Other causes may include spasm of an artery. This may occur due to cocaine. Cancer is also another well recognized potential cause of stroke. Although, malignancy in general can increase the risk of stroke, certain types of cancer such as pancreatic, lung and gastric are typically associated with a higher thromboembolism risk. The mechanism with which cancer increases stroke risk is thought to be secondary to an acquired hypercoagulability. Air pollution is responsible for around 27% of deaths from strokes worldwide, according to the Global Burden of Disease Study.