BEU, Alm.del - 2024-25 - Bilag 223: Til orientering vedlægges en ny videnskabelig artikel om forekomsten af PFAS i blodet hos danske brandfolk, fra beskæftigelsesministeren

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International Journal of Hygiene and Environmental Health xxx

(xxxx)

xxx

Contents lists available at

ScienceDirect

International Journal of Hygiene and Environmental Health

journal homepage:

www.elsevier.com/locate/ijheh

Serum concentrations of per- and polyfluoroalkyl substances (PFAS) among

men from the Danish fire services and Armed Forces

Kajsa Ugelvig Petersen

a,*

, Dorthe Furstrand Lauritzen

, Regitze Sølling Wils

Anne Thoustrup Saber

, Ulla Vogel

, Niels Erik Ebbehøj

, Johnni Hansen

Julie Elbæk Pedersen

, Tina Kold Jensen

, Maria Helena Guerra Andersen

Department of Occupational and Environmental Medicine, Copenhagen University Hospital - Bispebjerg and Frederiksberg, Bispebjerg Bakke 23, 2400, Copenhagen,

NW, Denmark

The National Research Centre for the Working Environment, Lersø Parkall

105, 2100, Copenhagen E, Denmark

The Danish Society for Occupational and Environmental Medicine, Denmark

Danish Cancer Institute, The Danish Cancer Society, Strandboulevarden 49, 2100, Copenhagen E, Denmark

Department of Clinical Pharmacology, Pharmacy and Environmental Medicine, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark

A R T I C L E I N F O

Keywords:

Firefighters

Occupational exposure

Air force

Navy

Military

Cross-sectional

A B S T R A C T

Background:

Per- and polyfluoralkyl substances (PFAS) have been used extensively in firefighting foams with

resulting occupational exposure among firefighters.

Objective:

To examine serum concentrations of PFAS among current and former employed and volunteer fire-

fighters from the Danish fire services and Armed Forces.

Methods:

During 2023–2024, 429 men from the Danish fire services and Armed Forces participated in the study.

They were asked to provide a blood sample and fill in an online questionnaire. Concentrations of 15 PFAS were

measured in serum. Measurements from the general population sampled in 2021 (the ENFORCE study) were used

as reference. Associations between occupational factors and serum PFAS were assessed using multiple linear

regression.

Results:

Participants were from municipal fire services (n

208), governmental fire services (n

59), civilian

airport fire services (n

50), the air force (n

98) and the navy (n

14). Their median age was 50 years and

median year of commencing service was 1999. While serum concentrations of PFAS among most participants

were at level with those of the general population, civilian airport firefighters had higher serum concentrations of

especially perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS) and perfluorooctane

sulfonic acid (PFOS). Age-adjusted geometric means were 1.42 ng/mL for PFHxS, 0.28 ng/mL for PFHpS and

6.92 ng/mL for total PFOS among civilian airport firefighters.

Conclusion:

Higher serum concentrations of PFHxS, PFHpS and PFOS among civilian airport firefighters likely

reflected past occupational exposure to firefighting foam. Findings emphasized the importance of regulatory

measures and substitution.

1. Introduction

They are lurking in all the comforts of our modern lives. The versatile

family of per- and polyfluoroalkyl substances covers more than 9000

individual chemicals found in a wide range of products (The

Interstate

Technology, 2023; Miljøstyrelsen. Kortlægning af brancher, 2016; Na-

tional Institute for Occupational Safety and Health, 2021; Evich et al.,

2022).

Their fluorinated carbon structure yields an appealing combi-

nation of surface-active properties and exceptional stability (The

Danish

Environmental Protection Agency et al., 2015).

As industries and con-

sumers continue to rely on PFAS, concerns for environmental footprints

and health impacts have gained significance. Especially the

non-polymeric PFAS have attracted much scientific and regulatory

attention due to their inevitable bioaccumulation (Hull

et al., 2023).

* Corresponding author. Department of Occupational and Environmental Medicine Bispebjerg and Frederiksberg Hospital University of Copenhagen Bispebjerg

Bakke 23F, 2400, Copenhagen NV, Denmark.

E-mail address:

[email protected]

(K.U. Petersen).

https://doi.org/10.1016/j.ijheh.2025.114559

Received 11 November 2024; Received in revised form 27 January 2025; Accepted 4 March 2025

(

http://creativecommons.org/licenses/by/4.0/

Please cite this article

as:

Kajsa Ugelvig

https://doi.org/10.1016/j.ijheh.2025.114559

Petersen

al.,

International

Journal

Hygiene

and

Environmental

Health,

BEU, Alm.del - 2024-25 - Bilag 223: Til orientering vedlægges en ny videnskabelig artikel om forekomsten af PFAS i blodet hos danske brandfolk, fra beskæftigelsesministeren

K.U. Petersen et al.

International Journal of Hygiene and Environmental Health xxx

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humans, their half-lives for excretion are exceptionally long (5.3 years

for perfluorohexane sulfonic acid (PFHxS), 2.7 years for per-

fluorooctanoic acid (PFOA), and 4.7 years for perfluorooctane sulfonic

acid (PFOS)) (Rosato

et al., 2024).

The most common non-polymeric

PFAS are epigeno- and immunotoxic (Zahm

et al., 2024).

These are

characteristics of carcinogens and PFOA has recently been classified as

carcinogenic to humans

(group 1) by the International Agency for

Research on Cancer (IARC) (Zahm

et al., 2024).

In addition, exposure to

non-polymeric PFAS has been linked to changes in liver and kidney

function, lipid metabolism, reproductive organs along with develop-

mental effects (EFSA

panel on contaminants in the food chain, 2020).

While progress has been made regarding our understanding of PFAS

in various environmental matrices and general populations worldwide,

documentation of occupational exposure remains scarce, and available

measurements cover only a few industries (Lucas

et al., 2022; Par-

is-Davila et al., 2023).

Most frequently, occupational exposure has been

studied in relation to firefighting (Burgess

et al., 2022; Dobraca et al.,

2015; Goodrich et al., 2021; Graber et al., 2021; Jin et al., 2011; Khalil

et al., 2020; Laitinen et al., 2014; Leary et al., 2020; Tefera et al., 2023;

Nilsson et al., 2020, 2022a; Rihackova et al., 2023; Rosenfeld et al.,

2022; Rotander et al., 2015; Shaw et al., 2013; Tao et al., 2008; Trow-

bridge et al., 2020; Purdue et al., 2023; Nematollahi et al., 2023).

Due to

their flame-resistant and water-repellent profile, PFAS have long served

as integral components of both protective equipment and firefighting

foams (Rosenfeld

et al., 2022).

In particular, high concentrations of

PFAS have been used in aqueous film-forming foam (AFFF) (NIRAS,

2021).

Further, fire smoke and dust may also contain PFAS and

contribute as sources of exposure (Rosenfeld

et al., 2022; Tao et al.,

2008; Young et al., 2021).

Exposure may occur during actual fire in-

cidents, training scenarios or activities in the hazardous zones of the

workplace (i.e., decontamination area or apparatus bay). Inhalation is

considered the main exposure route with potential contributions also

from dermal absorption and incidental ingestion (Rosenfeld

et al.,

2022).

Previous studies measuring PFAS in relation to firefighting have

shown striking variations in blood concentrations among employees and

volunteers (Burgess

et al., 2022; Dobraca et al., 2015; Goodrich et al.,

2021; Graber et al., 2021; Jin et al., 2011; Khalil et al., 2020; Laitinen

et al., 2014; Leary et al., 2020; Tefera et al. 2023; Nilsson et al., 2022a;

Rihackova et al., 2023; Rotander et al., 2015; Shaw et al., 2013; Tao

et al., 2008; Trowbridge et al., 2020; Purdue et al., 2023; Nematollahi

et al., 2023).

The contrasts in exposure may largely reflect differences in

use of AFFF and related working conditions (Leary

et al., 2020; Nilsson

et al., 2022a; Rihackova et al., 2023).

Globally, the quantities of AFFF

used by military services far outweigh the amounts spent by civilian fire

services (Rosenfeld

et al., 2022; Ruyle et al., 2023).

Despite the potential

intensity of AFFF use in the military, the majority of existing studies

cover PFAS exposures exclusively among regular firefighters (Burgess

et al., 2022; Dobraca et al., 2015; Goodrich et al., 2021; Graber et al.,

2021; Jin et al., 2011; Khalil et al., 2020; Laitinen et al., 2014; Leary

et al., 2020; Tefera et al., 2023; Rihackova et al., 2023; Rotander et al.,

2015; Shaw et al., 2013; Trowbridge et al., 2020; Nematollahi et al.,

2023).

Thus, the aim of this study was to examine serum concentrations

of non-polymeric PFAS among different types of current and former

employed and volunteer firefighters from both the Danish fire services

and Armed Forces in relation to reference measures from the general

population.

2. Materials and methods

2.1. Setting and study population

In Denmark, rescue and fire management primarily relies on

municipal fire services with potential assistance from the governmental

Danish Emergency Management Agency (DEMA). In addition, specific

hazards require specialized fire services. Thus, airports and air bases

have an aircraft rescue and firefighting (ARFF) response operated by

either a civilian airport fire service or the Royal Danish Air Force

(RDAF). Similarly, the Royal Danish Navy (RDN) contributes to the

management of maritime rescue and firefighting. DEMA, RDAF and RDN

are all a part of the Armed Forces in Denmark.

The study population consisted of current and former employees and

volunteers from 27 municipal fire stations, three governmental emer-

gency management centers, two civilian airport fire stations, three air

force fire stations and two naval stations representing all regions of

Denmark. Initially, we collected records on all staff with exposures

related to firefighting from employers. The number of women affiliated

with the selected workplaces was too limited for meaningful statistical

analyses of occupational exposure to PFAS, and they were, thus,

excluded. Men with a minimum age of 18 years and at least one

employment or volunteer affiliation with a municipal, governmental, or

specialized fire service or response during the years 2000 through 2024

were eligible for participation. We identified 1735 eligible male em-

ployees and volunteers from staff records with 21 records representing

firefighters with additional affiliations at the selected workplaces. To

ensure adequate representation of occupational exposure periods and

durations, we selected 1535 men to be invited based on their period of

employment. Between September 2023 and January 2024, each of these

men were contacted through a secure digital mailbox system, e-Boks,

held by all residents in Denmark. They were invited for at least one study

information meeting at their current or former workplace

(Supplementary

Fig. S1).

Among the 434 men attending an information

meeting, five men were not enrolled in the study due to either inability

to have a blood sample collected, lack of relevant exposure during the

required time interval, or simply declining participation. All of the 429

participating men (participation rate 28%) received thorough oral and

written information about the study prior to their enrollment. Each

participant was required to give a blood sample and fill in an electronic

questionnaire. We forwarded monthly reminders to participants failing

to respond to the questionnaire. Despite these reminders, 40 participants

(9%) provided no questionnaire data. A full overview of the recruitment

process is shown in

Fig. 1.

2.2. Blood sample collection and PFAS analyses

A VACUETTE® Safety blood collection set with holder (Greiner-Bio-

One Gmbh, Kremsmünster, Austria) was used to draw blood from an

antecubital vein. Participants were non-fasting. Following 60 min of

clotting time at room temperature, samples were centrifuged with sub-

sequent separation of serum. Serum was stored in CryoPure® tubes

(Sarstedt, Nümbrecht, Germany) at 80

◦

C until analysis.

Based on previous studies of occupational exposure among fire-

fighters, we prioritized quantification of short- and long-chained per-

fluoroalkyl acids (six sulfonic acids and nine carboxylic acids)(Burgess

et al., 2022; Dobraca et al., 2015; Goodrich et al., 2021; Graber et al.,

2021; Jin et al., 2011; Khalil et al., 2020; Laitinen et al., 2014; Leary

et al., 2020; Tefera et al., 2023; Nilsson et al., 2022a; Rihackova et al.,

2023; Rotander et al., 2015; Tao et al., 2008; Trowbridge et al., 2020;

Purdue et al., 2023; Nematollahi et al., 2023).

The 15 PFAS selected for

quantification were perfluorobutane sulfonic acid (PFBS), per-

fluoropentanoic acid (PFPeA), perfluoropentane sulfonic acid (PFPeS),

perfluorohexanoic acid (PFHxA), PFHxS, perfluoroheptanoic acid

(PFHpA), perfluoroheptane sulfonic acid (PFHpS), PFOA, PFOS, per-

fluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), per-

fluorodecane sulfonic acid (PFDS), perfluoroundecanoic acid (PFUnDA),

perfluorododecanoic acid (PFDoDA), and perfluorotridecanoic acid

(PFTrDA). Total PFOS was calculated as the sum of branched isomers

plus the linear isomer (nPFOS). A serum sample of 150

L was prepared

adding 20

L of an internal standard solution containing 20 ng/mL

carbon-13-labelled PFAS analogues (MPFAC-24ES from Wellington

Laboratories, Guelph, Canada) and 120

L methanol in a polypropylene

tube. Subsequently, the sample was whirl mixed and centrifuged at 21,

BEU, Alm.del - 2024-25 - Bilag 223: Til orientering vedlægges en ny videnskabelig artikel om forekomsten af PFAS i blodet hos danske brandfolk, fra beskæftigelsesministeren

K.U. Petersen et al.

International Journal of Hygiene and Environmental Health xxx

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Fig. 1.

Flowchart of the recruitment of participants from the Danish fire services and Armed Forces; 2023–24.

000 g for 20 min. A volume of 160

L supernatant was transferred to a

new polypropylene tube and added 400

L of formic acid 0.1 M. The

sample was whirl mixed again and 400

L was injected onto an online

solid-phase extraction (SPE) column on a high-pressure liquid chroma-

tography and triple quadrupole mass spectrometry (LC-MS/MS) system

(Haug

et al., 2009; Nielsen et al., 2024).

The LC-MS/MS system con-

sisted of an EQuan MAX ultra-high-pressure liquid chromatograph

(UHPLC) connected to a TSQ Quantiva triple quadrupole mass spec-

trometer using Xcalibur v. 4.5 software (Thermo Fischer Scientific, San

Jose, CA, USA). Serum samples were analyzed along with calibrators,

solvent blanks and quality control (QC) samples (with low and high

concentrations of PFAS). QC samples included serum from a previous

Human Biomonitoring for Europe (HBM4EU) quality assessment pro-

gram and in-house made samples. All QC samples were well within

acceptable ranges and coefficients of variation (CV) ranged between

2.8% and 11.7% (Supplementary

Table S1).

The limits of detection

(LODs) ranged from 0.03 to 0.1 ng/mL (Supplementary

Table S1).

Values below the LOD were assigned the value of the LOD divided by the

square root of two. All analyses were performed at the Department of

Clinical Pharmacology, Pharmacy and Environmental Medicine, Uni-

versity of Southern Denmark. Accuracy and reliability of PFAS analyses

from the laboratory were ensured by regular participation in the German

External Quality Assessment Program (G-EQUAS) organized by the

German Society of Occupational Medicine (The

German external quality

assessment, 2024).

2.3. Questionnaire and covariates

A questionnaire was developed based on the existing literature on

exposure to PFAS among firefighters, knowledge of specific working

conditions in Denmark, and additional factors potentially contributing

to either exposure to or excretion of PFAS (Burgess

et al., 2022; Dobraca

et al., 2015; Goodrich et al., 2021; Graber et al., 2021; Jin et al., 2011;

Khalil et al., 2020; Laitinen et al., 2014; Leary et al., 2020; Tefera et al.,

2023; Nilsson et al., 2020, 2022a; Rihackova et al., 2023; Rosenfeld

et al., 2022; Rotander et al., 2015; Shaw et al., 2013; Tao et al., 2008;

Trowbridge et al., 2020).

Information on occupational history, work

environment, educational level, age, height, weight, ethnicity, blood

donation, health, diet and health behavior was collected in the ques-

tionnaire. The questionnaire was distributed using the secure

browser-based tool, Research Electronic Data Capture (REDCap) under

the Capital Region of Denmark (Harris

et al., 2009).

Using information from the questionnaire, the following covariates

regarding health and health behaviour were constructed: body mass

index (BMI, weight in kg/(height in m)

, continuous), intake of meat

(≥4 days per week;

yes, no),

eggs (≥4 days per week;

yes, no),

dairy

products (≥4 days per week;

yes, no),

fruit (≥4 days per week;

yes, no),

fish and shellfish (weekly;

yes, no),

takeaway (weekly;

yes, no)

and tea

drinking (weekly;

yes, no),

total blood donations (continuous), and co-

morbidity (yes,

no).

Covariates related to occupational exposure

included total foam usage (calculated as years of foam use multiplied by

the frequency of foam use and categorized in tertiles as

low, medium and

high),

dermal foam exposure during training and incidents (never/rarely,

regularly, most times/always),

function as instructor (yes,

no),

storage

management (yes,

no),

and emergency vehicle technician or mechanic

(yes,

no),

and civilian non-firefighting jobs (categorized according to

db07 sector).

2.4. Reference measurements

As a reflection of PFAS serum concentrations in the general popu-

lation in Denmark, we applied measures from samples collected in 2021

through the Danish national cohort study of effectiveness and safety of

SARS-CoV-2 vaccines (ENFORCE) (Staerke

et al., 2022).

ENFORCE

included a total of 6943 participants from all five administrative regions

of Denmark (Staerke

et al., 2022).

We sampled serum from 496 men

(median age 64 years, 5th percentile 43 years and 95th percentile 82

years) receiving the mRNA-1273 vaccine. Serum was collected before

the first vaccination and analyzed for the same PFAS as in our current

study using liquid chromatography triple quadrupole linear ion trap

mass spectrometry (LC/MS/MS, QTRAP 5500, AB Sciex, Framingham,

MA, USA) (Supplementary

Table S2)

(Petersen

et al., 2022).

Analyses

were performed at the Division of Occupational and Environmental

Medicine, Lund University, Sweden. The laboratory participated in the

Erlangen Round Robin inter-laboratory control program and qualified as

a European Human Biomonitoring Initiative (HBM4EU) laboratory for

analyses of PFAS.

2.5. Statistical analyses

All participants were assigned a primary occupational exposure

group (municipal,

governmental, airport, air force and navy)

and employ-

ment type (full-time,

part-time or volunteer)

based on their longest held

employments or volunteer affiliations. The most recent employment or

affiliation was chosen, when durations of time spent were equal between

categories. Initially, we examined the distribution of covariates and

serum concentrations of PFAS among the men according to their pri-

mary occupational exposure groups and employment types. We decided

a priori

to include only PFAS with measured concentrations above the

LOD in samples from at least 40% of the participants in analyses

(Supplementary

Table S1).

Correlations between serum concentrations

of PFHxS, PFHpS, PFOA, PFOS, PFNA, PFDA and PFUnDA were analyzed

using Spearman’s

We calculated age-adjusted geometric means with 95% confidence

intervals for serum concentrations of PFAS among male participants

from the ENFORCE study and the participants from the fire services and

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K.U. Petersen et al.

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Armed Forces according to their primary occupational exposure group

and employment types. In a separate analysis, age-adjusted geometric

means of serum PFAS were calculated exclusively for participants

commencing service from 2011 and onwards, when PFOS was banned

for use in firefighting foam in Denmark (NIRAS,

2021).

Subsequently, we examined potential associations between primary

occupational exposure group and employment type and serum concen-

trations of PFAS using multiple linear regression analyses. The following

covariates were included in the main analyses:

•

Age was calculated as the interval from date of birth to date of

participation and included as a continuous covariate.

•

Years of service was counted for all non-overlapping employments

with the fire services and Armed Forces and categorized based on 10-

year intervals.

•

The longest completed education was categorized according to the

Danish version of the International Classification of Education,

DISCED-15 (v1: 2024) with three main aggregates (short,

medium and

long)

(Statistics

Denmark, 2024; Eurostat - Statistics Explained,

2023).

•

The total number of blood donations was calculated based on in-

formation on years and frequency of donating and included as a

continuous covariate.

These covariates were selected

a priori

based on the existing litera-

ture (Graber

et al., 2021; Rihackova et al., 2023; Rotander et al., 2015;

Richterova et al., 2023).

Bivariate correlations (Spearman’s

0.8) and

variance inflation factors (VIF) were assessed to limit potential issues

with multicollinearity in analyses. We also tested for interactions be-

tween covariates. PFAS concentrations were skewed in their distribu-

tions and a natural log transformation was applied to secure adequate

model fit. Results were back-transformed to ease interpretation. The

adjusted analyses included only the 389 men providing questionnaire

information.

An expanded multiple linear regression model was used to examine

the importance of additional factors both within and outside of the

working environment. We adjusted for the same covariates as in the

main model with the addition of BMI, intake of meat, eggs, dairy

products, fruit, fish and shellfish, takeaway and tea drinking, comor-

bidity, total foam usage, dermal foam exposure, function as instructor,

storage management, and emergency vehicle technician or mechanic,

and jobs outside the fire services and Armed forces. Finally, we repeated

our main analyses with added adjustment for the most influential factors

according to the expanded model.

To ensure adequate anonymity and compliance with national data

protection regulations, all estimates were based on information from at

least five individuals. Statistical analyses were performed using Stata V.

14 (StataCorp, College Station, TX, USA).

2.6. Ethics

The study was conducted in accordance with the principles of the

Table 1

Characteristics of the 429 men from the Danish fire services and Armed Forces, 2023–2024.

Primary occupational exposure group

Total

Participants, n

Age (years), Mdn (P

, P

95%

)

Education

Short, n (%)

Medium, n (%)

Long, n (%)

Body Mass Index, Mdn (P

, P

95%

)

Current tobacco use

, n (%)

Diet

Meat, n (%)

Eggs, n (%)

Dairy products, n (%)

Fruit, n (%)

Fish and shellfish, n (%)

Tea drinking, n (%)

Takeaway, n (%)

Alcohol units per week, Mdn (P

, P

95%

)

Vitamin and/or omega-3 oil supplement, n (%)

Exercise (weekly hours)

, Mdn (P

, P

95%

)

Blood donation ever, n (%)

Cholesterol-lowering medicine, n (%)

Comorbidity

, n (%)

Occupational information

Primary employment type (full-time), n (%)

Year of commencing service, Mdn (P

, P

95%

)

Years of service, Mdn (P

, P

95%

)

Years of foam usage, Mdn (P

, P

95%

)

Functions:

Instructor, n (%)

Storage management, n (%)

Emergency vehicle technician or mechanic, n

(%)

Other job(s)

, n (%)

429

50 (26, 67)

–

26.8 (22.6, 33.6)

73 (19)

–

3 (0, 12)

203 (52)

5 (1, 15)

152 (40)

44 (11)

–

348 (81)

1999 (1979,

2020)

23 (3, 41)

21 (2, 40)

–

27 (7)

31 (8)

182 (47)

Municipal

208

50 (27, 64)

22 (12)

125 (66)

42 (22)

26.6 (22.8, 32.8)

38 (21)

144 (79)

48 (26)

126 (69)

86 (47)

115 (64)

53 (30)

75 (41)

3 (0, 13)

98 (52)

5 (1, 17)

77 (42)

19 (10)

26 (14)

143 (69)

1999 (1983,

2019)

23 (4, 40)

23 (3, 39)

62 (30)

8 (4)

14 (8)

95 (50)

Governmental

38 (22, 62)

≤5

28 (53)

22 (42)

27.4 (21.3, 33.7)

11 (21)

39 (75)

13 (25)

32 (62)

22 (44)

31 (62)

19 (38)

26 (50)

3 (0, 13)

23 (43)

3 (0, 19)

13 (25)

≤5

6 (11)

43 (73)

2009 (1984,

2023)

14 (1, 39)

10 (1, 31)

40 (68)

10 (19)

6 (12)

29 (55)

Airport

52 (38, 67)

9 (20)

29 (66)

6 (14)

26.2 (22.7, 36.4)

5 (12)

34 (81)

16 (38)

29 (69)

20 (48)

31 (78)

11 (28)

16 (38)

4 (0, 12)

22 (50)

5 (1, 12)

17 (40)

5 (10)

8 (18)

50 (100)

1998 (1979,

2021)

24 (2, 42)

21 (6, 37)

28 (56)

≤5

10 (23)

Air force

56 (28, 72)

31 (35)

44 (49)

14 (16)

27.3 (22.2, 33.7)

14 (16)

65 (74)

24 (27)

70 (79)

50 (56)

61 (69)

35 (40)

24 (27)

3 (0, 11)

54 (61)

4 (1, 15)

38 (43)

16 (16)

16 (18)

98 (100)

1992 (1972,

2020)

30 (2, 43)

26 (4, 43)

34 (35)

6 (7)

43 (48)

Navy

49 (35, 58)

–

26.1 (24.3, 31.2)

5 (36)

–

2 (0, 6)

6 (43)

7 (3, 12)

7 (50)

≤5

14 (100)

1996 (1986,

2012)

27 (10, 37)

11 (5, 17)

≥10

≤5

5 (36)

Mdn, Median. Medians and other percentiles are displayed as pseudo-percentiles based on five adjacent values.

Includes cigarette, pipe and e-cigarette smoking and snuff use.

For meat, eggs, dairy products and fruit, consumption is daily or almost daily (≥4 days per week) while intake of fish, tea and takeaway is weekly.

Includes moderate and vigorous physical activity.

Includes cancer, diabetes, inflammatory bowel disease, renal and liver disease, acute myocardial infarction and stroke.

Includes jobs outside the fire services and Armed Forces from 2000 to 2024 categorized according to db07 sector.

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K.U. Petersen et al.

International Journal of Hygiene and Environmental Health xxx

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Declaration of Helsinki. Study approval was obtained from the Capital

Region’s Committee on Health Research Ethics (H-23027326) on June

8, 2023. Further, the study was registered by the Knowledge Center on

Data Protection Compliance under the records of processing regarding

health science research projects within the Capital Region of Denmark

(p-2023-14170) in accordance with regulations from the Danish Data

Protection Agency. The privacy rights of all participants were observed

and written informed consent was given prior to their participation in

the study.

3. Results

A full overview of characteristics for the 429 participants in the study

is shown in

Table 1.

The median age of participants was 50 years. Par-

ticipants from the governmental fire services had the lowest median age

and the highest percentage with long educations. Conversely, partici-

pants from the air force had the highest median age and the highest

percentage with short educations. Median BMI was above the normal

range in all groups. Dietary intake varied among the primary occupa-

tional exposure groups. Thus, a higher percentage of participants from

airport fire services had a frequent intake of eggs, fish and shellfish.

Notably, 40% of all participants had donated blood at some point.

Participants from airport fire services, the air force and the navy

were exclusively full-time employees. For the 267 men from the

municipal and governmental fire services, characteristics according to

primary employment type is shown in

Supplementary Table S3.

Correlations in serum concentrations of PFAS are shown in

Supple-

mentary Table S4.

Concentrations of PFHxS, PFHpS and PFOS were

strongly or very strongly correlated. Concentrations of PFAS with the

longest carbon chains (PFOS, PFNA, PFDA and PFUnDA) were also

strongly or very strongly correlated. Concentrations of PFOA were,

however, not strongly correlated with the other PFAS.

The median serum concentrations of PFHxS, PFHpS and total PFOS

(1.49, 0.28 and 6.46 ng/mL, respectively) were higher among partici-

pants from airport fire services compared to participants from other

primary occupational exposure groups (Table

2).

Age-adjusted geo-

metric means for serum concentrations of PFHxS, PFHpS and total PFOS

(1.42, 0.28 and 6.92 ng/mL) were also higher among airport fire service

participants in comparison to reference measurements from ENFORCE

(0.72, 0.14 and 5.86 ng/mL for PFHxS, PFHpS and total PFOS, respec-

tively) (Fig.

and

Table 3).

In analyses restricted to participants

commencing service from 2011 and onwards, the age-adjusted geo-

metric means for serum PFAS were, however, closer to even among the

primary occupational exposure groups (Supplementary

Table S5).

analyses according to primary employment type, the medians and age-

adjusted geometric means were lowest among the volunteers, interme-

diary among the part-time employees and highest among the full-time

employees for almost all the measured PFAS (Supplementary

Tables S6 and S7).

In our main regression analysis, serving in civilian airport fire ser-

vices was associated with higher serum concentrations of PFHxS, PFHpS

and PFOS (59.6%, 32.6% and 14.5% difference in adjusted analyses)

compared to participants from municipal fire services (Table

4).

Con-

centrations of PFNA and PFUnDA were also slightly higher among the

civilian airport fire service participants. Conversely, serving in the air

force was associated with lower serum concentrations of PFHxS, PFOS

and PFNA ( 16.3%, 16.2% and 12.8% difference in adjusted ana-

lyses). Finally, service in the navy seemed to be associated with a pos-

itive difference in PFDA and PFUnDA (15.5% and 35.0% difference in

adjusted analyses).

Table 5,

our regression analysis according to primary employment

type is shown. Compared to volunteers, part-time service was associated

with a positive trend difference in serum concentrations of almost all the

measured PFAS with differences appearing more pronounced for full-

time service.

In the expanded regression model, primary occupational exposure

group and employment type, age, blood donations, body mass index and

intake of eggs were the most influential factors in relation to serum

PFAS. Results for PFHxS, total PFOS and PFOA are shown in

Supple-

mentary Table S8.

However, adding adjustment for body mass index and

intake of eggs to our regression analyses did not change results sub-

stantially (Supplementary

Table S9).

4. Discussion

In this cross-sectional study of serum PFAS among men from the

Danish fire services and Armed Forces, findings signified occupational

exposure of civilian airport firefighters. While serum concentrations of

PFAS among most participants were at level with recent age-adjusted

measurements from the general population in Denmark, civilian

airport firefighters had slightly higher concentrations of especially

PFHxS, PFHpS and PFOS in serum (Hull

et al., 2023).

Regression ana-

lyses also confirmed positive associations for these PFAS among civilian

airport firefighters in comparison to municipal firefighters.

Airport fire services specialize in mitigation of aviation emergencies

with requirements for response times and equipment dictated by a risk

of mass casualties. Fires may involve large quantities of aviation fuels

and similar highly flammable liquids prompting widespread use of AFFF

in relation to both civilian and military airports in the past (Nilsson

et al., 2020; Miljøstyrelsen, 2016; Xu et al., 2020; Forsvarsministeriet,

2021).

Analyses of AFFF used in airports and resulting contaminations

have documented the presence of a range of non-polymeric PFAS in

previous generations of firefighting foams with a predominance in

detection of PFOS, PFOA and PFHxS (NIRAS,

2021; Miljøstyrelsen,

2016; Interstate Technology Regulatory Council, 2023).

In Denmark,

foams containing PFOS were banned in 2006 with a transition period

Table 2

PFAS serum concentrations (ng/mL) among the 429 men from the Danish fire services and Armed Forces, 2023–2024.

Primary occupational exposure group

Total

429)

PFAS

PFHxS

PFHpS

PFOA

nPFOS

Total PFOS

PFNA

PFDA

PFUnDA

Mdn (P

, P

95%

)

0.76 (0.36,

0.19 (0.07,

1.02 (0.44,

3.96 (1.41,

5.09 (1.91,

0.43 (0.20,

0.15 (0.08,

0.08 (0.02,

2.03)

0.41)

1.91)

10.19)

12.36)

0.90)

0.34)

0.20)

Municipal

208)

Mdn (P

, P

95%

)

0.74 (0.37,

0.18 (0.06,

1.03 (0.45,

4.00 (1.36,

5.08 (1.77,

0.45 (0.18,

0.16 (0.07,

0.08 (0.01,

1.70)

0.39)

2.11)

10.03)

12.42)

0.96)

0.36)

0.21)

Governmental

59)

Mdn (P

, P

95%

)

0.66 (0.27,

0.17 (0.06,

0.89 (0.39,

3.32 (1.34,

4.41 (1.67,

0.39 (0.19,

0.13 (0.07,

0.07 (0.01,

1.43)

0.39)

1.91)

9.99)

11.92)

1.03)

0.34)

0.25)

Airport

50)

Mdn (P

, P

95%

)

1.49 (0.49,

0.28 (0.08,

1.11 (0.41,

5.12 (1.80,

6.46 (2.35,

0.54 (0.23,

0.16 (0.07,

0.09 (0.03,

3.99)

0.68)

1.92)

14.70)

18.31)

0.95)

0.31)

0.22)

Air force

98)

Mdn (P

, P

95%

)

0.74 (0.36,

0.19 (0.08,

0.95 (0.46,

3.91 (1.61,

5.17 (2.09,

0.41 (0.23,

0.15 (0.09,

0.08 (0.03,

1.41)

0.37)

1.81)

8.75)

11.22)

0.77)

0.29)

0.17)

Navy

14)

Mdn (P

, P

95%

)

0.81

0.19

0.89

4.48

5.68

0.48

0.18

0.10

(0.48, 1.38)

(0.11, 0.35)

(0.47, 1.82)

(2.20, 8.00)

(2.76, 9.91)

(0.28, 0.86)

(0.12, 0.33)

(0.06, 0.18)

PFAS, per- and polyfluoralkyl substances; Mdn, Median, nPFOS, linear PFOS.

Medians and other percentiles are displayed as pseudo percentiles based on five adjacent values.

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Fig. 2.

Age-adjusted geometric means for serum concentrations (ng/mL) of total PFOS, PFOA, PFHxS and PFHpS among men from the Danish fire services and

Armed Forces (n

429, 2023–2024) compared to national measurements from the ENFORCE study (n

496 men, 2021).

Table 3

Age-adjusted geometric means for PFAS serum concentrations (ng/mL) among men (n

429, 2023–2024) from the Danish fire services and Armed Forces compared to

national measurements from the ENFORCE study (n

496 men, 2021).

Primary occupational exposure group

Municipal

ENFORCE

PFAS

PFHxS

PFHpS

PFOA

Total PFOS

PFNA

PFDA

PFUnDA

GM (95% CI)

0.72 (0.66,

0.14 (0.12,

1.15 (1.06,

5.86 (5.53,

0.55 (0.50,

0.19 (0.16,

0.11 (0.09,

0.78)

0.17)

1.24)

6.22)

0.60)

0.22)

0.13)

208)

GM (95% CI)

0.83

0.20

1.10

5.51

0.48

0.17

0.08

(0.77,

(0.18,

(1.03,

(5.05,

(0.44,

(0.16,

(0.07,

0.89)

0.21)

1.17)

6.00)

0.51)

0.18)

0.11)

Governmental

59)

GM (95% CI)

0.77 (0.69,

0.23 (0.20,

1.18 (1.04,

5.32 (4.64,

0.48 (0.42,

0.16 (0.14,

0.08 (0.06,

0.87)

0.26)

1.33)

6.11)

0.54)

0.19)

0.12)

Airport

50)

GM (95% CI)

1.42 (1.20,

0.28 (0.24,

1.07 (0.95,

6.92 (5.85,

0.53 (0.47,

0.16 (0.14,

0.09 (0.07,

1.68)

0.33)

1.21)

8.19)

0.59)

0.18)

0.11)

Air force

98)

GM (95% CI)

0.76 (0.69,

0.20 (0.18,

1.02 (0.92,

5.11 (4.62,

0.44 (0.40,

0.16 (0.15,

0.08 (0.08,

0.82)

0.22)

1.13)

5.66)

0.47)

0.17)

0.09)

Navy

14)

GM (95% CI)

0.88

0.23

1.04

5.97

0.54

0.20

0.11

(0.69, 1.13)

(0.17, 0.29)

(0.77, 1.42)

(4.38, 8.14)

(0.41, 0.71)

(0.16, 0.26)

(0.08, 0.16)

PFAS, per- and polyfluoralkyl substances; GM, geometric mean; CI, confidence interval.

allowing for stockpiled use until 2011 (NIRAS,

2021).

In the last de-

cades, production of AFFF has been adjusted favoring the use of PFHxS,

short-chain perfluoroalkyl acids and fluorotelomers with increasing

competition from PFAS free alternatives (NIRAS,

2021; Interstate

Technology Regulatory Council, 2023).

In a large recent study of airport

firefighters (n

799) from 27 airports across Australia, serum concen-

trations of PFHxS, PFHpS and PFOS were elevated among participants

commencing service prior to 2005 (Nilsson

et al., 2020, 2022a, 2022b).

At this point, use of Lightwater AFFF from 3M had been fully replaced by

a fluorotelomer based solution (Nilsson

et al., 2022a).

Median concen-

trations were 14 ng/mL for PFOS, 6.5 ng/mL for PFHxS and 0.85 ng/mL

for PFHpS for serum sampled in 2018–2019 (Nilsson

et al., 2022a).

In an

earlier and smaller study among a subset of participants (n

149, 2013),

medians were 66 ng/mL for PFOS and 25 ng/mL for PFHxS with no

measurement of PFHpS (Rotander

et al., 2015).

While our more recent

measurements may appear less striking, peak concentrations among our

civilian airport firefighters may also have been an order of magnitude

higher during their actual use of AFFF. In our study, the civilian airport

firefighters were almost exclusively from a single metropolitan airport

ceasing their use of AFFF from 3M in 2008. Since then, PFAS free foam

(Solberg Re-Healing RF3x6 foam) has been used. In our analyses

restricted to participants commencing service from 2011 and onwards,

civilian airport firefighters no longer had markedly higher serum PFAS.

Though contaminated soil and surface water in relation to training

grounds and fire stations may have contributed some exposure in the

years trailing the end of the AFFF era, our findings do not indicate

substantial ongoing occupational exposure to PFAS among airport fire-

fighters (Koordinerende

arbejdsgruppe ved Dragør Kommune TKoKLAS,

2024).

Regarding other potential sources of PFAS, the turnout gear

applied was coated with PFOA until manufacturers in Denmark gradu-

ally transitioned to treating textiles with PFHxA instead from 2020 to

2023 (Kruse,

2021).

We found no indications of higher exposure to

either of these compounds.

In a smaller American study (n

47) from Ohio from 2019, civilian

airport firefighters also had higher concentrations of PFHxS and PFOS in

serum compared to both suburban firefighters and measurements from

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Table 4

Multiple linear regression of associations between primary occupational expo-

sure group and PFAS serum concentrations (ng/mL) among 429 men from the

Danish fire services and Armed Forces, 2023–2024.

Primary occupational exposure group

Municipal

PFAS

PFHxS

Crude

Adjusted

PFHpS

Crude

Adjusted

PFOA

Crude

Adjusted

nPFOS

Crude

Adjusted

Total PFOS

Crude

Adjusted

PFNA

Crude

Adjusted

PFDA

Crude

Adjusted

PFUnDA

Crude

Adjusted

Governmental

% diff (95%

CI)

ref

¡15.7

(-26.9,

-2.8)

12.4 ( 24.5,

1.7)

2.2 ( 17.0,

15.2)

13.4 ( 3.8,

33.6)

6.1 ( 18.1,

7.6)

2.8 ( 16.5,

13.2)

15.5 ( 28.5,

0.0)

7.7 ( 23.1,

10.7)

15.1 ( 28.1,

0.4)

6.3 ( 21.6,

12.1)

10.7 ( 21.8,

1.9)

4.7 ( 17.5,

10.2)

11.3 ( 22.0,

0.9)

9.1 ( 21.4,

5.1)

12.0 ( 28.4,

8.1)

0.3 ( 20.6,

25.2)

Airport

% diff

(95% CI)

76.8

(51.9,

105.8)

59.6

(36.6,

86.5)

50.7

(26.5,

79.5)

32.6

(11.8,

57.4)

2.3

( 11.6,

18.4)

5.2

( 19.2,

11.1)

33.5

(11.7,

59.7)

17.8

( 2.6,

42.5)

31.4

(10.0,

57.0)

14.5

( 5.0,

38.0)

15.4

(0.2,

32.9)

8.8

( 6.5,

26.6)

3.4

( 15.8,

10.9)

5.7

( 18.9,

9.8)

10.6

( 11.3,

37.9)

14.6

(9.7,

45.3)

Air force

% diff

(95% CI)

5.9

( 16.3,

6.0)

¡16.3

(-26.0,

-5.3)

7.8

( 6.0,

23.5)

4.7

( 16.8,

9.2)

2.7

( 13.1,

9.0)

9.9

( 20.6,

2.3)

4.6

( 17.0,

9.6)

¡17.1

(-28.7,

-3.6)

3.0

( 15.5,

11.5)

¡16.2

(-27.7,

-2.8)

5.5

( 15.4,

5.5)

¡12.8

(-22.7,

-1.7)

4.6

( 14.3,

6.1)

9.4

( 19.6,

2.2)

3.4

( 12.8,

22.8)

1.9

( 18.7,

18.6)

Navy

% diff

(95% CI)

3.6

( 20.6,

35.2)

3.0

( 24.1,

24.0)

10.1

( 19.0,

49.7)

9.9

( 16.1,

43.9)

8.5

( 29.1,

18.2)

10.6

( 30.4,

14.9)

6.6

( 22.1,

45.8)

1.0

( 25.1,

36.3)

4.7

( 23.4,

43.1)

0.2

( 25.7,

33.9)

9.7

( 14.4,

40.5)

4.9

( 17.3,

33.2)

17.7

( 7.6,

49.8)

15.5

( 9.0,

46.7)

31.6

( 10.5,

93.7)

35.0

( 7.2,

96.4)

Table 5

Multiple linear regression of associations between primary employment type

and PFAS serum concentrations (ng/mL) among men (n

267) from the

municipal and governmental fire services in Denmark, 2023–2024.

Primary employment type

Volunteer

24)

PFAS

PFHxS

Crude

Adjusted

PFHpS

Crude

Adjusted

PFOA

Crude

Adjusted

nPFOS

Crude

Adjusted

Total PFOS

Crude

Adjusted

PFNA

Crude

Adjusted

PFDA

Crude

Adjusted

PFUnDA

Crude

Adjusted

ref

Part-time

57)

% diff (95% CI)

20.7 ( 3.7, 51.3)

13.0 ( 9.6, 41.1)

20.1 ( 8.6, 57.9)

8.4 ( 16.0, 39.9)

6.4 ( 14.6, 32.7)

2.4 ( 22.3, 22.6)

24.3 ( 5.6, 63.8)

16.2 ( 13.2, 55.6)

24.6 ( 5.1, 63.5)

14.7 ( 13.4, 52.1)

20.4 ( 3.9, 50.8)

23.1 ( 2.9, 56.2)

14.2 ( 8.2, 43.0)

17.9 ( 7.4, 50.3)

57.1 (7.8, 129.0)

63.1 (9.1, 143.8)

Full-time

186)

% diff (95% CI)

43.3 (17.2, 75.2)

39.0 (14.9, 68.2)

32.7 (4.0, 69.3)

25.6 (1.0, 56.2)

19.5 ( 1.8, 45.5)

14.3 ( 6.0, 38.9)

57.7 (23.4, 101.6)

51.2 (17.8, 94.0)

55.6 (22.1, 98.3)

48.5 (16.7, 88.9)

44.6 (18.2, 76.7)

42.4 (16.2, 74.5)

27.5 (4.3, 55.8)

25.1 (1.7, 54.0)

50.4 (7.5, 110.5)

53.1 (8.5, 115.9)

ref

PFAS, per- and polyfluoralkyl substances; diff, difference; CI, confidence inter-

val; nPFOS, linear PFOS.

Statistically significant associations marked in bold.

Adjusted for age, years of service, education and blood donations. Partici-

pants providing no questionnaire information were not included in the adjusted

analyses (n

25).

ref

PFAS, per- and polyfluoralkyl substances; diff, difference; CI, confidence inter-

val; nPFOS, linear PFOS.

Statistically significant associations marked in bold.

Adjusted for age, years of service, education, blood donations and primary

employment type. Participants providing no questionnaire information were not

included in the adjusted analyses (n

40).

the US general population (NHANES data)(Leary

et al., 2020).

Further, a

study from Finland documented changes in especially PFHxS and PFNA

in serum among firefighters (n

8) from the Oulu Airport during a

three-session ARFF training programme using AFFF in 2010 (Laitinen

et al., 2014).

We found no evidence of higher serum PFAS among participants

from the air force. If anything, serving in the air force was associated

with lower serum concentrations of PFHxS, PFOS and PFNA. At present,

the RDAF uses PFAS free foam (Solberg Re-Healing RF3x6 foam)

(Forsvarsministeriet,

2021).

AFFF containing PFOS was, however, used

on the firetrucks at their air bases until 2014 with storage continuing as

late as 2022 (Forsvarsministeriet,

2021; Rigsrevisionen, 2023).

In a

previous study of men (n

1060) from the United States Air Force,

employment in fire protection was the strongest service-related predic-

tor of elevated serum PFHxS, PFOA and PFOS (Purdue

et al., 2023).

The

number of men (n

5) serving in fire protection was, however, rather

limited (Purdue

et al., 2023).

Airports are categorized in order to dimension their ARFF responses

based on characteristics such as daily departure and landing frequencies,

maximum aircraft lengths and fuselage widths, and all-cargo operations

(International

Civil Aviation Organization, 2014).

Airport categories

determine requirements for emergency vehicles and types and amounts

of extinguishing agents used (International

Civil Aviation Organization,

2014).

Thus, differences in airport sizes and categories may explain

some of the differences in exposure to PFAS observed between civilian

and air force firefighters in this study. Job assignments may also differ

among civilians and military employees.

Participants serving in the navy were relatively few in our study and

their observed slightly positive associations for serum PFDA and

PFUnDA were most likely random findings. The concentrations of these

PFAS were quite low with narrow ranges among all groups.

Among participants from the municipal and governmental fire ser-

vices, differences in serum PFAS according to primary employment type

can be interpreted as indication of an occupational exposure gradient.

There are, however, distinct differences in socioeconomic status,

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geographical distribution, health behaviour and disease incidence

among these groups and residual confounding may explain at least some

of the gradient (Petersen

et al., 2018; Petersen, 2018).

Serum PFAS

among the full-time employees was at level with reference measure-

ments from the ENFORCE study. Ultimately, environmental exposure to

PFAS is extremely common with diet as the main source (European

Food

Safety Authority, 2020).

The main strength of the study was the inclusion of participants from

different occupational firefighting groups with different employment

types, durations and times. Further, workplaces in all five regions of

Denmark were represented in the study. Finally, participants provided

extensive information on potential sources of PFAS exposure both within

and beyond the working environment.

While recruitment efforts were extensive and flexible with numerous

information meetings both during and after working hours at work-

places across the country, the overall participation rate (28%) was

somewhat lower than expected. Firefighters assumed to be more

exposed following intense use of foam may have been more likely to

participate causing a potential bias from selection. Further, capturing

the full occupational history of firefighters may be quite complicated

with many potentially overlapping employments. Our approach of

assigning a primary occupational exposure group and employment type

was rather crude. Thus, 58% of participants belonged to more than one

of the occupational exposure groups and 37% of participants had served

with more than one employment type. Potential misclassification of

occupational exposure was equal across all the groups in the study and,

therefore, non-differential.

Our targeted analyses of PFAS were highly sensitive. Considering the

vast number of PFAS, the targeted approach was, however, inex-

haustive. No fluorotelomers were measured. Fluorotelomers may,

however, act as precursors and ultimately degrade into the measured

perfluoroalkyl acids (e.g. 6:2-fluorotelomer sulfonic acid can degrade

into PFHxA, PFPeA and PFBA, while 8:2-fluorotelomer sulfonic acid can

degrade into PFOA) (NIRAS,

2021).

We also prioritized measurements of

both short- and long-chained PFAS. Although the toxicokinetic docu-

mentation for short-chained PFAS remains limited, these compounds

appear to have much shorter half-lives for excretion (44 days for PFBS,

230 days for PFPeS, 32 days for PFHxA, and 62 days for PFHpA) and

their measured concentrations or their lack of such, therefore, reflect

only more recent exposures (The

Danish Environmental Protection

Agency et al., 2015; Xu et al., 2020; U.S. Environmental Protection

Agency, 2023).

Ultimately, assessment of occupational exposure to

PFAS remains challenging as manufacturers of products such as fire-

fighting foams and turnout gear face limited requirements for declaring

specific contents.

Serum concentrations of legacy PFAS have declined over the last

decades in Denmark (Hull

et al., 2023).

Our reference measurements

from the ENFORCE study were based on samples from 2021 analyzed in

a different laboratory. Applying these older measurements from an older

study population with no information on aspects such as blood donation

in comparisons, we may underestimate the current differences between

serum PFAS among the firefighters and the general population in

Denmark.

5. Conclusion

Slightly higher concentrations of especially PFHxS, PFHpS and PFOS

in serum among civilian airport firefighters compared to the general

population most likely reflected remnants of past occupational exposure

to firefighting foam. The use of firefighting foam containing PFAS was

discontinued by the civilian airport fire services more than a decade

prior to the study. Thus, our findings emphasize the importance of

protection through robust regulation and substitution.

CRediT authorship contribution statement

Kajsa Ugelvig Petersen:

Writing

–

review

editing, Writing

–

original draft, Visualization, Validation, Supervision, Software, Re-

sources, Project administration, Methodology, Investigation, Funding

acquisition, Formal analysis, Data curation, Conceptualization.

Dorthe

Furstrand Lauritzen:

Writing

–

review

editing, Validation, Software,

Investigation, Formal analysis, Data curation, Conceptualization.

Regi-

tze Sølling Wils:

Writing

–

review

editing, Methodology, Investiga-

tion, Conceptualization.

Anne Thoustrup Saber:

Writing

–

review

editing, Methodology, Conceptualization.

Ulla Vogel:

Writing

–

review

editing, Methodology, Conceptualization.

Niels Erik Ebbehøj:

Writing

–

review

editing, Methodology, Conceptualization.

Johnni

Hansen:

Writing

–

review

editing, Methodology, Conceptualization.

Julie Elbæk Pedersen:

Writing

–

review

editing, Methodology,

Conceptualization.

Tina Kold Jensen:

Writing

–

review

editing,

Methodology, Conceptualization.

Maria Helena Guerra Andersen:

Writing

–

review

editing, Methodology, Investigation,

Conceptualization.

Funding

This work was supported by the Danish Health Authority. The

funding source had no involvement in the study design, data collection,

analysis and interpretation, writing of this research article or decision to

submit for publication.

Conflicts of interest

The authors declare no conflicts of interests.

Acknowledgements

The authors wish to thank all of the involved workplaces and par-

ticipants in the study.

Appendix A. Supplementary data

Supplementary data to this article can be found online at

https://doi.

org/10.1016/j.ijheh.2025.114559.

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