Pneumoconiosis after sericite inhalation

Abstract

Background: Between 1997 and 1999 three sericite plant workers in Paraná, Brazil, were diagnosed with pneumoconiosis. Aims: To investigate and describe the radiological, clinical, and pathological changes in miners and millers exposed to sericite dust with mineralogical characteristics of inhaled dust. Methods: The working premises were visited to examine the sericite processing and to classify the jobs according to make qualitative evaluation. Respirable dust was collected and the amount of crystalline silica and particle size distribution were measured. Forty four workers were examined by a standard questionnaire for respiratory symptoms, spirometry, and chest x ray. Material from an open lung biopsy was reviewed for histopathological and mineralogical analysis, together with sericite samples from the work site to compare the mineral characteristics in lung lesions and work area. Results: Respirable dust contained 4.5-10.0% crystalline silica. Particle size distribution showed a heavy burden of very fine particles (23-55%) with a mean diameter of ,0.5 mm. Mean age of sericite miners was 41.0 (11.9) and mean number of years of exposure was 13.5 (10.1). In 52.3% of workers (23/44), chest radiographs presented a median category of 1/0 or above, and 18.2% (8/44) had a reduced FEV 1 . There was a significant association between exposure indices and x ray category. Histological studies of the lung biopsy showed lesions compatible with mixed dust fibrosis with no silicotic nodules. x Ray diffraction analysis of the lung dust residue and the bulk samples collected from work area showed similar mineralogical characteristics. Muscovite and kaolinite were the major mineral particle inclusions in the lung. Conclusion: Exposure to fine sericite particles is associated with the development of functional and radiological changes in workers inducing mixed dust lesions, which are distinct histologically from silicosis.

The importance of mineralogical composition for the cytotoxic and pro-inflammatory effects of mineral dust

“…However, the development of pneumoconiosis due to exposure to mica or other phyllosilicates seems to require prolonged exposure to very high concentrations of dust, and the disease-relationship is often confounded by exposure to other occupational hazards, such as quartz and asbestos [ 6 , 37 ]. Nevertheless, several case reports indicate that high exposure to mica dust may cause pneumoconiosis distinct from silicosis in the absence of other occupational hazards [ 38 – 44 ]. While the number of experimental studies is scarce, toxicity from exposure to mica has been reported.…”

Demonstrating the protective effect of a 70-year-old occupational exposure limit against pneumoconiosis caused by mica

“…Notably, ACGIH (2001) identified the compromising nature of a publication with such co-exposures (i.e., Vestal et al, 1943), and Vestal et al was the only previously used publication that was not also referenced by ACGIH in 2021. Regrettably, however, ACGIH (2021) introduced newer studies that were compromised for the same reasons (Algranti et al, 2005; Landas and Schwartz, 1991; Raymond, 2014). Respective studies were used by ACGIH (2021) but dismissed from consideration in this review because they must not contribute to a risk assessment for respiratory exposure to mica only.…”

Mica pneumoconiosis: a neglected occupational lung disease

“…In most cases, spirometric lung function showed both obstructive and restrictive patterns, and diffusion capacity of carbon monoxide yielded both normal and attenuated patterns. Radiological investigations in some participants showed pleural thickening associated with calcification, 3,4 whereas in others groundglass opacity associated with bilateral micronodules and hyperdense lymph nodes were observed. Critical evaluation de lineated typical features, which were unlike other pneumo conioses.…”

“…4,5 The use of advanced physicochemical analytical techniques, such as scanning electron microscopyenergy dispersive xray spectroscopy and analytical transmission electron microscopy of biopsy samples and bronchoalveolar lavage samples of patients with occupational exposure, confirmed the particles as pure mica. [3][4][5] One report 5 also showed an unusual autoimmune disease associated with mica pneumo coniosis.…”

“…It is well established that mica miners and millers are at increased risk of pneumoconiosis and that mica alone is fibrogenic, even in the absence of other potential occupational or environmental hazards, which are known to cause fibrosis. 1,[3][4][5] Mica pneumoconiosis is still considered a rare disease largely because occupational disease outbreaks occurring in the informal labour sector are not usually formally documented. Several studies 1,4 published in the past two decades provide substantial information about micaassociated pneumoconiosis and show that the disease has a complex set of clinical manifestations.…”