Cancer incidence and mortality in populations living near uranium milling and mining operations in grants, New Mexico, 1950-2004.

In a previous cohort study of workers engaged in uranium milling and mining activities near Grants, Cibola County, New Mexico, we found lung cancer mortality to be significantly increased among underground miners. Uranium mining took place from early in the 1950s to 1990, and the Grants Uranium Mill operated from 1958-1990. The present study evaluates cancer mortality during 1950-2004 and cancer incidence during 1982-2004 among county residents. Standardized mortality (SMR) and incidence (SIR) ratios and 95% confidence intervals (CI) were computed, with observed numbers of cancer deaths and cases compared to expected values based on New Mexico cancer rates. The total numbers of cancer deaths and incident cancers were close to that expected (SMR 1.04, 95% CI 1.01-1.07; SIR 0.97, 95% CI 0.92-1.02). Lung cancer mortality and incidence were significantly increased among men (SMR 1.11, 95% CI 1.02-1.21; SIR 1.40, 95% CI 1.18-1.64) but not women (SMR 0.97, 95% CI 0.85-1.10; SIR 1.01, 95% CI 0.78-1.29). Similarly, among the population of the three census tracts near the Grants Uranium Mill, lung cancer mortality was significantly elevated among men (SMR 1.57; 95% CI 1.21-1.99) but not women (SMR 1.12; 95% CI 0.75-1.61). Except for an elevation in mortality for stomach cancer among women (SMR 1.30; 95% CI 1.03-1.63), which declined over the 55-year observation period, no significant increases in SMRs or SIRs for 22 other cancers were found. Although etiological inferences cannot be drawn from these ecological data, the excesses of lung cancer among men seem likely to be due to previously reported risks among underground miners from exposure to radon gas and its decay products. Smoking, socioeconomic factors or ethnicity may also have contributed to the lung cancer excesses observed in our study. The stomach cancer increase was highest before the uranium mill began operation and then decreased to normal levels. With the exception of male lung cancer, this study provides no clear or consistent evidence that the operation of uranium mills and mines adversely affected cancer incidence or mortality of county residents.

A cohort study of uranium millers and miners of Grants, New Mexico, 1979-2005.

A cohort mortality study of workers engaged in uranium milling and mining activities near Grants, New Mexico, during the period from 1955 to 1990 was conducted. Vital status was determined through 2005 and standardised mortality ratio (SMR) analyses were conducted for 2745 men and women alive after 1978 who were employed for at least six months. Overall, mortality from all causes (SMR 1.15; 95% CI 1.07-1.23; n = 818) and all cancers (SMR 1.22; 95% CI 1.07-1.38; n = 246) was greater than expected on the basis of US mortality rates. Increased mortality, however, was seen only among the 1735 underground uranium miners and was due to malignant (SMR 2.17; 95% CI 1.75-2.65; n = 95) and non-malignant (SMR 1.64; 95% CI 1.23-2.13; n = 55) respiratory diseases, cirrhosis of the liver (SMR 1.79; n = 18) and external causes (SMR 1.65; n = 58). The lung cancer excess likely is attributable to the historically high levels of radon in uranium mines of the Colorado Plateau, combined with the heavy use of tobacco products. No statistically significant elevation in any cause of death was seen among the 904 non-miners employed at the Grants uranium mill. Among 718 mill workers with the greatest potential for exposure to uranium ore, no statistically significant increase in any cause of death of a priori interest was seen, i.e., cancers of the lung, kidney, liver, or bone, lymphoma, non-malignant respiratory disease, renal disease or liver disease. Although the population studied was relatively small, the follow-up was long (up to 50 yrs) and complete. In contrast to miners exposed to radon and radon decay products, for uranium mill workers exposed to uranium dusts and mill products there was no clear evidence of uranium-related disease.