ABSTRACT
Inputs of sludge-borne trace elements to agricutural land in the US has been governed since 1979 by Environmental Protection Agency (EPA) regulations and guidelines. In addition to valuable plant nutrients, sewage sludge contains variable concentrations of trace elements and synthetic organic compounds. Phyto-toxicity from sludge-applied metals was no longer believed to be of concern except for high-metal content sludges applied at high loading rates on acid soils. The development of hazard indices and their use in risk assessment is limited by the availability of valid data for the pollutants of concern. In addition to federal regulations, many states imposed limitations on cumulative applications of elements such as Cu, Ni, Zn and Pb. Under the 1979 regulations, only polychlorinated biphenyls (PCBs) were specifically controlled. The research data base on the fate of sludge-borne organics is extremely limited, as is the information on the content of various synthetic organic compounds in sludges.
