A Review of Asbestos and Related Consequences

Release Date: July 1, 2010

Expiration Date: July 31, 2012

FACULTY:

Carmela Avena-Woods, PharmD, CGP
Assistant Clinical Professor of Clinical Pharmacy Practice
St. John’s University College of Pharmacy and Allied Health Professions

Queens, New York
Community Pharmacy Practice Specialist
Walgreens
Garden City, New York

Olga Hilas, PharmD, MPH, BCPS, CGP, FASCP
Assistant Clinical Professor of Clinical Pharmacy Practice
St. John’s University College of Pharmacy and Allied Health Professions

Queens, New York
Clinical Pharmacy Coordinator
Internal Medicine/Geriatrics New York Presbyterian Hospital/Weill

Cornell Medical Center
New York, New York

FACULTY DISCLOSURE STATEMENTS:

Drs. Avena-Woods and Hilas have nothing to disclose.

U.S. Pharmacist does not view the existence of relationships as an implication of bias or that the value of the material is decreased. The content of the activity was planned to be balanced, objective, and scientifically rigorous. Occasionally, authors express opinions that represent their own viewpoint. Conclusions drawn by participants should be derived from objective analysis of scientific data.

ACCREDITATION STATEMENT:

Pharmacy
acpePostgraduate Healthcare Education, LLC is accredited by the Accreditation Council for Pharmacy Education as a provider of continuing pharmacy education.
UAN: 0430-0000-10-022-H01-P; 0430-0000-10-022-H01-T
Credits: 2.0 hours (0.20 ceu)
Type of Activity: Knowledge

TARGET AUDIENCE:

This accredited activity is targeted to pharmacists and pharmacy technicians. Estimated time to complete this activity is 120 minutes.

Exam processing and other inquiries to:
CE Customer Service: (800) 825-4696 or cecustomerservice@jobson.com

DISCLAIMER:

Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development. The information presented in this activity is not meant to serve as a guideline for patient management. Any procedures, medications, or other courses of diagnosis or treatment discussed or suggested in this activity should not be used by clinicians without evaluation of their patients’ conditions and possible contraindications or dangers in use, review of any applicable manufacturer’s product information, and comparison with recommendations of other authorities.

GOAL:

To enhance practitioner understanding of the nature, history, and consequences of asbestos exposure.

OBJECTIVES:

After completing this activity, participants should be able to:

  1. Discuss the origin of asbestos and its impact on health.*
  2. Identify the risk factors and etiology of asbestos-related diseases.*
  3. Differentiate between various asbestos-related diseases.*
  4. Provide information on the current regulation of asbestos.*
  5. Recognize and prevent potential exposure to asbestos.*

*Also applies to pharmacy technicians.


Asbestos is a natural fibrous mineral that has been mined and used for centuries. Its use and discovery can be traced back to Finland (approxi mately 2500 BC), where it was used to reinforce clay utensils and pottery.1 It was first used in the United States in the early 1900s to insulate steam engines.2 Asbestos was increasingly mined and used for its desirable fire-retardant and insulating properties, which proved to be a particularly advantageous and valuable component for construction materials.3 Due to its resistance to destruction, asbestos was also heavily used in the manufacture of ceiling tiles, pipe and broiler insulations, flooring, filter papers, and resin polymers throughout the 19th and 20th centuries.4 Over the years, asbestos-containing materials were used in the construction and renovation of schools and other public buildings, primarily to fireproof, insulate, soundproof, and even decorate them. According to the Environmental Protection Agency (EPA), it was estimated that there are asbestos-containing materials in most of the U.S. primary and secondary schools as well as in 733,000 public and commercial buildings.2 Additional products used in the past that may contain asbestos and that may release fibers are soundproofing or decorative materials.5

The world production of asbestos fibers reached a maximum in 1977 with 4.8 × 106 tons being produced. After findings of health problems in those who were heavily exposed to airborne asbestos fibers began to rise in the late 1960s and 1970s, the number began to decrease significantly. Asbestos-related health problems were reported as early as 1899 by Montague Murray, a British physician who was the first to link asbestos to a case of death from a disease that was then called fibroid phthisis.6 By the year 2000, the world production of asbestos fibers had declined to 1.9 × 106.1

The word asbestos is a very common yet broad term. Asbestos actually consists of six different fibrous minerals, which are all silicates and therefore are resistant to biodegradation and have low electrical conductivity. They belong to two main mineral groups: serpentines and amphiboles. The serpentine group contains one variety called chrysotile, also known as white asbestos.1 In the past, this form was known to constitute more than 90% of the world’s asbestos production.7 The fibers of chrysotile, which makes up 95% of asbestos mined globally, are long and curly. The crystalline structure of chrysotile has been found to be stable up to approximately 550°C (1,022°F). The amphibole group consists of five varieties: anthophyllite asbestos, grunerite asbestos (amosite [brown]), riebeckite asbestos (crocidolite [blue]), tremolite asbestos, and actinolite asbestos.1 Amphibole fibers of asbestos tend to be shorter and straighter compared to chrysotile fibers.3 Although asbestos fibers are strong and flexible enough to be spun or woven into cloth, the amphibole fibers are generally found to be easily broken and are the more brittle of the two groups.

Both main groups of this mineral have no smell or taste and do not dissolve in water. Asbestos is introduced into the air and water from the degradation of natural deposits of the fibers and the wearing down of manufactured asbestos products. Due to their great durability, asbestos fibers may break down into smaller particles but do not break down into other compounds and can remain unchanged for long periods of time.8

Naturally occurring asbestos can be found in soil and is released into the air as it is disturbed by the degradation and erosion of asbestos-bearing bedrock.8 Construction and demolition work in areas where naturally occurring asbestos is found can also lead to the release of inhalable fibers.9 Despite health concerns, there is no set standard to measure the amount of asbestos exposure that is safe or harmful. However, it is hypothesized that the curly fibers carry a slightly lower risk of lung disease than the straight fibers.4 The shape of asbestos fibers is the property that allows them to remain in the lungs. According to the EPA, determination of asbestos content in any product alleged to contain asbestos can only be made by mechanical analysis using polarized light microscopy. It can identify the type of asbestos and the percentage of asbestos in a product.2

EXPOSURE

Significant exposure to asbestos has been associated with increased risk of developing health problems. It is important to note that there is generally a substantial interval of time between exposure and the diagnosis of an asbestos-associated disease. After exposure, as many as 40 years may pass between the time of exposure to diagnosis. In some cases, this makes it difficult to link a patient’s current conditions and symptoms to past exposure.

Persons who work directly with asbestos are at greatest risk; however, families of workers are also at some risk. Asbestos is sometimes unintentionally brought into the home on the clothing of those who have been exposed because its natural fibrous structure can easily be entwined into cloth. Levels of asbestos can also be detected in rural areas, but at very low levels that present little or no health risk. Levels of asbestos in the air are measured by fibers per milliliter, which is equivalent to a cubic centimeter of air. A cubic meter is approximately the amount of air that one is estimated to breathe in 1 hour. In areas near asbestos mines or factories, the concentration of asbestos may be 0.01 fibers/mL or higher. An average of 0.00001 fibers/mL are found in rural areas.8

The potentially dangerous effects of asbestos are highly dependent on the cumulative exposure, the elapsed time since initial exposure, and the physicalchemical properties of the fibers.10-12 Chrysotile has been used more than any other type of asbestos fiber and accounts for approximately 95% of the asbestos found in buildings throughout the U.S. It is a soft, flexible fiber included in various materials (i.e., compound, cement and flat sheets, pipe insulation, floor tiles) and is woven into fabric.13,14 Amphibole fibers (particularly those of amosite and crocidolite) are frequently found as fire retardants in thermal insulation products and ceiling tiles. They are believed to be more toxic than the chrysotile fibers because they accumulate more readily in the lung tissue, are not cleared as effectively, and are more durable.10-12 However, it has been reported that chrysotile-related malignancies are associated with a much higher lung fiber concentration inducing pulmonary disease, as compared with those of amphiboles. Since the situation is inconclusive, no safe threshold to asbestos exposure exists.13

Exposure can occur through ingestion, skin contact, or inhalation of fibers. Inhalation has been found to be the most hazardous and potentiates the greatest risk of developing asbestos-caused diseases. Skin contact with fibers is comparatively harmless. Ingestion of water that has been kept in or passed through asbestos-contaminated pipes has not been shown to increase the occurrence of asbestos-related diseases.10-13

ASBESTOS-RELATED DISEASES

Health concerns regarding asbestos exposure usually arise in persons who are in contact with and inhale high concentrations of asbestos fibers over a long period of time. It is very unlikely for an asbestos-related illness to result from a single, high-level exposure or a short period of lower level exposure.14 Most people will be exposed to asbestos at some point in their lives; however, people who develop asbestos-related diseases usually have a clear history of direct exposure, such as builders, construction workers, and painters who mix asbestos cement or work with asbestos sheet materials; plumbers and electricians who work with asbestos insulation materials; and those without knowledge of exposure such as shipyard workers or ship engineers.13,15,16

The development of illness associated with asbestos may be delayed, and, in most cases, people who become ill are those who have inhaled a large number of fibers or have been exposed for a prolonged period of time.13,14 Asbestos inhalation usually causes pleural plaques, pleural thickening, and pleural effusion.10 The diseases most commonly attributed to environmental exposure to asbestos include asbestosis, lung cancer, and mesothelioma. All of these pulmonary illnesses are due to the disturbance of lung tissue and the normal pathways that control inflammatory processes, resulting in an uncontrolled and detrimental response to the inhaled asbestos.3,17 In addition, inhaled asbestos retained in the lungs can become coated with a proteinaceous iron-staining material. Longer and stronger fibers are more likely to be coated, most likely the amphibole forms, which survive longer in lung tissue.

Asbestosis

Asbestosis is a serious, progressive form of interstitial fibrosis of the pulmonary parenchyma that can cause significant impairment, lung cancer, and death.6,13,14,18,19 Cigarette smokers seem to be affected more often and with more advanced disease for a given time of exposure than nonsmokers, which is believed to be a result of reduced clearance of asbestos fibers from the lungs.19,20 Smokers and ex-smokers also have a higher frequency of irregular opacities on chest x-ray than similarly exposed nonsmokers, but do not have differences in pleural fibrosis presentation.10-13,19,21,22

Affected persons typically present after a considerable latency period of about 2 decades with signs and symptoms such as dyspnea, clubbing of fingers, and/or crackles/rales. In advanced disease, pulmonary hypertension and the consequence of right-sided heart failure may result.18,23 Diagnosis of asbestosis is generally based on clinical findings rather than histologic evaluation of lung tissue.6,18 Chest x-rays are important tools in diagnosis and usually present small irregular opacities in the lower and middle lung fields, pleural thickening, and pleural calcifications.14 However, signs and symptoms tend to present early on in disease development, and chest radiography is found to be abnormal later on in approximately 90% of cases.6 In addition, reduction in lung volume (with inspiratory capacity and vital capacity primarily affected, functional residual capacity and residual volume less affected) may be observed along with impairment of diffusing capacity and the development of hypoxemia.18 Treatment should include management of the clinical manifestations, supportive care, and preventative measures against progression to malignant disease.19

Lung Cancer

Exposure to asbestos is one of the leading causes of all types of lung cancer. It is also an independent risk factor for the development of lung cancer, although smoking further increases this risk and may cause additional complications.13,15,24,25 To date, no genetic testing or biological markers are available for the differentiation between asbestos-associated and tobacco-associated lung cancers.10,26

Asbestos-related lung cancers may affect any pleural lobe, and they possess a comparable distribution to that of the major lung cancer types.26 Although asbestosis is thought to precede the development of lung cancer in many cases, extremely heavy exposure to asbestos can also directly cause lung cancer.27 All exposed persons with any breathlessness, chest pain, persistent and worsening cough, hemoptysis, and weight loss and/or anorexia should be tested for lung cancer. Diagnosis and management of confirmed lung cancer cases should be individualized based on the type and extent of cancer detected.27 An overview of certain studies reporting asbestos-related lung cancer deaths are presented in TABLE 1.

Malignant Mesothelioma

Malignant mesothelioma is a rare progressive and aggressive cancer of the pleura and/or peritoneum with increasing incidence.13,14,25,28 It is caused by occupational or domestic exposure to asbestos with a variable lag time between initial exposure and death.15,29 Therefore, even minimal exposure may result in the development of mesothelioma.30 The prognosis of this disease is generally poor, with a survival of about 8 to 14 months from the time of diagnosis.28

Diagnosis of malignant mesothelioma includes clinical, radiologic, and histologic evaluation. Evaluation should be considered particularly for exposed persons with pleural effusion and pleural thickening with complaints of chest pain.14,28 The chest pain is generally described as dull, diffuse, and progressive, and may be accompanied by dyspnea. Palpable chest wall masses, clubbing of fingers, features of pericardial effusion, and ascites may also be present as a result of progressive disease.14

Treatment of malignant mesothelioma should involve multidisciplinary collaboration. Physicians, radiologists, surgeons, pathologists, oncologists, nurses, and pharmacists are among the health care professionals needed to optimize patient care and formulate an appropriate management strategy. Although most treatment options are weak and controversial, considerations may include draining of pleural effusions, placement of an indwelling pleural catheter, prophylactic or palliative radiotherapy, chemotherapy, surgery, and lung-sparing debulking procedures.14,28 Pharmacists may play a key role in the supportive care of malignant mesothelioma, as well as in the management of related respiratory conditions and complications.

Other Cancers

In addition to the pulmonary carcinomas that may result from asbestos exposure, an increased risk of malignant disease in other parts of the body has been suspected. In particular, cancers of the gastrointestinal tract (i.e., oral cavity, larynx, esophagus, stomach, colon, and rectum) have been consistently seen in various epidemiologic studies.25,31 Lymphosarcoma and malignant lymphoma have also been reported to cause an excess number of deaths among exposed persons.32,34

ASBESTOS REGULATIONS

All new use of asbestos was banned by the EPA in 1989; however, established uses of asbestos were still allowed. In 2007, Canada was reported as one of the world’s leaders in asbestos production, mining 2.4 × 105 tons of asbestos.3 Other countries presently producing large amounts of asbestos are Russia, Kazakhstan, and China.4 In 2000, there were 21 countries with active mining facilities. The last operating mine in the U.S. mined chrysotile in California and was closed in 2002.7

The EPA and the Occupational Safety and Health Administration (OSHA) are two of the main federal organizations responsible for the regulation of asbestos exposure and the protection of workers who may be exposed. The EPA recommends a concentration limit of 7 million fibers per liter of drinking water for fibers greater than 5 µm.2,4 OSHA has set standards and has classified the hazards of asbestos for those who work in asbestos-containing environments (TABLE 2). Permissible exposure limits (PELs) are also set by OSHA and are not to exceed 0.1 fibers per cubic centimeter of air (averaged over an 8-hour shift). OSHA further defines short-term exposure as not exceeding more than 1 fiber per cubic centimeter over a 30-minute time period.5,34

The EPA is also responsible for developing and enforcing regulations necessary to protect the general public from exposure. It provides protection to those who may not be covered by their state OSHA standards. The EPA Workers Protection Rule, similar to the OSHA requirements, covers medical examinations, air monitoring and reporting, protective equipment, work practices, and record keeping. There are a number of state and local agencies that have additional restrictions and requirements for those who remove or renovate asbestos-containing buildings or areas.2 The U.S Geological Survey (USGS) has an ongoing project to map the locations of historic asbestos mines, former exploration, and naturally occurring asbestos. A report published in 2005 included 324 locations identified in the eastern U.S. alone.18

In addition to the ban placed in 1989 on all new uses of asbestos, the EPA has also put into place requirements for schools. All schools must be inspected for asbestos, and any damaged asbestos found must be removed or covered up to minimize exposure into the air. In attempts to continue to minimize exposure, the EPA also regulates demolition or renovation of factories and the disposal of asbestos waste and monitors for asbestos concentrations in water. The FDA controls and limits the use of asbestos in packaging materials and in the preparation of food.

SAFETY MEASURES

Although fears and concerns about asbestos in homes and buildings are evident, the EPA does not necessarily recommend that removal of asbestos in homes or buildings be attempted. However, overlooking the potential hazards of asbestos exposure is not recommended either. If, upon inspection, asbestos is identified in a home or building, the appropriate state or local health department or regional EPA office should be contacted immediately to assist in locating a company properly trained to identify, contain, and/or remove asbestos. An overview of asbestosis and safety precautions is provided in TABLE 3.

The proposed approach is to locate and properly manage the asbestos material that has been suspected and identified by encapsulating (sealing) it or enclosing (covering) it.2 Encapsulation involves treating the area with binders, which will keep the fibers together. Enclosure would help to prevent the release of fibers by covering the area with a protective wrap. Improperly removing asbestos can prove to be more hazardous than leaving undamaged asbestos fibers untouched. If disturbed, asbestos materials may release asbestos fibers into the air that can be inhaled into the lungs. Once inhaled, fibers can remain there for a considerable amount of time, increasing the risk of disease.5 Fibers are very difficult to destroy. Macrophages may attempt to ingest asbestos fibers. If the fibers are long, they resist being broken down. During this process, macrophages release substances that may in turn harm the alveoli, leading to scarring and fibrosis. Over a period of time, the number of affected alveoli increases and lung capacity decreases due to loss by the aveoli of the ability to exchange oxygen and carbon dioxide.34

The increased concern about health-related problems associated with asbestos has led to significant efforts to find alternatives. One less costly alternative is to use cellulose fibers. Glass fibers, graphite mixtures, synthetic fibers, and polypropylene are currently being used in the production of materials such as floor tiles and bulk thermal insulation where asbestos was previously utilized.1

ROLE OF THE PHARMACIST

As health care professionals, pharmacists play an important role in the management of asbestos-related diseases. A thorough occupational and environmental history of all patients with pulmonary signs and symptoms must be taken, referral to a physician chest specialist should be recommended, and the diagnosis, prognosis, and treatment considerations for asbestos-related diseases should be communicated to patients in an empathetic manner. Pharmacists can also identify patients at risk for developing asbestos-related illnesses by conducting thorough medication therapy management sessions with persons receiving respiratory medications and/or those with lung-related conditions.

In addition, pharmacists should encourage smoking cessation and immunizations against pneumococcal disease and influenza virus. Smoking cessation involves informative discussions with patients and the distribution of pertinent materials to prepare individuals for this important and healthy lifestyle change. Questions regarding smoking cessation should be encouraged and continued until an individual is able to make an informed decision. A review of the available OTC aids and prescription medications should then be conducted with individuals electing to quit smoking in order to explain the expectations of the process.

According to the most recent recommendations of the Advisory Committee on Immunization Practices (ACIP), persons with chronic disorders of the pulmonary system are advised to be vaccinated against influenza annually. In regard to pneumococcal immunization, the ACIP recommends that all those with chronic lung diseases be vaccinated at least once before the age of 65 years, as well as a one-time revaccination over the age of 65 years (if last vaccination was received >5 years before).35

Appropriate management of coexisting pulmonary disorders, such as chronic obstructive pulmonary disease and asthma, is also necessary to minimize further pulmonary complications. Pharmacists are in optimal positions to emphasize the importance of therapeutic compliance and to ensure proper medication administration. Evaluation of patient history and medication regimens is essential to better educating patients on the benefits of proper medication use. Many patients receiving medical devices for pulmonary conditions (i.e., inhalers, nebulizer solutions, etc.) do not always use these medication delivery products properly. Therefore, pharmacist knowledge and skills are necessary to educate these patients on proper use or to collaborate with prescribers to determine alternative therapies in patients who are not able to use such delivery devices. This will not only maximize the benefits of their medications and prevent further complications, but will also help reduce health care costs.

ADDITIONAL INFORMATION

According to the EPA, the public should be aware of and take certain precautions against asbestos, such as 1) minimizing activities in areas with damaged materials with suspected asbestos; 2) removing or repairing areas with suspected asbestos only by trained/ qualified individuals; 3) avoiding cleaning of debris that may contain asbestos; 4) avoiding working with asbestoscontaining materials unless necessary and proper safeguards are taken; and 5) avoiding any abrasion or stripping of asbestoscontaining flooring.2

If asbestos is suspected or information on asbestos is requested, the EPA and OSHA should be contacted for support and assistance with any inquiries. Currently, there are 10 EPA regional offices around the country. The National Emission Standards for Hazardous Air Pollutants (NESHAP) was established as a result of the Clean Air Act of 1970 and required the EPA to create and implement regulations to protect the general public from exposure to airborne contaminants known to be hazardous. Asbestos was one of the first contaminants acknowledged as an air pollutant by the EPA. Some specific responsibilities of the Asbestos NESHAP are to hold accountable those who are involved in the demolition or renovation of any area that may contain asbestos. Prior to any activity, state and local agencies must be notified that an area is suspected or confirmed to contain asbestos. Since being established in 1973, the Asbestos NESHAP has been amended (most recently in 1990) to maintain and improve policies as needed for the regulation, transfer, and disposal of asbestos. More information on NESHAP can be obtained by contacting the regional office of the EPA.2,5

In addition, the EPA Toxic Substances Control Act has established a hotline for those with general questions. The hotline number is (202) 554-1404. Information can also be sent to anyone who requests it from the EPA by calling the main number, (202) 272-0167. To address concerns of asbestos in schools, in the workplace, and at home, the EPA Asbestos and Small Business Ombudsman (ASBO) was created. This agency serves to facilitate communications between the small business community and the agency and may be contacted by calling the toll-free number, (800) 368-5888.2

OSHA has made available several resources (i.e., training and educational programs) for the public, as well. In 1989, the Federal Register published OSHA’s Safety and Health Program Management Guideline, which provides fine points and facts to assist in the development of health-management systems. Publications from OSHA can be accessed online at www.osha.gov. Complaints can also be submitted on the same Web site. Free copies of publications can also be requested by sending a self-addressed envelope to OSHA Publications Office, P.O. Box 37535, Washington, DC 20013-7535. Requests could also be made by contacting OSHA at (202) 693-1888. 5

If compensation is being sought for illnesses related to asbestos exposure, the Department of Work and Pensions should be contacted. Compensation may be available through the Industrial Injuries Disablement Benefit (IIDB). However, according to the Limitations Act of 1980, patients must make their claims within 3 years of the date that serious injury became known. It should be noted that the process by which a claim is made can be extensive.13

REFERENCES

  1. U.S. Geological Survey. Asbestos: Geology, Mineralogy, Mining and Uses. Open-file Report 02-149. Usgs.gov. Accessed March 20, 2009.
  2. United States Environmental Protection Agency. The Asbestos Informer/ Region 4/US EPA. www.epa.gov/region4/air/asbestos/inform.htm. Accessed December 16, 2009.
  3. Luus k. Asbestos: mining exposure, health effects and policy implications. MJM. 2007;10:121-6.
  4. Wood WB, Gloyne SR. Pulmonary asbestosis. Lancet. 1930;i:445.
  5. U.S Department of Labor Occupational Safety and Health Administration 2002. www.osha.gov/OshDoc/data_AsbestosFacts/asbestos-factsheet.pdf. Accessed December 15, 2009.
  6. Ross R. The clinical diagnosis of asbestos in this century requires more than a chest radiograph. Chest. 2003;124:1120-1128.
  7. Van Gosen BS. Reported historic asbestos prospects and natural asbestos occurrences in the central United States. U.S. Geological Survey Open-File Report 2006-1211 Version 1. http://pubs.usgs.gov/of/2010/1041/downloads/ Plate.pdf.
  8. Department of Health and Human Services. Agency for Toxic Substances and Disease Registry. Public Health Statement Asbestos CAS# 1332-21-4. Division of Toxicology. September 2001. www.atsdr.cdc.gov. Accessed March 23, 2010.
  9. United States Environmental Protection Agency. Naturally occurring asbestos: approaches for reducing exposure. March 2008. www.epa.gov.
  10. Kamp DW. Asbestos-induced lung disease: an update. Translational Research. 2009;153:143-52.
  11. Cugell DW, Kamp DW. Asbestos and the pleura: a review. Chest. 2004;125:1103-1117.
  12. Mossman BT, Churg A. Mechanisms in the pathogenesis of asbestosis and silicosis. Am. J. Respir. Crit. Care Med. 1998;157:1666-1680.
  13. Currie GP, Watt SJ, Maskell NA. An overview of how asbestos exposure affects the lung. BMJ. 2009;339:506-510.
  14. Department of Health and Human Services. Asbestos. www.hhs.gov. September 16, 2001. Accessed April 1, 2010.
  15. Rake C, Gilham C, Hatch I, et al. Occupational, domestic and environmental mesothelioma risks in the British population: a case-control study. Br J Cancer. 2009;100:1175-1183.
  16. Department of Health and Human Services. Agency for Toxic Substances and Disease Registry. What is asbestos? www.atsdr.cdc.gov. Accessed March 23, 2010.
  17. American Thoracic Society. Workshop on lung disease and the environment. Where do we go from here? Am J Respir Crit Care Med. 2003;168:250254.
  18. American Thoracic Society. The diagnosis of nonmalignant diseases related to asbestos. American Review of Respiratory Disease. 1986;134:363-368.
  19. American Thoracic Society. Diagnosis and initial management of nonmalignant diseases related to asbestos. Am J Respir Crit Care Med. 2004;170:691715.
  20. Committee on Nonoccupational Health Risks of Asbesiform Fibers. Board of Toxicology and Environmental Health Hazards. National Research Council. Asbestiform fibers: nonoccupational health risks. Washington DC: National Academic Press; 1984:24-29.
  21. Lilis R, Selikoff IJ, Lerman Y, et al. Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking. Am J Ind Med. 1986;10:459-4570.
  22. Ehrlich R, Lilis R, Chan E, et al. Long-term radiological effects of shortterm exposure to amosite among factory workers. Br J Ind Med. 1992;49:268275.
  23. Lemen RA, Dement JM, Wagoner, JK. Epidemiology of asbestos-related diseases. Environmental Health Perspectives. 1980;34:1-11.
  24. Berry G, Newhouse ML, Turok M. Combined effects of asbestos exposure and smoking on mortality from lung cancer in factory workers. Lancet.1972;2:76.
  25. Rom WN, Palmer PES. The spectrum of asbestos-related diseases. West J Med. 1974;121:10-21.
  26. Mossman BT, Churg A. Mechanisms in the pathogenesis of asbestosis and silicosis. Am J Respir Crit Care Med. 1998;157:1666-1680.
  27. Kipen HM, Lilis R, Suzuki Y, et al. Pulmonary fibrosis in asbestos insulation workers with lung cancer: a radiological and histopathological evaluation. Br J Ind Med. 1987;44:96-100.
  28. British Thoracic Society. BTS statement on malignant mesothelioma in the UK. Thorax. 2007;62:ii1-19.
  29. Strumphius J, McGer PB. Asbestos bodies and mesothelioma. Ann Occup Hyg. 1968;11:283-293.
  30. Newhouse MI, Thompson H. Mesothelioma of pleura and peritoneum following exposure to asbestosin the London area. Brit J Indust Med.1965;22:261-269.
  31. Stell PM, McGill T. Asbestos and laryngeal carcinoma. Lancet. 1973;11:416-417.
  32. Robinson CF, Lemen RA, Wagoner JK. Mortality patterns, 1940-1075, among workers employed in an asbestos textile friction and packing products manufacturing facility. In: Dusts and Disease. RA Lemen and JM Dement, Eds. Forest Park, IL: Pathotox Publishers, 1979.
  33. Department of Health and Human Services. Agency for Toxic Substances and Disease Registry. Asbestos-Health Effects. April 1, 2008. www. Atsdr.cdc. gov/asbestos/asbestos/heath_effects. Accessed March 23, 2009.
  34. Mayoclinic. Abestosis. www.mayoclinic.com/health/asbestosis/DS00482. Accessed December 16, 2009.
  35. MMWR Recommended adult recommendation schedule–United States, 2010. www.cdc.gov/mmwr/PDF/wk/mm5901-Immunization.pdf. Accessed June 4, 2010. Jun 4

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