Biomonitoring of per- and polyfluoroalkyl substances (PFAS) exposure in firefighters: Study design and lessons learned from stakeholder and participant engagement.

Firefighters may be occupationally exposed to per- and polyfluoroalkyl substances (PFASs) through Aqueous Film-Forming Foam (AFFF), smoke, dust and turnout gear, in addition to other background exposure sources. Epidemiological assessment of PFAS exposure in an occupational cohort of firefighting staff commenced in 2013-2014, following cessation of PFAS-based AFFF in Australian aviation. Here we present the study design and methodology of a follow-up study conducted in 2018-2019. We focus on our experiences engaging with stakeholders and participants with the establishment of an inclusive study group and highlight the key lessons learned from implementing a co-design process in the study. The study included a cross-sectional assessment of blood serum concentrations of 40 PFASs, including perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS), and 14 health-related biomarkers in 799 current and former Aviation Rescue Firefighting Services employees. A large proportion (87%) of the participants from the preliminary exposure study in 2013-2014 were re-recruited in the follow-up study. This enabled further longitudinal analyses in this subset of 130 participants. Participants included employees from different work roles and timeframes, reflecting the periods when three different firefighting foams were utilised in Australia. Establishment of a collaborative and inclusive study group (including stakeholders and participants) contributed to several components of the study design, including the expansion of robust analytical quality assurance and control measurements, and tailoring of communication and dissemination strategies. These outcomes were key factors that improved transparency of the research design, methods and results. Additionally, implementing elements of co-design helped build trust between researchers and participants, which is an important consideration for studies funded by stakeholders related to the exposure source.