Application Of Systematic Review Methods In An Overall Strategy For Evaluating Low Dose Toxicity From Endocrine Active Chemicals

To safeguard public health, the US Environmental Protection Agency (EPA) must keep abreast of new scientific information and emerging technologies so that it can apply them to regulatory decision-making. For decades the agency has dealt with questions about what animal-testing data to use to make predictions about human health hazards, how to perform dose-response extrapolations, how to identify and protect susceptible subpopulations, and how to address uncertainties. As alternatives to traditional toxicity testing have emerged, the agency has been faced with additional questions about how to incorporate data from such tests into its chemical assessments and whether such tests can replace some traditional testing methods. Endocrine active chemicals (EACs) have raised concerns that traditional toxicity-testing protocols might be inadequate to identify all potential hazards to human health because they have the ability to modulate normal hormone function, and small alterations in hormone concentrations, particularly during sensitive life stages, can have lasting and significant effects. To address concerns about potential human health effects from EACs at low doses, this report develops a strategy to evaluate the evidence for such low-dose effects.

Potential health effects from chemicals that disrupt endocrine function pose an environmental health concern because of their ability to interfere with normal hormone function in human and wildlife populations. The endocrine system regulates biological processes throughout the body and is sensitive to small changes in hormone concentrations. Endocrine-disruptor research has focused primarily on chemicals that affect three hormone pathways that play important roles in reproduction and development - the estrogen, androgen, and thyroid hormone pathways. Some of this research has identified dose-response relationships that have nonmonotonic curves. Nonmonotonic dose-response curves (NMDRs) are of concern because they do not follow the usual assumption made in toxicology that as dose decreases the response also decreases. The existence of NMDRs has been a controversial topic for decades, and there has been considerable debate about their implications for how chemicals are tested and for how risks from such chemicals are assessed. Toxicity tests are designed to identify hazards and to characterize dose-response relationships, so tests are aimed at finding a (high) dose that elicits a response, and dose-response is explored by testing lower doses spaced to identify statistically a no- or lowest-observed-adverse-effect level. The concern for NMDRs is that such studies, as currently designed, might not detect the inflection of the dose-response curve if only a few doses are tested or if the change in inflection occurs below the range of doses tested. Another concern is that some NMDRs are found for biological effects that are not usually evaluated in toxicity tests. If current testing strategies are inadequate to account for NMDRs, changes to risk assessment practices might be necessary. To help address these issues, the U.S. Environmental Protection Agency (EPA) developed a draft State-of-the-Science Evaluation: Nonmonotonic Dose Responses as they Apply to Estrogen, Androgen, and Thyroid Pathways and EPA Testing and Assessment Procedures. EPA asked the National Research Council to conduct an independent review of this evaluation to ensure that it is scientifically sound and of high quality. Review of Environmental Protection Agency's State-of-the-Science Evaluation of Nonmonotonic Dose-Response as they Apply to Endocrine Disrupters evaluates whether EPA's evaluation presents a scientifically sound and high-quality analysis of the literature on NMDRs. This report reviews how well the EPA evaluation described how the assessment was performed, whether consistent methods and criteria were applied in the analysis of different evidence streams, and whether appropriate methods were applied to evaluating the evidence. The report makes recommendations to improve EPA's process and strengthen the evaluation.

This new fifth edition of Information Resources in Toxicology offers a consolidated entry portal for the study, research, and practice of toxicology. Both volumes represents a unique, wide-ranging, curated, international, annotated bibliography, and directory of major resources in toxicology and allied fields such as environmental and occupational health, chemical safety, and risk assessment. The editors and authors are among the leaders of the profession sharing their cumulative wisdom in toxicology’s subdisciplines. This edition keeps pace with the digital world in directing and linking readers to relevant websites and other online tools. Due to the increasing size of the hardcopy publication, the current edition has been divided into two volumes to make it easier to handle and consult. Volume 1: Background, Resources, and Tools, arranged in 5 parts, begins with chapters on the science of toxicology, its history, and informatics framework in Part 1. Part 2 continues with chapters organized by more specific subject such as cancer, clinical toxicology, genetic toxicology, etc. The categorization of chapters by resource format, for example, journals and newsletters, technical reports, organizations constitutes Part 3. Part 4 further considers toxicology’s presence via the Internet, databases, and software tools. Among the miscellaneous topics in the concluding Part 5 are laws and regulations, professional education, grants and funding, and patents. Volume 2: The Global Arena offers contributed chapters focusing on the toxicology contributions of over 40 countries, followed by a glossary of toxicological terms and an appendix of popular quotations related to the field. The book, offered in both print and electronic formats, is carefully structured, indexed, and cross-referenced to enable users to easily find answers to their questions or serendipitously locate useful knowledge they were not originally aware they needed. Among the many timely topics receiving increased emphasis are disaster preparedness, nanotechnology, -omics, risk assessment, societal implications such as ethics and the precautionary principle, climate change, and children’s environmental health. Introductory chapters provide a backdrop to the science of toxicology, its history, the origin and status of toxicoinformatics, and starting points for identifying resources Offers an extensive array of chapters organized by subject, each highlighting resources such as journals, databases,organizations, and review articles Includes chapters with an emphasis on format such as government reports, general interest publications, blogs, and audiovisuals Explores recent internet trends, web-based databases, and software tools in a section on the online environment Concludes with a miscellany of special topics such as laws and regulations, chemical hazard communication resources, careers and professional education, K-12 resources, funding, poison control centers, and patents Paired with Volume Two, which focuses on global resources, this set offers the most comprehensive compendium of print, digital, and organizational resources in the toxicological sciences with over 120 chapters contributions by experts and leaders in the field

Understanding risk to humans is one of the most important problems in environmental public health. Risk assessment is constantly changing with the advent of new exposure assessment tools, more sophisticated models, and a better understanding of disease processes. Risk assessment is also gaining greater acceptance in the developing world where major environmental problems exist. Developed in partnership with the Association of Schools of Public Health, this comprehensive text offers a thorough survey of risk assessment, management, and communications as these practices apply to public health. Key Features: Provides a practical overview of environmental risk assessment and its application by discussing the process and providing case studies and examples Focuses on tools and approaches used for humans in an environment involving potential chemical hazards Fully updated, the first part introduces the underlying principles and techniques of the field, and the second examines case studies in terms of different risk assessment scenarios Risk assessment is a core requirement for the MPH degree in environmental health Useful “stories” suitable for case studies

In the 1970s, flame retardants began to be added to synthetic materials to meet strict flammability standards. Over the years, diverse flame retardants have been manufactured and used in various products. Some flame retardants have migrated out of the products, and this has led to widespread human exposure and environmental contamination. There also is mounting evidence that many flame retardants are associated with adverse human health effects. As a result, some flame retardants have been banned, restricted, or voluntarily phased out of production and use. This publication develops a scientifically based scoping plan to assess additive, nonpolymeric organohalogen flame retardants as a class for potential chronic health hazards under the Federal Hazardous Substances Act, including cancer, birth defects, and gene mutations.

Toxicological Risk Assessment and Multisystem Health Impacts From Exposure highlights the emerging problems of human and environmental health attributable to cumulative and multiple sources of long-term exposure to environmental toxicants. The book describes the cellular, biological, immunological, endocrinologic, genetic, and epigenetic effects of long-term exposure. It examines how the combined exposure to nanomaterials, metals, pharmaceuticals, multifrequency radiation, dietary mycotoxins, and pesticides accelerates ecotoxicity in humans, animals, plants, and the larger environment. The book goes on to also offer insights into mixture risk assessments, protocols for evaluating the risks, and how this information can serve the regulatory agencies in setting safer exposure limits. The book is a go-to resource for scientists and professionals in the field tackling the current and emerging trends in modern toxicology and risk assessment. • Bridges basic research with clinical, epidemiological, regulatory, and translational research, conveying both an introductory understanding and the latest developments in the field • Evaluates real-life human health risk assessment for long-term exposures to xenobiotic mixtures and the role they play in contributing to chronic disease • Discusses advances in predictive (in silico) toxicology tools and the benefits of using omics technologies in toxicology research

Trichloroethylene (TCE) is a solvent that is used as a degreasing agent, a chemical intermediate in refrigerant manufacture, and a component of spot removers and adhesives. It is produced in mass quantities but creates dangerous vapors and is an environmental contaminant at many industrial and government facilities, including facilities run by the U.S. Department of Defense (DoD). It is important to determine the safe occupational exposure level (OEL) for the solvent in order to protect the health of workers who are exposed to its vapors. However, there are concerns that the current occupational standards insufficiently protect workers from these health threats. Review of DOD's Approach to Deriving an Occupational Exposure Level for Trichloroethylene makes recommendations to improve the DoD's approach to developing an OEL for TCE, strengthen transparency of the process, and improve confidence in the final OEL value. This report reviews the DoD's approach using a literature review, evidence synthesis based on weight of evidence [WOE], point-of-departure derivation, physiologically based pharmacokinetic modeling, extrapolation tools, and explores other elements of the process of deriving an OEL for TCE. It examines scientific approaches to developing exposure values and cancer risk levels, defining the scope of the problem, and improving hazard identification.

The United States Navy has been concerned for some time with protecting its military and civilian personnel from reproductive and developmental hazards in the workplace. As part of its efforts to reduce or eliminate exposure of Naval personnel and their families to reproductive and developmental toxicants, the Navy requested that the National Research Council (NRC) recommend an approach that can be used to evaluate chemicals and physical agents for their potential to cause reproductive and developmental toxicity. The NRC assigned this project to the Committee on Toxicology, which convened the Subcommittee on Reproductive and Developmental Toxicology, to prepare this report. In this report, the subcommittee recommends an approach for evaluating agents for potential reproductive and developmental toxicity and demonstrates how that approach can be used by the Navy. This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC's Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: James Chen (National Center for Toxicological Research), George Daston (Procter and Gamble Company), Jerry Heindel (National Institute of Environmental Health Sciences), Grace Lemasters (University of Cincinnati), and John Young (National Center for Toxicological Research).