I pondered their reasons for calling this product “chemical free”:
a) Free of Synthetic Chemicals?
Perhaps the marketers mean “synthetic chemical-free”. Titanium dioxide can be considered natural in the sense that it is mined from the earth, but crude titanium dioxide from ores has to be purified via chemical and physical processes into pure, white titanium dioxide that is used in sunscreens.
Furthermore, if you are familiar with the unattractive white sheen attributed to titanium dioxide or zinc oxide powders in sunscreens, you will understand why the micronized or nano versions have become popular. These ultrafine particles go on clear and impart less of a tacky feel. Micronizing titanium dioxide requires further processing, such as coating or doping with chemicals (typically safe, innocuous ones) to keep the tiny particles from agglomerating. I couldn’t tell if the “chemical-free” sunscreen comprises micronized or non-micronized titanium dioxide as manufacturers are not required to state which version they use. But my point is that titanium dioxide is subject to chemical processing (making it a "chemical") and isn’t simply ground into particles from rocks in a quarry (even then it's still a "chemical"!).
b) "Chemical" Being the Opposite of "Physical"
Another explanation for calling the product “chemical free” is to differentiate it from products containing “chemical sunscreens”. Titanium dioxide and zinc oxide are known as “physical sunscreens”, a classification stemming from the mode of action: physical sunscreens physically deflect whereas chemical sunscreens absorb UV rays. Why not label the product as containing “physical sunscreens” or “mineral sunscreens”? I suppose those terms just don’t evoke the same excitement (or fear).
Sunscreen active ingredients are regulated by FDA (would they care if it’s not a chemical?) and dubbing a sunscreen “chemical free” seems oxymoronic to me. To be sure, not all chemicals are created equal and some are more hazardous than others. Chemical sunscreens have their issues (absorption into the skin, allergenicity, etc.) but calling a product “chemical free” because it comprises natural plant sourced or mineral ingredients does not move the conversation forward. A perfect sunscreen ingredient doesn’t exist today – physical and chemical sunscreens both have their respective shortcomings. Sunscreen formulation should be based on a balanced and informed understanding of different options. I don’t question their choice of titanium dioxide at all. However, promoting one option based on a creative re-interpretation of basic chemistry is a disservice to good science and to the public.
And by the way, that product did contain synthetic chemicals in the form of fragrance.
Side Notes:
#1: There are concerns that nanoparticles could penetrate the skin and be cytotoxic (i.e. toxic to cells). However, evidence thus far suggests that penetration is low [1], and the consumer advocacy group, EWG, believes that the benefits of using nano-titanium dioxide as sunscreens outweigh the risks.
#2: As mentioned earlier, titanium dioxide (TiO2) is a photocatalyst – when activated by UV light, it produces free radicals that have been harnessed in applications such as environmental remediation to break down organic contaminants e.g. CFCs. In my opinion, that more than qualifies titanium dioxide as a chemical. This photoactivity brings up another issue - the thought of titanium dioxide generating free radical in sunlight when it’s supposed to function as a sunscreen is disconcerting. Indeed, an in vitro study conducted by Serpone et al. showed that UV irradiation of TiO2 containing commercial sunscreens led to DNA damage in cells [2]. Eeek! However, such cytotoxicity is a concern primarily if the TiO2 particles penetrate deeper into the skin and into cells; otherwise they should hopefully keep their harmful photoactivity to the top layers of the skin, the stratum corneum, which comprises dead skin cells. Serpone et al. reported that they found a way to inactivate the photoactivity by modifying titanium dioxide although I could not find details in the scientific literature.
References:
1. Cross et al. Human Skin Penetration of Sunscreen Nanoparticles: In-vitro Assessment of a Novel Micronized Zinc Oxide Formulation. Skin Pharmacology and Physiology. 20 148-154 (2007)
2. Serpone et al. Inorganic and organic UV filters: Their role and efficacy in sunscreens and suncare products. Inorganica Chimica Acta360 794-802 (2007)
Posted by THY
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