On the Tremolite Trail in Minneapolis
Tannie Eshenaur, MPH, Environmental Health Division, Minnesota Department of Health, St. Paul, Minnesota

The Western Mineral Products plant operated two expansion furnaces to exfoliate the ore into lightweight vermiculite products. Ore shipment records dating back to 1958 show that the mine received >8,500 tons of ore in 1959; by 1988, that amount had decreased to <1,000 tons. The ore was gravity-fed into the furnaces at a rate of up to 2,400 pounds per hour, then heated to a temperature of 2,000°F (1,093°C), causing water trapped in the ore to expand or "pop." The expanded vermiculite was then separated from any unexpanded material, known as stoner rock. The finished product was cooled, dampened, and bagged, or further screened into several size ranges for specific applications.

The unexpanded stoner rock was piled outside the plant building and labeled "free crushed rock." Local residents were encouraged to take the rock to use on their own properties for fill material. The warm piles of stoner rock waste were a favorite place for neighborhood children to play. In 1989, the facility closed, the furnaces and all equipment were removed, and the site was sold. The building is now used by several small businesses.

According to mineral analyses conducted by W.R. Grace, the stoner rock contained between 2% and 10% friable tremolite asbestos. In February and April 2000, the U.S. Environmental Protection Agency (EPA) and the Minnesota Pollution Control Agency (MPCA) collected surface soil samples at the site as part of a national evaluation of facilities that received ore from the Libby mine. Amphibole asbestos was found at levels as high as 20% by volume, prompting further investigation. Tremolite asbestos was visible on the ground at both the site and at neighboring homes as small, grayish grains or bundles with a fibrous component.

In September 2000, EPA determined that the presence of visible tremolite asbestos in the neighborhood was an immediate health threat to area residents. EPA contractors inspected properties and removed visible surface contamination from the yards and driveways of >20 homes. Emergency response action continued in summer 2001. EPA is also planning remediation of the Western Mineral Products industrial property.

In the 1970s, the plant operated 24 hours per day, 5 days per week, and typically employed 10-20 people. The operation was described as "very dusty." Before 1971, minimal pollution control equipment was in place. Bag-house filters were installed in 1972. In the 1970s, airborne asbestos fiber concentrations inside the building often exceeded existing Occupational Safety and Health Administration (OSHA) limits. Dust permeated the building, and concentrations above OSHA limits were found even in nonwork areas such as the lunch room. Former plant workers have been notified by letter about the possible health risks resulting from exposure to asbestos. Through an agreement with W.R. Grace, these workers are being offered health screening in two area clinics.

The Minnesota Department of Health (MDH), under a cooperative agreement with ATSDR, completed an initial health consultation identifying health concerns related to asbestos exposure from the Western Mineral Products site. The health consultation described exposures of former workers, family members of workers, and area residents. Some residents used the free crushed rock in their yards or played in the rock piles as children. Residents living near the plant might have been exposed to airborne fibers from the plant's three vent stacks on or near the roof of the four-story building. In the late 1960s and early 1970s, area residents complained that dust from a roof vent was settling on lawns, on cars, and inside homes. MDH staff members are now focusing on better quantifying exposure estimates for residents. An air dispersion model of plant emissions was developed with help from scientists at MPCA. Information from the Libby site will also be critical to the risk assessment process.

Community health education activities have had an important role in communicating information to neighbors of the site and to former workers at the plant. MDH has maintained contacts with community leaders and neighborhood associations to ensure that people are informed of activities at the site and to respond to the community's concerns. In addition, MDH organized a committee of local health professionals to assist in providing local physicians with guidance for meeting the medical care needs of the residents.

Finally, MDH has begun an investigation to identify and characterize individual asbestos exposures among community members. Six field staff members are visiting neighbors who live within a ½-mile radius of the plant to gather information about household residents and offer property inspections. Former residents of the area and others who might have been exposed are also being identified and will be interviewed by telephone. In the future, MDH hopes to conduct follow-up health investigations to determine any health outcomes that might have occurred as a result of vermiculite processing in Northeast Minneapolis.

A comprehensive effort is under way to address the needs and concerns of the community at the Western Mineral Products site and to mitigate the ongoing threat to the health of the community.

The risk for asbestos-related disease depends on many factors, including type of asbestos fiber, level of exposure, duration of exposure, and smoking history of the person. The latency period for these diseases ranges from 10 years to 30 years. Following is a description of the three known asbestos-related diseases.

• Asbestosis is a serious, chronic, noncancerous respiratory illness. Asbestosis causes scarring of the lung tissues, making breathing more difficult as the scarring increases. The disease can lead to heart failure. Asbestosis is usually caused by chronic occupational exposure to asbestos. No effective treatment exists for asbestosis, and the disease might be disabling
  or fatal.
  
  

• Lung cancer accounts for about 50% of all asbestos-related diseases. Studies have shown that asbestos workers are five times more likely to develop lung cancer than are workers who are not exposed to asbestos. In addition, asbestos workers who smoke are 50 to 90 times more likely to develop lung cancer in comparison with nonsmokers who are not exposed to asbestos. In the United States, only 14% of patients with lung cancer survive for 5 years (1).

• Mesothelioma is a cancer of the lining of the chest or abdomen. Mesothelioma is a rare cancer—about 200 cases are diagnosed in the United States each year. Mesothelioma is incurable and is usually fatal within 1 year after diagnosis. The majority of mesotheliomas are caused by exposure to asbestos. Mesothelioma accounts for 10% to 18% of deaths among workers exposed to asbestos.

Reference
1. DeVita VT, Hellman S, Rosenberg SA, editors. Principles and practices of oncology. 6th edition. Philadelphia: Lippincott Williams & Wilkins; 2001.

However, evidence of asbestos exposure (such as pleural plaques) does not mean that asbestos-related disease must follow. Most importantly, the person exposed can help reduce the risk for a more serious illness by quitting smoking. Smoking exponentially increases the risk for health problems such as cancer among people exposed to asbestos. The Breathe Easy information was created to help community members develop a sense of self-empowerment so that even if they were diagnosed as having a disease such as asbestosis, they still could have some control over their condition. Community members can help manage their conditions with simple common-sense activities.

The Breathe Easy information was introduced in a well-attended health information session during a comprehensive community conference in Libby. The information was later distributed in the local clinic at which the >6,000 participants in the testing program were evaluated. "Breathe Easy: Ten Tips for Taking Care of Yourself if You Have Asbestos-Related Disease" provided important information to members of the community by targeting one of their fears: a complete lack of control over their own health.

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Coming Soon: Asbestos Web Site 

A new Web site devoted to asbestos will soon be available on the Internet. The site will include links to ATSDR documents and information on asbestos.

Watch for it on the ATSDR Web page: www.atsdr.cdc.gov/.

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Case Studies in Environmental Medicine

ATSDR's Case Studies in Environmental Medicine: Asbestos Toxicity is being updated in winter 2002. It will be available on the Internet at www.atsdr.cdc.gov/HEC/CSEM/ and in print (see contact information).

The case studies series is a key part of the agency's health professional education strategy. The case studies are available free of charge to educate and inform health processionals and the general public about hazardous substances. The case studies are accredited and offer continuing medical education (CME), continuing nursing education (CNE), and continuing education unit (CEU) credits. In the near future, the case studies will also offer continuing health education specialist (CHES) credits.

Contact Information
To order a print version of the revised Case Studies in Environmental Medicine: Asbestos Toxicity when it becomes available, write to or fax the Continuing Education Coordinator, ATSDR/DHEP, 1600 Clifton Road, NE (MS E33), Atlanta, GA 30333; fax: 770-488-4178.

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This page last updated on May 2, 2002
Contact Name: Wilma López/ WLópez@cdc.gov