A time trend of urinary 4-methylbenzylidene camphor metabolites in young adults from Germany

4-methylbenzylidene camphor (4-MBC) is used as a UV-B filter in cosmetics. Two oxidized metabolites of 4-MBC - 3-(4-carboxybenzylidene)camphor (cx-MBC) and 3-(4-carboxybenzylidene)-6-hydroxycamphor (cx-MBC-OH) - were analyzed in 250 24-h urine samples from young adults in Germany. The samples were from the German Environmental Specimen Bank (ESB) and represented exposure in the years 1995, 2005, 2010, 2015 and 2019. A UHPLC-MS/MS method enabled the sensitive determination of both metabolites, with limits of quantification at 0.15 μg L^-1 (cx-MBC) and 0.30 μg L^-1 (cx-MBC-OH), respectively. A temporal trend of the internal exposure to 4-MBC was clearly noticeable. The metabolite cx-MBC was frequently quantifiable at the beginning of the period: in 70% of the samples in 1995, and 56% in 2005. After 2005, urinary concentrations and detection rates of cx-MBC dropped to reach very low levels. In 2015 and 2019, the detection rate was only 2% and 0%, respectively. A similar trend was observed for cx-MBC-OH, though overall, this metabolite was detected less often and at lower concentration levels than cx-MBC. Nowadays, measurable levels of urinary 4-MBC metabolites are an extremely rare occurrence in Germany. These trends are consistent with the history of 4-MBC use by the cosmetic industry. The highest measured individual concentration of 16.20 μg L^-1 (in a sample of the year 2005) was still more than 30 times below the health-based guidance value (HBM-I). An investigation of the ratios between both metabolites uncovered several features of the 4-MBC metabolism which have been essentially overlooked until now. In particular, stereochemical aspects should be explored in future studies. As urine was collected in autumn/winter in Northwestern Germany, the 4-MBC metabolites measured probably do not arise from sunscreen products in a narrow sense. They rather may reveal the use of other skin care products containing 4-MBC for UV protection as an added feature.

A "dilute-and-shoot" column-switching UHPLC-MS/MS procedure for the rapid determination of branched nonylphenol in human urine: method optimisation and some fundamental aspects of nonylphenol analysis

Technical grade branched nonylphenol (NP) was determined in human urine by online solid phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS). Prior to analysis, urine specimens were simply diluted and enzymatically deconjugated. The run time of the chromatography, including SPE and re-equilibration, was 9 min per injection. The enzymatic cleavage of NP conjugates was optimised with incurred sample material from a human metabolism study: the highest recoveries were obtained with β-glucuronidase from E. coli K 12 in 0.1 M ammonium acetate at pH 6.5, within a minimal hydrolysis time of 30 to 60 min. Using sodium acetate instead of ammonium acetate led to systematically decreased recovery rates. The analytical method was validated regarding its precision (coefficients of variation: 2.9-7.4%), accuracy (relative recovery rates: 93-105%), robustness (relative recovery rates in individual urine matrices: 92-117%), selectivity, and limit of quantification (1.0 μg L^-1). Fundamental aspects in the analysis of technical product mixtures such as NP, comprising various isomers and homologues, were considered. Validation results, an exposure scenario and the application of the procedure to real samples, show that it enables a rugged monitoring of NP exposures above, at, and significantly below health-based guidance values, corresponding to daily NP intakes in the low μg kg^-1 d^-1 range. On the other hand, background levels in non-specifically exposed populations cannot be detected with this method. Hence, while alternative approaches should be pursued for NP analysis at environmental trace level, the speed and simplicity of our method are ideal for high-throughput human biomonitoring in occupational medicine.

Human Metabolism and Urinary Excretion Kinetics of Nonylphenol in Three Volunteers after a Single Oral Dose

Nonylphenol (NP) is an endocrine-disrupting anthropogenic chemical that is ubiquitous in the environment. Human biomonitoring data and knowledge on internal NP exposure are still sparse, and its human metabolism is largely unknown. Therefore, in this study, we investigated human metabolism and urinary excretion of NP. Three male volunteers received a single oral dose of 1 mg ¹³C₆-labeled NP (10.6-11.7 μg/kg body weight). Consecutive full urine voids were collected for 48 h. A metabolite screening identified nine ring- and/or side chain-oxidized metabolites. We chose the most promising hits, the alkyl chain-oxidized metabolites hydroxy-NP (OH-NP) and oxo-NP, for quantitative investigation next to the parent NP. For this purpose, we newly synthesized specific n - 1-oxidized monoisomeric analytical standards. Quantification of the polyisomeric metabolites was performed via online-solid phase extraction-LC-MS/MS with stable isotope dilution using a previously published consensus method. Alkyl chain hydroxylation (OH-NP) constituted the major metabolism pathway representing 43.7 or 62.2% (depending on the mass transition used for quantification) of the NP dose excreted in urine. The urinary excretion fraction (F_UE) for oxo-NP was 6.0 or 9.3%. The parent NP, quantified via an analogous isomeric ¹³C₆-NP standard, represented 6.6%. All target analytes were excreted predominately as glucuronic acid conjugates. Excretion was rather quick, with concentration maxima in urine 2.3-3.4 h after dosing and biphasic elimination kinetics (elimination half-times first phase: 1.0-1.5 h and second phase: 5.2-6.8 h). Due to its high F_UE and insusceptibility to external contamination (contrary to parent NP), OH-NP represents a robust and sensitive novel exposure biomarker for NP. The novel F_UEs enable to robustly back-calculate the overall NP intakes from urinary metabolite levels in population samples for a well-informed cumulative exposure and risk assessment.

A validated LC-MS/MS method for the quantification of climbazole metabolites in human urine

Climbazole is a preservative and an anti-dandruff ingredient with applications in various cosmetic products. The general population is therefore exposed to this chemical, and exposure monitoring is desirable. We have postulated a pathway for the human metabolism of climbazole, leading to two specific metabolites which can be excreted via urine. An analytical method for the determination of these metabolites in human urine was developed and validated. The sample preparation includes an enzymatic hydrolysis protocol. The measurement as such is based on online solid phase extraction (SPE), coupled to ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Intra- and inter-series coefficients of variation (CV) were determined in the concentration range from 1 µg/l to 100 µg/l with spiked pooled urine samples, and they were consistently below 15%, mostly below 10%. The corresponding accuracies (mean relative recovery rates) in spiked pooled urine varied from 97% to 103%. The robustness of the method was estimated by spiking individual urine samples. At 1 µg/l, the robustness was rather limited due to interfering matrix peaks in several samples, but excellent results were obtained at 10 µg/l and 100 µg/l, with CVs between 7% and 14% and accuracies from 101% to 110%. Matrix interferences often seemed to be associated with higher creatinine contents (≥2.0 g/l) of the samples. We subsequently applied the method to urine specimens from a human metabolism study involving documented climbazole exposures. We were able to identify and quantify the postulated metabolites in those real samples, thus validating our metabolism hypothesis. We also investigated the precision and accuracy of the enzymatic deconjugation with the real samples. The deconjugation step was found to be highly repeatable and largely quantitative. Both metabolites formed glucuronides, though varying fractions were also excreted in unconjugated (free) forms. Phase II conjugates other than glucuronides did not seem to be produced in significant amounts. With our method, both climbazole metabolites can be reliably quantified in the range between about 1.5 µg/l (depending on matrix interferences in individual samples) and at least 500 µg/l.

Metabolites of 4-methylbenzylidene camphor (4-MBC), butylated hydroxytoluene (BHT), and tris(2-ethylhexyl) trimellitate (TOTM) in urine of children and adolescents in Germany - human biomonitoring results of the German Environmental Survey GerES V (2014-2017)

The UV filter 4-methylbenzylidene camphor (4-MBC), used in cosmetics, the antioxidant butylated hydroxytoluene (BHT), used inter alia as a food additive and in cosmetics, and the plasticizer tris(2-ethylhexyl) trimellitate (TOTM), used mainly in medical devices as substitute for di-(2-ethylhexyl) phthalate (DEHP), are suspected to have endocrine disrupting effects. Human biomonitoring methods that allow for assessing the internal exposure of the general population to these substances were recently developed in a German cooperation to enhance the use of human biomonitoring. First-morning void urine samples from 3- to 17-year-old children and adolescents living in Germany were analysed for metabolites of 4-MBC (N = 447), BHT (N = 2091), and TOTM (N = 431) in the population-representative German Environmental Survey on Children and Adolescents 2014-2017 (GerES V). 4-MBC metabolites were found in quantifiable amounts only in single cases and exposure levels remained well below health-based guidance values. In contrast, ubiquitous exposure to BHT became evident with a geometric mean (GM) urinary concentration of the metabolite BHT acid of 2.346 μg/L (1.989 μg/g_creatinine) and a maximum concentration of 248 μg/L (269 μg/g_crea). The highest GM concentration was found in young children aged 3-5 years, yet no specific sources of exposure could be identified. Also, TOTM metabolites were found in quantifiable amounts only in very few samples. None of these findings could be related to previous hospital treatment or exposure via house dust. The presented results will be the basis to derive reference values for exposure of children and adolescents in Germany to BHT and will facilitate to identify changing exposure levels in the general population.

Rapid and sensitive LC-MS-MS determination of 2-mercaptobenzothiazole, a rubber additive, in human urine

2-Mercaptobenzothiazole (MBT) is one of the most important vulcanization accelerators in the industrial production of rubber, especially car tires. Given its wide use in household articles and industrial rubber products it has a high potential to migrate into the environment. Humans can be exposed by dermal, oral, or inhalative routes. Incorporated MBT is excreted in urine, mainly as conjugates to glucuronide, sulfate, and mercapturic acid. On the basis of these facts MBT has been selected as a substance of high interest in the large scale 10-year German project on human biomonitoring (HBM); a cooperation between the German Federal Ministry for the Environment (BMUB) and the German Chemical Industry Association (VCI) with the objective of developing new analytical methods for relevant chemicals. The presented method was developed to determine MBT in human urine to reliably investigate the internal human MBT dose. Total MBT is measured after enzymatic hydrolysis followed by application of high-pressure liquid chromatography tandem mass spectrometry (HPLC-MS-MS) in positive-electrospray-ionization mode (ESI+) using isotope-dilution quantification. High sample throughput could be obtained by use of the column-switching technique. Optimization yielded an analytical method with a low and reproducible limit of detection (LOD) of 0.4 μg L(-1) and a limit of quantification (LOQ) of 1 μg L(-1), and low relative standard deviations in the range 1.6-5.8 %. A small biomonitoring study covering unexposed humans and occupationally exposed workers was performed to establish the feasibility and reliability of the method. MBT was found in only one urine sample from the unexposed humans, at a value of 10.8 μg MBT per liter, whereas it was found in all samples from the tested workers at values of up to 6210 μg MBT per liter.

Inter- and intra-specific gene-density-correlated radial chromosome territory arrangements are conserved in Old World monkeys

Recently it has been shown that the gene-density correlated radial distribution of human 18 and 19 homologous chromosome territories (CTs) is conserved in higher primates in spite of chromosomal rearrangements that occurred during evolution. However, these observations were limited to apes and New World monkey species. In order to provide further evidence for the evolutionary conservation of gene-density-correlated CT arrangements, we extended our previous study to Old World monkeys. They comprise the remaining species group to be analyzed in order to obtain a comprehensive overview of the nuclear topology of human 18 and 19 homologous CTs in higher primates. In the present study we investigated four lymphoblastoid cell lines from three species of Old World monkeys by three-dimensional fluorescence in situ hybridization (3D-FISH): two individuals of Japanese macaque (Macaca fuscata), crab-eating macaque (Macaca fascicularis), and an interspecies hybrid individual between African green monkey (Cercopithecus aethiops) and Patas monkey (Erythrocebus patas). Our data demonstrate that gene-poor human 18 homologous CTs are located preferentially close to the nuclear periphery, whereas gene-dense human 19 homologous CTs are oriented towards the nuclear center in all cell lines analyzed. The gene-density-correlated positioning of human 18 and 19 homologous CTs is evolutionarily conserved throughout all major higher primate lineages, despite chromosomal inversions, fusions, fissions or reciprocal translocations that occurred in the course of evolution in these species. This remarkable preservation of a gene-density-correlated chromatin arrangement gives further support for a functionally relevant higher-order chromatin architecture.

[Spiegeli's hernia]

Spontaneous lateral ventral hernia (spigelian hernia) is briefly reviewed in the light of 7 patients with a total of 8 hernias. The relatively high incidence of spigelian hernia (5% of all abdominal hernias operated on in 1 year) suggests that this hernia type is not uncommon if borne in mind when diagnosing conditions with abdominal pain. Pain, tenderness and a palpable mass along the lateral edge of the rectus abdominis are the leading symptoms. Since the operation is simple and the postoperative period uneventful, operative treatment is strongly recommended. Accurate diagnosis with resultant surgery for this type of hernia spares the patient unnecessary examinations and totally relieves symptoms.

[Radiogenic sarcoma of the thyroid (author's transl)]

A sarcoma in the region of the thyroid, observed 30 years after radiotherapy in a patient with syringomyelia is presented. Even after low dose radiation in childhood and adolescence tumours of the thyroid frequently can be diagnosed. They rarely occur in adults, because apparently of a long latent period. This case is thought not to be a specific thyroid tumour.