It’s not just solvents such as methylene chloride that are coming under scrutiny as suspected human carcinogens. (I wrote about methylene chloride in the June, 2017 issue of Popular Woodworking.) The European Chemicals Agency’s Committee for Risk Assessment (RAC) just classified titanium dioxide as a suspected cause of cancer.
What is titanium dioxide (TiO2)? It’s a white inorganic pigment that occurs naturally in certain rocks and mineral sands. It has been used for decades in many products, including paints, cosmetics, sun blockers, foods, most toothpastes, and pills and tablets.
TiO2 is unique in several respects. It is whiter than other white pigments, often referred to as the “whitest white,” but more importantly, it has an extremely high refractive index. This refers to how much light is bent or refracted when entering a material. So titanium dioxide has better tinting strength and opacity than other pigments. It’s often used in non-white paints, in addition to white, to improve these two qualities.
Titanium dioxide also reflects harmful radiation, so it’s used in sun blockers.
The RAC bases its conclusion on the same type rat studies the EPA uses in its conclusion that methylene chloride, used in paint strippers, causes cancer. The coatings industry has pushed back the same way the stripper manufacturers have, saying there’s no evidence TiO2 causes cancer in humans.
If this finding by the RAC passes up through the chain of regulatory bodies in the usual way, we will soon find that many of the common products we use will include a warning that they include substances that are suspected carcinogens. Or the products will be reformulated, so as not to include this warning, and they won’t be as effective.
– Bob Flexner