Miguel Motas
Professor of Toxicology in the Department of Social and Health Sciences at the University of Murcia
Is the study of good quality?
“The study is of good quality as it develops a novel global model to simulate mercury levels in rivers in the pre-industrial era, thus assessing human disturbances by comparing them with current conditions. By establishing a reference level for mercury in rivers, it reveals rapid responses of mercury in rivers to human disturbances and could be used to inform global mercury restoration targets for rivers. In turn, these concentrations could also be used as indicators to comprehensively understand the effectiveness of mercury pollution governance".
Does it fit with existing evidence?
"It improves the current evidence because, for the first time, it quantifies the global increase in mercury levels in rivers since pre-industrial times, concluding that human activities have raised these levels two to three times higher than today".
Are there any notable limitations?
"Yes, the model results are uncertain due to limitations in the resolution of global datasets and models, which do not allow for a complete understanding of soil erosion processes and their influencing factors, such as small-scale topography and changes in land cover. The model does not consider changes in Hg (mercury) concentration in the soil due to leaching, erosion and atmospheric deposition, which could be an important factor for longer simulation periods".
What are the consequences of this increase for human health?
"The consequences are global and can be considered within the One Health concept, as they affect wetlands and rivers, contaminating the wildlife associated with these ecosystems, as well as other aquatic ecosystems, which ultimately leads to biomagnification in the food chain. All this leads to high levels of mercury exposure in certain geographical areas depending on fish consumption and local pollution of these aquatic ecosystems, which can cause serious health problems, mainly in children and pregnant women".
To what extent is this a problem for Spanish rivers? Which Spanish rivers are most at risk?
"Fortunately, in Spain and the Mediterranean, levels have decreased compared to pre-industrial times".