Ecotoxicological relevance of atrazine in aquatic systems

In this report an attempt is made to outline the ecotoxicological role of atrazine in aquatic ecosystems. A brief discussion of the chemistry and metabolism of atrazine is followed by a discussion of the occurrence of this herbicide in the environment. Peak levels for occurrence of atrazine in surface water range from up to 90 μg/L for flowing water to 2 μg/L for standing water. In reality, most values are significantly lower. As with ground water, in which atrazine has also been detected, great caution must be taken when interpreting data on the presence of atrazine in the environment. Atrazine is taken up by nearly all members of the aquatic biocenoses, but in many cases it is also quickly eliminated. The importance of these processes is discussed. The ecotoxicological effects of atrazine on producers, consumers, and decomposers as well as on ecosystem functions first become observable at levels of 20 μg/L or more; the changes are not lasting, even when studied over long periods. Indirect effects are also taken into account in the definition of the threshold value. Deviations from the ecotoxicological threshold value indicated by higher or lower toxi‐cological threshold values in the case of individual organisms are also evaluated. Furthermore, the threshold value is compared with the environmental concern level (EEC) of atrazine. The final assessment is that although atrazine may be potentially hazardous to the environment, the level of hazard depends on the concentration and degree of exposure. It can be assumed that at concentrations of up to 20 μg/L, atrazine does not cause any permanent damage to aquatic ecosystems.