Selection of MDD in Finished products

If I am working on single nitrosamine impurity for combination (two APIs) of finished product and out of them one (API) content has high MDD and other (API) has low MDD content, also based on information, I concluded that possible single nitrosamine impurity generated only from low MDD API.

So, for limit calculation purpose (AI/MDD), which MDD should be taken ? (Low MDD API or High MDD API)

Thank you.