Quantification and stability assessment of 7,9-di­tert­butyl­1-oxaspiro(4,5)deca-6,9-diene-2,8­dione leaching from cross-linked polyethylene pipes using gas and liquid chromatography.

This study assesses the formation and stability of the water contaminant 7,9-di­tert­butyl­1-oxaspiro(4,5)deca-6,9-diene-2,8­dione ([1]) which repeatedly occurs in the migration waters of cross-linked polyethylene (PE-X) pipes. In aqueous solution [1] is partially transformed to 3-(3,5-di­tert­butyl­1­hydroxy-4-oxo-2,5-cyclohexadien-1-yl)propionic acid ([2]). For a better understanding of the formation of [1] and its transformation into [2] an analytical method was established to allow the analysis of both species separately. Because of thermal instability [2] cannot be detected with GC-MS. Therefore, two methods were validated for a reliable and reproducible quantification: GC-MS for [1] and HPLC-MS/MS for both [1] and [2]. Comparative measurements of migration waters from PE-X pipes using GC-MS and HPLC-MS/MS methods showed that the concentrations of [1] detected with GC-MS corresponds to the sum of [1] and [2] measured with HPLC-MS/MS. In the migration waters [1] was detected in higher concentrations than [2]. The highest concentrations of [1], detected with GC-MS, were > 300 µg/L. The longer the materials are stored without contact with water, the more [1] is measured in the migration waters. Most of the previous values reported in the literature for [1] were based on semi-quantification. Hence, we compared results of the semi-quantitative determination according to EN 15768 with those of a quantitative method with a standard. The results gained with the semi-quantitative method represent less than 50% of the quantified values for the amount leaching from the pipes, which means that the semi-quantification method according to EN 15768 leads to a significant underestimation of [1]. Finally, stability assessment showed that [1] developed an equilibrium with [2] under acidic conditions, whereas it will completely be transferred to [2] at pH 10. At pH 7, it takes more than 50 days for [1] to reach an equilibrium with [2]. However, at increasing the temperature to 60 °C, [1] will be rapidly transformed into [2]. Besides [1] and [2], other currently unknown degradation products are formed. As there is no comprehensive toxicological assessment for both substances available today, our findings underline the need for regulatory consequences.

Identification of disinfection by-products (DBP) in thermal water swimming pools applying non-target screening by LC-/GC-HRMS.

The discovery of new disinfection by-products (DBPs) is still a rarely investigated research area in past studies. In particular, compared to freshwater pools, therapeutic pools with their unique chemical composition have rarely been investigated for novel DBPs. Here we have developed a semi-automated workflow that combines data from target and non-target screening, calculated and measured toxicities into a heat map using hierarchical clustering to assess the pool's overall potential chemical risk. In addition, we used complementary analytical techniques such as positive and negative chemical ionization to demonstrate how novel DBPs can be better identified in future studies. We identified two representatives of the haloketones (pentachloroacetone, and pentabromoacetone) and tribromo furoic acid detected for the first time in swimming pools. Non-target screening combined with target analysis and toxicity assessment may help to define risk-based monitoring strategies in the future, as required by regulatory frameworks for swimming pool operations worldwide.

Screening for 26 per- and polyfluoroalkyl substances (PFAS) in German drinking waters with support of residents.

The occurrence of per- and polyfluoroalkyl substances (PFAS) in water cycles poses a challenge to drinking water quality and safety. In order to counteract the large knowledge gap regarding PFAS in German drinking water, 89 drinking water samples from all over Germany were collected with the help of residents and were analyzed for 26 PFAS by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). The 20 PFAS recently regulated by sum concentration (PFAS∑20), as well as six other PFAS, were quantified by targeted analysis. In all drinking water samples, PFAS∑20 was below the limit of 0.1 µg/L, but the sum concentrations ranged widely from below the limit of quantification up to 80.2 ng/L. The sum concentrations (PFAS∑4) of perfluorohexanesulfonate (PFHxS), perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorononanoate of 20 ng/L were exceeded in two samples. The most frequently detected individual substances were PFOS (in 52% of the samples), perfluorobutanesulfonate (52%), perfluorohexanoate (PFHxA) (44%), perfluoropentanoate (43%) and PFHxS (35%). The highest single concentrations were 23.5 ng/L for PFHxS, 15.3 ng/L for PFOS, and 10.1 ng/L for PFHxA. No regionally elevated concentrations were identified, but some highly urbanized areas showed elevated levels. Concentrations of substitution PFAS, including 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate and 2,2,3-trifluor-3-[1,1,2,2,3,3-hexafluor-3-(trifluormethoxy)propoxy]-propanoate (anion of ADONA), were very low compared to regulated PFAS. The most frequently detected PFAS were examined for co-occurrences, but no definite correlations could be found.

Impact of in vitro digested zinc oxide nanoparticles on intestinal model systems.

BACKGROUND: Zinc oxide nanoparticles (ZnO NP) offer beneficial properties for many applications, especially in the food sector. Consequently, as part of the human food chain, they are taken up orally. The toxicological evaluation of orally ingested ZnO NP is still controversial. In addition, their physicochemical properties can change during digestion, which leads to an altered biological behaviour. Therefore, the aim of our study was to investigate the fate of two different sized ZnO NP (< 50 nm and < 100 nm) during in vitro digestion and their effects on model systems of the intestinal barrier. Differentiated Caco-2 cells were used in mono- and coculture with mucus-producing HT29-MTX cells. The cellular uptake, the impact on the monolayer barrier integrity and cytotoxic effects were investigated after 24 h exposure to 123-614 µM ZnO NP. RESULTS: In vitro digested ZnO NP went through a morphological and chemical transformation with about 70% free zinc ions after the intestinal phase. The cellular zinc content increased dose-dependently up to threefold in the monoculture and fourfold in the coculture after treatment with digested ZnO NP. This led to reactive oxygen species but showed no impact on cellular organelles, the metabolic activity, and the mitochondrial membrane potential. Only very small amounts of zinc (< 0.7%) reached the basolateral area, which is due to the unmodified transepithelial electrical resistance, permeability, and cytoskeletal morphology. CONCLUSIONS: Our results reveal that digested and, therefore, modified ZnO NP interact with cells of an intact intestinal barrier. But this is not associated with serious cell damage.

Effects of Zinc Oxide Nanoparticles on Model Systems of the Intestinal Barrier.

Zinc oxide nanoparticles (ZnO NP) are often used in the food sector, among others, because of their advantageous properties. As part of the human food chain, they are inevitably taken up orally. The debate on the toxicity of orally ingested ZnO NP continues due to incomplete data. Therefore, the aim of our study was to examine the effects of two differently sized ZnO NP (<50 nm and <100 nm primary particle size; 123-614 µmol/L) on two model systems of the intestinal barrier. Differentiated Caco-2 enterocytes were grown on Transwell inserts in monoculture and also in coculture with the mucus-producing goblet cell line HT29-MTX. Although no comprehensive mucus layer was detectable in the coculture, cellular zinc uptake was clearly lower after a 24-h treatment with ZnO NP than in monocultured cells. ZnO NP showed no influence on the permeability, metabolic activity, cytoskeleton and cell nuclei. The transepithelial electrical resistance was significantly increased in the coculture model after treatment with ≥307 µmol/L ZnO NP. Only small zinc amounts (0.07-0.65 µg/mL) reached the basolateral area. Our results reveal that the cells of an intact intestinal barrier interact with ZnO NP but do not suffer serious damage.

The role of dietary factors on blood lead concentration in children and adolescents - Results from the nationally representative German Environmental Survey 2014-2017 (GerES V).

In industrialized nations, human lead exposure has decreased significantly in recent decades. Nevertheless, due to its toxic effects, this heavy metal remains a public health concern with children and adolescents being particularly at risk. In Europe nowadays, oral intake via food and drinking water is the predominant exposure pathway for lead. The objective of the present study was to investigate the association between dietary factors and blood lead (PbB) level of 3- to 17-year-old children and adolescents living in Germany, using data from the fifth German Environmental Health Survey (GerES V) and the Child and Adolescent Health Survey (KiGGS Wave 2). GerES V and KiGGS Wave 2 are two national population-representative studies conducted between 2014 and 2017, including measurement of lead concentrations in blood from 720 children and adolescents aged 3-17 years (mean age = 10.21, SD age = 4.36). Using multiple linear regression, sociodemographic and environmental characteristics as well as dietary factors could be identified as significant exposure determinants of PbB concentrations. Lead intake via domestic tap water was the strongest predictor of elevated PbB levels with 27.6% (p-value< .001) higher concentrations of highest compared to none lead intake via tap water. Other foods which were found to be relevant to PbB levels were meat, fruit, and fruit juice. While meat or fruit consumption were each associated with about 13% (p-value < .05) lower PbB levels, fruit juice drinking was associated with up to 12.2% (p-value = .04) higher PbB levels. In conclusion, results indicate the importance of dietary habits for lead exposure in children and adolescents. To protect vulnerable groups, it is recommended that future research and lead-reducing measures pay more attention to dietary links.

Pool water disinfection by ozone-bromine treatment: Assessing the disinfectant efficacy and the occurrence and in vitro toxicity of brominated disinfection by-products.

Pool water is continuously circulated and reused after an extensive treatment including disinfection by chlorination, ozonation or UV treatment. In Germany, these methods are regulated by DIN standard 19643. Recently, the DIN standard has been extended by a new disinfection method using hypobromous acid as disinfectant formed by introducing ozone into water with naturally or artificially high bromide content during water treatment. In this study, we tested the disinfection efficacy of the ozone-bromine treatment in comparison to hypochlorous acid in a flow-through test rig using the bacterial indicator strains Escherichia coli, Enterococcus faecium, Pseudomonas aeruginosa, and Staphylococcus aureus and the viral indicators phage MS2 and phage PRD1. Furthermore, the formation of disinfection by-products and their potential toxic effects were investigated in eight pool water samples using different disinfection methods including the ozone-bromine treatment. Our results show that the efficacy of hypobromous acid, depending on its concentration and the tested organism, is comparable to that of hypochlorous acid. Hypobromous acid was effective against five of six tested indicator organisms. However, using Pseudomonas aeruginosa and drinking water as test water, both tested disinfectants (0.6 mg L-1 as Cl2 hypobromous acid as well as 0.3 mg L-1 as Cl2 hypochlorous acid) did not achieve a reduction of four log10 levels within 30 s, as required by DIN 19643. The formation of brominated disinfection by-products depends primarily on the bromide concentration of the filling water, with the treatment method having a smaller effect. The eight pool water samples did not show critical values in vitro for acute cytotoxicity or genotoxicity in the applied assays. In real pool water samples, the acute toxicological potential was not higher than for conventional disinfection methods. However, for a final assessment of toxicity, all single substance toxicities of known DBPs present in pool water treated by the ozone-bromine treatment have to be analyzed additionally.

Lead, cadmium, mercury, and chromium in urine and blood of children and adolescents in Germany - Human biomonitoring results of the German Environmental Survey 2014-2017 (GerES V).

Metals reach humans through food and drinking water intake and inhalation of airborne particles and can have detrimental health effects in particular for children. The metals presented here (lead, cadmium, chromium, and mercury) could lead to toxic effects such as neurotoxicity, mutagenicity, and have been classified as (possible) carcinogens. Using population representative data from the German Environmental Survey 2014-2017 (GerES V) from 3- to 17-year-old children on lead and cadmium in blood (n = 720) and on cadmium, chromium, and mercury in urine (n = 2250) we describe current internal exposure levels, and socio-demographic and substance-specific exposure determinants. Average internal exposure (geometric means) in blood was 9.47 µg/L for lead and below 0.06 µg/L (limit of quantification) for cadmium, and in urine 0.072 µg/L for cadmium, 0.067 µg/L for mercury, and 0.393 µg/L for chromium, respectively. Younger children have higher concentrations of lead and chromium compared to 14-17-year-old adolescents, and boys have slightly higher mercury concentrations than girls. With respect to substance specific determinants, higher lead concentrations emerged in participants with domestic fuel and in non-smoking children with smokers in the household, higher levels of cadmium were associated with smoking and vegetarian diet and higher levels of mercury with the consumption of seafood and amalgam teeth fillings. No specific exposure determinants emerged for chromium. The health based guidance value HBM-I was not exceeded for mercury and for cadmium in urine it was exceeded by 0.6% of the study population. None of the exceedances was related to substantial tobacco smoke exposure. Comparisons to previous GerES cycles (GerES II, 1990-1992; GerES IV, 2003-2006) indicate continuously lower levels.

Cellular Uptake and Toxicological Effects of Differently Sized Zinc Oxide Nanoparticles in Intestinal Cells.

Due to their beneficial properties, the use of zinc oxide nanoparticles (ZnO NP) is constantly increasing, especially in consumer-related areas, such as food packaging and food additives, which is leading to an increased oral uptake of ZnO NP. Consequently, the aim of our study was to investigate the cellular uptake of two differently sized ZnO NP (<50 nm and <100 nm; 12-1229 µmol/L) using two human intestinal cell lines (Caco-2 and LT97) and to examine the possible resulting toxic effects. ZnO NP (<50 nm and <100 nm) were internalized by both cell lines and led to intracellular changes. Both ZnO NP caused time- and dose-dependent cytotoxic effects, especially at concentrations of 614 µmol/L and 1229 µmol/L, which was associated with an increased rate of apoptotic and dead cells. ZnO NP < 100 nm altered the cell cycle of LT97 cells but not that of Caco-2 cells. ZnO NP < 50 nm led to the formation of micronuclei in LT97 cells. The Ames test revealed no mutagenicity for both ZnO NP. Our results indicate the potential toxicity of ZnO NP after oral exposure, which should be considered before application.

Tp*Cu(I)-CN-SiL2-NC-Cu(I)Tp*--a hexacoordinate Si-complex as connector for redox active metals via π-conjugated ligands.

Hexacoordinate silicon complexes L2SiX2 (L = a 2-benzoylpyrrol-1-yl derivative, X = CN, NCS) were synthesized from L2SiCl2 by ligand exchange with trimethylsilyl reagents Me3SiX. In the presence of [Tp*CuNCMe] and Me3SiCN the silicon complex L2Si(NC(CuTp*))2 was obtained, which contains a linear Cu-CN-Si-NC-Cu unit (Tp* = hydrotris(3,5-dimethylpyrazolyl)borato).

2-Acylpyrroles as mono-anionic O,N-chelating ligands in silicon coordination chemistry.

Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole (L(1)H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L(1)2SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L(1)2SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L(1)2SiCl2, L(1)2SiF2, L(1)2Si(OTf)2, L(1)2SiPhCl, and L(1)2SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L(1)3Si(+) and L(1) SiPh(+) were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L(1)2SiCl2 with a third equivalent of L(1)H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated C-C coupling of two ligands L(1).