There are several proposed remediation techniques that use nanotechnology. For example, solar photocatalysis using titanium dioxide nanoparticles can degrade pollutants like volatile organic compounds and nitrous oxides and consequently has been used in cement and commercial plants. Paints enriched with Nano titanium dioxide, replacing organic biocides, are used to keep the surfaces of buildings clean.Soil remediation of abandoned and old military and industrial sites has become a great challenge in industrialized nations. Trials have been set-up using Nano zero-valent iron and iron oxides and the results have been quite promising. However, there are environmental concerns regarding the impact of nanoparticles on the soil.