i think the point of toxicity is a combination of factors. there is the fact that the du becomes a fine dust, which then travels. this then gets into the water. according to the section on it in tom clancy's armoured warfare (not a novel, its non-fiction, a guided tour throught the 3 acr and interviews, its equipment and history), if ingested equally and all of it is ingested, one m829 apfsds could kill 10, 000 people. its use in 1991 in iraq has had a significant impact on cancer levels and birth defects in the areas it was used. im also currently looking for the award winning documentary on the topic, by ard tv, where they conducted interviews and also tests.
when the shooting starts, clearly the best tools are needed for the men and women involved to win. in this i do agree with certain members on this forum. on the other hand, in cases such as iraq, if the objective is a long term iraq, in the interests of iraq, then du can be self-defeating in several respects. one consideration is the affect on us personnel in theatre. one clip i have seen from the aforementioned documentary shows u.s. recovery crews recovering armour the team has just tested and found to be radioactive.
though we have touched on it, i think the primary reason for its use is cost. in a world where cost wouldnt matter, i suspect most nations would employ top-attack atgms (i cant find the Bill per unit cost estimates..anyone know?), and would not need to be du rounds. in practice one cannot forget that you need to have the necessary number of anti armour rounds at all times...you cant wait for the war to start, and then suddenly produce 15,000 top attack atgms...consider the pace of events in south ossetia, for example). cost is one of the primary factors here, as is density ( armour penetration performance, and velocity..note du rounds have higher velocity with less charge..this is also in the link posted previously on the m829a3 if you look closely). KE performance of du is unrivalled to the best of my knowledge.
thus the negative aspects are considerable, though not widely discussed. in the short term these negative aspects are also not the priority. on the pros side are the characteristics mentioned, at a lower cost.