UV filters are individual compounds or mixtures to prevent ultraviolet (UV) light from getting through. UV filters are used in sunscreens to protect skin or in photography to reduce the level of ultraviolet light that strikes the recording medium.
Historically, photographic films were mostly sensitive to UV light, which caused haziness or fogginess, and in color films a bluish hue. Therefore, as a standard, a UV (blocking) filter was used, transparent to visible light while filtering out shorter ultraviolet wavelengths. However, newer photographic film and digital cameras are highly insensitive to UV wavelengths. UV filters are sometimes referred to as L37 or L39 filters, depending on the wavelengths of light that they filter out; an L37 filter removes ultraviolet light with a wavelength shorter than 370 nm, whereas an L39 filter eliminates light with a wavelength shorter than 390 nm.
Applications in printing and photography
UV filters span the color spectrum and are used for a wide variety of applications. Ortho Red and Deep Ortho Red lights are commonly used in diffusion transfer, typesetting films/paper other applications dealing with orthochromatic materials. Yellow Gold, Yellow, Lithostar Yellow and Fuji Yellow filters or safelights provide safe workspaces for contact proofing applications like screen printing and platemaking. Pan Green, Infrared Green and Dark Green filters or safelights are commonly used in scanning applications, work with panchromatic film and papers and x-rays.
Many photographers and cinematographers still use UV filters as a protection for their lenses' glass and coating, due to their low cost and lack of effect on the exposure of the shot. However, UV filters (in particular filters lacking optical coating) may introduce lens flare and have an adverse impact on contrast and sharpness, especially when a strong light source is present.
However, in photography, the term "UV filter" can be also be misused as a filter that passes UV light while blocking other wavelengths in the light spectrum, in the same way the term "IR filter" is also sometimes misused. The correct names for such filters though, are "UV pass filter" and "IR pass filter". This is a very specialized area in photography.
Applications in personal care products
Ultraviolet absorbing compounds are the main ingredients of sunscreen products and other personal care products e.g. lipsticks, shampoos and hair sprays. They are being used increasingly due to the growing concern about the UV radiation and the skin cancer. They absorb protect humans from the serious effects of the UV radiation by absorbing, reflecting or scattering it (UVA 320-400 nm and UVB 290-320 nm). The reflection and scattering effect are done by the inorganic UV filters, they are also named as the physical UV filters titaniumdioxide (TiO2) and zinc oxide (ZnO). However, the absorbing effect is accomplished by the organic UV filters which are known as chemical UV filters( mainly UVB)
|ethylexyl methoxycinnamate (OMC)||Benzophenone-3 (BP3)|
|isoamyl p-methoxycinnamate (IMC) = amiloxate||benzophenone-4 (BP4)|
|camphor benzalkonium methosulfate (CBM)||4-p-aminobenzoic acid (PABA)|
|terephtalydene dicamphor sulfonic acid (PDSA||Ethylhexyl dimethyl PABA (OD-PABA)|
|benzylidene camphor sulfonic acid (BCSA)||Homosalate (HMS)|
|polyacrylamidomethyl benzylidene camphor (PBC)(4||2-ethylhexyl salicylate (EHS)|
|Benzotriazoles||3-benzylidene camphor (3BC)|
|drometrizole trisiloxane (DRT)|
|methylene bis-benzotriazolyl tetramethylbutylpheno 1
|4-methylbenzylidene camphor (4-MBC)|
|phenylbenzimidazole sulfonic acid (PMDSA)||ethylhexyltriazone (OT)|
|disodium phenyl dibenzimidazole tetrasulfonate
|diethylhexyl butamido triazone (DBT)|
|Dybenzoyl methane derivatives||bis-ethylhexyloxyphenol methoxyphenyl triazine (EMT)|
|butyl methoxydibenzoyl methane (BM-DBM|
They are released into the environment either directly or indirectly.
They enter the environment directly through bathing activities in oceans, rivers and lakes or through industrial waste water discharge. While the indirect way involves domestic water discharge during showering, bathing or urine excretion or through waste water treatment.
Their continuous release to the environment has prompted them to be considered as a new class of pollutants. They can undergo degradation and transformation to more toxic products e.g. Avobenzone undergo transformation in presence of chlorinated disinfection products and UV radiation to substituted chlorinated phenols and acetophenones which are known for their toxicity.
Natural mechanisms of degradation
It is sunlight induced photochemical process.it is the main abiotic route for transformation of UV filters. Photolysis dissociates the organic filters into free radicals.
Photolysis can be direct or indirect. The direct way occurs when the chromophore of the organic filters absorb sunlight at certain wavelengths. The indirect pathway occurs in the presence of a photo-sensitizer. Dissolved organic matter (DOM) in the surface waters act as the photo-sensitizers and produce reactive photooxidants as hydroxyl radicals, peroxyl radicals and singlet oxygen.
Sayre et al. showed that the photolysis of sunscreen products is more complicated than the behavior of individual UV filters as shown by this example
Photoisomerization can result in products that absorb less UV light than parent compound. This was evidenced by cinnamates, salicylates, benzylidine camphorand dibenzoylmethane derivatives.
Swimming pool water is usually disinfected by chlorination, bromination, ozonation or UV radiation. Up on the presence of some UV filters as Avobenzone in the swimming pool water transformation products are produced as a result of the interaction between Avobenzone and the active chlorine and UV radiation
- Thom Hogan. "Filtration 101". bythom.com. Retrieved 13 October 2009.
- Díaz-Cruz, M. Silvia; Barceló, Damià (2009-06-01). "Chemical analysis and ecotoxicological effects of organic UV-absorbing compounds in aquatic ecosystems". TrAC Trends in Analytical Chemistry. Applying combinations of chemical analysis and biological effects to environmental and food samples - II. 28 (6): 708–717. doi:10.1016/j.trac.2009.03.010.
- Silvia Díaz-Cruz, M.; Llorca, Marta; Barceló, Damià; Barceló, Damià (2008-11-01). "Organic UV filters and their photodegradates, metabolites and disinfection by-products in the aquatic environment". TrAC Trends in Analytical Chemistry. Advanced MS Analysis of Metabolites and Degradation Products - I. 27 (10): 873–887. doi:10.1016/j.trac.2008.08.012.
- Santos, A. Joel M.; Miranda, Margarida S.; Esteves da Silva, Joaquim C. G. (2012-06-15). "The degradation products of UV filters in aqueous and chlorinated aqueous solutions". Water Research. 46 (10): 3167–3176. doi:10.1016/j.watres.2012.03.057.
- Trebše, Polonca; Polyakova, Olga V.; Baranova, Maria; Kralj, Mojca Bavcon; Dolenc, Darko; Sarakha, Mohamed; Kutin, Alexander; Lebedev, Albert T. (2016-09-15). "Transformation of avobenzone in conditions of aquatic chlorination and UV-irradiation". Water Research. 101: 95–102. doi:10.1016/j.watres.2016.05.067.