1. What happened in Libby, Montana?
Mine workers and Libby residents were exposed to asbestos released into the air due to mining operations for vermiculite ore and vermiculite processing in Libby. In addition, family members of mine workers were exposed to asbestos that workers brought home on their work clothing.
This study was based on 123 people who had lived in Libby, worked in the mines, or were family members of people who worked in the mines. This study investigated loss of lung function and damage to the lining of the lung over time in individuals exposed to Libby asbestos. Subjects in the study received medical examinations (tests and X-rays) to assess the damage to the lining of their lungs. About three-fourths of patients tested had lost lung function over time, and all showed evidence of damage to the lining of the lung. The researchers found that the amount of lost lung capacity and damage to the lining of the lung in the study population was excessive, compared to that of unexposed populations in published studies.
2. Details on the study
The intent of this study was to explore how exposure to asbestos may result in damage to the lining of the lungs and an excessive decline in lung function. However, scientists did not intend to compare statistical data from exposed and unexposed groups. Because researchers did not plan to conduct a statistical test, there was no need to calculate study power. Instead, the authors of this study, who were medical doctors, intended to share with other medical providers their observations on the patients who had been exposed to Libby asbestos through various routes of exposure. These researchers quantified the decline in lung function and the damage to the lining of the lungs of the exposed population over time.
In this study, the exposed group included people who were exposed to asbestos from the Libby mine. However, this study is different from the type of study discussed in other sections of this website because researchers did not collect their own data from an unexposed group. Instead, the researchers/medical doctors used published data to assess lung function and damage to the lining of the lung of the unexposed group. It is likely that this study was conducted in this manner because it was the most cost- and time-effective way to analyze the data.
The researchers in this study were medical doctors who treated people that were exposed to asbestos from the Libby mine. They used data that was already available to them in their medical practice.
3. Why was a health study appropriate in Libby, Montana?
BASIC QUESTIONS FOR LIBBY, MONTANA
Yes, there was evidence of contamination of the air by asbestos from the Libby mine due to vermiculite mining and processing.
People were exposed to asbestos by breathing the air while living in Libby, Montana and working at the vermiculite mine. Family members of mine workers were exposed to asbestos brought home by workers on their work clothing.
Yes, asbestos is known to cause loss of lung function and alter the lining of the lung.
Researchers believed that levels of asbestos from the vermiculite mine in Libby, Montana were high enough to cause lung problems. Asbestos is known to cause lung cancer and mesothelioma, which is a cancer in the lining of the chest or abdomen. Asbestos is also known to cause noncancerous respiratory diseases, including asbestosis and pleural abnormalities, which both decrease lung function. Other studies have suggested that persons living near asbestos-contaminated areas may also be at risk for these health outcomes. This study helped answer the question about health risk from environmental exposures.
Yes, since loss of lung function can occur immediately after people are exposed. There is no latency period. Workers and community members were exposed to asbestos between 1963 and 1990, when vermiculite was being mined. In this study, researchers examined lung function in people after exposure.
ADVANCED QUESTIONS FOR LIBBY, MONTANA
The researchers did find some people who were right for the study. The study evaluated people who were living in Libby, who worked in the mine, or who were family members of former mine employees. However, it is important to note that there can be participation bias in the selection of study participants. This study only used data available to this medical practice. Thus, only those people who had access to these doctors and who took the initiative to see these doctors were included in the study.
Exposure was measured accurately enough for this type of study. People were considered exposed if they worked at the mine or lived with a mine worker, or if they lived or worked near the mine itself.
Disease could be accurately classified because everyone had a medical examination.
The researchers interviewed study subjects to take into account other factors that may affect lung function, such as smoking and body mass index (BMI).
This study was not designed to provide evidence of a link between asbestos and lung damage. Researchers wanted to find out how exposure to asbestos may result in an excessive decline in lung function and damage to the lining of the lungs. The
sample size of this study was limited by the available data collected by this medical practice. This particular practice served people who had been affected by asbestos exposure in Libby, Montana.
Researchers did not conduct a statistical test in this study. However, in order to determine whether this study was appropriate, researchers probably took the following steps:
- Found out how much lung function loss per year and damage to the lining of the lungs is expected in people not exposed to asbestos
- Gathered information on lung function loss and damage to the lining of the lungs from studies among workers and communities exposed to asbestos
- Estimated how much lung function loss and damage to the lining of the lungs would occur among those exposed to asbestos in Libby, Montana
Researchers probably decided that the following criteria were met:
- Lung function loss and damage to the lining of the lungs was expected to be unusually high among those exposed to asbestos in Libby, Montana compared to unexposed groups.
- There was already some evidence of excess lung function loss and damage to the lining of the lungs through clinical observations among physicians treating this population.
4. Summary table
| exposure |
Asbestos in the air due to vermiculite mining and processing |
| health outcome |
Loss of lung function and damage to the lining of lung |
| type of study |
Similar to cohort study. However, this study sampled only individuals exposed to asbestos. In order to get data for individuals not exposed to asbestos, researchers used data from unexposed individuals in published studies. |
| questions this study tries to answer |
What amount of lung function loss and damage to the lining of the lungs was observed in people exposed to Libby asbestos?Was the lung damage greater than what has been observed in populations not exposed to asbestos, according to published studies? |
| target population |
People exposed to Libby asbestos through work, being a family member of a worker, and living in Libby |
| data collected and methodology |
Medical doctors gathered data from lung function tests and X-rays of exposed patients |
| data analysis |
Data in exposed group compared to published data from unexposed populations |
strengths
of this study |
Shares observations with other medical providers on the impact of Libby asbestos on lung function loss and damage to the lining of the lungs |
limitations
of this study |
Not designed to provide more statistical evidence of link between asbestos and lung damage |