HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Related articles in JEQ Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Schoof, R. A. Articles by Houkal, D. Search for Related Content PubMed PubMed Citation Articles by Schoof, R. A. Articles by Houkal, D. Agricola Articles by Schoof, R. A. Articles by Houkal, D. Related Collections Best Management Practices Ecological Risk Assessment Heavy Metals Organic Compounds Soil Pollution

The Evolving Science of Chemical Risk Assessment for Land-Applied Biosolids

Integral Consulting, Inc., 7900 SE 28th Street, Suite 300, Mercer Island, WA 98040

View larger version (26K): [in a new window]   Fig. 1. Probabilistic exposure assessment (modified from USEPA, 2001). In a probabilistic exposure assessment, distributions for each input parameter (e.g., V1, V2, to Vn) are combined to yield an overall exposure distribution. This distribution is then used to identify the reasonable maximum exposure (RME), which is defined as exposures corresponding to the 90th to 99.9th percentiles. This definition of RME is consistent between deterministic and probabilistic risk assessment.

View larger version (74K): [in a new window]   Fig. 2. Farm family conceptual model (from USEPA, 2002b). Contaminants from biosolids applied to farmland are assumed to migrate from the application area along pathways indicated by arrows and by atmospheric deposition. The farm family is then assumed to contact contaminants either in the application area, in secondary media to which contaminants have migrated, and in biota that have contacted and absorbed the contaminants.

View larger version (46K): [in a new window]   Fig. 3. Media concentration module (modified from USEPA, 2002b). The source partition model used the distribution of reported dioxin concentrations in sewage sludge to predict agricultural soil concentrations, and then used fate and transport and food chain models to estimate distributions of concentrations in other environmental media and in food. (Met data = meteorological data.)

View larger version (41K): [in a new window]   Fig. 4. Ecological conceptual model for agricultural application (from USEPA, 2002b). Contaminants from biosolids applied to farmland are assumed to migrate from the application area along pathways indicated by arrows and by atmospheric deposition. Ecological receptors (see inserts) are then assumed to contact contaminants by the illustrated exposure routes.