Experimentally recreated workplace environments contain submicron crystalline silica particles, including ultrafine particles, which have been identified in the mediastinal lymph nodes of construction workers.

Abstract

Although ultrafine particles are suspected to contribute significantly to occupational exposure to crystalline silica, they have not yet been definitively identified in workplaces or human tissues. Particles were generated in three 60-minute tests in a glove box: cutting kerb or granite pavement, drilling solid cinder block. The particle concentrations per cm³ of air in the box and their mean size were analysed online and using transmission electron microscopy and energy dispersive X-ray analysis (EDX). 17 mediastinal lymph node (MLN) samples from construction workers who underwent lung cancer surgery were examined by Fourier transform infrared spectroscopy (FTIR) and 8/17 by scanning electron microscopy (SEM) with EDX analysis. The particle concentration was high when cutting kerb or granite pavement (10 000-20 000 cm^-3 and 50 000-160 000 cm^-3, respectively), while below 1000 cm^-3 for drilling cinder block. The aerosol consisted mainly of submicron emissions with a nanometric fraction (ie, <100 nm), showing two main modes: 351 nm to 16 nm for kerb, 407 nm to <16 nm for granite pavement and 310 nm to 17 nm for cinder block processing. Ultrafine silica particles were only identified in kerb and granite cutting samples.Analysis using FTIR revealed an Si signal in 15/17 of the MLN samples and SEM and EDX analysis detected geometric particle deposition with Si spectra, particularly nano-sized particles, in the eight analysed samples. Ultrafine silica particles are produced in conditions that mimic typical construction work processes, but the quantity produced varies according to the task. Similar characteristics were observed in ultrafine silica particles in both MLN samples and experimental aerosols.