It sometimes seems as if the list of carcinogenic substances gets longer every day. A substance such as a food additive that's been in common use for years may unexpectedly show signs of being carcinogenic in laboratory experiments. When that happens, the suspected carcinogen will often have to be withdrawn from the market. When a building material like asbestos turns out to be a carcinogen, it may also have to be physically removed from buildings. English has hundreds of other scientific words ending in -genic (such as allergenic), and in almost all of them the ending means "causing".