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Profiling Research on PFAS in Wildlife: Protocol of a Systematic Evidence Map and Bibliometric Analysis

  • NSW Department of Planning and Environment

Abstract and Figures

Background: Per- and polyfluoroalkyl substances (PFAS) are a large group of manufactured chemicals. Since the beginning of their commercial manufacturing in the 1950s, PFAS haven’t only found their way into numerous industrial and commercial applications, but also into the bloodstream of the majority of the human population, the natural environment and its wildlife. Exposure to high levels of PFAS can create health risks for humans and animals which may exacerbate the effects of other anthropogenic impacts faced by wildlife species. To gain a comprehensive overview of the abundance and distribution of PFAS in wildlife species, and to better understand the risk of PFAS exposure on threatened species and PFAS transfer into human food chains, we will collate the available literature into a systematic evidence map and bibliometric analysis. Methods: We will conduct a comprehensive systematic literature search on Scopus, Web of Science and the ‘grey literature’. For screening purposes, we will use decision trees, scanning title, abstract and keywords first. The next step includes full-text screening performed by two reviewers. We will only consider publications in English, peer-reviewed articles, pre-prints and theses. We will limit our search to 31 PFAS types (based on a previous study). A pilot search on Scopus resulted in ~250 potentially relevant publications. We will scan all publications included in the systematic map for predetermined indicators of quality and potential study-level biases. In addition, we will extract bibliometric records from Scopus and perform network analysis. We will present the results using a narrative summary, tables (database), bar plots and colour-coded maps. Results will be available on a dedicated freely accessible website. Discussion: This study will provide critical insight into the gaps and clusters of the literature with regards to the PFAS concentration in wildlife. Therefore, our study will inform and direct future research efforts to fill the gaps revealed. Systematic review registration:
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Proling Research on PFASin Wildlife: Protocol of a
Systematic Evidence Map and Bibliometric Analysis
Catharina Vendl ( )
University of New South Wales
Matthew Taylor1
The Port Stephens Fisheries Institute: Port Stephens Fisheries Centre
Jennifer Braeunig
The University of Queensland Queensland Alliance for Environmental Health Sciences
Matthew Gibson
School of Computer Science and Engineering, University of New South Wales Sydney
Daniel Hesselson
Centenary Institute
G. Gregory Neely
Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre, Centenary Institute, and
School of Life and Environmental Sciences, University of Sydney
Malgorzata Lagisz
Evolution and Ecology Research Centre and School of Biology, Earth & Environmental Sciences,
University of New South Wales Sydney
Shinichi Nakagawa
Evolution and Ecology Research Centre and School of Biology, Earth & Environmental Sciences,
University of New South Wales Sydney
Keywords: PFAS, PFOS, PFOA, ‘persistent organic pollutants’, ‘systematic map’
License: This work is licensed under a Creative Commons Attribution 4.0 International License.
Read Full License
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Background: Per- and polyuoroalkyl substances (PFAS) are a large group of manufactured chemicals.
Since the beginning of their commercial manufacturing in the 1950s, PFAS haven’t only found their way
into numerous industrial and commercial applications, but also into the bloodstream of the majority of
the human population, the natural environment and its wildlife. Exposure to high levels of PFAS can
create health risks for humans and animals which may exacerbate the effects of other anthropogenic
impacts faced by wildlife species. To gain a comprehensive overview of the abundance and distribution
of PFAS in wildlife species, and to better understand the risk of PFAS exposure on threatened species and
PFAS transfer into human food chains, we will collate the available literature into a systematic evidence
map and bibliometric analysis.
Methods: We will conduct a comprehensive systematic literature search on Scopus, Web of Science and
the ‘grey literature’. For screening purposes, we will use decision trees, scanning title, abstract and
keywords rst. The next step includes full-text screening performed by two reviewers. We will only
consider publications in English, peer-reviewed articles, pre-prints and theses. We will limit our search to
31 PFAS types (based on a previous study). A pilot search on Scopus resulted in ~250 potentially relevant
publications. We will scan all publications included in the systematic map for predetermined indicators of
quality and potential study-level biases. In addition, we will extract bibliometric records from Scopus and
perform network analysis. We will present the results using a narrative summary, tables (database), bar
plots and colour-coded maps. Results will be available on a dedicated freely accessible website.
Discussion: This study will provide critical insight into the gaps and clusters of the literature with regards
to the PFAS concentration in wildlife. Therefore, our study will inform and direct future research efforts to
ll the gaps revealed.
Systematic review registration:
Per- and polyuoroalkyl substances (PFAS, also spelled PFASs) are a group of 5,000 to 10,000 organic
chemicals commonly used in numerous industrial and commercial applications worldwide [1]. PFAS are
exclusively synthetic, and thus do not naturally occur in the environment [2]. They are water and oil
repellent and have a high persistence. These chemical properties have made them favourable additives to
many different products and industrial applications. Some of the best-known and widely distributed of
those are the uoropolymer Teon, the stain-resistant coating Scotchguard and aqueous lm-forming
foam (AFFF) [2–5]. One of the downsides of PFAS is their extreme persistence, high mobility, and
ubiquitous distribution throughout the environment. PFAS accumulate in the environment and bind to
human and animal blood proteins [6–9]. Some studies have also presented evidence for a link between
PFAS exposure and health effects in humans [10] and wildlife [11, 12].
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PFAS include per- and polyuoroalkyl substances. In peruoroalkyl acids (PFAA), every hydrogen atom on
the carbon chain has been replaced by uorine, whereas in the polyuoroalkyl acids this is not the case,
as only some hydrogen atoms have been replaced here.
PFAS can be divided into long-chain and short-chain substances. Peruoroalkyl carboxylic acids (PFCA)
– with seven or more fully uorinated carbon atoms (CnF2n + 1COOH; n  7; e.g., PFOA) – and
peruoroalkane sulfonic acids (PFSA) – with six or more (CnF2n + 1SO3H; n  6; e.g., PFHxS) – are
considered long-chain PFAS and tend to accumulate in biota and the environment more than their short-
chain counterparts (see Table1 for a list and abbreviations of common PFAS) [13–15]. In addition,
PFSAs accumulate to a larger extent than PFCAs of the same peruoroalkyl chain length. This is thought
to be due to their ability to bind to serum proteins more strongly [16, 17].
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Table 1
Types of PFAS included in the systematic map. PFAS are listed in their acidic form.
Name of PFAs
group Abbreviation Full name CAS Registry No.
acids (PFCA)
PFBA Peruorobutanoic/ peruorobutyric acid 375-22-4
PFPeA Peruoro-n-pentanoic acid 2706-90-3
PFHxA Peruorohexanoic acid 307-24-4
PFHpA Peruoroheptanoic acid 375-85-9
PFOA Peruorooctanoic acid 335-67-1
acid 95 % | 335-
acid 95 % | 335-
PFNA Peruorononanoic acid 375-95-1
PFDcA Peruorodecanoic acid 335-76-2
PFUA/ PFUdA Peruoroundecanoic acid 2058-94-8
PFDoA/PFDoDA Peruorododecanoic acid 307-55-1
PFTriDA/ PFTrA Peruorotridecanoic acid 72629-94-8
PFTA/ PFTeDA Peruorotetradecanoic acid 376-06-7
sulfonic acids
PFBS/ PFBuS Peruorobutane sulfonic acid 375-73-5
PFPeS Peruoropentane sulfonic acid 2706-91-4
PFHxS Peruorohexane sulfonic acid 355-46-4
PFHpS Peruoroheptane sulfonic acid 375-92-8
PFOS Peruorooctane sulfonic acid 1763-23-1
PFNS Peruorononane sulfonic acid 68259-12-1
PFDS Peruorodecane sulfonic acid 335-77-3
PFECHS Peruoroethylcyclohexane sulfonic acid 335-24-0
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Name of PFAs
group Abbreviation Full name CAS Registry No.
ADONA 4,8-dioxa-3H-peruorononanoic acid 958445-44-8
ether sulfonic
6:2Cl-PFESA (F-
53B) 6:2 Chlorinated polyuoroalkyl ether
sulfonate 73606-19-6
8:2 Cl-PFESA 8:2 Chlorinated polyuorinated ether
sulfonate 83329-89-9
Naon BP2 Naon Byproduct 2 749836-20-2
polymers Hydro-Eve 2,2,3,3-Tetrauoro-3-((1,1,1,2,3,3-
propanoic acid
PFO4DA Peruoro-3,5,7,9-tetraoxadecanoic acid 39492-90-5
PFO5DoDA Peruoro-3,5,7,9,11-pentaoxadodecanoic
acid 39492-91-6
HFPO-DA (GenX) Hexauoropropylene Oxide (HFPO)
Dimer Acid 13252–13–6
HFPO-TA Hexauoropropylene Oxide (HFPO)
Trimer Acid 13252-14-7
6:2 FTS/FTSA h,1h,2h,2h-Peruorooctane sulfonic
acid 27619-97-2
8:2 FTS/FTSA 2-(Peruorooctyl)ethane-1-sulfonic acid 39108-34-4
While the US-based company DuPont accidentally developed the rst PFAS compound in 1938 (Lyons
1994), the company 3M, also US-based, grew into the biggest PFAS producer worldwide and started the
commercial manufacturing process of PFOA, PFOS and many other PFAS in the 1950s [19]. Since then,
PFOS and PFOA have become the most produced, distributed and researched members of the PFAS
family [20, 21]. One of the main applications of PFAS is in AFFF products which included a wide range of
different PFAS as active ingredients including PFOS, PFOA, and PFHxS. Due to the effectiveness of AFFF
products in controlling hydrocarbon res, these products have been broadly deployed for training or
disaster management across military sites, civilian airports and reghting training centres since the
1970s [22]. In the 1980s, China joined the growing number of PFAS-producing countries [23, 24]. Thus, as
early as 1968 research suggested that PFAS accumulated in the human bloodstream [25]. Ubel et al. [26],
Belisle [27], and Yamamoto et al. [28] eventually conrmed Taves’ [25] suspicion. Nevertheless, it took
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until the early 2000s before a large number of studies left no doubt that PFAS had not only made it into
the human body, but also into wildlife [6], the oceans [29], and drinking water [30]. The unique chemical
properties of PFAS prevented an earlier detection in the environment, as measurements required specic
and particularly sensitive analytical methods that were beyond the capabilities of most laboratories until
recent times [6].
In the early 2000s, it also became evident that PFAS had indeed a compromising effect on human and
animal health [31, 32]. In the light of such ndings, in 2002, the company 3M voluntarily phased out most
of its production of long-chain PFAS substances, including PFHxS, PFOS, PFOA and FOSA [33]. As the
demand for PFAS still existed, countries like China, Russia and India increased their production [34],
whereupon the OECD [35] hypothesized that these countries’ PFAS production might have offset the
phase out by 3M. In addition, the worldwide production of other PFAS, like PFUnDA, that were of lesser
public concern, increased [36]. 3M and DuPont introduced PFBS and GenX as two new short-chain PFAS
to replace PFOA [37] and PFOS [38], in 2003 and in 2009, respectively. In the meantime, national and
international initiatives began attempts to restrict production and use of the most common long-chain
PFAS. Among the most extensive programmes was the 2010/2015 PFOA Stewardship Program, initiated
by the US Environmental Protection Agency in 2006, that aimed to eliminate PFOA emissions and
production by the eight leading US manufacturers by 2015 [39]. Furthermore, the UN Stockholm
Convention on Persistent Organic Pollutants (POPs) was signed by 152 countries in 2000, and vowed to
strictly limit the use of PFOS to certain purposes [33]. However, the list of these exempted purposes
included most of the common usages, such as photoimaging, reghting foams, insect baits, metal
plating and surface treatment of leather [33]. Moreover, the speed of the implementation of the
Stockholm Convention differed signicantly across countries. In 2017, China was the only known
producer of PFOS, despite having ratied the Stockholm Convention [23]. While PFHxS is currently under
review, PFOA was added to the convention as a harmful environmental pollutant to be eliminated by 2019
[23]. Figure1 shows a short timeline of important events in PFAS-related history of production, use and
legal restrictions, since the discovery of these chemicals.
After all, PFAS substances have truly earned their infamous reputation as ‘forever chemicals’. However,
questions remain as to whether conventions and restrictions are actually reducing PFAS burdens in the
humans, animals and the environment, and if so, when this effect will become apparent. In 2018, the UN
Environment Programme declared PFOS, PFOA, PFHxS and PFNA as the most frequently detected PFAS
worldwide [40]. In the same year, Land et al. [41] published a large systematic review on PFAS
concentrations in humans and showed that exposures to PFOS, PFOA and PFHxS, were in decline in
North America and Europe, potentially reecting the impacts of legislated restrictions towards some types
of PFAS. On the other hand, in China people are increasingly exposed to PFAS, like PFOS and PFOA,
which was presumably due to the recent local peak in production [42]. However, PFAS contamination
trends affect not only humans, but also non-human biota. Wildlife is constantly exposed to contaminants
in the natural environment. Thus, PFAS burdens in wildlife are expected to reect those of their habitat,
however there is some uncertainty in these patterns (compared to patterns in humans). Depending on the
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geographical region and species, longitudinal studies have provided conicting reports on trends in PFAS
abundance in wildlife and the natural environment over the past 20years [43–45].
PFAS concentrations in wildlife are also relevant in other ways than just reecting the contamination of
our natural environment. Many wildlife species, particularly sh, are an essential part of the diet of people
in many different cultures [46]. The assessment of PFAS concentrations in such species is therefore of
relevance to public health. Finally, assessing PFAS burdens in wildlife also serves the purpose of
conservation management, especially for those species that have already been impacted by
anthropogenic threats, such as loss of habitat and climate change. Exposure to ubiquitous PFAS in the
environment could be another potential driver of population decline and extinction [11, 12].
We aim to perform a comprehensive overview of the existing state of knowledge on the abundance and
distribution of PFAS in wildlife species and to investigate factors that affect distribution of research
efforts generating such knowledge. Therefore, we will collate the available literature into a systematic
evidence map. The systematic evidence map will not only reveal patterns and relationships in existing
data, but also identify knowledge gaps. Our main research questions will explore ‘when and where the
papers were published’, ‘what the recent trends in publications numbers were’ and ‘what (e.g., types of
PFAS, tissue), where (habitat, location), and when was tested’. With this work, we will create a body of
information to complement the systematic map of Pelch et al. [47], who aimed to synthesise the health
effects of PFAS in people. In addition, following the research weaving approach that combines the
synthesis of evidence and inuence [48], we will investigate the collaboration networks among authors
and countries.
This protocol has been prepared in accordance PRISMA-P [49]. The PRISMA - P checklist is attached as
an additional le 1. We registered the project on (
Eligibility criteria
To be eligible for the inclusion in the systematic evidence map, studies need to fulll the following criteria
(also presented as decision trees A, B & C, Figs.1 & 2): The studies have to be journal articles, pre-prints or
theses, written in English. We do not set any limits regarding the publication year. Furthermore, the papers
should investigate the concentration of one or several of 34 types of PFAS of emerging importance [10,
47]. The included PFAS’ names and synonyms are listed in Table1. The studies’ subjects should be wild
or feral animal species in which PFAS concentrations were measured. Research had to be performed on
individuals that were not kept in captivity and involve whole animals or their parts or products (e.g., eggs,
muscle tissue, blood, feathers, liver). In addition to primary literature, we will also collect secondary
literature that focuses on PFAS concentrations in wildlife, for performing backward and forward reference
searches and for providing context to the included primary studies.
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Information sources
For the systematic evidence map, we will identify the relevant peer-reviewed published literature by
searching the inter-disciplinary broad-coverage electronic databases Scopus and Web of Science. We will
also include grey literature (theses and reports) in our search, using BASE, OpenGrey, Ebsco and the
Australian Policy Observatory, as well as the preprint repositories bioRxiv and OSF. We will also perform
backward and forward reference searches from the key secondary publications on the topic. We will
periodically (every 6 months) update the systematic map until the manuscript is accepted for publication.
Search strategy, study selection and data collection process
Development and piloting
Our search strategy, selection process and data collection process are based on a pilot test. We
performed a pilot search (Table S1) in the Scopus database to develop and evaluate our main search
strings (Table S2) and scope the available literature. We randomly selected 100 bibliometric records from
our pilot search and screened them according to the eligibility criteria. Two people (ML, CV) performed the
pilot screening independently using the online software Rayyan QCRI [50] to facilitate the process. Firstly,
we screened the bibliometric records using title, abstract and keywords of the studies, using decision tree
A (Fig.2). We excluded 55 papers that did not t the initial inclusion criteria. As the second step, we
screened full texts of publications that had passed the initial screening step, using decision trees B and C
(Fig.3). A total of 29 out of an initial 100 papers passed the second screening step. When the decision of
our two reviewers on the inclusion of publications was not unanimous, we discussed and resolved
divergent opinions.
To test the data extraction and coding process for the systematic evidence map, the two reviewers (ML,
CV) extracted relevant data from 20 included full-text papers using questionnaires implemented in Google
Forms. Again, diverging results were discussed and resolved. After the pilot search and data extraction,
we adjusted our search strings, rened the decision trees, and data extraction tables (Tables2 and 3).
Informed by the pilot test, our nal search strategy will involve searching eight databases. Table S2
presents nal search strings formatted according to the requirements of the individual data sources. We
will not use date, language or subject limits in our searches. One reviewer will screen the entire search
results and extract the data, because the pilot screens for the systematic evidence map showed high
consistency between the reviewers (93 % for stage one, 89 % for stage two of the pilot screening process,
and 90 % for data extraction). The second reviewer will cross-check the screening and resolve any
conicts. We will follow the two-step process (rstly, screening of title, abstract and keywords, and
secondly, screening of full-text), as in the pilot screening, using decision trees A, B and C (Figs.2, 3). One
reviewer will also perform data extraction and coding, with the second reviewer cross-checking the data.
For initial data extractions, we will use pre-piloted online questionnaires implemented in Google Forms.
Data management
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We will import all literature search results (bibliometric records) to the reference management software
Zotero (version 5.0.88). We will remove duplicate records using Zotero function ‘Find Duplicates’, based
on study title and authors. Following this, we will export and upload bibliometric records to Rayyan QCRI
[50]. We will also collect full-text studies in Zotero. We will collate the extracted data in three separate
spread sheets (Systematic evidence map: Table2 – rst step; Table3 – second step; Table S3 –
additional data; more details below). We will track the numbers of studies retrieved from our literature
searches, numbers screened, excluded and included in our systematic review. We will present our
workow as a diagram based on the PRISMA owchart [49]. We will make the collected data available to
the public via a dedicated website. Analysis code will be available via GitHub.
Data coding strategy
We will perform data extraction from full-text studies using data extraction forms and data extraction
spreadsheets (Tables2 & 3). We will use the data extraction form presented in Table2 to collate study
bibliometric details and general study design and scope details (the content extracted in Google Form will
be exported into a at table in .csv format). The bibliometric data extracted at this stage will comprise
document title, year of publication, country of research institution of rst author and study funding
sources. The study details will include type of PFAS studied, timeframes of sample collection, scientic
name of the study species, studied habitat, type of animal tissue used for analysis etc. If the required
information is missing in the publication, we will contact the study authors. We will use the data
extraction form presented in Table S3 to collect additional information regarding the study species, such
as conservation status, economical relevance, average weight of adult individuals. This additional table
is required, because this information might not be provided in the actual publication itself, but will be
relevant for the interpretation of the systematic map as a whole. Table S3 also includes the sources the
information can be obtained from. We will rst scan the included publication itself for the required
additional information. If the publication does not provide the required information on the species
characteristics, we will refer to the IUCN Red List [51], the Animal Diversity Web [52] and the AnAge
Database of Animal Ageing and Longevity [53]. Other relevant references for other species-related
information categories (e.g., charismatic species as dened in Albert et al. [54]) are stated in Table S3. We
will use the R package
[55] to provide a unique identier for each study species and to link data
stored in different extraction tables.
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Table 2
Data extraction form, step 1: bibliometric and study data for the systematic evidence map.
Bibliometric information Options of answers
Study ID? Study ID code
Title of paper? Text
Year of publication? Number
Country of research institution of rst
author? Text
Study information Options of answers
Did the authors have a conict of interest? Yes, No, Not stated
Does the study include a statement of
funding? Yes, No
Did the study receive funding from a
governmental institution? Yes, No, Unknown (no funding stated)
Did the study receive funding from an
NGO? Yes, No, Unknown (no funding stated)
Did the study receive funding from the
industry? Yes, No, Unknown (no funding stated)
Does the publication provide a link to the
raw data? Yes, No
Does the publication provide a link to the
analysis code? Yes, No
Is the study primary or secondary
literature? Primary, Secondary
Was the chosen sample site located near a
known source of PFAS? Yes (distinct source near-by, e.g., known spill, factory),
Possibly (diffuse source like large industrialized area
near-by), No
Did the study investigate one or multiple
species? One, Multiple
Were temporal trends investigated? Yes, No
Did the study include measurements of
PFAS only (vs. other pollutants)? Yes, No
Year of sample collection started? Year
Year of sample collection nished? Year
Habitat of study species? Aquatic: marine, estuarine, freshwater;
Terrestrial: terrestrial inland, terrestrial coastal
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Bibliometric information Options of answers
Sex of study specimen? Male, Female, Mixed, Unknown
Developmental stage of study species? Eggs/ early development (e.g., embryo), Juvenile, Adult,
Mixed, Unknown
Did the study investigate functional
aspects (e.g., effects of pollutant burden
on reproduction)?
Yes, No
Biogeographical region of study species? Tropical, Temperate, Polar
Type of PFAS investigated? (34 types, refer to Table1 for details)
Types of tissue of study species? Liver, Fatty tissue, Feathers, Eggs, Muscle, Bile, Kidney,
Blood, Whole body homogenate, Other
Scientic names of all study species? Text
General comments/notes? Text
Study quality assessment
We will check all publications included in the systematic map for the statement of the following
information: conict of interest, funding sources and availability of raw data and analysis code, if
relevant. This information could be indicative of study quality and potential study-level biases [56, 57], is
easy to extract and comparable across different study types and designs. The sections for related data
extraction are included in Table2. These extracted variables representing study-level risk of bias will be
included in the systematic map results.
Data mapping method
To present the extracted data, we will use a combination of tables, plots (e.g., for research questions like
’year of publication’, ‘year of sample collection, ‘conservation status (IUCN) of wildlife species’), and
colour-coded maps (e.g., for ‘geographical origin of rst author’, ‘biogeographical regions of tested
wildlife species’; as used in Mangano et al. [58]. We will make the systematic map publicly available on a
dedicated freely accessible website.
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Table 3
Data extraction form, step 2: additional information for the systematic evidence map.
General information on study species Options of answers
Lay name of study species? Text
Taxonomy of study species (class)? Text (e.g., Mammalia, Aves, Actinopterygii)
Conservation status of study species
(according to IUCN Red List of
Threatened Species, 2020)?
Not evaluated, Data decient, Least concern, Near
threatened, Vulnerable, Endangered, Critically
endangered, Extinct in the wild, Extinct
Dietary class of study species? Omnivore, Carnivore, Piscivore, Herbivore
Weight (average of male and female) of
study species in g? Number
Does study species belong to one of the
20 highly charismatic species (according
to Albert et al. [54]?
Yes, No
Economically relevant wildlife species
(e.g., human consumption)? Yes, No
General comments/notes? Text
Data synthesis criteria & Summary measures
We will provide a narrative summary of the systematic evidence map featuring PFAS ndings, especially
in relation to major events in the history of PFAS (introduction of new types, bans and regulations etc.)
(Fig.1). We will discuss the main ndings of the systematic map by pointing out trends, gaps and gluts.
For instance, we will elaborate on trends regarding the countries of aliation of the publications’ rst
authors, providing insight into which countries demonstrate most research activity investigating the issue
of PFAS exposure in wildlife. Furthermore, we will discuss which geographical regions the studies mostly
focus on and where studies are potentially missing (e.g., here we expect large focus on polar regions and
negligence of the tropics). Moreover, we will assess which types of PFAS are most frequently studied and
if the general focus lies more on the exposure to phased-out substances, or whether relevant studies exist
on the new generation of PFAS, such as HFPO-DA (GenX) and HFPO-TA (for details on nomenclature
please refer to Table1). We will also investigate the collaboration networks across authors and countries
using information automatically extracted from Scopus bibliometrics records of the included studies for
which full Scopus records exist. We will process these bibliometric records and perform network analyses
R package [60].
The risk of exposure to high levels of per- and polyuoroalkyl substances of humans, domestic animals,
wildlife and the environment is a major concern worldwide [30, 31]. The use of PFAS and subsequent
pollution has been ongoing since the mid-20th century [19]. However, the revelation that action should be
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taken only recently became apparent to legislative bodies and the public eye [33, 39]. Since then, a large
number of research studies has been conducted to trace the extent of PFAS exposure and its
consequences [30, 31]. Wildlife species worldwide are facing a multitude of anthropogenic threats which
has led to a wave of extinction and population decline [61, 62]. PFAS exposure adds an additional risk
factor to the current situation that should therefore be closely monitored and controlled to keep its
consequences at bay [11, 12]. In addition, PFAS in wildlife poses a threat to public health as it enables
PFAS to enter the human food chain [63, 64].
The aim of our systematic map and bibliometric analysis is to give a critical overview of those studies
performed on the PFAS concentrations in wildlife. Therefore, this study will provide guidance and
orientation for further research efforts that aim to close existing knowledge gaps in this important eld.
Ethics approval and consent to participate
Not applicable
Consent for publication
Not applicable
Availability of data and materials
All materials are available within this protocol. During the review, all materials will be made available in a
publicly accessible repository at the Open Science Framework.
Competing interests
The authors declare that they have no competing interests.
National Health and Medical Research Council (NHMRC) Targeted Research Grant (APP1185002)
awarded to Neely, Nakagawa and Hesselson.
Authors' contributions
CRediT authorship contribution statement:
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CV: Conceptualization, Formal analysis, Methodology, Writing - original draft, Creating of website; MT:
Conceptualization, Methodology, Writing - review & editing; JB: Methodology, Writing - review & editing;
MG: Writing - review & editing, Creating of website; DH: Writing - review & editing; GN: Writing - review &
editing; ML: Conceptualization, Formal analysis, Methodology, Writing - review & editing, Supervision,
Creating of website; SN: Conceptualization, Formal analysis, Methodology, Writing - review & editing,
Supervision, Funding. CV, ML & SN will be the guarantors of the review.
We acknowledge support to SN from the Faculty of Science and the oce of Deputy Vice-chancellor of
Research, UNSW, Sydney. The Queensland Alliance for Environmental Health Sciences (QAEHS), The
University of Queensland, gratefully acknowledges the nancial support of Queensland Health.
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Figure 1
Short historic timeline of selected PFAS-related events including introduction, usage and legal restrictions.
Legend: References: 1 – Lyons (1994), 2 – 3M Company (2020), 3 – Taves (1968), 4 – Australian
Department of Defence (2020), 5 – Ubel et al. (1980), 6 – Belisle (1981), 7 – Yamamoto et al. (1989), 8 –
Giesy and Kannan (2001), 9 – Yamashita et al. (2005), 10 – Exner et al. (2006), 11 – OECD (2002), 12 –
Hekster et al. (2003), 13 – Martin et al. (2010), 14 – Olsen et al. (2007), 15 – Ahearn (2019), 16 – EPA
(2020), 17 – UN Environment (2018), 18 – Worldbank (2017a)
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Figure 2
Decision Tree A for initial screening of bibliometric records. Legend: Inclusion criteria for screening title,
abstract and keywords of the papers.
Page 21/22
Figure 3
Decision Trees B & C for screening of full-text studies. Legend: Inclusion criteria for screening full-text of
studies that passed Decision tree A (Figure 2).
Supplementary Files
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Full-text available
Background Systematic reviews, which assess the risk of bias in included studies, are increasingly used to develop environmental hazard assessments and public health guidelines. These research areas typically rely on evidence from human observational studies of exposures, yet there are currently no universally accepted standards for assessing risk of bias in such studies. The risk of bias in non-randomised studies of exposures (ROBINS-E) tool has been developed by building upon tools for risk of bias assessment of randomised trials, diagnostic test accuracy studies and observational studies of interventions. This paper reports our experience with the application of the ROBINS-E tool. Methods We applied ROBINS-E to 74 exposure studies (60 cohort studies, 14 case-control studies) in 3 areas: environmental risk, dietary exposure and drug harm. All investigators provided written feedback, and we documented verbal discussion of the tool. We inductively and iteratively classified the feedback into 7 themes based on commonalities and differences until all the feedback was accounted for in the themes. We present a description of each theme. Results We identified practical concerns with the premise that ROBINS-E is a structured comparison of the observational study being rated to the ‘ideal’ randomised controlled trial. ROBINS-E assesses 7 domains of bias, but relevant questions related to some critical sources of bias, such as exposure and funding source, are not assessed. ROBINS-E fails to discriminate between studies with a single risk of bias or multiple risks of bias. ROBINS-E is severely limited at determining whether confounders will bias study outcomes. The construct of co-exposures was difficult to distinguish from confounders. Applying ROBINS-E was time-consuming and confusing. Conclusions Our experience suggests that the ROBINS-E tool does not meet the need for an international standard for evaluating human observational studies for questions of harm relevant to public and environmental health. We propose that a simpler tool, based on empirical evidence of bias, would provide accurate measures of risk of bias and is more likely to meet the needs of the environmental and public health community.
Full-text available
Charisma is a term commonly used in conservation biology to describe species. However, as the term “charismatic species” has never been properly defined, it needs to be better characterized to fully meet its potential in conservation biology. To provide a more complete depiction, we collected information from four different sources to define the species currently considered to be the most charismatic and to understand what they represent to the Western public. First, we asked respondents of two separate surveys to identify the 10 animal species that they considered to be the most charismatic and associate them with one to six traits: Rare, Endangered, Beautiful, Cute, Impressive, and Dangerous. We then identified the wild animals featured on the website homepages of the zoos situated in the world’s 100 largest cities as well as on the film posters of all Disney and Pixar films, assuming in both cases that the most charismatic species were generally chosen to attract viewers. By combining the four approaches, we set up a ranked list of the 20 most charismatic animals. The majority are large exotic, terrestrial mammals. These species were deemed charismatic, mainly because they were regarded as beautiful, impressive, or endangered, although no particular trait was discriminated, and species were heterogeneously associated with most of the traits. The main social characteristics of respondents did not have a significant effect on their choices. These results provide a concrete list of the most charismatic species and offer insights into the Western public’s perception of charismatic species, both of which could be helpful to target new species for conservation campaigns.
Full-text available
Background There is a concern that continued emissions of man-made per- and polyfluoroalkyl substances (PFASs) may cause environmental and human health effects. Now widespread in human populations and in the environment, several PFASs are also present in remote regions of the world, but the environmental transport and fate of PFASs are not well understood. Phasing out the manufacture of some types of PFASs started in 2000 and further regulatory and voluntary actions have followed. The objective of this review is to understand the effects of these actions on global scale PFAS concentrations. Methods Searches for primary research studies reporting on temporal variations of PFAS concentrations were performed in bibliographic databases, on the internet, through stakeholder contacts and in review bibliographies. No time, document type, language or geographical constraints were applied in the searches. Relevant subjects included human and environmental samples. Two authors screened all retrieved articles. Dual screening of 10% of the articles was performed at title/abstract and full-text levels by all authors. Kappa tests were used to test consistency. Relevant articles were critically appraised by four reviewers, with double checking of 20% of the articles by a second reviewer. Meta-analysis of included temporal trends was considered but judged to not be appropriate. The trends were therefore discussed in a narrative synthesis. Results Available evidence suggests that human concentrations of perfluorooctane sulfonate (PFOS), perfluorodecane sulfonate (PFDS), and perfluorooctanoic acid (PFOA) generally are declining, while previously increasing concentrations of perfluorohexane sulfonate (PFHxS) have begun to level off. Rapid declines for PFOS-precursors (e.g. perfluorooctane sulfonamide, FOSA) have also been consistently observed in human studies. In contrast, limited data indicate that human concentrations of PFOS and PFOA are increasing in China where the production of these substances has increased. Human concentrations of longer-chained perfluoroalkyl carboxylic acids (PFCAs) with 9–14 carbon atoms are generally increasing or show insignificant trends with too low power to detect a trend. For abiotic and biological environmental samples there are no clear patterns of declining trends. Most substances show mixed results, and a majority of the trends are insignificant with low power to detect a trend. Conclusions For electrochemically derived PFASs, including PFOS and PFOA, most human studies in North America and Europe show consistent statistically significant declines. This contrasts with findings in wildlife and in abiotic environmental samples, suggesting that declining PFOS, PFOS-precursor and PFOA concentrations in humans likely resulted from removal of certain PFASs from commercial products including paper and board used in food packaging. Increasing concentrations of long-chain PFCAs in most matrices, and in most regions, is likely due to increased use of alternative PFASs. Continued temporal trend monitoring in the environment with well-designed studies with high statistical power are necessary to evaluate the effectiveness of past and continuing regulatory mitigation measures. For humans, more temporal trend studies are needed in regions where manufacturing is most intense, as the one human study available in China is much different than in North America or Europe.
Full-text available
More than 3000 per-and polyfluoroalkyl substances (PFASs) are, or have been, on the global market, yet most research and regulation continues to focus on a limited selection of rather well-known long-chain PFASs, particularly perfluorooctanesulfonate (PFOS), per-fluorooctanoic acid (PFOA) and their precursors. Continuing to overlook the vast majority of other PFASs is a major concern for society. We provide recommendations for how to proceed with research and cooperation to tackle the vast number of PFASs on the market and in the environment.
The white-tailed eagle (Haliaeetus albicilla) in Scandinavia has suffered from impaired reproduction due to high exposure to industrial pollution between the 1960s and 1980s. While population numbers are rising again, new contaminants, such as per- and polyfluoroalkyl substances (PFAS), are increasingly found in high trophic avifauna and are of concern to potentially impact once again population health. In the present study, we examined PFAS levels in plasma of white-tailed eagle nestlings from northern Norway over the last decade (2008-2017). While PFOA and PFNA exposure did not follow a significant time trend, PFOS and PFHxS concentrations decreased over time, and ≥C11 perfluorinated carboxylic acids only seem to level-off during the last four years. This may in fact be the first evidence for a change in the trend for some of these compounds. Furthermore, since several PFAS are expected to be highly present in aqueous film forming foams used at airports, we also investigate the potential of the two main airports in the region to act as hotspots for PFAS. Our results indeed show decreasing exposure to PFOA with distance to the airports. Altogether, our results seem to show that legislation actions are effective, continued concern for PFAS exposure of high trophic wildlife is still warranted, even in the northern environment.
Background Per- and polyfluoroalkyl substances (PFAS) confer waterproof, greaseproof, and non-stick properties when added to consumer products. They are also used for industrial purposes including in aqueous film forming foams for firefighting. PFAS are ubiquitous in the environment, are widely detected in human biomonitoring studies, and are of growing regulatory concern across federal, state, and local governments. Regulators, scientists, and citizens need to stay informed on the growing health and toxicology literature related to PFAS. Objectives The goal of this systematic evidence map is to identify and organize the available health and toxicology related literature on a set of 29 PFAS of emerging and growing concern. Search and study eligibility We will search the electronic database PubMed for health or toxicological studies on 29 PFAS of emerging concern. Eligible studies must contain primary research investigating the link between one or more of the PFAS of interest and a health effect, toxicological, or biological mechanistic endpoint. Study appraisal and synthesis methods Title and abstract screening and full text review will require a single reviewer for inclusion to the next level and two independent reviewers for exclusion. Study quality will not be conducted for this evidence mapping. Study characteristics will be extracted and coded from the included studies and checked for accuracy by a second reviewer. The extracted and coded information will be visualized in a publicly available, interactive database hosted on Tableau Public. Results of the evidence mapping will be published in a narrative summary.
Per- and poly-fluorinated alkyl substances (PFASs, including perfluoroakyl acids [PFAAs]) have been used in a range of applications, and are widely distributed throughout the environment including environmental media in aquatic systems. Recent literature provides multiple reports of these compounds in a range of aquatic species, but temporal and spatial variability in tissue concentrations is rarely assessed in a rigorous way. Using an important fishery species of representative biology as a case study (Eastern School Prawn, Metapenaeus macleayi), temporal (month-to-month, and year-to-year) and spatial (intra-estuarine and oceanic) variability in PFAAs concentrations was assessed alongside potential contributing factors. Perfluorooctane sulfonate (PFOS) was the dominant PFAA detected, and there was significant spatial variation in concentration driven primarily by distance to major point sources. There was also substantial variation in PFOS among months, likely driven by behavioural physiological or ecological factors. Importantly, muscle tissue concentrations were unrelated to surface water inputs of PFAAs into the estuary. A numerical model linking prawn migration data with concentrations in the estuarine nursery accurately predicted PFOS concentrations in adjacent oceanic trawling grounds. The results demonstrate the magnitude of temporal and spatial variation in PFAA concentrations, which has implications for assessing PFAA exposure risk through seafood consumption for free-ranging aquatic animals.
An exponential increase in scientific publications requires informative and integrative reviews to provide a detailed synthesis of a particular research field, and this has resulted in the emergence of novel methods for synthesizing heterogeneous research. Research weaving provides a novel framework that combines bibliometrics and systematic mapping to inform the development of a field, the influence of research papers and their interconnections, and to visualize content across and within publications. Research weaving has the potential to provide a more efficient, in-depth, and broad synthesis of a research field, to identify research biases, gaps, and limitations. Such insights have the potential to inform ecological and environmental policy and communicate research findings to the general public in more effective ways then are typically done in current research syntheses. We propose a new framework for research synthesis of both evidence and influence, named research weaving. It summarizes and visualizes information content, history, and networks among a collection of documents on any given topic. Research weaving achieves this feat by combining the power of two methods: systematic mapping and bibliometrics. Systematic mapping provides a snapshot of the current state of knowledge, identifying areas needing more research attention and those ready for full synthesis. Bibliometrics enables researchers to see how pieces of evidence are connected, revealing the structure and development of a field. We explain how researchers can use some or all of these tools to gain a deeper, more nuanced understanding of the scientific literature.