Risk assessment for environmental health

Abstract

This comprehensive and easy-to-readtreatment of the various facets, history,and criticisms involved in risk assess-ment for environmental health focuseson tools and approaches used forhumans in an environment involvingpotential chemical hazards. The first part introduces the underlyingprinciples and techniques of the field,and the second examines case studies interms of different risk assessment scenarios. Iwould have preferred a finer division of the book (withchapters in a different sequence). The first three chapters introduce risk assessment and place it in thebroader context of how risk is managed and how risk characterizationsmust be communicated effectively to different stakeholders. Chapter 14describes the history of managing risk by acts passed by the federal andstate governments, as well as the U.S. government system that allows forthese enforcements. Chapter 16 presents the various steps and issuesinvolved in risk communication. The notion of involving the broadercommunity in the process of prioritizing risks from different sources in theenvironment is explained in the chapter on comparative risk assessment(Chapter 8) and illustrated with the help of the Ohio comparative riskproject case study (Chapter 26). The authors of Chapter 15 argue that thecurrent paradigm of risk assessment/management must be revised to mini-mize harm as quickly as possible. Using the precautionary principle a com-pletely proven causal link to risk would be replaced by a search foralternatives when there is a somewhat dependable hint of substantial risk.Chapter 4 describes the principles of toxicokinetics and toxicodynamicsand justifies the steps defined for risk assessment from a toxicologic view-point. In light of the bias of chemical testing for carcinogenicity potential, asection in this chapter is devoted to the current theories of carcinogenesis. Various computational and experimental tools are described inChapters 5, 6, 7, and 13, and their application is demonstrated in thecase studies described in Chapters 17, 20, and 33. Physiologically basedpharmacokinetic (PBPK) models used to model the absorption,distribution, metabolism, and excretion of the chemical of interest aredescribed in Chapter 5, including the models’ uncertainty and variabil-ity. Basic mathematical equations that capture risk assessment notionsare introduced in Chapter 6, along with ways of considering multipleexposures and different routes for the same exposure and Monte Carlomethods to quantify uncertainties in the model predicted responses.Modern molecular measurements involving genes, proteins, andmetabolites are described in Chapter 7. The variability between individ-uals is illustrated by the presence of single nucleotide polymorphismsfor genes governing the metabolism of xenobiotic chemicals. Chapter13 describes the various issues and techniques involved in collectingbiological samples for monitoring the presence of chemicals. Other chapters describe risk assessments that differ from the stan-dard approach: assessment involving microbial or radiological sources,susceptible populations such as children, and chemicals that have anoptimum range of no effect. The history and the current state of regulat-ing the working conditions of workers are also presented, including dis-parities in standards between the workforce and the general community. The book emphasizes the need for risk assessment, the inherentuncertainties in arriving at a quantitative estimate of risk, and the valuejudgments, technology, commerce, and politics that play importantroles in the final enforced risk standard. Also emphasized are multipleroutes of exposure and the need for special attention to risk assessmentsfor susceptible populations such as children.Overall, the book reads less like a standard textbook and more like areference source. Material discussed in one part of the book is again dis-cussed in another part without the addition of anything new. For example,the PBPK model of methylene chloride is discussed in at least three partsof the book in different contexts but the descriptions do not reference theothers. Each chapter, helpfully, begins with a list of summary points andends with questions that require the student to think beyond and to accessresources outside the book. The figure captions could have been moredescriptive, and color would have made some of the figures easier to deci-pher. Finally, for the curious student, some portions of the book are notself-contained and would require reading from additional references. R