This study measured As, Cd, tHg, and Pb separately in the yolk, albumen, and eggshell of 141 rural-farmed eggs (5 genotypes: Araucana, Leghorn, Warren Brown hybrid, Marans, Olive Egger) and 60 commercial organic supermarket eggs purchased in Italy. All analyses used ICP-MS with LOD 0.002 mg/kg and LOQ 0.005 mg/kg (wet weight). The key finding is that supermarket eggs had significantly higher Pb in all matrices while rural eggs had higher tAs in albumen and eggshell, and supermarket albumens showed detectable tHg while rural egg albumens were all below LOQ. Cadmium was below LOQ in all matrices for both types, attributed to the protective role of metallothionein at the ovarian level. The authors note no MRLs have been set for Pb, Hg, or Cd in eggs at the EU level, creating a food safety gap.
Key numbers
All values mg/kg wet weight, mean ± SD; LOQ = 0.005 mg/kg for all matrices.
Egg yolk:
- Rural (n=141): As = 0.011 ± 0.03 mg/kg; Cd = <LOQ; tHg = <LOQ; Pb = 0.089 ± 0.25 mg/kg (range by genotype: 0.023–0.141)
- Supermarket (n=60): As = 0.006 ± 0.01 mg/kg; Cd = <LOQ; tHg = <LOQ; Pb = 0.186 ± 0.04 mg/kg (all 5 supermarkets: 0.181–0.203)
Egg albumen:
- Rural: As = 0.112 ± 0.12 mg/kg; Cd = <LOQ; tHg = <LOQ; Pb = 0.039 ± 0.11 mg/kg
- Supermarket: As = 0.043 ± 0.06 mg/kg; Cd = <LOQ; tHg = 0.266 ± 1.65 mg/kg (highly variable; S1 = 1.077 ± 3.70, S3 = <LOQ); Pb = 0.688 ± 0.69 mg/kg
Eggshell:
- Rural: As = 0.202 ± 0.21 mg/kg; Cd = <LOQ; tHg = 0.006 ± 0.00 mg/kg (only 19/141 detectable); Pb = 0.022 ± 0.071 mg/kg
- Supermarket: As = 0.010 ± 0.004 mg/kg; Cd = <LOQ; tHg = 0.009 ± 0.004 mg/kg; Pb = 0.052 ± 0.20 mg/kg
Literature comparison table (Table 6) collects As, Cd, tHg, and Pb data from 20+ prior studies across Italy, Belgium, Bangladesh, Iran, Australia, Spain, USA, India, Pakistan, Greece, Taiwan, Brazil.
Methods (brief)
ICP-MS (Agilent 7700 series). Wet mineralization with concentrated nitric acid (J.T. Baker) followed by dilution. LOD = 0.002 mg/kg; LOQ = 0.005 mg/kg for all matrices (wet weight). Isotopes monitored: Hg-202 and Pb-208 in He mode; As-75 in HeHe mode. CRM BCR-185R Bovine Liver used for accuracy verification. No arsenic speciation performed; total As reported. Mercury reported as total Hg without MeHg speciation. Statistical analysis: Kruskal-Wallis + Dunn post-hoc (non-parametric), significance at p < 0.05.
Implications
Certification: This paper establishes that eggs from free-range and organic production systems can contain elevated Pb (supermarket) or elevated tAs (rural/free-range), and that Cd is consistently below LOQ in hen eggs across farming systems. The absence of EU MRLs for Pb, Hg, and Cd in eggs is a regulatory gap highlighted by the authors. Pb in supermarket egg albumens (mean 0.688 mg/kg) substantially exceeds the EU limit for raw milk (0.020 mg/kg), illustrating that the regulatory vacuum for eggs matters commercially.
Courses: Excellent case study comparing rural ethical farm vs. commercial organic supply chains. The Araucana genotype consistently showed highest Pb in yolk (0.141 mg/kg) while Warren Brown hybrids showed lowest (0.023 mg/kg), suggesting genotype effects worth exploring in sourcing decisions.
App: Contributes to the contamination profile for eggs. The tAs numbers (albumen dominates over yolk) and Pb numbers (yolk and albumen both significant) inform risk scoring when eggs appear in product ingredient lists.