The installation in Río Negro of the first pulp mill UPM generated a diplomatic conflict between Uruguay and Argentina which even led to the bridges were cut during much of Tabaré Vázquez’s first administration.
The dispute ended in 2010 in The Hague with the obligation to carry out joint monitoring of activitieswhose results must be made public although the Administrative Commission of the Uruguay River (CARU) usually analyzes and discloses them with a delay.
In February, the CARU unveiled a report which showed that in the first ten years of monitoring was greater non-compliance at the mouth of Gualeguaychú (505) than at the UPM plant in Fray Bentos (12).
Although they generated various interpretations, the data were not questioned by the countries’ technicians, something that It did happen recently when analyzing the 2023 reports from the UPM plantaccording to documents reviewed by The Observer.
That year, which represents the last report available since the 2024 report is being analyzed, 12 entrances to the plant –the monitoring program is monthly– and is They surveyed 117 parameters, of which 55 are regulated and 62 are not included in applicable regulations.
The report indicates that the regulated values were “below the permitted value” except in the phosphorus measurement that was recorded in April.
The document says that Nor were any non-compliance observed with respect to the “load values and specific load per unit of production in the annual average for the year 2023.”
The differences
However, beyond these analyzes and in a complementary manner, toxicity tests in Microtox and Daphnia magna.
The Daphnia magna It is a small organism known as a water flea that is often used as an environmental bioindicator. The results of their analyzes were those generated the difference in interpretations.
The Argentines Emilio Menvielle and Alejandra Rodríguez and the Uruguayan Cristhian Clavija They interpreted that In November and December, UPM effluents caused toxicity to the Daphnia magna, while Eugenio Lorenzo – the other Uruguayan – concluded that No “regulatory non-compliance” was observed.
The controversy is in the interpretation of the Uruguay River digest, which establishes that for a liquid to be officially considered “acutely toxic”must have a lethal dose so high that it causes the death of 50% or more of the organisms tested.
When evaluating exclusively the 100% pure (undiluted) effluent sample, the maximum mortality levels were 46.6% (November) and 40% (December)leading Lorenzo to maintain that there is no “acute toxicity.”
However, as the laboratory noted that in None of the dilutions tested had a mortality of 0%which indicated that there was a component in the sample that affected the survival of the organisms, the others three scientists suggested that there was toxicity. “Levels of immobilization/mortality are reached statistically significant compared to the negative control in this sample (so) it is considered that the effluent caused toxicity on Daphnia magna ”says the report.
To argue this position, the specialists highlighted that in the diluted samples the results were variable; for example, in December when diluting the 80%, 70% and 60% mortality was 63%, 60% and 60% respectively. In his opinion, these levels are “statistically significant with respect to the negative control samples.”
As he knew The Observer, The technicians analyze the samples from the first months of 2024 to determine if it was a one-time incident or episodes of widespread toxicity.
