Updated: Mar 05, 2020
  • Author: Christopher D Jackson, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Asbestosis is a process of diffuse interstitial fibrosis of the lung due to exposure to asbestos dust. [1, 2]  Asbestos is the name given to a group of naturally occurring minerals that are resistant to heat and corrosion; these include mineral fibers such as chrysotile, amosite, and crocidolite, among others. Chrysotile is by far the most common type of asbestos fiber produced in the world, and it accounts for virtually all commercial use of asbestos in the United States.

Exposure to asbestos occurs through inhalation of fibers in air in the working environment, ambient air in the vicinity of factories handling asbestos, or indoor air in housing and buildings containing asbestos materials. Heavy exposures to asbestos can occur in the construction or shipping industries, particularly during the removal of asbestos materials for renovation, repairs, or demolition. Workers are also likely to be exposed during the manufacture and use of asbestos products (eg, textiles, floor tiles, friction products, insulation [pipes], other building materials), as well as during automotive brake and clutch repair work. Asbestos stopped being manufactured in US materials since the 1970s. 

The development of asbestosis is dose dependent, with symptoms typically appearing only after a latent period of 20 years or longer. However, the latency period may be shorter after intense exposure.


Pathophysiology and Etiology

The incidence of asbestosis varies with the cumulative dose of inhaled fibers; the greater the cumulative dose, the higher the incidence of asbestosis. Experts estimate a 1% risk of developing asbestosis after a cumulative dose of 10 fiber-year/m3. [3]

All types of asbestos fibers are fibrogenic to the lungs. Amphiboles, particularly crocidolite fibers, are markedly more carcinogenic to the pleura. [3]  The dimensions of the fibers are also important. [4, 5] Fibers with diameters smaller than 3 micrometers are fibrogenic because they penetrate cell membranes. Long fibers (ie, >5 micrometers) are incompletely phagocytosed and stay in the lungs, leading to cytokine release and cell destruction.

The initial inflammation of asbestosis occurs in the alveolar bifurcations, characterized by the influx of alveolar macrophages. Asbestos-activated macrophages produce a variety of growth factors, including fibronectin, platelet-derived growth factor, insulinlike growth factor, and fibroblast growth factor, which interact to induce fibroblast proliferation.

Oxygen free radicals (eg, superoxide anion, hydrogen peroxide, hydroxy radicals) released by the macrophages damage proteins and lipid membranes, potentiating the inflammatory process. A plasminogen activator, which is also released by macrophages, further damages the interstitium of the lung by degrading matrix glycoproteins.

Individuals probably differ in their susceptibility to asbestosis based on respiratory clearance and other unidentified host factors. People who smoke have an increased rate of asbestosis progression, likely due to impaired mucociliary clearance of asbestos fibers. [6]  In addition, although data regarding the association between MUC5B promoter polymorphism and idiopathic pulmonary fibrosis appear to be clear, the data are mixed about the MUC5B promoter variant being a potential genetic risk factor for asbestosis. [7, 8, 9]

Uncertainty remains about the mode(s) of action of asbestos in the genesis of diseases; therefore, an expert group has previously proposed cooperative action by diverse scientific disciplines to address such issues as terminology, mineralogy, test materials, and experimental models. [10]

Antinuclear antibodies

Exposure to amphibole asbestos fibers is linked to the production of autoantibodies. Moreover, studies indicate that asbestos-related abnormalities occur more often in individuals who test positive for antinuclear antibodies (ANAs) than they do in persons who test negative for them. These studies were conducted on the population of Libby, Montana, where mining, transportation, and processing of asbestos-contaminated vermiculite caused an increased risk of asbestos-related pleural and lung diseases. [11]  Serum samples in the study showed that the majority of persons sampled were positive for ANAs. [12, 13] In addition, the risk of developing pleural or interstitial abnormalities was more than triple in the ANA-positive individuals than it was in persons who were ANA negative. [12]

Despite the association with ANA seropositivity, there is no clear link between asbestos exposure and the development of autoimmune disorders such as systemic lupus erythematosus. This lack of association with autoimmune disease is in stark contrast to silicate dust in which there is an association with the development of autoimmune disorders. [14, 15, 16]

Sources of asbestos exposure

As noted earlier, exposure to asbestos occurs through inhalation of fibers in air in the working environment, ambient air in the vicinity of factories handling asbestos, or indoor air in housing and buildings containing asbestos materials. Manufacturers commonly use asbestos in the following products:

  • Products containing asbestos cement: Pipes, shingles, clapboards, sheets

  • Vinyl-asbestos floor tiles

  • Asbestos paper in filtration and insulation products

  • Material in brake linings and clutch facings

  • Textile products: Yarn, felt, tape, cord, rope

  • Spray products used for acoustic, thermal, and fireproofing purposes

Occupations associated with asbestosis include the following:

  • Insulation workers

  • Boilermakers

  • Pipefitters

  • Plumbers

  • Steamfitters

  • Welders

  • Janitors

The risk of uncontrolled removal of sprayed-on asbestos was highlighted in a study of two workers, in whom the presence and persistence of asbestos fibers and bodies in their bronchoalveolar lavage (BAL) fluid was noted even after several months. [17, 18]  A separate study provided a detailed assessment of the health hazards of exposure to asbestos-containing drywall accessory products. [19]



The World Health Organization (WHO) estimates 125 million people worldwide are exposed to asbestos in the workplace and over 100,000 people die each year from asbestos-related lung cancer, mesothelioma, and asbestosis. [3] In addition, nearly 400 deaths have been attributed to non-occupational exposure to asbestos. [3]  According to 1999-2010 mortality data from the National Center for Health Statistics (NCHS), 6,290 deaths were attributed to asbestosis in this period, of which the majority of deaths were in white males (95%) with a median age of 79 years. [20]  The most recent US mortality data due to asbestosis span 2005–2014 (posted May 2017), in which 13,024 deaths were related to asbestosis, again predominantly in white males but with a slightly older median age (80.8 years). [21]

The World Trade Center Health Registry estimates about 410,000 people were exposed to asbestos when up to 400 tons of it was released following the collapse of the the Twin Towers on September 11, 2001 ("9/11"). [22]  Those at highest risk for developing 9/11-related illnesses are workers who participated in the rescue, recovery, and clean-up efforts at the sites of the towers, and those living and working in lower Manhattan during the clean-up.

 A substantial amount of asbestos remains in buildings and eventually will be removed, either during remediation or renovations or demolition. It has been estimated that approximately 1.3 million workers in construction and general industry are potentially exposed to asbestos during maintenance activities or remediation of buildings containing asbestos. [20]  In the United States, vermiculite mined in Libby, Montana, was found to be contaminated with asbestos; this Libby vermiculite was used in 70% of vermiculite insulation in the United States from 1919 to 1990. In a study of 128 Libby miners, 119 had asbestos-related findings on high-resolution computed tomography scans. [23]  

Asbestos has not been mined in the United States since 2002, but approximately 340 metric tons were imported in 2016 for use in the chloralkali industry to manufacture semi-permeable diaphragms in electrolytic cells. In addition, an unknown quantity of asbestos was imported within manufactured products, possibly including brake linings and pads, building materials, gaskets, millboards, and yarn and thread, among others. [24]

Globally, bans on asbestos use are in place in several countries, including Australia, Japan, South Africa, and the nations of the European Union; asbestos use is restricted in the United States and Canada. However, persons who have been previously exposed to asbestos continue to be at risk for asbestosis and other asbestos-related diseases due to long latency periods following exposure. [25, 26]  In addition, trends in developing countries and countries that are emerging as economic powers indicate an increasing problem with asbestos-related diseases. [27]




The following complications can result from asbestos exposure:

  • Pulmonary hypertension

  • Cor pulmonale

  • Right-sided heart failure

  • Progressive respiratory insufficiency

  • Malignancy

Progressive respiratory insufficiency

The risk factors for developing progressive respiratory insufficiency are as follows:

  • Cumulative amount of asbestos inhaled

  • Degree of dyspnea

  • Cigarette smoking

  • Combined pulmonary and pleural involvement

  • Honeycombing visible on radiographs

  • High number of neutrophils, eosinophils, and fibronectin in bronchoalveolar lavage (BAL) fluid


A higher risk of lung carcinoma has been found in patients with asbestosis. Specifically, asbestos exposure raises the risk for bronchogenic carcinoma. Patients with asbestosis are also at risk for developing malignant mesothelioma and carcinomas of the upper respiratory tract, esophagus, biliary system, and kidney. Findings from a mortality study published in 2018 that followed 3984 Genoa Italian shipyard workers between 1960 and 1981 to 2014 found an 83.6% mortality (n = 3331), with excess mortality for all cancers, pleural mesothelioma, and cancers of the larynx and lung, as well as for respiratory diseases, including asbestosis. [28] Of 399 deaths from lung cancer, 90 (22.6%) were attributed to asbestos exposure.

People who smoke are likely to develop chronic bronchitis and obstructive airway disease, and they are prone to respiratory tract infections. Moreover, people who smoke are at high risk for the development of bronchogenic carcinoma because asbestos and tobacco smoke have synergistic carcinogenicity. [29] Individuals who both smoke and are exposed to asbestos are several times more susceptible to the development of lung carcinoma than are individuals without either exposure. [30]

Some studies show that asbestos exposure alone, without a smoking history, increases the risk of lung carcinoma six-fold.

In addition, a meta-analysis of several studies of women who were occupationally exposed to asbestos found sufficient evidence for a causal association between asbestos exposure and ovarian cancer. [31] This association should be interpreted with caution as some cohort studies included in prior meta-analyses reported disease misclassification for peritoneal mesothelioma. [32]

Concomitant diseases

Asbestosis may coexist with other asbestos-related diseases, including calcified and noncalcified pleural plaques, pleural thickening, benign exudative pleural effusion, rounded atelectasis, and malignant mesothelioma of the pleura.

Airway obstruction

Ameille et al found no causal relationship between airway obstruction and asbestos exposure. Their study evaluated lung function in persons (N=3,660) with previous occupational exposure to asbestos. [33] No significant correlation was shown between pulmonary function parameters and cumulative asbestos exposure.


Patient Education

Inform patients of the work-related causes of asbestosis (see Medical Care). For patient education information, see Bronchoscopy.

What is asbestos?

Asbestos is a group of minerals shaped as long fibers. Sources of asbestos, up to the 1970s, included insulation, car brakes, ships, and construction materials. 

Who gets exposed to asbestos?

People get exposed to asbestos through theiri work. Occupations at high risk include construction workers, roofers, welders, insulation workers, etc. As absestos can linger on articles of clothing, family members of people who work in these occupations can be exposed if not careful.

What health problems can result from exposure to asbestos?

Asbestos can causes many health problems. The mnemonic CAP can help you remember the health problems associated with asbestos exposure. C stands for cancer. Asbestos exposure has been associated with lung cancer and rarely mesothelioma. A stands for asbestosis. Asbestosis is when asbestos causing damage to parts of the lung, which can make it diffiicult to breathe. P stands for pleural disease. The pleura is the thin outer coveriing of your lungs. When asbestos causes disease in the pleura, it can cause fluid to accumulate in that space. This fluid accumulation can cause difficulty breathing. 

Symptoms of asbestos exposure do not occur immediately after contact with the mineral. Some people may not have symptoms for 15 to 30 years. Most patients who develop asbestosis or other related disease due to asbestos exposure will have shortness of breath. Other symptoms include coughinig up blood or chest pain. If you experience any of these systems. you should seek medical attention.