Effect of long-term exposure to simazine on brain and muscle acetylcholinesterase activity of common carp (Cyprinus carpio).

Several water-contamination incidents with simazine have occurred in the province of Badajoz (Spain), due to its excessive use for controlling weeds in olive trees and vineyards. Simazine residues were also detected in drinking water, increasing public health concern. However, little is known on the effects that low levels of simazine pose to environment organisms. We investigated if residues of simazine in the natural waters would affect brain and muscle acetylcholinesterase activity in common carps captured in areas in which simazine residues were detected at average levels of 4.5 microg/L. Results confirmed depression on brain and muscle acetylcholinesterase activity of 20% and 29%, respectively, in carps inhabiting one of the simazine-contaminated ponds, termed "Molinos de Matachel." To assess the biological significance of this finding, we developed a controlled laboratory study in which carps were exposed to simazine at 45 microg/L (10-fold that of the natural water levels) for 90 days. The results obtained in the field study were not confirmed in our laboratory experiment, since carps did not show evidence or brain or muscle acetylcholinesterase activity depression for the duration of the experiment, and therefore, we can conclude that acetylcholinesterase depression found in carps collected in "Molinos de Matachel" should be ascribed to other compounds or mixtures of xenobiotics.