to be stabilized in solution by complexes with the digestive enzymes reducing the toxicity of lead therefore requires breaking the complexes between lead and the digestive enzymes this is accomplished in the present invention by means of metals that more strongly complex the digestive enzymes than does lead it has been found that calcium and magnesium ions are particularly effective at reducing the concentrations of lead in the simulated digestion test solutions table 6a this result is unexpected since many metals u2014 including sodium ferric iron ferrous iron and copper u2014 are not effective in reducing concentrations of lead in simulated digestion test solutions table 6b table 6a effect of treatment with various cations on lead concentrations from treated soil in simulated digestion tests simulated digestion test leachate lead concentrations mg l p treated p cl treated soil treatment stomach intestines stomach intestines none 5 25 4 74 4 69 3 63 magnesium added as magnesium hydroxide 1 mg oh 2 4 68 1 59 7 23 3 09 2 5 mg oh 2 3 21 0 30 3 10 0 69 5 mg oh 2 2 31 0 19 1 57 0 20 calcium added as calcium carbonate 1 caco 3 13 4 3 72 6 21 3 05 2 5 caco 3 6 14 0 86 5 86 0 62 5 caco 3 3 90 0 44 2 08 0 11 0039 table 6b effect of treatment with various cations on lead concentrations from treated soil in simulated digestion tests simulated digestion test leachate lead concentrations mg l p treated p cl treated soil treatment stomach intestines stomach intestines none 5 25 4 74 4 69 3 63 sodium added as sodium.