Assessment of deposited surface of airborne ultrafine particles from welding processes

Abstract: Welding is the principal industrial process used for joining metals. However, it can produce dangerous fumes that may be hazardous to the welder's health and it is estimated that, presently, 1-2% of workers from different professional backgrounds are subjected to welding fume and gas action. The influence of very ultrafine particulate, lying in the nanoparticles range, on human health has been pointed to be of much concern as airborne nanoparticles are resulting both from nanotechnologies processes and also from macroscopic common industrial processes such as welding. In fact, nanotoxicological research is still in its infancy and the issuing and implementation of standards for appropriate safety control systems can still take several years. Yet, the advanced understanding of toxicological phenomena on the nanometre scale is largely dependent on technological innovations and scientific results stemming from enhanced R&D. Meanwhile, the industry has to adopt proactive risk management strategies in order to provide a safe working environment for their staff, clients and customers, and obtain products without posing health threats at any point of their lifecycle. Understanding the relationship of airborne nano sized particulate and human health, under different environmental conditions is of great importance for improving exposure estimates and for developing efficient control strategies to reduce human exposure and health risk and for establishing, evaluating and improving regulations and legislation both on air quality, airborne emissions and the incorporation of nano sized materials in other products and commodities. Mass measurement methods are not sufficiently sensitive for airborne nanoparticles and are not sensitive toward the specific health relevant properties of nanoparticles. The most sensitive concentration measured in this particle range (< 100 nm diameter) is the number concentration. As already pointed out, surface area is a relevant metric for nanoparticles, as most of the processes in the human body environment take place via the particle surface, which is increasing significantly with decreasing particle size in the nanometer size range for the same amount of mass. A Nanoparticle Surface Area Monitor, TSI, Model 3550, was used. This equipment indicates the human lung-deposited surface area of particles expressed as square micrometers per cubic centimeter of air (µm2/cm3). Tests for exposure assessment were made over different welding procedures using different welding parameters and also different sampling locations. The measured deposited area was expressed as alveolar due to the reduced size of the emitted particles. The study clearly demonstrated the existence of nanoparticles in welding of carbon steel and aluminum, which are clearly dependent from the distance to the welding front and also from the main welding parameters. It should be noted that, although measured parameters such as the deposited area and the dose per lung area, are elevated when compared with baseline values, they cannot, at this stage, be ascertained as toxicity indicator.