Understanding Lung Cancer Risk Among Navajo Former Uranium Miners

Abstract

"<bold> Problem statement:</bold>" Historically, uranium mining caused many Navajo to develop lung cancer, but little is known about the contribution of uranium mining to lung cancer cases diagnosed in years following the demise of that industry. <bold>Background: </bold> Results from two previous case-control studies demonstrated that a high proportion (67%-72%) of Navajo lung cancers diagnosed between 1969-1993 were attributable to employment in the uranium industry. In one study, approximately 72% of Navajo lung cancers occurred in uranium miners with little to no exposure to tobacco. The smoking prevalence among American Indians living in the Southwest has been observed to be lower than American Indians living in the Northern Plains and the general U.S. population. More recent studies have observed that younger age tribal members and males living in the Southwest have higher rates of smoking. Such changes in smoking prevalence may affect lung cancer rates despite a moratorium on uranium mining in the Southwest. <bold>Methods: </bold> We conducted a population based case-control study to characterize the association between employment in the uranium industry and lung cancer during the period 1994-2006. Eligible subjects were all Navajo residents of New Mexico and Arizona. Cases were diagnosed with lung cancer and controls had a confirmed cancer diagnosis other than lung or kidney during the study period. Multivariate logistic regression was used to assess the association between employment in the uranium industry and lung cancer, adjusted for age and smoking. <bold>Results: </bold>Navajo lung cancer cases had greater odds than controls to have a history of employment in the uranium industry (Odds Ratio=3.9; 95% CI: 2.08, 7.36). Approximately 31 percent of lung cancer cases were employed in the uranium industry. The mean age of cases and controls was 70.1 years (SD=13.1). Males made up approximately 68% of both cases and controls. A higher proportion of cases compared to controls were deceased during the study period 1994-2006, 53.1% and 32.8%, respectively. <bold>Conclusions: </bold>Employment in the uranium industry continued to influence lung cancer incidence among the Navajo well into the 21st century. However, the proportion of lung cancers attributable to uranium mining has diminished over time. <bold>Benefits of research: </bold>This study will help the Navajo Nation better understand the risks associated with uranium mining.