Sediment cores measured for containment levels have the highest levels of PCB's from the early 1960's. True or false

Question

I think this is true? right? Help

Yes, it is true in most cases. An examp-le is shown at
http://pubs.usgs.gov/circ/circ1171/html/cores.htm

The reason is that PCB bans and restrictions on disposal began to take effect in the late 1960's.