Minnesota Mesothelioma by the Numbers: Taconite, Fiberboard, and the Iron Range

Minnesota’s mesothelioma story runs through two landscapes: the Iron Range in the northeast, where taconite miners extracted low-grade iron ore for decades, and the paper and fiberboard towns around Duluth and Cloquet, where workers made ceiling tiles and insulation with asbestos-containing materials.

According to the Minnesota Taconite Workers Health Study, a long-running research program funded by the Minnesota Legislature, mesothelioma has appeared at roughly three times the expected rate among workers at Iron Range taconite operations compared with the general Minnesota population. A December 2025 verdict of $65.5 million against Johnson & Johnson in a Ramsey County talc case pushed the state’s litigation into national news, but the underlying epidemiology was built decades earlier on cohort studies of miners and mill workers.

What the Data Show

Minnesota’s overall mesothelioma mortality rate sits close to the national figure of roughly 1 per 100,000. In 2021, CDC data recorded approximately 69 new mesothelioma cases in the state against a population of 5.71 million, an incidence of roughly 1.0 per 100,000.

The state stands out in one subgroup. A 2022 Morbidity and Mortality Weekly Report from the CDC identified seven states, including Minnesota, where the age-adjusted mesothelioma death rate for women aged 25 and older exceeded 6 per million between 1999 and 2020. The other six were Louisiana, Maine, Montana, Oregon, Washington, and neighboring Wisconsin.

The Iron Range and the Taconite Workers Health Study

The Iron Range stretches across northeastern Minnesota through towns like Hibbing, Virginia, Eveleth, and Silver Bay. Reserve Mining Company’s taconite operation at Silver Bay and sister plants across the range employed tens of thousands of workers through the second half of the 20th century.

In 2008, the Minnesota Legislature funded the Taconite Workers Health Study, a collaboration among the Minnesota Department of Health, the University of Minnesota, and the National Institute for Occupational Safety and Health (NIOSH).

2016 Case-Control Study

The 2016 NIOSH case-control study analyzed 80 mesothelioma cases, all male, drawn from a cohort of 68,737 taconite and hematite miners identified through the Minnesota Cancer Surveillance System and death certificates. Of the 80 cases, 57 had worked in taconite. The study compared them with 315 controls drawn from the same cohort.

The findings:

• Mesothelioma risk rose with taconite employment duration (rate ratio 1.03 per year worked, 95% confidence interval 1.00 to 1.06).
• Risk also rose with cumulative exposure to NIOSH-defined elongate mineral particles longer than 5 microns (rate ratio 1.10 per elongate-mineral-particle-per-cubic-centimeter-year).
• No elevated risk appeared among workers limited to hematite mining.
• Models adjusted for commercial asbestos exposure, but the study could not fully exclude commercial asbestos as a contributor.

2024 Follow-Up Study

A 2024 extension of the study analyzed 104 mesothelioma cases, including 71 taconite workers, against 410 controls. It confirmed the earlier finding. Risk rose with taconite years (rate ratio 1.02 per year, 95% CI 1.00 to 1.05) and with NIOSH elongate mineral particle exposure (rate ratio 1.20 per particle-per-cubic-centimeter-year). Cases showed higher median taconite years and more exposure in Zone 2, which covers Hibbing, Virginia, Eveleth, and Silver Bay.

Conwed Corporation and the Cloquet Fiberboard Plant

Conwed Corporation operated a fiberboard manufacturing plant in Cloquet, Minnesota, roughly 20 miles west of Duluth. Between 1958 and 1974, the plant used asbestos in the production of Lo-Tone ceiling tiles, which were installed in commercial and residential buildings across the United States.

In 1988, the Minnesota Department of Health screened 1,101 former Conwed workers along with 451 of their spouses. The screening found:

• 28% of workers (roughly 308 individuals) had chest X-ray abnormalities consistent with asbestos exposure, as judged by at least one expert radiologist.
• About 5% of spouses showed abnormalities, indicating household or take-home exposure at a lower level than direct workplace contact.

A 1993 follow-up publication summarized a broader state-sponsored program that screened approximately 4,500 asbestos-exposed workers in Minnesota. The Conwed cohort was the largest single facility within that program.

A 2007 Minnesota Department of Health update, prepared in collaboration with NIOSH, analyzed 58 mesothelioma cases among Iron Range taconite workers. Only three of the 58 had worked at Conwed, which ruled out the Cloquet plant as the primary cause of the taconite cohort’s mesothelioma burden.

Duluth, Superior, and Regional Shipyards

The Duluth-Superior harbor at the western end of Lake Superior supported shipbuilding and ship repair for Great Lakes freighters and ocean-going vessels transiting the St. Lawrence Seaway. Workers at Fraser Shipyards in Superior, Wisconsin, and at smaller Duluth facilities handled insulation, gaskets, pipe covering, and engine room components that contained asbestos.

In 2016, OSHA cited Fraser Shipyards for workplace hazards during the retrofit of a 690-foot Great Lakes vessel. The proposed penalties totaled roughly $1.4 million for lead and other violations, including 14 willful egregious health citations for lead levels more than 20 times the occupational limit. Asbestos hazards were among the issues identified during the work. The citations drew national attention to conditions in inland shipyards.

Who Is Most at Risk

• Taconite miners from Iron Range operations at Hibbing, Virginia, Eveleth, and Silver Bay
• Conwed Cloquet workers and their household members from the 1958 to 1974 production period
• Paper mill workers at facilities in Cloquet, International Falls, and Sartell
• Shipyard workers at Fraser and other Duluth-Superior harbor facilities
• Power plant workers at Northern States Power (now Xcel Energy) generating stations including Allen S. King and Sherco
• Minneapolis-Saint Paul construction tradespeople, including insulators, pipefitters, and electricians who worked in pre-1980 buildings
• 3M production workers at Minneapolis-Saint Paul manufacturing facilities

Statute of Limitations

Minnesota gives mesothelioma plaintiffs six years from the date of discovery under Minnesota Statute 541.05. That is longer than the two-year deadline in Pennsylvania or Wisconsin’s three-year window. Wrongful death claims must be filed within three years under Minnesota Statute 541.07. The discovery rule starts the clock at diagnosis or at the point when a person reasonably should have connected the illness to asbestos, not at the date of exposure.

The Minnesota Supreme Court applied the six-year personal injury limit in Palmer v. Norlift (2020), holding that a January 2012 diagnosis linking mesothelioma to asbestos started the clock and that a 2018 filing fell outside the window.

Legal Options for Minnesota Workers

Minnesota’s asbestos trust fund claims matter most to taconite miners, fiberboard workers, and construction tradespeople whose exposure sources trace back to bankrupt manufacturers. Minnesota verdicts and settlements reflect the state’s mix of occupational mining exposure and consumer talc litigation, including the record $65.5 million Ramsey County verdict against Johnson & Johnson in December 2025.