Advancing urban exposome research through the integration of qualitative and quantitative approaches in epidemiological research

The notion of 'urban exposome' brings promise to the public health and epidemiology fields of inquiry, particularly within research projects conducted within birth cohorts. However, it is also challenging. The present paper addresses how combining qualitative methods with numerical data on exposures and health outcomes may help to fulfil that promise while posing important challenges to researchers. Quantitative methods based on Geographic Information System and other geo-technologies establish the linkage between participants' residential locations and geospatial datasets, generating many quantitative measurements of environmental exposures throughout participants' life course since birth. Yet, abstracted quantitative measurements alone do not capture lived experiences and do not allow for a rich inquiry about the complex and situated webs of social, physical, and biological phenomena that shape their bodies. Qualitative approaches may enhance quantitative data collected from sensors, blood samples, and physical examinations. These methods help to uncover, with depth and nuance, how individuals build meaning, navigate their surroundings, and how their complex contexts shape their lives and health, strengthening epidemiological evidence. In other words, they may help produce more data points and provide context, thus improving the interpretation of quantitative measurements. Besides, some of these methods promote reflection, collective discussion, and community empowerment. By integrating quantitative and qualitative approaches, researchers can obtain a more holistic and contextualised understanding of the external urban exposome. Multi-methods and mixed-methods approaches may strengthen the validity of findings, improve the interpretability of results, generate new hypotheses, and support the development of place-based interventions. Nevertheless, integrating quantitative and qualitative approaches may raise several challenges related to epistemological and ontological tensions, different scientific practices, ethical compliance, and the training of research teams. Concluding, the combined use of quantitative and qualitative methods in measuring the external urban exposome within cohort studies offers a powerful approach to understanding the complex interplay between urban environments and health outcomes.