Liang et al. 2019 — Heavy metals in Beijing foodstuffs: concentrations and health risk
This study measured concentrations of Cd, Cr, Pb, total As, and total Hg across 25 types of foodstuffs (cereals, vegetables, fruits, fish, and meat) collected in Beijing, China, then assessed non-carcinogenic health risk via target hazard quotients (THQ) and weekly intake comparisons with FAO/WHO provisional tolerable weekly intakes (PTWIs). Most foodstuff concentrations were below China’s National Food Safety Standard maximum limits, with the exception of Pb in chicken, fish, white gourd, and pork, and Hg in millet and mutton. All calculated THQ and TTHQ values remained below 1 on a single-food-group basis, but the combined TTHQ across all food groups reached 2.30, indicating a possible cumulative adverse effect from multi-pathway metal intake. Cereals and vegetables were identified as the dominant contributors to Cd and Pb dietary intake, accounting together for 91.5% of total Cd and 67.1% of total Pb consumed.
Key numbers
Cereal group mean concentrations (dry weight, mg/kg):
- Cr: 0.128 mg/kg (128 ppb)
- Cd: 0.020 mg/kg (20 ppb)
- Pb: 0.062 mg/kg (62 ppb)
- As (total): 0.028 mg/kg (28 ppb)
- Hg (total): 0.020 mg/kg (20 ppb)
Individual cereal values (mg/kg dry weight):
- Millet Pb: 0.072 ± 0.018; Millet Hg: 0.023 ± 0.006 (Hg exceeds China’s 0.02 mg/kg standard)
- Corn flour Pb: 0.060 ± 0.028; Corn flour Hg: 0.018 ± 0.013
- Wheat flour Pb: 0.045 ± 0.017; Wheat flour Cd: 0.023 ± 0.007; Wheat flour As: 0.024 ± 0.007; Wheat flour Hg: 0.020 ± 0.014
Estimated cereal dietary contribution (µg/d, adults at 366 g/person/day):
- Cd from cereals: 7.32 µg/d (24.8% of total Cd intake)
- Pb from cereals: 22.60 µg/d (23.8% of total Pb intake)
- Cr from cereals: 46.67 µg/d (22.7% of total Cr intake)
- As from cereals: 10.07 µg/d (29.6% of total As intake)
- Hg from cereals: 7.27 µg/d (46.6% of total Hg intake — highest single food group for Hg)
Weekly intakes (WIs) vs PTWIs (µg/kg bw/week):
- Cd: 3.4 calculated vs 7 PTWI
- Cr: 24.0 calculated vs 1050 PTWI
- Pb: 11.1 calculated vs 25 PTWI
- As: 4.0 calculated vs 15 PTWI
- Hg: 1.8 calculated vs 5 PTWI
THQ for cereals by metal: Cr 0.22, Pb 0.13, Cd 0.12, As 0.06, Hg 0.04. Total TTHQ for cereals: 0.57.
LODs (MLOD): Cd 0.01 mg/kg, Cr 0.05 mg/kg, Pb 0.12 mg/kg, As 0.40 µg/kg, Hg 0.25 µg/kg.
Methods (brief)
Sample collection: 25 foodstuff types from 4 Beijing sites, 3 replicates per foodstuff. Cereals washed with deionized water, dried; acid digestion with HNO3/H2O2 mixture at 160°C. Cd, Cr, Pb measured by ICP-AES (SPECTRO); total As and total Hg by atomic fluorescence spectrometry (AFS-930). Note: As and Hg are reported as total (not speciated); iAs and MeHg fractions are not distinguished. Health risk assessed via US EPA THQ methodology and FAO/WHO PTWI comparison.
Implications
Certification: Provides Beijing-specific cereal concentration data for Pb, Cd, total As, Cr, and total Hg. Useful for regional benchmarking but limited by small n (3 replicates per item) and lack of speciation. Total As values cannot serve as iAs proxies for HMT&C threshold purposes.
Courses: Good illustrative case for dietary exposure contribution analysis — demonstrates how high-volume staple foods (cereals, vegetables) dominate intake even when per-serving concentrations are modest. Millet Hg exceedance of China’s standard is noteworthy.
App: Cereal-group mean values are usable as rough regional benchmarks for Beijing, wet/dry weight basis noted. Speciation absent; app should flag that As data here is total As only.