Editors

IrmeliLindstöm

HeikkiFrilander

Silicosis

Silicosis presents as nodular fibrosis of the lung tissue particularly in the upper lung fields.
Susceptibility to lung cancer and pulmonary tuberculosis are increased.
Workers at risk of developing occupational silicosis should go through an initial health examination and then regular follow-up examinations every three years.

Within European Union, the employer and employee associations have agreed on reducing exposure to crystalline silica dust. The Good practice guide linked to the agreement provides guidance for different industrial sectors in achieving this goalhttp://guide.nepsi.eu/.
The primary goal is to prevent exposure to crystalline silica (silicon dioxide) dust, i.e. quartz, cristobalite or tridymite. This is achieved either by the development of working methods, by technical modifications of the work environment (dust control) or as the last choice by wearing of personal P2 respiration protectors.
Exposure may occur in the following occupations:
- mining, quarrying, stone work, construction, and foundry work
- manufacture of glass, porcelain, enamel, clay and stone products
- sand blasting and grinding
- production and dismantling of refractory material
- construction industry: demolishing old structures for renovation work, dry grinding and clearance. In addition to siliceous earth, asbestos has been used for example in the manufacture of pipe lagging (exposure to mixed dust).

Crystalline forms of silica usually cause chronic pulmonary fibrosis, silicosis (grinders' disease).
The patients with silicosis usually have a history of silica dust exposure over a time period exceeding 10 years, and the latency period has usually been over 20 years.
The more rare acute silicosis may already develop within a few weeks or months after an exceptionally heavy exposure and may rapidly lead to respiratory failure.
Mixed dust exposure (simultaneous exposure to a mixture of mineral dusts) may cause an irregular pulmonary fibrosis (mixed dust pneumoconiosis).
Silicosis predisposes the individual to pulmonary tuberculosis (silicotuberculosis) which is considered as an occupational disease if the original silicosis was classified as such.
IARC (International Agency for Research on Cancer/WHO) classifies crystalline silica dust as carcinogenic to humans (Group 1). Lung cancer in patients with silicosis is compensated as an occupational disease.
Quartz dust and other industrial dusts, gases and fumes have been shown to be associated with chronic bronchitis and COPD. An occupational disease should be suspected in a COPD patient with exposure to quartz or other dusts if the smoking history is less than 10 pack years.

Chest x-ray typically shows nodular fibrosis in the upper lung fields and calcification of hilar lymph nodes. HRCT shows much more clearly the different changes in silicosis. In the acute form, ground-glass opacities may be seen in the lung parenchyma.
In a slowly progressing disease the patient remains symptomless for a long time. At a later stage and in the acute form the symptoms may include an irritative cough and dyspnoea.
Fine mid- and end-inspiratory rales can be heard on auscultation.
Lung function tests may initially show a decrease in vital capacity. As the disease progresses, obstruction and diffusion impairment may be observed.

Significant exposure to silica dust
Even when abnormalities on radiological findings are visible the patient may remain asymptomatic.
E.g. sarcoidosis should be excluded in the differential diagnostics.
Sometimes lung biopsy
Pulmonary function tests help to determine the degree of disability.

There are specific national instructions concerning regular surveillance of workers at risk of developing occupational silicosis.
- The worker should go through an initial health examination and then regular follow-up examinations every three years.
- The initial examination should include medical history, clinical examination, chest x-ray (PA and lateral views) and spirometry.
- The follow-up examinations are contain the same investigations, except that the need for a chest x-ray is evaluated on a case-by-case basis, as the person's age and cumulative exposure increase.
- Consult local guidance for more information.
If the findings in an exposed person suggest pneumoconiosis, the clinical diagnostic examinations should be performed in a specialized hospital department or other specialized unit.
The necessary measures concerning the insurance coverage of an occupational disease must be taken care of.
Because the diseases due to the exposure may emerge only after many years, health examinations should be continued also after the exposure has ceased, if the exposure has been sufficient to cause silicosis. Occupational health service should guide persons who end their employment, retire or become unemployed to seek health checks at an appropriate place.

The European network for silica (NEPSI). Good practice guide http://guide.nepsi.eu/