Yes. In some occupational settings, or over the working history of an individual, there is the possibility of being exposed to several occupational cancer-causing substances simultaneously or in sequence. Typical combinations are: radon or arsenic and crystalline silica; asbestos and polycyclic aromatic hydrocarbons (PAHs); or chromium and nickel compounds.

Smoking often adds substantially to the risk related to occupational cancer-causing substances. For example, the risk of lung cancer in asbestos workers is much higher in those who also smoke, and smoking is a stronger risk factor in these individuals than is asbestos.