Quantification of synergistic, additive and antagonistic effects of aerosol components on total oxidative potential.

The interaction-based oxidative potential (OPint) represents the prediction of binary mixture effects distinguishing from linear additivity by including information on binary mixtures among PM components. The objective of this work is to develope a reliable estimate on the possible synergistic or antagonistic possibility of binary PM components and to quantify the combined effect. We firstly assessed the interactions among PM components in generating the OP based on DTT consumption rate and AA depletion. We started with the standard solution sequence (from 0.005 to 10 μM), including quinones (PQ, 1,2-NQ, and 1,4-NQ) and metals (Cu, Mn, and Fe). The interactions between metals were antagonistic interactions in DTT consumption. Cu showed antagonistic interaction with PQ, but additive with 1,2-NQ and 1,4-NQ. Mn interacted synergistically with 1,4-NQ in DTT consumption but antagonistically with PQ (where CPQ < 2.5 μM) and 1,4-NQ (where CPQ < 2 μM). Fe showed synergistic with quinones in investigated concentration range (from 0.01 to 5 μM). Finally, applying a moderate approach, on the basis of interaction magnitude (M = 5), resulted in 1-17% higher environmental risks, compared with the classical calculation method using simple addition. This work highlights a new approach to quantify the interaction effects between metals and quinones in PM components, and apportioning the components' contributions for PM OP.