Surface-enhanced Raman spectroscopy enables confirmatory detection of dyes on hair submerged in hypolimnion water for up to twelve weeks.

Difficulties in the localization of bodies of homicidal or drowning victims in natural water result in their submergence for weeks if not months. Water insects and microbes drastically change the body's appearance, which significantly changes the determination of a victim's identity. DNA analysis is commonly used for identifying the decedent; however, this PCR-based approach is time-consuming and destructive of the evidence. Considering that nearly half of the people in the world dye their hair with a variety of permanent and semi-permanent dyes, one can expect that confirmatory identification of dyes on the body's hair can be used to shed light on the victim's identity. A growing body of evidence suggests that surface-enhanced Raman spectroscopy (SERS) can be used to detect and identify hair dyes. In this study, we investigated the extent to which SERS could be used to detect black and blue, permanent and semi-permanent dyes on hair submerged in hypolimnion water for up to twelve weeks. We found that SERS enabled 100% accurate identification of analyzed dyes on hair submerged in hypolimnion water for up to 8 weeks, whereas, on average, 87% accurate identification of the hair dyes could be achieved on hair exposed for 10 weeks and 50% for hair exposed 12 weeks in hypolimnion water. We also found that the aqueous environment caused progressive fading of some dyes, whereas other dyes showed substantial spectral transformations after prolonged submergence. Finally, we found that changes in the intensity of vibrational bands of dyes could be used to predict the duration of submergence of colored hair in hypolimnion water.

Bioinspired peptides designed for hair perming and dyeing with potential for repair.

Cosmetics for perming hair are commonly used but have negative impacts on hair fibers. Repairing damaged hair with conditioners, hair oil, and hair masks can provide relief but cannot prevent injuries. Recent research has shown that proteins and amino acids can remodel hair's disulfide bonds. However, the permeation ability of proteins is limited, and amino acids may disrupt the secondary structure of hair keratins. Our study demonstrates that peptides can be safely, efficiently, and promisingly used for hair perming. A bioinspired peptide, PepACS (PepA-PepC-SPB), was designed through bioinformatics. It can interact with keratin's sulfhydryl group in situ to remodel disulfide bonds without affecting hair fiber's tensile properties. The potential of PepACS to repair cuticle injuries is also observed through scanning electron microscope visualization. Besides, linking PepACS with mCherry enables hair dyeing. This research suggests that biomaterials can be applied in the hair care industry. STATEMENT OF SIGNIFICANCE: Chemical perming products can have negative impacts on people's health and hair fibers, making it essential to explore alternative methods. Peptides treatment is a promising option, but synthesizing sulfur-rich short peptides for hair perming has not been demonstrated before. In this paper, we utilized bioinformatics to design bio-inspired peptides that can interact with hair keratins and form curled shapes. Our study demonstrates that bioinformatics tools can be utilized to design bioinspired peptides with unique functions. Sulfur-rich short peptides can be heterologously expressed with fusion strategies, and PepACS can securely bind hair fibers through disulfide bonds. Importantly, perming hair with 0.01% PepACS maintains the mechanical properties of hair, and dyeing hair with the fusion protein PepACS_mCh can be facilitated by ethanol. These findings suggest that the strategy of perming and dyeing hair through peptides is non-injurious, and the peptides used for repairing hair damage show tremendous potential.

Elucidation of the effect of heat exposure on hair colored by permanent and semipermanent colorants using surface-enhanced Raman spectroscopy.

Confirmatory identification of hair colorants can be used to establish a connection between a suspect and the crime science or demonstrate the absence of such connections. A growing body of evidence shows that surface-enhanced Raman spectroscopy (SERS) could be a confirmatory, minimally destructive, and fully noninvasive analysis of hair colorants. In SERS, a signal that provide the information about the chemical structure of both permanent and semipermanent dyes present on hair is enhanced by a million-fold using noble metal nanostructures. However, it is unclear whether the information of hair colorants can be revealed if hair was contaminated or exposed to harsh environments such as sunlight and heat. In this work, we determine the effect of a short- and long-term heat exposure on SERS-based analysis of hair colored with blue and red permanent and semipermanent dyes. We found that short and especially long-term heat exposure at 220°C could alter chemical structure, and consequently SERS spectra, of permanent and semipermanent colorants. This thermal degradation of permanent dyes complicates their direct identification using SERS. We also found that partial least squares discriminant analysis can be used to overcome this issue allowing for highly accurate identification of both permanent and semipermanent dyes on colored hair that was exposed to 220°C for 6-12 min. These results show that heat exposure of colored hair should be strongly considered upon their SERS-based examination to avoid both false positive or false negative identification of chemical dyes.

Implementing a suspect screening method to assess occupational chemical exposures among US-based hairdressers serving an ethnically diverse clientele: a pilot study.

BACKGROUND: There are over 700,000 hairdressers in the United States, and it is estimated that >90% are female and 31% are Black or Hispanic/Latina. Racial and ethnic minorities in this workforce may be exposed to a unique mixture of potentially hazardous chemicals from products used and services provided. However, previous biomonitoring studies of hairdressers target a narrow list of compounds and few studies have investigated exposures among minority hairdressers. OBJECTIVE: To assess occupational chemical exposures in a sample of US-based Black and Latina hairdressers serving an ethnically diverse clientele by analyzing urine specimens with a suspect screening method. METHODS: Post-shift urine samples were collected from a sample of US female hairdressers (n = 23) and office workers (n = 17) and analyzed via reverse-phase liquid chromatography coupled to high-resolution mass spectrometry. Detected compounds were filtered based on peak area differences between groups and matching with a suspect screening list. When possible, compound identities were confirmed with reference standards. Possible exposure sources were evaluated for detected compounds. RESULTS: The developed workflow allowed for the detection of 24 compounds with median peak areas ≥2x greater among hairdressers compared to office workers. Product use categories (PUCs) and harmonized functional uses were searched for these compounds, including confirmed compounds methylparaben, ethylparaben, propylparaben, and 2-naphthol. Most product use categories were associated with "personal use" and included 11 different "hair styling and care" product types (e.g., hair conditioner, hair relaxer). Functional uses for compounds without associated PUCs included fragrance, hair and skin conditioning, hair dyeing, and UV stabilizer. SIGNIFICANCE: Our suspect screening approach detected several compounds not previously reported in biomonitoring studies of hairdressers. These results will help guide future studies to improve characterization of occupational chemical exposures in this workforce and inform exposure and risk mitigation strategies to reduce potential associated work-related health disparities.

Effects of crime scene contaminants on surface-enhanced Raman analysis of hair.

Forensic analysis of hair is important as hair is one of the most commonly examined forms of trace evidence found at crime scenes. A growing body of evidence suggests that surface-enhanced Raman spectroscopy (SERS), a label-free and non-destructive analytical technique, can be used to detect and identify artificial colorants present on hair. However, hair collected at crime scenes is often contaminated by substances of biological and non-biological origin present at such locations. In this study, we investigate the extent to which four contaminants, saliva, blood, dirt, and bleach can alter the accuracy of SERS-based detection and identification of both permanent and semi-permanent colorants present on hair. Our findings show that saliva and dirt reduce the intensity of the colorants' signals but do not obscure their detection and identification. At the same time, an exposure of the colored hair to bleach or the presence of blood eliminates SERS-based analysis of artificial dyes present on such samples. We identified the procedure that can be used to remove blood contamination, which, in turn, enables identification of the hair colorants on such pre-cleaned samples. However, bleach treatment irreversibly eliminates SERS-based detection of artificial colorants on hair. These findings expand our understandings about the potential of SERS in forensic investigation of colorants on trace hair evidence.

Surface-enhanced Raman spectroscopy enables highly accurate identification of different brands, types and colors of hair dyes.

Hair is present at nearly all crime scenes. Forensic analysis of hair can be used to establish a connection between a suspect and a crime scene or demonstrate the absence of such connection. Almost half of people around the world color their hair. However, there is no robust and reliable forensic approach that can be used for a confirmatory analysis of artificial colorants present on hair. A growing body of evidence suggests that surface-enhanced Raman spectroscopy (SERS), a modern analytical technique, can be used to detect and identify colorants present on hair. In the current work, we examined the potential of SERS in identification of more than 30 different colorants. We found that the accuracy of detection and identification of individual hair colorants is 97%, on average. We also investigated the extent to which SERS can be used to differentiate between different brands and types of colorants, as well as to identify hair color regardless of the type and brand of the colorant used to dye hair. Our results showed that individual colorants could be identified with on average 97% accuracy, whereas different brands can be predicted with nearly 100% accuracy. We also found that SERS offered nearly 100% accurate identification of the type of the colorant and on average 97.95% accurate prediction of the hair color. These results demonstrate that SERS can facilitate the forensic analysis of hair providing highly important information about the artificial colorants present on the analyzed specimens.

[Determination of 32 oxidative dyes by high performance liquid chromatography and confirmation by high performance liquid chromatography-tandem mass spectrometry].

Various types of oxidative dyes used in hair dye products possess poor stability and have varying frequency of use. Interference problems also frequently arise in actual sample measurements. Therefore, it is necessary to establish a simple, rapid, accurate, and specific method for the determination of common dyes in hair dye products for their effective regulation. In this study, dyes were grouped according to their frequency of use. Using a C18 column that minimizes the silanol effect and influence of metals, the quantitative high performance liquid chromatography (HPLC) method for 32 dyes listed in Safety and Technical Standards for Cosmetics (2015 edition) was optimized, and a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) confirmatory method for the dyes was established. The samples were extracted using a mixed solution of ethanol-water (1∶1, v/v) with 10 g/L sodium bisulfite solution as an antioxidant, vortexed and mixed, and then extracted by ultrasonication in an ice bath for 10 min. Methanol, acetonitrile, and phosphate buffer were used as the mobile phases in the HPLC analysis. Additionally, two different elution conditions (chromatographic gradient) were used for the separation of 32 oxidative dyes, which were detected at a wavelength of 280 nm. The HPLC separations were compared using columns of particle sizes 5 µm and 2.7 µm; 5 µm C18 columns with better anti-interference and antiblocking ability were selected. Satisfactory separation was achieved for all three commercial C18 columns with a particle size of 5 µm, and the method had good general usability. In condition 1, 17 commonly used dyes and three less commonly used dyes were assigned to group Ⅰ and separated by HPLC; in condition 2, eight banned dyes and four other less commonly used dyes were assigned to group Ⅱ and separated by HPLC. The HPLC-MS/MS method used 5 mmol/L ammonium acetate aqueous solution-acetonitrile and 5 mmol/L acetic acid aqueous solution-acetonitrile as mobile phases in the positive and negative ion modes, respectively. Multiple reaction monitoring (MRM) was performed for qualitative and quantitative analyses in the electrospray ionization mode. Under the examined conditions, six pairs of isomers were well resolved. For the HPLC and HPLC-MS/MS methods, the relative standard deviations (RSDs) of the intra-day precision and 48 h stability tests were less than 10%. The recoveries were between 82.6% and 114.9% (RSD<10%). In the HPLC method, 32 dyes showed good linearity in an approximate range of 10-500 mg/L (r2>0.99), and the limits of detection (LODs) were 9.7-40.1 µg/g. The linear range of hydroquinone in the HPLC-MS/MS method was 2.0-79.7 mg/L, and the LOD was 8.0 µg/g; the linear ranges of the other components were approximately 0.1-4 mg/L, and the LODs were 0.01-0.4 µg/g. The actual samples were simultaneously measured by HPLC, HPLC-MS/MS, and the standard method. Finally, 16 of the 32 dyes were detected, and the detected contents ranged from 58 to 25160 µg/g. The RSDs of the results obtained from the three detection methods were between 1.9% and 10.1%. All detected components were within the limits of group Ⅰ of this method. In comparison with methods reported in the literature and the standard method, this method covers all components for the routine regulatory inspection of oxidative dyes in cosmetics. The method can separate the commonly used dyes under the same HPLC conditions and avoid interference from 15 other commonly used dyes during the analysis of actual samples. A suitable HPLC-MS/MS confirmatory method was also established for the identification of currently unknown substances in the statutory inspection of cosmetics. The method is simple, rapid, accurate, and specific with general usability and good operability.

Controllable synthesis of boron-doped Zn-N-C single-atom nanozymes for the ultrasensitive colorimetric detection of p-phenylenediamine.

Single-atom catalysts with atomically dispersed M-Nx active sites have been widely used as nanozymes for colorimetric sensing due to their similar structure to natural enzymes, but they are still limited by their biological activity. Herein, controllable synthesis of B-doped Zn-N-C (ZnBNC) single-atom nanozymes (SAzymes) was designed and realized for the first time as a potent peroxidase mimetic. Based on the peroxidase-like activity of ZnBNC SAzymes, a novel colorimetric method was developed for the highly sensitive and selective detection of p-phenylenediamine (PPD) with a wide response range (0.3-10 µM) and a low detection limit (0.1 µM), which can be used as an alternative method for the detection of PPD in hair dyes and dyed hair samples.

Differences between hairdressers and consumers in skin exposure to hair cosmetic products: A review.

Hairdressers are at high risk of developing occupational hand eczema. Opinions on the health and safety concerns of nonfood consumer products, such as cosmetics and their ingredients, consider the exposure of a "common consumer," which may not account for occupational exposure of hairdressers. As a result, there is a parlous scenario in which serious safety concerns about occupational exposures are present. The purpose of this review is to compare the frequency of exposure to various types of hair cosmetic products among hairdressers and consumers. Database searches for this review yielded a total of 229 articles; 7 publications were ultimately included. The analysis showed that-dependent on the task-hairdressers were exposed 4 to 78 times more than consumers to a wide spectrum of hair cosmetic products used in their daily working life, ranging from shampoos, conditioners, oxidative and nonoxidative hair colors, to bleaching agents. The highest frequency was found for coloring hair with oxidative hair color. Consumer use frequency does not appear to be appropriate for representing hairdresser exposure. The current standards do not effectively address the occupational risks associated with hairdressers' use of cosmetics. The findings of this study should cause current risk-assessment procedures to be reconsidered.

In situ Chelation of Monoazo Dyes in Human Hair Keratin Fibers Using Environmentally Benign Metal Ions.

The coloration of human hair keratin fibers has long involved the oxidative coupling of primarily aromatic amines and phenols inside the fibers with the aid of harsh agents such as H2O2 and NH4OH. Further, the traditional process has exposed millions of consumers and their hairstylists to toxic substances such as skin sensitizers. While alternative hair dyeing processes have been explored, they fail to be competitive with the traditional method, for reasons including impracticality and limited colors achievable. In the present study, we developed an approach to imparting color to human hair fibers that involves entrapping colorants inside hair fibers by forming chelated monoazo dyes in situ. Dyes employed were based on monoarylide, arylazopyrazolone, and arylazonaphthol families, which display yellow, orange, and magenta colors on dyed hair. The dyes were applied at 40 °C without the use of oxidants and alkali associated with current commercial hair dyes, with the best dye uptake observed when the arylazonaphthol dye was employed. The dyed hair fibers showed good durability to washing, and treatment of these fibers with Al3+ or Fe3+ ions at 40 °C led to the rapid in situ formation of 1:2 metal/dye structures. In addition, the dyed hair was soft, indicating that chelated dye occupies the interior of the fibers rather than the surface. Such an approach can be applied to the coloration of other materials, including textiles.

Immortalized equivalent human epidermis as a platform to evaluation hair dyes toxicity: Efficiency comparison between 3D and monolayer culture.

The use of 3D models in various scientific applications is becoming more popular to replace traditional monolayers models. In this work, we used a three-dimensional in-house model of epidermis using HaCaT immortalized cells to evaluate the dermal toxicity induced by Basic Blue 99 and Basic Red 51, both present in commercial hair dye formulations. Our data show that cells cultured in the 3D model respond differently to those cultured in monolayer. Basic Red 51 dye induces apoptosis an DNA breaks in both models, however, these effects is more pronounced in cells cultured in monolayer. The toxic mode of action of Basic Blue 99 seems to be the induction of cell death, without genotoxic effects, but while the necrotic pathway is observed in HaCaT monolayer cell culture, was apoptosis seen in the Equivalent Human Epidermis (EHE) model. We could also confirm that cells in EHE model, an environment that could better mimic human effects, react differently to chemical stressors than the cells cultivated in 2D.

Hair dye and risk of skin sensitization induction: a product survey and quantitative risk assessment for para-phenylenediamine (PPD).

BACKGROUND: Para-Phenylenediamine (PPD) is a commonly used dye intermediate in permanent hair dye formulations, and exposure to PPD has been associated with allergic contact dermatitis at certain doses. PURPOSE: Determine the concentration of PPD in a survey of self-application permanent hair dye products, and perform a quantitative risk assessment to determine the risk of skin sensitization induction following application of these products. METHODS: Consumer exposure levels (CELs) to PPD following application of hair dye products were estimated using the maximum amount of hair dye that can adhere to the surface area of the scalp, the measured concentration of PPD in the hair dye product, a retention factor, the dermal absorption of PPD, and the surface area of the scalp. CELs were calculated for various exposure scenarios, and were stratified by hair dye shade. RESULTS: All estimated CELs did not exceed the acceptable exposure level. Specifically, margins of safety ranged from 2.3 to 1534 for black dyes, 2.9 to 5031 for brown dyes, and 26 to 5031 for blonde dyes. CONCLUSIONS: Findings suggest that use of the evaluated permanent hair dyes, under the evaluated exposure scenarios, would not be expected to induce skin sensitization due to PPD exposure at concentrations ≤0.67%.

Assessment of p-aminophenol oxidation by simulating the process of hair dyeing and occurrence in hair salon wastewater and drinking water from treatment plant.

This work reports the study of oxidation reaction of p-aminophenol (PAP) in ammoniacal medium in dissolved atmospheric oxygen and hydrogen peroxide, simulating the process of hair dyeing with permanent dyes. The products formed, which included semi-quinoneimine radical, quinoneimine, dimers, trimers and tetramers, were identified by mass spectrometry, infrared spectroscopy, UV-vis spectrophotometry, and nuclear magnetic resonance of hydrogen. The process was found to involve an autoxidation mechanism. The mutagenicity of the products was carried out by Salmonella Typhimurium YG1041 assay, and the results indicated no mutagenic properties. The presence of PAP and its oxidative products in samples of wastewater collected from hairdressing salon effluent (WW), raw river water (RRW), and water inlet and outlet of drinking water treatment plant (DWTP) was analyzed by HPLC-DAD. PAP was detected in the collected samples of WW, water samples from DWTP (before and after treatment), at concentrations of 2.1 ± 0.5 mg L-1, 1.9 ± 0.3 × 10-3 mg L-1 and 1.3 ± 0.2 × 10-3 mg L-1, respectively. The reaction products, including dimers, trimers and tetramers were identified only in the WW sample; this shows that both the precursor in the sample and its derivatives were released into the wastewater.

Determination of phenylenediamines in hair colors derivatizated with 5-(4, 6-dichlorotriazinyl)aminofluorescein via micellar electrokinetic chromatography.

Phenylenediamines (PDs), which are reported to cause allergic dermatitis and possess genotoxicity and carcinogenicity, are the ingredients used in permanent hair dyes. The fluorescent derivatization strategy coupled with micellar electrokinetic chromatography (MEKC) were established to analyze four PDs, including o-phenylenediamine (OPD), m-phenylenediamine (MPD), p-phenylenediamine (PPD) and toluene-2,5-diamine (PTD). Additionally, 5-(4, 6-dichlorotriazinyl) aminofluorescein (DTAF) was used as a fluorescent reagent derived at amino groups of PDs and underwent nucleophilic substitution reaction to improve the detection sensitivity. The derivatization condition reacted at 90 °C for 10 min in alkaline conditions. The optimized separation conditions were 20 mM borate (pH 8.0) containing 10 mM Brij 35 and 35% (v/v) methanol. The limits of detection (S/N = 3) for MPD, PTD, PPD and OPD were 25, 25, 50 and 100 nM, respectively. Compared to MEKC-UV, the sensitivity enhancements were 30- to 81-fold when PDs were derived with DTAF. The high-sensitivity MEKC-LIF method was successfully established and applied to determine PDs in commercial hair colors for quality control and in real hair samples for evaluating the location of PDs in dyed hair samples, as well as in percutaneous absorption samples for evaluating the ability of PDs to penetrate skin.

Surface-Enhanced Raman Analysis of Underlaying Colorants on Redyed Hair.

Forensic examination of hair evidence can help with establishing a connection between a suspect and a crime scene or demonstrate the absence of such connections. Currently, it is primarily done by a subjective microscopic examination which can only elucidate the species of origin and, if human, the part of the body the hair came from. Several years ago, surface-enhanced Raman spectroscopy (SERS) was proposed for advanced forensic analysis of hair ( Kurouski , D. ; Van Duyne , R. P. In situ detection and identification of hair dyes using surface-enhanced Raman spectroscopy (SERS) . Anal. Chem. 2015 , 87 , 2901 - 2906 . DOI: 10.1021/ac504405u ). It was shown that SERS could be used to determine whether hair was dyed or not and even reveal what commercial hair colorant was used. Expanding upon those findings, we show that SERS is capable of probing the original colorant even if hair was redyed afterward. Specifically, we were able to detect and identify the underlaying blue semipermanent colorant on hair redyed by both black semipermanent and black permanent colorants. We also demonstrate that original black permanent colorant could be detected by SERS if the hair was recolored by blue semipermanent dye. However, it could not if the hair was recolored by another (blue or black) permanent dye. We also provide experimental evidence that SERS can be used to detect the dye on hair colored more than two months prior to its spectroscopic examination. These experimental findings substantially expand capabilities of SERS in forensics.

A highly sensitive perovskite oxide sensor for detection of p-phenylenediamine in hair dyes.

Effective regulation of p-phenylenediamine (PPD), a widely used precursor of hair dye that is harmful to human health in large concentration, relies upon an accurate yet simple detection of PPD. In this context, amperometric electrode sensor based on perovskite oxide becomes attractive given its portability, low cost, high sensitivity, and rapid processing time. This work reports the systematic characterization of a series of Sr-doped PrCoO3-δ perovskite oxides with composition of Pr1-xSrxCoO3-δ(x = 0, 0.2, 0.4, 0.6, 0.8, and 1) for PPD detection in an alkaline solution. PSC82 deposited onto glassy carbon electrode (PSC82/GCE) generates the highest redox currents which correlates with the highest hydrogen peroxide intermediates (HO2-) yield and the σ*-orbital (eg) filling of Co that is closest to unity for PSC82. PSC82/GCE provides the highest sensitivities of 655 and 308 µA mM-1 cm-2 in PPD concentration range of 0.5-2,900 and 2,900-10,400 µM, respectively, with a limit of detection of 0.17 µM. PSC82/GCE additionally demonstrates high selectivity to PPD and long term stability during 50 consecutive cyclic voltammetry scans and over 1-month storage period. The potential applicability of PSC82/GCE was also demonstrated by confirming the presence of very low concentration of PPD of below 0.5% in real hair dyes.

Detection of lawsone (2-hydroxy-1,4-naphthoquinone) in henna treated hair.

Hair analysis plays an important role in abstinence control in forensic toxicology. However, hair coloration affects the concentrations of xenobiotics and may lead to false negative results. For instance, henna has been shown to decrease ethyl glucuronide concentrations in hair. For analysis of the main henna ingredient lawsone (2-hydroxy-1,4-naphthoquinone), hair samples were washed, cut into small pieces (less than 5 mm), incubated (20 mg) in water and with internal standard (theophylline) for 24 h at 37 °C. Lawsone was analyzed in the supernatant using liquid chromatography with diode array detection. For quantitative assay, the absorption at 280 nm was found to be linear up to 250 ng/mg hair. The detection limit of lawsone was 2.2 ng/mg, precision and accuracy were better than 6%. Lawsone was only detectable in 12 henna-colored hair samples in concentrations from 27.3 to 253.7 (median 92.6) ng/mg. The analysis of lawsone is recommended in cases of suspected hair coloration where assessment of oxidative treatment was negative (e.g. no increase of 1H-pyrrole-2,3,5-tricarboxylic acid (PTCA) and unobtrusive fluorescence microscopy).

Microstructured prealloyed Titanium-Nickel powder as a novel nonenzymatic hydrogen peroxide sensor.

At present, commercial pure Titanium (Ti) and microstructured pre-alloyed Titanium-Nickel (TiNi) powders are employed as a sensitive electrochemical hydrogen peroxide (H2O2) sensor. Surface characterization of these materials are performed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical characterization is achieved via cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) on Ti and TiNi modified glassy carbon electrode (GCE). The electrochemical behavior of H2O2 at the pure Ti/GCE and microstructure pre-alloyed TiNi/GCE are studied by CV in 0.1 M phosphate buffer solution (PBS) containing as the supporting electrolyte. In addition, CA is employed for the determination of H2O2 at the applied potential of 0 V vs. Ag/AgCl. The sensor has a linear response range of 0.5-17.5 mM with a sensitivity of 280 µA mM-1 cm-2. Moreover, the limit of detection (LOD) and limit of quantification (LOQ) are 0.5 µM and 1.7 µM, respectively. The electrochemical sensor exhibits fast and selective responses to H2O2 concentration. The applicability of the sensor is checked using a hair coloring as a real sample with satisfactory results.

Skin sensitization quantitative risk assessment for occupational exposure of hairdressers to hair dye ingredients.

Occupational exposure of hairdressers to hair dyes has been associated with the development of allergic contact dermatitis (ACD) involving the hands. p-Phenylenediamine (PPD) and toluene-2,5-diamine (PTD) have been implicated as important occupational contact allergens. To conduct a quantitative risk assessment for the induction of contact sensitization to hair dyes in hairdressers, available data from hand rinsing studies following typical occupational exposure conditions to PPD, PTD and resorcinol were assessed. By accounting for wet work, uneven exposure and inter-individual variability for professionals, daily hand exposure concentrations were derived. Secondly, daily hand exposure was compared with the sensitization induction potency of the individual hair dye defined as the No Expected Sensitization Induction Levels (NESIL). For PPD and PTD hairdresser hand exposure levels were 2.7 and 5.9 fold below the individual NESIL. In contrast, hand exposure to resorcinol was 50 fold below the NESIL. Correspondingly, the risk assessment for PPD and PTD indicates that contact sensitization may occur, when skin protection and skin care are not rigorously applied. We conclude that awareness of health risks associated with occupational exposure to hair dyes, and of the importance of adequate protective measures, should be emphasized more fully during hairdresser education and training.