Mirex: an unrecognized contaminant of fishes from Lake Ontario.

A perchlorinated, cage-structured hydrocarbon, C(10)C(l2), also known as mirex or Dechlorane, has been identified in fish samples from the Bay of Quinte, Lake Ontario, Canada. The compound coelutes with polychlorinated biphenyls (PCB's) in residue cleanup procedures and under standard gas chromatographic conditions. Mirex has never been registered for use as an insecticide in Canada, nor does it appear to be in use in any area of the United States discharging water into Lake Ontario or its tributaries. It seems likely, therefore, that this compound is another widespread environmental contaminant of extremely high geochemical stability and as yet only superficially investigated biological activities. Under standard gas chromatographic conditions its peak is superimposed on that of the PCB's, and, as a result, the presence of mirex may have been unrecognized and it may therefore have been misinterpreted as a PCB isomer.