Climate Change-Related Temperature Impact on Human Health Risks of Species in Bathing and Surface Water.

species are part of the indigenous microbial flora in marine, brackish and fresh water in moderate and tropical climates that thrive and multiply in water at elevated water temperatures. The number of human non-cholera infections due to exposure to contaminated surface water increases worldwide. To study possible climate change-related changes in concentrations, prevalent species, and risks of illness, water samples from coastal and inland water bodies in the Netherlands were tested in 2019-2021. Data were combined with data from previous studies in 2009-2012 in order to develop a regression model to predict current and future risks of illness. Year-to-year and site-specific variations in concentrations and water temperature were observed, but there was no trend of increasing concentrations or water temperature over time. In 2019-2021, species distribution had not changed since 2009-2012; and were still the dominant species. Statistical analysis demonstrated a significant effect of water temperature on concentrations. The model predicted a concentration increase of a factor of 1.5 for each degree Celsius temperature increase. Predicted risks of illness were higher at higher water temperatures, and higher for children than for adults. Based on the most recent climate change scenarios for the Netherlands, the risks of illness will increase with factors ranging from 1.6 to 7.6 in 2050 and 2100. These outcomes warrant adequate information about risks to water managers, public health workers and the general public.