The concentrations of substances introduced into river systems by humans have been measured by 87 research groups worldwide in a concerted effort. In the journal “PNAS” they show that at every fourth measurement point, at least one value of residues of pharmaceuticals, cosmetics or lifestyle substances such as nicotine or caffeine was increased to an extent that could threaten aquatic organisms or promote antibiotic resistance. This also applies to the Danube near Vienna.
Samples were collected from 137 regions around the world. In total, the scientists gathered information from 1,052 locations. All samples were evaluated in a single laboratory at the University of York (Great Britain) in order to achieve the best possible comparability. A search was made for 61 substances from the pharmaceutical and lifestyle sectors. According to the environmental geoscientist Thilo Hofmann from the University of Vienna, who was involved in the study, this is the first comprehensive study that deals with the substance cocktail that humans put into rivers.
The 61 substances now being examined are those that scientists have identified as important influencing factors in earlier studies. From a global perspective, the epilepsy drug carbamazepine was found most frequently in the new study, followed by the diabetes drug metformin and third place was taken by caffeine, a compound that reflects lifestyle, but is also used in medicines. Also at the top of the list are the narcotics lidocaine or nicotine and paracetamol, as can be seen from the work.
Vienna in 40th place
The highest levels of contamination were found in Lahore (Pakistan), La Paz (Bolivia), Addis Ababa (Ethiopia) and in India
Delhi. In the Vienna area, Hofmann and his team took samples from a total of seven points before, in and at certain intervals after the city and after Vienna’s main sewage treatment plant. On average, the values in the federal capital are higher than in other EU countries and in other cities bordering the Danube, such as Bratislava, Budapest, Belgrade and Bucharest. Madrid achieved the highest average values in the EU (twelfth place worldwide). The Vienna section of the Danube ranked 40th among the 137 regions surveyed.
Hofmann emphasized that this finding should not be taken in an alarmist manner. However, the sometimes “surprisingly high concentrations” show where the weaknesses lie. In Vienna, for example, the carbamazepine and metformin levels were relatively high. “Of course we also find a lot of caffeine.” In addition, there were several antibiotics, allergy medicines, antihypertensive drugs and active substances against nervous disorders.
Concentrations that could have an impact on organisms are also recorded immediately after the discharge of city sewage into the Danube, but this disappears again a few kilometers downstream.
In any case, the study clearly shows that the rivers are a mirror of human activity. The findings are a strong argument in favor of establishing a fourth cleaning stage in sewage treatment plants in Europe so that “no more medication or cosmetic residues are discharged into water”. Vienna is in a good position to be able to wash these remnants down the Danube, so to speak, with the high-quality fresh water from the high springs, where it is quickly diluted. “But that can’t be the long-term solution, we’ll need a fourth purification stage so that we can get these substances out,” says the environmental geoscientist.
“10 to 15 years left”
Which effects the substance cocktail can actually develop in the rivers is also being investigated in Vienna as part of the recently launched “Exposome Austria research infrastructure”. What individual substances could do is widely understood. However, the interplay of the materials could also hold surprises, explained Hofmann. In order to really understand the “chemical cloud”, however, science will probably “need around 10 to 15 years”.