Assessing correlations between geological hazards and health outcomes: Addressing complexity in medical geology.

BACKGROUND The field of medical geology addresses the relationships between exposure to specific geological characteristics and the development of a range of health problems: for example, long-term exposure to arsenic in drinking water can result in the development of skin conditions and cancers. While these relationships are well characterised for some examples, in others there is a lack of understanding of the specific geological component(s) triggering disease onset, necessitating further research. OBJECTIVES This paper aims to highlight several important complexities in geological exposures and the development of related diseases that can create difficulties in the linkage of exposure and health outcome data. Several suggested approaches to deal with these complexities are also suggested. DISCUSSION Long-term exposure and lengthy latent periods are common characteristics of many diseases related to geological hazards. In combination with long- or short-distance migrations over an individual's life, daily or weekly movement patterns and small-scale spatial heterogeneity in geological characteristics, it becomes problematic to appropriately assign exposure measurements to individuals. The inclusion of supplementary methods, such as questionnaires, movement diaries or Global Positioning System (GPS) trackers can support medical geology studies by providing evidence for the most appropriate exposure measurement locations. CONCLUSIONS The complex and lengthy exposure-response pathways involved, small-distance spatial heterogeneity in environmental components and a range of other issues mean that interdisciplinary approaches to medical geology studies are necessary to provide robust evidence.