This report provides the first large-scale estimate of road salt contribution to freshwater salinization in Nordic countries and its ecological consequences. In Sweden, road salt alone may account for up to 11% of freshwater salinization, while nearly 40% of variation is jointly explained by salt and other human pressures. Analyses of least-impacted sites revealed biological responses at very low salinity levels: even modest road salt concentrations significantly increased conductivity and ion concentrations. Biodiversity declines were substantial, with strong decreases of biomonitoring indices and Ephemeroptera and Plecoptera richness at highly exposed sites. These community responses occurred at salinity far below existing thresholds used in other countries, suggesting that current standards are likely too high for naturally low-salinity ecosystems and emphasizes the need to develop standards specific to Nordic countries. The study highlights uncertainties linked to defining reference sites, accounting for confounding pressures. Nonetheless, evidence shows that road salt pollution is a meaningful ecological threat; especially as usage trends vary across countries. Concentrations of road salt currently observed are likely to cause major biodiversity impacts on many sites. Improved monitoring and region-specific salinity thresholds are therefore essential for effective freshwater protection.

CRABOT Julie;  MINGARELLI Sandra;  FOLSTER Jens;  AROVIITA Jukka;  MITIKKA Sari;  FREE Gary;  CANEDO ARGUELLES Miguel; 

2026-07-15

Publications Office of the European Union

JRC146123

978-92-68-41514-6 (online),   

1831-9424 (online),   

EUR 40779,    OP KJ-01-26-294-EN-N (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC146123,   

10.2760/9059606 (online),