Today lead-chromate pigments encounter two problems. Current environmental standards require pigmentation systems that are free of heavy metals. The inadequate acid and alkali resistance of inorganic pigments is also problematic because they cannot withstand the increasing "acid rain" in industrialized countries, nor do they resist the alkali pH range of waterborne systems which, out of ecologic considerations, have become the preferred choice today.
For example, in pastel colors the opacity is primarily based on the very good light-scattering properties of the titanium dioxide, which is added to brighten the shade. In dark blue and green shades, on the other hand, it is especially the very good light absorption of the blue and green pigments that is responsible for a very high degree of opacity. For that reason it is possible to produce coatings in both color ranges using lead-free pigment systems.