Ecotoxicological risk assessment of chemical pollution in four Iberian river basins (Llobregat, Ebro, Júcar and
Guadalquivir) was performed. The data set included more than 200 emerging and priority compounds measured
at 77 sampling sites along four river basins studied. The toxic units (TU) approach was used to assess the risk of
individual compounds and the concentration addition model (CA) to assess the site specific risk. Link between
chemical pollution and aquatic macroinvertebrate communities in situ was examined by using four biological
indexes; SPEAR (“Species at Risk Index”) as the indicator of decline of sensitive species in relation to general
organic (SPEARorganic) and pesticides (SPEARpesticides) pollution; and Shannon and Margalef biodiversity indexes.
The results of the study suggested that organic chemicals posed the risk of acute effects at 42% of the sampling
sites and the risk of chronic effects at all the sites. Metals posed the acute risk at 44% of the sites. The main drivers
of the risk were mainly pesticides and metals. However, several emerging contaminants (e.g. the antidepressant
drug sertraline and the disinfectant triclosan) were contributing to the chronic effects risk. When risk associated