The measurement of particulate matter induced oxidative potential activity by dithiothreitol (DTT) as an alternative quantitative method has been of recent interest. The mechanism of this process is not well understood. Proposed mechanisms often involve formation of the hydrogen peroxide as the final step. Evidence suggests that this may not be the dominant route. We applied computational methods to determine a possible alternative mechanism in the presence of .OH radical production. An energetically favored mechanism was found for DTT-chemical reactivity reaction which is consistent with previously reported experimental results.