Keywords: toxicity stream pyrethroids Systems: stream Substances: Tetramethrin (CXBMCYHAMVGWJQ-UHFFFAOYSA-N) Acrinathrin (YLFSVIMMRPNPFK-WEQBUNFVSA-N) Empenthrin (YUGWDVYLFSETPE-JLHYYAGUSA-N) Cypermethrin (KAATUXNTWXVJKI-UHFFFAOYSA-N)