Solvents are used in paint removers, grease removers, paint thinners, and dry cleaning. The solvents benzene, carbon tetrachloride, chloroform, and methylene chloride have been linked to human cancer.
The strongest evidence linking a solvent to cancer involves benzene, which is also found in cigarette smoke and gasoline. It increases the risk of leukemia.
If you must work with solvents, work outside or make sure the area is well ventilated.