THE INFLUENCE OF SEWAGE-SLUDGE APPLICATIONS TO AGRICULTURAL LAND ON HUMAN EXPOSURE TO POLYCHLORINATED DIBENZO-P-DIOXINS (PCDDS) AND -FURANS(PCDFS)

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) are organic che micals of suspected extreme toxicity. PCDD/Fs are ubiquitous in the en vironment and relatively enriched in sewage sludges. The deliberate ap plication of sewage sludge to agricultural land can therefore potentia lly increase exposure of the human population to these compounds via t ransfers through the food chain. This paper presents a protocol for as sessing the background human exposure to all seventeen 2,3,7,8-substit uted PCDD/Fs for, which toxic equivalent factors (TEFs) are available. Background daily human exposure in the U.K. to 2,3,7,8-T4CDD and I-TE Q are calculated to be 0.0239 ng and 0.203 ng, respectively. The poten tial increases in crop plant and livestock tissue PCDD/F concentration s, and hence in human exposure, following applications of sewage sludg e to agricultural land are quantified for different sludge application scenarios. The key role of PCDD/F transfer into livestock via ingesti on of sludge adhered to vegetation in determining increases in human e xposure is demonstrated.