Simultaneous analysis of insect repellent DEET, sunscreen oxybenzone and five relevant metabolites by reversed-phase HPLC with UV detection: Application to an in vivo study in a piglet model

Association between percutaneous absorption of benzophenone-3 and N, N-diethyl-m-toluamide among the general adult population

BACKGROUND

Multiple studies have confirmed the mutual enhancement of percutaneous permeation of benzophenone-3 (BP-3) and N,N-diethyl-m-toluamide (DEET), which are effective ingredients in sunscreen products and insect repellents, respectively. However, the association between percutaneous absorption of BP-3 and DEET in a large general adult population remains to be elucidated.

METHODS

This cross-sectional study included US adults who had available data on urinary BP-3 and two DEET metabolites, 3-(diethylcarbamoyl) benzoic acid (DCBA) and 3-(ethylcarbamoyl) benzoic acid (ECBA), from the National Health and Nutrition Examination Survey (NHANES) conducted in 2015-2016. We conducted three weighted multivariable linear regression models to investigate the potential correlation between percutaneous absorption of BP-3 and DEET, along with trend tests, smooth curve fitting, and subgroup analysis to assess the robustness of the findings.

RESULTS

Weighted multivariable linear logistic regression revealed a positive correlation between log10 BP-3 and log10 DCBA (β = 0.1678, 95 % CI: 0.0970 to 0.2386) as well as log10 ECBA (β = 0.1416, 95 % CI: 0.0707 to 0.2125), after adjusting for all covariates. After converting log10 BP-3 from a continuous variable to a categorical variable (quartiles), the trend tests showed that the results were stable (all P for trend < 0.05). Smoothed curve fitting demonstrated a linear positive correlation between log10 BP-3 and both log10 DCBA and log10 ECBA. In subgroup analyses, the positive correlation between BP-3 and DEET metabolites was more pronounced in participants who were male, middle-aged, non-Hispanic white, had a moderate PIR level and reported always or most of the time using sunscreen.

CONCLUSIONS

Our findings revealed a statistically significant linear and positive correlation between the percutaneous absorption of BP-3 and DEET in the general adult population.

Prenatal exposure to benzophenone-type UV filters and the associations with neonatal birth outcomes and maternal health in south China

Benzophenone (BP)-type UV filters are commonly added to sunscreens and cosmetics to protect against UV radiation for human skin and hair. As a result, BPs are ubiquitous in the environment and human body, and their endocrine-disrupting characteristics have been a hot topic of discussion. However, our knowledge regarding the detrimental effects of prenatal exposure to BPs on pregnant women and their offspring remains limited. To fill this gap, we determined five BP derivatives in 600 serum samples obtained from pregnant women. All the target analytes, except 2,4-dihydroxybenzophenone (BP-1), have achieved a 100 % detection rate. The most prevalent compound was 2-hydroxy-4-methoxybenzophenone (BP-3), with a median concentration of 0.545 ng/mL. Significant and positive correlations were observed among BP derivatives, indicating both endogenous metabolism and common external sources. Utilizing Bayesian kernel machine regression (BKMR) and quantile-based g-computation (QGC) models, we found relationships between BP exposure and reduced neonatal birth weight (BW) and birth chest circumference (BC) during the third trimester. Notably, the adverse effect of BPs on birth size was sex-specific. Moreover, triglyceride (TG) was identified as a potential mediator of the effect of BPs on blood pressure, and co-exposure to BPs was linked to disruptions in thyroid hormone levels and glucose regulation. Further research is warranted to unravel the toxicity of BPs and their detrimental effects on pregnant women and fetuses.

Target analysis and suspect screening of UV filters, parabens and other chemicals used in personal care products in human cord blood: Prenatal exposure by mother-fetus transfer

Prenatal exposure to certain organic chemicals like pesticides and phenols has been lifelong associated with birth outcomes and health disorders. Many personal care product (PCP) ingredients have similar properties or structures to those chemicals. Previous studies have documented the occurrence of UV filters (UVFs) and paraben preservatives (PBs) in the placenta, but observational studies concerning PCPs chemicals and foetal exposure are particularly scarce. Thus, this work aimed to assess the presence of a wide range of PCPs chemicals using target and suspect screening in the umbilical cord blood of new born babies to evaluate their potential transfer to the fetus. To do so, we analysed 69 umbilical cord blood plasma samples from a mother-child cohort from Barcelona (Spain). We quantified 8 benzophenone-type UVFs and their metabolites, and 4 PBs using validated analytical methodologies based on target screening using liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Then, we screened for additional 3246 substances using high-resolution mass spectrometry (HRMS) and advanced suspect analysis strategies. Six UVFs and three parabens were detected in the plasma with frequencies between 1.4% and 17.4% and concentrations up to 53.3 ng/mL (benzophenone-2). Thirteen additional chemicals were tentatively identified in the suspect screening, and ten were further confirmed with the corresponding standards. Among them, we found the organic solvent N-methyl-2-pyrrolidone, the chelating agent 8-hydroxyquinoline, and the antioxidant 2,2'-methylenebis(4-methyl-6-tert-butylphenol), which have been demonstrated to display reproductive toxicity. UVFs and PBs presence in the umbilical cord blood demonstrates mother-fetus transfer through the placental barrier and prenatal exposure to these PCPs chemicals, which may lead to adverse effects in the early stages of fetal development. Considering the small cohort used in this study, the reported results should be interpreted as a preliminary reference for the background umbilical cord transfer levels of the target PCPs chemicals. Further research is needed to determine the long-term consequences of prenatal exposure to PCPs chemicals.

Assessment of human exposure to benzophenone-type UV filters: A review

To avoid the harmful effects of UV radiation, benzophenone-type UV filters (BPs) are widely used in personal care products and other synthetic products. Biomonitoring studies have shown the presence of BPs in various human biological samples, raising health concerns. However, there is a paucity of data on the global human exposure to this group of contaminants. In this study, we compiled data on the body burden of BPs along with the possible exposure routes and biotransformation pathways. BPs can easily penetrate the skin barrier and thus, they can be absorbed through the skin. In the human body, BPs can undergo Phase I (mainly demethylation and hydroxylation) and Phase II (mainly glucuronidation and sulfation) biotransformations. From a total of 158 studies, most of the studies are related to urine (concentration up to 92.7 mg L^-1), followed by those reported in blood (up to 0.9 mg L^-1) and milk (up to 0.8 mg L^-1). Among BPs, benzophenone-1 and benzophenone-3 are the most commonly detected congeners. The body burden of BPs is associated with various factors, including the country of residence, lifestyle, income, education level, and ethnicity. The presence of BPs in maternal urine (up to 1.1 mg L^-1), placenta (up to 9.8 ng g^-1), and amniotic fluid (up to 15.7 μg L^-1) suggests potential risks of prenatal exposure. In addition, transplacental transfer of BPs is possible, as demonstrated by their presence in maternal serum and cord serum. The possible association of BPs exposure and health effects was discussed. Future human biomonitoring studies and studies on the potential health effects are warranted. Overall, this review provides a summary of the global human exposure to BPs and can serve as supporting evidence to guide usage in order to protect humans from being exposed to BPs.

Mathematical filtration of quaternary mixture to the zero order spectra of its individual components

Simple accurate and precise validated UV spectrophotometric methods have been described here for the simultaneous determination of Tretinoin (TN) Eusolex (EX) Hydroquinone (HQ) & Hydrocortisone acetate (HC) in their dosage form. Simultaneous determination of these four drugs was a major challenge till now. Each spectrum was filtered alone to its zero-order absorption spectrum (D⁰) form getting spectra typical to each pure component separately. Four methods were applied depending upon constants obtained from extended regions of partially overlapped spectra in the zero or first derivative forms. The methods applied are constant multiplication coupled with spectrum subtraction method (CM-SS) derivative transformation coupled with spectrum subtraction method (DT-SS) constant value method (CV) and concentration value (conc.value) method. The partially overlapped spectra of TN and EX in the mixture were obtained by CM-SS in their zero-order form allowing direct measurement at their λ_max while the resolved binary mixture of HQ and HC obtained by SS; was determined by derivatization and transformed to their zero order by DT-SS. Also Ex and HQ concentrations were determined by the graphical representation of data only without regression equation by concentration value method and the results were compared to the conventional constant value method using a regression equation. The methods applied to the quaternary mixture under study were successfully applied for the simultaneous determination of the four drugs in synthetic mixtures and in their combined dosage form Tritospot® cream. Comparing the acquired results statistically together and to official methods demonstrated no significant difference.

Development and Validation of a Simple HPLC-UV Method to Assay DEET Repellents and its Application to Different Commercial Forms

Background:

N’,N’-diethyl-m-toluamide (DEET) is the most widely used repellent substance worldwide. It is formulated as aerosol, solution, lotion, gel and patches. However, the official compendia report monographs to analyze only DEET drug substance and solution.

Objective:

In this study an isocratic HPLC method was validated to assay DEET in lotion, gel and solution, under the same analytical conditions.

Methods:

The method was validated according to ICH requirements and DEET detection was achieved at around 11 min, using a C-18 column, a mobile phase composed by methanol, acetonitrile and water pH 4.5 (45:10:45), flow rate at 1 mL min-1and detection at 270 nm.

Results:

A linear relationship was observed in the range of 2.5 to 100 μg mL-1, the method was precise (relative standard deviation<2%) and accuracy was demonstrated by DEET recovery values ranging from 99.5 to 100.2%. The specificity was studied by a forced degradation test, where degradation products were observed after alkaline degradation and ultraviolet radiation. Appropriate resolution between DEET, degradation products and excipient peaks indicated the method specificity. Robustness was evaluated by a full factorial design, and no effect on DEET assay was observed under simultaneous variation in analytical parameters. The method was applied to assay nine marketed formulations, demonstrating its good applicability.

Conclusion:

The validated HPLC method was successfully applied to the quantitative analysis of DEET in lotion, gel and solution, contributing to improve the quality control and the efficacy of these formulations.

On the IR spectroscopy and chemometric based rapid and non-destructive method for the investigation of sunscreen stains: Application in forensic science

Cosmetic products such as sunscreens may often be encountered in forensic investigations as traces left on tissue paper, apparels, drinkware, painted exterior, or various alternative surfaces. The pilot study aimed at efficiently using Infrared spectroscopy coupled with chemometrics to cater to unbiased, rapid, and non-destructive identification of sunscreens which will aid various forensic investigations soon. In the present research, a total of 109 sunscreen samples were analyzed using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. The physicochemical data from the FTIR instrument was then subjected to principal component analysis (PCA), which successfully distinguished most of the samples based on their spectral information. The trained model resulted in clear segregation of unknown sunscreen samples. This could provide an outstanding level of confidence during the conduction of 'questioned versus known' comparisons of similar sunscreens and will give the details of the manufacturer, thereby, helping in rounding off the suspects.

Chemometric-assisted UV spectrophotometric method for determination of N, N- diethyl-3-methylbenzamide in insect repellents

In recent years outbreaks of vector-borne diseases have caused great concern to the population, especially those diseases transmitted by mosquitoes. Repellents appear as an affordable alternative for prevention, making it increasingly important to control the quality of these products, since the content of the active ingredients are directly related to the efficiency and the protection time provided by the repellent. This paper proposes an analytical method for determining the DEET (N, N- Diethyl-3-methylbenzamide) content in insect repellents in lotion using UV spectroscopy. For this propose five different strategies of regression were evaluated: (a) Partial Least Squares (PLS) using full-spectrum; (b) interval PLS (iPLS); Multiple Linear Regression (MLR) with variable selection by the (c) Genetic Algorithm (MLR/GA), (d) Successive Projections Algorithm (MLR/SPA) and the (e) Stepwise (MLR/SW). Appropriate predictions were obtained with RMSEP values between 0.88 and 0.93%w w^-1. No systematic error was observed and no significant differences were found between the predicted and reference values, according to a paired t-test at 95% confidence level. The results demonstrated the potential of UV spectroscopy associated to multivariate calibration to determine DEET content in repellents as a fast, simple strategy and with a suitable correlation between the values estimated by the model and the reference values.

Metabolism and disposition of 2-hydroxy-4-methoxybenzophenone, a sunscreen ingredient, in Harlan Sprague Dawley rats and B6C3F1/N mice; a species and route comparison

2-Hydroxy-4-methoxybenzophenone (HMB) is a common ingredient in personal care products and used as an UV stabilizer. In these studies, disposition and metabolism of [¹⁴C]HMB in rats and mice was assessed following single gavage administration (10, 100, or 500 mg/kg), single IV administration (10 mg/kg), or dermal application (0.1, 1, 10, or 15 mg/kg).Following gavage administration, [¹⁴C]HMB was well absorbed and excreted mainly in urine (39-57%) and feces (24-42%) with no apparent difference between doses, species or sexes. Distribution of HMB in tissues was minimal in rats (0.36%) and mice (<0.55%).Distribution of HMB following dermal application was comparable to that following gavage administration; no differences between doses, sexes, or species were observed but absorption varied between dose vehicles. Light paraffin oil had the highest absorption and excretion (98% of the HMB dose absorbed).In rats, HMB slowly appeared in the systemic circulation (T_max ∼2-6 h) and had poor bioavailability (F%<1).Urine metabolites for both species and all routes included HMB, HMB-glucuronide, 2,4-dihydroxybenzophenone (DHB), DHB-glucuronide, and DHB-sulfates, and novel minor dihydroxy metabolites including 2,5-dihydroxy-4-methoxybenzophenone.In vitro hepatic metabolism in mice differed from human and in vivo metabolism especially for phase II conjugates.

Phototoxic risk assessment on benzophenone UV filters: In vitro assessment and a theoretical model

Benzophenones (BPs), filtering out both UVA and UVB rays, are widely used in a great variety of sunscreens and personal care products. However, they have not been extensively studied for the mechanisms of UV-absorbing toxicity. In this study, we used CPZ (chlorpromazine) as a positive control and SDS (sodium dodecyl sulfate) as a negative control, and the phototoxic of BP-1, BP-3 and BP-4 were investigated in vitro assays using three cell types under different UV exposure conditions. This was followed by setting up a theoretical model, which was adopted to predict and compare the phototoxicity. It was found that Balb/c 3T3 (Balb/c 3T3 fibroblast cell lines) showed sensitivity to UVA+ and UVB+ exposure, while the HS68 (human HS68 fibroblast cell lines) to UVA+ and the HaCaT (human HaCaT keratinocyte cell lines) to UVB+. The test compound, BP-1, was detected to be phototoxic at UVA+ conditions, but BP-3 and BP-4 were discovered to be non-phototoxic at UVA+ conditions. This demonstrated that BP-1, BP-3 and BP-4 remained low-risk chemicals under UVB+ condition. The theoretical calculation of the energy gap (E_GAP) showed BP-1(E_GAP) > BP-3(E_GAP) > BP-4(E_GAP).

Urinary benzophenone-type UV filters in people living in South China: rural versus urban areas

Benzophenone (BP)-type UV filters are widely used in sunscreen products to protect human skin from UV radiation. However, only a few studies have been conducted to determine the level of human exposure to BPs in rural areas of China. In this study, we evaluated the exposure levels of people living in three villages and a city in South China to five major BPs (BP-1, BP-2, BP-3, BP-8, and 4-OH-BP). The detection rates of BP-1, BP-3, and 4-OH-BP were 66%, 72%, and 75%, respectively, in rural areas and 85%, 75%, and 80%, correspondingly, in urban areas. BP-2 and BP-8 were rarely detected. The results indicated that people living in South China are extensively exposed to BPs, regardless of sampling sites (rural and urban areas). The observed concentrations of BP-1 (urban vs. rural = 1.04 ng mL^-1vs. 0.21 ng mL^-1) and BP-3 (0.37 ng mL^-1vs. 0.16 ng mL^-1) were significantly (one-way ANOVA, p < 0.01) lower in the rural areas than in the urban areas. BP-1 (59%) based on composition profile analysis was the dominant BP derivative in urine samples of urban residents, whereas 4-OH-BP (36%) was the most prevalent BP in rural areas. In the rural areas, significant positive correlations between urinary BP-1 and BP-3 (r = 0.529, p < 0.01) and between urinary BP-1 and 4-OH-BP (r = 0.323, p < 0.05) concentrations were obtained; in the urban areas, we only observed a clear correlation (p < 0.01) between BP-1 and 4-OH-BP. The different composition profiles and associations among urinary BPs indicated that exposure sources of BPs might be different between rural and urban areas. The distribution profiles of BP-1 and its parent compound (i.e., BP-3) in urine decreased with the age of adults (r = -0.410, p < 0.01) in the rural areas.

Exposure to benzophenones, parabens and triclosan among pregnant women in different trimesters

Humans are potentially exposed to many environmental pollutants, many of which may cause adverse health effects, especially to pregnant women and their fetuses. In this study, 11 environmental pollutants from three different chemical classes, including benzophenones, parabens and triclosan were measured in 627 urine samples collected from 209 pregnant women to evaluate exposure and trends as a function of pregnancy stage. Methylparaben (MeP), ethylparaben, propylparaben (PrP), butylparaben, 2,4-dihydroxybenzophenone (BP-1), 2-hydroxy-4-methoxybenzophenone (BP-3) and 4-hydroxybenzophenone were detected in >50% samples. The concentrations of BP-1 and BP-3 (Spearman's r=0.57, p<0.01) and those of MeP and PrP (Spearman's r=0.68, p<0.01) were found to be correlated. The urinary concentrations of BP-1 and BP-3 in the first trimester were significantly higher than those in the second or third trimester (Mann-Whitney U test, p<0.05). These findings provide valuable information for improving the prediction of maternal exposure to these emerging pollutants and for assessing their potential health risks to the mother as well as the offspring.

Benzonphenone-type UV filters in urine of Chinese young adults: Concentration, source and exposure

Benzophenone (BP)-type UV filters are commonly used in our daily life. 2-hydroxy-4-methoxy benzophenone (BP-3), 4-hydroxy benzophenone (4-HBP), 2,4-dihydroxy benzophenone (BP-1), 2,2',4,4'-tetrahydroxy benzophenone (BP-2) and 2,2'-dihydroxy-4-methoxy benzophenone (BP-8) were measured in urine samples from Chinese young adults. The results indicated that Chinese young adults were widely exposed to BP-3, BP-1, and 4-HBP, with the median concentrations of 0.55, 0.21, and 0.08 ng/mL, respectively. No significant difference was found between males and females, between urban and rural population. The correlations between urinary concentrations provided important indications for sources and metabolic pathways of target compounds. The estimated daily excretion doses of BP-3, 4-HBP, BP-1, BP-2 and BP-8 were 27.2, 2.24, 5.86, 0.76 and 0.30 ng/kg-bw/day, respectively. The ratio of exposure to excretion must be considered for the exposure assessment with chemicals based on urine measurement. This is the first nationwide study on BP-derivatives with young adults in China.

Assessment of dermal absorption of DEET-containing insect repellent and oxybenzone-containing sunscreen using human urinary metabolites

Mutual enhancement of dermal absorption of N,N-diethyl-m-toluamide (DEET) and oxybenzone (OBZ) has been reported recently with DEET and OBZ being active ingredients of insect repellent and sunscreen, respectively. To assess the reported enhancing effect directly, we used human urinary metabolites as biomarkers; besides, we also sought to determine the best way for concurrent use of these two products without extra absorption of either. Four dermal application methods were used: DEET only (S1), OBZ only (S2), DEET on top of OBZ (S3), and OBZ on top of DEET (S4). Among the study methods, there was a significant difference (p = 0.013), which was attributed to the difference between S1 and S4, suggesting that applying OBZ over DEET on the skin lead to significantly higher absorption of DEET. Using both products in reverse order, (S3) did not result in extra DEET absorption significantly. As for OBZ permeation, no significant difference was observed among the methods. In summary, the enhancement of DEET absorption is confirmed for OBZ being applied over DEET on the skin; should concurrent use of both be necessary, applying sunscreen (OBZ) first and then insect repellent (DEET) with a 15-min interval is recommended.

Widespread occurrence of bisphenol A diglycidyl ethers, p-hydroxybenzoic acid esters (parabens), benzophenone type-UV filters, triclosan, and triclocarban in human urine from Athens, Greece

Biomonitoring of human exposure to bisphenol A diglycidyl ethers (BADGEs; resin coating for food cans), p-hydroxybenzoic acid esters (parabens; preservatives), benzophenone-type UV filters (BP-UV filters; sunscreen agents), triclosan (TCS; antimicrobials), and triclocarban (TCC; antimicrobials) has been investigated in western European countries and North America. Nevertheless, little is known about the exposure of Greek populations to these environmental chemicals. In this study, 100 urine samples collected from Athens, Greece, were analyzed by liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the determination of total concentrations of five derivatives of BADGEs, six parabens and their metabolite (ethyl-protocatechuate), five derivatives of BP-UV filters, TCS, and TCC. Urinary concentrations of BADGEs, parabens, ethyl-protocatechuate, BP-UV filters, TCS and TCC (on a volume basis) ranged 0.3-20.9 (geometric mean: 0.9), 1.6-1010 (24.2), <2-71.0 (2.1), 0.5-1120 (4.4), <0.5-2580 (8.0) and <0.5-1.9 (0.6) ng/mL, respectively. All 19 target chemicals were found in urine, and the highest detection rates were observed for methyl paraben (100%), bisphenol A bis (2,3-dihydroxypropyl) ether (90%), ethyl paraben (87%), 2,4-dihydroxybenzophenone (78%), propyl paraben (72%), and TCS (71%). Estimated daily intakes (EDIurine), calculated on the basis of the measured urinary concentrations, ranged from 0.023 μg/kg bw/day for Σ5BADGEs to 31.4 μg/kg bw/day for Σ6Parabens.

Molecular interactions of benzophenone UV filters with human serum albumin revealed by spectroscopic techniques and molecular modeling

Benzophenone (BP)-type UV filters have been widely used in many personal care products to protect human from UV exposure. Their dermal applications can cause direct human health risk following accumulation in bloodstream. Few studies have addressed whether BP-type UV filters could bind and alter the structure and function of human serum albumin (HSA), the major carrier protein in plasma. Four benzophenones, BP-1, BP-2, BP-3 and BP-8 were selected to investigate their potentially toxic interactions with HSA and the intrinsic binding mechanism using combined spectroscopies and molecular docking techniques. Four benzophenones significantly quench the intrinsic fluorescence of HSA via static mode. The competitive binding fluorescence assay and molecular docking both revealed that the benzophenones bind at site II of HSA. Their binding constants range from 1.91 × 10(4)M(-1) to 12.96 × 10(4)M(-1) at 296 K. BP-8 interacts with HSA mainly through hydrogen bonding interactions and van der Waals interactions, while hydrophobic interactions and electrostatic interactions are dominant for interactions between BP-1, BP-2, BP-3 and HSA. Molecular docking revealed that the changes in structural moiety and hydrophobicity of four benzophenones account for their different binding affinities. As further revealed by circular dichroism and time-resolved fluorescence decay, these benzophenones cause global and local structural changes of HSA, which illustrates their potential toxicity to cause structural damage of HSA. Two degradation products of BP-3 have higher binding affinities to HSA, suggesting higher potencies in causing adverse effects on human health.

Benzophenone-type UV filters in urine and blood from children, adults, and pregnant women in China: partitioning between blood and urine as well as maternal and fetal cord blood

Limited information exists on the exposure of benzophenone (BP)-type UV filters (i.e., sunscreen compounds) in children, adults, and pregnant women in China. In this study, we determined the concentrations of five BP derivatives, BP-1, BP-2, BP-3, BP-8, and 4OH-BP in urine (n=101) as well as paired specimens of blood and urine (n=24 pairs) collected from adults; in matched maternal and fetal cord blood (n=20 pairs) collected from pregnant women; and in blood collected from children (n=10). 4OH-BP, BP-1, and BP-3 were found in 61%, 57%, and 25%, respectively, of the urine samples analyzed. 4OH-BP was found in all blood samples; BP-3 was found more frequently in the blood of adults (83%), followed, in decreasing order, by pregnant women (35%) and children (30%). Among all adults, urinary BP-3 concentrations were significantly (p<0.001) positively correlated with urinary BP-1 concentrations. Nevertheless, no significant correlations were found between urinary concentrations of BP-3 (or BP-1) and 4OH-BP. Our results suggest that human exposure to BP-3 and BP-1 is related, whereas 4OH-BP originates from a discrete source. Females had higher urinary concentrations of BP-3, BP-1 and 4OH-BP than males. The distribution profiles of BP-1 and its parent compound (i.e., BP-3) in urine decreased with increasing age of donors (p<0.05). The ratio of concentrations of BP-3 between blood and urine was 0.21 in adults, which was significantly lower than that for 4OH-BP (0.36). The concentration ratio of BPs between cord blood and maternal blood was higher for 4OH-BP (0.61) than that for BP-3 (0.48), which suggested greater trans-placental transfer potential of 4OH-BP. This is the first study to document the occurrence of BPs in paired urine and blood, and in matched maternal and fetal cord blood.

On-line solid phase extraction-high performance liquid chromatography-isotope dilution-tandem mass spectrometry approach to quantify N,N-diethyl-m-toluamide and oxidative metabolites in urine

Human exposure to N,N-diethyl-m-toluamide (DEET) occurs because of the widespread use of DEET as an active ingredient in insect repellents. However, information on the extent of such exposure is rather limited. Therefore, we developed a fast on-line solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) method to measure in urine the concentrations of DEET and two of its oxidative metabolites: N,N-diethyl-3-(hydroxymethyl)benzamide and 3-(diethylcarbamoyl)benzoic acid (DCBA). To the best of our knowledge, this is the first HPLC-MS/MS method for the simultaneous quantification of DEET and its select metabolites in human urine. After enzymatic hydrolysis of the conjugated species in 0.1 mL of urine, the target analytes were retained and pre-concentrated on a monolithic column, separated from each other and from other urinary biomolecules on a reversed-phase analytical column, and detected by atmospheric pressure chemical ionization in positive ion mode. The limits of detection ranged from 0.1 ng mL(-1) to 1.0 ng mL(-1), depending on the analyte. Accuracy ranged between 90.4 and 104.9%, and precision ranged between 5.5 and 13.1% RSD, depending on the analyte and the concentration. We tested the usefulness of this method by analyzing 75 urine samples collected anonymously in the Southeastern United States in June 2012 from adults with no known exposure to DEET. Thirty eight samples (51%) tested positive for at least one of the analytes. We detected DCBA most frequently and at the highest concentrations. Our results suggest that this method can be used for the analysis of a large number of samples for epidemiological studies to assess human exposure to DEET.

Chemometrics assisted dispersive liquid-liquid microextraction for quantification of seven UV filters in urine samples by HPLC-DAD

In the present study, dispersive liquid-liquid microextraction followed by high performance liquid chromatography-diode array detection has been developed as simple, rapid, accurate, and efficient sample preparation method for simultaneous determination of seven organic UV filters in urine samples. The influence of the main effects as well as their interactions was studied through a 2((6-2)) fractional factorial design. The candidate parameters were: type and volume of dispersant and extraction solvents, sample pH, and salt concentration. Under final optimal conditions, the analytes were extracted from 5 mL of samples by addition of 0.5 mL of acetonitrile (dispersing solvent) containing 70 μL of carbon tetrachloride (extraction solvent), without modifying the pH of the solution and applying the (+1) level of salt concentration (10% w/v NaCl). The assay was linear (R(2) > 0.997), relative recoveries ranged from 86.9 up to 97.3% and the LOQs between 3 and 45 ng mL(-1) were obtained. The intra- and interday RSDs were lower than 5 and 8% at the middle point of the linear range, respectively. The proposed method was successfully applied to different volunteer urine samples and it was shown that the extraction efficiency was not affected by the type of urine samples.

Metabolic disposition of the insect repellent DEET and the sunscreen oxybenzone following intravenous and skin administration in rats

Insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone have shown a synergistic percutaneous enhancement when applied concurrently. Both compounds are extensively metabolized in vivo into a series of potentially toxic metabolites: 2 metabolites of DEET, N,N-diethyl-m-hydroxymethylbenzamide (DHMB) and N-ethyl-m-toluamide (ET), and 3 metabolites of oxybenzone, 2,4-dihydroxybenzophenone (DHB), 2,2-dihydroxy-4-methoxybenzophenone (DMB), and 2,3,4-trihydroxybenzophenone (THB). In this study, the metabolites were extensively distributed following intravenous and topical skin administration of DEET and oxybenzone in rats. Combined application enhanced the disposition of all DEET metabolites in the liver but did not consistently affect the distribution of oxybenzone metabolites. The DHMB appeared to be the major metabolite for DEET, while THB and its precursor DHB were the main metabolites for oxybenzone. Repeated once-daily topical application for 30 days led to higher concentrations of DEET metabolites in the liver. Hepatoma cell studies revealed a decrease in cellular proliferation from all metabolites as single and combined treatments, most notably at 72 hours. Increased accumulation of DHMB and ET in the liver together with an ability to reduce cellular proliferation at achievable plasma concentrations indicated that simultaneous exposure to DEET and oxybenzone might have the potential to precipitate adverse effects in a rat animal model.

Urinary concentrations of benzophenone-type UV filters in U.S. women and their association with endometriosis

Benzophenone (BP)-type UV filters are widely used in a variety of personal care products for the protection of skin and hair from UV irradiation. Despite the estrogenic potencies of BP derivatives, few studies have examined the occurrence of these compounds in human matrices. Furthermore, associations among exposure to these compounds and estrogen-dependent diseases (such as endometriosis) have not been examined previously. In this study, we determined the concentrations of five BP derivatives, 2-hydroxy-4-methoxybenzophenone (2OH-4MeO-BP), 2,4-dihydroxybenzophenone (2,4OH-BP), 2,2'-dihydroxy-4-methoxybenzophenone (2,2'OH-4MeO-BP), 2,2',4,4'-tetrahydroxybenzophenone (2,2',4,4'OH-BP), and 4-hydroxybenzophenone (4OH-BP), in urine collected from 625 women in Utah and California, using liquid chromatography (LC)-tandem mass spectrometry (MS/MS). The association of urinary concentrations of BP derivatives with an increase in the odds of a diagnosis of endometriosis was examined in 600 women who underwent laparoscopy/laparotomy (n = 473: operative cohort) or pelvic magnetic resonance imaging (n = 127: population cohort), during 2007-2009. 2OH-4MeO-BP, 2,4OH-BP, and 4OH-BP respectively were detected in 99.0%, 93.3%, and 83.8% of the urine samples analyzed, whereas the detection rates for 2,2',4,4'OH-BP and 2,2'OH-4MeO-BP were below 6.0%. Significant regional differences (higher concentrations in California) and monthly variations (higher concentrations in July and August) were found for urinary concentrations of 2OH-4MeO-BP and 2,4OH-BP. In addition, urinary concentrations of 2OH-4MeO-BP and 2,4OH-BP tended to be higher in more affluent, older, and leaner women. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for the urinary concentrations of BP derivatives and the odds of an endometriosis diagnosis; ORs increased across quartiles of 2OH-4MeO-BP and 2,4OH-BP concentrations, but a significant trend was observed only between 2,4OH-BP and the odds of an endometriosis diagnosis in the operative cohort (OR = 1.19; 95% CI = 1.01, 1.41). When women in the highest quartile of 2,4OH-BP concentrations were compared with women in the first three quartiles, the OR increased considerably (OR = 1.65; 95% CI = 1.07, 2.53). Given that 2,4OH-BP possesses an estrogenic activity higher than that of 2OH-4MeO-BP, our results invite the speculation that exposure to elevated 2,4OH-BP levels may be associated with endometriosis.

Determination of benzotriazole and benzophenone UV filters in sediment and sewage sludge

Benzophenones and benzotriazoles are widely used as ultraviolet (UV) light filters and stabilizers in cosmetics, skin creams, and body lotions and as corrosion inhibitors in building materials, automobile components, and automotive antifreeze cooling systems. Benzophenones and benzotriazoles have been reported to occur in the environment. Some of these UV filters have been reported to possess significant estrogenic activity. Despite this, very few studies have examined their occurrence and profiles in the environment. In this work, we determined five benzophenone-type UV filters and two benzotriazole-type corrosion inhibitors, namely, 2-hydroxy-4-methoxybenzophenone (2OH-4MeO-BP), 2,4-dihydroxybenzophenone (2,4OH-BP), 2,2'-dihydroxy-4-methoxybenzophenone (2,2'OH-4MeO-BP), 2,2',4,4'-tetrahydroxybenzophenone (2,2',4,4'OH-BP), 4-hydroxybenzophenone (4OH-BP), 1H-benzotriazole (1H-BT), and 5-methyl-1H-benzotriazole (5Me-1H-BT), in sediment and sewage sludge samples, using liquid-liquid extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In addition, four benzotriazole-type UV stabilizers, namely, 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole (UV-326), 2,4-di-t-butyl-6-(5-chloro-2H-benzotriazole-2-yl) phenol (UV-327), 2-(2H-benzotriazole-2yl)-4,6-di-t-pentylphenol (UV-328), and 2-(5-t-butyl-2-hydroxyphenyl) benzotriazole (TBHPBT) were determined by gas chromatography (GC)-mass spectrometry (MS). The limits of quantitation (LOQ) were in the ranges of 0.06-0.33 ng g⁻¹ dry weight (dw) and 0.1-1.65 ng g⁻¹ dw for sediment and sludge samples, respectively. Recoveries of target compounds spiked into sample matrices and passed through the entire analytical procedure ranged from 70% to 116% (RSD: 3.32-13.8%) and from 82% to 106% (RSD: 2.89-8.09%) for the compounds analyzed by LC-MS/MS and GC-MS, respectively. The methods were applied to the analysis of sediment samples from the Songhua, Saginaw, and Detroit Rivers; the sum concentrations of target compounds were 3.29-9.93, 5.81-22.5, and 190-389 ng g⁻¹ dw, respectively. Five sludge samples collected from five wastewater treatment plants in northeastern China contained the sum concentrations of target compounds in the range of 104-6370 ng g⁻¹ dw. The concentration of UV-328 in sludge was the highest (mean: 1300 ng g⁻¹ dw) among the target compounds. To our knowledge, this is the first work to report the occurrence of 2OH-4MeO-BP, 2,4OH-BP, 2,2'OH-4MeO-BP, 2,2',4,4'OH-BP, and 4OH-BP in sediment and sludge samples.

Tissue deposition of the insect repellent DEET and the sunscreen oxybenzone from repeated topical skin applications in rats

Insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone are capable of enhancing skin permeation of each other when applied simultaneously. We carried out a cellular study in rat astrocytes and neurons to assess cell toxicity of DEET and oxybenzone and a 30-day study in Sprague-Dawley rats to characterize skin permeation and tissue disposition of the compounds. Cellular toxicity occurred at 1 µg/mL for neurons and 7-day treatment for astrocytes and neurons. DEET and oxybenzone permeated across the skin to accumulate in blood, liver, and brain after repeated topical applications. DEET disappeared from the application site faster than oxybenzone. Combined application enhanced the disposition of DEET in liver. No overt sign of behavioral toxicity was observed from several behavioral testing protocols. It was concluded that despite measurable disposition of the study compounds in vivo, there was no evidence of neurotoxicological deficits from repeated topical applications of DEET, oxybenzone, or both.

Current sunscreen issues: 2007 Food and Drug Administration sunscreen labelling recommendations and combination sunscreen/insect repellent products

The Food and Drug Administration (FDA) regulates sunscreens as over-the-counter drugs. This article describes sunscreen actives available in the United States, new developments available elsewhere, and the amendment to the FDA 1999 sunscreen monograph, released on August 27, 2007, which proposes a new grading system for ultraviolet B protection, a cap of the sunburn protection factor to 50+, and a 4-star grading of ultraviolet A protection. In addition, current data on combination sunscreen and insect repellent products are discussed. Application of a combination product too frequently poses the risk of insect repellent toxicity, whereas application too infrequently invites photodamage. It may be prudent to follow the same approach of our Canadian colleagues of discontinuing combination products until more investigations are available.

Sensitive determination of free benzophenone-3 in human urine samples based on an ionic liquid as extractant phase in single-drop microextraction prior to liquid chromatography analysis

Benzophenone-3 (BZ3), one of the compounds most commonly used as UV filter in cosmetic products, can be absorbed through the skin into the human body, since it can be found at trace levels in urine from users of cosmetic products that contain BZ3. Moreover, different undesirable effects have been attributed to this compound. Thus, sensitive analytical methods to monitor urinary excretion of this compound should be developed. This paper presents a selective and sensitive methodology for BZ3 determination at ultratrace levels in human urine samples. The methodology is based on a novel microextraction technique, known as single-drop microextraction (SDME). An ionic liquid (IL) has been used as extractant phase instead of an organic solvent. After the microextraction process, the extractant phase was injected into a liquid chromatography system. The variables of interest in the SDME process were optimized using a multivariate optimization approach. A Plackett-Burman design for screening and a circumscribed central composite design for optimizing the significant variables were applied. Ionic strength, extraction time, stirring speed, pH, ionic liquid type, drop volume and sample volume were the variables studied. The optimum experimental conditions found were: sodium chloride concentration, 13% (w/v); extraction time, 25 min; stirring speed, 900 rpm; pH, 2; ionic liquid type, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)MIM][PF(6)]); drop volume, 5 microL; and sample volume, 10 mL. The proposed method requires a standard addition calibration approach, and it has been successfully employed to determine free BZ3 in urine samples coming from human volunteers who applied a sunscreen cosmetic containing this UV filter. The limit of detection was in the order of 1.3 ng mL(-1) and repeatability of the method, expressed as relative standard deviation, was 6% (n=8).

Quantitative and qualitative determination of dimethyl phthalate and N, N-diethyl-m-toluamide in repellents commercial formulations by high performance thin layer chromatography

In this study HPTLC was used for simultaneous quantitative and qualitative determination of N, N-diethyl meta toluamide (DEET) and dimethyl phthalate (DMP), which are the main elements and active ingredients in current chemical repellents. Some defined amounts of commercial form of 3 repellents included trench pomade, stick insect repellent (SIR), which is containing 33% of DEET and DMP60 (dimethyl phthalate 60%) dissolved in ethyl acetate solvent, separately. The method employed TLC aluminum plate precoated with silica gel plates (SiO4) 60F245 as the stationary phase. The solvent system consisted of benzene-diethyl etherhexane (5:3:2, v/v/v) as mobile phase. The multiple level method used for spotting. Densitometric analysis of repellents was carried out using TLC scanner 3 and CATS4 software in the absorption/reflection mode at 230 nm. According to the results, the type and amount of active ingredients in DMP60 lotion was 61.8 g (SE = +/-1.6) per 100 cc and in SIR, 31.3 g (SE = +/-0.8) diethyl meta toluamide per 100 g of repellents raw materials. Also the active ingredients in trench pomade were determined as a combination of DMP and DEET by rates of 5.5 g (SE = +/-0.2) and 25 g (SE = +/-l) per 100 g repellents commercial formulations, respectively. In this study, the value of Rf for DMP and DEET was calculated 0.71 +/- 0.2 and 0.32 +/- 0.2, respectively. HPTLC is a suitable method to quantitatively and quantitatively determine repellents which have DMP and DEET active ingredients. Since most of commercial chemical repellents have this active ingredient, adjusting and setting HPTLC up can be important.

Simultaneous determination of p-aminobenzoic acid and its metabolites in the urine of volunteers, treated with p-aminobenzoic acid sunscreen formulation

p-Aminobenzoic acid (PABA) and its metabolites (p-aminohippuric acid, p-acetamidobenzoic acid, and p-acetamidohippuric acid) were detected using high-performance liquid chromatography with an electrochemical (carbon paste) detector (HPLC-ECD). For direct current (dc) mode, with the current at a constant potential, and measurements with suitable experimental parameters, a linear concentration from 0.125 to 1.80 microg/ml was found. The detection limit was approximately 2.0 ng/ml. A carbon paste coulometric detector was used to demonstrate that PABA and its metabolites are electrochemically oxidized in acidic media, and to determine, by analyzing human urine, the percutaneous absorption of PABA and its metabolites. Findings using HPLC-ECD and HPLC with an ultraviolet detector (HPLC-UV) were comparable.

In vitro permeation of repellent DEET and sunscreen oxybenzone across three artificial membranes

DEET and oxybenzone are two essential active ingredients in repellent and sunscreen products. We performed a series of in vitro diffusion studies to evaluate the transmembrane permeation of DEET and oxybenzone across three artificial membranes, low-density polyethylene (LDPE), low fouling composite (LFC) and mixed cellulose esters (MCE), from concurrent use of commercial repellent and sunscreen preparations. Permeation of DEET and oxybenzone across the test membranes was synergistically increased when both the repellent and the sunscreen formulations were applied simultaneously. Different application sequences and formulation types also resulted in variable permeation profiles of DEET and oxybenzone. Compared to biological piglet epidermis under the identical experimental conditions, transmembrane permeation of DEET was suppressed in LDPE and LFC membranes, but enhanced in MCE membrane; transmembrane permeation of oxybenzone was reduced in LFC membrane, but increased in LDPE and MCE membranes. Permeability coefficients of DEET and oxybenzone in all three artificial membranes were significantly different from those in piglet skin. It was concluded that the permeation profiles of the compounds were dependent upon physicochemical characteristics of the membranes and the formulations.