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Sand quality as the new criterion of the new Blue Flag recreational water sites in Portugal - It's happening!
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Introduction: The new WHO guidelines for the quality of bathing waters were published in June 2021, and the chapter on sands was significantly revised compared to the 2003 guidelines. They recommend monitoring enterococci with a provisional limit of 60 MPN/g and a guide value for the total fungal count of 90 CFU/g. The 60 MPN/g sand value was calculated through microbiological risk assessment as equivalent to the reference of 200 MPN/100ml of water, which corresponds to a maximum risk of 5% of developing disease from direct exposure.
Based on these guidelines, Portugal’s Blue Flag program decided to implement a new quality criterion for bathing areas in 2024, called “Sand Quality Monitoring.” This criterion was tested for two years without being mandatory, and it was concluded that it would be a good addition to the list of criteria and would not pose a management issue for the beaches. On the contrary, it provides an additional and independent microbiological safety criterion for recreational users, separate from the monitoring of recreational water quality.
To implement the new criterion, limits had to be designed for total fungi and E. coli, as the current European directive includes E. coli, and the guidelines for total fungi only provide a guide value, no safety limits. For fungi, the following was defined: 20% of rejection rate, considering the results of Brandão et al. (2021). This represent a guidance value of 89 CFU/g of total fungi in sand but a rejection limit of the 80% percentile, which is 420 CFU/g for coastal beaches and 1130 CFU/g for inland beaches. E. coli serves as an extra faecal indicator, with a reference value of 25 CFU/g (Sabino et al. 2011).
Methods: Analytical methods are based on colony counting on sabouraud plates for all Fungi (Sabino et al. (2011)), Quanti-Tray® systems from IDEXXTM (IDEXX, Westbrook, MN, USA) or standard ISO methods (ISO 7899-2 (Boehm et al. 2009) and ISO 9308-1) for enterococci and E. coli and BACTERISK® (MolEndoTech, LTD, Brixham, UK) for the latter.
Results (provisional): -Inland and transitional beaches (>1130 CFU/g): 14 out of 43 (32.6%); -Coastal beaches (>420 CFU/g): 17 out of 292 (5.8%)
Discussion and conclusions: There is still not enough data to analyse seasonality and regionality comparatively, but…There doesn't seem to be a visible rationale for changes during the bathing season — too many factors influence sand quality and there’s little historical data. Maybe in the future. The values for fecal parameters in Mirandela are low and compliant, but…Total fungi values in Mirandela exceed the 2024 criteria: Homem do Leme, Gondarém and Mamoa exceeded the limits for enterococci contamination more than once; Beaches exceeding fungal limits more than once: Inland beaches: Mirandela, Fraga da Pegada, Ribeira, and Praia fluvial de Reguengos de Monsaraz; Coastal beaches: Homem do Leme, Foz, and Quebrada;
Impact: This study shows that it is possible to include sand in the health protection aspects of recreational water quality without loss of the number of safe recreational sites.
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Sand Quality Blue Flag Fungi Bacterias Agentes Microbianos e Ambiente Portugal