Gacal et al. 2023 — Cadmium and lead in gluten and gluten-free bread, Poland
This peer-reviewed study measured Cd and Pb concentrations in 50 bread samples from the Polish market (Silesia Province) using ET-AAS (electrothermal atomic absorption spectrometry), then assessed non-carcinogenic and carcinogenic health risk for eight age groups using US EPA THQ/HQ and cancer risk methods. The central finding is that Cd concentrations ranked wheat-rye bread highest (mean 0.072 mg/kg) and gluten-free bread lowest (mean 0.021 mg/kg), contradicting the hypothesis that gluten-free breads — which typically contain rice or maize flour — would carry higher heavy metal loads for Cd and Pb. Lead was detectable above LOQ in only one wheat bread sample (max 0.152 mg/kg). Significant non-carcinogenic risk (HQ > 1) for Cd appeared only for the youngest children (6 months to <3 years) exposed to maximum wheat-rye bread concentrations; cancer risk for Cd and combined Cd+Pb exceeded 10-4 for children under 11 years in worst-case scenarios. The study concludes that at current contamination and consumption levels, children under 11 years face potential significant cancer health risk from Cd and Pb in wheat and wheat-rye bread.
Key numbers
Cd concentrations in bread (mg/kg fresh weight):
| Bread type | Min | Mean | Max |
|---|---|---|---|
| Gluten-free (n=10) | < LOQ | 0.021 | 0.040 |
| Wheat-rye (n=12) | 0.030 | 0.072 | 0.164 |
| Wheat (n=20) | 0.022 | 0.050 | 0.090 |
| Rye (n=8) | 0.008 | 0.041 | 0.088 |
Cd LOD: 0.0043 mg/kg; LOQ: 0.008 mg/kg.
Pb concentrations: below LOQ in all samples except one wheat bread sample (max 0.152 mg/kg; mean reported as ”—” since only one detectable result). Pb LOD: 0.044 mg/kg; LOQ: 0.08 mg/kg.
EU regulatory limits for reference:
- Cd in cereals: 0.10 mg/kg fresh weight (EU Reg 2021/1323); rye specifically: 0.050 mg/kg
- Pb in cereals: 0.20 mg/kg fresh weight (EU Reg 2021/1317)
- Exceedances: Cd in 2 of 8 rye bread samples exceeded the rye-specific 0.050 mg/kg limit; 1 wheat-rye sample exceeded the general 0.10 mg/kg Cd limit. The single detectable Pb sample did not exceed 0.20 mg/kg.
Non-carcinogenic risk (HQ) for Cd at maximum concentration in wheat-rye bread:
- Children 6–11 months: HQ = 1.78 (exceeds safe threshold of 1)
- Children 1–<2 years: HQ = 1.44
- Children 2–<3 years: HQ = 1.19
- All older groups: HQ < 1
Cancer risk (CR) for Cd at mean concentration in wheat-rye bread:
- Children 6–11 months: 1.3 × 10-4 (exceeds acceptable 10-4 threshold)
- Children 1–<2 years: 1.0 × 10-4
Cancer risk index (CRI, combined Cd + Pb at maximum wheat bread concentrations):
- Children 6–11 months: 3.54 × 10-4
- Children 1–<2 years: 2.86 × 10-4
- Children 2–<3 years: 2.36 × 10-4
- Children up to < 11 years: all exceed 10-4
Consumption assumption: 100 g bread/day (approximately 4 slices), applied uniformly across age groups. Authors note this is high but possible for youngest groups.
Methods (brief)
ET-AAS (electrothermal atomic absorption spectrometry) on Savanta Sigma spectrometer (GBC, Australia). Microwave closed-vessel mineralization: 1 g sample in HNO3 + H2O2. Matrix modifier for Pb: NH4H2PO4 + Mg(NO3)2. LOD Cd: 0.0043 mg/kg; LOQ Cd: 0.008 mg/kg. LOD Pb: 0.044 mg/kg; LOQ Pb: 0.08 mg/kg. Wavelengths: Cd 228.8 nm, Pb 217 nm. Health risk: US EPA HQ/THQ and cancer risk (slope factor) methods for 8 age groups. Note: only Cd and Pb measured; no As, Hg, or Ni data.
Implications
Certification: Provides bread-specific Cd concentration data for Poland/EU market. The finding that wheat-rye bread carries the highest Cd load (mean 0.072 mg/kg) while gluten-free bread carries the lowest (mean 0.021 mg/kg) is counterintuitive given that gluten-free breads often contain rice flour, which is a high-iAs ingredient. The authors note the absence of As and Hg measurements as a study limitation. HMT&C product pages for baked goods should reflect this Cd hierarchy: wheat-rye > wheat > rye > gluten-free for Cd.
Courses: Good teaching case for population-stratified risk assessment — the HQ and CR calculations demonstrate why children under 3 years face qualitatively different risk from the same bread consumed at the same rate as adults, due to lower body weight. The gluten-free paradox (lower Cd but expected higher As) is pedagogically valuable.
App: Mean Cd values by bread type (gluten-free: 21 ppb; rye: 41 ppb; wheat: 50 ppb; wheat-rye: 72 ppb; all in µg/kg) are usable for Polish/EU market bread Cd profiling. Pb is effectively below LOQ for all bread types except one outlier wheat sample. As, Hg, and Ni data absent from this study; those fields remain uncharacterized for bread from this source.