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 α-MHCH (methyl hexachlorocyclohexane) and γ-MHCH (methyl lindane), and a series of other methylated isomers of MHCH. Mean values for ΣMHCH in mussels declined serially from Rock Ferry (81.4 ± 19.3 μg kg−1), the innermost site in the Mersey Estuary, to Egremont (49.0 ± 8.6 μg kg−1) and New Brighton (11.1 ± 3.8 μg kg−1); but the value for Crosby (67.0 ± 10.2 μg kg−1) on the Liverpool shoreline was surprisingly high. Concentrations of α-HCH and γ-HCH in M. edulis were consistently low, at <3.0 μg 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 γ-MHCH (18 ± 9 μg kg−1) and MHCH (169 ± 76 μg 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.