In the 1980s and 1990s governments across Australia outlawed the use of the herbicide 245T. The ban was introduced for one very good reason - 245T contains dioxin, a chemical impurity with the potential to seriously harm people who are exposed to it. But has the dioxin menace been tamed? Four Corners reveals evidence that this potentially deadly chemical compound may still be present in weed control products and that authorities do not routinely test for it.