Bone cancer among female radium dial workers. Latency periods and incidence rates by time after exposure: brief communication.

Bone cancer in 1,250 women exposed to radium while working in the luminous watch-dial industry between 1913 and 1929 were analyzed for times of appearance ("latency periods") and incidence rates over time after first exposure. The lowest radium intake dose associated with bone cancer, among 751 women whose intake doses had been determined, was 202.5 muCi. Mean and median bone cancer latency periods tended to decline, but average survival among women without bone cancer also decreased with increasing intake level. Bone cancer incidence rates over time were compared in 2 intake-dose groups (200--749 and greater than or equal to 759 muCi) by means of an actuarial method that takes competing risks into account. Incidence rates were consistently higher in the higher intake-dose group versus the lower dose group at each 5-year period after first exposure. The variability in the odds ratios across the time periods was not statistically significant, and the actuarial method provided little evidence for an effect of intake dose on the pattern of incidence rate over time. With the use of similar methods, no significant variability was evident in the relative odds of bone cancer over time after exposure between one group of women first exposed to radium at less than 18 years of age and another group exposed when 18 or more years old.