Generation, protection and health effects of nano-sized dust in the ferroalloy industry

Material production is one of the largest land-based industries in Norway and encompasses several plants with different end-products. The DeMaskUs project has worked with 14 different smelters, producing ferrosilicon, silicon, ferromanganese, silicomanganese and silicon carbide. Common features for all these processes are that they form dust, fume and gas. The plants are continuously working to reduce exposure, but the use of respirators is still necessary in many places even today. In the DeMaskUs project, we wanted to find out more about the ultrafine particles, for example how they form and the effect of various dust-reducing efforts. We wanted to study whether brain cells grown in a laboratory would take harm from the dust and we anted to find ways to improve the use of the respirators. Through melting trials in the laboratory, it was documented that dust is formed in different manners depending on the alloy and that the amount and appearance of the particles formed depend on the temperature of the melt. Increased temperature typically results in more dust. Ultrafine particles from silicomanganese contained somewhat different elements than the produced alloy and the composition depend on the quality of the raw materials. This means that the production process has a large impact on what type of dust is formed, how much and what it contains. In addition, experiments showed that attempts to reduce the fuming by use of water spray near the melt during casting had a reducing effect on ferromanganese but led to increased fuming from silicon. This shows the complexity of these processes and that measures which are effective in one smelter may not necessarily give the same effect in another. To examine possible effects of ultrafine dust on cells, human brain cells ? astrocytes ? were exposed for three types of dust. It was dust particles form industrial production of silicon carbide and lab generated dust from silicon- and silicomanganese melts. The astrocytes are important support cells in the brain and inflammatory mechanisms in these cells are assumed to contribute to neurodegenerative diseases like Alzheimers. At low doses of dust, there was no significant effect on cell death, DNA-damage or inflammatory responses in the cells. At high doses however, the biomarker amyloid precursor protein, observed in the context of neurodegenerative diseases, was activated and the cell-cell communication was disturbed. This shows that central functions in the cells seem to be robust against ultrafine dust in short term trials with low doses. The results are not directly applicable to the development of diseases in humans but shows that minimising the exposure is important as a precautionary measure. To say something about whether the respirators used were the most suited, quantitative mask fit tests were carried out on smelter workers. Particles are then measured inside the mask and compared to the particle concentration outside the mask to assess leakage between mask and face. 37% of those tested did not pass the test with the respirator they usually use so they had been using a mask with insufficient protection. There was variation between mask models and some persons could use all masks while for others none of the selected masks fit. It was more difficult to find mask suited for women (due to smaller faces) and beard lead to leakage. These results show the importance of personal adaptation of protective equipment. The individual attitudes toward use of respirators was a determining factor for whether masks were used on an every day basis. Several practical factors like discomfort, warmth and difficult breathing were the main reasons for not using masks. Also problems with condensation on goggles and communication were important. Several of these challenges can be improved by better personal fit. A mask without leakage will feel more comfortable and give less condense.

As a direct effect of DeMaskUs, corporate standard procedures are revised, e.g. with new routines in procurement of masks to ensure good fit for different face shapes. To ensure that operators use the right dust masks, fit testing must be carried out continuously. From a plant OHS-perspective, the respiration fit testing and intervention are the most important project results. The course ("Dust and Health") was seen as highly relevant and the videos and other material from the course have been distributed to OHS-staff to be used in the future. The practical recommendations are implemented widely, for example through internal HSE days at the plants where researchers from DeMaskUs continues to participate. The fundamental research results on particle generation are important as all dust reducing process improvements are based on scientific knowledge. The cell viability tests confirm that keeping occupational exposure low does prevent negative health effects.

In the ferroalloy and SiC industry, emissions of ultrafine, oxide-based dust originating from different production processes, have been documented. The origin and health effect of these particles is, however, not well known. The proposed project, a collaboration between the ferroalloy industry, SiC industry SINTEF, NTNU, UNN, STAMI and St. Olavs hospital, is divided in three main work packages (WP): -WP 1: Dust formation mechanisms and kinetics -WP 2: Protection and human behaviour -WP 3: Neuroinflammatory health effects -WP1 aims to develop a fundamental understanding of the nanosized dust formation mechanisms and the characteristic properties of these particles (size distribution, composition) under various, process related conditions, with specific focus on FeSi, SiMn, FeMn and SiC production. -WP2 seeks to a) identify a selection of RPEs with optimal characteristics for the exposure conditions in the smelter industry b) identify psychological factors that interfere with actual use/non-use of RPEs. Based on the results from the psychological assessment, suggest intervention strategies that better facilitate desired behaviour and thus increase the probability of actual and correct RPE use among the workers. -WP 3 seeks to i) establish a human in vitro cell model, ii) adopt protocols for alloy particle preparation, dispersion and exposure of cells in vitro, iii) investigate cellular uptake of the particles, and iv) examine biomarkers of inflammation and oxidative stress after exposure of the cells to well characterised respirable alloy particles. This WP will evaluate these biomarkers for their relationship to particle characteristics, given by WP1. The project will train 2 PhD and 1 Post Doc for recruitment to industry and the research area.