Assessment of health and environmental risks of trace elements and toxic organics in land-applied municipal solid waste compost
Compost Science and Utilization
DOI of Published Version
This study applied the risk assessment methodology developed by USEPA for establishing regulatory contaminant limits and loading rates for municipal biosolids to MSW compost. Literature data on trace element and organics composition of MSW compost were evaluated relative to levels of the same compounds in biosolids. In addition, data from several laboratory, greenhouse, and field studies with MSW compost were used to determine parameter values for MSW compost for the 503 risk assessment algorithms. Assumptions about MSW compost production and use patterns were used to evaluate impacts on other algorithm parameters. Organics and trace elements in MSW compost were low in most cases, and only Pb exceeded the 503 exceptional quality (EQ) concentration limit. Trace organics concentrations in MSW compost are low compared to those in biosolids with the exception of phthalate esters. Degradation, leaching and plant uptake studies with selected organics added to MSW prior to composting showed that these materials degrade during composting and in soil, do not leach, and are taken up by crops at low but measurable levels. Concentrations of organics in MSW compost are low compared to the risk levels, and thus regulation is not warranted based on risk. Trace element bioavailability was similar or lower in MSW compost as in biosolids. Considering this and the likelihood that MSW compost will not be used extensively in general agriculture (primarily used by home gardeners or for specialty crops, and for horticultural applications), and that the supply of MSW compost will be no greater than that of biosolids, it appears that safe, risk-based trace element concentrations for MSW compost may be as high or higher than those for biosolids. Given that the actual concentrations of trace elements in MSW composts are no higher than those in biosolids (with the possible exception of Pb), regulatory limits on trace elements in MSW compost should not affect land application of these materials. A concentration standard for B, a phytotoxic trace element often found in much higher concentrations in MSW compost than in biosolids is recommended.
Published Article/Book Citation
Compost Science and Utilization, 7:3 (1999) pp.38-53.