To the Editor: Roughly half the toxic PCB's in the New York Harbor have chemical "fingerprints" tracing them to General Electric's factories 200 miles upriver.

A year ago, G. E. scientists reported that some bacteria found in PCB sediments attacked and released chlorine atoms from PCB's, thus rendering the PCB's less toxic.

A manufacturer of outboard motors has agreed to pay for a $20 million cleanup of toxic PCB's in Lake Michigan's Waukegan Harbor, ending years of bitter dispute over the problem.

A Houston-based gas pipeline company today released the names of 51 sites in 12 states where it has acknowledged burying toxic PCB's.

The overnight acquisition of Honeywell, a $45 billion company, stands in stark contrast to the 20-year battle to remove the million pounds of toxic PCB's that G.E. dumped into the Hudson River.

The Department of Health is considering whether to investigate an elevated rate of respiratory diseases among people who live near hazardous-waste sites containing toxic PCB's and pesticides, a department spokeswoman said yesterday.

For the dwindling number of commercial fishermen on the river, the fish, although plentiful, are a mixed catch - a legacy of a 16-year-old controversy about toxic PCB's in the river.

That is why high levels of toxic PCB's found in the stream and their unlikely source have sent a ripple of shock through this central Montana town of 4,000.

The Environmental Protection Agency disclosed today that it had found high levels of toxic PCB's in wells for drinking water near a pipeline company dump near Lambertville, N.J.

An industrial accident in Taiwan nine years ago that spilled high levels of toxic PCB's into cooking oil has caused an epidemic of birth defects, a new study has found.