Introduction/framework/objectives

Pneumoconiosis are the most frequent occupational diseases. Silicosis is caused by inhaling breathable crystalline Silica. It is a diffuse interstitial fibronodular lung disease. Initially it is asymptomatic, however, it is usually progressive and without cure. The diagnosis is partially based on a history of professional exposure.

It is more prevalent in countries with considerable unemployment and/or little or no Health and Safety Surveillance at Work.

Methodology

This is a Bibliographic Review, initiated through a search carried out in January 2022, in the databases “CINALH plus with full text, Medline with full text, Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Cochrane Methodology Register, Nursing and Allied Health Collection: comprehensive, MedicLatina and RCAAP”.

Contents

Silica or silicon dioxide (SiO2) is made up of oxygen and silicon. In nature it exists in amorphous and crystalline forms. The International Agency for Research on Cancer (IARC) considered inhaled crystalline Silica as a human carcinogen (group 1), probably due to cellular damage, inflammation, oxidative stress and inhibition of clearance. Amorphous silica is not considered carcinogenic to humans (group 3).

Silicosis exists in all countries, but is more prevalent in the ones less developed, even realizing that the real incidence should be higher than the official one, due to the situation being underreported. In more developed countries, the incidence/prevalence has decreased, due to the improvement of working conditions.

Exposure is relevant via inhalation; cutaneous and digestive tracts generally do not have important consequences in the work context.

The health risk varies with concentration, particle size- diameter, surface and shape (more dangerous if smaller), exposure time, type of silica (crystalline, tridymite and cristobalite are the most harmful, although more rare), density, water and lipid solubility, chemical reactivity, hygroscopic and electrostatic character, temperature, air speed and employee physical activity. Also important are gender, body area, age, general health status, previous pathologies and smoking- that is, individual susceptibility.

The particles can be inhaled, thoracic or respirable (the latter are able to settle in the lungs). The shape, size and density of dust will affect the behavior and penetration into the respiratory system. The respirable fraction consists of particles smaller than 10 micrometers, that is, they can reach the area where gas exchange takes place; larger than that, they are usually deposited in the nasal and thoracic region. Silica nanoparticles smaller than 100 nanometers can reach the bloodstream.

After inhalation, Silica particles are mainly deposited in the bronchioles and alveoli; if mucociliary clearance is not sufficient, inflammation (alveolitis) develops, which can lead to fibrosis and cancer. Macrophage activation generates free radicals/reactive oxygen species, which are not always attenuated by anti-oxidant defenses. Continued exposure enhances the release of cytokines which, in turn, activate more macrophages, neutrophils and lymphocytes; the increased production of collagen will then lead to said fibrosis, decreasing lung profitability and efficiency; that is, decreasing gas exchange; being that it can also reach the pleura.

Discussion and Conclusions

Despite the advances provided by an increasingly effective Health and Safety system, Silicosis is still a problem in some contexts, so it is necessary that the professionals working in these teams have reasonable knowledge regarding the sectors/tasks where it can occur, auxiliary diagnostic tests and other surveillance parameters, collective and individual protection measures, as well as possible implications for the classification of aptitude to work.

It would be relevant to better understand the national scenario, through the dissemination of investigations carried out in this context.

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