Why the Dose Matters: Assessing the Health Risk of Exposure to Toxicants

Description:

Each day we are exposed to a myriad of natural and human-made chemicals in our food, drinking water, air, soil, at home or at the workplace—pesticide residues, food additives, drugs, household products—but how can we gauge the human health risk posed by these chemicals? Should we believe the somber headlines that depict a serious threat for humans and the environment, or should we follow the reassuring voices of others who claim that the angst is totally unfounded?

Why the Dose Matters: Assessing the Health Risk of Exposure to Toxicants uses a rational, science-based approach to explain in plain language that a quantitative view is key for understanding and predicting potentially toxic effects of chemicals.

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Preface

In 2021, the Swiss people had to vote on whether to accept or dismiss a referendum initiated by a group of environment-conscious citizens. The initiative’s theme was (I’m paraphrasing): should there be a total ban on the use of all synthetic pesticides across the country? The heated debates on TV, in the media, at the cracker-barrel, and across garden fences are long over, and I really do not want to reopen the case, nor open a new can of worms (by the way, the initiative was rejected). What made me ransack my brains over, though, even long after that political decision was made, were two nagging questions:
First, why do a lot of people believe that everything synthetic is bad and everything natural is good? And second, why do a lot of people believe that a chemical must be toxic just because it is there?

Before the vote, the country had never seen so many self-appointed toxicology pundits, suddenly mushrooming from nowhere. But what was more astonishing was the fact that most of the acrimonious arguments (from both advocates and opponents) were often fueled by emotions, bold assumptions, beliefs, and knowledge from hearsay rather than being based on rational facts and sound knowledge. If you let yourself become entangled in a discussion, you were either reviled as an idealistic green activist or stigmatized as a lobbyist for the pesticide industry. Where was the science? Fallen by the wayside?

The science of toxicology is dauntingly complex. Not only because there is a lot of chemistry to grapple with, but also because it involves an understanding of the underlying biology and pathophysiology, pharmacology, environmental sciences, and an insight into risk assessment and risk management. Toxicology clearly is multi-disciplinary, and it must therefore be quite confusing for a non-scientist to keep track of everything and assemble it to the big picture. You can’t blame the laypeople when a discussion gets emotionally charged while the scientific, rational arguments are few and far between.

Part of the blame probably must go to the scientists themselves (I’m one of them)—why do they hide in the ivory tower, behind their hardto-understand publications and scientific meetings, instead of getting the message across to the public in easily understandable language while not distorting the facts? Believe me, it’s not the arrogance of the adepts. It’s mostly a lack of time, and often the frustration that things have gotten too complicated to be explained in simple terms. (Which isn’t easy; Einstein once said, “Make everything as simple as possible, but not simpler.”)

It was on one of those days that the seed for this book project was planted in my mind.

This book is targeted at interested people who have no special training in the field but who would like to see through the mist of this complex area without having to whack through the thick jungle of scientific jargon (and I promise, you won’t find any chemical equations or molecular structures). It is not a comprehensive reference book (there are many outstanding textbooks on toxicology on the market)—instead, it illuminates just a couple of key aspects that I think will help better understand the complex interactions between chemicals and humans.

Finally, I hope this book can convey some of the fascinations that’s inherent in studying science, and I would like to share with the reader some of the passion I feel while further exploring the field of toxicology.

Key Features

Explains the basics of toxicology in easily understandable terms.
Includes numerous examples.
Clears up common misconceptions and dispels myths.
Provides take-home messages for each chapter.
This book is aimed at interested laypeople. It uses numerous examples to illustrate the basic concepts and ensure that the reader will get a better understanding of why not only the hazard but also the overall exposure will determine whether some chemicals pose a serious risk while others are of little or negligible concern.

Table of contents :

Cover
Half Title
Title Page
Copyright Page
Dedication
Disclaimer
Contents
List of Figures and Tables
Preface
About the Author
Chapter 1: Introduction
Part I: The Concepts: Hazard and Exposure
Chapter 2: What Does “Toxic” Mean?
Pegging a Chemical a Priori as Bad?
Of Industrial Toxicants, Plant Toxins, Magic Poisons, and Snake Venoms
Potency
Is It Safe? On Hazard and Risk
Chapter 3: Paracelsus Reloaded: The Dose Concept
From Master of Alchemy to Founder of Toxicology
A Novel Approach
The Dose Makes the Poison
The Dose-Response
The Dose Does Not Always Reach Its Target
Chapter 4: Exposure: The Key Determinant in Risk Assessment
What Does “Exposure” Mean?
Different Ports of Entry
Checkpoint Liver
How Much, How Often, for How Long?
Exposure Determines the Risk
A Ubiquitous Metal
Chapter 5: Natural and Synthetic Chemicals
Why That Chemophobia?
Natural Versus Synthetic
Natural Medicines
Of Natural and Organic Pesticides
High-Hazard Natural Toxins
Chapter 6: What Our Body Does to a Chemical
Toxicokinetics
Cellular Transport Systems for Chemicals
Paraquat—A Hazardous Pesticide That Hijacks a Carrier in the Lung
The Liver as the Major Metabolic Organ
Gut Bacteria—More Than Just Quiet Coresidents
The Kidney as the Major Excretory Organ
Hard-to-Get-Rid-of Chemicals
Chapter 7: What a Chemical Does to Our Body
Toxicodynamics
Targeting Nerve Cell Function
Disrupting the Endocrine System
Cell Death—By Accident or Suicide
Cancer
Chapter 8: Defense Shields
Standing Troops, Reserves, and Help from Outside
Trapping Chemicals Before They Hit
Oxidant Stress, Radicals, and Antioxidants
Stress Is Not Always Bad
Refusing Unwanted Chemicals Admittance to Cells
Antidotes
Chapter 9: Correlation and Causality
Does Drinking from a Plastic Bottle Cause Cardiovascular Disease?
Is a Correlation Enough to Make a Strong Case?
Do Storks Deliver Babies?
Plasticizers and Sex Hormones
The Search for Causality
Can Phthalates Cause Cells to Store Fat?
Part II: The Chemicals
Chapter 10: Pesticides: KillLLers with a License
Insidious Threat or Benefit for Humankind?
Pesticide Basics
Glyphosate: The Commotion
Glyphosate: The Facts
Glyphosate: The Cancer Controversy
Does Glyphosate End Up on Our Food?
Chapter 11: Toxic Food
Ingredients, Additives, and Contaminants
Toxic Fries?
Just My Cup of Tea
Invisible and Unavoidable: A Mold Toxin
Trans Fat
Chapter 12: Dietary SupplPPLements: The More the Better?
Boosting Health with Vitamin Supplements?
Green Tea, Red Wine, and Dark Chocolate
Herbal Supplements
Chapter 13: Significant Chemical Risks: Persistent and Widespread
Chemicals That Don’t Make the Headlines (Anymore)
Arsenic
Mercury
Cadmium
Lead
Benzene
Wood Smoke and Air Pollution
Dioxins
Hazardous Pesticides Revisited
Chapter 14: Drugs
Adverse Drug Reactions
The Opioid Crisis
People Are Different—Individual Susceptibility
Part III: The Risk
Chapter 15: Safety Assessment
Can We Predict and Prevent a Toxic Response?
Drug Development
Translation from Mice to Humans?
Non-Clinical Studies
Clinical Trials
First Exposure
Testing of Agrochemicals
Computer Simulations, Omics, and Organs-on-a-Chip
Chapter 16: Acceptable Limits, Tolerance, and Red Lines
Crossing the Line
How Much Is Considered Safe?
Detection Limits for Chemicals
Tainted Water
Recalibrating the Tolerance Limits
Setting Exposure Limits for Data-Poor Chemicals
Chapter 17: Risk Assessment
Risk Perception
Deadly and Avoidable: Fugu
Risk Assessment
Rodent Cancer Bioassays—How Predictive Are They?
Does Carpet Cleaning Cause Cancer?
Risk Management
Chapter 18: Gauging the Risk Against the Benefit
The Benefit Must Outweigh the Risk
Healthy Eating
A Day at the Beach
Chapter 19: Risk CommMMunication
The Daily Dose of Hazardous Headlines, Toxic Information, and Risky Conclusions
Balancing the Information
Part IV: The Future
Chapter 20: Toxicological ChallLLenges
Chemical Medleys and Data-Poor Chemicals
Nanoparticles and Microplastics
Forever Chemicals
Green Toxicology
Chapter 21: Conclusions and Outlook
Mythbusters
Hazard, Exposure, and Risk Resumed
Appendix 1: Units and Concentrations
Appendix 2: Classification of Human Carcinogens as Defined by Iarc
Glossary and Abbreviations
Suggestions for Further Reading
Acknowledgments
Index