Bioavailability in Environmental Risk Assessment

Since bioavailability can alter health risk estimates by a factor of 10, 100 or more, its importance in risk assessment cannot be underestimated. Presenting the basic principles that govern bioavailability and how it is measured, this very unique and timely book fills a void in the existing literature on toxicology and toxicokinetics. It contains clear and concise discussions on the behavior of environmental contaminants and how they reach the bloodstream in living organisms. It also presents an exhaustive review of measured bioavailability factors for environmental contaminants most frequently encountered at contaminated sites.

Table of Contents:
Introduction Fundamental Concept of Bioavailability Definition of Bioavailability Unaltered Form Systemic Circulation Relationship Between Extent and Rate of Bioavailability Extent of Bioavailability Bioavailability in Health Risk Assessment Biologically Effective Dose Internal Dose and Average Daily Internal Dose External Dose and Average Daily External Dose Summary Mechanism of Absorption Respiratory System Structure and Function Rate-Limiting Processes for Gaseous Phase Contaminants Other Factors Influencing Respiratory Bioavailability for Gases and Vapors Rate-Limiting Processes for Particulate Phase Contaminants Other Factors Influencing Respiratory Bioavailability for Aerosols Gastrointestinal System Structure and Function Rate-Limiting Processes Other Factors Influencing Oral Bioavailability Skin Structure and Function Rate-Limiting Processes Other Factors Influencing Dermal Bioavailability Summary Experimental Methods for Evaluating Bioavailability General in Vivo Methods Measurement of Blood Levels Measurement of the Cumulative Urinary Excretion Mass-Balance Technique Measurement of Toxic Response Specific Methods for the Inhalation Exposure Route Determination of Deposition Fraction Mechanical Clearance Fraction Dissolution Rate In Vitro Methods: Isolated Perfused Lung Specific Methods for the Ingestion Exposure Route Measurement of Fecal Excretion Measurement of Liver Ratio Dissolution Testing Methods Based on the pH Partition Theory Specific Methods for Dermal Exposure Route Surface Disappearance In Vitro Methods: Biological Membrane Models; Artificial Membrane Models Summary Exposure Routes and Bioavailability Factors for Selected Contaminants* Arsenic Cadmium Chromium and Chromium Compounds Copper Mercury Lead 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) Polynuclear Aromatic Hydrocarbons (PAHs) Benzene Toluene Polychlorinated Phenols Phenol Aniline Bioavailability of Xenobiotics from Contaminated Sites Identification of Exposure Routes Reliability and Validity of the Bioavailability Factors Choice of Experimental Methods Analytical Capabilities Species Differences Mixtures and Vehicles Mechanism of Toxicity Chemical Forms Exposure Duration and Frequency Priority Needs for Further Research Considerations for Applying Bioavailability to Health Risk Assessment Metals Organic Xenobiotics Other Application Considerations Risk Management Considerations References Glossary of Terms Index *For each of the contaminants in this section, the following is provided: Exposure Routes and Receptors Toxicokinetics (Following Absorption) Bioavailability (Inhalation, Ingestion, Dermal) Uncertainties Conclusions Recommendations