Suchergebnisse

AbstractBackgroundPtaquiloside (PTA) is a natural carcinogen found in bracken ferns. PTA is released from the plants via soil to surface and groundwaters from where humans can be exposed via drinking water. Primary degradation of PTA is due to hydrolysis with formation of pterosin B (PTB). Temperature and pH determine the rate of hydrolysis under pure experimental conditions. To assess the applicability of the experimental model to natural groundwaters, PTA degradation kinetics were examined in a range of natural groundwaters at environmentally relevant conditions.ResultsPTA was quantified by UPLC-MS/MS. Over an 80-day study period, PTA half-lives ranged from 6.5 to 47 days (natural pH; 8.0 °C). The fastest degradation was observed for the most alkaline groundwaters with pH of around 8. Rates of degradation were well predicted using an existing mathematical model for hydrolysis. However, deviations from this model were found, especially at the extremes of the examined pH-range (4.7–8.2). The degree of conversion of PTA to PTB was close to unity around neutral pH. However, at slightly acidic conditions, formation of PTB could only count for 9% of the degraded PTA, indicating formation of other products.ConclusionsDegradation of PTA in groundwater is determined by pH and temperature, and PTA can prevail for months under slightly acid to neutral pH conditions. The existing laboratory-based model for PTA hydrolysis is generally applicable for groundwaters but needs further validation at high and low pH.

Abstract
Background
Bracken fern (Pteridium aquilinum) produces several toxic glycosides, of which ptaquiloside (PTA) is the most well documented. PTA is released from bracken to soil and leaches to surface water and to groundwater. This study presents the first comprehensive monitoring study of bracken biomass, PTA content in the biomass, release by precipitation and concentrations in soil solution at 50 cm depth. Laboratory experiments were carried out to estimate the degradation kinetics of PTA in different soil horizons and moisture contents.

Results
The PTA concentration in bracken was highest at the earliest development stages of the plant, i.e., May, declining through the growing season until negligible contents at senescence. The maximum seasonal PTA content in the canopy peaked in early summer, with values up to 1600 mg m−2. Results show that on average 0.2% of the PTA present in the canopy is washed per mm of incident rain, resulting in up to 13.1 mg PTA m−2 being washed off during single rain events. Once in the soil, PTA dissipates rapidly showing a half-lives ranging from 3.3 to 73 h with observed degradation rates showing a tenfold decrease with soil depths increasing from top soil to 25 cm soil depth. Concentrations of PTA in soil solution were positively correlated with the content of PTA in the canopy, with maximum pore water concentrations up to 4,820 ng L−1 during a pulse event taking place in July 2019.

Conclusions
The production of PTA in bracken was found to be proportional to biomass growth, while the mass of PTA being released is a function of volume and intensity of precipitation, as well as the bracken development stage. Leaching of PTA takes place in the form of pulses linked to precipitation events, with concentrations in the soil solution exceeding levels which are known to pose a risk to human health.

Abstract
Background
Ptaquiloside (PTA), caudatoside (CAU) and ptesculentoside (PTE) are carcinogenic illudane glycosides found in bracken ferns (Pteridium spp.) world-wide. The environmentally mobile PTA entails both acute and chronic toxicity. A comparable risk might be associated with the structurally similar CAU and PTE. It is of great health concern if these compounds are present in drinking water, however, it is currently unknown if these compounds can detected in wells in bracken-dominated regions. This study investigates the presence of PTA, CAU, PTE, and their corresponding hydrolysis products pterosins B (PtB), A (PtA) and G (PtG) in water wells in Denmark, Sweden and Spain. Water samples from a total of 77 deep groundwater wells (40–100 m) and shallow water wells (8–40 m) were collected and preserved in the field, pre-concentrated in the laboratory and analysed by liquid chromatography–mass spectrometry (LC–MS).

Results
Deep groundwater wells contained neither illudane glycosides nor their pterosins. However, seven private shallow wells contained at least one of the illudane glycosides and/or pterosins at concentrations up to 0.27 µg L−1 (PTA), 0.75 µg L−1 (CAU), 0.05 µg L−1 (PtB), 0.03 µg L−1 (PtA) and 0.28 µg L−1 (PtG). This is the first finding of illudane glycosides and pterosins in drinking water wells.

Conclusions
Detected concentrations of illudane glycosides in some of investigated wells exceeded the suggested maximum tolerable concentrations of PTA, although they were used for drinking water purpose. Contaminated wells were shallow with neutral pH and lower electric conductivity compared to deep groundwater wells with no illudane glycosides nor pterosins.

On February 12, 2010, SUERF, the Oesterreichische Nationalbank and the Bankwissenschaftliche Gesellschaft continued their established tradition of jointly organised conferences. As evidenced also by the 115 conference participants, this year's subject of "Contagion and Spillovers – New Insights from the Crisis" turned out to be particularly topical, as first lessons from the financial crisis and global recession were being drawn, while concerns about Greece's government debt problems were threatening to spread to other countries within the euro area, with potential negative repercussions for the euro area as a whole being feared by observers.

Background: The COVID-19 pandemic has disrupted routine hospital services globally. This study estimated the total number of adult elective operations that would be cancelled worldwide during the 12 weeks of peak disruption due to COVID-19. Methods: A global expert response study was conducted to elicit projections for the proportion of elective surgery that would be cancelled or postponed during the 12 weeks of peak disruption. A Bayesian β-regression model was used to estimate 12-week cancellation rates for 190 countries. Elective surgical case-mix data, stratified by specialty and indication (surgery for cancer versus benign disease), were determined. This case mix was applied to country-level surgical volumes. The 12-week cancellation rates were then applied to these figures to calculate the total number of cancelled operations. Results: The best estimate was that 28 404 603 operations would be cancelled or postponed during the peak 12 weeks of disruption due to COVID-19 (2 367 050 operations per week). Most would be operations for benign disease (90·2 per cent, 25 638 922 of 28 404 603). The overall 12-week cancellation rate would be 72·3 per cent. Globally, 81·7 per cent of operations for benign conditions (25 638 922 of 31 378 062), 37·7 per cent of cancer operations (2 324 070 of 6 162 311) and 25·4 per cent of elective caesarean sections (441 611 of 1 735 483) would be cancelled or postponed. If countries increased their normal surgical volume by 20 per cent after the pandemic, it would take a median of 45 weeks to clear the backlog of operations resulting from COVID-19 disruption. Conclusion: A very large number of operations will be cancelled or postponed owing to disruption caused by COVID-19. Governments should mitigate against this major burden on patients by developing recovery plans and implementing strategies to restore surgical activity safely.