INGESTION OF SLUDGE APPLIED ORGANIC-CHEMICALS BY ANIMALS

Intake of sludge-borne chemicals is related to the crop and animal man agement systems, the species and physiological status of animals, and the properties of the chemicals. The greatest intake occurs when sludg e is applied to established crops and animals have immediate access. I ntake is reduced when access is delayed to allow losses by weathering and dilution by plant growth, or when sludge is incorporated into soil because vapour transport from soil to plants and lower concentrations at the surface reduce intake via soil ingestion. Animals that consume forage are the most subject to contaminant exposure, which is maximiz ed when pasture is the major component of the diet because soil ingest ion is an additional exposure pathway. Of the many organic contaminant s in sludges, only lipophilic halogenated hydrocarbons accumulate in a nimal tissues and products. Compounds like phthalate esters, PAHs, aci d phenolics, nitrosamines, volatile aromatics, and aromatic surfactant s are metabolized and do not accumulate. Among halogenated hydrocarbon s, compounds with low degrees of halogenation are metabolized and do n ot accumulate, but higher degrees of halogenation block metabolism, an d concentrations in milk and tissue fat may be several-fold greater th an in the diets.