Introduction Following the fire at the Lubrizol and NL Logistique facilities in Rouen on September 26, 2019, the Directorate General for Health asked Santé publique France to propose a methodology for assessing the medium-term health impacts on the affected population. Among the various responses proposed, the question arose as to whether it would be appropriate to conduct a biomonitoring study of population exposure several weeks or even several months after the fire, given the lack of an emergency biomonitoring system available in France. This analysis is the subject of the present report. Method This report was produced by a Santé publique France working group with the support of external experts. It presents: i) the approach to follow to assess the relevance of a biomonitoring study, ii) the application of this approach to the situation based on available data, iii) information (fate in the body and health effects) on the pollutants identified based on those potentially emitted, listed by INERIS and ANSES in late 2019, and the corresponding available biomarkers, iv) a conclusion on the advisability of a biomonitoring study, and v) recommendations for future situations and for improving the approach. Results and Discussion Numerous pollutants may have been emitted during the fire. Pending a comprehensive environmental assessment, the analysis of the environmental situation was based on theoretical or incomplete data regarding the released substances and public exposure. The substances likely to be considered for a biomonitoring study are persistent organic pollutants, such as dioxins and PAHs (polycyclic aromatic hydrocarbons); lead could be included if it is found to have been emitted during the fire. Other substances, such as zinc, perfluorinated compounds, phthalates, and BTEX (certain volatile organic compounds), were not deemed relevant. The primary expected route of exposure for residents living near the site several weeks after the fire is the oral route via the consumption of contaminated local products or the ingestion of soil dust contaminated by fallout from the fire. In the absence of chronic airborne emissions, the inhalation route is no longer a concern. A biomonitoring study aimed at characterizing potential overexposure among exposed populations is feasible for dioxins, PAHs, and possibly lead, given the availability of biomarkers for these pollutants. It is relevant only if contamination of the environment and the food chain that could lead to chronic exposure is identified. It remains difficult to implement, and interpreting the data will be challenging (no health-related interpretation at the individual level, other possible sources of exposure). Given the area’s industrial history, it will be difficult to isolate the contribution of the fire to the contamination of the local population. To do so, environmental data capable of characterizing the chemical signature of the accident would be necessary, as well as the selection of a relevant control population to study. Furthermore, the added value of this study for risk management will be limited, as numerous measures have already been taken. Recommendations The implementation of a biomonitoring system immediately following an accident is recommended for future situations in order to assess contamination of the potentially exposed population. Santé publique France will incorporate considerations regarding the implementation of an emergency response system into the national strategy for the biomonitoring program.