Asbestos and Cancer: Understanding the Direct Link

Asbestos is a naturally occurring mineral. In the past, it was widely used in industry due to its insulating and heat-resistant properties. However, the association between asbestos exposure and the development of cancer has been known since 1943, but due to the timings and location of this discovery, changes weren’t implemented quickly enough around the world. As such, asbestos is known as the number one cause of work-related deaths across the world with around 90,000 people dying from asbestos-related diseases each year. In this article, we’ll explore the link between asbestos and different forms of cancer, including mesothelioma. 

What is asbestos?

Asbestos is a term that describes six naturally occurring fibrous minerals. These all contain thin fibrous crystals in strands and are mostly defined by their colour. These are:

• Chrysotile (white asbestos)
• Tremolite
• Crocidolite (blue asbestos)
• Amosite (brown asbestos)
• Anthophyllite
• Actinolite

The substance is mined directly from the ground in various locations around the world. The biggest producer in the world is Russia, which produced 700,000 metric tonnes of asbestos in 2022. Kazakhstan, Brazil and China are also leading asbestos mining countries. The mineral resembles wood when unprocessed and is mined directly from an open pit. When it is processed it looks like fluffy fibres.

Though asbestos mine production has fallen, the product is still consumed in various places around the world. The Middle East and Asia, for example, use around one million metric tonnes each year. 

The types of asbestos are divided into groups: amphiboles and serpentine. Chrysotile is the most widely used of minerals, accounting for around 95% of all asbestos used globally. This is serpentine asbestos. These fibres are flexible and soft. They’re not as dangerous as those that come from crocidolite, amosite, tremolite, anthophyllite and actinolite. These fibres are needle-like and brittle and are classed as amphiboles.

Asbestos is naturally resistant to fire, electricity, chemicals and heat. It is for these reasons that the substance became the perfect additive for products used in construction or other industries when fire prevention and chemical exposure occurred.

Asbestos: The discovery of minerals

Although asbestos was only really used towards the end of the 19th century, it is believed that ancient civilisations some 4,500 years ago used it to strengthen cooking equipment. It’s also believed that the fibres were used to make wicks in candles and lamps and cloths used for embalming in ancient Egypt. 

What it’s used for in the modern era

During the Industrial Revolution, asbestos gained popularity, particularly in Great Britain. Asbestos started being used as an insulator for machinery that facilitated the Industrial Revolution like kilns, ovens, turbines and steam pipes, for example. This caused an increase in demand for the substance, which triggered the first mines to be opened in the late 19th century. The first were in Quebec, Canada, shortly followed by South Africa, Australia and Russia. 

Some 20 years later, doctors began noting lung diseases in their patients who had worked with asbestos. Despite these health concerns, the substance continued to gain popularity and became an important material for the construction of the US railroad and also in the shipping, automobile and construction industries.

How does asbestos exposure occur?

Despite the growing concerns around asbestos use in the early 20th century, it wasn’t until 1906 that the first death due to asbestos exposure was documented. Exposure can occur due to a range of mechanisms. The fibres don’t evaporate or dissolve and are mechanically strong. They won’t degrade biologically either. 

By 1965, there was a clear link reported in an epidemiological study called ‘Mesothelioma of Pleura and Peritoneum Following Exposure to Asbestos in the London Area’ by Hilda Thompson and Muriel Newhouse. This study explored 83 cases of mesothelioma and tracked the occupations of the victims, which showed a clear correlation to asbestos. Those included in the study had either worked with asbestos or lived close to an asbestos factory.

People are exposed to asbestos due to contact with building materials or other asbestos-containing products. However, this doesn’t automatically make the materials dangerous. It is only when the products containing asbestos are broken or damaged that the dangerous fibres are released. These are then airborne and can be breathed in. It is also possible to consume small amounts of asbestos fibres if there is ground contamination near water sources or crops. 

The different ways of asbestos exposure: Occupational

People who are particularly vulnerable are those who are involved in demolition, asbestos removal and building maintenance. Construction workers might be exposed to ACMs (asbestos-containing materials) that are present in roofing, flooring and insulation. 

Asbestos was also commonly used in shipbuilding due to being fire-resistant. Shipyard workers, therefore, have the potential to be exposed to asbestos at work. 

Other employees in a range of industries like manufacturing, automotive, power plants, etc. may be exposed to the substance through working with machinery, insulation materials and equipment. 

The different ways of asbestos exposure: Environmental

Asbestos is a naturally occurring mineral. People living close to asbestos mines or asbestos deposits could be exposed to fibres that are released from the mineral due to weathering. The fibres are dangerous due to being airborne and so lots are released during the mining process. These can then travel through the air and be inhaled by nearby individuals.

The different ways of asbestos exposure: Secondary exposure

It is also possible to be exposed to asbestos through secondary exposure, when those who work with the substance bring fibres home on their skin, hair or clothing. This can be a particular problem for anyone in the home who is responsible for washing work clothes. 

The link between asbestos and cancer

Nowadays, the link between asbestos and cancer is well-established in scientific research. Asbestos is a human carcinogen. It’s known to cause four main cancers:

• Mesothelioma
• Lung cancer
• Laryngeal cancer
• Ovarian cancer

It is also possible that it causes pharyngeal, colon and stomach cancers. 

As well as malignant diseases, there are also non-malignant diseases linked to asbestos. These include:

• Asbestosis
• Pleural thickening
• Pleural effusion
• Atelectasis
• Peritoneal effusion
• Pericardial effusion
• Hyaline pleural plaques

Though not malignant, these can still be life-threatening.

Mesothelioma

Mesothelioma is a cancer that develops in the lung lining. Around 2,700 people in the UK are diagnosed with this each year and most of these are in individuals over the age of 75. More men are affected than women, likely due to their past working environments. 

This condition is almost always caused by asbestos exposure. The asbestos fibres are inhaled and become stuck in the lungs, which causes damage over time. Most people who get mesothelioma would have been exposed to asbestos decades earlier. 

In the UK, asbestos was banned at the end of the 20th century, which means there are fewer incidents of exposure now. It is believed that between 20% and 30% of mesothelioma cases have no direct link to asbestos exposure, however.

A diagnosis of mesothelioma is terminal. There is no cure and any treatments are palliative. Around 2,500 people die from mesothelioma each year currently, but cases are expected to drop due to the banning of the substance.

Studies

A study based in Broni, Italy of 188 people who died from asbestos-related diseases showed that 80% died of mesothelioma. A further 11% died of asbestosis. Others died of lung cancer, other tumours or other cardiopulmonary pathologies. For those with occupational exposure (109/188), 67% died of mesothelioma. For household exposure (i.e. family members of someone who worked with asbestos), 100% died of mesothelioma. 

Mechanisms of asbestos-induced cancer

The mechanisms of asbestos-induced cancer are complex. There is a combination of oxidative stress, genetic damage and inflammatory responses involved. Asbestos fibres are thin and needle-like. This makes them able to penetrate deep into the lungs during inhalation. These physical characteristics are what make them carcinogenic. Here are some of the mechanisms involved:

• Chronic inflammation: The inhalation of asbestos fibres causes an inflammatory response in the lungs. Immune cells called macrophages make an attempt to remove the fibres but cannot break them down. As such, the inflammation is persistent and the immune system continues to respond to this presence. When there is chronic inflammation, signalling molecules promote cell proliferation.
• Oxidative stress: Asbestos fibres cause reactive oxygen species (ROS) to be produced. These are reactive molecules that cause damage to components of cells, including lipids, proteins and cell DNA. When the DNA is damaged, normal cellular function is disrupted, which contributes to the initiation of cancer cells.
• Genetic damage: The DNA damage caused by asbestos fibres causes mutations in cells. When there is an accumulation of mutations, normal cells can turn into cancer cells.
• Cellular responses: Asbestos fibres also interfere with signalling pathways for cells. As such, apoptosis (programmed cell death) is affected, allowing cells with DNA damage to accumulate further mutations.
• Persistence of asbestos fibres: Asbestos fibres won’t degrade in lung tissue so even if there is no further exposure, they can persist.
• Synergistic effects: Asbestos exposure is thought to have synergistic effects with other carcinogens. This means the combined effect of asbestos fibres with another carcinogen like tobacco smoke makes the problem worse.

Risk factors and vulnerable populations

Certain people and occupations are more at risk for developing asbestos-related cancers. Various factors increase a person’s susceptibility to its health effects. Identifying potential exposure and patients will allow for early detection and treatment. 

Occupational risk

Those most at risk of asbestos-related illnesses are those who have worked in the construction industry, including demolition and renovation work. Examples of contractors at risk include electricians, plumbers, insulators and labourers.

Asbestos was also used commonly in shipbuilding so individuals who have worked in ship construction, maintenance or repair would also be at risk of exposure to asbestos fibres. 

As expected, miners and millers involved in the extraction of asbestos and its processing are at an increased risk of exposure due to direct contact with the fibres. 

Other workers like those in chemical production, power plants and automotive manufacturing might also come across asbestos at work. 

Demographic factors

Asbestos-related diseases like cancer have a long latency period. Most people who are diagnosed are 50+. The peak incidence is in people in their 60s and 70s. Historically, men are more likely to get asbestos-related cancers due to their occupational exposures. Further risks occur in those who smoke tobacco as this combined with asbestos exposure increases an individual’s risk of developing cancer. 

Environmental exposure

As we saw through the study of Broni in Italy, environmental exposure as someone living close to an asbestos mine is a risk factor in the development of asbestos-related disease. There are also potential risks to those living in older homes that were built using asbestos-containing materials. While intact, these provide no risk. However, when homeowners complete renovations, this could be a problem.

Secondary exposure

There is also a risk to people who live with those working in high-risk occupations. This is because asbestos fibres can be brought home on clothing, skin and hair. 

Pre-existing health conditions

Those with pre-existing health conditions, especially those affecting the lungs like COPD or asbestosis, are more susceptible to developing asbestos-related cancer. 

Regulations and safety measures

Now the dangers of asbestos are fully known, there are lots of rules and regulations regarding its use and exposure to it. Here are some of the measures that have been put in place within the United Kingdom to protect people from asbestos-related diseases:

• 1931: The first industry regulations regarding asbestos were put in place. This included instructions to supress dust and provide medical examinations. The Asbestos Industry Scheme also brought the asbestos industry into the 1925 Workmen’s Compensation Act, which meant people who suffered from asbestos-related diseases were entitled to compensation.
• 1960: Shipbuilding and repairing regulations were introduced. This meant people were required to wear protective masks when undertaking removal work.
• 1967: The mesothelioma and asbestosis registers were established and these are still used today.
• 1969: Asbestos Regulations 1969 were introduced, which meant workers in factories, warehouses and power stations, for example, had to be protected.
• 1970: Crocidolite (blue asbestos) was banned voluntarily in the UK.
• 1980: Amosite was banned voluntarily.
• 1983: Asbestos (Licensing) Regulations were introduced, which required, among other things, that workers have medical examinations before starting work and every two years.
• 1985: Asbestos (Prohibitions) Regulations were introduced, which prohibited the initiation of asbestos insulation and the importation of amosite and crocidolite.
• 1987: Control of Asbestos At Work Regulations were revised.
• 1999: Asbestos (Prohibitions) Regulations amendment meant it was no longer legal to supply or use chrysotile or products containing it.
• 2012: Control of Asbestos Regulations (CAR). These are the latest regulations regarding asbestos in the UK. Specified asbestos works require workers to undergo medical surveillance every three years. Employers also have to keep a register of workers, the work they’ve done and how long it took them. This log must be kept with medical records for 40 years.

Treatment and support

Asbestos-related cancers like mesothelioma and lung cancer are challenging to treat. The prognosis is typically poor with treatment options varying depending on the progression of the disease. In most cases, treatment is palliative.

Treatment for asbestos-related cancers

Here are some options for treatment:

• Surgery: Depending on the location of the affected tissue and tumours, surgery might be performed. With mesothelioma, however, the surgery is usually for symptom relief rather than to cure the disease.
• Chemotherapy: This may be given before or after surgery or to treat advanced cases.
• Radiation therapy: This may be given to shrink tumours before or after surgery or alone.
• Immunotherapy: This aims to stimulate the immune system to recognise the cancer cells and attack them.
• Multimodal therapy: It is likely that patients use a combination of treatments to treat their condition and improve their symptoms.

Support for those with asbestos-related cancers

There are a range of organisations in the UK that can help those with an asbestos-related disease and their families. These include:

• Asbestos Victim Support: This is an organisation that provides information to help those through their illness and to give advice. There is also information about claiming compensation for the illness.
• HASAG: This is a charity founded by Lynne Squibb and Diane Salisbury in 2006 to help and support those affected by asbestos in the south, the south-east, London and the Home Counties.
• Asbestos Awareness: This is an organisation supporting those with an asbestos-related disease and their families.
• Asbestos Action: This is a membership group for those affected by asbestos. It’s a small charity that aims to support those affected by asbestos-related diseases.
• Mesothelioma UK: This is a charity specifically targeting those affected by mesothelioma and their families.

Final thoughts on asbestos and cancer

Though the use of asbestos in industry is now banned, asbestos exposure is still a huge problem. This is because any building built before 1999 could contain the substance and, therefore, could pose a risk to people in the event of its degradation or demolition. Thankfully, there is now awareness and so there are risk assessments and rules around the maintenance of buildings where asbestos could be in existence. Compliance with regulations is crucial for those working with asbestos, particularly due to its high latency period. Early detection through health checks is essential as this improves outcomes for those affected.