Environmental fate of persistent biocides and human exposure.

摘要

Approximately 82,000 chemicals are listed in the toxic substances control act (TSCA) inventory today. Among these are a number of polychlorinated aromatic compounds whose usual route of disposal is via flushing into wastewater. Although household use of persistent biocides (PBs) is widespread, the fate of these anthropogenic compounds during wastewater treatment remains largely unknown. Since PBs tend to have significant hydrophobicity, it has been suggested that during sewage treatment, sorption to municipal sludge may be more important than degradation. Land application of sewage sludge containing sequestered PBs therefore may represent a previously unrecognized pathway for environmental dispersal of these compounds and subsequent secondary human exposure.To test this hypothesis, the following specific aims were defined: (i) to perform a literature review and meta-analysis to investigate factors governing the fate of wastewater contaminants during sewage treatment (ii) to perform mass balances for PBs for determining their fate during wastewater treatment (iii) to estimate the mass of PBs disposed of into wastewater and applied with sewage sludge onto agricultural land nationwide and (iv) to investigate human exposure to PBs by determining the internal dose or body burden of select target compounds.A meta-analysis revealed hydrophobicity as the principal compound property governing the fate of PBs and related pharmaceuticals and personal care products during municipal wastewater treatment. Two studies carried out at a major treatment plant in the Mid-Atlantic region revealed that 50 and 76%, respectively, of the mass loading of the PBs triclosan and triclocarban persisted during treatment following sorption to sewage sludge. An extension of these studies to the U.S. national scale confirmed the local findings. Additionally, several PBs were detected for the first time in wastewater and sewage sludge. Nationwide estimates of the mass of triclosan and triclocarban applied onto land as a result of sewage sludge recycling in agriculture were calculated to equal 81,000 kg/yr and 169,000 kg/yr, respectively. Application of a newly developed method for the determination of PB in whole blood yielded some of the first measurements of the body burden in adults and newborns. Overall, this study identified PBs as widespread pollutants detectable in the U.S. environment and, much less frequently, in whole blood of U.S. residents.