methyl mercaptan heavy metals are substances of toxicological concern metals such as lead and mercury have long been associated with adverse health effects while the concentrations of these heavy metals are not expected to be great in recycled fiber they will be present nonetheless in the process as set forth in sulfur reduction step 10 of system 2 reduced sulfur reacts with recycled pulp to form essentially insoluble metal sulfide compounds these metal sulfides precipitate from the solution this is because heavy metal sulfides are some of the most insoluble substances known by forming these sulfides these heavy metals are no longer available for reaction and or migration if these substances cannot migrate or react they are no longer substances of toxicological concern in the current process the preferred source for reducing the sulfur is sodium sulfide nash a chemical substance is said to be oxidized when it loses electrons and a substance is reduced when it gains electrons in the present invention the recycled fiber 4 is oxidized with one or more of the following chemicals chlorine chlorine dioxide ozone or elemental oxygen it is to be understood that this is not an all inclusive list the time and temperature of the oxidation treatment will depend on the oxidizing compound used and on the extent and type of contamination exhibited by the recycled fiber 4 the important aspect of the chemical oxidation step 12 is that it mitigates poisonous and deleterious compounds examples of poisonous or deleterious substances mitigated during oxidation reduction include polynuclear compounds such as pyrene pesticides such as aldrin and certain organic pigments the chemical oxidation described above has the additional benefit of removing a.