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Risk of exposure to harmful substances released during FDM 3D printing

 

Introduction

Protection from emissions from desktop 3D printers is a topic which has not received an appropriate amount of attention given the recent surge in popularity of these devices. Although acknowledged that there is some risk, detailed information is not readily available. This report presents the most up to date information from published peer-reviewed studies and guidance from recognised bodies. A proportional safety response will be recommended.

Literature review

A 2013 study by Stevens et.al [1] measured ultra-fine particles (UFPs) emitted from a commercially available 3D printer operating with both PLA and ABS. The study, conducted in a 45m3 furnished and conditioned office space, confirmed the production of UFPs during the printing process. Printing with PLA produced 1-4 times the background levels of UFPs while printing with ABS produced 9 to 56 times background (across the size range 11.5 nm to 116nm).

This paper [1] also discussed the negative health effects of UFPs on the human body and cites several published papers to support the discussion. Therefore, this information will not be presented again here. Instead, that UFPs have negative health effects will be considered as established. However, it is worth mentioning that these effects include total and cardiorespiratory mortality, hospital admissions for stroke and asthma symptoms.

A separate study published in 2015 [2] , using in a 1 x 1 x 1m test chamber, two different models of printer and three different filaments, analysed emitted particle numbers and size distribution more accurately. Table 1 shows the concentration of particles emitted during printing. Printing with ABS produced a concentration of nano-sized particles many times higher than the concentration produced by printing with PLA. The large difference between printing with ABS and PLA is better visualised by the real time monitoring chart shown in Figure 1.

Material Measured concentration of particles emitted before printing ea/cm3 Measured concentration of particles emitted during printing ea/cm3 Measured concentration of particles emitted during printing as a multiple of concentration of particles before printing Count Median Diameter of particles /nm
PLA1 1997 52 252 26 28
PLA2 2174 45 690 21 188
ABS 5021 1 731 578 345 33

Table 1 – Comparison of emitted particle concentration before and during printing with ABS and two types of PLA material [2]

figure201_zps3hb5fczi

Figure 1 – Real time monitoring during 3D printing with the use of ABS, PLA1 and PLA2 (particle size ranged from 10 to 420 nm) [2]

The latest study conducted on nanoparticle emissions from 3D printers was published in 2016 [3] and is the most comprehensive yet. Five different printer models and sixteen different filaments were used. As reported in the previous work, ABS filament produced substantially more UPFs across all models of printer than PLA (Figure 2).

figure202_zpsmtxnx4pi

Figure 2 Summary of time-varying UFP emission rates estimated for 16 3D printer and filament combinations. Each data point represents data from 1 min intervals, and the combination of data points represents the entire printing period (typically between 2.5 and 4 h). Boxes show the 25th and 75th percentile values with the 50th percentile (median) in between. Whiskers represent upper and lower adjacent values, and circles represent outliers beyond those values. [3]

VOCs produced also depends on the filament type. PLA filaments produced the least VOCs and those consisted predominantly of lactide at a rate of about 4 to 5µg/min. ABS filaments produced between 3 and 20 times the total mass of VOCs (12-113µ/min and this consisted mainly of styrene. Nylon, PCTPE (Plasticised Copolyamide Thermoplastic Elastomer), Laybrick and Laywood filaments produced predominantly caprolactam as high as 180µg/min. See (Figure 3).

figure203_zps3bvvmptl

Figure 3 – Estimates of emission rates for the top three highest-concentration VOCs as well as sum of the top 10 detectable VOCs (ΣVOC) resulting from operation of 16 3D printer and filament combinations. The figure is divided into (a) low emitters, with EΣVOC < 40 μg/min, and (b) high emitters, with EΣVOC > 40 μg/min, for visual clarity. Note that although no error bars are shown in the figure, we estimate the uncertainty in each individual VOC emission rate to be ∼36% [3]

These production rates were used to estimate chemical concentration in a 45m3 furnished and conditioned office space with typical ventilation containing one 3D printer. These concentrations can then be compared with published workplace exposure limits (Table 2).  When doing this only caprolactam comes close to being of any concern measuring in at approximately 25% of the limit.

 

Exposure estimate/µgm-3 NIOSH exposure limit /µgm-3 HSE exposure limit/µgm-3
caprolactam 244 1000 [4] 1000 [5]
styrene 150 215000 [6] 430000 [5]
lactide 6 Unregulated* Unregulated*

Table 2 – Comparison of estimated concentrations against published long term exposure limits.

Ultimaker sell some very popular models of 3D printer and provides information on health risk from using them. In the manual for the Ultimatker 2 Extended [7], Ultimaker recognises that printing with ABS is more risky than printing with PLA. The manual advises that styrene can be released during printing with ABS and recommends that long term exposure is avoided. Use of a fume hood is recommended during use and is considered mandatory for use in offices or classrooms. Unfortunately this information is not prominent being located on page 32 near the end of the manual (Figure 4).

figure204_zpsjs3zgoxw

Figure 4 – Snapshot taken from Ultimaker 2 Extended Manual [7] showing health recommendation on page 32.

Makerbot, another mainstream manufacturer has recently updated its website to highlight the fact that their latest generation of printer only use PLA which it considers to be safe. This webpage [8] references the latest paper by Azimi et.al. [3] as the basis for its stance on safety. The manual for the Makerbot Replicator [9], a current model, places safety information in a more prominent place at the start of the manual on page 8 in the ‘Getting Started’ section and requires that the printer is set up in a well ventilated area (Figure 5).

figure205_zpspbtyy5dz

Figure 5 – Snapshot taken from Makerbot Replicator manual [9]showing health recommendation on page 8.

 

Risk Evaluation

Examination of the existing work done on assessing the health risk from 3D printing identifies two key sources of risk:

  • Risk from exposure to Ultra Fine Particles, and
  • Risk from exposure to harmful substances emitted during printing.

Ultra Fine Particles

Investigations into the risk to health posed by ultrafine particles is a relatively new area of study prompted by the relatively new field of nanotechnology. Evidence exists that exposure to UFPs of nano-particle dimensions can result in adverse health effects [10]. Even if the evidence available is not conclusive, the possible adverse outcomes are such that there is an ethical obligation to protect users.

The emission of UFPs has been confirmed by all of the published papers reviewed. In addition, all of the papers recognise that printing using ABS presents a much greater risk to nearby persons than printing with PLA. It is therefore advised that measures be taken to reduce the exposure to these particles to as low as is reasonably practicable.

Risks from exposure to harmful substances emitted during printing.

The papers reviewed for this report have all detected some level of harmful substance emission during 3D printing. However, the concentrations detected are so low that they fall far below any recommended exposure limit. Measures solely to reduce exposure to these substances is therefore deemed not to be required.

Recommendations

  1. PLA will be the approved material for 3D printing in the department. Use of ABS will only be approved where it is shown that the properties of ABS is specifically required in the finished item
  2. Where ABS is used, local exhaust ventilation or a self-contained air filtration system must be provided. Locating the printer in a fume cabinet which extracts to the outside will be sufficient.
  3. Use of any other material will need to be justified, require approval and a risk assessment.

 

 

References

[1] B. Stevens, P. Azimi, Z. El Orch and T. Ramos, “Ultrafine Particle Emissions from Desktop 3D Printers,” Atmospheric Environment, vol. 79, pp. 334-339, 2013.
[2] K. Yuna, Y. Chungsik, P. Jihoon, K. Songha, K. Ohhun and T. Perng-Jy, Environmental Science and Technology, vol. 49, pp. 12044-12053, 2015.
[3] P. Azimi, D. Zhao, C. Pouzet, N. Crain and B. Stephens, “Emissions of Ultrafine Particles and Volatile Organic Compounds from Commercially Available Desktop Three-Dimensional Printers with Multiple Filaments,” Environmental Science and Technology, vol. 50, pp. 1260-1268, 2016.
[4] The National Institute for Occupational Safety and Health (NIOSH), “NIOSH Pocket Guide to Chemical Hazards,” 11 April 2016. [Online]. Available: http://www.cdc.gov/niosh/npg/npgd0097.html.
[5] Health and Safety Executive, EH40/2005, London: HSE Books, 2011.
[6] National Institute for Occupational Safety and Health, “NIOSH Pocket Guide to Chemical Hazards,” 04 April 2011. [Online]. Available: http://www.cdc.gov/niosh/npg/npgd0571.html. [Accessed 11 April 2016].
[7] Ultimaker, “Ultimaker 2 Extended User Manual V2.1,” 2016.
[8] Makerbot Industries LLC, “Safe and Sound: MakerBot PLA Filament,” Makerbot Industries LLC, 03 February 2016. [Online]. Available: http://www.makerbot.com/blog/2016/02/03/safe-and-sound-makerbot-pla-filament. [Accessed 21 April 2016].
[9] Makerbot Industries LLC, “Makerbot Replicator Desktop 3D Printer User manual Version 2,” Makerbot Industries LLC, 2016.
[10] HEI Review Panel on Ultrafine Particles, “Understanding the Health Effects of Ambient Ultrafine Particles,” HEI, Boston, MA, 2013.
[11] M. R. Gwinn and V. Vallyathan, “Nanoparticles: Health Effects Pros and Cons,” Environmental Health Perspectives, vol. 114, pp. 1818-1825, 2006.

 

 

 

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This entry was posted on 13 May, 2016 by in Technology and tagged , , , , , , , .

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