When all these risks are considered together, the role of chemical exposures in causing cancer is small and, as of now, not very clear. Scientists know very little about how contact with most chemicals causes cancer. Substances known to cause cancer are called carcinogens.ollution & Exposure to Chemicals Exposure to some chemicals and hazardous substances can increase the risk of cancer. A few well-known carcinogens are asbestos, nickel, cadmium, radon, vinyl chloride, benzidene, and benzene. These carcinogens may act alone or with another carcinogen to increase your risk.