Behind a single MDMA tablet or a few grams of methamphetamine lies a pollution that is still largely unspoken about. Chemical waste, contaminated soil, wastewater... From clandestine production to consumption, synthetic drugs leave an environmental footprint that is beginning to be measured. A new synthesis by the Office français de la drogue et de la toxicomanie (OFDT) documents the contaminations already observed and their effects on wildlife. For human health, however, knowledge remains very incomplete. A single tablet can hide kilograms of waste. The clandestine production of synthetic drugs does not only produce an illicit substance. It also generates significant amounts of chemical waste. According to the OFDT, production can generate 5 to 30 times the volume of the final product in waste. Solvents, acids, precursors, and byproducts can be abandoned in the soil, discharged into sewers, or dispersed into the environment. In these clandestine laboratories, no regulation guarantees their collection or treatment. And once released, certain molecules can persist on surfaces or in natural environments. The problem, however, does not stop at production sites. From toilets to rivers. After consumption, part of the substances are eliminated by the body and enter wastewater. However, wastewater treatment plants are not designed to eliminate all molecules from synthetic drugs. Cathinones and MDMA have thus been detected in surface waters in Spain. Amphetamines and methamphetamine have also been found in rivers in China and on the Tibetan Plateau. At very low concentrations, these molecules may seem insignificant. However, their repeated presence raises another question: that of chronic exposure and their association with other contaminants. Researchers are particularly interested in this "cocktail effect," when several substances are present simultaneously in the environment. The aquatic animals are on the front line. The effects on wildlife are still being studied, but the growing presence of these chemicals in natural environments suggests a potential long-term risk for ecosystems and possibly for human health.