and has been for at least the last century. Part N in a series.
This edition: lead.
Aside from the direct deaths, add in all the hundreds of thousands of lives ruined by violence, both the victims and the criminals (whose crimes were likely in no small part due their exposure). And they knew. NY and NJ had already banned lead additives for public health reasons.
Previous editions: injecting random people with plutonium, Tuskegee, forced sterilization, coerced confessions, forced lobotomies.