A weak organic acid is used to effect the release of CaDPA from Bacillus or Clostridium endospores, rapidly and at room temperature, to enable detection and measurement of DPA and thereby the assessment of risk associated with exposure to Bacillus anthracis, Clostridium botulinum, and like spores. The method can be applied to airborne, food-borne, and water-borne spores, as well as to spores collected from surfaces or contained in body fluids, and analysis is advantageously carried out using surface-enhanced Raman spectroscopy.