Toxic Waste is a perk that's available from the start to all heroes.
Toxic Waste improves your nuke damage by 335, provides ~4 HP/s, and the irradiate aura (which is no longer a talent)
Irradiate aura has been changed since patch 11.3(?). It now provides 30 dps to units within 9 range and stacks with multiple heroes.
The DSL Class Toxins talent adds +9 damage to heroic enemies.
The KBW Class Toxins talent adds +10 damage to psionic enemies.
The Megaman talent adds +2 to Irradiate's range
Each upgrade to irradiate through a power cube pickup increases its damage by 1, to a max of 30.