What value of lead level in blood does the CDC use as a reference level, above which action must be taken? According to the previously referenced news reports, were any of the children in the DC area above that limit?

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).

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