869 a newspaper in locality A became aware started an investigation of its own resulting in its identification of leukaemia among benzene-exposed workers, some of whom were former pliofilm production workers. In June, 1977, during routine ascertainment of pathology reports for the leukaemia cases, a hematologist in locality A informed us of several previously identified cases of leukwmia among workers at that location. We hope that these comments now answer the questions-originally voiced at the O.S.H.A. hearings (and responded to at those hearings) and once again raised in the forum of The
lity.9.IO Subsequently,
of our study and
Lancet. Studies Branch, Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Center for Disease Control, Cincinnati, Ohio 45202, U.S.A.
Industry-wide
PETER F. INFANTE ROBERT A. RINSKY JOSEPH K. WAGONER RONALD J. YOUNG
ARSENICAL AIR POLLUTION AND LUNG CANCER
SIR,-An increased risk of lung cancer has been reported among residents of counties which house smelters, and arsenic in the smelter smoke was suggested as a possible causal agent.’1 Using a population-based cancer registry we have investigated the clustering of lung-cancer cases around one of the copper smelters included in the original report. This employs over 1000 workers and releases about 214 000 tons of sulphur dioxide and an unknown amount of arsenic annually into the Salt Lake Valley atmosphere. The smelter is on the western edge of a valley with a population of 475 000 which is at 1300 m elevation, is 48 x 32 km in area, and is bounded by east and west mountain ranges rising to approximately 3300 m. Prevailing northwesterly winds carry the smelter’s effluent across the valley from its northwest corner. The communities closest to the smelter receive the greatest amounts and we thus assumed that these people would have higher risk of lung cancer. ASSOCIATION BETWEEN DISTANCE FROM THE SMELTER AND
INCIDENCE OF CANCER
of lung cancer in 1969-75, and, of lymphoma from that penbd. Addresses at the time of diagnosis were available for 97% of cases and controls. These were plotted on U.S. Geological Survey maps, and a coordinate system was constructed with the origin at the smoke stacks of the smelter. Cases and controls were grouped according to their position less than or equal to 5, 10, 15, and 20 miles from the smelter. Statistical testing used the Mantel-Haenszel chi-square procedure,2controlled We identified all
as
new cases
controls, used all
9 Lemen,
cases
R A., and others. Paper read at third international symposium Detection and Prevention of Cancer, held in New York in April, 1976. 10 Akron Beacon Journal, April 18, 1976. 1. Blot. W. J, Fraumeni, J. F. Lancet, 1975, ii, 142. 2. Mantel, N. J. Am. Statis, Assoc. 1963, 58, 690.
for age and sex. The accompanying table shows the distribution of cases and controls for both men and women. There was no significant difference at any specific distance from the smelter and the number of cases within the four distances tested were all close to expectation. We thus cannot support the previous conclusion’ that closeness to a smelter increases the risk of lung cancer. Our use of lymphoma cases as a control can be questioned, but no association between lymphoma and arsenic has been reported. Our results may be influenced by the low lung cancer rate in Salt Lake County which in 1966-75 was 36% below U.S. White incidence-rates. Huwever, the communities closest to the smelter have the highest proportion of smelter employees, who thus have a work and home exposure to effluent, and a greater proportion of these smoke.4 On the grounds of smoking alone, lung cancer cases might be expected to cluster nearer the smelter than the lymphoma cases, but this was not the case. We emphasise that our cases were identified at the time of diagnosis, rather than at time of death. Significant migration between the time of diagnosis and death in lung cancer patients has been reported by ourselves5 and others.6 It should also be pointed out that in both this and the previous investigation,there was no control for smoking, a strong potential confounding factor. Nevertheless, our study found no association between lung cancer and residence near a smelter. Division of Epidemiology,
Department of Family and Community Medicine University of Utah, Salt Lake City, Utah 84132, U.S.A.
JOSEPH L. LYON JEFFREY L. FILLMORE MELVILLE R. KLAUBER
EXOGENOUS ŒSTROGENS AND OVARIAN CANCER
SIR,-Dr Hoover and his colleagues (Sept. 10, p. 533) report an association between use of exogenous oestrogens for six months or more and subsequent ovarian cancer. We have just completed a case-control study in the Rochester, Minnesota, population, and found no association between exogenous oestrogen use for six months or more and epithelial ovarian cancer (relative risk 1.0, 95% confidence interval 0-5—1-9) or with conjugated oestrogen use of six months or more (relative risk 0.9, 95% confidence interval 0-4—1-8). This study was done in the same population and with the same methods as a case-control study on endometrial cancer in which we found a significant relationship between conjugated oestrogens and endometrial cancer.7 Other workers have investigated exogenous oestrogen use in case-control studies and have not found it to be related to ovarian cancer.8-10 Hoover et al. reported 8 cases of ovarian cancer in an oestrogen-exposed cohort where the expected number was 3.3(relative risk 2.4, 95% confidence interval 1-0-4.4). All the patients were at risk of ovarian cancer in that they had at least one ovary. The person-years of follow-up were terminated if the patient underwent an oophorectomy. Thus, only personyears were obtained from the total population, including those ovary) were considered. The rates they applied to these personyears were obtained from the total population, including those not at risk of ovarian cancer. We do not know the prevalencerates of bilateral oophorectomy in the populations served by the three tumour registries whose incidence-rates were used by Hoover et al. However, in Rochester about 10% of the female population over 45 are without ovaries and are thus not at risk 3. Criteria for a Recommended Standard. Occupational Exposure to Inorganic Arsenic: New Criteria. Center for Disease Control, 1975. 4. Smith, T. J., Peters, J. M., Reading, J. C., Castle, H. C. Am. Rev. resp. Dis. 5. 6.
1977, 116, 31. Graft, W. T., Lyon, J. L. Am. J. Epidemiol. 1977, 106, 23. Haenszel, W., Loveland, D. B., Sirkin, M. R. J. nat. Cancer Inst. 1975, 28, 947.
on
7. 8. 9. 10.
McDonald, T. W., and others Am. J. Obstet. Gynec. 1977, 127, 572. West, R. O. Cancer, 1966, 19, 1001. Wynder, E. L., and others, Cancer, 1969, 23, 352. Lau, H. U., and others, Arch. Geschwulstforsch. 1977, 47, 57.
lity.9.IO Subsequently,
of our study and
Lancet. Studies Branch, Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Center for Disease Control, Cincinnati, Ohio 45202, U.S.A.
Industry-wide
PETER F. INFANTE ROBERT A. RINSKY JOSEPH K. WAGONER RONALD J. YOUNG
ARSENICAL AIR POLLUTION AND LUNG CANCER
SIR,-An increased risk of lung cancer has been reported among residents of counties which house smelters, and arsenic in the smelter smoke was suggested as a possible causal agent.’1 Using a population-based cancer registry we have investigated the clustering of lung-cancer cases around one of the copper smelters included in the original report. This employs over 1000 workers and releases about 214 000 tons of sulphur dioxide and an unknown amount of arsenic annually into the Salt Lake Valley atmosphere. The smelter is on the western edge of a valley with a population of 475 000 which is at 1300 m elevation, is 48 x 32 km in area, and is bounded by east and west mountain ranges rising to approximately 3300 m. Prevailing northwesterly winds carry the smelter’s effluent across the valley from its northwest corner. The communities closest to the smelter receive the greatest amounts and we thus assumed that these people would have higher risk of lung cancer. ASSOCIATION BETWEEN DISTANCE FROM THE SMELTER AND
INCIDENCE OF CANCER
of lung cancer in 1969-75, and, of lymphoma from that penbd. Addresses at the time of diagnosis were available for 97% of cases and controls. These were plotted on U.S. Geological Survey maps, and a coordinate system was constructed with the origin at the smoke stacks of the smelter. Cases and controls were grouped according to their position less than or equal to 5, 10, 15, and 20 miles from the smelter. Statistical testing used the Mantel-Haenszel chi-square procedure,2controlled We identified all
as
new cases
controls, used all
9 Lemen,
cases
R A., and others. Paper read at third international symposium Detection and Prevention of Cancer, held in New York in April, 1976. 10 Akron Beacon Journal, April 18, 1976. 1. Blot. W. J, Fraumeni, J. F. Lancet, 1975, ii, 142. 2. Mantel, N. J. Am. Statis, Assoc. 1963, 58, 690.
for age and sex. The accompanying table shows the distribution of cases and controls for both men and women. There was no significant difference at any specific distance from the smelter and the number of cases within the four distances tested were all close to expectation. We thus cannot support the previous conclusion’ that closeness to a smelter increases the risk of lung cancer. Our use of lymphoma cases as a control can be questioned, but no association between lymphoma and arsenic has been reported. Our results may be influenced by the low lung cancer rate in Salt Lake County which in 1966-75 was 36% below U.S. White incidence-rates. Huwever, the communities closest to the smelter have the highest proportion of smelter employees, who thus have a work and home exposure to effluent, and a greater proportion of these smoke.4 On the grounds of smoking alone, lung cancer cases might be expected to cluster nearer the smelter than the lymphoma cases, but this was not the case. We emphasise that our cases were identified at the time of diagnosis, rather than at time of death. Significant migration between the time of diagnosis and death in lung cancer patients has been reported by ourselves5 and others.6 It should also be pointed out that in both this and the previous investigation,there was no control for smoking, a strong potential confounding factor. Nevertheless, our study found no association between lung cancer and residence near a smelter. Division of Epidemiology,
Department of Family and Community Medicine University of Utah, Salt Lake City, Utah 84132, U.S.A.
JOSEPH L. LYON JEFFREY L. FILLMORE MELVILLE R. KLAUBER
EXOGENOUS ŒSTROGENS AND OVARIAN CANCER
SIR,-Dr Hoover and his colleagues (Sept. 10, p. 533) report an association between use of exogenous oestrogens for six months or more and subsequent ovarian cancer. We have just completed a case-control study in the Rochester, Minnesota, population, and found no association between exogenous oestrogen use for six months or more and epithelial ovarian cancer (relative risk 1.0, 95% confidence interval 0-5—1-9) or with conjugated oestrogen use of six months or more (relative risk 0.9, 95% confidence interval 0-4—1-8). This study was done in the same population and with the same methods as a case-control study on endometrial cancer in which we found a significant relationship between conjugated oestrogens and endometrial cancer.7 Other workers have investigated exogenous oestrogen use in case-control studies and have not found it to be related to ovarian cancer.8-10 Hoover et al. reported 8 cases of ovarian cancer in an oestrogen-exposed cohort where the expected number was 3.3(relative risk 2.4, 95% confidence interval 1-0-4.4). All the patients were at risk of ovarian cancer in that they had at least one ovary. The person-years of follow-up were terminated if the patient underwent an oophorectomy. Thus, only personyears were obtained from the total population, including those ovary) were considered. The rates they applied to these personyears were obtained from the total population, including those not at risk of ovarian cancer. We do not know the prevalencerates of bilateral oophorectomy in the populations served by the three tumour registries whose incidence-rates were used by Hoover et al. However, in Rochester about 10% of the female population over 45 are without ovaries and are thus not at risk 3. Criteria for a Recommended Standard. Occupational Exposure to Inorganic Arsenic: New Criteria. Center for Disease Control, 1975. 4. Smith, T. J., Peters, J. M., Reading, J. C., Castle, H. C. Am. Rev. resp. Dis. 5. 6.
1977, 116, 31. Graft, W. T., Lyon, J. L. Am. J. Epidemiol. 1977, 106, 23. Haenszel, W., Loveland, D. B., Sirkin, M. R. J. nat. Cancer Inst. 1975, 28, 947.
on
7. 8. 9. 10.
McDonald, T. W., and others Am. J. Obstet. Gynec. 1977, 127, 572. West, R. O. Cancer, 1966, 19, 1001. Wynder, E. L., and others, Cancer, 1969, 23, 352. Lau, H. U., and others, Arch. Geschwulstforsch. 1977, 47, 57.
