Trace Metal and Chlorinated Hydrocarbon Concentrations in Shellfish from Irish Waters 2001

Abstract

Major shellfish growing areas were sampled in accordance with the monitoring requirements of Council Directive 79/923/EEC, on the quality required of shellfish waters, and Council Directive 91/492/EEC, laying down the health conditions for the production and placing on the market of live bivalve molluscs. Data for physicochemical parameters in water, trace metal levels and chlorinated hydrocarbon concentrations in shellfish are presented. In 2001, a total of 23 samples from 20 different shellfish sites were analysed for trace metals and chlorinated hydrocarbons. The median concentration of mercury in shellfish sampled in 2001 was <0.03 mg/kg wet weight, with a maximum of 0.04 mg/kg wet weight which is well within the maximum limit of 0.50 mg/kg wet weight for mercury in bivalve molluscs set by the EU. The levels of lead and cadmium detected were low, with means of 0.20 and 0.24 mg/kg wet weight and maxima of 0.37 and 0.74 mg/kg wet weight respectively, also within the respective maximum levels of 1.50 and 1 mg/kg wet weight set by the EU. There are no internationally agreed standards or guidelines available for the remaining trace metals and chlorinated hydrocarbons in shellfish. However these results were compared with the strictest standard or guidance values for shellfish, which are applied by contracting countries to OSPAR, and were found to be well below the strictest values listed. This is evidence of the clean, unpolluted nature of Irish shellfish and shellfish producing waters. As in previous years, the water quality from shellfish growing areas was good and conformed to the requirements of the Directive. Petroleum hydrocarbons were not visible in any of the shellfish waters or as deposits on the shellfish. This survey confirms previous studies (Glynn et al., 2003; McGovern et al., 2001; Bloxham et al., 1998; Smyth et al., 1997 and Nixon et al., 1995, 1994, and 1991), which show that contamination from trace metals and chlorinated hydrocarbons is low in Irish shellfish aquaculture.