PCB hot spots found in estuaries

The results were published in a report on the latest findings of the Ministry of Agriculture, Fisheries and Food's programme of marine pollution monitoring.¹Some 120 samples of surface sediments were taken during a cruise around the English and Welsh coasts in 1990.

In most offshore samples, PCBs were not found above the detection limit of 0.2µg/kg. Slight contamination, up to 20µg/kg, was found in the Humber, Tees, Tweed and Ribble estuaries, and around a sewage sludge dumping site off the Mersey estuary.

Higher PCB levels of 20-100µg/kg were detected in the Tyne, Wear and Mersey estuaries. The highest level of 109µg/kg was found in the middle Tyne estuary and would be classed as "heavily contaminated" under a proposed system of classifying PCB levels in sediments.

The most extensive area of contamination discovered was off Rame Head, near Plymouth Sound. The area is a dump site which receives about 200,000 tonnes of dredgings from Plymouth Sound annually. Thirteen samples taken across a wide area had PCB levels of up to 72µg/kg.

All of the highest levels of contamination are apparently associated with dockyards and may have resulted from the use of PCBs in transformers and as flame retardants in oils and other materials. The lower levels of contamination appear to be associated with industrial and sewage sludge sources.