Statistical Analysis of Ecotoxicity Studies

John W. Green, Timothy A. Springer, Henrik Holbech

• Publisher: Wiley
• Year: 2018
• Print ISBN:
  9781119088349
• eBook ISBN:
  9781119488811
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

A guide to the issues relevant to the design, analysis, and interpretation of toxicity studies that examine chemicals for use in the environment

Statistical Analysis of Ecotoxicity Studies offers a guide to the design, analysis, and interpretation of a range of experiments that are used to assess the toxicity of chemicals. While the book highlights ecotoxicity studies, the methods presented are applicable to the broad range of toxicity studies. The text contains myriad datasets (from laboratory and field research) that clearly illustrate the book's topics. The datasets reveal the techniques, pitfalls, and precautions derived from these studies.

The text includes information on recently developed methods for the analysis of severity scores and other ordered responses, as well as extensive power studies of competing tests and computer simulation studies of regression models that offer an understanding of the sensitivity (or lack thereof) of various methods and the quality of parameter estimates from regression models. The authors also discuss the regulatory process indicating how test guidelines are developed and review the statistical methodology in current or pending OECD and USEPA ecotoxicity guidelines. This important guide:

• Offers the information needed for the design and analysis to a wide array of ecotoxicity experiments and to the development of international test guidelines used to assess the toxicity of chemicals
• Contains a thorough examination of the statistical issues that arise in toxicity studies, especially ecotoxicity
• Includes an introduction to toxicity experiments and statistical analysis basics
• Includes programs in R and excel
• Covers the analysis of continuous and Quantal data, analysis of data as well as Regulatory Issues
• Presents additional topics (Mesocosm and Microplate experiments, mixtures of chemicals, benchmark dose models, and limit tests) as well as software

Written for directors, scientists, regulators, and technicians, Statistical Analysis of Ecotoxicity Studies provides a sound understanding of the technical and practical issues in designing, analyzing, and interpreting toxicity studies to support or challenge chemicals for use in the environment.

Chapter 1
An Introduction to Toxicity Experiments

This chapter introduces some basic concepts that apply to all chapters. It begins with a discussion of the nature of toxicology or ecotoxicology studies that distinguish them from experiments more generally. Then some basic experimental design issues are discussed, such as types of control groups, replicates and pseudo‐replicates, and units of analysis. The various types of responses that occur are introduced, with pointers to chapters in which methods of statistical analysis of the various types of response are developed. An introduction is given to the use of historical controls and how these studies relate to regulatory risk assessment of chemicals in the environment. Then a hierarchy of statistical models is provided that, in broad terms, defines the statistics used in this field of study and, specifically, in this text. Finally, a topic is introduced that is the cause of considerable tension in ecotoxicology and biological analysis of data in general, namely the difference between biological and statistical significance.

1.1 NATURE AND PURPOSE OF TOXICITY EXPERIMENTS

The purpose of a toxicity experiment is to obtain a quantifiable measure of how toxic a given substance is to a group of organisms or community of organisms. The primary purpose of this book is to describe the design and statistical analysis of laboratory experiments on groups of organisms of a single species exposed to controlled levels of a substance thought to have the potential to produce an adverse effect on the test organisms. Such experiments have the goal of quantifying the level of exposure to the substance that has an adverse effect of biological concern. Some consideration is also given to how information from multiple toxicity experiments on different species can be combined to assess the adverse effect of the test substance on an ecological community. This chapter is intended to provide a general overview of toxicity studies and an introduction to the topics covered in this book.

1.1.1 Designed Experiments Compared to Observational Studies

Historically, the toxicity of chemicals has been studied using experiments performed under carefully controlled conditions in the laboratory and by observation of responses in uncontrolled settings such as the environment. Observational studies that gather information by survey or monitoring have the advantage of providing insight into toxicological responses under real‐world conditions. Such studies are valuable in alerting researchers to potential problems resulting from chemical exposure. However, in surveys and monitoring studies, many uncontrolled factors can affect responses, and exposure of organisms to a chemical of interest (e.g. dose and concentration) usually cannot be estimated accurately. As a result, conclusions concerning the relationship between possible toxicological responses and exposure to the chemical are difficult to establish with certainty.

On the other hand, designed experiments typically control most of the factors that affect response, and dose or exposure concentration can be accurately measured. Designed experiments performed in a laboratory are usually performed at constant temperature with constant exposure to a test substance. Control of test substance exposure and other experimental factors allow the relationship between exposure and response to be modeled.

Exposure to the test substance in these experiments may be: via food or water ingested, air breathed, from contact with the soil or sediment or contact with spray application or spray drift on plants, through gavage or intravenous injection, or by direct application to the skin or eyes. The measure of exposure can be the concentration in the food or water or air, the quantity of chemical per unit of body weight, the quantity of chemical per unit of land area, or the concentration of the chemical in the blood.

Toxicity experiments are generally classified as a...

Table of contents

• Cover
• Table of Contents
• Preface
• Chapter 1: An Introduction to Toxicity Experiments
• Chapter 2: Statistical Analysis Basics
• Chapter 3: Analysis of Continuous Data
• Chapter 4: Analysis of Continuous Data
• Chapter 5: Analysis of Continuous Data with Additional Factors
• Chapter 6: Analysis of Quantal Data
• Chapter 7: Analysis of Quantal Data
• Chapter 8: Analysis of Count Data
• Chapter 9: Analysis of Ordinal Data
• Chapter 10: Time‐to‐Event Data
• Chapter 11: Regulatory Issues
• Chapter 12: Species Sensitivity Distributions
• Chapter 13: Studies with Greater Complexity
• Appendix 1: Dataset
• Appendix 2: Mathematical Framework
• Appendix 3: Tables
• References
• Author Index
• Subject Index
• End User License Agreement