/content/tobaccocontrol/33/5/663.full.pdf |access-date=2026-05-22}}</ref>
In 2025, UK researchers publicly urged a ban on cigarette filters, arguing that filters do not reduce toxicant exposure and contribute to plastic pollution.<ref>{{Cite news |last=Gayle |first=Damien |last2= |first2= |date=2025-10-16 |title=Experts urge UK to ban cigarette filters to protect health and environment |url=https://www.theguardian.com/environment/2025/oct/16/experts-urge-uk-to-ban-cigarette-filters-to-protect-health-and-environment |access-date=2026-05-21 |work=The Guardian |language=en-GB |issn=0261-3077}}</ref>[[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]]
== Waste== thumb|A cigarette butt littered on the ground|alt=A cigarette butt littered on the ground {{See also|Plastic pollution|Marine pollution#Plastic debris}}
Cigarette butts are the most littered anthropogenic (man-made) 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 biodegrades 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 |article-number=128731 |doi = 10.1016/j.chemosphere.2020.128731 |pmid=33127118 |bibcode=2021Chmsp.26528731Y |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> Peer-reviewed studies have quantified microfiber shedding from cigarette filters in water over time, reporting average releases of ~5.78–92.43 microfiber items per gram of filter after 1–60 days, and estimating that cigarette filters may release tens of trillions of microfibers annually into aquatic environments.<ref>{{Cite web |title=Cigarette filters as a major source of microfibers in aquatic environments |url=https://www.nature.com/articles/s41598-025-20771-7.pdf}}</ref> A 2025 laboratory study reported that cigarette butts in water can shed cellulose acetate microfibers immediately upon immersion and continue shedding over time; the authors quantified release under different agitation conditions over 10 days.<ref>{{Cite journal |last=Vasseghi |first=Ghazal |last2=Atkinson |first2=John D. |date=2026-02-01 |title=Cellulose acetate microfiber release from cigarette filters in agitated water |url=https://www.sciencedirect.com/science/article/pii/S3051060025000368 |journal=Journal of Hazardous Materials: Plastics |volume=2 |article-number=100036 |doi=10.1016/j.hazmp.2025.100036 |issn=3051-0600|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.<ref>{{Cite web |title=Measuring Airborne Emissions from Cigarette Butts: Literature Review and Experimental Plan |url=https://nvlpubs.nist.gov/nistpubs/ir/2016/NIST.IR.8147.pdf |access-date=2026-05-22}}</ref> 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|bibcode=2009WaMan..29.1192M |hdl=10091/3192|hdl-access=free|url-access=subscription}}</ref><ref>{{Cite journal |last=Dolar |first=Andraž |last2=Mušič |first2=Branka |last3=Skalar |first3=Tina |last4=Marolt |first4=Gregor |last5=Drobne |first5=Damjana |last6=Škapin |first6=Andrijana Sever |last7=Jemec Kokalj |first7=Anita |date=2025-06-01 |title=Microplastics from cigarette filters: Comparative effects on selected terrestrial and aquatic invertebrates |url=https://www.sciencedirect.com/science/article/pii/S026974912500572X |journal=Environmental Pollution |volume=374 |article-number=126199 |doi=10.1016/j.envpol.2025.126199 |issn=0269-7491|doi-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> Moreover, cigarette filters enriched in toxic substances that enter environmental waterbodies have been shown to be increasingly colonized by potentially pathogenic bacteria including those displaying antibiotic resistance, as these are particularly well adapted to the adverse conditions on the filters.<ref>{{Cite journal|vauthors=Fang P, Konyali D, Fischer E, Mayer RP, Huang J, Elena AX, Orzechowski GH, Tony-Odigie A, Kneis D, Dalpke A, Krebs P, Li B, Berendonk TU, Klümper U|date=2025|title=Effects of cigarette-derived compounds on the spread of antimicrobial resistance in artificial human lung sputum medium, simulated environmental media and wastewater|journal=Environmental Health Perspectives|volume=133 |issue=3–4 |page=047003 |doi=10.1289/EHP14704|doi-access=free|pmid=40032488 |pmc=11980918 |bibcode=2025EnvHP.133d7003F }}</ref> Research indicates that switching to paper filters alone would not reduce coastal filter pollution.<ref>{{Cite journal |last=Ward |first=Collin P. |last2=Reddy |first2=Christopher M. |last3=James |first3=Bryan D. |date=2025-06-23 |title=Initial estimates of the lifetime of unsmoked cellulose diacetate and paper cigarette filters in the coastal ocean |url=https://pubs.rsc.org/en/content/articlelanding/2025/va/d4va00364k |journal=Environmental Science: Advances |language=en |volume=4 |issue=7 |pages=1014–1023 |doi=10.1039/D4VA00364K |issn=2754-7000|doi-access=free }}</ref>alt=Ashtray full of Cigarette butts|thumb|Ashtray full of cigarette butts Many governments and local authorities have imposed stiff penalties for littering of cigarette filters; for example 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 }}</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 receptacles, and expanding public education. Others have suggested banning 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 supercapacitor electrode material. These materials have demonstrated superior performance as compared to commercially available carbon, graphene and carbon nanotubes.<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 |page=34 |date=2014 |doi=10.1088/0957-4484/25/34/345601 |pmid=25092115 |bibcode=2014Nanot..25H5601L |s2cid=8692351 |doi-access=free }}</ref>
Another group of researchers has proposed adding tablets of food grade acid inside the filters. Once wet enough the tablets would 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 |title=No more butts: biodegradable filters a step to boot litter problem |url=http://www.environmentalhealthnews.org/ehs/newscience/2012/06/2012-0725-biodegradable-cigarette-filters |publisher=Environmental Health News |access-date=23 November 2014 |archive-date=29 November 2014 |archive-url=https://web.archive.org/web/20141129225410/http://www.environmentalhealthnews.org/ehs/newscience/2012/06/2012-0725-biodegradable-cigarette-filters }}</ref>
Some jurisdictions have introduced extended producer responsibility (EPR) requirements specifically for tobacco products with filters and filters sold for use with tobacco products aiming to reduce cigarette-butt littering and finance costs of collection and cleanup.<ref>{{Cite web |title=Extended producer responsibility for certain tobacco products and filters |url=https://www.naturvardsverket.se/en/guidance/extended-producer-responsibility-epr/extended-producer-responsibility-for-certain-tobacco-products-and-filters/ |access-date=2026-05-22 |website=www.naturvardsverket.se}}</ref><ref>{{Cite web |title=Single-use plastics in the European Union |url=https://europa.eu/youreurope/business/product-requirements/recycling-waste-management/single-use-plastics/index_en.htm |access-date=2026-05-22 |website=Your Europe |language=en}}</ref>
Some birds collect and add cigarette butts to their nests. It has been shown to reduce the number of parasites and improve the health of the nestlings.<ref name="Ogden">{{cite news |last1=Ogden |first1=Lesley Evans |title=Why Some Birds Seem to Be Developing a Cigarette Habit |url=https://www.nytimes.com/2026/03/18/science/bird-nests-cigarettes.html |access-date=19 March 2026 |work=The New York Times |date=18 March 2026 |language=en-US |quote=The toxins in tobacco may keep parasites at bay in the nests of blue tits, [...] But in studying Darwin finch nests, she found the birds hadn't learned to add enough butts to ward off the pests. [...] when researchers added more live ticks to nests, house finch females responded by adding more cigarette butts. [...] Dr. Suárez-Rodriguez showed that hatching, fledging and immune response in finch chicks improved alongside an increase in butts. But blood cells from nestlings showed evidence of genetic damage from cigarette butt exposure, with the long-term impacts unknown.}}</ref><ref name="Glądalski">{{cite journal |last1=Glądalski |first1=Michał |last2=Norte |first2=Ana Cláudia |last3=Bartos |first3=Maciej |last4=Demeško |first4=Iwona |last5=Kaliński |first5=Adam |last6=Markowski |first6=Marcin |last7=Skwarska |first7=Joanna |last8=Wawrzyniak |first8=Jarosław |last9=Zieliński |first9=Piotr |last10=Pietrala |first10=Maria |last11=Bańbura |first11=Jerzy |title=Urban blue tit nests and cigarette butts: accidental litter or adaptive behaviour? |journal=Animal Behaviour |date=March 2026 |volume=233 |article-number=123464 |doi=10.1016/j.anbehav.2026.123464 |url=https://www.sciencedirect.com/science/article/pii/S0003347226000011/pdfft?md5=d5663ba8129ae4c6055b0950a2c2abf0&pid=1-s2.0-S0003347226000011-main.pdf |access-date=19 March 2026 |language=en |format=PDF}}</ref>
== Activated charcoal filtration == Cigarette filter can incorporate an activated charcoal filtration system. Instead of acetate or cardboard filters, it consists of two ceramic caps on either sides containing activated charcoal, which reduces tar and other toxins in the smoke.<ref>{{cite journal | pmc=6471497 | date=2018 | last1=Goel | first1=R. | last2=Bitzer | first2=Z. T. | last3=Reilly | first3=S. M. | last4=Bhangu | first4=G. | last5=Trushin | first5=N. | last6=Elias | first6=R. J. | last7=Foulds | first7=J. | last8=Muscat | first8=J. | last9=Richie Jr | first9=J. P. | title=Effect of Charcoal in Cigarette Filters on Free Radicals in Mainstream Smoke | journal=Chemical Research in Toxicology | volume=31 | issue=8 | pages=745–751 | doi=10.1021/acs.chemrestox.8b00092 | pmid=29979036 }}</ref>
== See also == * Cigarette butt * Cigarette holder * List of additives in cigarettes * Nicotine marketing * Tobacco smoking
== References == {{Reflist|30em}}
{{Cigarettes}}
Category:Cigarettes Category:Air filters Category:1925 introductions Category:Hungarian inventions Category:Pollutants