Taconite Worker Exposures and Associations with Ischemic Heart Disease and Chronic Obstructive Pulmonary Disease Mortality

Abstract

Background: Taconite mining (i.e., iron mining) began in the late 1800s along the Mesabi range in Minnesota and currently produces the largest amount of iron ore within the United States. Taconite mining and processing results in potential exposures to respirable dust and silica. Previous population and occupational studies have demonstrated potential associations between respirable dust and silica with chronic obstructive pulmonary disease (COPD) and ischemic heart disease (IHD). Additionally, a previous mortality study among Minnesota taconite workers indicated that IHD mortality was elevated. Although COPD was not elevated in the previous mortality study, IHD and COPD often occur as comorbidities. However, using only the underlying cause of death on a death certificate may result in an under-estimation of the COPD mortality burden particularly in the presence of co-morbidities such as IHD. Objective: The overall objective of this research is to evaluate the impact of occupational exposures in taconite mining (i.e., employment duration, respirable dust, and respirable silica) on IHD and COPD mortality among a cohort of taconite miners in Minnesota. Specifically, to determine whether the underlying causes of death due to both COPD and IHD were under-or over-estimated, respectively, this dissertation investigated IHD and COPD mortality among taconite workers using a multiple cause of death analysis. Further, given the potential relationship between employment duration, respirable dust and respirable silica with IHD and COPD, this dissertation also explored the association between employment duration, respirable dust, and respirable silica with IHD and COPD, respectively, among a cohort of taconite miners.