Toxic is defined. Persistent is defined. Bioaccumulative is defined. If a chemical is toxic and either persistent or bioaccumulative, it should be eliminated, based on its intrinsic properties. No risk assessment needed.
Some effects are quite dramatic.
Earlier studies are being re-examined based on new evidence. For example, a recent retrospective risk assessment suggested that dioxin in Lake Ontario may have caused complete reproductive failure in native lake trout populations by the early 1940s. This important fishery has required artificial stocking to this, day, with mixed results. Other cited problems are increased testicular cancer, undescended testis and genital tract disorders. The authors conclude that disorders seen today originated 20 to 40 years ago, during fetal and childhood development.