Medical experts generally consider a lead of 30  μg Pb per (dL) of blood to pose a significant health risk (Pb = 208). Number of lead atoms per cm3 of blood is

1  dL = 110 L=0.1  L=100  cm3100  cm3  of  blood  has=30  mg  Pb=30 × 10−6 g  Pb= 30  ×  10−6208 mol  Pb=30  ×  10−6 × N0208atoms  Pb                                = 8.6827  ×  1016  atoms   Pb1  cm3  of blood  has  =8.627  ×  10+14  atoms  Pb.