The human health and environmental impacts of airborne particles are closely linked to their size, which determines their behavior in the air. Size is also a relevant factor for their potential toxicity. Ultrafine particles (UFPs) are of particular concern due to their high number concentration and large surface area relative to mass. These particles can deposit deep in the pulmonary region, from where they may enter the bloodstream, leading to inflammation and oxidative stress associated with various diseases. Given these risks, understanding emissions and exposure to UFPs is critical for public health (ILAQH White Paper on Ambient Ultrafine Particles, 2019). Consequently, assessing the potential risks of industrial nanoparticle emissions is a vital component of comprehensive workplace safety evaluations.
Why Size Matters: The Toxicity of Ultrafine Particles
This article presents a case study on the potential health risks associated with nanomaterial exposure during stainless-steel laser cutting in industrial settings. Data were collected to assess worker exposure during metal cutting operations. The study was inspired by the Nanoparticle Emission Assessment Technique (NEAT), developed by the NIOSH nanotechnology field research team, which aims to evaluate airborne nanomaterial concentrations in workplaces. NIOSH recommends a "multi-metric approach," incorporating parameters such as particle count, size, mass, and surface area. Real-time measurements are essential for ensuring high accuracy and repeatability, as UFP concentrations can fluctuate both temporally and spatially (M. Methner et al., 2010, Part A & B).
Case Study: Measuring Nanoparticle Emissions During Laser Cutting
The experiments were conducted in cooperation with the Institute of Industrial Engineering of the Technical University of Košice and the European Science and Research Institute in Slovakia. The results were presented at the Annual Conference of the Czech Aerosol Society in 2024.
Methodology
A case study on potential health implications of exposure to nanomaterial during the industrial stainless-steel metal laser cutting process is presented here. Data were collected to analyze workers exposure during the metal cutting operation. This study approached the Nanoparticle Emission Assessment Technique (NEAT) developed by the NIOSH nanotechnology field research team to evaluate airborne nanomaterial concentrations in the workplace. NIOSH recommends a “multi metric approach” such as particle count, size, mass and surface area.
This study utilized two advanced portable instruments to monitor particle emissions during a standard laser cutting operation:
- Optical Particle Sizer (OPS) 3330: Measures particle size and concentration across a broad range.
- NanoScan SMPS™ 3910: Specifically designed for detecting nanoparticles down to 10 nm.
The instruments were placed above the laser cutting machine, with measurements taken at one-minute intervals. The process began by establishing a baseline indoor air quality (background particle size distribution PSD and particle number concentration PNC) before focusing on emissions during a continuous 36-minute laser cutting operation.
Key Findings
Measurements revealed significantly elevated PNCs of UFPs throughout the production area. Background PNC fluctuated around 110,000 #/cm³, with no readings below 100,000 #/cm³. Although no formal occupational limits exist for UFPs, this concentration is concerning. For comparison, WHO guidelines associate potential health risks with PNCs exceeding 10,000 #/cm³ (24-hour average) or 20,000 #/cm³ (1-hour average).
During continuous laser cutting, PNCs in the breathing zone exceeded 1 million #/cm³, peaking at 4 million #/cm³ at the start of operations. Nearly all emitted particles measured below 250 nm, with dominant peaks at 65 nm and 100 nm.
This trend persisted throughout the measurement period, with intervals corresponding to active cutting phases.
Given the high surface area of nanoparticles relative to their mass, they exhibit greater biological activity, which increases potential health risks for exposed workers (Gurr et al., 2005).
High Number of Nanoparticles Emitted
The measurements taken during standard daily operations in the metal laser cutting process demonstrated high particle number concentrations (PNC) of nanoparticles emitted during the industrial process. Since the particle emission intervals clearly correspond to the cutting operation, suitable abatement measures should be considered. A study in a similar facility with a laser cutting process reported PNCs below 5000 #/cm³, highlighting the potential for emission reduction. However, to gain a more comprehensive understanding, further studies, including detailed chemical analysis, are recommended.
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References
Gurr, J.R., Wang, A.S., Chen, C.H., & Jan, K.Y. (2005). Ultrafine titanium dioxide particles in the absence of photoactivation can induce oxidative damage to human bronchial epithelial cells. Toxicology, 213(1-2), 66-73. https://doi.org/10.1016/j.tox.2005.05.007
Methner M. et al., 2010, “Nanoparticle Emission Assessment Technique (NEAT) for the Identification and Measurement of Potential Inhalation Exposure to Engineered Nanomaterials — Part A,” Journal of Occupational and Environmental Hygiene, 7: 127-132.
Methner M. et al., 2010, “Nanoparticle Emission Assessment Technique (NEAT) for the Identification and Measurement of Potential Inhalation Exposure to Engineered Nanomaterials —Part B: Results from 12 Field Studies,” Journal of Occupational and Environmental Hygiene, 7: 163–176.
White paper on ambient ultrafine particle evidence for policy makers. Queensland University of Technology's International Laboratory for Air Quality and Health (ILAQH), 2019, https://research.qut.edu.au/ilaqh/2019/11/08/white-paper-on-ambient-ultrafine-particle-evidence-for-policy-makers-published-on-the-efca-website/
WHO Global Air Quality Guidelines, 2021, https://www.who.int/publications/i/item/9789240034228