Cleaning as high-risk activity for respiratory particulate exposure during additive manufacturing of sand moulds and its preceding silica sand coating process.

IF 1.8 4区 医学 Q3 PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH
Ntoko Lucas Matlhatsi, Sonette du Preez, Cornelius J Van Der Merwe, Stephanus J L Linde
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引用次数: 0

Abstract

Background: Occupational exposure to respirable crystalline silica (RCS) is a known cause of respiratory diseases, such as silicosis and lung cancer. Binder jetting additive manufacturing (AM) uses silica sand coated with sulphonic acid as feedstock material and operators are potentially exposed to RCS during various activities associated with AM. This includes the cleaning of the AM machine and associated equipment. This study aimed to investigate particulate exposures associated with additive manufacturing of sand moulds and its preceding silica sand coating process.

Methods: The particle size distribution (PSD) and particle shape analysis of different forms of silica sand (virgin, coated, and used) was determined using a Malvern Morphologi G3 automated microscope and the structural characteristics was measured using X-ray diffraction (XRD). Personal exposure and area monitoring for airborne respirable dust and RCS were performed using MDHS 14/4 and NIOSH 7602, while real-time particle number concentrations of 0.3 to 10 µm sized particles was measured using the TSI Aerosol Particle Counter (APC). Monitoring was performed for 2 operators over 8 d and included 3 d of coating, one day of cleaning the AM machine, and 4 d of printing during which 3 identical parts were manufactured.

Results: According to the PSD analysis, virgin and used silica sand particles were mostly in the respirable size range (d(0.9) = 3.98 ± 0.72 µm; and d(0.9) = 6.51 ± 2.71 µm, respectively), while coated sand was mostly in the inhalable size fraction d(0.5) = 29.76 ± 42.91 µm). The wt% results of the XRD analysis for the bulk virgin, coated and used silica sand were 97.3%, 92.6%, and 96.8% quartz, respectively. Personal exposure to RCS exceeded the exposure limit of 0.1 mg/m3 when the operator used compressed air to clean the coating machine's filter (0.112 mg/m3) and exceeded the action level on the day the AM machine was cleaned (0.70 mg/m3). The results for real-time particle number concentrations of 0.3 to 10 µm sized particles showed peaks while the cleaning activities such as dry sweeping were performed.

Conclusion: The personal exposure to RCS was the highest on days when cleaning activities that used compressed air and dry sweeping took place. The high quartz content of the silica sand feedstock material and the respirable size of the virgin and used silica sand particles means that cleaning activities pose an RCS exposure risk to AM operators. Nine recommendations are made to reduce exposure to RCS during cleaning activities.

在砂模增材制造及其之前的硅砂涂层过程中,清洗是呼吸道微粒暴露的高风险活动。
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来源期刊
Annals Of Work Exposures and Health
Annals Of Work Exposures and Health Medicine-Public Health, Environmental and Occupational Health
CiteScore
4.60
自引率
19.20%
发文量
79
期刊介绍: About the Journal Annals of Work Exposures and Health is dedicated to presenting advances in exposure science supporting the recognition, quantification, and control of exposures at work, and epidemiological studies on their effects on human health and well-being. A key question we apply to submission is, "Is this paper going to help readers better understand, quantify, and control conditions at work that adversely or positively affect health and well-being?" We are interested in high quality scientific research addressing: the quantification of work exposures, including chemical, biological, physical, biomechanical, and psychosocial, and the elements of work organization giving rise to such exposures; the relationship between these exposures and the acute and chronic health consequences for those exposed and their families and communities; populations at special risk of work-related exposures including women, under-represented minorities, immigrants, and other vulnerable groups such as temporary, contingent and informal sector workers; the effectiveness of interventions addressing exposure and risk including production technologies, work process engineering, and personal protective systems; policies and management approaches to reduce risk and improve health and well-being among workers, their families or communities; methodologies and mechanisms that underlie the quantification and/or control of exposure and risk. There is heavy pressure on space in the journal, and the above interests mean that we do not usually publish papers that simply report local conditions without generalizable results. We are also unlikely to publish reports on human health and well-being without information on the work exposure characteristics giving rise to the effects. We particularly welcome contributions from scientists based in, or addressing conditions in, developing economies that fall within the above scope.
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