Iron oxide is possibly the single most common pigment used in oil and acrylic paints. Powdered aluminum is used in all the silver, gold, and "metallic" colors. While these pigments are not dangerous when used in tubed paint, many artists purchase them separately for mixing their own paints. This is potentially dangerous.
Aluminum powder is a common ingredient in fireworks. If aluminum pigment powder is in the air, and even a slight static discharge occurs nearby (walking across the carpet), there can be an explosion. If aluminum powder and red oxide powder are mixed and ignited, the explosion will be hot enough to melt the iron pigment.
On June 2nd, two students from Georgia Tech were burned severely while working with aluminum powder and iron oxide powder. If you work with these pigments in dry form, it is best to stay far away from flames, and avoid all sources of static electricity.