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Respirable Crystalline Silica Dust – The Next Asbestos?

Silicon is the most common element in the Earth’s crust after oxygen. Silicon dioxide, also known as silica, is formed from silicon and oxygen atoms and makes up about 59% of the Earth’s crust and silica is the main constituent of 95 percent of the known rocks.[1]

Silicosis is a form of occupational lung disease caused by the inhalation of crystalline silica dust. It is considered to be the most common chronic occupational lung disease in the world. It is estimated to affect thousands of workers every year. It is caused by the deposition of fine respirable dust, less than 10 micrometres in diameter, containing crystalline silica in the form of quartz, cristobalite or tridymite.

Classification of the disease, made according to severity, radiographic pattern, onset and speed of progression, includes: Simple Silicosis, Accelerated Silicosis, Complicated Silicosis and Acute Silicosis.

Simple Silicosis usually results from long term exposure to relatively low concentrations of silica dust and generally appears 10 – 30 years after first exposure. Radiographically, Simple Silicosis reveals a profusion of opacities or nodules less than 10mm in diameter, typically rounded, and appearing predominantly in the upper lung zones. In some cases it can progress to Complicated Silicosis, also known as Conglomerate Silicosis and Progressive Massive Fibrosis.

Accelerated Silicosis results from the inhalation of very high concentrations of silica dust. It develops in a pattern similar to that of Simple Silicosis, except the time from initial exposure to the onset of disease is shorter (5 – 10 years) and the progression to Complicated Silicosis is more rapid.

Complicated Silicosis: In some cases, fibrosis (hardening or scarring) of the lung tissue can occur when the nodules coalesce and reach a size of 1cm or more, with a consequent loss of function. According to the Health and Safety Executive[2], “Sufferers are likely to have severe shortness of breath and may find it difficult or impossible to walk even short distances or upstairs. The effect continues to develop after exposure has stopped and is irreversible. Sufferers usually become house- or bed-bound and often die prematurely due to heart failure.”

Acute Silicosis is a rare complication in which symptoms develop within the first weeks to 5 years after exposure to very high concentrations of silica.

Silicosis increases the risks of tuberculosis, kidney disease, arthritis, Chronic Obstructive Pulmonary Disease, chronic bronchitis and lung cancer. Whilst the impact of smoking on silica exposure is not clearly understood, there are studies which suggest that silica exposure and smoking act together to increase the risk of lung cancer.[3]

The HSE identifies occupations with exposure to respirable crystalline silica as including: quarrying, slate work, foundries, potteries, stonemasonry, construction work, and industries using silica flour to manufacture goods. Other trades are also affected, including those, such as: kitchen and bathroom installers, workers involved in fracking, those who work with artificial stone[4] and textile workers working with stone washed denim.[5] Artificial stone has a particularly high silica content – commonly 90% quartz combined with polymer resins and pigments which are heat cured. This can be compared with marble and limestone, said to contain “up to 2%” and granite or brick, “up to 30%”.[6] Papers by Leon-Jiménez and others suggest that workers with artificial stone demonstrated an aggressive form of silicosis with rapid progression in a high proportion of affected individuals even after cessation of exposure[7]

The current workplace exposure limit for respirable crystalline silica is 0.1mg/m3 expressed as an 8-hour time weighted average. Exposure to respirable crystalline silica is subject to the Control of Substances Hazardous to Health Regulations 2002.

Historically, silicosis was associated with steelworks, foundries, mines and quarries, but with the decline of those traditional industries, numbers of cases reduced. In March 2020, however, the All Party Parliamentary Group for Respiratory Health, Chaired by Jim Shannon MP, published a report, “Silica – The Next Asbestos?”,[8] in which it argued that in the UK, the workplace exposure limit (WEL) of  0.1mg/m3 is double that of other developed nations and made 10 recommendations, including reducing the WEL to 0.05mg/m3 and imposing statutory monitoring requirements to ensure that workers are not exposed above the limit. One of the findings of that report was that 600,000 UK workers are exposed to silica dust each year.

The British Occupational Hygiene Society welcomed the All Party Parliamentary Group report[9] at the time of its publication and has recently written to MPs in the Group to “follow the example of their counterparts in the Australian legislature, who have prompted the government by putting forward legislation in their own right”.[10]

The union Unite, with the assistance of Thompsons Solicitors, maintains a register for members who believe that have been exposed to silica dust at work. According to the Unite website, “The database allows us, and panel law firms, to collect information from members that may help support legal claims for other members who have been diagnosed with an illness linked to silica dust exposure.[11]

The number of recent reported cases dealing with silicosis is small.[12] However, the signs are that litigation arising out of respirable silica dust exposure is likely to be on the increase. That appears to have been the experience in the United States over the last two decades[13] and it would be surprising if the UK did not follow suit.

Insurers and solicitors requiring specialist barristers with experience of handling silicosis cases need look no further than the Disease Team at Crown Office Chambers. For further information, please contact James Wilkinson.

Written by Robert O’Leary.




[3] See, for example, “Silica exposure, smoking and lung cancer” (Brown, Occupational Medicine, Volume 59, Issue 2, March 2009)




[7] Leon Jiménez A and others “Artificial stone silicosis: rapid progression after exposure cessation” (Chest, 2020;158(3):1060-1068)





[12] Mark v Universal Coatings and Services [2018] EWHC 3206 (QB); Harry Mills v J P Barnes & Sons Ltd, 2013 WL8182338, Leeds County Court, HHJ Cockcroft; Vava & Others v American South Africa Ltd [2013] EWHC 2131 (QB)

[13] Is Silica the Next Asbestos? An Analysis of Silica Litigation and the Sudden Resurgence of Silica Lawsuit Filings, 32 Pepp L Rev 4 (2005)

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