From Environmental Evidence to Biomarker Selection: A Structured Decision-Support Process for Human Biomonitoring Studies in Contaminated Sites.

Human Biomonitoring (HBM) is a key tool for assessing human exposure to environmental contaminants and identifying early biological changes potentially associated with adverse health effects. However, as contaminated sites are characterized by multiple pollutants, exposure pathways and biological targets, a structured decision-support process is required to guide exposure assessment, biomarker selection, and early health-risk evaluation. This manuscript does not report biomonitoring results but describes the methodological process used to design the INSINERGIA_RT HBM study in two contaminated areas of Tuscany, Italy. The study design integrated environmental evidence, toxicological knowledge, epidemiological priorities, biomarker relevance, analytical feasibility, logistical considerations, and public health needs. Instead of proposing a universally applicable framework, the manuscript presents a structured approach that may support the design of HBM studies in similarly complex settings. Biomarkers are organized within a hierarchical model reflecting successive stages of the biological response to environmental exposure. A central feature is a mechanistic, multi-level approach encompassing upstream pathways (oxidative stress and inflammation), early markers of adverse effects and subclinical organ damage, including cardiovascular, renal, and respiratory alterations, and integrative indicators of cumulative biological responses, such as telomere length, epigenetic changes, and metabolomic profiles. Applicability is illustrated through an ongoing HBM study in Livorno and Piombino (Tuscany).