Damaging Effects Of UV Radiation Research Articles

NLC-Based Sunscreen Formulations with Optimized Proportion of Encapsulated and Free Filters Exhibit Enhanced UVA and UVB Photoprotection.

The topical use of sunscreens is recommended for avoiding the damaging effects of UV radiation. However, improvements are still needed in the existing products to enhance their photoprotection effectiveness and safety. This involves minimizing the use of chemical UV filters while providing enhanced and prolonged photoprotection. This work investigated novel sunscreen formulations and their UV protection effects by encapsulating Uvinul® A, Tinosorb® S, and Uvinul® T150 into nanostructured lipid carriers (NLCs) based on bacuri butter and raspberry seed oil. First, the impact of critical formulation and process parameters on NLCs' particle size was evaluated using a 22 Face Centered Central Composite Design. Then, formulations were evaluated in terms of critical quality factors, in vitro skin permeation, and in vitro and in vivo photoprotection activities. The developed NLCs-containing formulations exhibited appropriate size (122-135 nm), PdI (<0.3), encapsulation efficiency (>90%), and drug content (>80%), which were preserved for at least 90 days under different stability conditions. Moreover, these NLCs-based formulations had equivalent skin permeation to emulsion-based controls, and the addition of NLCs into sunscreen cream bases in the optimum proportion of 20% (w/w) resulted in enhanced UVA and UVB photoprotection levels, despite a 10% reduction in the total filters content. Altogether, these results describe the application of nanoencapsulated organic UV filters in innovative sunscreen formulations to achieve superior photoprotection and cosmeceutical properties.

Multiple Photolyases Protect the Marine Cyanobacterium Synechococcus from Ultraviolet Radiation.

ABSTRACTMarine cyanobacteria depend on light for photosynthesis, restricting their growth to the photic zone. The upper part of this layer is exposed to strong UV radiation (UVR), a DNA mutagen that can harm these microorganisms. To thrive in UVR-rich waters, marine cyanobacteria employ photoprotection strategies that are still not well defined. Among these are photolyases, light-activated enzymes that repair DNA dimers generated by UVR. Our analysis of genomes of 81 strains of Synechococcus, Cyanobium, and Prochlorococcus isolated from the world’s oceans shows that they possess up to five genes encoding different members of the photolyase/cryptochrome family, including a photolyase with a novel domain arrangement encoded by either one or two separate genes. We disrupted the putative photolyase-encoding genes in Synechococcus sp. strain RS9916 and discovered that each gene contributes to the overall capacity of this organism to survive UVR. Additionally, each conferred increased survival after UVR exposure when transformed into Escherichia coli lacking its photolyase and SOS response. Our results provide the first evidence that this large set of photolyases endows Synechococcus with UVR resistance that is far superior to that of E. coli, but that, unlike for E. coli, these photolyases provide Synechococcus with the vast majority of its UVR tolerance.

Pheomelanin Effect on UVB Radiation-Induced Oxidation/Nitration of l-Tyrosine.

Pheomelanin is a natural yellow-reddish sulfur-containing pigment derived from tyrosinase-catalyzed oxidation of tyrosine in presence of cysteine. Generally, the formation of melanin pigments is a protective response against the damaging effects of UV radiation in skin. However, pheomelanin, like other photosensitizing substances, can trigger, following exposure to UV radiation, photochemical reactions capable of modifying and damaging cellular components. The photoproperties of this natural pigment have been studied by analyzing pheomelanin effect on oxidation/nitration of tyrosine induced by UVB radiation at different pH values and in presence of iron ions. Photoproperties of pheomelanin can be modulated by various experimental conditions, ranging from the photoprotection to the triggering of potentially damaging photochemical reactions. The study of the photomodification of l-Tyrosine in the presence of the natural pigment pheomelanin has a special relevance, since this tyrosine oxidation/nitration pathway can potentially occur in vivo in tissues exposed to sunlight and play a role in the mechanisms of tissue damage induced by UV radiation.

Determination of Benzophenones in Water and Cosmetics Samples: A Comparison of Solid-Phase Extraction and Microextraction by Packed Sorbent Methods.

Benzophenones (BPs) are extensively used in a wide variety of cosmetic products and other materials (e.g., textiles or plastics) to avoid damaging effects of UV radiation. In the present work, we compared two extraction methods for the determination of BPs, namely, 2,4-dihydroxybenzophenone (BP-1), 2-hydroxy-4-methoxybenzophenone (BP-3) and 2,2-dihydroxy-4-methoxybenzophenone (BP-8), in water and cosmetics samples. The following extraction methods were used for the research: solid-phase extraction (SPE) and microextraction by packed sorbent (MEPS), whereas analysis was performed by gas chromatography with mass spectrometric detection. A comparison between the methods indicates that the MEPS technique(s) can be reliably used for analysis of BPs (sunscreen residue) in water samples and cosmetic samples with satisfactory results. This microextraction technique is cheap, easy, quick to implement, and consumes small amounts of solvents. On the other hand, the main advantage of the SPE method are low detection limits for the determination of BPs in water samples, i.e., from 0.034 to 0.067 µg L−1, while, for the MEPS method, LODs were at the level of 1.8–3.2 µg L−1. For both methods, the recoveries of BPs were 96–107% and 44–70% for water and cosmetics samples, respectively. The presented methods are suitable for use in cosmetics quality control and environmental pollution assessment.

UVA Exposure Combined with Glycation of the Dermis Are Two Catalysts for Skin Aging and Promotes a Favorable Environment to the Appearance of Elastosis.

Skin aging is the result of superimposed intrinsic (individual) and extrinsic (e.g., UV exposure or nutrition) aging. Previous works have reported a relationship between UV irradiation and glycation in the aging process, leading, for example, to modified radical species production and the appearance of AGEs (advanced glycosylation end products) in increasing quantities, particularly glycoxidation products like pentosidine. In addition, the colocalization of AGEs and elastosis has also been observed. We first investigated the combination of the glycation reaction and UVA effects on a reconstructed skin model to explain their cumulative biological effect. We found that UVA exposure combined with glycation had the ability to intensify the response for specific markers: for example, MMP1 or MMP3 mRNA, proteases involved in extracellular matrix degradation, or proinflammatory cytokine, IL1α, protein expression. Moreover, the association of glycation and UVA irradiation is believed to promote an environment that favors the onset of an elastotic-like phenomenon: mRNA coding for elastin, elastase, and tropoelastin expression is increased. Secondly, because the damaging effects of UV radiation in vivo might be more detrimental in aged skin than in young skin due to increased accumulation of pentosidine and the exacerbation of alterations related to chronological aging, we studied the biological effect of soluble pentosidine in fibroblasts grown in monolayers. We found that pentosidine induced upregulation of CXCL2, IL8, and MMP12 mRNA expression (inflammatory and elastotic markers, respectively). Tropoelastin protein expression (elastin precursor) was also increased. In conclusion, fibroblasts in monolayers cultured with soluble pentosidine and tridimensional in vitro skin constructs exposed to the combination of AGEs and UVA promote an inflammatory state and an alteration of the dermal compartment in relation to an elastosis-like environment.

Ultraviolet absorbance of Sphagnum magellanicum, S. fallax and S. fuscum extracts with seasonal and species-specific variation

Bryophytes, including Sphagnum, are common species in alpine and boreal regions especially on mires, where full sunlight exposes the plants to the damaging effects of UV radiation. Sphagnum species containing UV-protecting compounds might offer a biomass source for nature-based sunscreens to replace the synthetic ones. In this study, potential compounds and those linked in cell wall structures were obtained by using methanol and alkali extractions and the UV absorption of these extracts from three common Sphagnum moss species Sphagnum magellanicum, Sphagnum fuscum and Sphagnum fallax collected in spring and autumn from western Finland are described. Absorption spectrum screening (200–900 nm) and luminescent biosensor (Escherichia coli DPD2794) methodology were used to examine and compare the protection against UV radiation. Additionally, the antioxidant potential was evaluated using hydrogen peroxide scavenging (SCAV), oxygen radical absorbance capacity (ORAC) and ferric reducing absorbance capacity (FRAP). Total phenolic content was also determined using the Folin-Ciocalteu method. The results showed that methanol extractable compounds gave higher UV absorption with the used methods. Sphagnum fallax appeared to give the highest absorption in UV-B and UV-A wavelengths. In all assays except the SCAV test, the methanol extracts of Sphagnum samples collected in autumn indicated the highest antioxidant capacity and polyphenol content. Sphagnum fuscum implied the highest antioxidant capacity and phenolic content. There was low antioxidant and UV absorption provided by the alkali extracts of these three species.

Pharmacognstic evaluations of Phyllanthus emblica L.

Emblica officinalis belongs to Family Euphorbiaceae, is also called as Amla, is a tree growing in subtropical and tropical parts of China, India, Indonesia and the Malay Peninsula. It is one of the most widely used herbs in Indian traditional medicine and is a constituent of several polyherbal preparations used in Ayurveda to treat many chronic ailments including Diabetes Mellitus. It is found to have excellent anti-oxidant and free radical scavenging activity, protective effect against the damaging effects of UV radiation, inhibits nitrosation reaction in stomach, which helps to prevent stomach cancers, hepatoprotective effect, anti-mutagenic effect and reduced clastogenicity induced by various metals. It is also said to have anti-diabetic effect, hypolipidemic effect and anti-ulcerogenic effect. Hence it makes amla as an interesting natural ingredient that people can incorporate in their daily diets, which may be an effective step to manage various complications. Fresh Fruit, Dried fruit, the nut or seed, leaves, root, bark and flowers. Ripe fruits used generally fresh, dry also used. Each part has a different therapeutic value and must be prepared in its own way for maximum benefits. Amalaki fruit requires a meticulous 21-step process at low heat to maintain potency of the vitamins and minerals as well as the biological intelligence of this remarkable plant. This well-known Ayurvedic drug Amla is standardized in the present study by its pharmacognostic properties.

Nanoceria-curcumin conjugate: Synthesis and selective cytotoxicity against cancer cells under oxidative stress conditions

A water- and alcohol-soluble cerium oxide-curcumin conjugate was obtained by co-evaporation with poly(N-vinylpyrrolidone) (PVP). A nanocomposite consisting of hybrid organic-inorganic particles was stable in a wide range of pH values. Its properties were evaluated using nine cell lines: normal (MDBK, ST, Vero) and malignant (L929, T98G, HEp-2, A549, RIN-m5F, Hep G2). PVP-stabilised nanoceria was shown to inhibit autoxidation of curcumin, to enhance curcumin photostability, to promote bioaccumulation and to affect curcumin cytotoxicity and photocytotoxicity, depending on cell type, being more toxic to cancer cells in a selective manner. Under the conditions of UVA/UVC or H2O2-induced oxidative stress, the nanoceria-PVP-curcumin (NPC) conjugate was found to possess a selective cytotoxicity: it caused drastic inhibition of metabolic activity or a decrease in the total number of tumour cells, while in non-transformed cultures under the same conditions, the nanoceria-PVP-curcumin conjugate protected cells from these damaging factors. The NPC-conjugate, unlike curcumin itself, demonstrated a photosensitising effect in tumour cell cultures, while protecting non-transformed cultures from the damaging effects of UV radiation or oxidative stress. Based on the results obtained, we strongly believe that this novel hybrid material has enhanced characteristics compared to other curcumin formulations, and can be considered as a potent drug for biomedical applications, including cancer therapy.

THE RECENT UPDATE OF DEOXYARBUTIN: A SKIN DEPIGMENTATION AGENT WITH TYROSINASE INHIBITION TARGETING

Melanin is produced through the process of melanogenesis, which serves to protect the skin from the damaging effects of UV radiation. Abnormal accumulation of melanin will aesthetically disturb even interfere with health. One of the clinical manifestations of abnormal accumulation of melanin is the incidence of melasma. Some of the tyrosinase enzyme inhibitor agents most widely used as Hydroquinone, Kojic acid and Arbutin do not give satisfactory results and cause serious side effects. Hydroquinone is known to cause ochronosis exogenous and cytotoxic. Kojic acid is known to cause allergies and mutagenic, while arbutinisis is known to have cytotoxic properties lower than hydroquinone, but less satisfactory depigmentation activity. There was a compound that has been synthesized by removing the hydroxy group of arbutin, known as deoxyarbutin (4-[Tetrahydro-2H-Pyrans-2-yl) oxy] phenol). Deoxyarbutin (dA) shows Ki 10-fold is lower than hydroquinone and 350-fold is lower than arbutin. IC50dA is 17.5+0.5 µmol/l, while the IC50 hydroquinone is 73.7+9.1 µmol/l. In terms of security, dA indicates that cell viability is 95% higher than hydroquinone. However, dA is thermolabile and photolabile. Several studies have shown satisfactory results to improve the stability of dA, that these compounds are considerable potential for further development as a depigmentation agent. The aim of this review is to describe how the potency of dA as a tyrosinase inhibitor interferes melanogenesis process through the latest depigmentation agent, its safety, efficacy and stability.

Performance of Hydrophobisation Techniques in Case of Reinforced Concrete Structures

Concrete is, unchangeably, one of the most frequently applied building materials, also in the case of bridges, overpasses or viaducts. Along with the aging of such structures, the degradation of concrete, which may accelerate the corrosion of reinforcing steel and drastically decrease the load-bearing capacity of the structure, becomes an important issue. The paper analyzes the possibilities of using deep hydrophobisation in repairing reinforced concrete engineering structures. The benefits of properly securing reinforced concrete structures from the damaging effects of UV radiation, the influence of harmful gases, or progression of chlorine induced corrosion have been presented, especially in regards to bridge structures. The need to calculate the costs of carrying out investments along with the expected costs of maintaining such structures, as well as the high share of costs connected with logistics, has also been indicated in the total costs of repair works.

Advanced UV Absorbers for the Protection of Human Skin.

The increasing awareness of the damaging effects of UV radiation to human skin triggered the market introduction of new cosmetic UV absorbers. This article summarizes the outcome of a multi-year research program, in which the author contributed to the development of different new UV filters. First of all, the molecular design and the basic properties of bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) will be presented. This oil-soluble filter, which today is widely used in both beach products and skin care products, exhibits inherent photostability and strong broad-spectrum UV-A+B absorbance. Based on the concept of micronized organic UV absorbers, the UV-B filter tris biphenyl triazine (TBPT) will be introduced. At present TBPT exhibits the highest efficacy of all cosmetic UV absorbers in the market (measured by area under the UV spectrum). Finally, the concept of liposomogenic UV absorbers will be featured. This approach was developed to create water-resistant UV filters, as liposomogenic structures are thought to integrate into the lipids of the horny layer. Due to prohibitively high costs, this technology did not result in a commercial product so far.

Determination Of Sun Protection Factor By Uv-Vis Spectrophotometry

Background: Sunscreen products contain active ingredients that can absorb, reflect or scatter the sunlight, depending on their nature. We can evaluate the effectiveness of a sunscreen by determining the sun protection factor (SPF). This SPF should be specific for each phototype, so as to the protection against the damaging effects of UV rays may be the best. Besides the choice of the adequate sunscreen, care must be taken with the application method and the amount of product that is applied. In most cases, the real SPF did not correspond to the labeled SPF. Aim: The aim of this study was to determine the real SPF values of ten chemical or physical sunscreens through UV-Visible Spectroscopy, as well as the degradation by direct solar radiation and temperature at 37°C. Methods: UV-Vis spectrophotometry was used to measure the UV absorption of each sample and the Mansur equation was applied to obtain the final SPF. Results: The majority of the studied sunscreens have much lower SPF when compared to the labeled value. Conclusion: To avoid the damaging effects of UV radiation, we have to encourage the correct use of sunscreen, reapplication and double-application to reach a desirable effect of the sunscreen, promote the use of other physical protection (clothes, hats) and avoid the hours of peak radiation. We also concluded that it is important to have constant monitoring of SPF on sunscreens marketed in World, in order to allow their use with complete quality assurance.

Baseline monitoring of organic sunscreen compounds along South Carolina's coastal marine environment

Organic ultraviolet filters (UV-F) are increasingly being used in personal care products to protect skin and other products from the damaging effects of UV radiation. In this study, marine water was collected monthly for approximately one year from six coastal South Carolina, USA sites and analyzed for the occurrence of seven organic chemicals used as UV filters (avobenzone, dioxybenzone, octocrylene, octinoxate, oxybenzone, padimate-o and sulisobenzone). The results were used to examine the relationship between beach use and the distribution of UV-F compounds along coastal South Carolina, USA. Five of the seven target analytes were detected in seawater along coastal South Carolina during this study. Dioxybenzone and sulisobenzone were not detected. The highest concentrations measured were >3700ng octocrylene/L and ~2200ng oxybenzone/L and beach use was greatest at this site; a local beach front park. Patterns in concentrations were assessed based on season and a measure of beach use.

UV filters bioaccumulation in fish from Iberian river basins

The occurrence of eight organic UV filters (UV-Fs) was assessed in fish from four Iberian river basins. This group of compounds is extensively used in cosmetic products and other industrial goods to avoid the damaging effects of UV radiation, and has been found to be ubiquitous contaminants in the aquatic ecosystem. In particular, fish are considered by the scientific community to be the most feasible organism for contamination monitoring in aquatic ecosystems. Despite that, studies on the bioaccumulation of UV-F are scarce.In this study fish samples from four Iberian river basins under high anthropogenic pressure were analysed by liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Benzophenone-3 (BP3), ethylhexyl methoxycinnamate (EHMC), 4-methylbenzylidene camphor (4MBC) and octocrylene (OC) were the predominant pollutants in the fish samples, with concentrations in the range of ng/gdryweight (d.w.). The results indicated that most polluted area corresponded to Guadalquivir River basin, where maximum concentrations were found for EHMC (241.7ng/gd.w.). Sediments from this river basin were also analysed. Lower values were observed in relation to fish for OC and EHMC, ranging from below the limits of detection to 23ng/gd.w. Accumulation levels of UV-F in the fish were used to calculate biota-sediment accumulation factors (BSAFs). These values were always below 1, in the range of 0.04–0.3, indicating that the target UV-Fs are excreted by fish only to some extent. The fact that the highest concentrations were determined in predators suggests that biomagnification of UV-F may take place along the freshwater food web.

The photoprotective effects of a food supplement tomato powder rich in phytoene and phytofluene, the colorless carotenoids, a preliminary study

Background: Currently, protection against the damaging effects of UV radiation is most commonly accomplished by use of a topical sunscreen. This protection is effective but localized. Objective: The aim of the present study was to determine if a food supplement comprised of a tomato powder rich in Phytoene and Phytofluene, the colorless carotenoids, could improve the natural protection of the skin against the sun, and bring other beauty and health benefits to the skin. Phytoene and Phytofluene absorb in the UV range; they also have antioxidant and anti-inflammatory properties. Method: A group of 22 healthy female volunteers were given an oral supplement corresponding to an equivalent of 5 mg of Phytoene and Phytofluene a day for 12 weeks. Minimum Erythemal Dose (MED) was measured on the back of the volunteers after 6 and 12 weeks. Results: Results show an average increase of 10% of the MED in all panelists; in 2/3 of the panelists, an increase of 20% was observed after 12 weeks. Erythema after exposure to 1.25 MED was also measured, showing no increase in skin color. Skin quality was reportedly improved in 55-95% of the volunteers (clinical and subjective assessment). Conclusions: Our study, while limited in the number of panelists, shows that daily intake of these carotenoids protects the skin from UV radiation by increasing the MED and the skin’s natural resistance to UV induced erythema.

A new method for the determination of benzophenone-UV filters in human serum samples by dispersive liquid–liquid microextraction with liquid chromatography–tandem mass spectrometry

Benzophenone-UV filters (BP-UV filters) are extensively used in cosmetics products to avoid damaging effects of UV radiation. Despite their low toxicity, many research papers indicate that BP-UV filters are weak endocrine disruptors (EDCs). There are clear relationships between BP-UV filters exposure and several health disorders such as carcinogenesis and malformations observed in animals. In the present work, a new sample treatment procedure by dispersive liquid-liquid microextraction (DLLME) is proposed for the extraction of six BPs, namely benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone-3 (BP-3), benzophenone-6 (BP-6), benzophenone-8 (BP-8) and 4-hydroxybenzophenone (4-OH-BP), in human serum samples, followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. The method involves an enzymatic treatment to quantify the total content (free plus conjugated species) of BP-UV filters in serum. The extraction parameters were accurately optimized using multivariate optimization approach. Benzophenone-d₁₀ (BP-d₁₀) was used as surrogate. Limits of quantification (LOQs) ranged from 0.4 to 0.9 ng mL(-1) and inter-day precision (evaluated as relative standard deviation) ranged from 1.9% to 13.1%. The method was validated using matrix-matched calibration and a recovery assay. Recovery rates for spiked samples ranged from 97% to 106%, and acceptable linearity was obtained up to concentrations of 40 ng mL(-1). The method was applied to the determination of the target compounds in human serum samples from 20 randomly selected anonymous individuals.

Aged Human Skin is More Susceptible than Young Skin to Accumulate Advanced Glycoxidation Products Induced by Sun Exposure

Background: Skin aging is the result of intrinsic and extrinsic phenomena. Among the factors involved in skin aging, the glycation reaction and the formation of advanced glycation end-products (AGEs) is an important element. AGEs such as carboxy-methyl-lysine (CML) and pentosidine, are formed by an oxidative process, and often referred to as glycoxidation products. AGEs have been reported to accumulate during chronological aging but sun exposure has also been shown to contribute to this accumulation likely through induction of an oxidative environment. The purpose of this study was to investigate the accumulation of AGEs in human skin and, more specifically, CML and pentosidine, both of which are generated by oxidative pathways. Methods: CML and pentosidine immunolabelling were investigated in skin samples from both non photoexposed (sun protected) and photo-exposed (sun exposed) sites from donors of two different age groups (18-25 years and 70-75 years). Results: Results demonstrate CML and pentosidine accumulation in sun-exposed skin especially in the aged group. A vicious circle is envisioned in which the presence of AGEs in a tissue accelerates the formation of additional glycoxidation products following UV-exposure. Conclusion: The damaging effects of UV radiation might be more detrimental in aged skin than in young skin due, in part, to an increased accumulation of AGEs and, in turn, the exacerbation of alterations caused by chronological aging.

Small Acid-Soluble Proteins with Intrinsic Disorder Are Required for UV Resistance in Myxococcus xanthus Spores

Bacterial sporulation in Gram-positive bacteria results in small acid-soluble proteins called SASPs that bind to DNA and prevent the damaging effects of UV radiation. Orthologs of Bacillus subtilis genes encoding SASPs can be found in many sporulating and nonsporulating bacteria, but they are noticeably absent from spore-forming, Gram-negative Myxococcus xanthus. This is despite the fact that M. xanthus can form UV-resistant spores. Here we report evidence that M. xanthus produces its own unique group of low-molecular-weight, acid-soluble proteins that facilitate UV resistance in spores. These M. xanthus-specific SASPs vary depending upon whether spore formation is induced by starvation inside cell aggregations of fruiting bodies or is induced artificially by glycerol induction. Molecular predictions indicate that M. xanthus SASPs may have some association with the cell walls of M. xanthus spores, which may signify a different mechanism of UV protection than that seen in Gram-positive spores.

New UV Absorber for PET Packaging: Better Protection With Less Discoloration

``UVA S-Pack'' is a new UV absorber additive designed to protect PET packaging content from the damaging effects of UV radiation. Compared to conventional UV absorbers that have been used for this purpose, this new product offers broader UV protection with less discoloration. The performance of this new UV absorber in content protection was demonstrated in exposure tests with vitamins and colorants. The product is also FDA-cleared for use in PET for food-contact applications. Due to this product's unique absorption and emission profile, it is expected to also offer suitable performance in polyester-based films and sheets.

Effects of Enhanced Ultraviolet-B Radiation on Algae and Cyanobacteria

This article provides an overview of existing literature on the ultraviolet-B (UV-B) radiation effects on algae and cyanobacteria. We report on the effects of UV-B radiation to the growth and development, biomass, sensitivity, photosynthetic pigments, UV-B absorbing compounds, photosynthesis, protein and DNA damage, enzyme activity, nitrogen fixation and assimilation of nitrogen, protective mechanisms of algae and cyanobacteria, the accommodation of algae and cyanobacteria to environmental stress, and the effects to ecology system. Many of the studies show the dramatic effects of UV-B radiation; but typically these studies were conducted under conditions with supplemental UV-B irradiance that was higher than would ever occur outside experimental conditions or natural condition. A few of the studies reviewed used experimental conditions and supplemental UV-B irradiance that approached realism. Enhanced UV-B generally decreased chlorophyll content, whereas it increased UV-B absorbing compounds in many algae. Decrease in photosynthesis, particularly at higher UV-B doses, was due to both direct (effect on photosystem) and indirect (decrease in pigments) effects. The decreases in chlorophyll pigments and photosynthesis resulted in lower biomass. However, algae and cyanobacteria have evolved various avoidance and repair mechanisms to protect themselves against the damaging effects of UV radiation to acclimate to enhanced UV-B radiation. The review points to areas where further studies on the relationships among nitrogenase, Rubisco, antioxidase activity, signal, antioxidants, and free radicals under enhanced UV-B are needed to quantify the effects of UV-B radiation on algae and cyanobacteria. These studies are needed in order to develop dose response functions that can facilitate development of dynamic simulation models for use in UV-B and other environmental impact assessments.