Respiratory Diseases And Exposures To Taconite Dust Components

Abstract

The primary research question addressed in this work is whether long-term on-site exposure to non-asbestiform EMP contributes to the development of mesothelioma and lung cancer observed in the taconite mines. If so, which EMP exposure metric (what size range of the study EMP) is most associated with the mesothelioma cases among taconite worker population. The dissertation has a total of six main chapters. The first chapter includes a brief history of Minnesota iron mining industry, mining related health concerns, and the resulting Minnesota Taconite Worker Health Study (TWHS) conducted from 2008 to 2013. It summarizes the main findings of this previous study and the new research directions after this study. The primary research hypotheses and four associated specific aims are described. Chapter 2 describes the exposure reconstruction process for historical respirable silica (RS) and respirable dust (RD) exposures of workers in Minnesota taconite industry from 1955-2010 in specific aim 1. This chapter also discusses how the historical dust exposure changed over time in each mine-department combination. Chapter 3 addresses specific aim 2, and describes how the historical EMP exposure levels are predicted using EMP data and the time-trends obtained from specific aim 1. Chapter 4 describes the mathematical modeling approach for deriving numerical conversion factors (CFs) between EMP of different size ranges. This chapter also discusses how these CFs are important in the development of alternative dimension-specific EMP JEMs starting from the existing NIOSH-EMP based JEM developed in specific aim 2. This work addresses specific aim 3. Chapter 5 describes a mesothelioma case-control study conducted using an updated study cohort and new dimension-specific EMP JEMs developed in specific aim 3. The chapter addresses specific aim 4 and provides answers to the primary research question of this dissertation. In the last chapter, I summarize the overall conclusion and propose some future research directions.