Nowadays, Cadmium (Cd) is a common toxic metal in soil pollution. The nationwide survey of soil pollution in China indicated that the pollution of Cd is very severe, and the over standard rate of Cd is 7.0%. According to a national survey, nearly 65% of the rice produced near the mining area contains more Cd than the national food standard (0.2 mg/kg). There is widespread concern that health risk caused by the accumulation of heavy metals in the body via rice consumption.  

In order to evaluate the heavy metals in contaminated food, the bioavailability of metals must be measured. It is the indicator of the greatest oral route bioavailability of pollutants, so many studies on the bioavailability of pollutants take bioavailability as the starting point and object of research. Usually, in vitro simulation test (in Vitro) has the advantages of overcoming the high cost, long cycle and moral defects of animal models. However, whether in vitro simulation can effectively predict bioavailability and regulatory factors is unclear.  

Researchers from South China Botanical Garden of the Chinese Academy of Sciences conducted both in vitro bioaccessibility (using four methods) and in vivo bioavailability (using a mouse model) of Cd from six kinds of rice.

The relative bioavailability (RBA) for Cd ranged from 15 to 56%, 18 to 56% and 3.71 to 54% based on kidney, liver and femur, respectively, which was negatively correlated with total Cd concentration in contaminated rice. Results of cadmium bioaccessibility in rice varied among different assays.

When the relationship between the in vitro and in vivo data was assessed, all the correlations between the four in vitro methods and the mouse assay based on the liver or kidney were generally weak.

Results of in vitro digestion models varied drastically among the different methods, suggesting that there were limitations for the in vitro methods to predict Cd relative bioavailability in contaminated rice.

Together with the observation of poor correlations between the in vivo and in vitro results, it is strongly suggested that further exploration and more optimization of in vitro methods are required for use in human health risk assessment.  

The research results entitle "Bioavailability and bioaccessibility of cadmium in contaminated rice by in vivo and in vitro bioassays" was published in Science of The Total Environment.