Answer: exposure to chemicals im not that sure but or fond of this
Explanation:
What makes a source credible is it has backed up information. Basically, it has to have supporting details so you know its true.
The war which occurred in the mid-1800s that weakened the economy of the Ottoman Empire was the Russo-Turkish War, led by the Turks on one side, and Russia, Bulgaria, Romania, Serbia, and Montenegro on the other.