A Review of Sunscreen Safety and Efficacy

Growth and characterization of organic material 2-methylamino-5-chlorobenzophenone single crystal by modified vertical Bridgman technique

The organic material 2-methylamino-5-chlorobenzophenone single crystal has been grown by modified vertical Bridgman technique using the single wall ampoule with nano translation. The grown crystal was confirmed by single crystal and powder X-ray diffraction analyses. Fourier transform infrared analysis was used to identify the functional groups present in the grown crystal. High resolution X-ray diffraction studies show the crystalline perfection of the grown crystal. The optical property of the grown crystal was analyzed by UV-vis-NIR and photoluminescence spectral studies. The thermal behavior of the grown crystal was analyzed by thermogravimetric and differential thermal analyses. The dielectric measurements of the grown crystal were carried out with different frequencies and temperatures and the results indicate an increase in dielectric and conductivity parameters with the increase of temperature at all frequencies. The microhardness measurements were performed to analyze the mechanical property of the grown crystal.

Color stability of maxillofacial silicone with nanoparticle pigment and opacifier submitted to disinfection and artificial aging

The purpose of this study was to evaluate the color stability of a maxillofacial elastomer with the addition of a nanoparticle pigment and∕or an opacifier submitted to chemical disinfection and artificial aging. Specimens were divided into four groups (n = 30): group I: silicone without pigment or opacifier, group II: ceramic powder pigment, group III: Barium sulfate (BaSO(4)) opacifier, and group IV: ceramic powder and BaSO(4) opacifier. Specimens of each group (n = 10) were disinfected with effervescent tablets, neutral soap, or 4% chlorhexidine gluconate. Disinfection was done three times a week during two months. Afterward, specimens were submitted to different periods of artificial aging. Color evaluation was initially done, after 60 days (disinfection period) and after 252, 504, and 1008 h of artificial aging with aid of a reflection spectrophotometer. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05). The isolated factor disinfection did not statistically influence the values of color stability among groups. The association between pigment and BaSO(4) opacifier (GIV) was more stable in relationship to color change (△E). All values of △E obtained, independent of the disinfectant and the period of artificial aging, were considered acceptable in agreement with the norms presented in literature.

Identification and semi-quantitative analysis of parabens and UV filters in cosmetic products by direct-analysis-in-real-time mass spectrometry and gas chromatography with mass spectrometric detection

A method based on direct-analysis-in-real-time mass spectrometry (DART-MS) for the qualitative and semi-quantitative analysis of eight organic UV filters and four parabens in twelve cosmetic products with substantially different formulations (as cream, milk, lotion, oil, lipstick) was developed. All tested substances could be identified unambiguously in the investigated samples without any sample pre-treatment. Direct analysis of cosmetic products allows semi-quantitative determination of parabens. For UV filters no satisfactory results were obtained by direct analysis but all analytes could be quantified by simply dissolving the samples in methanol, addition of an internal standard and subsequent measurement of the solution by DART-MS without further pre-treatment. The results obtained using DART-MS were confirmed by a more established method namely gas chromatography with mass spectrometric detection (GC-MS).

Human safety review of "nano" titanium dioxide and zinc oxide

Based on the current weight of evidence of all available data, the risk for humans from the use of nano-structured titanium dioxide (TiO(2)) or zinc oxide (ZnO) currently used in cosmetic preparations or sunscreens is considered negligible. There is a large body of information that when viewed in its entirety is considered as sufficient to demonstrate that these nano-structured ultraviolet (UV) filters, irrespective of various treatments (coatings) or crystalline structure, can be regarded as safe for use at concentrations up to 25% in cosmetic products to protect the skin from harmful effects of solar UV radiation. "Nano" TiO(2) and ZnO formulated in topically applied sunscreen products exist as aggregates of primary particles ranging from 30-150 nm in size. These aggregates are bonded such that the force of sunscreen product application onto the skin would have no impact on their structure or result in the release of primary particles. Multiple studies have shown that under exaggerated test conditions neither nano-structured TiO(2) nor ZnO penetrates beyond the stratum corneum of skin. Further, the distribution and persistence of these nano-structured metal oxides is the same compared to larger pigment-grade (i.e., >100 nm) particles, demonstrating equivalence in the recognition and elimination of such material from the body. Finally, the in vitro genotoxic and photogenotoxic profiles of these nano-structured metal oxides are of no consequence to human health. Whereas the most logical, straightforward conclusion based on data from internationally-recognized guideline studies and current 20+ year history of human use is that nano-structured TiO(2) and ZnO are safe, there will continue to be questions as "nano" conjures images of technology gone awry. Despite this rather sober view, the public health benefits of sunscreens containing nano TiO(2) and/or ZnO outweigh human safety concerns for these UV filters.

The use of radioactive zinc oxide nanoparticles in determination of their tissue concentrations following intravenous administration in mice

The increasing uses of zinc oxide nanoparticles (ZnONPs) in coatings, paints, personal care products and many other products increase the possibility of the body's exposure to ZnONPs. Accurate and quantitative profiling on the tissue distribution and body clearance of ZnONPs, which is an important factor to clarify the acute and chronic safety concerns of ZnONPs, is interfered by the abundance of the body's endogenous zinc moiety. In this report, radioactive zinc oxide nanoparticles (R-ZnONPs) generated from neutron activation were employed for the in vivo bio-distribution studies using mice as the animal model. Gamma-ray emitting radioactive R-ZnONPs were produced from neutron activation. Zeta potentials of the ZnONPs before and after the neutron irradiation remained about the same, and R-ZnONPs largely remained its original nano-particulate form after neutron irradiation. After intravenous administration into ICR mice, R-ZnONPs exhibited a primary retention in lung (43.6% injected dose (ID)/g tissue wet weight) for the first hour and began to be translocated to intestinal tract for feces excretion at a later stage. This type of labeling free and radioactive nanoparticles retains the surface property and can be a convenient protocol for studying bio-distribution of nanoparticles in pristine chemical form.

Influence of solid lipid microparticle carriers on skin penetration of the sunscreen agent, 4-methylbenzylidene camphor

The objective of this study was to prepare lipid microparticles (LMs) loaded with the sunscreen agent, 4-methylbenzylidene camphor (4-MBC), to achieve decreased skin penetration of this UV filter. The microparticles were produced by the melt dispersion technique using tristearin as lipidic material and hydrogenated phosphatidylcholine as the surfactant. The obtained microparticles were characterized by scanning electron microscopy and differential scanning calorimetry. Release of 4-MBC from the LMs was found to be slower than its dissolution rate. The influence of the LMs' carrier system on percutaneous penetration was evaluated after their introduction in a model topical formulation (emulsion). In-vitro measurements were performed with cellulose acetate membranes in Franz diffusion cells. The 4-MBC release and diffusion was decreased by 66.7-77.3% with the LM formulation, indicating that the retention capacity of the microparticles was maintained after incorporation into the emulsion. In-vivo human skin penetration of 4-MBC was investigated by tape stripping, a technique for selectively removing the upper cutaneous layers. The amount of sunscreen penetrating into the stratum corneum was greater for the emulsion containing non-encapsulated 4-MBC (36.55% of the applied dose) compared with the formulation with the sunscreen-loaded microparticles (24.57% of the applied dose). The differences between the two formulations were statistically significant in the first (2-4) horny layer strips. Moreover, the LMs' effect measured in-vivo was less pronounced than in-vitro. The increased 4-MBC retention on the skin surface achieved by its incorporation in the LMs should enhance its efficacy and reduce the potential toxicological risk associated with skin penetration.

Interventions for preventing non-melanoma skin cancers in high-risk groups

BACKGROUND

Some groups of people have a greater risk of developing common non-melanoma skin cancers (NMSC).

OBJECTIVES

To evaluate interventions for preventing NMSC in people at high risk of developing NMSC.

SEARCH STRATEGY

We searched the Cochrane Skin Group Specialised Register (March 2007), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2007, MEDLINE (from 2003 to March 2007), EMBASE (from 2005 to March 2007), the metaRegister of Controlled Trials (February 2007). References from trials and reviews were also searched. Pharmaceutical companies were contacted for unpublished trials.

SELECTION CRITERIA

Randomised controlled trials of adults and children at high risk of developing NMSC.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and assessed their methodological quality.

MAIN RESULTS

We identified 10 trials (7,229 participants) that assessed a variety of interventions. One trial found T4N5 liposome lotion significantly reduced the rate of appearance of new BCCs in people with xeroderma pigmentosum. One of three trials of renal transplant recipients showed a significantly reduced risk of new NMSCs when acitretin was compared to placebo (relative risk (RR) 0.22 95% confidence interval (CI) 0.06 to 0.90) and no significant difference in risk of adverse events in two trials (RR 1.80, 95% CI 0.70 to 4.61). In three trials conducted in people with a history of NMSC, the evidence was inconclusive for the development of BCCs for retinol or isoretinoin. However the risk of a new SCC in one trial (HR 1.79, 95% CI 1.16 to 2.76) and adverse events in another trial (RR 1.76 95% CI 1.57 to 1.97) were significantly increased in the isotretinoin group compared with placebo. In one trial selenium showed a reduced risk of other types of cancer compared with placebo (RR 0.65, 95% CI 0.50 to 0.85) but also a significantly elevated risk of a new NMSC (HR 1.17 95% CI 1.02 to 1.34). The evidence for one trial of beta-carotene was inconclusive; and there was a trend towards fewer new NMSC in a trial of a reduced fat diet (RR 0.16, 95% CI 0.02 to 1.31), p=0.09.

AUTHORS' CONCLUSIONS

Some preventative treatments may benefit people at high risk of developing NMSC, but the ability to draw firm conclusions is limited by small numbers of trials, often with one trial per intervention or with inconsistent results between studies.

Photoprotection

Sun exposure is the main cause of photocarcinogenesis, photoageing, and photosensitivity; thus, photoprotection is an important issue. In a skin cancer prevention strategy, behavioural measures--eg, wearing sun protective clothes and a hat and reducing sun exposure to a minimum--should be preferred to sunscreens. Often this solution is deemed to be unacceptable in our global, outdoor society, and sunscreens could become the predominant mode of sun protection for various societal reasons (eg, healthiness of a tan, relaxation in the sun). The application of a liberal quantity of sunscreen has been shown to be by far the most important factor for effectiveness of the sunscreen, followed by the uniformity of application and the specific absorption spectrum of the agent used. The sunscreen market--crowded by numerous products--shows various differences worldwide. Nevertheless, sunscreens should not be abused in an attempt to increase time in the sun to a maximum. Controversies about safety of sunscreens and clinical recommendations are discussed.

Solid lipid microparticles containing the sunscreen agent, octyl-dimethylaminobenzoate: effect of the vehicle

Solid lipid microparticles (SLMs) loaded with the sunscreen agent, octyl-dimethylaminobenzoate (ODAB), were prepared in order to achieve enhanced sunscreen photostability. The microparticles were produced by the melt dispersion technique using glyceryl behenate as lipidic material and poloxamer 188 as the emulsifier. The obtained SLMs showed proper features in terms of morphology, size distribution (1.67-15.81 microm) and ODAB loading (16.15+/-0.11%, w/w). The sunscreen release from the SLMs was slower than its dissolution rate and the photodecomposition of ODAB was markedly decreased (>51.3%) by encapsulation into the lipid microparticles. The efficacy of the SLM carrier system was also evaluated after their introduction in model topical formulations (i.e., hydrogel and oil-in-water emulsion). Further in vitro release measurements, performed using Franz diffusion cells with polycarbonate membranes, indicated that the retention capacity of the microparticles was lost after their incorporation into the emulsion, whereas it was retained in the hydrogel. Moreover, the SLMs achieved a reduction of the sunscreen photodegradation in the hydrogel vehicle (the ODAB loss decreased from 87.4% to 59.1%), whereas no significant photoprotective effect was observed in the emulsion. Therefore, the efficacy of the ODAB-loaded SLMs was markedly affected by the vehicle.

Promoting sun safety among US Postal Service letter carriers: impact of a 2-year intervention

OBJECTIVES

We examined whether US Postal Service letter carriers who received a sun safety intervention would wear wide-brim hats and sunscreen significantly more often than those who did not receive the intervention.

METHODS

We used a 2-group randomized design with 2662 evaluation cohort participants from 70 US postal stations. Evaluations were conducted at baseline, 3 months, 1 year, and 2 years. Questionnaire items assessed occupational use of sun-screen and wide-brim hats. The 2-year sun safety intervention included the provision of wide-brim hats, accessible sunscreen, reminders, and 6 educational sessions.

RESULTS

At the 3-month follow-up evaluations, the odds ratio (OR) for regular sun-screen use was 2.8 times higher among the intervention group than among the control group (95% confidence interval [CI]=2.2, 3.5); at the 2-year follow-up evaluations, the rate was still significantly higher (OR=2.0; 95% CI=1.6, 2.6). Intervention group participants also had significantly higher rates of hat use, with the differences remaining consistent across all follow-ups (OR=2.9; 95% CI=2.3, 3.6).

CONCLUSIONS

The intervention should be disseminated to postal stations nationwide and possibly to other occupational groups that work outdoors.

Complexation of the sunscreen agent, 4-methylbenzylidene camphor with cyclodextrins: effect on photostability and human stratum corneum penetration

The interaction between the sunscreen agent, 4-methylbenzylidene camphor (4-MBC) and hydrophilic alpha-, beta- and gamma-cyclodextrin derivatives was investigated in water by phase-solubility analysis. Among the studied cyclodextrins, random methyl-beta-cyclodextrin (RM-beta-CD) had the greatest solubilizing activity. The complexation of the sunscreen agent with RM-beta-CD was confirmed by nuclear magnetic resonance spectroscopy and powder X-ray diffractometry. The light-induced decomposition of 4-MBC in emulsion vehicles was markedly decreased by complexation with RM-beta-CD (the extent of degradation, determined by HPLC, was 7.1% for the complex compared to 21.1% for free 4-MBC). The influence of RM-beta-CD on the human skin penetration of the sunscreen was investigated in vivo using the tape stripping method, a useful procedure for selectively removing the outermost cutaneous layers. Considerable quantities (21.2-25.1% of the applied dose) of 4-MBC permeated in the stratum corneum. However, no significant differences in the amounts of UV filter in the 10 first strips of the horny layer were observed between the formulations containing 4-MBC free or complexed with RM-beta-CD. Therefore, RM-beta-CD complexation did not alter the retention of 4-MBC in the superficial layers of the stratum corneum, where its action is more desirable.

Occupational exposure to ultraviolet radiation: the duality dilemma

Human exposure to ultraviolet (UV) radiation is a component of everyday life and a significant hazard for outdoor workers. In addition, a large range of artificial sources also has the potential to provide extreme occupational UV exposure. Even though the human health risks of overexposure to UV are well documented, to date relatively little is known quantitatively about UV exposure. For example, the evidence indicates that workers who are exposed to particular sources (for example, welding arcs) are exposed to extreme UV exposures, despite the use of current control measures. In contrast, increasing evidence points to significant health impacts resulting from underexposure to UV, particularly with the production (or more correctly lack of production) of vitamin D in the skin. The latter poses a serious issue for the work-force, with specific risks for workers lacking adequate sun exposure-underground miners, long-haul flight crews, shift workers, and perhaps indoor workers. Using a risk-management approach, this paper provides a comprehensive review of occupational UV sources, health impact of occupational UV exposure, occupational exposure standards, and levels of exposure in various settings, and discusses the appropriate control measures. In addition, the duality aspect of health impacts from overexposure and underexposure to UV and the associated occupational health implications are specifically explored.

Coenzyme Q_{10} effects on manganese superoxide dismutase and glutathione peroxidase in the hairless mouse skin induced by ultraviolet B irradiation

Coenzyme Q_{10} (CoQ_{10}) is a naturally occurring antioxidant and a prominent component of mitochondrial electron transport chain. In the present study, we investigated the effect of CoQ_{10} nanoparticle against photoaging using immunohistochemistry and Western blot analysis in the hairless mouse skin induced by ultraviolet B (UVB) irradiation (300 mJ/cm;{2}, 3 min/day for 21 days). In the UVB-irradiated distilled water (DW)-treated group, manganese superoxide dismutase (SOD2) and glutathione peroxidase (GPx) immunoreactivity and their protein levels in the skin were significantly lower than those in the control group. However, SOD2 and GPx immunoreactivity and their protein levels in the skin of the UVB-irradiated CoQ_{10}-treated group were higher than those in the UVB-irradiated DW-treated group. GPx activity in the skin in the UVB-irradiated DW-treated group significantly decreased compared to that in the control group; whereas GPx activity in the UVB-irradiated CoQ_{10}-treated group was similar to that in the control group. These results suggest that CoQ_{10} strongly inhibits oxidative stress in the skin induced by UVB via increasing SOD2 and GPx.

Nucleotide excision repair and cancer

Nucleotide excision repair (NER) is the most versatile and best studied DNA repair system in humans. NER can repair a variety of bulky DNA damages including UV-light induced DNA photoproducts. NER consists of a multistep process in which the DNA lesion is recognized and demarcated by DNA unwinding. Then, an approximately 28 bp DNA damage containing oligonucleotide is excised followed by gap filling using the undamaged DNA strand as a template. The consequences of defective NER are demonstrated by three rare autosomal-recessive NER-defective syndromes: xeroderma pigmentosum (XP), Cockayne syndrome (CS), and trichothiodystrophy (TTD). XP patients show severe sun sensitivity, freckling in sun exposed skin, and develop skin cancers already during childhood. CS patients exhibit sun sensitivity, severe neurologic abnormalities, and cachectic dwarfism. Clinical symptoms of TTD patients include sun sensitivity, freckling in sun exposed skin areas, and brittle sulfur-deficient hair. In contrast to XP patients, CS and TTD patients are not skin cancer prone. Studying these syndromes can increase the knowledge of skin cancer development including cutaneous melanoma as well as basal and squamous cell carcinoma in general that may lead to new preventional and therapeutic anticancer strategies in the normal population.

Incorporation of the sunscreen agent, octyl methoxycinnamate in a cellulosic fabric grafted with β-cyclodextrin

The aim of the study was to investigate the incorporation of the sunscreen agent, octyl methoxycinnamate into cyclodextrin cavities covalently bound to cloth fibres. Tencel, a cellulosic fabric, was grafted with beta-cyclodextrin molecules through reaction with monochlorotriazinyl-beta-cyclodextrin (beta-CDMCT). The finished and untreated textiles were soaked in water-methanol mixtures containing 2% (v/v) of sunscreen agent and subsequently subjected to several washing cycles. The unmodified and modified fabrics were characterized by UV spectrophotometry and thermogravimetric analysis. The level of octyl methoxycinnamate entrapped in the Tencel tissue was determined by high-performance liquid chromatography and was found to be much higher (0.0203%, w/w) for the textile functionalised with beta-CDMCT compared to the unmodified fabric (0.0025%, w/w). In addition, spectrophotometric assessment of UV transmission through the fabric samples using the Transpore test showed that the in vitro sun protection factor of the textile support was markedly enhanced (3.2-fold increase) by impregnation with octyl methoxycinnamate of the beta-CDMCT grafted textile. Hence, even after repeated washings, the beta-CD finished fabric exhibits higher sunscreen agent retention and photoprotective properties than the unmodified textile material.

Human Safety and Efficacy of Ultraviolet Filters and Sunscreen Products

Ultraviolet (UV) filters are the active ingredients in sunscreens. The concentration and combination of UV filters determine the efficacy of sunscreens as measured by sun protection factor. The safety of individual UV filters, and, more generally, sunscreen products, is a matter of a few related components: objective toxicologic evaluation, phototoxicologic potential, and human health consequences of using products that may reduce some but not all of the solar UV. Of 16 UV filters approved by the US Food and Drug Administration, 9 are used in different combinations in the most currently marketed sunscreens. Most of these compounds are considered safe and effective alone or in combination with other UV filters based on extensive toxicologic/phototoxicologic evaluations and market history. The benefits from proper use of sunscreens outweigh real or perceived human health concerns, establishing a favorable benefit-to-risk ratio. Future UV filters will require complete human safety evaluations alone and in combination with select benchmark ingredients.

Near-critical carbon dioxide extraction and liquid chromatography determination of UV filters in solid cosmetic samples: A green analytical procedure

Near-critical carbon dioxide extraction of four UV filters used as sunscreens in lipsticks and makeup formulations is reported. Extraction parameters were optimized. Efficient recoveries were obtained after 15 min of dynamic extraction with a 80:20 CO2/ethanol mixture at 300 atm and 54 degrees C, using a 1.8 mL/min flow rate. Extracts were collected in ethanol, and appropriately diluted with ethanol and 1% acetic acid to obtain a 70:30 v/v ethanol/1% acetic acid solution. The four UV filters were determined by LC with gradient elution using ethanol/1% acetic acid as mobile phase. The accuracy of the analytical procedure was estimated by comparing the results with those obtained by methods based on classical extraction. The proposed method only requires the use of CO2, ethanol and acetic acid avoiding the use of more toxic organic solvents, thus it could be considered as both operator and environment friendly.

UV-specific DNA repair recombinant fusion enzyme: a new stable pharmacologically active principle suitable for photoprotection

BACKGROUND

UV radiation can produce mutations in skin cells and correlates strongly with the onset of actinic keratoses and basal and squamous cell carcinomas. Xeroderma pigmentosum (XP) is a heritable disease characterized by an extreme sensitivity of skin to UV radiation. Recently, studies in cultured cells as well as in XP patients have demonstrated that the recombinant T4 endonuclease V UV-specific endonuclease could enhance repair of UV-induced photoproducts.

OBJECTIVE

We aimed to obtain a stable UV-specific DNA recombinant endonuclease, pharmacologically active in mammalian cells so as to be used in treatment and prophylaxis of sun damage.

METHODS

The UV-specific DNA endonuclease gene obtained from Micrococcus luteus, was fused to a leader peptide and expressed (alphaUveA), refolded and purified. A construction under the control of an eukaryotic promoter was used to transfect XP fibroblasts deficient in DNA damage repair. Transformed cells were UV irradiated and cell survival was assessed.

RESULTS

alphaUveA was obtained as a highly active UV-specific repair enzyme stable for at least 2 years. XP fibroblasts transfected with alphaUveA gene increased the resistance to UV radiation and, in consequence, cell survival.

CONCLUSION

alphaUveA is stable and pharmacologically active in human cells. The topical administration of this long-term stable new active principle could help diminish the risks of skin cancer after sun exposure.

Assay of common sunscreen agents in suncare products by high-performance liquid chromatography on a cyanopropyl-bonded silica column

A rapid high-performance liquid chromatographic method was developed for the simultaneous assay of eight of the most common sunscreen agents (octyl-methoxycinnamate, oxybenzone, butyl-methoxydibenzoylmethane, octyl-salicilate, methylbenzylidene camphor, octyl-dimethylamminobenzoate, phenylbenzimidazole sulphonic acid and octocrylene) in sun protection products. Evaluation of the influence of different stationary phases and eluents on the separation selectivity showed that optimal resolution was obtained on a cyanopropyl-silica column eluted with methanol-acetonitrile-tetrahydrofuran-aqueous acetic acid. A small adjustment of the proposed chromatographic system (reduction in the aqueous content of the mobile phase) permitted also the determination of the extremely hydrophobic UV filter, methylene bis-benzotriazolyl tetramethylbutylphenol along with three other sunscreen agents, octyl-methoxycinnamate, oxybenzone, butyl-methoxydibenzoylmethane. Recoveries of the UV filters from the spiked formulation were between 95.7 and 103.7% and the precision of the method was better than 6.1% relative standard deviation. The developed HPLC procedure is suitable for quality control and photostability analyses of commercial suncare products.

Photoprotection

Many agents affect the transmission of ultraviolet light to human skin. These include naturally occurring photoprotective agents (ozone, pollutants, clouds, and fog), naturally occurring biologic agents (epidermal chromophores), physical photoprotective agents (clothing, hats, make-ups, sunglasses, and window glass), and ultraviolet light filters (sunscreen ingredients and sunless tanning agents). In addition, there are agents that can modulate the effects of ultraviolet light on the skin (antioxidants and others). All of the above are reviewed in this article.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be able to provide an overview of all aspects of photoprotection.

Ethnoracial differences among outdoor workers in key sun-safety behaviors

BACKGROUND

Few sun-safety studies have included ethnoracially diverse groups. Comparison across such groups of sun-safety behaviors was the main objective of this analysis.

METHODS

Postal workers (n =2543) self-reported frequency of sunscreen, wide-brim hat, and sunglasses use during the last 5 workdays on 5-point Likert-type scales ranging from "never" to "always." Responses were dichotomized by "always" versus all other responses. Generalized estimating equations were used to assess the association between ethnicity/race and frequency of each sun safety behavior. The baseline data reported in this paper were collected in the summer of 2001, and the randomized trial was completed in the summer of 2004.

RESULTS

Ethnicity/race was significantly related to sunscreen and sunglasses use. For both sunscreen and sunglasses, the white group had significantly higher "always" rates than the other four groups (30% vs 14% to 23% and 63% vs 44% to 52%, respectively).

CONCLUSIONS

The results of this study indicated that although non-Latino white employees tended to have higher rates of sun-safety behaviors, the rates of adequate protection of all groups were low.

Susceptibility of skin cells to UVA-induced necrotic cell death reflects the intracellular level of labile iron

The mechanism of resistance of keratinocytes to ultraviolet A (UVA) (320-400 nm)-induced oxidative damage has not yet been elucidated. Here, we examined the possible link between the intracellular level of the labile iron pool (LIP) and the susceptibility to UVA-induced cell death using a series of human skin fibroblast and keratinocyte cell lines as a model. Resistance of keratinocytes to UVA-induced cell death was confirmed by flow cytometry and in fibroblasts necrosis was found to be the primary mode of cell death induced by UVA. The percentage of necrosis in fibroblasts also correlated with the extent of intracellular ATP depletion, a hallmark of necrotic cell death. The evaluation of the intracellular level of LIP by calcein assay revealed that both "basal" and "UVA-induced" levels of LIP in keratinocytes were several fold lower than in fibroblasts. Accordingly the dose to give an equivalent level of necrosis was several fold lower in fibroblasts than in keratinocytes. Furthermore, the modulation of "basal" or "UVA-induced" level of LIP by either Desferal and/or hemin treatment significantly affected the extent of UVA-induced necrotic cell death and ATP depletion in all the cell lines. Cellular susceptibility to UVA-induced necrotic cell death appears to reflect the intracellular level of LIP.

Lack of in vitro protection by a common sunscreen ingredient on UVA-induced cytotoxicity in keratinocytes

As an extension of our previous investigations on sunscreen ingredients, the present work was aimed at assessing the possible protective effects of a common UVA-absorbing agent, Parsol 1789 (4-tert-butyl-4'-methoxydibenzoylmethane) in contact with human keratinocytes under UVA illumination. Cell viability was evaluated by determining lactate dehydrogenase (LDH) release, uptake of propidium iodide and fluorescein diacetate, total protein content and percentage of cell detachment. Apoptosis was detected by recognition of translocated phosphatidylserine using annexin V-FITC uptake. Oxidative stress was evaluated through the carboxy-H2DCFDA assay while the total oxyradical scavenging capacity (TOSC) assay was used for determining the total antioxidant capacity level in these cells. Lipid peroxidation was also assessed by checking hydroperoxide (HP) levels. The results obtained show that UVA exposure induces significant cell mortality, decrease in protein concentration, release of LDH, increase in apoptosis, oxidative stress and lipid peroxidation with a concomitant reduction in the response of the antioxidant cellular defense system. The presence of 10 microM Parsol 1789 did not minimize these UVA-induced effects, on the contrary, for some parameters measured such as lipid hydroperoxides, there was a significant enhancement. Furthermore, the presence of glutathione (GSH) alone decreased the level of ROS and lipid hydroperoxides, but in combination with Parsol 1789, this protective effect was reduced. The overall results indicate that the compound does not protect these cells from UVA exposure under our experimental conditions confirming previous findings on the lack of photoprotective efficiency of this sunscreen in contact with biologically relevant molecules. However, the biological role and significance of these results to the consequences of sunscreen use in humans are not known, hence extrapolation from laboratory experiments must be done with caution.