Dude, if it's "common sense" (a right wing code word for "I don't know what the **** I'm talking about") then you should be able to easily demonstrate it.
Here, I'll help.
The answer to question one is: There is no safe level for lead exposure.
http://www.tandfonline.com/doi/abs/10.1080/00039896.1975.10666672
Thomas Midgley, since you didn't recognize the reference despite it being very well known to anyone with any knowledge of lead, was the guy who put lead in gas (and poisoned himself in the process) and CFCs in air conditioners. He later, fittingly, managed to kill himself with a robot he designed to roll himself over in bed. Lets just say he had an *abundance* of common sense.