Nutrient metals
          Macronutrients                 Calcium, magnesium, potassium, 
                                         sodium
          
          Micronutrients                 Chromium, cobalt, copper, 
                                         molybdenum, nickle, selenium
     Possibly essential micronutrients Arsenic, boron, vanadium
     Toxic metals                        Berrylium, cadmium, lead, mercury
     Non toxic, non-essential metals     Aluminium, tin
                                          
        
    Heavy metals
    Heavy metals
      Heavy metals  one of 
                      
       Heavy metals   one of 
       inorganic pollutants
       inorganic pollutants
      Lustrous appearance, good 
       Lustrous appearance, good 
       conductor of electricity & 
       conductor of electricity & 
       enter chemicals reactions 
       enter chemicals reactions 
       as cations
       as cations
      Natural substances, 
       Natural substances, 
       present since the earth’s 
       present since the earth’s 
       formation
       formation
      Become pollutants when 
       Become pollutants when 
       human activities (i.e. 
       human activities (i.e. 
       mining & smelting) release 
       mining & smelting) release 
       them from the rocks
       them from the rocks
                                        
        
    Heavy metals in food
    Heavy metals in food
     Undesirable – Pb, Cd, As, Hg
      Undesirable – Pb, Cd, As, Hg
        high toxicity level
          high toxicity level
        adverse health effect & no benefit for 
          adverse health effect & no benefit for 
         human
         human
     Expected in certain amount – Fe, Cu, 
      Expected in certain amount – Fe, Cu, 
      Zn, Al
      Zn, Al
        medium toxicity level
          medium toxicity level
        have important roles in human 
          have important roles in human 
         metabolism
         metabolism
                                
       
  Table. PTWI and MAC for several heavy metals
      Heavy               PTWI                   Equivalent
       Heavy              PTWI                   Equivalent
      metals
      metals              (mg/kg           (mg/day for 60 kg 
                          (mg/kg            (mg/day for 60 kg 
                            BW)                      adult)
                            BW)                      adult)
     Lead (Pb)              0.025                      0.21
     Lead (Pb)              0.025                      0.21
     Cadmium                0.007                      0.06
     Cadmium                0.007                      0.06
         (Cd)
         (Cd)
    Arsenic (Ar)            0.015                      0.12
    Arsenic (Ar)            0.015                      0.12
   Mercury (Hg)             0.005                     0.043
   Mercury (Hg)             0.005                     0.043
    Copper (Cu)              3.5                        30
    Copper (Cu)              3.5                        30
    Aluminium                  7                        60
     Aluminium                 7                        60
  * PTWI = Provisional Tolerable Weekly Intake
         (Al)
         (Al)
  * According to JECFA (Joint Expert Committee on Food Additives) FAO
      Zinc (Zn)                7                        60
      Zinc (Zn)                7                        60