Reconstructing Historical Exposures to Respirable Dust and Respirable Silica in the Taconite Mining Industry for 1955-2010

Yuan Shao, Jooyeon Hwang, Richard F. Maclehose, Bruce H. Alexander, Jeffrey H. Mandel, Peter C. Raynor, Gurumurthy Ramachandran

Research output: Contribution to journalArticlepeer-review


The goal of this study was to reconstruct the historical respirable silica (RS) and respirable dust (RD) exposures of workers in the Minnesota taconite industry from 1955 to 2010 as part of several epidemiological studies for assessing the association between exposure to components of taconite dusts and the development of respiratory diseases. A job-exposure matrix (JEM) was developed that uses 9127 RS and 19 391 RD occupational hygiene historical measurements. Historical RS and RD data were extracted from several sources and were grouped into seven mines and then into eight departments [Concentrating, Crushing, Janitor, Mining, Office/control room, Pelletizing, Shop (mobile), and Shop (stationary)]. Within each department, we applied a two-level random-intercept regression model which assumes that the natural log of Y (RD or RS concentration) changes over time at a constant rate. Among all predicted RD and RS values, we found that larger RD values were located in the following departments: Crushing, Concentrating, Pelletizing, and Shop (mobile). Larger RS values were located only in either Crushing or Shop (mobile). The annual rates of change for historical RD and RS exposures were between -3.3 and 3.2%. The silica percentage in the dust varied by mine/department with the highest value of 29.3% in Mine F (Crushing) and the lowest value of 2.1% in Mine B (Pelletizing). The predicted historical RD and RS arithmetic mean exposures ranged between <0.075 and 3.14 mg m-3, and between <0.005 and 0.36 mg m-3, respectively. The result of this study is a JEM by mine, department, and year for RD and RS for epidemiological studies.

Original languageEnglish (US)
Pages (from-to)459-471
Number of pages13
JournalAnnals of Work Exposures and Health
Issue number4
StatePublished - May 1 2022

Bibliographical note

Funding Information:
This research was made possible by funding under NIOSH 1R01OH010418-01A1-Respiratory Diseases and Exposure to Elongated Mineral Particles in Taconite Ore. We would also like to thank the State of Minnesota for funding the original TWHS study.

Publisher Copyright:
© 2021 The Author(s).


  • job-exposure matrix (JEM)
  • respirable dust
  • respirable silica
  • retrospective exposure reconstruction
  • taconite mining

PubMed: MeSH publication types

  • Journal Article
  • Research Support, U.S. Gov't, P.H.S.


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