Many chemicals are undetected in waters

Landau. For many chemicals in water, there are no or only insufficient measured values. A German research team has demonstrated this for the USA and reported on it in the journal "Science." According to the Federal Environment Agency, parts of the study are also applicable to Germany.

For only 0.52 percent of the approximately 297,000 potentially environmentally relevant chemicals in the U.S. Environmental Protection Agency's database, sufficient data on both their occurrence in waterways and their effects are available, writes the five-person team from the Rhineland-Palatinate Technical University of Kaiserslautern-Landau (RPTU). Previously, there was a lack of data on toxicity; today, there is a lack of monitoring data. "The ever-increasing rate at which new chemicals enter the environment poses a challenge for environmental risk assessment."

"Without monitoring the occurrence and distribution of most chemicals, there remains a potential for significant environmental hazards to be overlooked in some cases," the study states. This has historically been the case, for example with the insecticide DDT or, more recently, with the PFAS group of chemicals used in many everyday products. "This demonstrates how the quality of regulatory water monitoring can influence assessments of the risks of chemicals," explains the study's senior author, Ralf Schulz. The researchers only considered the impact on aquatic ecosystems, not on human health.

Some substances are already toxic to aquatic organisms at concentrations that cannot yet be detected, the team writes. This is particularly pronounced with insecticides, especially the group of pyrethroids. They are highly toxic to many insect larvae, but also to fish and other aquatic organisms. Many relevant pyrethroid concentrations remain undetected in regular monitoring programs, the researchers write, referring to the United States.

In Germany, too, there are substances that could be harmful in waters even at concentrations that are not detected or cannot even be detected, said a spokesperson for the Federal Environment Agency. This applies particularly to pyrethroids.

There is clear evidence that agriculturally used pesticides and pharmaceuticals are polluting aquatic ecosystems in Germany, said the UBA spokesperson. This applies particularly to pyrethroids, but also to other active ingredients. "The legal regulations and existing measures to reduce inputs to protect surface waters are therefore insufficient."

Pyrethroids are used not only in agriculture but also as head lice treatments, for wood preservation, and against clothes moths, among other things. They are far less toxic to humans than to insects.

In addition to the few potentially environmentally relevant chemicals for which both monitoring and toxicity data are available, the study reveals that a far larger number exist in the United States without such data. Some of these substances are biologically active even at very low concentrations, including dioxins, endocrine disruptors, PFAS, and pharmaceuticals.

"US water monitoring is considered the most comprehensive program for assessing water quality over large spatial and temporal scales," the researchers write. Other regions, such as the EU, have less comprehensive or no monitoring programs, or no publicly available data. "Today, surface water quality monitoring faces a dual challenge: on the one hand, the sharp increase in the use of chemicals, and on the other, the lack of highly sensitive analytical methods for highly toxic substances in regular testing."

Only recently has a method been developed in Switzerland that is sufficiently sensitive to detect even very low, yet toxic, concentrations of pyrethroids been developed, the UBA spokesperson said. When or to what extent this or a similarly powerful analytical method will be established in the federal states' water monitoring systems remains to be seen, according to the UBA. According to the spokesperson, assessment gaps in the EU approval system for plant protection products also play a key role in the currently inadequate protection of water bodies.

RND/dpa