Analysis and fate of insect repellents.

During summer months the insect repellent N,N-diethyl-m-toluamide (DEET) could always be detected in influents and effluents of wastewater treatment plants (WWTP) and anthropogenically influenced surface waters. In Germany the concentrations have decreased constantly since 1999, when DEET was substituted by Bayrepel. DEET can be degraded in WWTP, but only after an adaptation period and values in the influent above the threshold value. Since the year 2000 Bayrepel could also be detected during the summer months in the influents of WWTP, whereas in the effluents Bayrepel was not present.