Optical brighteners are a type of chemical used to enhance the white or bright appearance of fabrics. They're often used during the manufacturing process of new white or lightly coloured fabrics, and are commonly added to laundry detergents to maintain the appearance of brightness after successive washes. Because optical brighteners are designed to stick to clothes, they end up being in contact with our skin for prolonged periods of time. While currently there's limited evidence that optical brighteners in laundry detergents pose a risk to human health, they're known to be made from non-renewable petrochemicals and can be slow to biodegrade - both of which have environmental consequences. We prefer to leave them out of our products.
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‘Optical brighteners’ is a general term for a group of chemicals, also known by other names such as ‘Fluorescent Whitening Agents (FWAs)’. They're used in several industries, including fabrics, laundry detergents, paper, plastics and some cosmetics, and are derived from non-renewable sources such as pyrene (from coal tar). Optical brighteners can be considered as a type of dye, and they work by absorbing UV (ultraviolet) light and reflecting blue light. This makes materials look less yellow to the human eye, and thus appear whiter, brighter and ‘cleaner’.
Regarding the safety of optical brighteners, the current evidence generally points to low risk to human health in this context (some people may have sensitivities), but some environmental impacts that require further study. A risk assessment by the Human & Environmental Risk Assessment (HERA) Project reviewed optical brightener ‘Fluorescent Brightener FWA-1’ in household laundry products and concluded it was safe for consumers. An equivalent assessment was undertaken for ‘Fluorescent Brightener FWA-5’, reaching a similar conclusion. Looking at the environmental impacts, both of these optical brighteners are listed by the European Chemical Agency (ECHA) as ‘not readily biodegradable’, with low potential for bioaccumulation but ‘acute’ or ‘inconclusive’ aquatic toxicity. Given these known and potential impacts, we prefer to leave optical brighteners out of our products.
Other names: Optical Brightening Agents (OBAs), Optical Whiteners, Fluorescent Brightening Agents, Fluorescent Brighteners, Fluorescent Optical Brighteners, Fluorescent Whitening Agents (FWAs), Fluorescent White Dyes, Organic Fluorescent Dyes
Chemical class: Colour Additives - Miscelaneous
Chemical structure depicted: Fluorescent brightener 71 and Fluorescent brightener 351
REFERENCES
James Burckett St. Laurent, Francesco de Buzzaccarini, Karen De Clerck, Hugo Demeyere, Regine Labeque, Rainer Lodewick, Lieva van Langenhove, B.1.I - Laundry Cleaning of Textiles, Editor(s): Ingegärd Johansson, P. Somasundaran, Handbook for Cleaning/Decontamination of Surfaces, Elsevier Science B.V., , Pages 57-102, ISBN , https://doi.org/10./B978--0/-6.
I. Mangas, E. Vilanova, Pyrene, Editor(s): Philip Wexler, Encyclopedia of Toxicology (Third Edition), Academic Press, , Pages -, ISBN , https://doi.org/10./B978-0-12--3.-2.
HERA. (). Human & Environmental Risk Assessment on ingredients of European household cleaning products. Substance: Fluorescent Brightener FWA-1 (CAS -02-1). https://www.heraproject.com/files/23-F-04-HERA-FWA1(Version%203_1%20).pdf
HERA. (). Human & Environmental Risk Assessment on ingredients of European household cleaning products. Substance: Fluorescent Brightener FWA-5 (CAS -41-8). https://www.heraproject.com/files/11-F-04-HERA%20FWA5%20Full%20web%20wd.pdf
European Chemicals Agency (). Disodium 4,4'-bis[(4-anilino-6-morpholino-1,3,5-triazin-2-yl)amino]stilbene-2,2'-disulphonate. EC number: 240-245-2 | CAS number: -02-1. https://echa.europa.eu/registration-dossier/-/registered-dossier//1/1
For more information, please visit Ogilvy.
European Chemicals Agency (). Disodium 2,2'-([1,1'-biphenyl]-4,4'-diyldivinylene)bis(benzenesulphonate). EC number: 248-421-0 | CAS number: -41-8. https://echa.europa.eu/registration-dossier/-/registered-dossier//5/3/1
https://echa.europa.eu/web/guest/legal-notice
National Center for Biotechnology Information (). PubChem Compound Summary for CID , C.I. Fluorescent brightener 260. https://pubchem.ncbi.nlm.nih.gov/compound/C.I.-Fluorescent-brightener-260
National Center for Biotechnology Information (). PubChem Compound Summary for CID . https://pubchem.ncbi.nlm.nih.gov/compound/
Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), are chemical compounds that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the electromagnetic spectrum, and re-emit light in the blue region (typically 420-470 nm) through the phenomenon of fluorescence. These additives are often used to enhance the appearance of color of fabric and paper, causing a "whitening" effect; they make intrinsically yellow/orange materials look less so, by compensating the deficit in blue and purple light reflected by the material, with the blue and purple optical emission of the fluorophore.[1]
The most common classes of compounds with this property are the stilbenes, e.g., 4,4′-diamino-2,2′-stilbenedisulfonic acid. Older, non-commercial fluorescent compounds include umbelliferone, which absorbs in the UV portion of the spectrum and re-emit it in the blue portion of the visible spectrum. A white surface treated with an optical brightener can emit more visible light than that which shines on it, making it appear brighter. The blue light emitted by the brightener compensates for the diminishing blue of the treated material and changes the hue away from yellow or brown and toward white.[2]
Approximately 400 brightener types are listed in the international Colour Index database,[4] but fewer than 90 are produced commercially, and only a handful are commercially important. The Colour Index Generic Names and Constitution Numbers can be assigned to a specific substance. However, some are duplicated, since manufacturers apply for the index number when they produce it. The global OBA production for paper, textiles, and detergents is dominated by just a few di- and tetra-sulfonated triazole-stilbenes and a di-sulfonated stilbene-biphenyl derivatives. The stilbene derivatives are subject to fading upon prolonged exposure to UV, due to the formation of optically inactive cis-stilbenes. They are also degraded by oxygen in air, like most dye colorants. All brighteners have extended conjugation and/or aromaticity, allowing for electron movement. Some non-stilbene brighteners are used in more permanent applications such as whitening synthetic fiber.
Brighteners can be "boosted" by the addition of certain polyols, such as high molecular weight polyethylene glycol or polyvinyl alcohol. These additives increase the visible blue light emissions significantly. Brighteners can also be "quenched". Excess brightener will often cause a greening effect as emissions start to show above the blue region in the visible spectrum.
Brighteners are commonly added to laundry detergents to make the clothes appear cleaner. Normally cleaned laundry appears yellowish, which consumers do not like.[2] Optical brighteners have replaced bluing which was formerly used to produce the same effect.
Brighteners are used in many papers, especially high brightness papers, resulting in their strongly fluorescent appearance under UV illumination. Paper brightness is typically measured at 457 nm, well within the fluorescent activity range of brighteners.[5] Paper used for banknotes does not contain optical brighteners, so a common method for detecting counterfeit notes is to check for fluorescence.
Optical brighteners have also found use in cosmetics. One application is to formulas for washing and conditioning grey or blonde hair, where the brightener can not only increase the luminance and sparkle of the hair, but can also correct dull, yellowish discoloration without darkening the hair. Some advanced face and eye powders contain optical brightener microspheres that brighten shadowed or dark areas of the skin, such as "tired eyes".
End uses of optical brighteners include:
From around to , chemical brighteners were used by many Chinese farmers to enhance the appearance of their white mushrooms. This illegal use was mostly eliminated by the Chinese Ministry of Agriculture.[6]