Check out this thread [here] (http://www.reddit.com/r/AskHistorians/comments/23o92d/on_cosmos_neil_degrassetyson_said_some_historians/). It should provide a glut of answers as well as links to other threads on the same topic.

The simple answer, however, seems to be that yes, there was an awareness of the toxicity of lead, at least among intellectuals.