Nanomaterials Remain Under Increasing SCCS Scrutiny

Introduction

Nanomaterials in cosmetic products—defined under Article 2(1)(k) of Regulation (EC) No 1223/2009 as insoluble or biopersistent materials intentionally manufactured with one or more external dimensions, or an internal structure, on the scale from 1 to 100 nm—remained subject to intensifying scientific and regulatory scrutiny throughout 2021 [89]. The unique physicochemical properties of nanomaterials, including enhanced dermal penetration potential, increased surface reactivity, and altered toxicokinetic behavior compared to bulk materials, necessitate specialized safety assessment approaches that extend beyond conventional toxicological evaluation [90]. The Scientific Committee on Consumer Safety (SCCS) continued to issue opinions on specific nanomaterials, frequently concluding that submitted data were insufficient to demonstrate safety, thereby driving reformulation activity and heightening compliance obligations for Responsible Persons [91].

Article 16 of Regulation (EC) No 1223/2009 establishes a specific regulatory framework for nanomaterials, requiring notification to the European Commission six months prior to placing a product containing nanomaterials on the market [92]. This notification must include detailed physicochemical characterization, toxicological data, and safety assessment information, enabling the Commission to request an SCCS opinion on any nanomaterial [93]. The SCCS guidance on the safety assessment of nanomaterials in cosmetics (SCCS/1484/12, updated in SCCS/1611/19) provides methodological recommendations that emphasize the importance of comprehensive characterization, including particle size distribution, shape, surface chemistry, crystallinity, and agglomeration/aggregation state [94]. By November 2021, the SCCS had issued numerous opinions concluding that nanomaterials could not be considered safe due to data gaps, creating significant uncertainty for manufacturers and driving demand for advanced testing strategies [95].

Regulatory Framework and Legal Analysis

Article 16(1) of Regulation (EC) No 1223/2009 requires that cosmetic products containing nanomaterials be notified to the Commission six months before being placed on the market, except for nanomaterials used as colorants, UV filters, or preservatives listed in Annexes IV, VI, or V, which are subject to separate authorization procedures [96]. The notification must include: (a) the identification of the nanomaterial including its chemical name (INCI name) and other descriptors; (b) the specification of the nanomaterial including size of particles, physical and chemical properties; (c) an estimate of the quantity of nanomaterial contained in cosmetic products intended to be placed on the market per year; (d) the toxicological profile of the nanomaterial; (e) the safety data of the nanomaterial relating to the category of cosmetic product as used in the cosmetic product; and (f) the reasonably foreseeable exposure conditions [97].

Article 16(3) empowers the Commission to request the SCCS to provide an opinion on the safety of nanomaterials for use in cosmetic products within six months of receipt of the notification [98]. The SCCS opinion must address whether the nanomaterial, when used in the specified cosmetic product categories under the stated conditions of use, poses a risk to human health [99]. If the SCCS concludes that the nanomaterial is unsafe, Article 16(4) requires the Commission to amend Annexes II or III to prohibit or restrict the nanomaterial [100]. This regulatory mechanism creates a precautionary framework where nanomaterials are subject to ongoing scientific review, and market access depends on demonstration of safety through comprehensive data submission [101].

Article 19(1)(g) requires that the presence of nanomaterials be clearly indicated in the list of ingredients, with the word “nano” in brackets following the ingredient name [102]. This labelling requirement enables consumer choice and facilitates post-market surveillance by clearly identifying products containing nanomaterials [103]. Article 13 CPNP notification must also identify nanomaterials present in the formulation, ensuring that poison centers and enforcement authorities have access to this information [104].

The SCCS guidance documents SCCS/1484/12 and SCCS/1611/19 provide detailed methodological recommendations for nanomaterial safety assessment [105]. These guidance documents emphasize that nanomaterials cannot be assessed through read-across from bulk materials due to size-dependent changes in physicochemical properties and biological behavior [106]. Comprehensive physicochemical characterization is essential, including: particle size distribution (measured by multiple orthogonal techniques such as dynamic light scattering, transmission electron microscopy, and analytical ultracentrifugation); shape and morphology; surface area; surface chemistry and coating; crystallinity; agglomeration and aggregation state; and purity [107]. The guidance specifies that characterization must be performed on the nanomaterial as manufactured, as incorporated into the cosmetic formulation, and as applied to skin, recognizing that formulation matrix and application conditions may alter nanomaterial properties [108].

Toxicological assessment of nanomaterials must address all endpoints required under Article 10 and the SCCS Notes of Guidance (10th Revision), with particular emphasis on dermal absorption, repeated-dose toxicity, and genotoxicity [109]. The SCCS guidance recommends in vitro dermal absorption studies using validated skin models, supplemented by in vivo studies if in vitro data suggest significant penetration beyond the stratum corneum [110]. Genotoxicity testing should include bacterial reverse mutation assays, in vitro micronucleus tests, and, if positive results are obtained, in vivo follow-up studies [111]. Repeated-dose toxicity studies should use appropriate routes of administration (typically dermal or oral) and dose levels that achieve systemic exposure, enabling derivation of a NOAEL for margin of safety calculation [112].

Toxicological and Safety Science Considerations

The toxicological assessment of nanomaterials presents unique challenges arising from their size-dependent properties and potential for enhanced biological interactions [113]. Dermal absorption is a critical endpoint, as the stratum corneum typically prevents penetration of particles larger than 20-40 nm, but nanomaterials may exploit intercellular lipid pathways, hair follicles, or compromised skin barrier to achieve deeper penetration [114]. In vitro studies using Franz diffusion cells with human or porcine skin demonstrate that most nanomaterials used in cosmetics, including titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles in sunscreens, remain largely confined to the stratum corneum and upper epidermis, with minimal systemic absorption [115]. However, factors such as particle size, surface coating, formulation vehicle, application duration, and skin condition (e.g., sunburn, eczema, mechanical damage) can influence penetration [116].

The SCCS has consistently emphasized that dermal absorption data must be generated using the specific nanomaterial formulation intended for market, as physicochemical properties in the final product may differ from the raw material [117]. For example, TiO₂ nanoparticles are typically surface-coated with alumina, silica, or organic compounds to reduce photocatalytic activity and improve dispersion stability [118]. These coatings alter surface chemistry and may influence dermal penetration and biological reactivity [119]. The SCCS guidance requires that dermal absorption studies characterize the nanomaterial in the test system, confirming that particle size and coating integrity are maintained throughout the study [120].

Systemic exposure dosage (SED) calculation for nanomaterials follows the same principles as conventional ingredients, but must account for the typically low dermal absorption [121]. SED is calculated as: SED (mg/kg bw/day) = (A × C × DAp) / BW, where A is the amount of product applied per day, C is the concentration of the ingredient in the product, DAp is the dermal absorption percentage, and BW is body weight [122]. For nanomaterials with dermal absorption below 1%, SED values are typically very low, resulting in high margins of safety even when NOAEL values are modest [123]. However, the SCCS has cautioned that low systemic exposure does not preclude local toxicity at the application site, and safety assessment must consider both systemic and local effects [124].

Genotoxicity is a particular concern for nanomaterials due to their potential to generate reactive oxygen species (ROS), induce oxidative stress, and cause indirect DNA damage through inflammatory responses [125]. In vitro genotoxicity assays may yield positive results for nanomaterials that are negative in bulk form, reflecting enhanced cellular uptake and intracellular reactivity [126]. The SCCS guidance recommends a weight-of-evidence approach, integrating results from multiple genotoxicity assays and considering physicochemical properties, cellular uptake, and mechanism of action [127]. If in vitro genotoxicity is observed, in vivo studies are required to assess whether the effect occurs under realistic exposure conditions [128].

Repeated-dose toxicity studies provide the basis for NOAEL determination and margin of safety calculation [129]. For nanomaterials, the SCCS recommends 90-day oral or dermal studies in rodents, with comprehensive histopathology and clinical chemistry to detect organ-specific toxicity [130]. Inhalation toxicity may also be relevant for spray products, as nanomaterials can reach the deep lung and cause pulmonary inflammation or fibrosis [131]. The SCCS has issued several opinions concluding that nanomaterials cannot be considered safe for use in spray applications due to insufficient inhalation toxicity data [132].

Margin of safety (MoS) calculation for nanomaterials follows the standard formula: MoS = NOAEL / SED [133]. An MoS ≥100 is generally considered acceptable for non-sensitizing ingredients, providing a safety factor that accounts for interspecies extrapolation (10-fold) and intraspecies variability (10-fold) [134]. However, the SCCS may require higher MoS values for nanomaterials if data gaps exist or if the nanomaterial exhibits concerning properties such as biopersistence, bioaccumulation, or genotoxic potential [135]. For example, SCCS opinions on carbon black nanoparticles and fullerenes have concluded that safety cannot be demonstrated due to insufficient data on long-term toxicity and potential for accumulation in tissues [136].

Practical Compliance Guidance

For Responsible Persons, compliance with Article 16 nanomaterial requirements necessitates early engagement with suppliers to obtain comprehensive physicochemical characterization and toxicological data [137]. Many cosmetic ingredient suppliers provide nanomaterials without the detailed characterization required by SCCS guidance, necessitating additional testing or reformulation with well-characterized alternatives [138]. The notification dossier submitted under Article 16 must include all information specified in Article 16(3), and incomplete submissions may trigger SCCS review and potential restriction [139].

Safety assessment under Article 10 must address all SCCS guidance recommendations, including nanomaterial-specific considerations [140]. Part A of the CPSR (Cosmetic Product Safety Information) must include detailed physicochemical characterization of the nanomaterial, including particle size distribution measured by multiple techniques, surface chemistry, coating composition, and stability in the formulation [141]. Part B (Cosmetic Product Safety Assessment) must evaluate dermal absorption using validated methods, calculate SED and MoS, and address potential local effects such as skin irritation, sensitization, and photo-induced toxicity [142]. If the nanomaterial is used in a spray product, inhalation exposure must be assessed, and the SCCS guidance recommends that nanomaterials not be used in spray applications unless inhalation safety is demonstrated [143].

CPNP notification under Article 13 must identify nanomaterials present in the formulation, and Article 19 labelling must include the word “nano” in brackets following the ingredient name [144]. Failure to comply with these requirements constitutes a violation of Regulation (EC) No 1223/2009 and may result in enforcement action under Article 25 [145]. Market surveillance authorities increasingly use analytical techniques such as single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS) to verify nanomaterial labelling claims and detect undeclared nanomaterials [146].

For products containing nanomaterials subject to SCCS review, Responsible Persons should monitor the Commission’s nanomaterial catalogue and SCCS opinion pipeline [147]. If an SCCS opinion concludes that a nanomaterial is unsafe, Article 16(4) requires the Commission to amend the relevant Annex, typically resulting in prohibition or restriction [148]. Responsible Persons should develop contingency plans for reformulation, including identification of alternative ingredients and preparation of updated safety assessments [149]. The six-month notification period under Article 16(1) provides limited time for reformulation if an SCCS opinion is negative, and proactive planning reduces market disruption [150].

Conclusion

Nanomaterials in cosmetics remain subject to rigorous scientific scrutiny under the specialized regulatory framework established by Article 16 of Regulation (EC) No 1223/2009 and the methodological guidance provided by the SCCS. The unique physicochemical properties and toxicological behavior of nanomaterials necessitate comprehensive characterization and safety assessment that extends beyond conventional approaches. The SCCS’s frequent conclusions that submitted data are insufficient to demonstrate safety reflect the high evidentiary standards required for nanomaterial approval and underscore the importance of early supplier engagement, robust testing strategies, and proactive compliance planning. As analytical capabilities and toxicological understanding continue to evolve, Responsible Persons must maintain vigilance regarding SCCS opinions and be prepared to reformulate products if nanomaterials are restricted or prohibited under Article 16(4).

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