Understanding Risk to Wildlife from Exposures to Per- and Polyfluorinated Alkyl Substances (PFAS)

Mark S. Johnson, Michael J. Quinn Jr., Marc A. Williams, Allison M. Narizzano

• Publisher: CRC Press
• Year: 2021
• Print ISBN: 9780367754075
• eBook ISBN: 9781000375886
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Chemistry
• Index: Biological Sciences

Understanding Risk to Wildlife from Exposures to Per- and Polyfluorinated Alkyl Substances (PFAS) provides the most recent summary of toxicity data relevant to mammals, birds, reptiles, and amphibians, and provides values for use in risk assessment applications. Predicting the bioaccumulation of PFAS in terrestrial wildlife (including humans) has proven to be extremely complex. As a group, PFAS act differently than traditional non-ionic organic molecules, where PFAS can break down and reform, whereas some are demonstrated to be extremely persistent. Where sufficient data are provided, this book establishes toxicity reference values (TRVs), which are derived to assist in characterizing environmental sources of contamination and making risk-based decisions.

Features:

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• Provides toxicity reference values (TRVs) for vertebrates (mammals, birds, amphibians) for PFAS, where sufficient data are available, and includes objective supporting background information.

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• Assigns a level of confidence to each TRV to provide the risk assessor with an understanding of the relative uncertainty associated with each value.

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• Presents toxicity data in the formats of scatter diagrams and tables for quick review and assessment.

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• Provides TRVs relevant for screening and decision making

This book serves as a useful aid for risk assessors and managers in those industries that have sites contaminated with PFAS, consultants tasked with evaluating risks at such sites, and staff at regulatory agencies at various governmental levels, who need to know how much contamination is considered safe for wildlife. It will also appeal to researchers with an interest in filling the gaps in the current toxicological data for PFAS exposure.

1  Introduction

Mark S. Johnson

Contents

Derivation of Toxicity Reference Values (TRVs)

Predicting the bioaccumulation of PFAS in terrestrial wildlife (including humans) is proving to be extremely complex. As a group, PFAS act differently from traditional non-ionic organic molecules, where PFAS can breakdown and reform, while some have been demonstrated to be extremely persistent. Toxicokinetic profiles for many PFAS vary widely between species and sexes (Li et al. 2017, Conder et al. 2008). In some cases, their structure resembles that of fatty acids, and they tend to accumulate in the liver rather than partitioning to fats. Given the lack of understanding of how some lipids function on a molecular level, the mechanisms of toxicity of the PFAS effect are poorly understood.

The extent of bioaccumulation may be the best predictor of toxicity. As exposure is sustained, so is the systemic dose to the target site. Largely, females of mammalian species may be more effective at excretion than males, given the larger number of pathways for release (e.g., menstruation, parturition, and lactation). Some species of phylogenetically similar taxa can show marked differences in bioaccumulation (or biological half-lives) and mechanisms for these differences between species are also poorly understood.

PFAS have been found in various tissues of many species of wildlife, including ring-billed gulls (Larus delawarensis), California sea lion (Zalophus californianus), polar bear (Ursus maritimus), Laysan albatross (Phoebastria immutabilis), bottlenose dolphin (Tursiops truncatus), and various fish species, samples of which reveal the global extent of PFAS transport (Giesy and Kannan 2001, Kannan et al. 2002a,b). Thus, PFAS are globally distributed, and are detected in water, air, house dust, soil, sediment, sludge from wastewater treatment plants, and biosolids, and are largely non-degradable.

Many of the more persistent PFAS are no longer being produced by industry, which places greater importance on accurately characterizing the risk associated with potential environmental sources of previous releases. Many jurisdictions have regulations that require the use of risk assessments to determine whether contaminated media should be remediated. Traditionally, exposures to important wildlife species are modeled, or, less often, concentrations are measured and compared with a toxicity benchmark to determine the degree of hazard or risk. Here, we provide the extent of knowledge regarding effects to terrestrial wildlife, defined here as terrestrial mammals, birds, reptiles, and amphibians. Where sufficient data are provided, toxicity reference values (TRVs) are derived to assist in characterizing environmental sources and in making risk-based decisions.

Derivation of Toxicity Reference Values (TRVs)

Derivation of TRVs requires a standardized approach to reviewing pertinent information and using this information to develop a value useful for screening and predicting risk. However, very few accounts published in the scientific literature have been developed with the goal of deriving TRVs. Therefore, clear interpretation of the results, the quality of the methods, and professional judgment regarding the potential adverse effect are key components to translate data to the risk to wildlife species and to derive useful TRVs. Largely, we begin with a clear approach to database query, where dates, databases searched, keywords used, number of hits, number of titles reviewed, number of abstracts retrieved, and publications reviewed are documented.

Controlled laboratory studies, where dose-response relationships are presented, are highly valued; however, other field data and mechanistic information, where biological pathways are conserved, can be used to help corroborate TRV estimates for interspecies extrapolation. When possible, benchmark dose methods are used to fit the data, and points of departures are determined typically at the sub-lethal benchmark dose, with 90% lower confidence levels (BMDL₁₀) for screening values, and the 50% confidence benchmark dose (BMD) level for baseline risk assessments, where decisions are made. Where models do not fit the dose-response data, the no-observed-adverse-effect and lowest-observed-adverse-effect levels, NOAEL and LOAEL, respectively, are used. Uncertainty factors are used according to those described in USACHPPM (2000), when data are incomplete for extrapolation. Hence, a TRV-low and a TRV-high are developed for screening and decision making, respectively. Only data within classes are used (e.g., mammal data for mammals) and only end points that are clearly considered to be adverse are included. Since any adverse effect has the potential to indirectly affect fitness (i.e., by influencing population regulation), we make no judgements (or adjustments) prioritizing toxicological end points where considered to be clearly adverse. Here, we follow the methods found in USACHPPM (2000) and others (Johnson and McAtee 2015, Deck and Johnson 2015).

Taxonomic diversity in toxicity data between species/genera/families and orders provides confidence in the utility of class-specific TRVs, particularly when effects and exposures are relatively consistent. Differences in methods can influence variation in the results and, as such, can be difficult to tease out from species differences. Therefore, each value also has a general level of confidence associated with it, to provide context to the user.

A particular challenge for this PFAS family of chemicals is that the toxicity is dependent, in many ways, upon the kinetics of exposure. Significant differences, particularly in excretion rates, exist between species and genders, and may also exist between age classes. Toxicity is dependent upon internal bioaccumulation of PFAS, that may vary between species, for many of which there are no empirical data. Some physiologically based pharmacokinetic models exist for rodents, primates, and humans for PFOA and PFOS (Loccisano et al. 2013, Chou and Lin 2019). Few other models exist for other species and PFAS, making extrapolation between species difficult.

TRVs are to be used as screening-level benchmarks for wildlife at or in close proximity to contaminated sites. The protocol for performing this assessment are described, in part, in Technical Guide No. 254 – the Standard Practice for Wildlife Toxicity Reference Values (USACHPPM 2000, Johnson and McAtee 2015, Deck and Johnson 2015).

2 Perfluorooctanoic acid (PFOA)

Marc A. Williams

Contents

Perfluorooctanoic Acid and Its Uses

Toxicological Effects of PFOA on Wildlife

Environmental Fate and Transport

Bioaccumulation and Elimination

Mammalian Oral Toxicity

Mammalian Oral Toxicity – Acute

Mammalian Oral Toxicity – Acute: Effects on Hormones

Mammalian Oral Toxicity – Acute: Endocrine Effects

Mammalian Oral Toxicity – Acute: Neurotoxicity

Mammalian Oral Toxicity – Sub-Chronic

Mammalian Oral Toxicity –Sub-Chronic: Developmental Toxicity

Mammalian Oral Toxicity – Subchronic: Endocrine Effects

Mammalian Oral Toxicity – Sub-Chronic: Immunotoxicity

Mammalian Oral Toxicity – Sub-Chronic: Effects on Enzymes

Mammalian Oral Toxicity – Chronic

Mammalian Oral Toxicity – Chronic: Reproduction

Mammalian Oral Toxicity – Chronic: Hormone Effects

Mammalian Oral Toxicity – Chronic: Enzyme Effects

Mammalian Inhalation Toxicity

Mammalian Inhalation Toxicity – Acute

Mammalian Inhalation Toxicity – Sub-Chronic

Dermal Toxicity

Dermal Toxicity – Acute

Dermal Toxicity – Acute: Immunotoxicity

Dermal Toxicity – Sub-Chronic

Mammalian Toxicity – Other

Mammalian Toxicity – Other: Endocrine Disruption

Mammalian Toxicity – Other: Genotoxicity/Mutagenicity

Mammalian Toxicity – Other: Effects on Enzymes

Mammalian Toxicity – Other: Immunotoxicity

Mammalian Toxicity – Other: Estrogenic Response

Summary of Avian Toxicology

Summary of Amphibian Toxicology

Summary of Reptilian Toxicology

Recommended Toxicity Reference Values (TRVs)

Toxicity Reference Values for Mammals

TRVs for Ingestion Exposures for Mammalian Species

TRVs for PFOA Inhalation Exposures for the Class Mammalia

Toxicity Reference Values for Birds

Toxicity Reference Values for Amphibians

Toxicity Reference Values for Reptiles

Important Research Needs

Perfluorooctanoic Acid and Its Uses

A wide range of manufactured per- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA), have found broad utility in an array of consumer goods and industrial products, and are widely recognized as emerging pollutants, with heightened concern at their diverse toxicological and environmental impacts (Buck et al. 2011, Vierke et al. 2012, USEPA 2014, NTN 2015). The extensive use of perfluorinated compounds (PFCs) in surface coatings and protectant formulations since the early 1950s was due to their unique chemical properties (Buck et al. 2011).

Toxicological Effects of PFOA on Wildlife

This chapter summarizes the toxicological effects of PFOA on wildlife following exposure to this compound and evaluates the PFOA toxicity data that are used to derive toxicity reference values (TRVs). The TRVs are to be used as screening-level benchmarks for wildlife at or in close proximity to contaminated sites. The protocol for performing this assessment is, in part, described in Technical Guide No. 254 – the Standard Practice for Wildlife Toxicity Reference Values (USACHPPM 2000, Johnson and McAtee 2015, Deck and Johnson 2015).

Environmental Fate and Transport

PFOA is manufactured as a fully fluorinated organic synthetic acid, that is used to synthesize fluoropolymers...

Table of contents

• Cover
• Half-Title
• Title
• Copyright
• Contents
• Foreword
• Preface
• Acknowledgments
• Authors
• Chapter 1 Introduction
• Chapter 2 Perfluorooctanoic acid (PFOA)
• Chapter 3 Perfluorooctane Sulfonate (PFOS)
• Chapter 4 Perfluorohexane Sulfonate (PFHxS)
• Chapter 5 Perfluororoheptanoic Acid (PFHpA)
• Chapter 6 Perfluorononanoic Acid (PFNA)
• Chapter 7 Perfluorobutane Sulfonate (PFBS)
• Chapter 8 6:2 Fluorotelomer Sulfonate (6:2 FTS)
• Chapter 9 Perfluorodecanoic Acid (PFDA)
• References
• Index