Nanomaterials and How the Hotlist Treats Them

Titanium dioxide shows up in an enormous range of cosmetics, as a white pigment in makeup, as an opacifier in lotions, and in mineral sunscreen formulations. But the exact same chemical name can describe two meaningfully different materials depending on how small the particles are ground down, and that distinction is exactly where nanomaterial rules come into play.

Same INCI name, different physical form

INCI naming identifies a substance chemically. Titanium Dioxide is Titanium Dioxide whether the particles are a few microns across or down in nanometer range. What changes at the nano scale isn't the chemistry, it's the physical behavior: smaller particles have vastly more surface area relative to their mass, they can scatter and absorb light differently, and depending on the product type, they can interact with skin or be inhaled differently than their conventional-sized counterparts.

Because the safety profile can shift with particle size even when the chemical identity doesn't, the Cosmetic Ingredient Hotlist and Health Canada's broader framework treat nanoscale forms as a distinct consideration from conventional forms of the same substance. That means a formulator can't assume that because "Titanium Dioxide" appears as an accepted ingredient in one form, any particle size of it is automatically fine.

Why titanium dioxide and zinc oxide are the classic examples

Both of these are common physical UV filters, valued because they sit on the skin's surface and scatter or reflect UV light rather than absorbing it chemically. In their conventional, larger-particle form, they tend to leave a visible white cast, which is why cosmetic chemists have leaned toward smaller particle sizes to improve cosmetic elegance, better spreadability, less chalkiness, more transparency on skin tone.

That drive toward smaller particles is precisely what puts these two ingredients under nanomaterial scrutiny. The finer the grind, the more likely the material falls into a nano classification, and the more relevant it becomes to confirm how the Hotlist and other regulatory pathways treat that specific form, separate from how they'd treat the coarser version of the same chemical.

What this means practically for a formulator

A few practical takeaways if you're using either of these ingredients, or any other material where nano-sized grades are commercially available:

• Get particle size confirmation from your supplier. A certificate of analysis or technical data sheet should specify whether the grade you're buying is nano or conventional. Don't assume based on marketing language like "micronized," which doesn't always mean nano.
• Check current guidance for that specific particle size. Since this is an area that regulators actively revisit as science develops, treat any general statement, including this one, as a starting point for verification rather than a final answer. Confirm against Health Canada's current published guidance for the specific form you're using.
• Keep the two forms straight in your documentation. If you reformulate from a conventional grade to a nano grade of the same nominal ingredient, that's a meaningful change worth treating carefully in your filing, not a cosmetic tweak.

Beyond these two ingredients

Titanium dioxide and zinc oxide get the most attention because they're common and because the cosmetic benefit of going nano is so directly tied to appearance and feel. But the same principle, that particle size can change how a substance is regulated, applies more broadly to any nanomaterial used in a cosmetic. If you're working with a novel nano-scale ingredient of any kind, it's worth treating that as its own research question rather than assuming standard bulk-material guidance covers it.

Where this fits into a notification

When you're filing a Cosmetic Notification Form, the INCI name you declare doesn't automatically communicate particle size to a reviewer, which is exactly why keeping accurate internal documentation on the form of each ingredient you use matters. If Health Canada's screening or a follow-up request specifically concerns nano form, having your supplier's particle size data on hand ready to reference saves a lot of back and forth.

Cosmetic Comply's ingredient screening flags substances with known nanomaterial considerations so you know to double check particle size documentation before filing, rather than discovering the distinction matters only after a question comes back on your notification. If you're formulating with UV filters or any other ingredient available in both conventional and nano grades, that's exactly the kind of detail worth nailing down early, not after your product's already labeled and boxed.