Asbestos is a naturally-occurring mineral used as an insulation material. Exposure to asbestos can occur in several occupations. Large amounts of asbestos fibers or dust inhaled over long period of time can produce damage and scar tissue in the lungs, making it difficult to breathe. This condition is called asbestosis.
Asbestosis is caused by breathing in asbestos fibres. People working in certain trades are more likely to have been exposed to asbestos in the past.
WHAT IS ASBESTOS?
Asbestos is a general term for a group of minerals made of microscopic fibres. Materials containing asbestos used to be widely used in construction, because they are strong, durable and fire-resistant.
There were three main types of asbestos in commercial use:
- crocidolite (“blue asbestos”)
- amosite (“brown asbestos”)
- chrysotile (“white asbestos”)
All these types of asbestos are hazardous if a material containing them becomes damaged and the fibres are released into the air.
No crocidolite was imported into the UK after 1970, and both amosite and crocidolite were banned in 1985 (although voluntary bans on the industrial use of both these materials came into force earlier than this). Chrysotile was not banned until 1999.
This means that, although asbestos is no longer used, materials containing asbestos are still found in many older buildings.
HOW ASBESTOS FIBRES AFFECT THE LUNGS
When you inhale a foreign body, such as a dust particle, cells in the lungs called macrophages usually hunt and break the particle down before it gets into your lung tissues and bloodstream.
However, asbestos fibres are too difficult for the macrophages to break down. In an attempt to break down the fibres, the macrophages release substances that are intended to destroy the fibres, but actually cause the tiny air sacs in your lungs (alveoli) to become damaged and permanently scarred over time. This scarring is what is known as asbestosis.
Alveoli are crucial in transferring oxygen from the air into your bloodstream and removing carbon dioxide from your bloodstream. If they become damaged and scarred, these processes will be affected, resulting in symptoms such as breathlessness.
For asbestosis to develop, prolonged exposure – usually over many years – to relatively high numbers of asbestosis fibres is necessary.
OCCUPATIONS ASSOCIATED WITH ASBESTOS EXPOSURE
The use of asbestos increased significantly after World War II. It peaked during the 1970s, before declining during the 1980s and 1990s. You may have been exposed to asbestos if you worked in an industry such as building or construction, where asbestos was used during this time period.
Occupations particularly associated with exposure to asbestos during this period include:
- insulation workers
- plumbers, pipefitters and steamfitters
- shipyard workers
- sheet metal workers
- chemical technicians
- heating, air-conditioning and refrigeration mechanics
Now that asbestos is no longer used, those most at risk of being exposed to asbestos fibres include people whose jobs put them at risk of damaging any asbestos remaining in older buildings, such as caretakers, electricians and demolition workers.
When asbestos fibres are inhaled, they deposit at alveolar duct bifurcations and cause an alveolar macrophage alveolitis. These activated macrophages release cytokines, such as tumour necrosis factor and interleukin-1beta and oxidant species, which initiate a process of fibrosis.  The initial interstitial fibrosis typically occurs in the lower lobes and may progress to extensive fibrosis and honeycombing. Peri-bronchial fibrosis with a cellular infiltrate may narrow the airway and cause reduced air flow.
The presence of asbestos bodies, coating of asbestos fibres that are typically amphiboles not chrysotile with iron and haemosiderin, are useful diagnostically but are rare (<15% with asbestosis).
The presence of asbestos fibres is associated with radiographical changes. However, since the most common asbestos fibre, chrysotile, is more easily broken down and cleared from the lung than amphibole fibres, the correlation is with the amphibole fibres, such as tremolite, that contaminate the chrysotile.
Part of the mechanism of the clearance of asbestos fibres is through lymphatic drainage and the pleural cavities. Mechanical irritation and inflammation is the presumed initiating mechanism for the pleural scarring. Typically few fibres are found in pleural plaques. When present, the fibres are preferentially chrysotile. The plaques usually occur on the parietal pleura and are acellular collagen that may calcify. When the plaques are found on the visceral pleura, they may extend into an interlobar fissure. Individuals who develop a benign pleural effusion are likely to go on to have diffuse pleural thickening, which involves the visceral pleura. Diffuse pleural thickening may also occur from confluence of smaller parietal pleural plaques or extension of subpleural interstitial fibrosis. Rounded atelectasis from both parietal and visceral pleural scarring and partial collapse of adjoining lung tissue can mistakenly appear as a tumour on a CXR.
The effects of long-term exposure to asbestos typically don’t show up for 10 to 40 years after initial exposure. Asbestosis signs and symptoms can include:
- Shortness of breath
- A persistent, dry cough
- Loss of appetite with weight loss
- Fingertips and toes that appear wider and rounder than normal (clubbing)
- Chest tightness or pain
When diagnosing asbestosis, your GP will first ask about your symptoms and listen to your lungs with a stethoscope (a medical instrument used to listen to the heart and lungs).
If your lungs have been affected by asbestos, they will usually make a crackling noise when you breathe in.
Your GP will also ask about your work history, particularly about periods when you may have been exposed to asbestos, how long you may have been exposed, and whether you were issued with any safety equipment, such as a face mask, when you were working.
REFERRAL TO A SPECIALIST
If asbestosis is suspected, you will be referred to a specialist in lung diseases for tests to confirm any lung scarring. These may include:
- a chest X-ray – to detect abnormalities in the structure of your lungs that could be caused by asbestosis
- a computerized tomography (CT) scan of the lungs – which produces more detailed images of the lungs and the membrane covering the lungs and can help identify less obvious abnormalities
- lung function tests – to assess the impact of damage of the lungs, determine how much air your lungs can hold and assess how well oxygen crosses the membrane of the lungs into your bloodstream
Before confirming a diagnosis of asbestosis, the chest specialist will also consider and rule out other possible causes of lung inflammation and scarring, such as rheumatoid arthritis.
There’s no treatment to reverse the effects of asbestos on the alveoli. Treatment focuses on slowing the progression of the disease and relieving symptoms. You’ll need routine follow-up care, such as chest X-rays and lung function tests, at regular intervals depending on the severity of your condition.
To ease breathing difficulty caused by advanced asbestosis, your doctor might prescribe supplemental oxygen. This is delivered by thin plastic tubing with prongs that fit into your nostrils or a mask.
If your symptoms are severe, you might be a candidate for a lung transplant.