On the Relationship between Exposure to Particles and Dustiness during Handling of Powders in Industrial Settings

Exposure to ceramic powders, which is frequent during handling operations, is known to cause adverse health effects. Finding proxy parameters to quantify exposure is useful for efficient and timely exposure assessments. Worker exposure during handling of five materials [a silica sand (SI1), three quartzes (Q1, Q2, and Q3), and a kaolin (K1)] with different particle shape (prismatic and platy) and sizes (3.4-120 μm) was assessed. Materials handling was simulated using a dry pendular mill under two different energy settings (low and high). Three repetitions of two kilos of material were carried out per material and energy conditions with a flow rate of 8-11 kg h -1 . The performance of the dustiness index as a predictor of worker exposure was evaluated correlating material's dustiness indexes (with rotating drum and continuous drop) with exposure concentrations. Significant impacts on worker exposure in terms of inhalable and respirable mass fractions were detected for all materials. Mean inhalable mass concentrations during background were always lower than 40 μg m -3 whereas during material handling under high energy settings mean concentrations were 187, 373, 243, 156, and 430 μg m -3 for SI1, Q1, Q2, Q3, and K1, respectively. Impacts were not significant with regard to particle number concentration: background particle number concentrations ranged between 10 620 and 46 421 cm -3 while during handling under high energy settings they were 20 880 - 40 498 cm -3 . Mean lung deposited surface area during background ranged between 27 and 101 μm 2 cm -3 whereas it ranged between 22 and 42 μm 2 cm -3 during materials handling. TEM images evidenced the presence of nanoparticles (≤100 nm) in the form of aggregates (300 nm-1 μm) in the worker area, and a slight reduction on mean particle size during handling was detected. Dustiness and exposure concentrations showed a high degree of correlation (R 2 = 0.77-0.97) for the materials and operating conditions assessed, suggesting that dustiness could be considered a relevant predictor for workplace exposure. Nevertheless, the relationship between dustiness and exposure is complex and should be assessed for each process, taking into account not only material behaviour but also energy settings and workplace characteristics. © The Author(s) 2018.This research was funded by the Spanish MINECO (CGL2015-66777-C2-1-R, 2-R), Generalitat de Catalunya AGAUR 2014 SGR33, the Spanish Ministry of the Environment (13CAES006) and FEDER (European Regional Development Fund) “Una manera de hacer Europa”. M.C. Minguillón acknowledges the Ramón y Cajal Fellowship awarded by the Spanish Ministry of Economy, Industry and Competitiveness. The authors also acknowledge the company MOLARIS for their support with technical information on the mill used. The authors declare no conflict of interest relating to the material presented in this article.Peer reviewe