The Community Environmental Health Project in Libby, Montana

An Overview of ATSDR Assistance to an Asbestos-Exposed Community
Jeffrey A. Lybarger, MD, Office of the Assistant Administrator, with B. Kathy Skipper, MA, Office of Policy and External Affairs

From 1924 through 1990, vermiculite ore was mined and milled from Zonolite Mountain in Libby, Montana. This ore was contaminated with tremolite asbestos. Tremolite asbestos is an asbestiform mineral that causes adverse health effects when inhaled (see story on page 6). In fall 1999, the Agency for Toxic Substances and Disease Registry (ATSDR) was asked by the U.S. Environmental Protection Agency (EPA) and Senator Max Baucus (MT) to determine the extent of asbestos-related exposures in the Libby area and to address community concerns.

ATSDR collaborated with other agencies to develop a Libby Community Environmental Health Project. Major components of the project include the following:

• A testing program, under which 6,149 people were evaluated for evidence of possible asbestos-related abnormalities. The first round of testing occurred in 2000. Initial results released in summer 2001 showed that 159 (48%) of 328 former W.R. Grace employees had pleural abnormalities. Twenty-four percent of test participants who reported exposure to asbestos through six or more potential pathways had pleural abnormalities. Six (5%) of 122 participants who reported no apparent exposure to asbestos had pleural abnormalities. During summer 2001, an additional 1,158 people were tested.
  
  

• A mortality review, which compared death rates for residents of the Libby area with those in Montana and the United States for selected diseases associated with exposure to asbestos. The review found that for the 20-year period evaluated (1979-1998), asbestosis mortality in the Libby area was approximately 40 times higher than in the rest of Montana and 60 times higher than in the rest of the United States.

• A CT (computed tomography) scan study is evaluating whether CT scans would provide a significant improvement over evaluations using chest radiographs in identifying lung problems associated with asbestos exposure. CT scans are sensitive radiographs that are analyzed by computer. Scans deliver a much greater exposure to radiation than standard radiographs do.

• A Toxicological Profile for Tremolite Asbestos, which describes the health effects of exposure to tremolite asbestos. The ATSDR peer-reviewed toxicological profiles identify and review the key literature that describes a hazardous substance's toxicologic properties.

• A case series, which involves a review of medical records, radiographs, and CT scans of selected patients with asbestos-related disease. The case series will help to increase knowledge about the more severe, clinical aspects of asbestos-related illness, especially among people with only environmental (not work-related) exposure to asbestos.

• An asbestos-related disease registry is planned. The registry will list individuals with asbestos-related disease or those individuals at high risk for asbestos-related disease because of their exposure to asbestos. Information on any new therapies or diagnostic tools developed will be shared with persons listed in the registry. The registry will also be used to help policy makers and researchers prepare for treating persons who have asbestos-related illnesses.

• Community education at Libby has been a cooperative endeavor. EPA, ATSDR, and state and local governments have provided education on asbestos, asbestos exposure, and asbestos-related diseases. An "ask EPA" column in the local newspaper is also used for ongoing education.
  
  
• Health provider training included a grand rounds presentation (a) to review the epidemiology and pathogenesis of nonmalignant lung disease from exposure to tremolite asbestos and (b) to discuss the clinical manifestations and diagnosis of nonmalignant asbestos-related lung diseases. Training sessions were held to review the purpose of screening evaluations for asbestos-related lung diseases and discuss appropriate diagnostic followup of screening abnormalities, identify practical approaches to medical management, and discuss education and risk communication strategies for patients with asbestos-related diseases.
  
  

ATSDR interviewed participants face-to-face to obtain information about their health, how long they had lived in the Libby area, their possible exposures to asbestos or vermiculite through work or recreation, and their smoking history. ATSDR performed a lung function test, and those participants who were 18 years of age and older also had chest radiographs.

Three radiologists, called "B readers," checked the chest radiographs for lung abnormalities and found that 994, or 18%, of the 5,590 adults tested had pleural (lining of the lungs) abnormalities. Pleural abnormalities are believed to be an indicator of exposure to asbestos. These abnormalities can be seen even with low levels of asbestos exposure. The occurrences of pleural abnormalities increased in older participants and in those who had lived longer in the Libby area. The pleural abnormality rate for groups within the United States who have had no known asbestos exposure ranges from 0.2% to 2.3%.

Lungs Affected by Asbestosis

A key finding was that those participants with higher levels of exposure had higher occurrences of pleural abnormalities. For example, 159 (48%) of 328 former W.R. Grace employees had pleural abnormalities. Of those participants who reported exposure to asbestos through six or more potential pathways (through household, employment, or recreational contact), 24% had pleural abnormalities. Of those tested who reported no known exposure to asbestos, 5% had pleural abnormalities.

Three risk factors were strongly associated with participants having pleural abnormalities:

1. Former W.R. Grace/Zonolite workers. The risk of having a pleural abnormality was almost 8 times greater for former W.R. Grace/Zonolite workers in comparison with people of the same age who did not work for the company.
   
   
2. Household contact with a W.R. Grace/Zonolite worker. The risk was 3.3 times greater for females who had household contact with these workers in comparison with women who had no household contacts with these workers.
   
   
3. Males. The risk for men was 5 times greater than for women.

Both children and adult participants were offered spirometry, or lung function, tests. Test results were interpreted by an on-site pulmonologist. Being a current smoker was the strongest risk factor for moderately to severely restricted air flow in and out of the lungs. Restricted breathing capacity was found in 5.7% of former W.R. Grace workers. No children tested had restricted lung function.

Participants and their designated primary care physicians have been notified of the test results. An electronic archive of the chest radiographs will be set up at Montana's state health department.

The Agency for Toxic Substances and Disease Registry (ATSDR), in cooperation with the Montana Department of Public Health and Human Services, analyzed mortality statistics for Libby, Montana, for the 20-year period from 1979-1998. Death certificate data were reviewed to generate an accurate representation of mortality potentially associated with historical exposure to asbestos in the Libby community. Underlying causes of death recorded on death certificates included nonmalignant respiratory diseases, lung cancer, mesothelioma, digestive cancers, and diseases of pulmonary circulation.

The decendents' places of residence at time of death were mapped using a geographic information system (GIS). Baseline population estimates and age stratification data were derived using GIS to generate standardized mortality ratios. Mortality statistics from the underlying causes of death were compared with mortality statistics for the state of Montana and the overall U.S. population.

For the 20-year period reviewed, mortality in Libby due to asbestosis was approximately 40 to 60 times higher than expected. Mortality resulting from mesothelioma was also elevated. However, it was difficult to precisely evaluate the degree to which mortality attributed to mesothelioma was elevated, because statistics on this extremely rare cancer are not routinely published at the state and national levels. This initial mortality review was released on December 12, 2000; personnel in the Montana Department of Public Health and Human Services' Office of Vital Statistics subsequently uncovered more applicable deaths in the Libby area. Information about these decedents is being included in a reanalysis of the data. The reanalysis will include an evaluation of potential pathways of exposure (occupational vs. nonoccupational). The reanalysis will also more accurately portray mortality in Libby as well as delineate the differences in risk among individuals who worked in the vermiculite mining and milling operation compared with community members who lived near these activities. 

In 1881, miners searching for gold unearthed a micalike material from an area outside of Libby, Montana. At the time, they did not know what they had uncovered. It was not until 1919 that Edward Alley, a local businessman from Libby, discovered the unique properties of this material. While he was walking through an abandoned mine, his torch contacted the surface of the mine, resulting in an expansion or "popping" of the ore into a material later known as vermiculite. This unique material was marketed for many uses, such as loose-fill insulation, a fertilizer carrier, a soil conditioner, and an aggregate in many products such as gypsum wall board and numerous construction products.

Vermiculite ore from Libby was mined beginning in the 1920s. In 1963, W.R. Grace purchased the mine and expanded operations. During the 1960s-1980s, millions of tons of vermiculite ore were shipped to 30 states and six foreign countries. The ore from Libby was contaminated with asbestos, and evidence of adverse health effects began to appear in workers employed at the mine, mill, and refining processes in Libby. Investigations in the 1980s found that those workers had increased rates of asbestosis, mesothelioma, and lung cancer. At a		Vermiculite Ore
fertilizer plant in Marysville, Ohio, that received ore from Libby, asbestos-related lung abnormalities were identified among workers. During early mining operations in Libby, airborne levels of asbestos were measured at levels >100 fibers per cubic centimeter (f/cc) of air. In downtown Libby, concentrations of airborne asbestos exceeded the federal Occupational Safety and Health Administration (OSHA) permissible exposure limit of 0.1 f/cc.

In 2000, as the U.S. Environmental Protection Agency (EPA) initiated clean-up actions in Libby, and as the Agency for Toxic Substances and Disease Registry (ATSDR) began health screening of former workers and residents, an effort was under way throughout the United States to investigate facilities that received asbestos-contaminated ore from the W.R. Grace mine. Approximately 300 sites across the country were identified as possible recipients of the vermiculite ore. Working with EPA, ATSDR has begun to evaluate all of these sites to determine whether asbestos contamination is present at levels that pose a public health risk.

Of all types of vermiculite processing facilities, exfoliation plants are most likely to have resulted in the greatest amounts of environmental contamination and exposure. Exfoliation plants heated the vermiculite ore to approximately 2,000°F (1,093°C), creating the expanded vermiculite used for a variety of products, including loose-fill insulation in homes. Significant concentrations of asbestos fibers might have been released into communities near these plants through stack emissions. ATSDR is evaluating past exposure to airborne asbestos around these plants by looking at asbestos-related disease rates.

Current exposure to asbestos-contaminated vermiculite is also being assessed at the facilities that received Libby vermiculite ore. EPA and ATSDR are working together to gather information on these sites. Where appropriate, environmental sampling of the air and soil is being conducted to assess the current level of exposure around former vermiculite facilities. In addition, the National Institute for Occupational Safety and Health (NIOSH) is evaluating active vermiculite facilities that are receiving ore from mines other than Libby.

Collecting environmental data is only the first step in the identification process. Current exposure models used to assess risk to asbestos in air and soil do not incorporate much of the knowledge acquired during the last 15 years. Much has been learned regarding asbestos fiber types and biologic mechanisms. This information needs to be incorporated into any future exposure models to give meaningful information regarding risk. In addition, environmental sampling methodologies must be developed to best measure and collect the kind of information that will be useful to health professionals who are assessing the data. The ultimate goal of this effort is to identify sites where unacceptable exposures to asbestos might be occurring, so that exposure at these sites can be mitigated to a safe level. ATSDR will work with EPA and other federal agencies to serve affected populations by providing health education and meeting other needs as appropriate.

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This page last updated on October 24, 2003
Contact Name: Wilma López/ WLópez@cdc.gov