Sun et al. 2022 — Chinese provisional PTMI for cadmium: derivation and rice ML justification
This policy note from the China National Center for Food Safety Risk Assessment (CFSA) presents the derivation of a provisional health-based guidance value (HBGV) for dietary cadmium exposure in China, recommending maintenance of the Joint FAO/WHO Expert Committee on Food Additives (JECFA) provisional tolerable monthly intake (PTMI) of 25 µg/kg body weight for the Chinese population. The work was conducted in response to a review of China’s GB2762-2022 National Food Safety Standard, which maintained the existing cadmium maximum limit (ML) in rice at 0.2 mg/kg — a value first established in 1984. The analysis included a population of 7,152 participants across cadmium-contaminated regions of China, using a concentration-effect model linking urinary cadmium to β2-microglobulin (B2M) as a renal tubular biomarker and toxicokinetic models specific to the Chinese population to derive dietary intake from urinary biomarkers.
Key numbers
Cadmium ML in rice under China GB2762-2022: 0.2 mg/kg (polished rice). For comparison: Codex Alimentarius Commission (CAC) ML: 0.4 mg/kg; EU: 0.15 mg/kg; Republic of Korea: 0.2 mg/kg; Japan: 0.4 mg/kg; Russia and Australia: 0.1 mg/kg. Recommended PTMI (China): 25 µg/kg bw/month, consistent with JECFA. Sample: 7,152 participants from 6 PLADs; 67.0% aged ≥50; all were long-term local rice consumers (≥30 years). Biomarkers: urinary cadmium (ICP-MS) and urinary B2M (biochemical analyzer). Models used: one-compartment TK model and physiologically based TK (PBTK) model optimized for Chinese non-smoking residents in Shanghai. The assessment report was reviewed and approved by the Sub-Committee on Chemical Hazard of the National Food Safety Risk Assessment Expert Committee on 27 May 2021.
Methods (brief)
Concentration-effect model (Hill model, piecewise linear model, generalized additive model) relating urinary cadmium to B2M; one-compartment TK and PBTK models to derive dietary intake from urinary cadmium; 24-hour dietary recall for food consumption data; ICP-MS for urinary cadmium and food cadmium. Parallel meta-analysis of updated international epidemiological literature.
Implications
Certification: this is the authoritative Chinese derivation of the cadmium PTMI, directly relevant to the regulatory context for cadmium in rice and food products sold in China and for comparison with EFSA and JECFA PTMI derivations.
Courses: exemplary case for how national regulatory agencies derive HBGVs from population-specific biokinetic data; illustrates divergence between EU (0.15 mg/kg), China (0.2 mg/kg), and Codex (0.4 mg/kg) MLs for cadmium in rice.
App: the confirmed 25 µg/kg bw/month PTMI and 0.2 mg/kg ML in rice are directly relevant to risk estimation for rice-containing products targeting Chinese market or Chinese-heritage consumers.