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Hammel et al. J Environ Expo Assess 2024;3:8 https://dx.doi.org/10.20517/jeea.2023.51 Page 13 of 17

permeability of BFRs have shown that dermal uptake of NBFRs does occur, though much is initially trapped
[82]
in the epidermis . The highest dermal uptake is expected for the BFR with lower log K such as DPTE,
ow
HBCDD, and the least brominated PBDEs, and it cannot be ruled out that dermal uptake may be a relevant
exposure pathway.

CONCLUSION
Despite attention to BFRs over the last few decades, NBFRs have only scarcely been studied with regard to
human external and internal exposure. This study shows that the internal exposure levels of NBFRs were
similar to those of most PBDEs already at the time of PBDE restrictions. As opposed to PBDEs, NBFRs were
not correlated in breast milk and house dust, indicating other prominent exposure pathways than dust
ingestion and/or transformation and toxicokinetic processes which are not yet understood. These data add
to the knowledge of exposure pathways and estimated total intake for infants that may be a valuable
reference point for future BFR studies and assessment of current and future restrictions.

DECLARATIONS
Acknowledgments
The authors would like to thank all study participants for volunteering, Marie Pedersen for the initial
recruitment, and Birgit Groth for skillful analyses of NBFRs, DPs, and HBCDDs.

Authors’ contributions
Writing - original draft: Hammel SC, Frederiksen M
Conceptualization: Vorkamp K, Nielsen JB, Sørensen LS, Knudsen LE, Frederiksen M
Writing - review & editing: Vorkamp K, Nielsen JB, Sørensen LS, Knudsen LE
Supervision: Vorkamp K, Knudsen LE
Funding acquisition: Vorkamp K, Nielsen JB, Sørensen LS, Knudsen LE, Frederiksen M
Methodology, resources: Vorkamp K, Knudsen LE, Frederiksen M
Data curation, project administration: Vorkamp K, Frederiksen M
Visualization, formal analysis: Hammel SC
Investigation: Frederiksen M

Availability of data and materials
Fully anonymized data can be shared upon justified request.

Financial Support and sponsorship
The study was supported by the Danish Agency for Science, Technology and Innovation (271-06-0355) and
Danish Council for Independent Research (DFF - 1333-00034), the data analyses and publication were
further supported by FFIKA (Focused Research Effort on Chemicals in the Working Environment) from
the Danish Government.

Conflict of Interest
All authors declare that there are no conflicts of interest.

Ethical approval and consent to participate
The study was approved by the Regional Ethics Committee of the Capital Region of Denmark (H-KF-
327603) and the Danish Data Protection Agency. All participants provided written consent to participate.