Titanium dioxide is a naturally occurring mineral that deflects light, including ultraviolet rays from the sun. It is used as a pigment in paints and protective coatings used in the manufacture of airplanes, automobiles, boats and construction materials. This mineral also supplies the sun protection factor to sunscreen products. However, there are concerns about the safety of titanium dioxide sunscreen.
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Titanium dioxide is an oxide of titanium, a chemical element that resides in the Earth’s crust. It is mined in its naturally occurring state, or from other minerals. One of the most common and pure forms of titanium dioxide is obtained from rutile, a mineral found in beach sand that supplies the starlike qualities seen in some gemstones, most notably rubies, sapphires and topaz.
Small particle sizes of the titanium dioxide are used in the production of sunscreen lotions. These particles are coated with silica to prevent the mineral from acting as a catalyst in the presence of ultraviolet light, which would produce toxic byproducts commonly known as free radicals. Collectively, these micronized particles of titanium dioxide are referred to as nanoparticles, which are measured in nanometers, with each representing one-billionth of a meter. To put that into perspective, that’s roughly 100,000 times smaller than the width of a single strand of human hair.
Toxicity in Mice
According to a study published in the July 29, 2009, issue of “Particle and Fibre Toxicology,” titanium dioxide adversely affects the expression of various genes involved in central nervous functioning in newborn mice whose mothers were exposed to the mineral in nanoparticle form. Specifically, changes in expression of the genes affected are associated with learning disabilities, autistic disorders and epilepsy in the young, as well as schizophrenia, Alzheimer's disease and Parkinson's disease later in life.
Toxicity in Humans
A report published on Aug. 19, 2009, by Friends of the Earth states that nanoparticles can penetrate human skin due to their small size. In fact, the organization says that nanoparticles of titanium dioxide used in sunscreens typically measure a mere 20 to 30 nanometers or less. Once penetrating the skin, the substance may migrate to multiple organs via the bloodstream. Moreover, Peter Wick and colleagues reported in the March 2010 issue of “Environmental Health Perspectives” that free nanoparticles in the bloodstream are capable of crossing the barrier of the human placenta.
According to an article written by Matthew Cimitile for Environmental Health News, researchers from the University of Toledo found that nanoparticulate titanium dioxide disrupts the function of bacteria within 60 minutes of exposure, which could negatively affect beneficial microbes that help to filter wastewater in sewage treatment plants. In addition, the results of a collaborative study between Arizona State University, the Georgia Institute of Technology and Tsinghua University in China showed that titanium dioxide nanoparticles have entered the food chain of aquatic animals, such as the Zebrafish. The study was published in the May 2010 issue of “Chemosphere.”