Extended Follow-up of Cancer Incidence in Fluoride-Exposed Workers

Extract

Workers at the cryolite mill in Copenhagen, Denmark, are unique because of their exposure to high levels of fluoride dust and their virtual lack of exposure to other occupational toxicants or carcinogens (1,2). We previously reported the cancer morbidity from 1943 through 1987 for 422 male cryolite workers employed for more than 6 months at the mill from 1924 through 1961 (1). We observed excess incidences of primary cancer of the lungs and of urinary bladder tumors (including bladder papilloma).

We have now extended the follow-up of this cohort by 12 years, at the end of which the total percentage of cohort members who had died exceeded 90%. As previously described (1), the personal identification numbers of the cohort were linked to the files of the Danish Cancer Registry. The period of observation for calculation of the risk of developing cancer began at the completion of 6 months of employment or on January 1, 1943, whichever occurred later. The end of the observation period was the date of death, the date of emigration, or December 31, 1999, whichever occurred first. Because most members of the cohort lived in the Copenhagen area, expected numbers of cancer cases were calculated by using the cancer-site–specific incidence rates for Copenhagen men.