Link Between Occupational Silica Exposure and Systemic Sclerosis?

In the above article, we discuss the IIAC review on evidence in support of a link between occupational exposure to silica and connective tissue diseases, including systemic sclerosis.

Adding to the evidence base collated in the IIAC report, a new study has discovered higher levels of silica in the blood of systemic sclerosis patients than in control patients.

As discussed above, scleroderma is a group of diseases causing abnormal growth of connective tissue. It is triggered by the immune system attacking connective tissue under the skin and around internal organs. Systemic sclerosis is a type of scleroderma in which blood vessels and internal organs are affected, as well as the skin. It mainly affects women and usually develops in individuals between 30 and 50 years of age. Thick, tight patches of skin may manifest. In some cases, the muscles of the oesophagus can lose normal movement and the patient can find it difficult to swallow. Other symptoms include fatigue, weight loss and swollen painful joints. If the heart, lungs or kidneys are affected, a range of potentially serious problems, such as shortness of breath and high blood pressure in the lungs can develop[i].

Scleroderma treatments aim to relieve symptoms, prevent the condition from worsening, detect and treat complications and help patients to maintain use of affected body parts. Treatments include medication to improve circulation, medication to reduce immune system activity and slow down progression of the disorder, steroid medication for joint and muscle problems, moisturisers to keep affected skin supple, and medications for pain, heartburn and high blood pressure. In some severe cases, surgery may be needed to remove hard lumps under the skin or to loosen tight muscles.

Researchers took blood samples from 80 systemic sclerosis patients and 50 controls, living in an area where many worksites could potentially expose the indigenous population to silica[ii]. The participants also provided information about environmental and occupational exposures. Exposure to silica dust was reported by 55% of patients and 11% of controls. Blood samples of all exposed systemic sclerosis patients contained silica micro-particles and nano-particles and blood-silica levels were significantly higher in patients than in controls, increasing with severity of the disease. Further, higher blood-silica levels were detected in patients with a history of occupational exposure.

This study is, to the researchers’ knowledge, the first to find higher levels of silica in the blood of systemic sclerosis patients. As such, silica exposure may be associated with more severe development of systemic sclerosis.

Publication of the study has come at the same time as the Health and Safety Executive (HSE) has called for companies to review their health surveillance programmes to ensure that they are sufficient to detect changes in workers exposed to silica.[iii]

Dr Steve Forman, principal medical advisor at the HSE, recently appeared at the Society and Faculty of Occupational Medicine’s annual scientific conference. He said that workers exposed to crystalline silica should regularly undergo both X-ray screening and lung function testing – not one or the other. In some industries, such as construction, lung function testing is performed regularly, but X-rays are not. Symptoms of silicosis can take a long time to develop, and X-rays can detect early changes better than lung function testing. In the early stages of silicosis, lung function may not be affected, but changes may be seen on an X-ray.

 

[i] Scleroderma. NHS Choices. https://www.nhs.uk/conditions/scleroderma/ (Accessed 19 July 2018)

[ii] Ferri, C. et al. High serum levels of silica nanoparticles in systemic sclerosis patients with occupational exposure: possible pathogenetic role in disease phenotypes. Seminars in Arthritis and Rheumatism (2018). doi:10.1016/j.semarthrit.2018.06.009 https://www.sciencedirect.com/science/article/pii/S004901721730700X (Accessed 19 July 2018)

[iii] Workers at risk of silica dust exposure need both x-ray and lung function screening, warns HSE. Personnel Today. https://www.personneltoday.com/hr/several-tests-should-be-used-to-identify-respiratory-diseases-says-hse/ (Accessed 20 July 2018)