Scientific Opinion on the safety evaluation of the substance zinc oxide, nanoparticles, uncoated and coated with [3‐(methacryloxy)propyl] trimethoxysilane, for use in food contact materials

Abstract

. Scientific Opinion on the safety evaluation of the substance zinc oxide, nanoparticles, uncoated and coated with [3-(methacryloxy)propyl] trimethoxysilane, for use in food contact materials. EFSA Journal 2015;13(4) The zinc oxide nanoparticles are intended to be used as a transparent ultraviolet light (UV) absorber in all types of polyolefins. When coated with [3-(methacryloxy)propyl] trimethoxysilane, the coating is up to 2 % by weight of the zinc oxide. The additive is to be used in the polymer at a maximum content of 2 % and 3 % by weight for the uncoated and the coated species, respectively. The plastics are intended to be used in contact with all types of foodstuffs for long-term storage at room temperature.The substance is used as a powder in nanoform. In the final polymer the nanoparticles are still present but largely aggregated. Zinc oxide particle clusters were present with a median number-based size of 205 nm for low-density polyethylene (LDPE) with 2 % of uncoated zinc oxide and of 120 nm for LDPE with 3 % of coated zinc oxide.Specific migration of the substance was tested from LDPE films (thicknesses 30-40 µm), containing the maximum use level of uncoated and coated species, into 3 % acetic acid and 10 % and 50 % ethanol for 10 days at 60 °C. Migration of zinc into 3 % acetic acid was high: up to 7.6 mg/kg (2 % zinc oxide), and up to 17.3 mg/kg (3 % coated zinc oxide). Migration of zinc into 10 % and 50 % ethanol was up to 80 µg/kg for the coated and uncoated species.The applicant provided data from a stress test on the migration test samples, which were in contact with iso-octane for 10 days at 20 °C to generate polymer swelling. The absence of any detectable zinc (< 0.1 µg/kg) in the swelling simulant iso-octane suggests that the up to 80 µg/kg of zinc detected in the 10 % and 50 % ethanol simulants is due to slight solubilisation of zinc oxide releasing ionic zinc. This would be consistent with current scientific understanding on the lack of the diffusion potential of nanoparticles in polymers (Bott et al., 2014a, b, c). No direct evidence is available, however, on the physical form of this released zinc. In the event that it was in particulate form, it would nonetheless be expected to dissolve immediately into ionic zinc on contact with acid foods or stomach acid. For the 3 % acetic acid simulant, based on the solubility results, the high level of migration is clearly driven by solubilisation of zinc by the acidic media with dissolution of zinc oxide to the soluble ionic form (i.e. Zn 2+ ).In 2003 The CEF Panel, after having considered the above-mentioned data, concluded that the substance zinc oxide in nanoform, uncoated or coated with [3-(methacryloxy)propyl]trimethoxysilane, does not migrate in nanoform, and therefore the safety evaluation focuses on the migration of soluble ionic zinc. The available migration data for ionic zinc coming from the intended application comply with the current specific migration limit (SML), but in combination with dietary exposure from other sources the UL of...

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