南海北部沿岸贝类体内镉含量及健康风险评价

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

根据2007年和2009年对南海北部沿岸菲律宾蛤仔(Ruditapes Philippinarum)、翡翠贻贝(Perna viridis)、近江牡蛎(Crassostrea rivularis)、太平洋牡蛎(Crassostrea gigas)、文蛤(Meretrix meretrix)5种贝类的监测资料,对贝类体内Cd的含量水平进行了分析讨论;采用点估计的方法,评估贝类Cd的暴露量,对其安全性进行评价。结果表明,调查海域近江牡蛎、太平洋牡蛎、菲律宾蛤仔、翡翠贻贝和文蛤样品中Cd的平均含量分别为:1.80、0.38、0.12、0.26和0.15 mg.kg-1,其变化范围分别为:0.92～2.39 mg.kg-1、0.31～0.46 mg.kg-1、0.10～0.13 mg.kg-1、0.21～0.30 mg.kg-1和0.08～0.22 mg.kg-1。与其他海域贝类调查的数据相比,此次调查贝类体内Cd含量处于正常的波动范围。风险评估结果显示,近江牡蛎的风险商HQ>1,表明人体存在过量摄入Cd的风险;其他4种贝类的HQ<1,处于安全范围内。评价结果还显示,儿童的Cd暴露量高于成年人。此次调查近江牡蛎样品中Cd/Zn的比值(0.005)低于0.015的临界值,从微量元素平衡的角度,近江牡蛎中Cd的健康风险低。

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 differences 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 human health. Conversely, the other 4 shellfish species likely pose no risk as the Cd levels were lower than the values 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, consumption of C. rivularis likely does not pose a risk to human health.