From Ecopedia

Overview

Titanium Dioxide (TiO₂) is a common oxide of titanium that occurs naturally. TiO₂ is found in a range of products that take advantage of the its highly reflective properties, including: sunscreen, cosmetics, fake snow, and food additives.

Studies have shown that TiO₂ nanoparticles are detrimental to organic life, resulting in cancer, birth defects, and asbestos-exposure like symptoms. Particles can enter the body through ingestion, inhalation and absorption.

Environmental Information

Manufacturing Byproducts
The purification and processing of TiO₂ results in toxic byproducts such as ferric chloride (FeCl₃).

Solar Cells
Although not the most efficient, thin-film solar cells utilizing TiO₂ offer higher ^price/_{performance ratio} (^kWh/_{m²・annum・dollar}) than the more efficient models. This advantage will allow for increased market penetration and widespread adoption of solar energy.

Photocatalysm
Titanium dioxide displays catalytic properties when exposed to UV light. The commercially available NOxer utlizes this property to convert harmful nitrogen oxides (NO_x), created during high temperature combustion, into harmless nitrates (NO₃^-).

References

http://en.wikipedia.org/wiki/Titanium_dioxide http://www.aolnews.com/nanotech/article/amid-nanotechs-dazzling-promise-health-risks-grow/19401235 http://www.eurovia.com/en/produit/136.aspx http://en.wikipedia.org/wiki/Air_pollution#Pollutants