Photo: Iron ore pellets. The overall objective of the Minnesota Taconite Worker Health Study was to determine whether dust-related lung disease might be related to working in the taconite industry.
On Friday in Mountain Iron, Minnesota, in the heart of the state’s Iron Range, University of Minnesota researchers confirmed an association between time spent working in the taconite industry and an increased risk of contracting mesothelioma, an association evident across Minnesota’s Iron Range. Researchers also found that air quality in communities surrounding taconite mines is cleaner in terms of particulates than air found in Minneapolis.
They’ve also found that current occupational exposure to dust from taconite operations is generally within safe exposure limits.
The updated results come as the Taconite Workers Health Study, a multi-pronged research initiative funded by the state of Minnesota, winds down later this year. The Minnesota Legislature commissioned the $4.9 million project in 2008, after data from the Minnesota Cancer Registry revealed an apparent excess of cases of mesothelioma in Iron Range workers. The mesothelioma deaths only occurred in men working in the taconite industry.
The University of Minnesota School of Public Health partnered with the Medical School and the Natural Resources Research Institute at the University of Minnesota Duluth on the project.
“This is a landmark study for Minnesota and the Iron Range,” said John Finnegan, Ph.D., dean of the School of Public Health. “Our goal was to begin to answer questions around how mining and taconite processing have impacted the health of Minnesotans. These studies have started to uncover those answers.”
An examination of increased rates of mesothelioma
Mesothelioma, a fatal cancer of the lining of the lung, is mainly caused by prolonged exposure to asbestos particles in the air, linking the disease to occupations that used the material in the past.
The Minnesota Department of Health originally established a relationship between working in the iron mining industry and an increased risk for mesothelioma in the 1990’s/early 2000’s. Past University of Minnesota research has also reported the risk for mesothelioma in iron mining workers to be around three times higher than in Minnesotans not working in the industry.
As a result, University of Minnesota researchers have looked for explanations for the increase and found that for every year worked, the risk for mesothelioma went up around three percent. Researchers have wanted to determine whether or not cumulative exposure to fiber types within the family of elongated mineral particles (EMPs) present in the dust from taconite operations could account for this increase. The types of EMPs involved in iron ore mining have not been previously linked to increased mesothelioma risk. As these exposures were examined, researchers did identify a potential link between cumulative exposure to workplace EMPs and mesothelioma in taconite workers. However, the link is not felt to be certain.
As a result, the researchers cannot say with assuredness that dust from taconite operations causes mesothelioma. Further data analysis in this area will continue in the coming months.
“One important finding of the work to date is that the risk of contracting mesothelioma is higher across the entirety of the Range among people who worked longer in the industry, said Jeff Mandel, M.D., M.P.H., a School of Public Health environmental health expert and principal investigator of the study. “Unfortunately, there is minimal information on exposure to other sources of asbestos, a specific type of EMP known to cause mesothelioma, which they may have experienced outside of iron ore processing. It is something that we want to continue to look at, if at all possible.”
Taconite worker mortality
In addition to mesothelioma, within the Taconite Workers Health Study researchers researchers assessed causes of death among people born after 1920 who spent time in the iron mining industry in Minnesota. This study includes people working in the taconite industry and the former hematite industry.
The causes of death in taconite workers (when compared to Minnesota averages) were higher than expected for three important diseases: mesothelioma, lung cancer and heart disease. Causes of deaths from all three were higher than expected across the Iron Range and not in one particular location.
Although working in the taconite industry increases a person’s lifetime risk of mesothelioma, the increase equates to a small risk of actually developing the disease. Mesothelioma is still a very rare disease.
Because taconite workers have higher rates of death than their counterparts for all types of cancer combined and heart disease, it also appears there are other health considerations impacting people living on the Iron Range and lifestyle appears to be an important factor.
Air quality assessment
University researchers can also confirm that air quality in communities surrounding the mines is better than most parts of Minnesota in terms of particulates in the air. Also, researchers found that occupational exposures to dust from taconite operations are, generally, within safe limits. In addition, spouses of taconite industry workers are also at no higher risk of contracting dust-related lung diseases than Minnesota’s broader general public.
“We’re hopeful that the results to date will allay fears that taconite dust has generated broad harm to the general public,” said Mandel. “When employers and employees both take the appropriate safety precautions to curtail dust exposures, potentially harmful effects from the dusts can be eliminated.
To measure air quality and potential exposure to community residents to dust generated in the mining processing, researchers from the Natural Resources Research Institute at the University of Minnesota Duluth collected and looked at air samples from across the Iron Range. This work confirmed, even though the East and West sides of the range have different geologic characteristics, that there are very low concentrations of EMPs in the air among these communities.
Challenges and study obstacles
Project researchers did encounter obstacles in this work, as gathering exposure data from within the Taconite industry was difficult to secure the further back they tried to go. They were also unable to fully document potential exposure to asbestos products that were used in the industry. Many processing facilities were constructed and maintained in a time period when asbestos was a common building and construction material, but exposures to workers were not regulated or recorded.
As part of their annual legislative report on the Taconite Workers Health Study, University researchers will recommend additional considerations should future investigations be undertaken.
About the Taconite Workers Health Study
The overall objective of the Minnesota Taconite Worker Health Study was to determine whether dust-related lung disease, including mesothelioma, lung cancer and non-malignant respiratory disease, might be related to working in the taconite industry.
The study had five main components, including 1) an occupational exposure assessment, 2) a mortality (cause of death) study, 3) cancer incidence studies of mesothelioma and lung cancer, 4) a respiratory health survey of taconite workers and spouses, assessing non-cancerous respiratory disease and 5) an environmental study of airborne particulates.
Each study component has utilized an external peer-review process with science advisory boards that have been involved in the projects since the beginning and each of the study’s five components provide a perspective that’s important to the interpretation of the overall health assessment process.