Overview
Sharef and co-authors measured leaching of ten heavy metals (aluminium, cadmium, Co, chromium, Cu, Fe, Mn, nickel, lead, Zn) from two locally unbranded yogurt container types in Erbil City, Kurdistan Region, Iraq: white plastic containers (WPC) and aluminum containers (ALC). Three leaching conditions mimicked cold storage, ambient distribution, and mild heating. Six food simulants were used alongside real yogurt. The study found that aluminum containers leach substantially more heavy metals than white plastic containers, with lead exceeding permissible limits and aluminum leaching exceeding the EC specific release limit and child provisional tolerable daily intake in several conditions.
Key numbers
Ten metals measured by ICP-OES across both container types and six simulants under three temperature-time conditions.
Aluminum containers (ALC) - Total Leached Metal Load (TLML, micrograms per liter) under 1stC (4 degrees C, 72 h):
| Simulant | TLML (micrograms/L) |
|---|---|
| 5% sodium carbonate | 2105 |
| 0.9% sodium chloride | 207 |
| Acetic acid pH 2.5 | 188 |
| Lactic acid pH 2.5 | 152 |
| 8% ethanol | 144 |
| Distilled water | 122 |
Specific regulated analytes in ALC leachates:
| Analyte | Simulant / condition | Reported value (micrograms/L) | Limit |
|---|---|---|---|
| lead (Pb) | 5% sodium carbonate, 1stC | 1408 | WHO/national permissible 1000 micrograms/L |
| lead (Pb) | 5% sodium carbonate, 2ndC | above permissible | 1000 micrograms/L |
| cadmium (Cd) | 5% sodium carbonate, 1stC | 83 | permissible 100 micrograms/L |
| aluminum (Al) | yogurt simulant, typical consumption | above EC SRL | EC SRL 0.50 mg Al/100 g food (5 mg/kg) |
White plastic containers (WPC): lead and cadmium were below detection limits in all simulants and all leaching conditions. Most metals in WPC leachates were below permissible limits in all conditions tested.
Aluminum leaching and child intake: The estimated aluminum intake via ALC-packaged yogurt exceeded the EFSA provisional tolerable daily intake for a 14 kg child (2.0 mg aluminium/day) in several conditions. The EC specific release limit of 0.50 mg aluminium/100 g food was exceeded for aluminum containers but not for white plastic containers.
Methods (brief)
Two locally unbranded container types (WPC and ALC) purchased from Erbil retail markets. Leaching tests at three temperature-time conditions: 1stC (4 degrees C, 72 h), 2ndC (25 degrees C, 24 h), 3rdC (60 degrees C, 2 h). Six simulants: distilled water, 0.9% NaCl, 8% ethanol, 5% sodium carbonate (pH 12.5), lactic acid (pH 2.5), acetic acid (pH 2.5). Ten metals measured by ICP-OES. Additional physicochemical parameters: pH, UV-absorbing extractable substances, oxidizable matter, global migration residue. Total leached metal load summed across all ten analytes per condition.
Evidence fitness
This study is relevant to plastic tubs as packaging for dairy products. The white plastic container data show that lead and cadmium were below detection in all conditions tested, providing context that standard plastic yogurt containers do not appear to contribute meaningfully to lead or cadmium at the conditions tested. The aluminum container data are more relevant to the cans/lids category and demonstrate that alkaline conditions (sodium carbonate simulant, pH 12.5) drive high lead and aluminium leaching from uncoated aluminum. The study is single-site (Erbil, Iraq) with locally unbranded containers; generalizability to commercial branded containers in other markets requires caution.
Limitations
Locally unbranded containers may not represent commercial branded containers in regulated markets. Sodium carbonate simulant (pH 12.5) is not a standard EU food simulant and represents an extreme alkaline condition not typical of yogurt storage. Sample size is small (two container types). No speciation for metals measured as totals. The IQ jurisdiction limits direct regulatory cross-reference to EU/US standards.
Related evidence
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