In environmental and human health protection, the role for geoscience may be expressed by how it enhances certainty in the hazard potential models that support risk assessment. For geochemical hazards, certainty reflects how well geoscience simplifies variability in the element concentrations and in the environmental conditions associated with exposure pathways. Through mineralogy, geoscience establishes natural geochemical background variability in terms of provenance, process, and past, and it links hazard potential to the physical and chemical transformation due to weathering and soil formation. The interpretation of hazard potential may be expressed by how analytical protocol, expressed by grain size and strength of acid decomposition, combines with geological factors, expressed by (1) mineralogy and mineral partitioning and (2) environmental cofactors, including moisture, pH, buffering capacity, and porosity. With this type of knowledge, geoscience enhances the potential to identify covariant relations between hazard indicators and disease, and to resolve potential causal factors.