An assessment of trace metal quantification capabilities for indoor (123+/-53μg; mean+/-standard deviation of particle mass) and personal exposure (PE) (32+/-12μg) PM 2 . 5 samples from Baltimore, MD was undertaken as part of an EPA study investigating health effects associated with particulate matter. This study included determination of total PM 2 . 5 metal concentrations by energy dispersive X-ray fluorescence and instrumental neutron activation analysis, as well as method development to quantify amounts of water and acid-extractable metals from PM 2 . 5 using inductively coupled plasma-mass spectrometry (ICP-MS). Analytical uncertainties, filter blank contributions, and sample preparation were all found to significantly impact quantification limits. The ICP-MS leaching procedure resulted in partial extraction of metals from the PM 2 . 5 . Most of the extractable components of the metals were in a water-soluble form suggesting a high potential for bioavailability of elements from respiratory exposure to PM 2 . 5 . A comparison of PM 2 . 5 trace metal concentrations from indoor air samples collected from a central indoor site versus concurrently collected PE samples indicates that resident activities result in exposure to higher concentrations of soluble trace metals.