levels of seven heavy metal residues , arsenic , cadmium , chromium , copper , lead , mercury and zinc were monitored in samples of the american oyster ( crassostrea virginica ) , the soft shell clam ( mya arenaria ) , the hard shell clam ( mercinaria mercinaria ) and the blue crab ( callinectes sapidus ) .
C0347988
heavy metal
C0043481
zinc