He et al. 2013 — Dietary cadmium exposure in Shanghai adults over 40
A cross-sectional survey of 207 Shanghai residents aged over 40 years combined food frequency questionnaire data with measured cadmium concentrations in food, water, and tobacco to estimate both external and internal (urinary and blood) cadmium exposure. Mean daily dietary cadmium exposure was 12.8 µg/day, accounting for 25.8% of the provisional tolerable daily intake (PTDI of 49.5 µg/day based on JECFA 2010 PTMI of 25 µg/kg body weight). Total environmental exposure including tobacco was 16.7 µg/day (33.8% of PTDI). The probabilistic model found 93.4% of the population below the PTDI, though the extreme P90 reached 110.6 µg/day (223.5% of PTDI). Vegetables, rice, and seafood together accounted for 86.3% of dietary cadmium exposure.
Key numbers
Food cadmium concentrations (mg/kg, wet weight) from Shanghai 2008 survey (n=207):
| Food item | Mean Cd (mg/kg) | Median | P90 |
|---|---|---|---|
| Rice | 0.023 | 0.009 | 0.090 |
| Wheat flour | 0.014 | 0.011 | 0.023 |
| Coarse cereal | 0.006 | 0.006 | — |
| Vegetables (fresh) | 0.025 | 0.005 | 0.170 |
| Pork | 0.018 | 0.002 | 0.100 |
| Innards (offal) | 0.278 | 0.001 | 0.572 |
| Aquatic products | 0.043 | 0.007 | 0.091 |
| Egg | 0.005 | 0.003 | 0.012 |
| Milk | 0.001 | 0.001 | 0.003 |
| Dry bean | 0.019 | 0.007 | 0.100 |
| Fruit | 0.001 | 0.001 | 0.003 |
Dietary cadmium exposure by source (mean, µg/day):
| Source | Mean (µg/day) | Contribution (%) |
|---|---|---|
| Vegetables | 5.13 | 40.2% |
| Rice | 4.80 | 37.6% |
| Seafood | 1.09 | 8.5% |
| Pork | 0.50 | 3.9% |
| Total dietary | 12.77 | 100% |
Total environmental exposure:
- Mean: 16.73 µg/day (33.8% of PTDI)
- Median: 3.31 µg/day (6.7% of PTDI)
- Dietary P90: 20.57 µg/day
- Extreme P90 (dietary): 94.18 µg/day
- Tobacco contribution: 3.93 µg/day (mean; for smokers: 13.8 µg/day)
Sensitivity analysis (probabilistic model) — top contributors to total exposure:
- Tobacco cadmium level: 27.5%
- Tobacco consumption: 24.9%
- Vegetables: 20.2%
- Rice: 14.6%
Internal exposure (n=207):
- Mean urinary cadmium (UCd): 0.52 µg/L (range not stated; P95: 5.12 µg/L)
- Mean blood cadmium (BCd): 1.88 µg/L (P95: 1.77 µg/L for total; males higher than females, p<0.001)
- Smokers vs non-smokers: BCd significantly higher in smokers (mean 1.04 vs 0.30 µg/L; UCd no significant difference)
Positive correlations: BCd and environmental Cd exposure (R=0.52, P<0.01); tobacco Cd intake and BCd excluding non-smokers (R=0.26, P=0.049); UCd and age (R=0.15, P=0.037).
Probabilistic model (Monte Carlo, n=100,000 simulations): Lognormal distribution. Total population: mean 23.05, median 18.24, SD 18.02, 5th–95th percentile 6.8–55.1 µg/day.
Regulatory comparisons (mg/kg):
- Rice: China ML = 0.2; EFSA = 0.2; WHO = 0.4. Study P90 = 0.09 (well below China ML).
- Meat (excluding offal): China = 0.1; EFSA = 0.05; WHO = 0.05.
Methods (brief)
Cross-sectional design, convenience sampling from residents attending routine health checks at Songnan Town Community Health Center, Baoshan District, Shanghai, July 2008. Food frequency questionnaire (FFQ) with 39 food items from the National Nutrition Survey; cadmium concentrations in food from a 2010 Shanghai dietary cadmium exposure assessment (GFAAS method from Chinese national standard WS/T 32–1996). Blood and urine cadmium by GFAAS (Shimadzu AA-670). LOD: 0.05 µg/L for both matrices. Four water samples from local waterworks; water cadmium below LOD in all samples (assumed half-LOD = 0.025 µg/L). Tobacco cadmium assumed 1.5 mg Cd/kg based on Qian et al. Probabilistic estimation by Monte Carlo simulation (Crystal Ball software 11, 100,000 iterations). Statistical analysis by SPSS 12.0.
Limitations: convenience sample (not population-representative); adults only (excludes children); food categories pooled (specific infrequently consumed items excluded); cadmium during food processing not considered; no biomarkers for early renal dysfunction; other trace metals not examined.
Implications
Certification: Provides Cd concentration data for rice (P90 = 90 µg/kg) and vegetables (mean 25 µg/kg) in a non-polluted Chinese coastal city. Rice below China, EU, and Codex MLs at 90th percentile. Confirms vegetables as the highest contributor to dietary Cd in Shanghai, exceeding rice by volume. Useful as baseline for HMT&C ingredient page comparison with reported Asian dietary exposure benchmarks.
Courses: Demonstrates the relative contribution of different food groups to dietary cadmium exposure in a rice-dependent Asian population. Key teaching point: tobacco cadmium rivals dietary exposure in smokers (13.8 µg/day tobacco vs 14.0 µg/day dietary). Probabilistic vs point estimation comparison is an excellent methods teaching case.
App: Rice Cd mean 23 µg/kg, P90 90 µg/kg (wet weight) from Shanghai 2008. Vegetable Cd mean 25 µg/kg, P90 170 µg/kg. These are input-level contamination data for Chinese-origin produce, not product-level; relevant for ingredient profile calibration.