Bisphenols and Oxidative Stress Biomarkers—Associations Found in Human Studies, Evaluation of Methods Used, and Strengths and Weaknesses of the Biomarkers

Bisphenols, particularly bisphenol A (4,4′-(hexafluoroisopropylidene)-diphenol) (BPA), are suspected of inducing oxidative stress in humans, which may be associated with adverse health outcomes. We investigated the associations between exposure to bisphenols and biomarkers of oxidative stress in human studies over the last 12 years (2008‒2019) related to six health endpoints and evaluated their suitability as effect biomarkers. PubMed database searches identified 27 relevant articles that were used for data extraction. In all studies, BPA exposure was reported, whereas some studies also reported other bisphenols. More than a dozen different biomarkers were measured. The most frequently measured biomarkers were 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-OHdG), 8-iso-prostaglandin F2α (8-isoprostane) and malondialdehyde (MDA), which almost always were positively associated with BPA. Methodological issues were reported for MDA, mainly the need to handle samples with caution to avoid artefact formation and its measurements using a chromatographic step to distinguish it from similar aldehydes, making some of the MDA results less reliable. Urinary 8-OHdG and 8-isoprostane can be considered the most reliable biomarkers of oxidative stress associated with BPA exposure. Although none of the biomarkers are considered BPA- or organ-specific, the biomarkers can be assessed repeatedly and non-invasively in urine and could help to understand causal relationships.

Volatile organic compounds in barite-hosted fluid inclusions from the 3.5 Ga old Dresser Formation, Western Australia

<p>The c. 3.5 Ga Dresser Formation of the East Pilbara Craton (Western Australia) contains large amounts of blackish barite. These rocks produce an intense sulfidic odor when crushed, resulting from abundant primary fluid inclusions. In part, the black barites are interbedded with sulfidic stromatolites. Using Raman spectroscopy, microthermometry, and two different online GC–MS approaches, we characterized in detail the chemical composition of the barite-hosted fluid inclusions. Our GC–MS techniques were based on (i) thermodecrepitation at 150-250°C and (ii) solid phase microextraction (SPME)–GC–MS at reduced temperature (50°C), thereby minimizing external contamination and artefact formation. Major fluid inclusion classes yielded mainly H<sub>2</sub>O, CO<sub>2</sub>, and H<sub>2</sub>S in varying abundance, along with minor amounts of COS and  CS<sub>2</sub>, N<sub>2</sub>, and CH<sub>4</sub> (< 1%). Notably, we also detected a wide range of volatile organic compounds, including short–chain ketones and aldehydes, thiophenes, and various organic (poly)sulfides. Some of these compounds (CH<sub>3</sub>SH, acetic acid) have previously been invoked as initials agents for carbon fixation under primordial conditions, but up to now their presence had not been observed in Precambrian materials. Based on our findings, we hypothesize that hydrothermal seepage of organic and inorganic compounds during Dresser times provided both, catabolic and anabolic substrates for early microbial metabolisms.</p>

The Application of Chemical Polishing in TEM Sample Preparation of Zirconium Alloys

Hydride artefacts are commonly induced by the TEM sample preparation process in Zirconium alloys as hydrogen-sensitive metals, including electron polishing and focused ion beam (FIB) technology. In the research, we present the application of chemical polishing with a solution of 10HF:45HNO3:45H2O to prepare the disk samples for TEM observation in zirconium alloys. The thinning efficiency of chemical polishing is 25 μm per minute. XRD patterns indicate that the chemical polishing actually eliminates the macro- and micro-stress induced by mechanical grinding. TEM observation demonstrates that chemical polishing reduces the amount of hydride artefacts, especially hydrides with large size. It is proposed that induced stress provides driving force for hydride artefact formation. Compared with traditional mechanical grinding, the advantages of chemical polishing are high efficiency, free of induced stress, less induced hydride artefacts and bend contours.

In-Depth Investigation into the Transient Humidity Response at the Body-Seat Interface on Initial Contact Using a Dual Temperature and Humidity Sensor

Relative humidity (RH) at the body-seat interface is considered an important factor in both sitting comfort and generation of health concerns such as skin lesions. Technical difficulties appear to have limited research aimed at the detailed and simultaneous exploration of RH and temperature changes at the body-seat interface; using RH sensors without the capability to record temperature where RH is recorded. To explore the causes of a spike in RH consistently produced on first contact between body and seat surface, we report data from the first use of dual temperature and RH (HTU21D) sensors in this interface. Following evaluation of sensor performance, the effect of local thermal changes on RH was investigated. The expected strong negative correlation between temperature and RH (R2 = −0.94) supported the importance of considering both parameters when studying impact of sitting on skin health. The influence of sensor movement speed (higher velocity approach: 0.32 cm/s ± 0.01 cm/s; lower velocity approach: 0.17 cm/s ± 0.01 cm/s) into a static RH region associated with a higher local temperature were compared with data gathered by altering the rate of a person sitting. In all cases, the faster sitting down (or equivalent) generated larger RH outcomes: e.g., in human sitting 53.7% ± 3.3% RH (left mid-thigh), 56.4% ± 5.1% RH (right mid-thigh) and 53.2% ± 2.7% RH (Coccyx). Differences in size of RH change were seen across the measurement locations used to study the body-seat interface. The initial sitting contact induces a transient RH response (duration ≤ 40 s) that does not accurately reflect the microenvironment at the body-seat interface. It is likely that any movement during sitting would result in similar artefact formation. As a result, caution should be taken when investigating RH performance at any enclosed interface when the surfaces may have different temperatures and movement may occur.