Causes of impurity can be anything that contaminates a substance, making it impure. Taints are one such cause, which are substances that are added to a material to make it impure. These taints can be either natural or man-made, and can come from a variety of sources, such as air pollution, industrial waste, or even food additives. Taints can also be caused by improper storage or handling of materials, leading to contamination. In any case, taints are a major cause of impurity in many materials.