I agree with revdocdrew that, while it may be overblown for adults, it is a definite concern for young children.
My sister is a child psychologist - when she was in graduate school she worked on a study testing the effects of very, very low levels of lead exposure. The government labels any amount over 10 µg/dL as harmful. The study my sister worked on found that even at as low as 3 or 4 µg/dL lead has negative developmental effects - reduced I.Q. - more behavioral issues, etc.
In her educated opinion there is no "safe level" of lead exposure for kids under age 6.
