The choline chloride case
This year (2000) a dioxin contamination in choline chloride pre-mixtures for feedstuff was detected in Germany. The original choline chloride from a Belgium producer was not contaminated but the Spanish feedstuf premix producer who sold the premix to Germany had added pine sawdust to the product as a carrier. This pine sawdust was heavily contaminated with dioxin (with pentachlorophenol being the source of the dioxin contamination).
The use of pine sawdust and other materials derived from wood treated with wood protection products is prohibited in compound feedstuff within EU and it seems that the enforcement was inadequate. The case is another example on how additives in the feed and food producing process may cause dioxin contamination.