Monitoring the liberation of volatile organic compounds during fused deposition modeling three dimensional printing using solid-phase microextraction coupled to gas chromatography/mass spectrometry

Review of volatile organic compound (VOC) emissions from desktop 3D printers and associated health implications

BACKGROUND

Three-dimensional (3D) printing is a technique by which materials are continually added in layers to form structures. The technique has grown in popularity over the past decade and affordable desktop 3D printers are now widely used in schools, universities, businesses, and hospitals.

OBJECTIVE

Understanding the types of chemical emissions from these 3D printers and their potential health effects is essential to safely use this technology.

METHODS

A scoping literature review on volatile organic compound (VOC) emissions from resin-bed and filament 3D printers has been conducted. Most of the published research has focused on emissions from filament 3D printers.

RESULTS

VOC emissions from resin 3D printers have been reported mostly as carbonyl compounds or methacrylate monomers. Filament VOC emissions are more varied in composition reflecting the constituents in the filaments used in this printer. The published research reported that the airborne concentrations of specific VOCs from 3D desktop printers fell below the HSE British workplace exposure limits (WELs). This may suggest that VOC emissions from these printers do not present a risk to occupational health. However, caution is required in reaching this conclusion because most of these studies quantified specific VOC emissions using methods different to those required by workplace regulatory standards. Other exposure circumstances, such as the effect of total VOC emissions, need to be considered, particularly for vulnerable groups, including individuals with respiratory disease, the elderly, or young children. Variables that could increase exposure and risks to health include long print times, multiple 3D printers, and poor ventilation. Research on the VOC emissions from resin 3D printers is required using experimental emission chambers.

IMPACT

The research discussed in this review focused on VOC emissions from desktop 3D printers and the potential health impacts associated with exposure to these compounds. The review identifies circumstances when people may be exposed to 3D printer emissions for which no regulatory exposure limits apply. This circumstance is especially relevant to people working in small businesses and organisations and to vulnerable people, such as the young, elderly and those with pre-existing lung disease. Raising awareness of these potential health concerns from 3D printer emissions can help to inform actions to mitigate exposure, through policy and behavioural changes, as well as engineering control measures. To our knowledge, this is the first review discussing studies of VOC emission from resin and popular filament 3D printers, including exposure risks and health outcomes.

Emission Characteristics of Volatile Organic Compounds from Material Extrusion Printers Using Acrylonitrile-Butadiene-Styrene and Polylactic Acid Filaments in Printing Environments and Their Toxicological Concerns

The utilization of 3D printing releases a multitude of harmful gas pollutants, posing potential health risks to operators. Materials extrusion (ME; also known as fused deposition modeling (FDM)), a widely adopted 3D printing technology, predominantly employs acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA) as printing materials, with the respective market shares of these materials reaching approximately 75%. The extensive usage of ABS and PLA during the ME process leads to significant volatile organic compound (VOC) emissions, thereby deteriorating the quality of indoor air. Nevertheless, information regarding the emission characteristics of VOCs and their influencing factors, as well as the toxicological impacts of the printing processes, remains largely unknown. Herein, we thoroughly reviewed the emission characteristics of VOCs released during ME printing processes using ABS and PLA in various printing environments, such as chambers, laboratories, and workplaces, as well as their potential influencing factors under different environmental conditions. A total of 62 VOC substances were identified in chamber studies using ABS and PLA filaments; for example, styrene had an emission rate of 0.29-113.10 μg/min, and isopropyl alcohol had an emission rate of 3.55-56.53 μg/min. Emission rates vary depending on the composition of the filament's raw materials, additives (such as dyes and stabilizers), printing conditions (temperature), the printer's condition (whether it has closure), and other factors. Additionally, we reviewed the toxicological concerns associated with hazardous VOC species commonly detected during the ME printing process and estimated cancer and non-cancer risks for users after long-term inhalation exposure. Potential health hazards associated with inhalation exposure to benzene, formaldehyde, acetaldehyde, styrene, and other substances were identified, which were calculated based on concentrations measured in real indoor environments. This study provides valuable insights for future research on the development of ME printing technologies and offers suggestions to reduce VOC emissions to protect users.

Microextraction-Driven Optical Fiber Sensor Coupled with Signal Enhancement by Gold Nanostars for Detection of Antibiotics in Food and Water

In this work, a portable optical fiber-based "microextraction sensing" platform coupled with gold nanostars (Au NSRs) was designed for the detection of kanamycin (Kana). Replaceable optical fibers were used as solid-phase microextraction (SPME) devices and sensing probes. Au NSRs and Kana aptamers were sequentially modified onto a fiber core as sensing elements. The evanescent wave generated from the fiber interacted with the surface of the Au NSR, and the localized surface plasmon resonance (LSPR) effect was triggered. In the presence of Kana, the refractive index of the Au NSR surface changed, causing the LSPR characteristic peak to shift, thereby enabling the quantitative detection of Kana. Benefiting from the strong "hot spot" effect produced by the sharp branches of the Au NSR, the intensity of the signals was greatly increased. Under optimal conditions, the sensing platform exhibited high selectivity toward Kana. The calibration linear range was 0.5-500 nM (r2 = 0.997), and a limit of detection of 0.138 nM was achieved. The optical fiber could be easily disassembled and reused. Signal stability remained intact even after a replaceable optical fiber probe was cleaned and used 10 times. The sensor was successfully applied to the analysis of Kana residues in genuine cow's milk samples. The procedure was also applied to river water samples. This assay has unique advantages of low cost, simplicity, and recyclability, making it a promising approach for food analysis and environmental monitoring.

Single-Particle ICP-TOFMS Analysis of Aerosol Particulate Matter Released by Fused Deposition Modeling 3D Printers

Additive manufacturing or 3D printing is rapidly growing in popularity. This growth brings increased interest in studying the byproducts released during 3D printing. In this work, we present a new method to collect and analyze the metal composition of individual particles released during the operation of fused deposition modeling (FDM) 3D printers using single-particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS). The presented method uses a positive-pressure sampling chamber and membrane filters to collect the emitted particles. Particles are then extracted into water, and suspensions are analyzed by spICP-TOFMS. We study common filaments used for fused deposition modeling, including acylonitrile butadiene styrene (ABS) and polylactic acid (PLA), and a specialty filament with stainless-steel particles embedded into the polymer. Using our sampling and extraction procedure, we measured over 1000 particles for each filament type. Critical masses for our measurements are as low as 0.03 fg. The most common measurable metals in the FDM-generated particles are Al, Ti, Fe, and Zr. Single-metal Fe particles make up over 50% of the thermoplastic particle population. We also identify multimetal associations in particles unique to each thermoplastic filament type. Using a stainless-steel-embedded polymer, we measure FeCr particles that are characteristic of the filament composition, with Fe:Cr mass ratios ranging from 4.4 to 3.6. Based on these particle compositions, we demonstrate that metal stainless-steel aerosols are released during the printing of the particle-embedded filament.

Extraction of volatile organic compounds liberated upon filament extrusion by 3D pen and its comparison with a desktop 3D printer using solid-phase microextraction fiber and Arrow

Desktop 3D printers that operate by the fused deposition modeling (FDM) mechanism are known to release numerous hazardous volatile organic compounds (VOCs) during printing, including some with potential carcinogenic effects. Operating in a similar manner to FDM 3D printers, 3D pens have gained popularity recently from their ability to allow users to effortlessly draw in the air or create various 3D printed shapes while handling the device like a pen. In contrast to numerous modern 3D printers, 3D pens lack their own ventilation systems and are often used in settings with minimum airflow. Their operation makes users more vulnerable to VOC emissions, as the released VOCs are likely to be in the breathing zone. Consequently, monitoring VOCs released during the use of 3D pens is crucial. In this study, VOCs liberated while extruding acrylonitrile butadiene styrene (ABS) filaments from a 3D pen were measured by solid-phase microextraction (SPME) combined with gas chromatography/mass spectrometry (GC/MS). SPME was investigated using the traditional fiber and Arrow geometries with the DVB/Carbon WR/PDMS sorbent while four different brands of ABS filaments-Amazon Basics, Gizmodork, Mynt 3D, and Novamaker-were used with the 3D pen. Heatmap analysis showed differentiation among these brands based on the liberated VOCs. The nozzle temperature and printing speed were found to affect the number and amount of released VOCs. This study goes a step further and presents for the first time a comparison between 3D pen and a desktop 3D printer based on liberated VOCs. Interestingly, the findings reveal that the 3D pen releases a greater number and amount of VOCs compared to the printer. The amounts of liberated VOCs, as indicated by the corresponding chromatographic peak areas, were found to be 1.4 to 62.6 times higher for the 3D pen compared to the 3D printer when using SPME Arrow.