Researchers say taconite’s link to high rates of mesothelioma may be hard to prove
A nearly $5 million study of taconite miners in Minnesota’s Iron Range may never prove a link between high rates of mesothelioma and the taconite industry.
The Minnesota Taconite Workers Health Study has found that at least 82 Iron Range miners have died in recent years from mesothelioma, a rare and invariably fatal lung disease caused by exposure to asbestos fibers. And the $4.9 million research initiative, funded by the State of Minnesota, has confirmed a 300 percent higher rate of mesothelioma on the Iron Range than the general population in Minnesota.
But Jeff Mandel, an associate professor at the University of Minnesota’s School of Public Health and the lead researcher in the study, told the Duluth News Tribune that the higher rates of the deadly disease may be attributable to previous exposure in another setting.
“It could be we don’t see any relationship to the workplace,” Mandel said.
A team of researchers from the University of Minnesota team has been investigating the occupational health hazards faced by workers in the taconite industry since 2008. The study aims to determine the extent to which exposure to dust from taconite affects the health of workers and their spouses, with specific focus on respiratory diseases and illness associated with silica and asbestos exposure.
Taconite is a low-concentrate iron ore that has been mined and processed in Minnesota since the 1950s.
In a report released this week, the study team says Iron Range workers have lung cancer rates that are about 20 percent higher than the general population, and an 11 percent higher incidence of heart disease.
But it’s not clear to researchers if the higher rates were caused by smoking or other habits linked to those health problems. The News Tribune says the researchers are not finding much evidence of asbestos-size mineral fibers, which is the only cause of mesothelioma, a disease that attacks the lining of the lungs, heart and abdomen.
Now, the newspaper reports, researchers are focusing on shorter fibers, called elongated mineral particles, that may or not be asbestos.
Researchers say they will continue to look at whether the minerals released when low-grade iron ore is mined and processed into taconite pellets is causing lung disease. But exposure to toxic fibers may have also come from previous jobs held by the miners, such as in the ship building industry, on board asbestos-laden Navy ships or while handling asbestos molds or insulation in taconite plants.
The study of health issues of iron mining workers began in the early 1980s, when the University of Minnesota School of Public Health created a roster of 70,000 people who worked in the Iron Range for at least a year before 1982. In the late 1990s, the Minnesota Department of Health, which had begun monitoring cancer rates in Iron Rangers, identified an increase in mesothelioma cases compared to expected cases for the northeastern part of Minnesota.
The study has five components: an occupational exposure assessment to determine the source of the asbestos; a mortality study to investigate the cause of death for Iron Range workers; a cancer incidence study to determine if taconite mining is related to higher rates of certain cancers; a respiratory health survey to evaluate current workers and spouses for lung diseases; and an environmental study of airborne particulates to assess asbestos levels on the range.
Mandel said the team should have results from each of the five components of the research within four to five years.