During wastewater treatment, incomplete elimination of micropollutants occurs. These micropollutants represent a potential threat to our health and aquatic environment. The potential impacts of these substances are underestimated due to the lack of available concentrations below the limit of quantifications (LOQ) for an important set of micropollutants. Here, we studied the potential impacts on Human health and aquatic environment of the release of 261 organic micropollutants at the scale of France and we showed that, even with a concentration below the LOQ, some micropollutants could have a significant impact. For the unmeasured concentrations, a global concentration distribution build on several datasets with different LOQ is used. The usual convention of LOQ/2 for the unmeasured concentrations is shown to be an overestimation. Ignoring the unmeasured micropollutants led to an underestimation of the impacts of more than 300% for both human health and aquatic environment. Some substances, such as hydrazine, endrin, or 2,3,7,8-TetraCDD, could lead to a very high impact even with an unmeasured concentration. This work can be adapted to any other compartment and any other geographical context.