Application of bioavailability measurements in medical geology

This chapter gives an overview of how bioavailability measurements are used in medical geology. In broad terms, bioavailability is a measure of the amount of chemical in the geological material that has the ability to have a biological effect on humans or animals. Definitions of bioavailability and the closely related term bioaccessibility are given for three pathways by which chemicals can enter the body, namely: ingestion, inhalation, and dermal absorption. A literature search on the bioavailability of potentially harmful elements in soils gave 3631 of scientific papers. Text mining of the paper abstracts identified nine themes (X-ray Absorption, Solid/Intestinal and Gastric phases, Soil properties, Risk assessment, Sequential Extraction, Organic Matter, Microbiology, Particle Size, Lead and Phosphorus). A review of a selection of the papers under these themes is given. A summary and discussion of the current ingestion in vitro bioaccessibility tests that are in common use is provided and an example case study of how bioaccessibility measurements can be put to practical use is given on the bioaccessibility of arsenic in south west England. Finally, future research in bioavailability testing is discussed in which further work on the development of testing methodologies for inorganic contaminant bioavailability tests for the dermal and inhalation routes is required along with methods for all three exposure pathways for organic contaminants in soil. Speculation on the use of organ-on-a-chip developments as a replacement for in vitro bioavailability testing is also discussed.