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  • Sugar Substitute

    sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie (non-nutritive)[2] or low-calorie sweetenerArtificial sweeteners may be derived through manufacturing of plant extracts or processed by chemical synthesis. Sugar substitute products are commercially available in various forms, such as small pills, powders and packets.

    Common sugar substitutes include aspartamemonk fruit extract, saccharinsucralosesteviaacesulfame potassium (ace-K) and cyclamate. These sweeteners are a fundamental ingredient in diet drinks to sweeten them without adding calories. Additionally, sugar alcohols such as erythritolxylitol and sorbitol are derived from sugars.

    No links have been found between approved artificial sweeteners and cancer in humans. Reviews and dietetic professionals have concluded that moderate use of non-nutritive sweeteners as a safe replacement for sugars can help limit energy intake and assist with managing blood glucose and weight.

    Description

    [edit]

    A sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie (non-nutritive)[2] or low-calorie sweetener. Sugar substitute products are commercially available in various forms, such as small pills, powders and packets.

    Types

    [edit]

    This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.
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    Artificial sweeteners may be derived through manufacturing of plant extracts or processed by chemical synthesis.

    High-intensity sweeteners—one type of sugar substitute—are compounds with many times the sweetness of sucrose (common table sugar). As a result, much less sweetener is required and energy contribution is often negligible. The sensation of sweetness caused by these compounds is sometimes notably different from sucrose, so they are often used in complex mixtures that achieve the most intense sweet sensation.

    In North America, common sugar substitutes include aspartamemonk fruit extract, saccharinsucralose and steviaCyclamate is prohibited from being used as a sweetener within the United States, but is allowed in other parts of the world.[3]

    Sorbitolxylitol and lactitol are examples of sugar alcohols (also known as polyols). These are, in general, less sweet than sucrose but have similar bulk properties and can be used in a wide range of food products. Sometimes the sweetness profile is fine-tuned by mixing with high-intensity sweeteners.

    Allulose

    [edit]

    Main article: Allulose

    Allulose is a sweetener in the sugar family, with a chemical structure similar to fructose. It is naturally found in figs, maple syrup and some fruit. While it comes from the same family as other sugars, it does not substantially metabolize as sugar in the body.[4] The FDA recognizes that allulose does not act like sugar, and as of 2019, no longer requires it to be listed with sugars on U.S. nutrition labels.[5] Allulose is about 70% as sweet as sugar, which is why it is sometimes combined with high-intensity sweeteners to make sugar substitutes.[6]

    Acesulfame potassium

    [edit]

    Main article: Acesulfame potassium

    Acesulfame potassium (Ace-K) is 200 times sweeter than sucrose (common sugar), as sweet as aspartame, about two-thirds as sweet as saccharin, and one-third as sweet as sucralose. Like saccharin, it has a slightly bitter aftertaste, especially at high concentrations. Kraft Foods has patented the use of sodium ferulate to mask acesulfame’s aftertaste. Acesulfame potassium is often blended with other sweeteners (usually aspartame or sucralose), which give a more sucrose-like taste, whereby each sweetener masks the other’s aftertaste and also exhibits a synergistic effect in which the blend is sweeter than its components.

    Unlike aspartame, acesulfame potassium is stable under heat, even under moderately acidic or basic conditions, allowing it to be used as a food additive in baking or in products that require a long shelf life. In carbonated drinks, it is almost always used in conjunction with another sweetener, such as aspartame or sucralose. It is also used as a sweetener in protein shakes and pharmaceutical products, especially chewable and liquid medications, where it can make the active ingredients more palatable.

    Aspartame

    [edit]

    Main article: Aspartame

    Aspartame was discovered in 1965 by James M. Schlatter at the G.D. Searle company. He was working on an anti-ulcer drug and accidentally spilled some aspartame on his hand. When he licked his finger, he noticed that it had a sweet taste. Torunn Atteraas Garin oversaw the development of aspartame as an artificial sweetener. It is an odorless, white crystalline powder that is derived from the two amino acids aspartic acid and phenylalanine. It is about 180–200 times sweeter than sugar,[7][8] and can be used as a tabletop sweetener or in frozen desserts, gelatins, beverages and chewing gum. When cooked or stored at high temperatures, aspartame breaks down into its constituent amino acids. This makes aspartame undesirable as a baking sweetener. It is more stable in somewhat acidic conditions, such as in soft drinks. Though it does not have a bitter aftertaste like saccharin, it may not taste exactly like sugar. When eaten, aspartame is metabolized into its original amino acids. Because it is so intensely sweet, relatively little of it is needed to sweeten a food product, and is thus useful for reducing the number of calories in a product.

    The safety of aspartame has been studied extensively since its discovery with research that includes animal studies, clinical and epidemiological research, and postmarketing surveillance,[9] with aspartame being a rigorously tested food ingredient.[10] Although aspartame has been subject to claims against its safety,[11] multiple authoritative reviews have found it to be safe for consumption at typical levels used in food manufacturing.[9][11][12][13] Aspartame has been deemed safe for human consumption by over 100 regulatory agencies in their respective countries,[13] including the UK Food Standards Agency,[7] the European Food Safety Authority (EFSA),[8] and Health Canada.[14]

    Cyclamate

    [edit]

    Main article: Cyclamate

    Cyclamate-based sugar substitute sold in Canada (Sweet’N Low)

    In the United States, the Food and Drug Administration banned the sale of cyclamate in 1969 after lab tests in rats involving a 10:1 mixture of cyclamate and saccharin (at levels comparable to humans ingesting 550 cans of diet soda per day) caused bladder cancer.[15] This information, however, is regarded as “weak” evidence of carcinogenic activity,[16] and cyclamate remains in common use in many parts of the world, including Canada, the European Union and Russia.[17][18]

    Mogrosides (monk fruit)

    [edit]

    Main article: Siraitia grosvenorii

    Mogrosides, extracted from monk fruit (which is commonly also called luǒ hán guò), are recognized as safe for human consumption and are used in commercial products worldwide.[19][20] As of 2017, it is not a permitted sweetener in the European Union,[21] although it is allowed as a flavor at concentrations where it does not function as a sweetener.[20] In 2017, a Chinese company requested a scientific review of its mogroside product by the European Food Safety Authority.[22] It is the basis of McNeil Nutritionals‘s tabletop sweetener Nectresse in the United States and Norbu Sweetener in Australia.[23]

    Saccharin

    [edit]

    Main article: Saccharin

    Saccharin, historical wrapping – Sugar Museum, Berlin

    Apart from sugar of lead (used as a sweetener in ancient through medieval times before the toxicity of lead was known), saccharin was the first artificial sweetener and was originally synthesized in 1879 by Remsen and Fahlberg. Its sweet taste was discovered by accident. It had been created in an experiment with toluene derivatives. A process for the creation of saccharin from phthalic anhydride was developed in 1950, and, currently, saccharin is created by this process as well as the original process by which it was discovered. It is 300 to 500 times sweeter than sucrose and is often used to improve the taste of toothpastes, dietary foods and dietary beverages. The bitter aftertaste of saccharin is often minimized by blending it with other sweeteners.

    Fear about saccharin increased when a 1960 study showed that high levels of saccharin may cause bladder cancer in laboratory rats. In 1977, Canada banned saccharin as a result of the animal research. In the United States, the FDA considered banning saccharin in 1977, but Congress stepped in and placed a moratorium on such a ban. The moratorium required a warning label and also mandated further study of saccharin safety.

    Subsequently, it was discovered that saccharin causes cancer in male rats by a mechanism not found in humans. At high doses, saccharin causes a precipitate to form in rat urine. This precipitate damages the cells lining the bladder (urinary bladder urothelial cytotoxicity) and a tumor forms when the cells regenerate (regenerative hyperplasia). According to the International Agency for Research on Cancer, part of the World Health Organization, “This mechanism is not relevant to humans because of critical interspecies differences in urine composition”.[24]

    In 2001, the United States repealed the warning label requirement, while the threat of an FDA ban had already been lifted in 1991. Most other countries also permit saccharin, but restrict the levels of use, while other countries have outright banned it.

    The EPA has removed saccharin and its salts from their list of hazardous constituents and commercial chemical products. In a 14 December 2010 release, the EPA stated that saccharin is no longer considered a potential hazard to human health.

    Steviol glycosides (stevia)

    [edit]

    Main article: Stevia

    Stevia is a natural non-caloric sweetener derived from the Stevia rebaudiana plant, and is manufactured as a sweetener.[25] It is indigenous to South America, and has historically been used in Japanese food products, although it is now common internationally.[25] In 1987, the FDA issued a ban on stevia because it had not been approved as a food additive, although it continued to be available as a dietary supplement.[26] After being provided with sufficient scientific data demonstrating safety of using stevia as a manufactured sweetener, from companies such as Cargill and Coca-Cola, the FDA gave a “no objection” status as generally recognized as safe (GRAS) in December 2008 to Cargill for its stevia product, Truvia, for use of the refined stevia extracts as a blend of rebaudioside A and erythritol.[27][28][29] In Australia, the brand Vitarium uses Natvia, a stevia sweetener, in a range of sugar-free children’s milk mixes.[30]

    In August 2019, the FDA placed an import alert on stevia leaves and crude extracts—which do not have GRAS status—and on foods or dietary supplements containing them, citing concerns about safety and potential for toxicity.[31]

    Sucralose

    [edit]

    Main article: Sucralose

    The world’s most commonly used artificial sweetener,[17] sucralose is a chlorinated sugar that is about 600 times sweeter than sugar. It is produced from sucrose when three chlorine atoms replace three hydroxyl groups. It is used in beveragesfrozen dessertschewing gumbaked goods and other foods. Unlike other artificial sweeteners, it is stable when heated and can therefore be used in baked and fried goods. Discovered in 1976, the FDA approved sucralose for use in 1998.[32]

    Most of the controversy surrounding Splenda, a sucralose sweetener, is focused not on safety but on its marketing. It has been marketed with the slogan, “Splenda is made from sugar, so it tastes like sugar.” Sucralose is prepared from either of two sugars, sucrose or raffinose. With either base sugar, processing replaces three oxygen-hydrogen groups in the sugar molecule with three chlorine atoms.[33] The “Truth About Splenda” website was created in 2005 by the Sugar Association, an organization representing sugar beet and sugar cane farmers in the United States,[34] to provide its view of sucralose. In December 2004, five separate false-advertising claims were filed by the Sugar Association against Splenda manufacturers Merisant and McNeil Nutritionals for claims made about Splenda related to the slogan, “Made from sugar, so it tastes like sugar.” French courts ordered the slogan to no longer be used in France, while in the U.S., the case came to an undisclosed settlement during the trial.[33]

    There are few safety concerns pertaining to sucralose[35] and the way sucralose is metabolized suggests a reduced risk of toxicity. For example, sucralose is extremely insoluble in fat and, thus, does not accumulate in fatty tissues; sucralose also does not break down and will dechlorinate only under conditions that are not found during regular digestion (i.e., high heat applied to the powder form of the molecule).[36] Only about 15% of sucralose is absorbed by the body and most of it passes out of the body unchanged.[36]

    In 2017, sucralose was the most common sugar substitute used in the manufacture of foods and beverages; it had 30% of the global market, which was projected to be valued at $2.8 billion by 2021.[17]

    Sugar alcohol

    [edit]

    Main article: Sugar alcohol

    Sugar alcohols, or polyols, are sweetening and bulking ingredients used in the manufacturing of foods and beverages, particularly sugar-free candies, cookies and chewing gums.[37][38] As a sugar substitute, they typically are less-sweet and supply fewer calories (about a half to one-third fewer calories) than sugar. They are converted to glucose slowly, and do not spike increases in blood glucose.[37][38][39]

    Sorbitolxylitolmannitolerythritol and lactitol are examples of sugar alcohols.[38] These are, in general, less sweet than sucrose, but have similar bulk properties and can be used in a wide range of food products.[38] The sweetness profile may be altered during manufacturing by mixing with high-intensity sweeteners.

    Sugar alcohols are carbohydrates with a biochemical structure partially matching the structures of sugar and alcohol, although not containing ethanol.[38][40] They are not entirely metabolized by the human body.[40] The unabsorbed sugar alcohols may cause bloating and diarrhea due to their osmotic effect, if consumed in sufficient amounts.[41] They are found commonly in small quantities in some fruits and vegetables, and are commercially manufactured from different carbohydrates and starch.[38][40][42]

    Production

    [edit]

    The majority of sugar substitutes approved for food use are artificially synthesized compounds. However, some bulk plant-derived sugar substitutes are known, including sorbitolxylitol and lactitol. As it is not commercially profitable to extract these products from fruits and vegetables, they are produced by catalytic hydrogenation of the appropriate reducing sugar. For example, xylose is converted to xylitol, lactose to lactitol, and glucose to sorbitol.

    Use

    [edit]

    Reasons for use

    [edit]

    Sugar substitutes are used instead of sugar for a number of reasons, including:

    Dental care

    [edit]

    Carbohydrates and sugars usually adhere to the tooth enamel, where bacteria feed upon them and quickly multiply.[43] The bacteria convert the sugar to acids that decay the teeth. Sugar substitutes, unlike sugar, do not erode teeth as they are not fermented by the microflora of the dental plaque. A sweetener that may benefit dental health is xylitol, which tends to prevent bacteria from adhering to the tooth surface, thus preventing plaque formation and eventually tooth decay. A Cochrane review, however, found only low-quality evidence that xylitol in a variety of dental products actually has any benefit in preventing tooth decay in adults and children.[43]

    Dietary concerns

    [edit]

    Sugar substitutes are a fundamental ingredient in diet drinks to sweeten them without adding calories. Additionally, sugar alcohols such as erythritolxylitol and sorbitol are derived from sugars. In the United States, six high-intensity sugar substitutes have been approved for use: aspartamesucraloseneotameacesulfame potassium (Ace-K), saccharin and advantame.[3] Food additives must be approved by the FDA,[3] and sweeteners must be proven as safe via submission by a manufacturer of a GRAS document.[44] The conclusions about GRAS are based on a detailed review of a large body of information, including rigorous toxicological and clinical studies.[44] GRAS notices exist for two plant-based, high-intensity sweeteners: steviol glycosides obtained from stevia leaves (Stevia rebaudiana) and extracts from Siraitia grosvenorii, also called luo han guo or monk fruit.[3]

    Glucose metabolism

    [edit]

    • Diabetes mellitus – People with diabetes limit refined sugar intake to regulate their blood sugar levels. Many artificial sweeteners allow sweet-tasting food without increasing blood glucose. Others do release energy but are metabolized more slowly, preventing spikes in blood glucose. A concern, however, is that overconsumption of foods and beverages made more appealing with sugar substitutes may increase risk of developing diabetes.[45] A 2014 systematic review showed that a 330ml/day (an amount little less than the standard U.S can size) consumption of artificially sweetened beverages lead to increased risks of type 2 diabetes.[46] A 2015 meta-analysis of numerous clinical studies showed that habitual consumption of sugar sweetened beverages, artificially sweetened beverages, and fruit juice increased the risk of developing diabetes, although with inconsistent results and generally low quality of evidence.[45] A 2016 review described the relationship between non-nutritive sweeteners as inconclusive.[46] A 2020 Cochrane systematic review compared several non-nutritive sweeteners to sugar, placebo and a nutritive low-calorie sweetener (tagatose), but the results were unclear for effects on HbA1c, body weight and adverse events.[47] The studies included were mainly of very low certainty and did not report on health-related quality of life, diabetes complications, all-cause mortality or socioeconomic effects.[47]
    • Reactive hypoglycemia – Individuals with reactive hypoglycemia will produce an excess of insulin after quickly absorbing glucose into the bloodstream. This causes their blood glucose levels to fall below the amount needed for proper body and brain function. As a result, like diabetics, they must avoid intake of high-glycemic foods like white bread, and often use artificial sweeteners for sweetness without blood glucose.

    Cost and shelf life

    [edit]

    Many sugar substitutes are cheaper than sugar in the final food formulation. Sugar substitutes are often lower in total cost because of their long shelf life and high sweetening intensity. This allows sugar substitutes to be used in products that will not perish after a short period of time.[48]

    Acceptable daily intake levels

    [edit]

    In the United States, the FDA provides guidance for manufacturers and consumers about the daily limits for consuming high-intensity sweeteners, a measure called acceptable daily intake (ADI).[3] During their premarket review for all of the high-intensity sweeteners approved as food additives, the FDA established an ADI defined as an amount in milligrams per kilogram of body weight per day (mg/kg bw/d), indicating that a high-intensity sweetener does not cause safety concerns if estimated daily intakes are lower than the ADI.[49] The FDA states: “An ADI is the amount of a substance that is considered safe to consume each day over the course of a person’s lifetime.” For stevia (specifically, steviol glycosides), an ADI was not derived by the FDA, but by the Joint Food and Agricultural Organization/World Health Organization Expert Committee on Food Additives, whereas an ADI has not been determined for monk fruit.[49]

    For the sweeteners approved as food additives, the ADIs in milligrams per kilogram of body weight per day are:[49]

    Mouthfeel

    [edit]

    If the sucrose, or other sugar, that is replaced has contributed to the texture of the product, then a bulking agent is often also needed. This may be seen in soft drinks or sweet teas that are labeled as “diet” or “light” that contain artificial sweeteners and often have notably different mouthfeel, or in table sugar replacements that mix maltodextrins with an intense sweetener to achieve satisfactory texture sensation.

    Sweetness intensity

    [edit]

    The FDA has published estimates of sweetness intensity, called a multiplier of sweetness intensity (MSI) as compared to table sugar.

    Plant-derived

    [edit]

    This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.
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    The sweetness levels and energy densities are in comparison to those of sucrose.

    NameRelative sweetness
    to sucrose by weight
    Sweetness by food energyEnergy densityNotes
    Brazzein1250Protein
    Curculin1250Protein; also changes the taste of water and sour solutions to sweet
    Erythritol0.65140.05
    Fructooligosaccharide0.4
    Glycyrrhizin40
    Glycerol0.60.551.075E422
    Hydrogenated starch hydrolysates0.650.850.75
    Inulin0.1
    Isomalt0.551.10.5E953
    Isomaltooligosaccharide0.5
    Isomaltulose0.5
    Lactitol0.40.80.5E966
    Mogroside mix300
    Mabinlin100Protein
    Maltitol0.8251.70.525E965
    Maltodextrin0.15
    Mannitol0.51.20.4E421
    MiraculinA protein that does not taste sweet by itself but modifies taste receptors to make sour foods taste sweet temporarily
    Monatin3,000Sweetener isolated from the plant Sclerochiton ilicifolius
    Monellin1,400Sweetening protein in serendipity berries
    Osladin500
    Pentadin500Protein
    Polydextrose0.1
    Psicose0.7
    Sorbitol0.60.90.65Sugar alcohol, E420
    Stevia250Extracts known as rebiana, rebaudioside A, a steviol glycoside; commercial products: TruviaPureViaStevia In The Raw
    Tagatose0.922.40.38Monosaccharide
    Thaumatin2,000Protein; E957
    Xylitol1.01.70.6E967

    Artificial

    [edit]

    This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed.
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    NameRelative sweetness to
    sucrose by weight
    Trade nameApprovalNotes
    Acesulfame potassium200[49]NutrinovaFDA 1988E950 Hyet Sweet
    Advantame20,000[49]FDA 2014E969
    Alitame2,000approved in Mexico, Australia, New Zealand and ChinaPfizer
    Aspartame200[49]NutraSweetEqualFDA 1981, EU-wide 1994E951 Hyet Sweet
    Salt of aspartame-acesulfame350TwinsweetE962
    Carrelame200,000
    Sodium cyclamate40FDA banned 1969, approved in EU and CanadaE952, Abbott
    Dulcin250FDA banned 1950
    Glucin300
    Lugduname220,000–300,000
    Neohesperidin dihydrochalcone1650EU 1994E959
    Neotame7,000–13,000[49]NutraSweetFDA 2002E961
    P-40004,000FDA banned 1950
    Saccharin200–700[49]Sweet’N LowFDA 1958, Canada 2014E954
    Sucralose600[49]Kaltame, SplendaCanada 1991, FDA 1998, EU 2004E955, Tate & Lyle

    Sugar alcohols

    [edit]

    NameRelative sweetness
    to sucrose by weight
    Food energy (kcal/g)Sweetness per food energy,relative to sucroseFood energy for equalsweetness, relative to sucrose
    Arabitol0.70.2147.1%
    Erythritol0.80.21156.7%
    Glycerol0.64.30.56180%
    HSH0.4–0.93.00.52–1.283–190%
    Isomalt0.52.01.0100%
    Lactitol0.42.00.8125%
    Maltitol0.92.11.759%
    Mannitol0.51.61.283%
    Sorbitol0.62.60.92108%
    Xylitol1.02.41.662%
    Compare with:Sucrose1.04.01.0100%

    Research

    [edit]

    Body weight

    [edit]

    Reviews and dietetic professionals have concluded that moderate use of non-nutritive sweeteners as a safe replacement for sugars may help limit energy intake and assist with managing blood glucose and weight.[51][52][53] Other reviews found that the association between body weight and non-nutritive sweetener usage is inconclusive.[46][54][55] Observational studies tend to show a relation with increased body weight, while randomized controlled trials instead show a little causal weight loss.[46][54][55] Other reviews concluded that use of non-nutritive sweeteners instead of sugar reduces body weight.[51][52]

    Obesity

    [edit]

    There is little evidence that artificial sweeteners directly affect the onset and mechanisms of obesity, although consuming sweetened products is associated with weight gain in children.[56][57] Some preliminary studies indicate that consumption of products manufactured with artificial sweeteners is associated with obesity and metabolic syndrome, decreased satiety, disturbed glucose metabolism, and weight gain, mainly due to increased overall calorie intake, although the numerous factors influencing obesity remain poorly studied, as of 2021.[56][57][58][59]

    Cancer

    [edit]

    Multiple reviews have found no link between artificial sweeteners and the risk of cancer.[46][60][61][62] FDA scientists have reviewed scientific data regarding the safety of aspartame and different sweeteners in food, concluding that they are safe for the general population under common intake conditions.[63]

    Mortality

    [edit]

    High consumption of artificially sweetened beverages was associated with a 12% higher risk of all-cause mortality and a 23% higher risk of cardiovascular disease (CVD) mortality in a 2021 meta-analysis.[64] A 2020 meta-analysis found a similar result, with the highest consuming group having a 13% higher risk of all-cause mortality and a 25% higher risk of CVD mortality.[65] However, both studies also found similar or greater increases in all-cause mortality when consuming the same amount of sugar-sweetened beverages.

    Non-nutritive sweeteners vs sugar

    [edit]

    Further information: Sugar § Health effects

    The World Health Organization does not recommend using non-nutritive sweeteners to control body weight, based on a 2022 review that could only find small reductions in body fat and no effect on cardiometabolic risk.[66] It recommends fruit or non-sweetened foods instead.

  • Air fresheners

    Air fresheners are products designed to reduce unwanted odors in indoor spaces, to introduce pleasant fragrances, or both. They typically emit fragrance to mask odors but may use other methods of action such as absorbing, bonding to, or chemically altering compounds in the air that produce smells, killing organisms that produce smells, or disrupting the sense of smell to reduce perception of unpleasant smells.

    There are many different types of air fresheners that deliver their active ingredients in different ways, including sprays, candles, reed diffusers, scented beads, gels, passive and active evaporating diffusers, atomizers, automatically timed metered aerosol dispensers, electric fan air fresheners, and plug-ins. Air fresheners are used in domestic and commercial settings and in both small and large spaces. Some air fresheners are produced for specific spaces and odors, such as car fresheners and urinal deodorizer blocks. Some air fresheners contain ingredients that provoke allergy and asthma symptoms or are toxic. Air freshening also involves the use of organic and everyday household items.

    History

    [edit]

    Fragrances have been used to mask odors since antiquity. A variety of methods and compounds have been used over the past two millennia for their abilities to create pleasant aromas or eliminate unpleasant odors in indoor spaces. These were often linked with spiritual or religious practices (e.g. the use of incense),[1] or with concepts of health and hygiene. Consumer products for air freshening began to emerge in the late 1800s[citation needed] which coincided with the arrival of the first synthetically produced fragrances.[2] However, air freshening consumer products first gained wider popularity in the 1940s.

    Air Wick print advertisement, 1957

    In 1939, Air Wick launched in the United States, initially producing liquid air fresheners in a variety of fragrances, which worked by evaporation with the help of a wick.[3] The products claimed to kill odors, not just mask them, by using chlorophyll. As early as 1953, scientists were questioning whether chlorophyll, at the time popular as a body deodorizer or for use on wounds, really acted as a space deodorizer.[4][5][6] From 1947 to 1951, the company sold 7 million dollars’ worth of these and other types of air fresheners.[6]

    The first fan-operated air freshener product was invented in 1946 and released by the company Surco under the brand Air-Scent in 1948.[7][8][9]

    In the United States, commercial aerosol sprays were introduced in 1948, [citation needed] based on what had been a military technology for dispensing insecticides.[10] The product[which?] delivered a fine mist of aroma compounds that would remain suspended in the air for an extended period of time.

    In the 1950s, many companies began to add chemicals that counteract odors to their fragrance formulas. These chemicals, intended to neutralize or destroy odors, included unsaturated esters, pre-polymers, and long-chain aldehydes.

    In the 1980s, the air freshener market shifted back away from aerosols due to concerns over the destruction of the ozone layer by chlorofluorocarbons (CFCs) which were used as a propellant. Many other air freshener delivery methods have become popular since, including under the seat wafer air fresheners, scented candles, reed diffuserspotpourri, and heat release products.

    Basic principles

    [edit]

    Air fresheners introduce fragrance into the air of interior spaces either as droplets which transition to vapor, or as the molecules of fragrance ingredients directly evaporating from a source. Fragrance diffuses into the air to mask other odors or to introduce a specific odor.

    Mechanisms of odor control

    [edit]

    A basic gel fragrance air freshener
    An automatic air freshener

    Mechanisms for the control of indoor airborne odors can be grouped into various different classes:

    Delivery: continuous vs. instant action

    [edit]

    A reed diffuser

    Delivery of the above air freshener mechanisms falls into two broad categories: continuous action and instant action.

    Continuous action products include scented candles and devices which use a candle flame or some other heat source to heat and vaporize a fragrance formulation, incense burners, wall plug-ins which either use piezoelectric technology to aerosolize fragrance or heat to vaporize it, fragrance impregnated gels which release fragrance as the gel evaporates sometimes with the help of an electric fan, wick and reed diffusers which release fragrance by evaporation from fragrance-soaked wicks or wooden reeds; and fragrance impregnated materials like floor wax, paper, plastics, wood which release fragrance by off gassing; and lastly nebulization systems which convert liquid fragrances into a vapor in a cold process without the use of heat.

    Instant action systems are mainly aerosol or atomizer sprays. The aerosol spray uses a propellant and fragrance packaged under pressure in a sealed metal container with a valve which is opened by pressing down a button which contains a spray nozzle – the actuator. When the container’s valve is opened by pressing the actuator, fragrance is forced through the spray nozzle located inside the actuator to create a mist of droplets containing fragrance. These droplets are 30 to 50 micrometres in diameter. A recently developed alternative, the “bag-on-valve” aerosol, places the air freshener inside a bag in the can. The can is filled with pressurised air which squeezes the bag and pushes out the product when the actuator is pressed.[12] An atomizer operates in a similar fashion except that the actuator is a pump which when pressed a few times creates the pressure to aspirate the fragrance from the container through a tube into the actuator and spray nozzle. Because the container is not constantly under pressure it may be made of glass or plastic as well as metal. The mist created contains droplets 50 to 150 micrometres in diameter.[citation needed]

    Ingredients

    [edit]

    In addition to the fragrances, adsorbents, oxidizers, surfactants, and disinfectants listed above, air fresheners can also contain aerosol propellantspreservatives, and solvents.

    Fragrances

    [edit]

    Air fresheners use both synthesized and organically occurring fragrances. Common fragrances used include lyral and citronellal. Preparations often include terpenes such as limonene.

    Aerosol propellants

    [edit]

    A propellant is usually a liquid gas substance used to physically propel the product out of an aerosol spray. The substance chosen needs to be a gas that turns to liquid when pressurized with a relatively low amount of pressure, safe for domestic use. The propellant is a liquid when under pressure in the can, but maintains the pressure in the can (and thereby its spraying ability) by turning partially back to a gas to fill any empty space. Less common compressed gas propellants work similarly but maintain pressure by filling the empty space without liquefying. The propellant in a true aerosol is mixed with the air freshener, so it must also not react with the product. Sometimes, multiple propellants are combined.

    CFCs were once popular propellants but are no longer widely used because of their damaging effects on the ozone layer and resulting bans. Current propellants used in air freshener sprays include:

    Note that while bag-on-valve systems may use compressed airnitrogen or carbon dioxide or other substances to squeeze the air freshener from the bag, these are not strictly ingredients because they are not mixed with the air freshener, and remain in the can.

    Preservatives

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    Preservatives prevent the decomposition of the product or the growth of microorganisms in it. These can include:

    Solvents, emulsifiers and surfactants

    [edit]

    These are substances that help other ingredients mix together, either by dissolving or emulsifying.

    Solvents used in air fresheners include ethanolmineral oil, or glycol ethers such as 2-butoxyethanol and trideceth-4.

    Toxicity and hazards

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    There have been various concerns about air fresheners having adverse health effects, due to factors including harmful ingredients, secondary substances formed by the chemical interactions of ingredients with other substances, allergy-provoking ingredients, misuse, and accidental injury.

    Harmful ingredients and secondary substances

    [edit]

    Many air fresheners employ carcinogensvolatile organic compounds and known toxins such as phthalate esters in their formulas.[22] A Natural Resources Defense Council (NRDC) study of 13 common household air fresheners found that most of the surveyed products contain chemicals that can aggravate asthma and affect reproductive development. The NRDC called for more rigorous supervision of the manufacturers and their products, which are widely assumed to be safe:

    The study assessed scented sprays, gels, and plug-in air fresheners. Independent lab testing confirmed the presence of phthalates, or hormone-disrupting chemicals that may pose a particular health risk to babies and young children, in 12 of the 14 products—including those marked ‘all natural.’ None of the products had these chemicals listed on their labels.[23]

    On September 19, 2007, along with the Sierra Club, Alliance for Healthy Homes, and the National Center for Healthy Housing, the NRDC filed a petition with the U.S. Environmental Protection Agency and the Consumer Product Safety Commission to report the findings.[24]

    Research at the University of Colorado at Boulder revealed the carcinogenic nature of paradichlorobenzene (PCDB) and naphthalene, present in some types of air fresheners. The pesticide substances were mainly used in mothballs but also in room sprays and toilet rim blocks.[25][26]

    The University of Bristol‘s Avon Longitudinal Study of Parents and Children (ALSPAC) found that exposure to volatile organic compounds through frequent use of air fresheners and other aerosols in the home was found to correlate with increased earaches and diarrhea in infants, and with increased depression and headaches in their mothers.[27][28]

    In 2008, Anne C. Steinemann of the University of Washington published a study of top-selling air fresheners and laundry products.[29][30] She found that all products tested gave off chemicals regulated as toxic or hazardous under federal laws, including carcinogens with no safe exposure level, but none of these chemicals were listed on any of the product labels or material safety data sheets. Chemicals included acetone, the active ingredient in paint thinner and nail-polish remover; chloromethane, a neurotoxicant and respiratory toxicant; and acetaldehyde and 1,4-dioxane, both carcinogens. A plug-in air freshener contained more than 20 different volatile organic compounds, with more than one-third classified as toxic or hazardous under federal laws. Even air fresheners called “organic,” “green,” or with “essential oils” emitted hazardous chemicals, including carcinogens.

    A report issued in 2005 by the Bureau Européen des Unions de Consommateurs (BEUC) found that many air freshener products emit allergens and toxic air pollutants including benzeneformaldehydeterpenesstyrenephthalate esters, and toluene.[31][32]

    In the United States, since 2020 air fresheners (as well as cleaning solutions and products used to clean cars) have been required to list any of their ingredients which are on California’s list of 2,300 harmful chemicals, based on a California law passed in 2017.[33] A California study in 2006 found that the prominent products of the reaction of terpenes found in air fresheners with ozone included formaldehyde, hydroxyl radical, and secondary ultrafine particles.[34] It is not clear if manufacturers will need to list such chemicals which are not ingredients, but form during deployment and are thus able to affect human health.

    Allergens and irrtants

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    In 2009, Stanley M. Caress of the University of West Georgia and Anne C. Steinemann of the University of Washington published results from two national epidemiological studies of health effects from exposure to air fresheners. They found that nearly 20 percent of the general population and 34 percent of asthmatics report headaches, breathing difficulties, or other health problems when exposed to air fresheners or deodorizers.[35]

    Misuse and accidental injury

    [edit]

    Air freshener aerosols with certain propellants are susceptible to misuse as an inhalant. Air fresheners have also been used to cause aerosol burn. In rare cases aerosol burns are reported to have been caused by air freshener canisters exploding.[36]

    Alternatives to fragranced air fresheners

    [edit]

    Removing the source of an unpleasant odor will decrease the chance that people will smell it. Ventilation is also important to maintaining indoor air quality and can aid in eliminating unpleasant odors. Simple cleaners such as white vinegar and baking soda, as well as natural adsorbents like activated charcoal and zeolite, are effective at removing odors. Other solutions are adapted to different types of odor. Some house plants may also aid in the removal of toxic substances from the air in building interiors.