Public Health Risk Assessment and Risk Management for Safe Drinking Water

1 INTRODUCTION

1.1 What is Safe Drinking Water?

1.2 The Nature of Contamination of Water

1.3 How Can Safe Drinking Water Be Ensured?

1.4 Do Aspects of Groundwater Affect Drinking Water Safety?

2 EXPERIENCE WITH DRINKING-WATER CONTAMINATION AFFECTING HUMAN HEALTH

2.1 History and Understanding of Safe Drinking Water

2.2 Chemical Contaminants

2.3 Microbial Pathogens

2.4 Chemical Versus Microbial Risk in Drinking Water

2.4.1 Contaminants in Groundwater

2.4.2 Chemical Contaminants in Groundwater

2.4.3 Microbial Contaminants in Groundwater

3 THE BASIC SCIENCES FOR ASSESSING PUBLIC HEALTH RISKS

3.1 How We Learn What We Believe About Public Health

3.2 Toxicology for Risk Assessment

3.2.1 Understanding Some Fundamental Aspects of Toxicology

3.2.2 Types of Toxicology Studies

3.2.3 Absorption, Distribution, Metabolism and Excretion (ADME)

3.2.4 Threshold and Non-threshold Toxic Agents

3.2.5 Interpreting Toxicology Studies – Weight of Evidence

3.3 Epidemiology for Risk Assessment

3.3.1 Correlation of Outcome with Exposure

3.3.2 Confounding

3.3.3 Bias

3.3.4 Validity and Reliability

3.3.5 Study Design for Supporting Causation

3.3.6 Weighing Epidemiological Evidence for Causation

4 HEALTH RISK ASSESSMENT

4.1 Comparative Human Health Risks and Environmental Health

4.2 Evolution of Environmental/Public Health Risk Assessment

4.3 Overview of Guidance on Environmental Health Risk Assessment

4.3.1 Issue/Problem Definition

4.3.2 Hazard Identification

4.3.3 Dose–Response Assessment

4.3.4 Exposure Assessment

4.3.5 Risk Characterization

4.3.6 Quantitative Microbial Risk Assessment (QMRA)

5 HEALTH RISK MANAGEMENT

5.1 Precautionary Bias of Public Health

5.2 Approaches to Precaution and Practical Limits to Precaution

5.3 Setting Environmental Health Criteria

5.4 Developing Drinking-Water Guidelines and Standards (WHO, EU, USA, Canada, and Australia)

5.4.1 World Health Organization Guidelines for Drinking-Water Quality

5.4.2 United States Safe Drinking Water Act Regulations (US DWA)

5.4.3 Guidelines for Canadian Drinking Water Quality (GCDWQ)

5.4.4 Australian Drinking Water Guidelines (ADWG)

5.4.5 European Union Water Directive

5.4.6 Calculation of Drinking Water Guideline/Standard Concentrations

5.4.7 Threshold of Toxic Concern (TTC)

5.5 Drinking-Water Safety Plans

6 HEALTH RISK PERCEPTION AND CONSEQUENCES

6.1 Misunderstanding Health Risk Evidence and Risk Perception

6.2 Misinformation Versus Reality

6.2.1 Disinfection By-Products and Human Health

6.2.2 Other Drinking Water Health Risk Controversies

6.3 Off-Flavors, Aesthetics, and Risk Perception

6.4 Judgment and Ethical Risk Management

6.4.1 Ethical Principles to Guide Risk Management

6.5 Making More of What We Know

7 CONCLUDING THOUGHTS

7.1 Overview

7.2 Principles, Foundations and Concepts About Health Risk

7.2.1 Risk and Health Risk

7.2.2 Evidence of Causation, Epidemiology, and Toxicology

7.2.3 Exposure Assessment is Essential

7.2.4 Cancer Risk and Thresholds of Dose–Response

7.2.5 Uncertainty and Managing Risk

7.3 Summary

8 EXERCISES

9 REFERENCES

10 BOXES

BOX 1 Drinking Water Guidelines and Standards are Dominated by Chemical Contaminants

Box 2 Chloroform and THMs: A True Story of Regulatory Evolution of DBPS

Box 3 Research Needs for DBP Exposure Assessment Issues (Arbuckle et al., 2002)

11 EXERCISE SOLUTIONS

12 GLOSSARY

13 NOTATIONS

14 ABOUT THE AUTHOR