The quality of bathing water is essential for the protection of the health of citizens and plays an important role also in terms of the protection of the natural environment and the economic aspects in the tourism sector. For this reason, specific monitoring is carried out throughout the bathing season. With regard to the bathing season 2024, more than 31,600 samples of seawater and lake were collected and analyzed on a total of over 5,000 km of bathing coast. At municipal level the km of coast are divided into more or less extensive bathing waters, for a total of 5,506 bathing waters. The results of the analysis, in addition to guaranteeing the absence of hygienic health risks during the season, have also allowed to classify the waters. The classification was made using the results of the monitoring carried out during the 2024 bathing season and those of the previous three seasons (2023-2022-2021). At the national level, most of the waters are excellent in the classroom (91%), however, however, there are still critical issues due to the presence of water in the low class (1.1%) and not classifiable (1.1%), for which it is not possible to make a quality judgment because most are newly identified and have not completed the 4-year cycle of monitoring, necessary for classification. Even at the regional level, the percentage of water in the excellent and good classes is the highest.

Ostreopsis cf. ovata is a potentially toxic benthic benthic microalgae, currently present in most Italian coastal regions with blooms that can give rise to phenomena of human intoxication and toxic effects on benthic marine organisms (states of suffering or mortality). The continuous expansion along the Italian coasts of Ostreopsis cf. ovata, its blooms and the health, environmental and economic problems associated with it, has led to the establishment of a microalga surveillance monitoring program since 2007. This activity is carried out annually in the summer season by the Regional Agencies for the Environment (ARPA). The data provided so far by ARPA, collected and processed by ISPRA have clarified the distribution and trend of blooms at national and regional level. To date, microalgae has been found at least once in the monitoring campaigns carried out so far in 12 of 15 coastal regions. In 2024, Ostreopsis cf. ovata is present in 11 coastal regions or in 135/196 stations (68.9%), while it is absent in all the samples taken along the coasts of Emilia-Romagna, Marche, Molise and Veneto.