Cadmium content in shellfish from the coast of the South China Sea: the risk to human health

Abstract

In many regions,the marine environment is contaminated with cadmium(Cd),a toxic but widely used industry material.Because shellfish live in the benthos and have a relatively fixed location,their health is largely dependant on the quality of the surrounding environment.A number of researchers have reported finding heavy metals in shellfish samples.Given the importance of shellfish in China,we measured levels of Cd contamination in 5 shellfish species: Crassostrea rivularis,C.gigas,Ruditapes Philippinarum,Perna viridis,and Meretrix meretrix collected from the coast of the South China Sea in 2007 and 2009.We measured the Cd content and evaluated the dietary exposure to Cd from shellfish using the point estimate method.We found significant differ-ences in Cd content among shellfish species.Mean concentrations were 1.80,0.38,0.26,0.15,and 0.12 mg.kg?1 in C.rivularis,C.gigas,P.viridis,M.meretrix,and R.Philippinarum,respectively(range 0.92?2.39 mg.kg?1,0.31?0.46 mg.kg?1,0.21?0.30 mg.kg?1,0.08?0.22 mg.kg?1,and 0.10?0.13 mg.kg?1,respectively).The distribution and seasonal variation in Cd content was correlated with marine environmental factors such as dissolved oxygen,salinity,and temperature.The Cd concentration was higher than the limit for deleterious material by non-environmental pollution of aquatic products in C.rivularis.Conversely,Cd levels were below this limit in the remaining species.In comparison,the levels of Cd were lower than foreign limits for all species.A comparison with survey data collected from other coastal areas in past years suggests the current levels of Cd are within a normal range.Based on our risk assessment,dietary exposure to Cd from consumption of C.rivularis exceeds levels recommended by the Joint Expert Committee on Food Additives(JECFA),suggesting there is a risk to hu-man health.Conversely,the other 4 shellfish species likely pose no risk as the Cd levels were lower than the val-ues recommended by JECFA.The ratio of Cd∶Zn was much lower in C.rivularis than the suggested critical value of 0.015 proposed by some authors as effectively providing protection from Cd induced health impacts.Increased intake of bioavailable zinc from C.rivularis reduces excessive cadmium absorption.Therefore,con-sumption of C.rivularis likely does not pose a risk to human health.