Table 1.

Potentially toxic elements compared with standard values.

Pollutant	USA regulation for sludge (mg/kg)	South Africa guidelines for sludge management (mg/kg)
As	75	<40
Cd	85	<40
Cr	N/A	<1200
Cu	4300	<1500
Pb	840	<300
Hg	57	<15
Ni	420	<420
Zn	7500	<2800