Breast cancer in female radium dial workers first employed before 1930

Female radium dial workers first employed before 1930 were analyzed for breast cancer mortality and incidence using method and rate tables described by Manson and the Mantel-Haenszel summary chi-square test for significance. Of 1180 located women, 736 were measured to estimate radium intake. This measured group was analyzed for breast cancer mortality and incidence according to four possible risk factors: radium intake dose, duration of employment, age at first exposure, and parity. The located women had a mortality ratio of 1.51 (p < 0.05). The measured women showed a significant excess of breast cancer incidence and mortality only among those women with a radium intake of 50 μCi or greater. Although not significant, incidence and mortality ratios were slightly higher for nulliparous women