Characterization And Toxicological Evaluation On The Airborne Particles Of A Wire-cut Electrical Discharge Machining Workshop

Objective:To investigate the airborne particles number concentration, size distribution,mass concentration, elemental composition, morphologic characters, and toxicologicalassessment from a wire-cut electrical discharge machining workshop. To measure theairborne particles exposure level and its biological effect, to evaluate its occupationalexposure risk, propose the way to reduce harm, and also inform the design ofparadigms for airborne characterization in WEDM-like workplaces.Method:Three instruments (SMPS, OPS, CPC3007) were employed to characterize totalparticle number concentration (TNC) and its size distribution with size range2.89nm-10μm. MOUDI125B was used to collect size-fractionated aerosol particlesamples from10nm to10μm for gravimetric, elemental, morphological analysis andtoxicological assessment. The particle mass concentration was calculated by WeightMethod, elemental analysis by ICP-MS/OES and EDS, morphological analysis byTEM/SEM.16HBE cell line was co-cultured with particles to assess particle toxicityand ROS production ability.Results:The aerosol particle TNC in WEDM was bimodal with peak maxima at workingdaytime10:00am and3:00pm. The TNC peak was as high as1.2×105particles percm3which was about6times higher than the background. Particles larger than100nm could settle down quickly after cutting pause, while nanoparticles could stay muchlonger in the air.90%of aerosol particles was smaller than100nm with peak maximaat40nm. Cutting different workpieces (Cu, Stainless steel, Al) could produceparticles with TNC in the same order of magnitude105. Particle TNC from cutting Al was about3times higher than Cu/Stainless steel but no significant difference betweenCu and Stainless steel. The mass concentration of airborne particles PM0.1, PM0.1-1.0,PM1.0-10, PM>10was19.5μg/m3,204.2μg/m3,143.0μg/m3,58.5μg/m3, withproportion4.6%,48.0%,33.6%,13.8%, respectively. Airborne particles contained Cu29.3μg/m3, Fe135.8μg/m3, Al60.7μg/m3which were from three different kind ofworkpieces. Airborne particles larger than56nm could cause cytotoxicitysignificantly (P<0.05). Airborne particles size range60-100nm,200-300nmand>1.0μm could induce cell oxidative stress (P<0.05).Conclusion:WEDM can produce a large amount of airborne nanoparticles leading to TNCincreasing of workplace atmosphere. Workers in such workplaces have risks toexposure to airborne nanoparticles. Airborne particles decrease the cell viability andinduce oxidative stress in vitro, which prompts that such airborne particles may doharm to works’ health. Effective measures have to be conducted to protect works.