Alexander Kämpfe

Circulation of pool water via a treatment plant is critical for maintaining pool water in a condition that is a safe and attractive for bathers. It is also one of the pool operations that is most costly in terms of energy used and associated carbon footprint. In this study, we compare and contrast circulation rate guidelines developed for the UK and for other northern and southern European countries and, where possible, provide an explanation of the underlying rationale. We focus on the management of turbidity-forming material and Cryptosporidium oocysts. We reveal that the parameters used to assess safe operational bathing load are relatively consistent across Europe, based on physical space requirements for bathing and other constraints such as lifeguarding. Circulation rate, on the other hand, is based on either rule-based turnover times, or a more flexible approach based on the volume of water to be treated per bather. The latter offers scope for innovation and energy savings, with the proviso that safe water is maintained for bathers. The guidance in several countries suggests reducing circulation rate when the pool is not being used by bathers. We conclude that a more progressive risk-based approach to pool management, building on these findings, offers significant opportunities for pool operators to run pools better and should be a priority for future research.

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.

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.

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.

Einrichtungen des Badewesen sind Orte zum Wohlfühlen und Entspannen, zur Bewegung, sportlichen Aktivität und vielem mehr, das einen positiven Beitrag zur Gesundheit und zum allgemeinen Befinden leistet. Damit dies so ist und selbstverständlich in Anspruch genommen werden kann, bedarf es einiger Voraussetzungen. Dazu zählen vor allem Maßnahmen, die verhindern, dass das Wasser in Bädern als Infektionsweg dient, auf dem Krankheitserreger von einem Badegast auf andere übertragen werden.