Introduction. The safety of E171 (TiO₂) is debated due to the potential genotoxicity of its nanoparticles (NPs, <100 nm). EFSA concluded that a safe level cannot be established (EU ban since 2022), while other countries (USA, UK, Canada, Australia) permit its use under conditions. This work aimed to estimate a safe NP limit in E171 and screen Russian market samples.

Methods. Meta-analysis of oral toxicity studies of nano-TiO₂ (<100 nm) was conducted. Ten E171 samples from the Russian market were analyzed by DLS (0.1% w/w in deionized water, 20 min sonication, 2 W/cm³). Number-based proportion of particles <100 nm was calculated.

Results. The meta-analysis revealed numerous effects of nano-TiO2 in animals (biochemical alterations, oxidative stress, genotoxicity, immune and reproductive disorders), despite low bioavailability (<0.1%). The lower 25th percentile NOAEL for nano-TiO₂ was 10 mg/kg bw/day. Using a safety factor of 100, a hypothetical safe intake of 0.1 mg/kg bw/day was derived. Total dietary exposure to TiO₂ is approximately 1 mg/kg bw/day (max. mean, mg/kg bw/day, based on JECFA 2024: USA - 0.19, Netherlands - 1.4, China - 0.3, Europe - 3.9). Thus, the NP fraction in E171 should not exceed 1% by mass (~20% by particle number) to stay below 0.1 mg/kg/day. DLS analysis revealed NPs in 7 out of 10 Russian samples, with their proportion reaching up to 7% by number, which is below the proposed safe limit.

Conclusion. Screening of ten E171 samples revealed a nanosized fraction in seven of them (up to 7% by number), which does not exceed the calculated safety level. The obtained results indicate the feasibility of introducing a hygienic standard limiting the nanoparticle content in E171 and the need for expanded monitoring of this food additive.

Funding. Ministry of Science and Higher Education of the Russian Federation (FGMF-2025-0004).