Objective Artificial stone dust (ASD) contains high levels of ultrafine particles (UFP <1 µm) which penetrate deeply into the lungs. This study aimed to demonstrate the direct effect of UFP in the lungs of ASD-exposed workers on functional inflammatory and imaging parameters.
Methods 68 workers with up to 20 years of ASD exposure at the workplace were recruited from small enterprises throughout the country and compared with 48 non-exposed individuals. Pulmonary function test (PFT), CT, induced sputum (IS) and cytokine analyses were performed by conventional methods. The CT scans were evaluated for features indicative of silicosis in three zones of each lung. UFP were quantitated by the NanoSight LM20 system (NanoSight, Salisbury) using the Nanoparticle Tracking Analysis. Interleukin (IL)-6, IL-8 and tumour necrosis factor alpha (TNF-α) levels were measured by Luminex (R&D Systems).
Results Thirty-four patients had CT scores between 0 and 42, and 29 of them were diagnosed with silicosis. Content of the UFP retrieved from IS supernatants correlated negatively with the PFT results (total lung capacity r=−0.347, p=0.011; forced expiratory volume in 1 s r=−0.299, p=0.046; diffusion lung carbon monoxide in a single breath r=−0.425, p=0.004) and with the CT score (r=0.378, p=0.023), and with the inflammatory cytokines IL-8 (r=0.336, p=0.024), IL-6 (r=0.294, p=0.065) and TNF-α (r=0.409, p=0.007). Raw material of ASD was left to sedimentate in water for <15 min, and 50% of the floating particles were UFP. A cut-off of 8×106 UFP/mL in IS samples had a sensitivity of 77% to predict pulmonary disease.
Conclusions This is the first demonstration of an association between UFP-related decreased PFT results, worsening of CT findings and elevation of inflammatory cytokines, which may be attributed to high-dose inhalation of UFP of ASD at the workplace.
- exposure assessment
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Presented at This paper was an oral presentation at the ERS Conference, Paris 2018.
Contributors NO: PhD student, design and conduct of laboratory work, and first draft of the manuscript. ABS: clinical advisor. RK: toxicological studies. MRK: chief clinical occupational pulmonology department. EF: head of the research group, in charge of all coordination, and revision of the draft of the manuscript with final approval.
Funding Committee for Research and Prevention in Occupational Safety and Health in Israel (N0 56/13).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Ethical approval was granted by the Institutional Ethics Committee in the Tel Aviv Sourasky Medical Center. All participants gave written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
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