Organic pollutants contaminate nearly all French rivers and streams, appearing in an average of nine different chemical forms per water sample inside protected ecological areas and 13 outside them, according to a major study published in the journal Water Research.
Environmental scientists Danisa Lione and Jakob Wolfram led a research team at RPTU University Kaiserslautern-Landau examining over 180 million water measurements. Technology Networks reported that the data came from the French long-term monitoring program known as Naïades.
The analysis evaluated a total of 1,731 different chemicals across more than two decades of monitoring records. Researchers compared these concentrations against the known toxicity levels for aquatic organisms in both protected and unprotected flowing waters. The scope of the French data provides us with unprecedented insight into the complexity of chemical pollution and its potential impacts on these ecologically important habitats,
says Jakob Wolfram.
Protected zones successfully reduced the frequency of chemical detections. Yet, concentrations capable of causing direct ecological risks still appeared regularly within those restricted habitats.
Protected areas do significantly reduce the number and frequency of pollutants. Nevertheless, adverse effects continue to occur frequently. Rivers and streams are open systems, so chemicals can also be carried by the current into ecologically valuable refuges, Danisa Lione explained, as quoted by Technology Networks.
Per- and polyfluoroalkyl substances, widely recognized as forever chemicals or PFAS, emerged as the second most frequently detected group of pollutants in the dataset. Phys.org noted that these compounds were identified at roughly 60 percent of the observed sites.
Urban water samples contained an average of six to 11 distinct PFAS compounds annually. Researchers tracked more than 10,000 different PFAS molecules currently in commercial use worldwide.
Aquatic plants suffered the most severe ecological impacts from these chemical exposures. Aquatic invertebrates and fish followed close behind in vulnerability across the monitored water networks.
We still know relatively little about the effects of PFAS on aquatic ecosystems, even though more than 10,000 different PFAS molecules are in use. Their long-term and widespread presence, even in protected areas, is therefore particularly concerning, Danisa Lione stated, as reported by Technology Networks.
Earlier academic studies typically restricted their focus to isolated groups of substances, primarily agricultural pesticides. Expanding the chemical scope to 1,731 total compounds changed risk assessments.
Incorporating these broader organic pollutants increased the estimated environmental risk by 26 percent for fish. For aquatic invertebrates, the calculated ecological risk jumped by 48 percent. The data also highlights how small rivers influenced by agricultural activity remain particularly vulnerable.
Regulatory restrictions on specific problematic pesticides improved conditions for aquatic plants. However, the study recorded no comparable recovery trends for aquatic animals.
Our findings from this large-scale study highlight the far-reaching impacts of organic pollutants, especially pesticides, on aquatic ecosystems. At the same time, they show that risks can be reduced if particularly problematic substances are consistently replaced or phased out, Jakob Wolfram stated, according to Water Research.
While the study clarifies the prevalence of these substances, the full extent of contamination remains partially understood, leaving open the question of how many other undetected chemicals continue to circulate through these open systems.
