An assessment of health and environmental risks of trace elements and toxic organics in land-applied municipal solid waste compost

This study applied the risk assessment methodology developed by USEPA for e stablishing regulatory contaminant limits and loading rates for municipal b iosolids to MSW compost. Literature data on trace element and organics comp osition of MSW compost were evaluated relative to levels of the same compou nds in biosolids. In addition, data from several laboratory, greenhouse, an d field studies with MSW compost were used to determine parameter values fo r 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) concen tration Limit. Trace organics concentrations in MSW compost are low compare d to those in biosolids with the exception of phthalate esters. Degradation , leaching and plant uptake studies with selected organics added to MSW pri or 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 leve ls. Concentrations of organics in MSW compost are low compared to the risk levels, and thus regulation is not warranted based on risk. Trace element b ioavailability was similar or lower in MSW compost as in biosolids. Conside ring this and the likelihood that MSW compost will not be used extensively in general agriculture (primarily used by home gardeners or for specialty c rops, and for horticultural applications), and that the sup ply of MSW comp ost will be no greater than that of biosolids, it appears that safe, risk-b ased trace element concentrations for MSW compost may be as high or higher than those for biosolids. Given that the actual concentrations of trace ele ments in MSW composts are no higher than those in biosolids (with the possi ble exception of Pb), regulatory Limits on trace elements in MSW compost sh ould not affect land application of these materials. A concentration standa rd for B, a phytotoxic trace element often found in much higher concentrati ons in MSW compost than in biosolids is recommended.