Asbestos-related diseases

Essentials

Asbestos may cause benign pleural changes, fibrosis of the lung parenchyma (asbestosis), lung cancer, pleural and peritoneal malignancies (mesothelioma), laryngeal cancer, ovarian cancer, as well as a rare condition known as retroperitoneal fibrosis.
• Exposure to both smoking and asbestos greatly increases the risk of cancer compared with that associated with either one separately. The risk of lung cancer in a smoking asbestos worker may increase up to 50-fold.
• As the latency phase is long, asbestos-related diseases continue to be among the most common occupational diseases.
  • In Finland, pleural changes due to asbestos, and asbestosis, are still diagnosed as occupational diseases in about 420 and 30 people per year, respectively.
  • About 25 cases of occupational lung cancer, and 50 cases of occupational mesothelioma, due to asbestos are diagnosed per year in Finland.
• Remember to assess the possibility of exposure to asbestos in patients with lung cancer.Asbestos may cause lung cancer, malignancy of the pleura and peritoneum (mesothelioma), laryngeal cancer, ovarian cancer, fibrosis of the lung parenchyma (asbestosis) as well as pleural changes and a rare condition known as retroperitoneal fibrosis.The combination of smoking and asbestos strongly increases the cancer risk associated with both of these exposures separately. The risk of lung cancer in a smoking asbestos worker may increase up to 50-fold. Remember to assess the possibility of occupational disease in persons exposed to asbestos.

Exposure

Asbestos is the generic term for a group of fibrous silicate minerals including actinolite, amosite, anthophyllite, crocidolite, chrysotile and tremolite. All types of asbestos cause the same diseases.
• In Finland, use of asbestos has been forbidden since 1994 (Government Decrees 643/2005 and 415/2009, EC Regulation 1907/2006).
• Before that time, people could be exposed to asbestos in, for instance, the following tasks or working environments: asbestos spraying, asbestos mines, manufacture of asbestos products, brake and clutch work, service and maintenance, shipyards, installation of boilers, lining or dismantling stoves, lagging of pipes, other insulating work, production of building materials, building construction, and property maintenance. There are still tens of thousands of people alive who were exposed to asbestos while working in such areas before 1994.
• Exposure to asbestos is still possible in demolition work if protection guidelines are not followed or inappropriate techniques are used. An asbestos survey must be performed before demolishing any building completed before 1994 (Government Decree 798/2015).
• In mining, exposure may still occur if the material being mined contains asbestos.
• The binding limit for asbestos content in workplace air is 0.1 fibres/cm³.
• Mild exposure may occur at home or at the workplace if old asbestos-containing building materials are deteriorated or premises are not carefully cleaned after demolishing.
• Asbestos fibres must not be present on indoor surfaces. The limit for clean room air is below 0.01 fibres/cm³.The primary aim is to prevent the exposure of humans to asbestos dust. Asbestos is the generic name used for a group of fibrous silicate minerals like actinolite, amosite, anthophyllite, crocidolite, chrysotile and tremolite. Exposure to any type of asbestos fibres may cause cancer in humans. Other mineral fibres such as talc or vermiculite may also contain asbestos, and they should be considered carcinogenic as well . In many countries the use of asbestos has been banned, e.g. in Finland since the year 1994. Many old buildings may still contain rich amounts of asbestos. The exposure to asbestos may take place in building renovation work when the old structures are demolished, if protection guidelines are not followed and the techniques used are not appropriate. The binding limit value for asbestos content in the workplace air is 0.1 fibres/cm3. Before the introduction of current legislation asbestos exposure was possible when working under the following circumstances: asbestos spraying, asbestos mines, manufacture of asbestos products, brake and clutch work, service and maintenance work, shipyards, installation of boilers, lining or dismantling stoves, lagging of pipes, other insulating work, production of building materials, building construction and property maintenance. There is still a considerable number of people alive who have earlier been exposed to asbestos while working in these tasks.Many countries keep a national registry of workers who in their occupation get exposed to cancer-causing substances like asbestos.

Investigation of exposure

• Any history of exposure should be defined based on the person's work history. The interviewer should know occupations that used to involve exposure to asbestos, or still do. The physician should therefore consult an occupational physician or the outpatient clinic of occupational medicine.
• If bronchoscopy is performed, the lavage fluid can be examined to determine the number of coated asbestos fibres (asbestos bodies) per millilitre.
• Asbestos exposure can also be examined by ashing lung tissue and calculating the number of asbestos fibres per gram dry lung.
• Bronchoscopy or lung biopsy should not be performed just to examine potential exposure.

Diseases

No threshold exposure level has been established below which the risk of asbestos-related cancers would not be increased.
• The latent phase from exposure to manifestation of disease usually lasts over 10 years; in the case of asbestos-related cancers the phase may often last 20–40 years or even longer.
• In Finland, the number of cases of asbestosis is decreasing, already, but the numbers of asbestos-related cancers are at their peak. They are only expected to decrease in the 2020s.
• Virtually all people who fall ill today were exposed before 1994.The threshold exposure level, below which the risk of asbestos-related cancers would not be increased, has not been established. The higher the exposure the higher the risk of asbestos-related cancers. The latent phase from exposure to disease emergence usually lasts over 10 years; in the case of asbestos-related cancers the phase may often last 10–40 years or even longer. Asbestos-induced cancers attributable to earlier asbestos exposure are estimated to peak in the 2010s. Virtually all people who today fall ill with such cancer have been exposed before the year 1994.

Pleural changes

• High-resolution computed tomography (HRCT) is diagnostically more sensitive and specific than chest x-ray.
• Thickening of the outer layer of the pleura, i.e. the parietal pleura (pleural plaques, pictures )
  • Even minor exposure may cause pleural plaques. These can also be seen in people who have not been exposed to asbestos in their work.
  • They can be seen in x-ray after a latency period of no less than 10 years, often in the diaphragmatic domes or parietal pleura in the region between the 5th and 10th ribs.
  • Plaques are often first detected unilaterally, but with continued monitoring they appear on both sides. Bilateral plaques are a reliable sign of asbestos exposure.
  • Pleural plaques do not usually cause symptoms or changes in lung function tests.
• Lesions of the visceral pleura
  • Changes in the visceral pleura usually indicate heavier asbestos exposure than plaques alone.
  • The visceral pleura thickens because of fibrosis and becomes attached to the parietal layer. At least in some patients this may be due to a history of exudative pleurisy.
  • Differential diagnosis should include accumulation of fat in the pleural space.
  • Early stages of the disease are asymptomatic, but in more advanced cases the patient may present with cough and dyspnoea.
  • Changes in the visceral pleura may also be present in patients with connective tissue disorders or as an adverse effect of pharmaceuticals.
• Round atelectasis
  • Usually caused by factors other than asbestos exposure
  • Can occur in any part of the lungs. The atelectatic lung tissue beneath the fibrotic pleura becomes twisted, producing a rounded shadow. The spiral structure of a round atelectasis is readily apparent on computed tomography.
• Exudative pleurisy
  • Asbestos exposure can lead to exudative pleurisy within as little as 10 years after the first exposure. There is no specific finding indicative of this condition. The association with asbestos exposure often remains uncertain, and the association may only be confirmed during subsequent follow-up.

Asbestosis (pneumoconiosis)

Asbestosis is a diffuse interstitial fibrosis of the lungs, caused by asbestos.
• The diagnosis of asbestosis is based on the demonstration of significant exposure to asbestos and findings in HRCT of the lungs, as well as differential diagnosis excluding other causes.
• Chest x-ray is insensitive in showing fibrosis, and pleural changes may mask parenchymal lesions.
• When asbestosis has become widespread, the diagnosis is also supported by clinical findings (dyspnoea on exertion) as well as findings in pulmonary function tests (restriction and diffusion impairment).All forms of asbestos may cause asbestosis. Asbestosis is a diffuse interstitial fibrosis of the lungs. The diagnosis of asbestosis is based on the demonstration of significant occupational exposure to asbestos and often on high-resolution computed tomography (HRCT). Up to 20% of asbestos-exposed workers may show histopathological findings of lung fibrosis even if the chest x-ray findings are normal. Owing to the long latency period, those who today develop asbestosis have usually been exposed to asbestos in the1970s. The increase of connective tissue starts in the lower lobes and causes shrinking of the lungs as it progresses. The interpretation of a chest x-ray for incipient diffuse pulmonary fibrosis requires an experienced radiologist. HRCT will detect changes in lung tissue earlier than chest radiography. Pleural changes may mask the parenchymal lesions. When asbestosis has become widespread, the diagnosis is also supported by clinical signs and symptoms (dyspnoea on exertion) as well as findings of pulmonary function tests (restriction and diffusion impairment).

Mesothelioma (a neoplasm of the pleura or peritoneum)

The only established causes of mesothelioma are asbestos and erionite fibre.
• The latent period for mesothelioma is usually 30–50 years.
• The exposure need not be of long duration: heavy exposure lasting only a few days or a week may cause mesothelioma.
• A detailed employment history is sufficient to show occupational origin.
• All mesotheliomas should be considered potential occupational diseases. Reimbursement for the treatment of occupational disease is available for all patients with mesothelioma exposed to asbestos in their employment.
• The first sign of mesothelioma is usually unilateral pleural effusion. The diagnosis is often only confirmed in thoracoscopy. Differential diagnosis against adenocarcinoma may be difficult. The mesothelioma panel by the Finnish Institute of Occupational Health may help with diagnostic problems (please contact a pathologist at the Finnish Institute of Occupational Health in Helsinki).

Lung cancer

Exposure to both smoking and asbestos greatly increases the risk of cancer compared with that associated with either one separately. The risk of lung cancer in a smoking asbestos worker may increase up to 50-fold.
• Asbestos-induced lung cancer does not differ from ordinary lung cancer in location or histology, but it tends to occur at a younger age.
• The employment history of each lung cancer patient must be examined and the possibility of an occupational aetiology considered. A work history form can be used to identify exposure to asbestos, and an occupational physician or outpatient clinic of occupational medicine can be consulted, as necessary.
• If a patient with lung cancer is assessed to have had heavy exposure to asbestos, reimbursement for the treatment of occupational disease is available regardless of smoking habits.

Surveillance and diagnostics of asbestos-exposed persons

• Based on Government Decree 1485/2001, the Finnish Ministry of Social Affairs and Health gave out instructions for health check-ups in occupational health care (Terveystarkastukset työterveyshuollossa) in 2005 6.81c.
• Occupational health care should conduct an initial health examination before the start of asbestos work.
  • Today, workers participating in demolition work may be exposed to asbestos. Demolition is physically hard work requiring meticulous use of respiratory protective devices (also taking the condition of facial skin into consideration) and careful observation of regulations, which should be considered when performing the initial check-up and subsequent follow-up examinations.
  • The initial check-up should include at least chest x-ray and spirometry. Regular follow-up examinations are usually done by occupational health care every 3 years. The first chest x-ray for detection of any pleural lesions need not be done until 10 years after starting asbestos demolition.
• The aim of follow-up of persons with significant exposure to asbestos at work or who have developed an asbestos-related disease is to improve the early diagnosis of occupational diseases, and at the same time to guarantee the appropriate sociomedical benefits to the patients (ILO Conventions No. 139, 1974 , and No. 162, 1986 ).
• If findings consistent with, or suggestive of, asbestos-related disease occur in people with work-related asbestos exposure, it is advisable to have investigations carried out either in occupational health care or at an outpatient clinic of pulmonary diseases or occupational medicine. The work history should be used to assess whether exposure to asbestos has been light, moderate or heavy.
• Since the diseases due to the asbestos exposure may not emerge until after many years, health examinations of those with significant exposure should also be continued after the exposure. However, no follow-up is necessary after only light exposure.
• Occupational health care should advise people ending their employment, including those retiring or being made redundant, to seek health check-ups at their health centre or their own physician when follow-up by occupational health care ends. Practical instructions for people exposed to asbestos are also available in a guide (in Finnish) published by The Organisation for Respiratory Health in Finland (www.hengitysliitto.fi/asbestisairaudet).The health of individuals who have been subjected to occupational exposure to asbestos should be monitored at regular intervals. The worker should go through an initial health examination at the start of asbestos work and then regular follow-up examinations every three years. The aim of follow-up of persons with significant exposure to asbestos at work or who have developed an asbestos-related disease is to improve the early diagnosis and prognosis of occupational diseases, and at the same time to guarantee the appropriate sociomedical benefits to the patients (ILO Occupational Cancer Convention No. 139, 1974 , and Asbestos Convention No. 162, 1986 ). HRCT and spiral CT have proven to be far more sensitive and accurate than chest x-rays in the diagnostics of asbestos-related diseases. These techniques provide ever better ways to identify pleural and parenchymal changes related to asbestos at an early stage. Since the diseases due to the asbestos exposure may emerge only after many years, health examinations should be continued also after the exposure has ceased. If signs or symptoms consistent with, or suggestive of, asbestos-related diseases occur, it is advisable to have any clinical diagnostic investigations carried out either at a department of pulmonary diseases or at a unit specialising in occupational medicine.

Procedures to be followed in cases of occupational disease

Any patient with suspected asbestos-related disease should be referred for investigations at an outpatient clinic of occupational medicine or pulmonary diseases.
• The insurance system nd the Occupational Safety and Health Administration should be appropriately notified of any diagnosed or suspected occupational disease.
• The health of patients with asbestos-related occupational disease should be closely monitored, and the insurance company should be informed about this.
• This will ensure that those affected will receive due compensation for their occupational disease. The compensation paid out to patients and the survivors' family pension payable to the next-of-kin of deceased individuals can be substantial, particularly in cases of occupational cancer.
• Patients can be followed up in specialized care or those continuing to work referred back to occupational health care and those outside working life to a health centre. In Finland, rehabilitation is reimbursed according to the Employment Accidents Act.
• Whenever there is reason to suspect that a disease resulting from occupational exposure to asbestos has caused or hastened a patient's death, the possible need for medicolegal autopsy should be discussed with the police. The same principle also applies to cases where the suspicion arises during medical autopsy. If an occupational disease is only confirmed in connection with autopsy, it should be ensured that a notification of occupational disease and a medical statement are written.Mesotheliomas, lung cancers and pleural and parenchymal fibroses in asbestos-exposed individuals are investigated, and all such diagnoses are reported to an appropriate insurance company and to the industrial safety authority. This ensures that the affected persons will receive due compensation for their occupational diseases. The compensation paid out to diseased persons and the survivors' family pension payable to the next-of-kin of a deceased individual, can be substantial, particularly in cases of occupational cancer. Whenever there is reason to suspect that an illness resulting from occupational exposure to asbestos has caused or hastened a patient's death, the possible need of a medicolegal autopsy should be discussed with the police authority. This also applies to cases where the suspicion arises during medical autopsy.

Related resources

• Other Internet resources
• Literature

Ədəbiyyat

1. IARC monographs on the evaluation of carcinogenic risks to humans. Volume 100C (2012). A review of human carcinogens: arsenic, metals, fibres, and dusts.