They are

usually synthesized in a measure that is the predicted no-effect concentration, shortened as PNUC.

that basically say that these thresholds are the toxicity thresholds for some aquatic species.

However, translating this threshold into the understanding of what is actually happening in the real aquatic environment is not very easy.

One major challenge is the data availability, because to assess the risk, we need to know how concentration of medicine in surface water change over time and over space.

And for doing this, we need environmental monitoring So someone that samples the water and says, oh, there is this concentration of this medicine.

However, the problem here is that this environmental monitoring of liver and legs is often limited by the feasibility and the cost because it's pretty expensive to do a lot of monitoring and results in few locations monitored and also not so frequently and also the number of substances to be limited.

So which other solutions would have the most impact on reducing environmental exposure to medicines?