China national food safety standards of cadmium in staple foods: Issues and thinking

Abstract

<p indent="0mm">Cadmium (Cd), as a class one carcinogen, is easily transferred from soil to the food chain, representing a potential threat to human health. Rapid industrialization in China during the last three decades has caused widespread contamination in agricultural soils. As a result, a considerable proportion of the rice grain in some areas of southern China has concentrations of Cd exceeding the Chinese food safety standard. This problem has raised a widespread concern regarding food safety and brought a big debate in China about whether the current food safety standard is reasonable. The food safety standard of Cd is not only critical for assessing soil environmental quality, but also important to reduce the current elevated dietary Cd intake for the general population. In this perspective, we summarize the history of establishment and revision in Chinese food safety standards of Cd in staple foods and discuss whether the current Cd safety limits for both rice and wheat are reasonable in terms of the tolerable limit for dietary Cd intake, dietary pattern, the current exposure level of Cd for the general pollution, and social-economic and international trading factors. The dietary Cd intake for the general population has doubled over the last <sc>25 years,</sc> from <sc>13.8 μg/d</sc> in 1990 to <sc>32.7 μg/d</sc> in 2011–2015, with the latter being approximately 61% of the provisional tolerable intake recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The growing body of evidence suggests no safe Cd intake limit for human health and consequently, dietary intake of Cd should be reduced as much as possible. The milling (i.e., polishing) process has an uncertain effect on change in Cd concentration in polished rice compared to the brown rice because of the uncertainty of the Cd spatial distribution pattern in rice grain. Furthermore, polished rice has higher bioavailability of Cd to humans than brown rice. These differences should be considered when extrapolating the food safety standard between brown rice and polished rice. According to the current exposure level and risk of Cd through consumption of rice, we contend that the current food safety limit for rice grain <sc>(0.2 mg/kg)</sc> in China is lenient for both the southern and northern general populations. It is unadvisable to be looser in further revisions of Chinese food safety standards. For wheat grain, the current safety limit <sc>(0.1 mg/kg)</sc> is reasonable for the northern population but strict for the southern population. Given the current contamination status and national food security and safety, the principle of ALARA (as low as reasonably achievable) should be applied to guild the amendment of the national food safety standard of Cd. There are several scientific perspectives to be further studied. First, epidemiological studies are required to establish the tolerable intake limit suitable to the Chinese ethnic characteristics and dietary patterns. Second, the new food safety standard should consider the subgroup populations with high Cd exposure risk, including infants, children, and local farmers who mainly consume home-grown rice with elevated Cd concentrations in Cd-contaminated regions. To reduce Cd exposure to the local population, effective mitigation strategies include exchanging high Cd home-grown rice with low Cd rice and increasing dietary nutrients and human nutrition.