A variety of substances used in the workplace, as well as ionizing radiation, have been found to cause cancer in humans. Estimates of the proportion of cancer that may be attributed to workplace exposures range from 5% to 20% and vary widely by cancer site. The Massachusetts Cancer Registry at the Massachusetts Department of Public Health (MDPH) collects data on newly diagnosed cancer cases in Massachusetts, including information about the usual industry and occupation of the cancer cases. OHSP has conducted studies using the Massachusetts Cancer Registry data to examine potential links between workplace exposures and cancer. OHSP has also worked to evaluate the quality of the employment data in the Cancer Registry..