Methylated hexachlorocyclohexane in blue mussels (Mytilus edulis) from the Mersey and Dee Estuaries

Blue mussels (Mytilus edulis) from the Mersey and Dee Estuaries have been found to contain high concentrations of alpha-MHCH (methyl hexachlorocyclohexane) and gamma-MHCH (methyl lindane), and a series of other methylated isomers of MHCH. Mean values for SigmaMHCH in mussels declined serially from Rock Ferry (81.4 +/- 19.3 microg kg(-1)), the innermost site in the Mersey Estuary, to Egremont (49.0 +/- 8.6 microg kg(-1)) and New Brighton (11.1 +/- 3.8 microg kg(-1)); but the value for Crosby (67.0 +/- 10.2 microg kg(-1)) on the Liverpool shoreline was surprisingly high. Concentrations of alpha-HCH and gamma-HCH in M. edulis were consistently low, at <3.0 microg kg(-1). Comparisons between MHCH data for M. edulis and muscle tissue of both dab (Limanda limanda) and plaice (Pleuronectes platessa) give some evidence of food chain biomagnification of MHCH compounds, with adult plaice caught within the Mersey Estuary, where they feed on shellfish, showing very high levels of gamma-MHCH (18 +/- 9 microg kg(-1)) and MHCH (169 +/- 76 microg kg(-1)). Methylated analogues of HCH in biota are of potential regulatory interest and of substantial importance to the environmental management of the Mersey and Dee Estuaries.