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Revision as of 13:55, 15 February 2012 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Saving copy of the {{chembox}} taken from revid 476654862 of page Propylene_glycol for the Chem/Drugbox validation project (updated: '').		Latest revision as of 03:35, 9 December 2024 edit OAbot (talk | contribs)Bots439,234 editsm Open access bot: pmc updated in citation with #oabot.
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			{{Distinguish|Polypropylene glycol|Ethylene glycol|Polyethylene glycol}}
	{{ambox | text = This page contains a copy of the infobox ({{tl|chembox}}) taken from revid of page ] with values updated to verified values.}}
			{{about|1,2-propanediol|other propylene glycols|Propanediol}}
	{{chembox		{{chembox
			| Watchedfields = changed
	| verifiedrevid = 464362595
			| verifiedrevid = 477004593
	| Reference = <ref>'']'', 11th Edition, '''7868'''.</ref>
			| Reference = <ref>{{cite book |url= https://archive.org/details/merckindexency00buda |title= The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals |publisher= Merck & Co |isbn= 978-0911910285 |year= 1989 |url-access= registration }}</ref>
	| Name = '''Propylene glycol'''
			| Name =
	| ImageFile = Propylene glycol chemical structure.png
			| ImageFile = Propylene glycol chemical structure.png
	| ImageSize = 200px
	| ImageName = Propylene glycol		| ImageName = Propylene glycol
	| ImageFileR1 = PropyleneGlycol-spaceFill.png		| ImageFileR1 = PropyleneGlycol-spaceFill.png
			| ImageNameR1 = Space-filling model
	| ImageSizeR1 = 100px
			| ImageFileL1 = PropyleneGlycol-stickAndBall.png
	| ImageNameR1 = Space-filling model
			| ImageNameL1 = ball-and-stick model
	| ImageFileL1 = PropyleneGlycol-stickAndBall.png
			| PIN = Propane-1,2-diol
	| ImageSizeL1 = 100px
			| SystematicName =
	| ImageNameL1 = ball-and-stick model
			| OtherNames = {{Unbulleted list|Propylene glycol|α-Propylene glycol|1,2-Propanediol|1,2-Dihydroxypropane|Methyl ethyl glycol|Methylethylene glycol}}
	| IUPACName = propane-1,2-diol
			| IUPACName =
	| OtherNames = propylene glycol, α-propylene glycol, 1,2-propanediol, 1,2-Dihydroxypropane, methyl ethyl glycol (MEG), methylethylene glycol, PG, Sirlene, Dowfrost
	| Section1 = {{Chembox Identifiers		| Section1 = {{Chembox Identifiers
	| UNII_Ref = {{fdacite|correct|FDA}}		| UNII_Ref = {{fdacite|correct|FDA}}
	| UNII = 6DC9Q167V3		| UNII = 6DC9Q167V3
			| UNII1_Ref = {{fdacite|correct|FDA}}
			| UNII1 = 942194N4TD
			| UNII1_Comment = (S-enantiomer)
	| CASNo = 57-55-6		| CASNo = 57-55-6
	| CASNo_Ref = {{cascite|correct|CAS}}		| CASNo_Ref = {{cascite|correct|CAS}}
			| CASNo_Comment = racemic
	| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
			| CASNo2 = 4254-15-3
			| CASNo2_Comment = S-enantiomer
			| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
	| ChemSpiderID = 13835224		| ChemSpiderID = 13835224
	| ChEBI_Ref = {{ebicite|correct|EBI}}		| ChEBI_Ref = {{ebicite|correct|EBI}}
	| ChEBI = 16997		| ChEBI = 16997
			| KEGG = C00583
	| StdInChI_Ref = {{stdinchicite|correct|chemspider}}		| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
	| StdInChI = 1S/C3H8O2/c1-3(5)2-4/h3-5H,2H2,1H3		| StdInChI = 1S/C3H8O2/c1-3(5)2-4/h3-5H,2H2,1H3
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	| StdInChIKey = DNIAPMSPPWPWGF-UHFFFAOYSA-N		| StdInChIKey = DNIAPMSPPWPWGF-UHFFFAOYSA-N
	| PubChem = 1030		| PubChem = 1030
			| EC_number = 200-338-0
	| ChEMBL_Ref = {{ebicite|correct|EBI}}		| ChEMBL_Ref = {{ebicite|correct|EBI}}
	| ChEMBL = 286398		| ChEMBL = 286398
	| ATCvet = yes		| SMILES = CC(O)CO
			| RTECS = TY6300000
	| ATCCode_prefix = A16
	| ATCCode_suffix = QA01
	| SMILES = CC(O)CO
	| RTECS = TY6300000
	}}		}}
	| Section2 = {{Chembox Properties		| Section2 = {{Chembox Properties
			| C=3 | H=8 | O=2
	| Formula = C<sub>3</sub>H<sub>8</sub>O<sub>2</sub>
			| Appearance = colourless liquid
	| MolarMass = 76.09 g/mol
			| Odor = odorless
	| Density = 1.036 g/cm³
			| Density = 1.036 g/cm<sup>3</sup>
	| MeltingPt = {{convert|-59|°C|°F}}
			| MeltingPtC = -59
	| Solubility = fully ]
	| Solubility1 = fully ]		| Solubility = ]
	| Solvent1 = ethanol		| Solubility1 = Miscible
			| Solvent1 = ethanol
	| Solubility2 = fully ]
			| Solubility2 = Miscible
	| Solvent2 = diethyl ether
			| Solvent2 = diethyl ether
	| Solubility3 = fully ]
	| Solvent3 = acetone		| Solubility3 = Miscible
			| Solvent3 = acetone
	| Solubility4 = fully ]
			| Solubility4 = Miscible
	| Solvent4 = chloroform
			| Solvent4 = chloroform
	| BoilingPt = {{convert|188.2|°C|°F}}
			| BoilingPtC = 188.2
	| ThermalConductivity = {{{conductivity|0.34}}} W/m-K (50% H2O @ {{convert|90|°C|°F}})
			| ThermalConductivity = 0.34 W/m·K (50% H<sub>2</sub>O @ {{convert|90|°C|°F}})
			| VaporPressure = 10.66 Pa (20 °C)
			| Viscosity = 0.042 Pa·s
			| LogP = -1.34<ref name="chemsrc">{{Cite web |url= https://www.chemsrc.com/en/cas/57-55-6_674628.html |title= Propylene Glycol_msds}}</ref>
	}}		}}
			| Section3 =
			| Section4 = {{Chembox Thermochemistry
			| DeltaHf =
			| DeltaHc =
			| Entropy =
			| HeatCapacity = 189.9 J/(mol·K) <ref>{{cite book |last=Zaripov |first=Z.I. |author-link= |date=1982 |title=Experimental study of the isobaric heat capacity of liquid organic compounds with molecular weights of up to 4000 a.e.m. |url=https://webbook.nist.gov/cgi/cbook.cgi?ID=C57556&Mask=1883#ref-5 |location= |publisher= |page= |isbn=}}</ref>
			}} <!--Chembox Thermochemistry-->
			| Section5 =
			| Section6 = {{Chembox Pharmacology
			| ATCvet = yes
			| ATCCode_prefix = A16
			| ATCCode_suffix = QA01
			}}
	| Section7 = {{Chembox Hazards		| Section7 = {{Chembox Hazards
			| ExternalSDS =
	| ExternalMSDS =
	| NFPA-H = 0		| NFPA-H = 0
	| NFPA-F = 1		| NFPA-F = 1
	| NFPA-R = 0		| NFPA-R = 0
	| NFPA-O =		| NFPA-S =
			| GHSPictograms =
	| RPhrases =
			| GHSSignalWord =
	| SPhrases = {{S24}} {{S25}}
			| HPhrases = {{HPhrases|}}
	}}
			| PPhrases = {{PPhrases|}}
			| GHS_ref = <ref>GHS: "Kein gefährlicher Stoff nach GHS" </ref>
			}}<ref>{{cite web|url=http://cameochemicals.noaa.gov/chemical/9030|title=Propylene Glycol - Cameo Chemicals|website=NOAA Office of Response and Restoration|publisher=]|access-date=3 October 2018}}</ref>
	| Section8 = {{Chembox Related		| Section8 = {{Chembox Related
	| Function = ]s		| OtherFunction_label = ]s
	| OtherFunctn = ] ]		| OtherFunction = ], ]
	}}		}}
	}}		}}
			'''Propylene glycol''' (]: '''propane-1,2-diol''') is a viscous, colorless liquid. It is almost odorless and has a faintly sweet taste. Its ] is CH<sub>3</sub>CH(OH)CH<sub>2</sub>OH.
			As it contains two ] groups, it is classified as a ]. An ] diol may also be called a ]. It is ] with a broad range of solvents, including ], ], and ]. In general, glycols<ref>{{Cite book |last=Zapka |first=Maskrey |title=Hawaii Energy and Environmental Technologies (HEET) Initiative |year=2016}}</ref> are non-irritating and have very low ].<ref name=Ullmann>{{Ullmann|title=Propanediols|first1=Carl J. |last1=Sullivan|first2=Anja|last2=Kuenz|first3=Klaus-Dieter|last3=Vorlop|year=2018|doi=10.1002/14356007.a22_163.pub2}}</ref>
			For certain uses as a ], propylene glycol is considered as ] by the US ], and is approved for food manufacturing.<ref name="gras">{{cite web |title=Propylene glycol, Subpart B - Listing of Specific Substances Affirmed as GRAS, Sec. 184.1666 (original 25 June 1982) |url=https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=184.1666 |publisher=Title 21, Code of Federal Regulations, US Food and Drug Administration |access-date=20 November 2024 |date=30 August 2024}}</ref> In the European Union, it has ] E1520 for food applications. For cosmetics and ], the number is E490. Propylene glycol is also present in ], which is known as E405.
			Propylene glycol is approved and used as a vehicle for topical, oral, and some intravenous pharmaceutical preparations in the US and Europe.
			==Structure==
			The compound is sometimes called (alpha) '''α-propylene glycol''' to distinguish it from the ] ], known as (beta) β-propylene glycol. Propylene glycol is chiral. Commercial processes typically use the ]. The S-isomer is produced by biotechnological routes.
			==Production==
			===Industrial===
			Industrially, propylene glycol is mainly produced from ] (for food-grade use). According to a 2018 source, 2.16 M tonnes are produced annually.<ref name=Ullmann/> Manufacturers use either non-catalytic high-temperature process at {{convert|200|C|0}} to {{convert|220|C|0}}, or a catalytic method, which proceeds at {{convert|150|C|0}} to {{convert|180|C|0}} in the presence of ] or a small amount of sulfuric acid or alkali.<ref name=petro>{{Cite book |author1=Chauvel, Alain |author2=Lefebvre, Gilles | title=Petrochemical Processes | volume = 2: Major Oxygenated, Chlorinated and Nitrated Derivatives | publisher=Editions Technip | isbn= 9782710805632 | page=26|year=1989 }}</ref>
			]
			Final products contain 20% propylene glycol, 1.5% of ], and small amounts of other ]s.<ref>{{cite web|url=http://chemindustry.ru/1,2-Propanediol.php|title=1,2-propanediol: chemical product info at CHEMINDUSTRY.RU<!-- Bot generated title -->|access-date=3 October 2018}}</ref> Further purification produces finished industrial grade or USP/JP/EP/BP grade propylene glycol that is typically 99.5% or greater. Use of USP (US Pharmacopoeia) propylene glycol can reduce the risk of Abbreviated New Drug Application (ANDA) rejection.<ref>{{Cite web|date=2020-07-20|title=Propylene Glycol USP|url=https://berrymanchemical.com/blog/propylene-glycol-usp/|access-date=2020-07-28|website=Berryman Chemical|language=en-GB|archive-date=2020-07-28|archive-url=https://web.archive.org/web/20200728212012/https://berrymanchemical.com/blog/propylene-glycol-usp/|url-status=dead}}</ref>
			Propylene glycol can also be obtained from ], a byproduct from the production of ].<ref name=Ullmann/> This starting material is usually reserved for industrial use because of the noticeable odor and taste that accompanies the final product.
			===Laboratory===
			(S)-Propanediol is synthesized via fermentation methods. ] and ] are common intermediates. ], one of the two products of breakdown (]) of ], is a precursor to ]. This conversion is the basis of a potential biotechnological route to the commodity chemical ]. Three-carbon ]s are also precursor to the 1,2-diol.<ref name=Ullmann/>
			A small-scale, nonbiological route from ] is illustrated in the following scheme:<ref>{{cite book|last=Hanessian|first=Stephen|title=Total Synthesis of Natural Products: The 'Chiron' Approach|year=1983|publisher=Pergamon press|isbn=978-0080307152|page=41}}</ref>
			]
			==Applications==
			===Polymers===
			Forty-five percent of propylene glycol produced is used as a chemical feedstock for the production of unsaturated ]s. In this regard, propylene glycol reacts with a mixture of unsaturated ] and ] to give a ]. This partially unsaturated polymer undergoes further ]ing to yield ]s. Related to this application, propylene glycol reacts with propylene oxide to give ] and polymers that are used to produce ]s.<ref name=Ullmann/> Propylene glycol is used in water-based acrylic architectural paints to extend dry time which it accomplishes by preventing the surface from drying due to its slower evaporation rate compared to water.
			===Food and drug===
			In regulated amounts, propylene glycol is designated as safe for food manufacturing as an ], ], flavor agent, ], texturizer, ], ], ], ] agent, and ].<ref name=gras/><ref name="scogs">{{cite web |title=Propylene glycol |url=https://www.hfpappexternal.fda.gov/scripts/fdcc/index.cfm?set=SCOGS&sort=SCOGS_Report_Number&order=ASC&startrow=1&type=basic&search=propylene%20glycol |publisher=Select Committee on GRAS Substances, US Food and Drug Administration |access-date=5 December 2024 |date=31 July 2020}}</ref><ref name="fda-saf">{{cite web |title=Propylene glycol: Substances added to food |url=https://www.hfpappexternal.fda.gov/scripts/fdcc/index.cfm?set=FoodSubstances&id=PROPYLENEGLYCOL |publisher=US Food and Drug Administration |access-date=5 December 2024 |date=29 October 2024}}</ref>
			As regulated by the US FDA for substances deemed as GRAS, propylene glycol is "not subject to premarket review and approval by FDA because it is generally recognized, by qualified experts, to be safe under the intended conditions of use."<ref name=scogs/> The scientific panel evaluating propylene glycol for food manufacturing defined its conclusion as: "There is no evidence in the available information on that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current or might reasonably be expected in the future."<ref name=scogs/>
			The FDA law defined maximum limits for the use of propylene glycol in various food categories under ]s:<ref name=gras/>
			* 2.0% for general food categories
			* 2.5% for frozen dairy products
			* 5% for alcoholic beverages
			* 5% for nuts and nut products
			* 24% for confections and ]
			* 97% for seasonings and flavorings
			The ] authorizes propylene glycol for use in food manufacturing, establishing a safe daily intake of 25 mg per kg of body weight.<ref name="efsa">{{cite journal |author=EFSA Panel on Food Additives and Nutrient Sources added to Food |title=Re-evaluation of propane-1,2-diol (E 1520)as a food additive |url=https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2018.5235 |journal=EFSA Journal |access-date=6 December 2024 |doi=10.2903/j.efsa.2018.5235 |year=2018|volume=16|issue=4|page=5235|pmc=7009459 }}</ref> Specifically for ice cream or ] products, ] permits use of propylene glycol mono fatty acid esters as an emulsifier and stabilizer at a maximum level of use of 0.35% of the ice cream made from the ingredients mix.<ref name="hc">{{cite web |title=Modification to the List of permitted emulsifying, gelling, stabilizing or thickening agents to enable the use of propylene glycol mono fatty acid esters as an emulsifier and stabilizer in ice milk mix |url=https://www.canada.ca/en/health-canada/services/food-nutrition/public-involvement-partnerships/modification-lists-permitted-food-additives-enable-use-propylene-glycol-mono-fatty-acid-esters-emulsifier-stabilizer-milk.html |publisher=Health Canada, Government of Canada |access-date=6 December 2024 |date=13 February 2013}}</ref>
			Propylene glycol is used in a variety of other edible items, such as baked goods, desserts, prepared meals, flavoring mixes, candy, popcorn, whipped dairy products, and soda.<ref name="terrell">{{cite web |last1=Terrell |first1=Casey |title=What Is Propylene Glycol, and What Does It Do in Our Food? |url=https://foodinsight.org/what-is-propylene-glycol/ |publisher=Food Insight |access-date=6 December 2024 |date=18 May 2021}}</ref> It is also used in beer to stabilize the foam.<ref>{{cite journal |title=Mechanism of Beer Foam Stabilization by Propylene Glycol Alginate | author=G. Jackson, R. T. Roberts and T. Wainwright |journal=Journal of the Institute of Brewing |date=January 1980 | volume=86 | issue=1 | pages=34–37 | doi=10.1002/j.2050-0416.1980.tb03953.x}}</ref>
			]s used for delivery of pharmaceuticals or personal-care products often include propylene glycol among the ingredients.<ref name=Ullmann/> In alcohol-based hand sanitizers, it is used as a humectant to prevent the skin from drying.<ref>{{Cite news|url=https://www.livestrong.com/article/164674-ingredients-in-hand-sanitizer/|title=Ingredients in Hand Sanitizer|last=Lohrey|first=Jackie|work=LIVESTRONG.COM|access-date=2018-06-11}}</ref> Propylene glycol is used as a ] in many ], including ], ], and ] formulations. Many pharmaceutical drugs which are ] in water utilize propylene glycol as a solvent and carrier; ] tablets are one example.<ref>{{cite web | url=http://www.inchem.org/documents/pims/chemical/pim443.htm | title=Propylene glycol (PIM 443) | publisher=IPCS INChem | date=August 1991 | access-date=July 2, 2009 | vauthors = ((Janusz Szajewski, MD, Warsaw Poison Control Centre))}}</ref> Propylene glycol is also used as a solvent and carrier for many pharmaceutical ] preparations. Additionally, certain formulations of ] use propylene glycol as an ingredient.<ref>{{cite journal |vauthors=Pucker AD, Ng SM, Nichols JJ |title= Over the counter (OTC) artificial tear drops for dry eye syndrome |journal=Cochrane Database Syst Rev|volume=2016 |pages= CD009729 |date=2016 |issue= 2 |pmid= 26905373 |doi= 10.1002/14651858.CD009729.pub2 |pmc=5045033}}</ref>
			] aircraft.]]
			===Antifreeze===
			The ] of water is depressed when mixed with propylene glycol. It is used as aircraft ] and anti-icing fluid. A 50% water-diluted and heated solution is used for removal of icing accretions from the fuselages of commercial aircraft on the ground (de-icing), and 100% undiluted cold solution is used only on wings and tail surfaces of an aircraft in order to prevent ice accretion from forming during a specific period of time before takeoff (anti-icing). Normally, such time-frame is limited to 15–90 minutes, depending on the severity of snowfall and outside air temperature.<ref name=Ullmann/><ref>{{cite web |url=http://pubs.acs.org/cen/whatstuff/stuff/7901scit5.html |title=What's That Stuff? Aircraft Deicers |website=Chemical & Engineering News |publisher=American Chemical Society |date=2000-07-10 |access-date=2013-06-21}}</ref> Water-propylene glycol mixtures dyed pink to indicate the mixture is relatively nontoxic are sold under the name of ] or marine antifreeze. Propylene glycol is frequently used as a substitute for ] in low toxicity, environmentally friendly automotive ]. It is also used to winterize the plumbing systems in vacant structures.<ref>{{cite web|url=http://www.wikihow.com/Winterize-a-Vacant-Home |title=5 Ways to Winterize a Vacant Home |publisher=wikiHow |date=2012-06-11 |access-date=2014-02-27}}</ref> The ]/temperature is 60:40 propylene glycol:water/−60&nbsp;°C.<ref>{{cite web|url=http://webserver.dmt.upm.es/~isidoro/bk3/c07sol/Solution%20properties.pdf |title=Properties of Some Particular Solutions |publisher=Portal del DMT |access-date=2014-02-27}}</ref><ref>{{cite web|last=Salnick |first=Robert |url=http://windborneinpugetsound.blogspot.com/2010/08/why-does-holding-plate-work.html |title=Windborne in Puget Sound: Why does a holding plate work? |publisher=Windborneinpugetsound.blogspot.com |date=2010-08-04 |access-date=2014-02-27}}</ref> The −50&nbsp;°F/−45&nbsp;°C commercial product is, however, water rich; a typical formulation is 40:60.<ref>{{cite web|url=http://www.chemicalspec.com/Winter_Care_4060_RV_Antifreeze.pdf |title=Material Safety Data Sheet: Winter Care RV Antifreeze |publisher=Chemical Specialties |access-date=2014-02-27}}</ref>
			===Electronic cigarettes liquid===
			Propylene glycol, vegetable ],<ref>{{Cite journal |last1=Agoons |first1=Dayawa D. |last2=Agoons |first2=Batakeh B. |last3=Emmanuel |first3=Kelechi E. |last4=Matawalle |first4=Firdausi A. |last5=Cunningham |first5=Jessica M. |date=2021-01-01 |title=Association between electronic cigarette use and fragility fractures among US adults |journal=American Journal of Medicine Open |language=en |volume=1-6 |pages=100002 |doi=10.1016/j.ajmo.2021.100002 |s2cid=244502249 |issn=2667-0364|doi-access=free |pmid=39036626 |pmc=11256257 }}</ref> or a mixture of both, are the main ingredients in ] used in ]. They are ] to resemble smoke and serve as carriers for substances such as ] and ]s.<ref name="Varlet">{{cite journal | last=Varlet | first=Vincent | display-authors=etal | title=Toxicity Assessment of Refill Liquids for Electronic Cigarettes | journal=International Journal of Environmental Research and Public Health | volume=12 | issue=5 | date=2015 | pages=4796–4815 | issn=1660-4601 | doi=10.3390/ijerph120504796 | pmid=25941845 | pmc=4454939 | doi-access=free }}</ref>
			==Miscellaneous applications<!--if 2 million tons are produced annually, a lot of minor apps-->==
			* As a ] for many substances, both natural and synthetic.<ref name="BradleyAbraham2015">{{cite journal|last1=Bradley|first1=Jean-Claude|last2=Abraham|first2=Michael H|last3=Acree|first3=William E|last4=Lang|first4=Andrew|title=Predicting Abraham model solvent coefficients|journal=Chemistry Central Journal|volume=9|issue=1|year=2015|pages=12|issn=1752-153X|doi=10.1186/s13065-015-0085-4|pmid=25798192|pmc=4369285 |doi-access=free }}</ref>
			* As a ] (E1520).
			* As a ] for ].
			* In veterinary medicine as an oral treatment for ] in ]s.<ref>{{cite journal | url=https://www.researchgate.net/publication/248332819 | title=Propylene glycol for dairy cows | author=Nielsen, Nicolaj | journal=Animal Feed Science and Technology | doi=10.1016/j.anifeedsci.2004.03.008 | volume=115 | issue=3–4 | pages=191–213| year=2004 }}</ref>
			* In the cosmetics industry, where propylene glycol is very commonly used as a carrier or base for various types of makeup.<ref>{{Cite journal|last1=Fiume|first1=Monice M.|last2=Bergfeld|first2=Wilma F.|last3=Belsito|first3=Donald V.|last4=Hill|first4=Ronald A.|last5=Klaassen|first5=Curtis D.|last6=Liebler|first6=Daniel|last7=Marks|first7=James G.|last8=Shank|first8=Ronald C.|last9=Slaga|first9=Thomas J.|display-authors=3|date=September 2012|title=Safety assessment of propylene glycol, tripropylene glycol, and PPGs as used in cosmetics|journal=International Journal of Toxicology|volume=31|issue=5 Suppl|pages=245S–60S|doi=10.1177/1091581812461381|issn=1092-874X|pmid=23064775|s2cid=24754435|doi-access=free}}</ref>
			* For ] and preserving insects (including as a ] preservative).<ref>{{Cite journal|last1=Rubin|first1=Benjamin E. R.|last2=Czekanski-Moir|first2=Jesse E.|last3=Wray|first3=Brian D.|last4=Moreau|first4=Corrie S.|date=2013-03-13|title=DNA preservation: a test of commonly used preservatives for insects|journal=Invertebrate Systematics|language=en|volume=27|issue=1|pages=81–86|doi=10.1071/IS12067|s2cid=4820463|issn=1447-2600}}</ref>
			* For the creation of ] in special effects for film and live entertainment. So-called 'smoke machines' or 'hazers' vaporize a mixture of propylene glycol and water to create the illusion of smoke. While many of these machines use a propylene glycol-based fluid, some use oil. Those which use propylene glycol do so in a process that is identical to how electronic cigarettes work; utilizing a heating element to produce a dense vapor. The vapor produced by these machines has the aesthetic look and appeal of smoke, but without exposing performers and stage crew to the harms and odors associated with actual smoke.<ref>{{Cite web|url=https://nevadafilm.com/production-notes-haze-machines/|title=Production Notes: Haze Machines|last=Nevada Film Office|date=February 19, 2019|website=nevadafilm.com|access-date=November 1, 2019}}</ref><ref>{{Cite web|url=https://www.provideocoalition.com/atmosphere101|title=Atmosphere: Hazers, Fazers, Smoke and Fog 101 by Daniel Brea|last=Daniel|first=Brea|date=July 15, 2016|website=provideocoalition.com|url-status=dead|archive-url=https://web.archive.org/web/20160719141901/http://www.provideocoalition.com/atmosphere101|archive-date=2016-07-19|access-date=November 1, 2019}}</ref>
			* As an additive in ] (PCR) to reduce the melting temperature of ] for targeting of ] sequences.{{Citation needed|date=April 2021}}
			* As a ], it is used to prevent water from beading up on objects. It is used in photography for this purpose to reduce the risk of water spots, or deposits of minerals from water used to process film or paper.
			==Safety in humans==
			When used in average quantities, propylene glycol has no measurable effect on development and/or reproduction on animals and probably does not adversely affect human development or reproduction without active use.<ref name="National Toxicology Program NIEHS 2004">{{citation |author= National Toxicology Program NIEHS |year= 2004|title=NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Propylene Glycol | id = NIH Publication No. 04-4482 }}</ref> The ]—which utilize propylene glycol-based preparations of nicotine or THC and other cannabinoids—is the subject of much controversy.<ref>{{Cite web|url=https://www.cdc.gov/tobacco/basic_information/e-cigarettes/index.htm|title=Electronic Cigarettes|last=CDC|date=March 11, 2019}}</ref><ref>{{Cite web|url=https://www.leafly.com/news/health/vaping-vs-smoking-marijuana-safety|title=Is Vaping Safe?|last=Havelka|first=Jacqueline|date=April 27, 2017|website=leafly.com}}</ref><ref>{{Cite web|url=https://www.herbonaut.com/are-vaporizers-safe/|title=Are Vaporizers Safe?|last=Peki|first=Winston|date=May 5, 2019|website=herbonaut.com}}</ref> ] has also been identified in this controversy.<ref>{{cite web|url=https://www.cdc.gov/tobacco/basic_information/e-cigarettes/severe-lung-disease.html#overview|title=Outbreak of Lung Injury Associated with the Use of E-Cigarette, or Vaping, Products|publisher=]|year=2020}}</ref>
			===Oral administration===
			The acute oral toxicity of propylene glycol is very low, and large quantities are required to cause perceptible health effects in humans;<ref name=scogs/> in fact, the toxicity of propylene glycol is one third that of ].<ref>{{cite journal |title=Propylene glycol: Rate of metabolism absorption, and excretion, with a method for estimation in body fluids. |author=Lehman A, Newman H |journal=J Pharmacol Exp Ther |volume=60 |pages=312–322 |year=1937 }}</ref> Propylene glycol is metabolized in the human body into ] (a normal part of the glucose-metabolism process, readily converted to energy), ] (handled by ethanol-metabolism), ] (a normal acid generally abundant during digestion),<ref>{{cite journal |author = Hamilton, D. J. |title = Gastric Dyspepsia |journal = The Lancet |volume =2 |issue = 3493 |year = 1890 |page = 306 |doi=10.1016/S0140-6736(02)17110-8}}</ref> and ] (a potentially hazardous substance).<ref>{{cite web |url = http://www.sciencelab.com/msds.php?msdsId=9924730 |publisher = ScienceLab.com |year = 2010 |title = Material Safety Data Sheet Propionaldehyde MSDS}}</ref><ref>{{cite journal |author = Miller DN, Bazzano G |year = 1965 |title = Propanediol metabolism and its relation to lactic acid metabolism |journal = Ann NY Acad Sci |volume = 119 |pages = 957–973 |bibcode = 1965NYASA.119..957M |last2 = Bazzano |doi = 10.1111/j.1749-6632.1965.tb47455.x |pmid = 4285478 |issue = 3| s2cid = 37769342 }}</ref><ref>{{cite journal |author = Ruddick JA |year = 1972 |title = Toxicology, metabolism, and biochemistry of 1,2-propanediol |journal = Toxicol Appl Pharmacol |volume = 21 |issue = 1 |pages = 102–111 |doi = 10.1016/0041-008X(72)90032-4 |pmid = 4553872 |bibcode = 1972ToxAP..21..102R }}</ref> According to the ], the ] (dose that kills 50% of the test population) for rats is 20 g/kg (oral/rat).<ref>{{cite web | website = rocklinusd.org|title= Lethal dose table |url= http://whs.rocklinusd.org/documents/Science/Lethal_Dose_Table.pdf}}</ref><ref>{{cite web |author= Alton E. Martin and Frank H. Murphy | publisher = Dow Chemical Company |title= GLYCOLS - PROPYLENE GLYCOLS |url= http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_006e/0901b8038006e13c.pdf?filepath=propyleneglycol/pdfs/noreg/117-01785.pdf&fromPage=GetDoc }}</ref>
			Toxicity generally occurs at plasma concentrations over 4&nbsp;g/L, which requires extremely high intake over a relatively short period of time, or when used as a vehicle for drugs or vitamins given intravenously or orally in large ].<ref>Flanagan RJ; Braithwaite RA; Brown SS; et al. The International Programme on Chemical Safety: Basic Analytical Toxicology. WHO, 1995.</ref> It would be nearly impossible to reach toxic levels by consuming foods or supplements, which contain at most 1&nbsp;g/kg of PG, except for alcoholic beverages in the US which are allowed 5 percent = 50&nbsp;g/kg.<ref name=gras/><ref name=scogs/> Cases of propylene glycol poisoning are usually related to either inappropriate intravenous administration or accidental ingestion of large quantities by children.<ref>National Library of Medicine; Propylene glycol is used in antifreeze. Human Toxicity Excerpts: CAS Registry Number: 57-55-6 (1,2-Propylene Glycol). Selected toxicity information from HSDB. 2005.</ref>
			The potential for long-term oral toxicity is also low.<ref name="scogs-opinion">{{cite web |title=Select Committee on GRAS Substances Opinion: Propylene Glycol and Propylene Glycol Monostearate |url=https://wayback.archive-it.org/7993/20171031062706/https://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/SCOGS/ucm261045.htm |publisher=Select Committee on GRAS Substances, US Food and Drug Administration |access-date=5 December 2024 |date=29 September 2015}}</ref> In a ] continuous breeding study, no effects on fertility were observed in male or female mice that received propylene glycol in drinking water at doses up to 10100&nbsp;mg/kg bw/day. No effects on fertility were seen in either the first or second generation of treated mice.<ref name="National Toxicology Program NIEHS 2004"/> In a 2-year study, 12 rats were provided with feed containing as much as 5% propylene glycol, and showed no apparent ill effects.<ref>{{cite journal |last1=Gaunt |first1=I. F. |last2=Carpanini |first2=F. M. B. |last3=Grasso |first3=P. |last4=Lansdown |first4=A. B. G. |title=Long-term toxicity of propylene glycol in rats |journal=] |year=1972 |volume=10 |issue=2 |pages=151–162 |doi=10.1016/S0015-6264(72)80193-7 |pmid=5072816 }}</ref>
			===Skin and eye contact===
			].]]
			Propylene glycol may be non-irritating to the skin, see section ] below for details on allergic reactions.<ref>{{citation | publisher = Agency for Toxic Substances and Disease Registry |year= 2008|title=Addendum to the Toxicological Profile for Propylene Glycol |page= 7 }}</ref> Undiluted propylene glycol is minimally irritating to the eye, producing slight transient ]; the eye recovers after the exposure is removed.
			A 2018 human volunteer study found that 10 male and female subjects undergoing 4 hours exposures to concentrations of up to 442&nbsp;mg/m3 and 30 minutes exposures to concentrations of up to 871&nbsp;mg/m3 in combination with moderate exercise did not show pulmonary function deficits, or signs of ocular irritation, with only slight symptoms of respiratory irritation reported.<ref name="Dalton 2018">{{cite journal | title=Lack of respiratory and ocular effects following acute propylene glycol exposure in healthy humans. | author1=Dalton P |author2=Soreth B |author3=Maute C |author4=Novaleski C |author5=Banton M |display-authors=3| journal=Inhal. Toxicol. | volume=30 | issue=3 | pages=124–132| year=2018| doi=10.1080/08958378.2018.1470207 | pmid=29764241 | bibcode=2018InhTx..30..124D | s2cid=21711274 }}</ref>
			Propylene glycol has not caused ] or carcinogenicity in laboratory animal studies, nor has it demonstrated ] potential.<ref name="UNEP">{{cite web |title=1,2-Dihydroxypropane: SIDS Initial Assessment Report for 11th SIAM |url=http://www.chem.unep.ch/irptc/sids/OECDSIDS/57-55-6.pdf |access-date=2008-01-08 |url-status=dead |archive-url=https://web.archive.org/web/20090219045910/http://www.chem.unep.ch/irptc/sids/OECDSIDS/57-55-6.pdf |archive-date=2009-02-19 |publisher=UNEP Publications |date=January 23–26, 2001 |pages=15–22}}</ref><ref>Title 21, U.S. Code of Federal Regulations. 1999.</ref>
			===Inhalation===
			Inhalation of propylene glycol vapors appears to present no significant hazard in ordinary applications.<ref name="Robertson47">{{cite journal | url=http://jpet.aspetjournals.org/content/91/1/52.abstract | title=Tests for the chronic toxicity of propylene glycol and triethylene glycol on monkeys and rats by vapor inhalation and oral administration |author1=Robertson, OH |author2=Loosli, CG |author3=Puck, TT |author4=Wise, H |author5=Lemon, HM |author6=Lester, W |display-authors=3| journal=Journal of Pharmacology and Experimental Therapeutics|date=September 1947 | volume=91 | issue=1 | pages=52–76 | pmid=20265820 | quote=air containing these vapors in amounts up to the saturation point is completely harmless}}</ref> Due to the lack of chronic inhalation data, it is recommended that propylene glycol not be used in inhalation applications such as theatrical productions, or antifreeze solutions for emergency ] stations.<ref>, Dow, page 36</ref> Recently, propylene glycol (commonly alongside ]) has been included as a carrier for nicotine and other additives in ], the use of which presents a novel form of exposure. The potential hazards of chronic inhalation of propylene glycol or the latter substance as a whole are as-yet unknown.<ref>{{Cite web|url=https://vapingcheap.com/vaping-vs-smoking/#tab-con-1|title = Vaping vs Smoking: Is the Former Really a Healthier Alternative?|date = 29 June 2020}}</ref>
			According to a 2010 study, the concentrations of PGEs (counted as the sum of propylene glycol and ]) in indoor air, particularly bedroom air, has been linked to increased risk of developing numerous respiratory and immune disorders in children, including ], ], ], and allergies, with increased risk ranging from 50% to 180%. This concentration has been linked to use of water-based paints and water-based system cleansers. However, the study authors write that ] and not propylene glycol are the likely culprit.<ref>{{cite news |url=https://www.sciencedaily.com/releases/2010/10/101019084607.htm |title=Everyday Substances Increase Risk of Allergies in Children, Swedish Study Reveals |work=ScienceDaily |date=Oct 19, 2010 }}</ref><ref>{{cite web|url=http://www.hsph.harvard.edu/news/features/features/paints-cleaners-children-asthma-allergy.html|title=Chemical Compounds Emitted From Common Household Paints and Cleaners Increase Risks of Asthma and Allergies in Children|publisher=Harvard|access-date=3 October 2018|archive-date=17 February 2011|archive-url=https://web.archive.org/web/20110217071525/http://www.hsph.harvard.edu/news/features/features/paints-cleaners-children-asthma-allergy.html|url-status=dead}}</ref><ref>{{Cite journal| volume = 5| issue = 10| pmc = 2956675| pages = e13423| last = Choi| pmid = 20976153| first = Hyunok |author2=Norbert Schmidbauer |author3=] |author4=Mikael Hasselgren |author5=John Spengler |author6=Carl-Gustaf Bornehag| title = Common Household Chemicals and the Allergy Risks in Pre-School Age Children| journal = PLOS ONE| date = 2010-10-18| editor1-last = Hartl| editor1-first = Dominik| doi = 10.1371/journal.pone.0013423| bibcode = 2010PLoSO...513423C |display-authors=3| doi-access = free}}</ref>
			===Intravenous administration===
			Studies with intravenously administered propylene glycol have resulted in LD<sub>50</sub> values in rats and rabbits of 7&nbsp;mL/kg BW.<ref>{{Cite journal |author=Ruddick |year= 1972 |title=Toxicology, metabolism, and biochemistry of 1,2-propanediol. |journal=Toxicol Appl Pharmacol |volume=21 |issue= 1 |pages=102–111 |doi= 10.1016/0041-008X(72)90032-4 |pmid= 4553872|bibcode= 1972ToxAP..21..102R }}</ref> Ruddick (1972) also summarized intramuscular LD<sub>50</sub> data for rat as 13–20 mL/kg BW, and 6&nbsp;mL/kg BW for the rabbit. Adverse effects to ] of drugs that use propylene glycol as an ] have been seen in a number of people, particularly with large bolus dosages. Responses may include CNS depression, "hypotension, ], ] and ] abnormalities on the ECG, ], cardiac arrhythmias, seizures, agitation, serum ], ], and ]".<ref>Szajewski, Janusz. "Propylene Glycol (PIM 443)." 1991. 2 June 2010 http://www.inchem.org/documents/pims/chemical/pim443.htm#SectionTitle:9.1%20%20Acute%20poisoning</ref> A high percentage (12–42%) of directly-injected propylene glycol is eliminated or secreted in urine unaltered depending on dosage, with the remainder appearing in its ]-form. The speed of ] decreases as dosage increases,<ref>{{Cite journal |last1 = Speth |first1 = P. A. J. |last2 = Vree |first2 = T. B. |last3 = Neilen |first3 = N. F. M. |last4 = De Mulder |first4 = P. H. M. |last5 = Newell |first5 = D. R. | last6 = Gore | first6 = M. E. |last7 = De Pauw |first7 = B. E. |doi = 10.1097/00007691-198709000-00001 |title = Propylene Glycol Pharmacokinetics and Effects after Intravenous Infusion in Humans |journal = Therapeutic Drug Monitoring |volume = 9 |issue = 3 |pages = 255–258 |year = 1987 |pmid = 3672566 |s2cid = 23317790 |display-authors=3 }}</ref> which may be due to propylene glycol's mild anesthetic / ] properties as an alcohol.<ref>{{cite journal |last1=Seidenfeld |first1=M. A. |last2=Hanzlik |first2=P. J. |year=1932 |title=The general properties, actions, and toxicity of propylene glycol |journal=] |volume=44 |pages=109–121 }}</ref> In one case, intravenous administration of propylene glycol-suspended ] to an elderly man may have induced coma and ].<ref name="DemeyDaelemans1984">{{cite journal |last1=Demey |first1=H. |last2=Daelemans |first2=R. |last3=De Broe |first3=M.E. |last4=Bossaert |first4=L. |title=Propylene glycol intoxication due to intravenous nitroglycerin |journal=The Lancet |volume=323 |issue=8390 |year=1984 |pages=1360 |issn=0140-6736 |doi=10.1016/S0140-6736(84)91860-9 |pmid=6145062 |s2cid=36606490}}</ref> However, no confirmed lethality from propylene glycol was reported.
			===Animals===
			Propylene glycol is an approved food additive for dog and ] food under the category of animal feed and is ] for dogs,<ref>FDA. "Subchapter E - Animal Drugs, Feeds, and Related Products; § 582.1666. Propylene glycol." ''Code of Federal Regulations,'' {{USCFR|21|582|1666}}</ref> with an LD<sub>50</sub> of 9&nbsp;mL/kg. The LD<sub>50</sub> is higher for most laboratory animals (20&nbsp;mL/kg).<ref>{{Cite book |author1=Peterson, Michael |author2=Talcott, Patricia A. |title=Small animal toxicology |year=2006 |publisher=Saunders Elsevier |location=St. Louis |isbn=978-0-7216-0639-2 |page=997}}</ref> However, it is prohibited for use in food for cats due to links to ] formation and a reduced lifespan of red blood cells.<ref>{{cite web |url=http://www.lyondellbasell.com/techlit/techlit/2275.pdf |title= Propylene glycol and cats |archive-url= https://web.archive.org/web/20150227043018/http://www.lyondellbasell.com/techlit/techlit/2275.pdf |access-date=2013-06-21 |archive-date= 2015-02-27 }}</ref> Heinz body formation from MPG has not been observed in dogs, cattle, or humans.
			PG has been used in the ] since the 1950s for cows showing signs of ]. The negative energy balance during the early stages of lactation can cause the animal's body to have lower glucose levels, inducing the liver to make up for this by the conversion of body fat, leading to several health conditions, e.g. ].<ref name=dairy>, Bulent Elitok, Journal of Reproductive Health and Contraception, April 23, 2018.</ref> PG "reduces the ] ratio of ] to ], while increasing conversion of ruminal PG to propionate, and aid in the closure of energy deficit in cattle."<ref name=dairy />
			===Allergic reaction===
			Estimates on the prevalence of propylene glycol allergy range from 0.8% (10% propylene glycol in aqueous solution) to 3.5% (30% propylene glycol in aqueous solution).<ref name=":1">{{Cite journal|last1=Warshaw|first1=Erin M.|last2=Botto|first2=Nina C.|last3=Maibach|first3=Howard I.|last4=Fowler|first4=Joseph F.|last5=Rietschel|first5=Robert L.|last6=Zug|first6=Kathryn A.|last7=Belsito|first7=Donald V.|last8=Taylor|first8=James S.|last9=DeLeo|first9=Vincent A.|date=January 2009|title=Positive patch-test reactions to propylene glycol: a retrospective cross-sectional analysis from the North American Contact Dermatitis Group, 1996 to 2006|journal=Dermatitis: Contact, Atopic, Occupational, Drug|volume=20|issue=1|pages=14–20|issn=2162-5220|pmid=19321115|doi=10.2310/6620.2008.08039|s2cid=959002 |display-authors=3}}</ref><ref>{{Cite journal|last1=Lessmann|first1=Holger|last2=Schnuch|first2=Axel|last3=Geier|first3=Johannes|last4=Uter|first4=Wolfgang|date=November 2005|title=Skin-sensitizing and irritant properties of propylene glycol|journal=Contact Dermatitis|volume=53|issue=5|pages=247–259|doi=10.1111/j.0105-1873.2005.00693.x|issn=0105-1873|pmid=16283903|s2cid=13006333|doi-access=free}}</ref><ref>{{Cite journal|last1=Wetter|first1=David A.|last2=Yiannias|first2=James A.|last3=Prakash|first3=Amy V.|last4=Davis|first4=Mark D. P.|last5=Farmer|first5=Sara A.|last6=el-Azhary|first6=Rokea A.|display-authors=3|date=November 2010|title=Results of patch testing to personal care product allergens in a standard series and a supplemental cosmetic series: an analysis of 945 patients from the Mayo Clinic Contact Dermatitis Group, 2000-2007|journal=Journal of the American Academy of Dermatology|volume=63|issue=5|pages=789–798|doi=10.1016/j.jaad.2009.11.033|issn=1097-6787|pmid=20643495}}</ref> The North American Contact Dermatitis Group (NACDG) data from 1996 to 2006 showed that the most common site for propylene glycol ] was the face (25.9%), followed by a generalized or scattered pattern (23.7%).<ref name=":1" /> Investigators believe that the incidence of allergic contact dermatitis to propylene glycol may be greater than 2% in patients with ] or fungal infections, which are very common in countries with lesser sun exposure and lower-than-normal ] balances. Therefore, propylene glycol allergy is more common in those countries.<ref name="AMA-DEA1994">{{citation | publisher = American Medical Association, Council on Drugs|year=1994| title = AMA Drug Evaluations Annual 1994|page=1224}}</ref>
			Because of its potential for allergic reactions and frequent use across a variety of topical and systemic products, propylene glycol was named the American Contact Dermatitis Society's ] for 2018.<ref name=":0">{{Cite journal|last1=Jacob|first1=Sharon E.|last2=Scheman|first2=Andrew|last3=McGowan|first3=Maria A.|date=January–February 2018|title=Propylene Glycol|journal=Dermatitis: Contact, Atopic, Occupational, Drug|volume=29|issue=1|pages=3–5|doi=10.1097/DER.0000000000000315|issn=2162-5220|pmid=29059092|s2cid=24598433}}</ref><ref>{{Cite web|url=https://www.mdedge.com/clinicianreviews/article/176541/contact-dermatitis/allergen-year-may-be-nearer-you-think|title=Allergen of the year may be nearer than you think|website=www.mdedge.com|language=en|access-date=2019-04-08}}</ref> Recent publication from The Mayo Clinic reported 0.85% incidence of positive patch tests to propylene glycol (100/11,738 patients) with an overall irritant rate of 0.35% (41/11,738 patients) during a 20-year period of 1997–2016.<ref>{{Cite journal|author1=Lalla SC |author2=Nguyen H |author3=Chaudhry H |author4=Killian JM |author5=Drage LA |author6=Davis MDP |author7=Yiannias JA |author8=Hall MR. |display-authors=3 |year= 2018|title=Patch Testing to Propylene Glycol: The Mayo Clinic Experience. |journal=Dermatitis |volume=29 |issue=4 |pages= 200–205|doi=10.1097/DER.0000000000000393 |pmid= 29923851|s2cid= 49311147}}</ref> 87% of the reactions were classified as weak and 9% as strong. The positive reaction rates were 0%, 0.26%, and 1.86% for 5%, 10%, and 20% propylene glycol respectively, increasing with each concentration increase. The irritant reaction rates were 0.95%, 0.24%, and 0.5% for 5%, 10%, and 20% propylene glycol, respectively. Propylene glycol skin sensitization occurred in patients sensitive to a number of other concomitant positive allergens, most common of which were: Myroxylon pereirae resin, benzalkonium chloride, carba mix, potassium dichromate, neomycin sulfate; for positive propylene glycol reactions, the overall median of 5 and mean of 5.6 concomitant positive allergens was reported.
			==Environmental impacts==
			Propylene glycol occurs naturally, probably as the result of anaerobic catabolism of sugars in the human gut. It is degraded by ]-dependent enzymes, which convert it to ].<ref name=biodeg>{{cite journal |doi=10.1007/s00203-003-0601-0 |title=PduP is a coenzyme-a-acylating propionaldehyde dehydrogenase associated with the polyhedral bodies involved in B<sub>12</sub> -dependent 1,2-propanediol degradation by ''Salmonella enterica'' serovar Typhimurium LT2 |year=2003 |last1=Leal |first1=Nicole A. |last2=Havemann |first2=Gregory D. |last3=Bobik |first3=Thomas A. |journal=Archives of Microbiology |volume=180 |issue=5 |pages=353–361 |pmid=14504694 |bibcode=2003ArMic.180..353L |s2cid=44010353}}</ref>
			Propylene glycol is expected to degrade rapidly in water from biological processes, but is not expected to be significantly influenced by hydrolysis, oxidation, ], ], or ] to sediment.<ref name="UNEP"/> Propylene glycol is readily biodegradable under aerobic conditions in freshwater, in seawater and in soil. Therefore, propylene glycol is considered as not persistent in the environment.
			Propylene glycol exhibits a low degree of toxicity toward aquatic organisms. Several guideline studies available for freshwater fish with the lowest observed lethal concentration of 96-h ] value of 40,613&nbsp;mg/L in a study with '']''. Similarly, the lethal concentration determined in marine fish is a 96-h LC50 of >10,000&nbsp;mg/L in '']''.
			Although propylene glycol has low toxicity, it exerts high levels of ] (BOD) during degradation in surface waters. This process can adversely affect aquatic life by consuming oxygen needed by aquatic organisms for survival. Large quantities of ] (DO) in the ] are consumed when ] decompose propylene glycol.<ref>{{Cite report |date=April 2012 |title=Environmental Impact and Benefit Assessment for the Final Effluent Limitation Guidelines and Standards for the Airport Deicing Category |url=https://www.epa.gov/eg/airport-deicing-effluent-guidelines-documents |publisher=U.S. Environmental Protection Agency (EPA) |location=Washington, D.C. |id=EPA 821-R-12-003}}</ref>{{rp|2–23}}
			==References==
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			==External links==
			{{commons category|1,2-Propanediol}}
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