Enormous PCBs increase in oysters from the coast of Guangdong, China

► PCB concentrations (ng g−1 d.w.) ranged from 30 to 2040 with a mean of 315 in 2003-2007. ► Annual PCB levels were 313, 290, 342 ng g−1 d.w., respectively in 2003, 2006, 2007. ► Recent PCB levels have risen by 350-1032 ratios compared with the data in 1989-1991. ► Fortunately, residual PCBs in recent oysters are within 0.004-0.253 mg kg−1 (w.w.). ► Current PCB may derive from older transformers, printing materials and pressworks.