Azo dyes and pigments are commonly used to color textiles and plastics. Some of the by-products, such as chlorinated aromatic amines, are toxic and may be potential carcinogens. The European Commission has recently passed directive 76/769EEC, which bans the usage of certain azo dyes for use in any textile or leather product which may come in "direct or prolonged" contact with the skin or mouth. Also, azo dyes and pigments resist biodegradation under aerobic conditions, so they are difficult to remove from an ecosystem.