More often than desirable, however, the inadequate
disposal of industrial residues can result in severe environmental
problems, which must be properly resolved. Currently, in the
state of São Paulo, Brazil, more than 3500 contaminated sites have
been identified, and at least 400 of these sites are contaminated by
heavy metal addition to soil (CETESB — COMPANHIA DE TECNOLOGIA
DE SANEAMENTO AMBIENTAL, 2005).