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Ultrafine particle emissions from desktop 3D printers


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The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that has been shown to have significant aerosol emissions in industrial environments. However, we are not aware of any data on particle emissions from commercially available desktop 3D printers. Therefore, we report on measurements of size-resolved and total ultrafine particle (UFP) concentrations resulting from the operation of two types of commercially available desktop 3D printers inside a commercial office space. We also estimate size-resolved (11.5 nm-116 nm) and total UFP (<100 nm) emission rates and compare them to emission rates from other desktop devices and indoor activities known to emit fine and ultrafine particles. Estimates of emission rates of total UFPs were large, ranging from ˜2.0 × 1010 # min-1 for a 3D printer utilizing a polylactic acid (PLA) feedstock to ˜1.9 × 1011 # min-1 for the same type of 3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. Because most of these devices are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results herein suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments. Additionally, these results suggest that more controlled experiments should be conducted to more fundamentally evaluate particle emissions from a wider arrange of desktop 3D printers.
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Technical note
Ultrane particle emissions from desktop 3D printers
Brent Stephens
, Parham Azimi
, Zeineb El Orch
, Tiffanie Ramos
Department of Civil, Architectural and Environmental Engineering, Illinois Institute of Technology, Chicago, IL, USA
National Institute of Applied Sciences (INSA de Lyon), Lyon, France
article info
Article history:
Received 22 April 2013
Received in revised form
24 June 2013
Accepted 26 June 2013
Indoor aerosols
Three-dimensional printers
Thermoplastic emission
Molten extrusion deposition
The development of low-cost desktop versions of three-dimensional (3D) printers has made these de-
vices widely accessible for rapid prototyping and small-scale manufacturing in home and ofce settings.
Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that
has been shown to have signicant aerosol emissions in industrial environments. However, we are not
aware of any data on particle emissions from commercially available desktop 3D printers. Therefore, we
report on measurements of size-resolved and total ultrane particle (UFP) concentrations resulting from
the operation of two types of commercially available desktop 3D printers inside a commercial ofce
space. We also estimate size-resolved (11.5 nme116 nm) and total UFP (<100 nm) emission rates and
compare them to emission rates from other desktop devices and indoor activities known to emit ne and
ultrane particles. Estimates of emission rates of total UFPs were large, ranging from w2.0 10
for a 3D printer utilizing a polylactic acid (PLA) feedstock to w1.9 10
# min
for the same type of
3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock.
Because most of these devices are currently sold as standalone devices without any exhaust ventilation
or ltration accessories, results herein suggest caution should be used when operating in inadequately
ventilated or unltered indoor environments. Additionally, these results suggest that more controlled
experiments should be conducted to more fundamentally evaluate particle emissions from a wider
arrange of desktop 3D printers.
Ó2013 The Authors. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Three-dimensional (3D) printers are gaining popularity as
rapid prototyping and small scale manufacturing devices. The
development of low-cost desktop versions has made this tech-
nology widely accessible for use in home and ofce settings. The
majority of commercially available 3D printers utilize an additive
manufacturing technique known as molten polymer deposition
(MPD), whereby a solid thermoplastic lament is forced through a
computer-driven extrusion nozzle (Bumgarner, 2013). The heated
nozzle melts the thermoplastic feedstock and deposits streams of
extruded plastic in thin layers across a moving baseplate. As the
material hardens and the baseplate moves to the next layer, a
three-dimensional solid shape is rapidly formed.
Several types of thermoplastics are commonly used in a variety
of these commercially available desktop MPD devices. Most
desktop 3D printers currently utilize either acrylonitrile butadiene
styrene (ABS) or polylactic acid (PLA) as a thermoplastic feedstock
(Ragan, 2013). Primary differences between ABS and PLA based
printers are feedstock origin and nozzle and baseplate tempera-
tures during operation. PLA is a biodegradable, corn-based plastic
that prints at nozzle temperatures of w180
C and baseplate
temperatures near room temperature. ABS is a stronger thermo-
plastic that typically prints at w220
C nozzle temperatures and
C baseplate temperatures in most commercially available
devices (Weinhoffer, 2012). Other thermoplastic feedstock sources
include polyvinyl alcohol (PVA), polycarbonate (PC), and high-
density polyethylene (HDPE), although they are not widely used
in commercially available devices (Ragan, 2013).
Previous studies of moderately high temperature (e.g., 170e
C nozzle temperatures) thermal processing of thermoplastics
in large scale industrial extrusion equipment have shown that both
gases and particles are emitted during operation (Contos et al.,
1995; Unwin et al., 2012). Primary gas-phase products of ABS
thermal decomposition at very high temperatures have been
shown to include carbon monoxide and hydrogen cyanide, as well
This is an open-access article distributed under the terms of the Creative
Commons Attribution-NonCommercial-No Derivative Works License, which per-
mits non-commercial use, distribution, and reproduction in any medium, provided
the original author and source are credited.
*Corresponding author.
E-mail address: (B. Stephens).
Contents lists available at SciVerse ScienceDirect
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1352-2310/$ esee front matter Ó2013 The Authors. Published by Elsevier Ltd. All rights reserved.
Atmospheric Environment 79 (2013) 334e339
as a variety of volatile organics (Rutkowski and Levin, 1986).
Exposure to thermal decomposition products from ABS has also
been shown to have toxic effects in both rats (Zitting and
Savolainen, 1980) and mice (Schaper et al., 1994).
Other studies have shown that exposure to fumes from thermal
decomposition of other thermoplastics, such as polytetrauoro-
ethylene (PTFE), is also acutely toxic to mammals, including
humans (Oberdörster et al., 2005 and references therein). More-
over, ultrane particles (UFPs: particles less than 100 nm) may be of
particular importance for toxicity of fumes emitted from melting of
some thermoplastics. For example, in a previous study of high
temperature melting of PTFE at w480
C, UFPs with a count median
diameter of 18 nm were produced, which were also shown to be
highly toxic to rats (Oberdörster et al., 1995). Additional studies
revealed that the gas phase of PTFE fumes alone was not acutely
toxic (Johnston et al., 2000), which suggests that ultrane aerosols
emitted from thermal degradation of thermoplastic materials may
be of concern among emission products generated in these high
temperature applications.
Despite the rapid commercial uptake of desktop 3D printers that
rely on similar moderate or high temperature thermoplastic melting
and extrusion technology, we are not aware of any data on particle
emissions from these commercially available devices. Indoor
emissions from these devices may be particularly important
because they are most often sold as standalone devices without
mechanical ventilation or ltration accessories. Therefore, we
report on the rst measurements of which we are aware of size-
resolved and total UFP concentrations resulting from the opera-
tion of several models of a single type of commercially available
desktop 3D printer utilizing two types of thermoplastic feedstocks
and operating inside a small ofce space. We also estimate indi-
vidual size-resolved and total UFP emission rates and compare them
to other desktop devices and indoor activities known to emit UFPs.
2. Methods
Measurements were conducted in a 45 m
furnished and
conditioned ofce space belonging to a company who specializes in
3D printer education, training, and sales for the general public. Nine
3D printers were installed on tables in this particular space; only
ve adjacent printers were used in this study. Particle number
concentrations were measured in the closed room using a TSI
NanoScan SMPS Model 3910 logging at 1-min intervals. The SMPS
utilizes an isopropanol-based CPC and a radial DMA for size reso-
lution across 13 bins from 10 to 420 nm. It was placed on a table
inside the closed room approximately 2 m away from the nearest
printer. The door remained closed during the testing procedure
except during periods when printers were reset.
We were granted access to the ofce space only for a limited
time and thus relied on an ad hoc experimental design consisting of
four distinct operational periods over a period of approximately
2.5 h: (1) background measurements without printers operating for
approximately 25 min; (2) two identical 3D printers using PLA
thermoplastic feedstocks operating for approximately 20 min to
print small plastic gures (followed by a short decay period while
the next printing period was setup); (3) the same two PLA-based
printers operating simultaneously with three of the same make
and model printers operating with higher temperature ABS feed-
stocks for approximately 20 min to print another set of small plastic
gures; and (4) a concentration decay period lasting approximately
40 min. The measured concentration data were used to solve for
size-resolved and total UFP emission rates using a combination of
methods from the various monitoring periods, as described below.
Increases in particle concentrations during either printer oper-
ation period were observed only for particles smaller than the
150 nm bin; therefore we only use data from the rst nine particle
size bins (11.5 nme116 nm) in this work. In addition to size-
resolved measurements, we also describe total UFPs as the sum
of the rst eight particle size bins smaller than 100 nm, per existing
nomenclature in the eld (Oberdörster et al., 2005). The room was
assumed to be well-mixed for all periods, which should be
reasonable for a small room with several high temperature devices
operating over a 2.5 h time period (Baughman et al., 1994; Klepeis,
1999), although we cannot conrm this assumption. However,
similar approaches for estimating emission rates from even larger
spaces have been used successfully in previous studies (Wallace
et al., 2004; Buonanno et al., 2009).
2.1. Period 1: background measurements
Upon arrival to the room the printers had not been operating
since the previous day. Particle concentrations were rst measured
inside the room during this time for a period of w25 min. Because
the resulting concentrations were stable, data from this period was
used as the representative steady-state background concentration
for each particle size, including total UFPs (i.e., the sum of all par-
ticle concentrations less than 100 nm). The background concen-
tration is a function of the fundamental parameters described in
Equation (1), although only concentrations were directly measured.
where C
is the mean baseline size-resolved (or total UFP)
indoor particle concentration (# cm
); C
is the size-resolved
outdoor particle concentration (# cm
, not measured in this
study); L
is the size-resolved total loss rate in the room due to the
combined effects of air exchange with outside the room, deposi-
tion to surfaces, and removal by any operating HVAC system and
lter (min
); P
is the room penetration factor (dimensionless, not
measured); and
is the air exchange rate in the room (# min
not measured). Because of the short access window for the eld
measurements and limited instrument availability, we were not
able to measure the air exchange rate in the ofce space. However,
the total loss rate L
was estimated from the decay period in this
study according to a procedure outlined in the description of
Period 4. Total loss rates are then used for estimating emission
rates in both Periods 2 and 3. This same procedure has been used
successfully in other previous studies of indoor UFP emissions
from a variety of devices and appliances (e.g., Wallace et al., 2004;
Buonanno et al., 2009).
2.2. Period 2: two PLA printers operating
During Period 2, two 3D printers were operated simultaneously
to print sample plastic products. Printer operation continued until
the objects were fully printed, which took approximately 20 min.
These identical make and model printers utilized a polylactic acid
(PLA) feedstock and operated at an extruder temperature of 200
and baseplate temperature of 18
C. One printer assembled a small
plastic frog (shown in Fig. 1) and the other assembled a plastic
chain link.
UFP concentrations measured during Period 2 were shown to
reach approximately steady state before the print jobs were com-
plete (see Fig. 2). Therefore, individual emission rates were esti-
mated using steady-state indoor concentrations (C
shown in Equation (2). Emission rates were assumed to be the same
for each PLA printer because they were the same make and model,
although we were not able to test the validity of this assumption.
B. Stephens et al. / Atmospheric Environment 79 (2013) 334e339 335
where E
is the individual size-resolved (or total) UFP emission
rate from each of the two PLA printers (# min
) and Vis the vol-
ume of the room (cm
). The mean and standard deviation of the
background concentrations from Period 1 were used in conjunction
with steady-state data from Period 2 and estimates of L
from Period
4 to solve for E
. The procedure was performed using data from
each of the nine particle size bins (11.5e116 nm), as well as for the
total UFP number concentrations (the sum of all eight UFP bins).
Uncertainty in E
was estimated as the relative standard de-
viations from the means for both C
and C
added in
quadrature with the relative uncertainty in L
. Period 2 ended when
the 3D printers nished printing the models; subsequently there
was a short decay period while we prepared additional printers for
Period 3 tasks.
2.3. Period 3: two PLA printers and three ABS printers operating
During Period 3, the same two printers from Period 2 utilizing
PLA feedstocks were operated again along with three additional
printers of the same make and model. However, the three addi-
tional printers utilized an ABS feedstock and operated at higher
extruder and baseplate temperatures of 220
C and 118
respectively. Each printer assembled another small plastic frog,
with the exception of one of the PLA printers that again assembled a
small chain link. Because of the time-varying nature of the data
measured during this period, emission rates were estimated using
the analytical solution to a dynamic mass balance on the space, as
shown in Equation (3).
A two-parameter nonlinear least squares regression (Stata
Version 11) was performed to estimate the size-resolved (and total)
UFP emission rates from the combination of all ve printers during
this period, where E
/V. Both the initial
concentration (C
) and the total emission rates (E
treated as unknowns for each particle size (and total UFPs) in the
regression analysis. The same values of L
from Period 4 decay data
(which were also used in Period 2) were used in conjunction with
mean values of C
from Period 1. Uncertainty in emission rates
was estimated as the relative standard error of the regression co-
efcients for both E
and L
added in quadrature with the rela-
tive standard deviation in C
from Period 1. Size-resolved UFP
emission rates for the two PLA printers (E
) were assumed to be
the same as in Period 2 and size-resolved UFP emission rates for
each of the three ABS printers (E
) were also assumed to be
equal. As a check on our emission rate estimates, we also estimated
size-resolved and total UFP emission rates assuming there were no
losses during this brief period of high emissions (where
t). This served to provide a reasonable lower bound
of emission rates for the printers. This procedure for solving for
emission rates neglects any particle coagulation or growth by
condensation, which may introduce some additional uncertainty in
our estimates of size-resolved emission rates. However, emission
rates of total UFPs based on this approach are not affected by
coagulation or condensation growth, as these mechanisms only
impact individual bins within the total UFP range. Other recent
studies have also used a similar methodology neglecting coagula-
tion or condensation, as source strengths are often large enough to
overwhelm other impacts within a short period of testing (e.g.,
Wallace et al., 2004; Afshari et al., 2005; He et al., 2007).
Number concentration (# cm
0 30 60 90 120 150
11. 5 n m
15.4 nm
20.5 nm
27.4 nm
36.5 nm
48.7 nm
64.9 nm
86.6 nm
116 n m
Printers off
Total UFPs
11. 5 n m
15.4 nm
20.5 nm
27.4 nm
36.5 nm
48.7 nm
64.9 nm
86.6 nm
116 n m
Background 2PLA
Fig. 2. Size-resolved and total (<100 nm) ultrane particle (UFP) concentrations measured in the ofce space during the sampling campaign.
Fig. 1. Example of a three-dimensionally printed frog in this study.
B. Stephens et al. / Atmospheric Environment 79 (2013) 334e339336
2.4. Period 4: printers off (decay)
Finally, during Period 4, all printers were turned off and indoor
concentrations decayed back toward normal background levels.
Total loss rates (L
) were estimated for each particle size and for
total UFPs using the time-varying data that t a straight line on a
log-linear plot, as shown in Equation (4).
ln C
i;in;ss bg
i;in ss bg
Estimating loss rates in this manner provides lumped loss rates
that account for the combined effects of air exchange, deposition to
indoor surfaces, and removal by any HVAC ltration. Unfortunately
due to both equipment and access limitations, relative contribu-
tions of each of these were not directly measured. However, pre-
vious studies have shown this lumped approach to be valid for
estimating emission rates (Wallace et al., 2004; Buonanno et al.,
2009). Total particle loss rates were assumed to be constant dur-
ing the relatively short eld-testing period of 2.5 h for use in solving
for emission rates from the previous periods.
3. Results
Fig. 2 shows resulting time-resolved UFP concentrations
measured in the ofce space throughout the sampling campaign.
The bottom portion shows size-resolved number concentrations
for the 11.5 nme116 nm particle size bins (as previously
mentioned, no elevations in particle concentrations were observed
in particle bins larger than 116 nm and thus are not shown for
graphical clarity). The top portion of Fig. 2 also shows total UFP
concentrations summed across the rst 8 particle size bins smaller
than 100 nm.
The operation of the two printers utilizing PLA as a feedstock
increased concentrations primarily for particles larger than 20 nm.
Indoor concentrations during PLA printer operation also reached
approximately steady-state conditions for a period of w15 min.
Subsequently, the operation of the two PLA printers in conjunction
with three of the same make and model printers (albeit utilizing a
higher temperature ABS feedstock) resulted in substantial increases
in all UFP sizes. Table 1 summarizes mean (s.d.) size-resolved and
total UFP concentrations measured during both background (Period
1) and steady-state operation of two PLA-based printers (Period 2),
along with peak concentrations from the operation of all ve 3D
printers (Period 3). Only peak concentrations are shown for each
particle size for Period 3 measurements because steady-state
conditions were not achieved before the printers nished their
print jobs. Table 1 also summarizes loss rates and associated un-
certainty estimated from Period 4 data. Regression coefcients
showed good correlation between measured and modeled con-
centrations during the decay period for most particle sizes (except
for the smallest and largest size bins).
Mean size-resolved particle concentrations during the opera-
tion of the two printers utilizing PLA feedstock were a factor of
w1e4 times higher than during background periods, depending on
particle size. Total UFP concentrations were almost three times
higher (w27,800 cm
vs. w9700 cm
). The largest increases were
observed in the 36e86 nm size ranges. During operation of the
same two PLA printers combined with three additional printers
utilizing ABS feedstocks, size-resolved particle concentrations
rapidly elevated to as high as 9e56 times background and 3.6e31
times that with only two PLA-based printers operating, depending
on particle size. Peak total UFP concentrations with all ve printers
operating (w142,200 cm
) were ve times higher than with only
two PLA-based printers operating and nearly 15 times higher than
background conditions.
Lumped loss rates estimated from all of the Period 4 decay data
ranged from w2.5 h
to w5.6 h
. Total UFP loss rates were
approximately 3 h
. The largest uncertainty in loss rates was
associated with the largest and smallest particle size bins, likely
due to relatively low peak concentrations from which decay
occurred. Although the relative contributions of air exchange,
deposition to surfaces, and control by any HVAC ltration are not
known, they are not necessary to solve for emission rates herein
(Wallace et al., 2004; Buonanno et al., 2009).
Fig. 3 shows size-resolved and total UFP emission rates and
associated uncertainty for individual 3D printers estimated from the
measured concentration data following the methodology described
in Section 2. The higher temperature ABS-based printers had total
UFP emission rates nearly an order of magnitude higher than the
lower temperature PLA-based printers (1.8e2.0 10
# min
compared to 1.9e2.0 10
# min
). Peak emission rates from the
PLA-based printers occurred in the 48e65 nm size range while peak
emission rates from the higher temperature ABS-based printers
occurred in a smaller size range (w15e49 nm). Table 2 describes the
same central estimates of UFP emission rates from Fig. 3 along with
ranges of uncertainty estimated for each size bin. Additionally,
minimum estimates of emission rates made by ignoring particle
losses were 30e51% lower than our central estimates; for example,
the minimum estimate for the total UFP emission rate from a single
ABS printer was 9.7 10
# min
compared to 1.9 10
# min
for our best estimate. Therefore, even if there is additional uncer-
tainty in our estimates of emission rates, the ABS printers still have a
total UFP emission rate on the order of 10
# min
Several recent studies have also reported size-resolved and/or
total UFP emission rates from a variety of other consumer devices,
appliances, and activities such as laser printers, candles, cigarettes,
irons, radiators, and cooking on gas and electric stoves (e.g.,
Dennekamp, 2001; Wallace et al., 2004, 2008; Afshari et al., 2005;
Buonanno et al., 2009; He et al., 2010). Unfortunately, it is not
straightforward to compare our results directly to results from
many of these studies because they have varied in both their
minimum and maximum measured particle sizes, as well as in their
denition of UFPs. However, Buonanno et al. (2009) reported total
UFP emission rates over the same size range as ours measured
during various cooking activities. For comparison, our estimate of
the total UFP emission rate for a single PLA-based 3D printer (1.9e
2.0 10
# min
) was similar to that reported during cooking
with an electric frying pan (1.1e2.7 10
# min
). The same 3D
printer utilizing a higher temperature ABS feedstock had an emis-
sion rate estimate (1.8e2.0 10
# min
) similar to that reported
during grilling food on gas or electric stoves at low power (1.2e
Table 1
Summary statistics for each test period.
Period 1 Period 2 Period 3 Period 4
(# cm
(# cm
i,in,2PLA þ3ABS
(# cm
Mean (s.d.) Mean (s.d.) Peak
11.5 nm 158 (25) 495 (33) 8977 4.01 0.20 0.91
15.4 nm 544 (27) 557 (33) 17,438 5.65 0.08 0.99
20.5 nm 975 (25) 1085 (63) 14,356 4.19 0.06 0.99
27.4 nm 1779 (64) 3712 (99) 22,475 2.89 0.05 0.99
36.5 nm 2025 (76) 5976 (164) 27,185 2.58 0.05 0.98
48.7 nm 1793 (76) 6671 (229) 25,473 2.54 0.06 0.98
64.9 nm 1372 (66) 5649 (218) 20,265 2.54 0.06 0.98
86.6 nm 1038 (45) 3695 (161) 13,479 3.09 0.09 0.97
116 nm 695 (58) 1575 (137) 142,211 4.42 0.35 0.80
UFP 9684 (248) 27,838 (658) 6345 2.97 0.04 0.99
B. Stephens et al. / Atmospheric Environment 79 (2013) 334e339 337
2.9 10
# min
), but approximately an order of magnitude
lower than gas or electric stoves operating at high power (1.2e
3.4 10
# min
). Regardless, the desktop 3D printers measured
herein can all be classied as high emitterswith UFP emission
rates greater than 10
particles per min, according to criteria set
forth in He et al. (2007).
4. Discussion
UFPs are particularly relevant from a health perspective because
they deposit efciently in both the pulmonary and alveolar regions
of the lung (Hinds, 1999; Chalupa et al., 2004), as well as in head
airways. Deposition in head airways can also lead to translocation
to the brain via the olfactory nerve (Oberdörster et al., 2004). The
high surface areas associated with UFPs also lead to high concen-
trations of other adsorbed or condensed compounds (Delno et al.,
2005; Sioutas et al., 2005). Several recent epidemiological studies
have shown that elevated UFP number concentrations are associ-
ated with adverse health effects, including total and cardio-
respiratory mortality (Stölzel et al., 2007), hospital admissions for
stroke (Andersen et al., 2010), and asthma symptoms (Peters et al.,
1997; Penttinen et al., 2001; Von Klot et al., 2002). Therefore, re-
sults herein suggest that caution should be used when operating
these 3D printing instruments inside unvented or unltered indoor
environments due to their large emissions of UFPs.
One important limitation to this study is that we have no in-
formation about the chemical constituents of the UFPs emitted
from either type of 3D printer, although condensation of synthetic
organic vapors from the thermoplastic feedstocks are likely a large
contributor (Morawska et al., 2009). In addition to large differences
in emission rates observed between PLA- and ABS-based 3D
printers, there may also be differences in toxicity because of dif-
ferences in chemical composition. As mentioned, thermal decom-
position products from ABS have been shown to have toxic effects
(Zitting and Savolainen, 1980; Schaper et al., 1994); however, PLA is
known for its biocompatibility and PLA nanoparticles are widely
used in drug delivery (Anderson and Shive, 1997; Hans and
Lowman, 2002).
Another important limitation to this study is that we did not
explicitly account for particle coagulation or growth by condensa-
tion in our methodology for estimating emission rates. Coagulation
has been shown to be a factor in indoor environments primarily
during the rst few minutes of high concentration periods (e.g.,
>20,000 cm
) for particles smaller than 20 nm, and particularly
for those smaller than 10 nm (Wallace et al., 2008; Rim et al., 2012).
Fig. 2 shows that there may have been some additional losses from
the smallest size bin due to coagulation and/or condensation
growth, as peak concentrations lagged other sizes by 3e5 min.
However, it is not clear whether this is due to particle growth or
mixing issues or, alternatively, that the difference is meaningful.
Because we could not conduct controlled experiments in the test
space with limited access, this potential evolution is difcult to
evaluate precisely and is not explicitly accounted for herein, which
may introduce some additional uncertainty in our estimates of size-
resolved emission rates. However, emission rates of total UFPs
based on the lumped loss rate approach are not affected by coag-
ulation or condensation growth, as these mechanisms only impact
individual bins within the total UFP range and no emissions were
observed for particles greater than the 116 nm size bin. Regardless,
particle growth and/or coagulation should be explored in more
controlled environments in future studies.
5. Conclusions
In this work, we present some of the rst known measurements
of which we are aware of UFP emissions from commercially avail-
able desktop 3D printers. Emission rates of total UFPs were
approximately an order of magnitude higher for 3D printers uti-
lizing an ABS thermoplastic feedstock relative to a PLA feedstock:
w1.9 10
# min
compared to w2.0 10
# min
. However,
Table 2
Estimates of emission rates from individual 3D printers utilizing different thermo-
plastic feedstocks.
size bin
UFP emission rates per printer (# min
PLA (Period 2) ABS (Period 3)
Range Central
11.5 nm 5.8 10
[4.7e6.8] 10
1.4 10
[1.1e1.7] 10
15.4 nm 2.8 10
[2.6e3.0] 10
3.2 10
[2.8e3.6] 10
20.5 nm 1.7 10
[1.6e1.8] 10
2.5 10
[2.2e2.7] 10
27.4 nm 2.4 10
[2.2e2.5] 10
3.0 10
[2.8e3.3] 10
36.5 nm 3.6 10
[3.4e3.7] 10
3.4 10
[3.2e3.7] 10
48.7 nm 4.5 10
[4.2e4.7] 10
3.1 10
[2.8e3.3] 10
64.9 nm 4.0 10
[3.8e4.3] 10
2.2 10
[2.0e2.4] 10
86.6 nm 3.0 10
[2.8e3.2] 10
1.5 10
[1.3e1.6] 10
116 nm 1.5 10
[1.2e1.7] 10
6.9 10
[5.4e8.5] 10
Total UFPs
(<100 nm)
2.0 10
[1.9e2.0] 10
1.9 10
[1.8e2.0] 10
Fig. 3. Individual UFP emission rates from 3D printers utilizing two types of thermoplastic feedstocks in this study: (a) size-resolved emission rates (11.5e116 nm) and (b) total UFP
(<100 nm) emission rates.
B. Stephens et al. / Atmospheric Environment 79 (2013) 334e339338
both can be characterized as high emittersof UFPs. These results
suggests caution should be used when operating some commer-
cially available 3D printers in unvented or inadequately ltered
indoor environments. Additionally, more controlled experiments
should be conducted to more fundamentally evaluate aerosol
emissions from a wider range of desktop 3D printers and
The authors thank Robert Zylstra and Julie Friedman Steele from
The Metaspace and The 3D Printer Experience, respectively, for
providing access to the test space.
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Exposure science has developed alongside epidemiology and toxicology as a field that aims to describe qualitatively and, in particular, quantitatively the contact of an individual or a population group with a chemical, physical, and biological stressor. Therefore, this chapter describes the basics of the exposure assessment process, its procedure and helpful sources to find data on human exposure factors like the US EPA Exposure Factors Handbook. Overall, the exposome is understood as the comprehensive—cumulative—description of the lifelong exposure history of individuals to changing exogenous and endogenous influences. In addition, the inclusion of human biomonitoring in exposure assessment and the importance of textiles as a source of indoor air pollution expands our scientific knowledge. Indispensable for understanding the health effects is the behavior of volatile and semi-volatile organic compounds, as well as particulate matter in the lungs. Many exposure and risk assessment strategies take their starting point from the exposure of sedimented dust indoors and its uptake through, e.g., hand-to-mouth contact. Nevertheless, some critical points like sampling conditions, type of analytical method, intake rates, bioaccessibility, and bioavailability have to be taken into account. In addition, special important exposure situations such as the use of printers, open fires indoors, as well as the exposure inside aircraft cabins are presented.
This chapter provides a brief overview of emerging materials that either have the potential to be or have already been identified as problematic for the environment. The growing population, estimated to be \(\approx \)10 billion people by the year 2050, will create asymmetric pressure on available resources, leading to the need for novel materials to drive technological advancement and alleviate the burden on natural resources. Development and implementation of new materials and technologies driven by necessity may exacerbate environmental contamination as these new materials are rushed into use without forethought into their environmental impacts. In this chapter, various aspects of 3D printing, nanocomposites, electronic waste (E-waste), biomaterials, cellulosic materials, volatile organic compounds (VOC), microplastics, and antibiotics have been discussed in terms of their current or potential environmental relevance. For example, Ag- and TiO\(_2\)-nanoparticles (NPs) have potential for antibacterial, and UV protection applications, respectively, and are used in textiles, medical devices, dental fillings, etc. However, these NPs can pose a threat if released into the environment, which may occur through leaching mechanisms or through textile laundering. The annual global E-waste production is projected to increase to 74.7 Mt by the year 2030, thus increasing the potential for environmental contamination unless efficient recovery and remediation technologies are developed. Photovoltaic panels (PVs) are one such example that have emerged as significant E-waste contaminants. These devices have only recently been classified as E-waste by the European Commission, and their volumes are anticipated to increase rapidly. During pyrolysis processes (combustion, biomass conversion, etc.), a significant quantity of VOCs such as benzene, toluene, and phenol are expected to be released and pose both carcinogenic and noncarcinogenic health hazards to the workforce, neighboring general population, and environment. Furthermore, the tracking and detection of increased antibiotic resistance, and accumulation of microplastics leading to organic and metallic pollutants will be highlighted. One major environmental contaminant relevant in today’s society, per- and polyfluoroalkyl substances (PFAS), will not be discussed in this chapter as this topic is discussed in two separate chapters in the book. Material types, pros and cons, and modes of release into the environment will be discussed. The topics reviewed in this chapter will support parallel research on environmental impacts of next-generation materials as new technologies are developed and implemented in society.
Manufacturing advancements in polymer printing now allow for the addition of metal additives to thermoplastic feedstock up to 80-90 % by weight and subsequent printing on low-cost desktop 3D printers. Particles associated with metal additives are not chemically bound to the plastic polymer, meaning these particles can potentially migrate and become bioavailable. This study investigated the degree to which two human exposure pathways, oral (ingestion) and dermal (skin contact), are important exposure pathways for metals (copper, chromium, and tin) from metal-fill thermoplastics used in consumer fused filament fabrication (FFF). We found that dermal exposure to copper and bronze filaments presents the highest exposure risk due to chloride (Cl-) in synthetic sweat driving copper (Cu2+) release and dissolution. Chromium and tin were released as micron-sized particles < 24 μm in diameter with low bioaccessibility during simulated oral and dermal exposure scenarios, with potential to undergo dissolution in the gastrointestinal tract based on testing using synthetic stomach fluids. The rate of metal particle release increased by one to two orders of magnitude when thermoplastics were degraded under 1 year of simulated UV weathering. This calls into question the long-term suitability of biodegradable polymers such as PLA for use in metal-fill thermoplastics if they are designed not to be sintered. The greatest exposure risk appears to be from the raw filaments rather than the printed forms, with the former having higher metal release rates in water and synthetic body fluids for all but one filament type. For brittle feedstock that requires greater handling, as metal-fill thermoplastics can be, practices common in metal powder 3D printing such as wearing gloves and washing hands may adequately reduce metal exposure risks.
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Previous research has indicated that ultrafine particles (UFPs, particles less than 100 nm) emitted from desktop three-dimensional (3D) printers exhibit cytotoxicity. However, only a limited number of particles from different filaments and their combinations have been tested for cytotoxicity. This study quantified the emissions of UFPs from a commercially available filament extrusion desktop 3D printer using three different filaments, including acrylonitrile butadiene Styrene (ABS), thermoplastic polyurethane (TPU), and polyethylene terephthalate glycol (PETG). In this study, controlled experiments were conducted where the particles emitted were used to expose cells grown in an air-liquid interface (ALI) system. The ALI exposures were utilized for in vitro characterization of particle mixtures, including UFPs from a 3D printer. Additionally, a lactate dehydrogenase (LDH) assay was used to evaluate the cytotoxic effects of these UFPs. A549 cells were exposed at the ALI to UFPs generated by an operational 3D printer for an average of 45 and 90 min. Twenty-four hours post-exposure, the cells were analyzed for percent cytotoxicity in a 24-well ALI insert (LDH assay). UFP exposure resulted in diminished cell viability, as evidenced by significantly increased LDH levels. The findings demonstrate that ABS has the most significant particle emission. ABS was the only filament that showed a significant difference compared to the high efficiency particulate arrestance (HEPA) following 90 min of exposure (p-value < 0.05). Both ABS and PETG exhibited a significant difference compared to the HEPA control after 45 min of exposure. A preliminary analysis of potential exposure to these products in a typical environment advises caution when operating multiple printer and filament combinations in poorly ventilated spaces or without combined gas and particle filtration systems.
Acrylonitrile–butadiene–styrene (ABS) polymers are composed of elastomers dispersed as a grafted particulate phase in a thermoplastic matrix of styrene and acrylonitrile (SAN) copolymer. The presence of SAN grafted onto the elastomeric component, usually polybutadiene or a butadiene copolymer, compatabilizes the rubber with the SAN component. The property advantages provided by this graft terpolymer include excellent toughness, good dimensional stability, good processability, and chemical resistance. The system is structurally complex. This allows considerable versatility in the tailoring of properties to meet specific product requirements. Consequently, research and development in ABS systems is active. Numerous grades of ABS are available, including new alloys and specialty grades for high heat, flaming‐retardant, or static dissipative product requirements. Good chemical resistance combined with the relatively low water absorptivity (<1%) results in high resistance to staining agents. Antioxidants substantially improve oxidative stability. Applications involving extended outdoor exposure require the use of stabilizing additives, pigments, and protective coatings. In manufacturing, grafting is achieved by the free‐radical copolymerization of styrene and acrylonitrile monomers. The commercial processes for manufacturing ABS are discussed. ABS can be processed by compression and injection molding, extrusion, calendering, and blow molding. Postprocessing operations include cold forming, painting, and adhesive bonding. ABS is one the two major plastic materials used in 3D printing, an emerging additive‐manufacturing technology that is developing rapidly in the past couple of decades. As a “bridge” polymer between commodity plastics and higher performance engineering thermoplastics, ABS has become the largest selling engineering thermoplastic.
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A fundamental understanding of the in vivo biodegradation phenomenon as well as an appreciation of cellular and tissue responses which determine the biocompatibility of biodegradable PLA and PLGA microspheres are important components in the design and development of biodegradable microspheres containing bioactive agents for therapeutic application. This chapter is a critical review of biodegradation, biocompatibility and tissue/material interactions, and selected examples of PLA and PLGA microsphere controlled release systems. Emphasis is placed on polymer and microsphere characteristics which modulate the degradation behaviour and the foreign body reaction to the microspheres. Selected examples presented in the chapter include microspheres incorporating bone morphogenetic protein (BMP) and leuprorelin acetate as well as applications or interactions with the eye, central nervous system, and lymphoid tissue and their relevance to vaccine development. A subsection on nanoparticles and nanospheres is also included. The chapter emphasizes biodegradation and biocompatibility; bioactive agent release characteristics of various systems have not been included except where significant biodegradation and biocompatibility information have been provided.
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Indoor ultrafine particles (UFP, < 100 nm)undergo aerosol processes such as coagulation and deposition, which alter UFP size distribution and accordingly the level of exposure to UFP of different sizes. This study investigates the decay of indoor UFP originated from five different sources: a gas stove and an electric stove, a candle, a hair dryer, and power tools in a residential test building. An indoor aerosol model was developed to investigate differential effects of coagulation,deposition and ventilation.The coagulation model includes Brownian, van der Waals and viscosity forces, and also fractal geometry for particles > 24 nm. The model was parameterized using different values of the Hamaker constant for predicting the coagulation rate. Deposition was determined for two different conditions: central fan on vs. central fan off. For the case of a central fan running, deposition rates were measured by using a nonlinear solution to the mass balance equation for the whole building. For the central fan off case, an empirical model was used to estimate deposition rates. Ventilation was measured continuously using an automated tracer gas injection and sampling system.The study results show that coagulation isa significantaerosol process forUFP dynamics and the primary cause for the shift of particle size distribution following an episodic high-concentration UFP release with no fans on‥ However, with the central mechanical fan on, UFP deposition loss is substantial and comparable to the coagulation loss. These results suggest that coagulation should be considered during high concentration periods (> 20, 000 cm), while particle deposition should be treated as a major loss mechanism when air recirculates through ductwork or mechanical systems.
The evaluation of emissions of volatile organic compounds (VOCs) during processing of resins is of interest to resin manufacturers and resin processors. An accurate estimate of the VOCs emitted from resin processing has been difficult due to the wide variation in processing facilities. This study was designed to estimate the emissions in terms of mass of emitted VOC per mass of resin processed. A collection and analysis method was developed and validated for the determination of VOCs present in the emissions of thermally processed acrylonitrile butadiene styrene (ABS) resins. Four composite resins were blended from automotive, general molding, pipe, and refrigeration grade ABS resins obtained from the manufacturers. Emission samples were collected in evacuated 6-L Summa canisters and then analyzed using gas chromatography/flame ionization detection/mass selective detection (GC/FID/MSD). Levels were determined for nine target analytes detected in canister samples, and for total VOCs detected by an inline GC/FID. The emissions evolved from the extrusion of each composite resin were expressed in terms of mass of VOCs per mass of processed resin. Styrene was the principal volatile emission from all the composite resins. VOCs analyzed from the pipe resin sample contained the highest level of styrene at 402 μg/g. An additional collection and detection method was used to determine the presence of aerosols in the emissions. This method involved collecting particulates on glass fiber filters, extracting them with solvents, and analyzing them using gas chromatography/mass spectrometry (GC/MS). No significant levels of any of the target analytes were detected on the filters.
Recently published studies not only demonstrated that laser printers are often significant sources of ultrafine particles, but they also shed light on particle formation mechanisms. While the role of fuser roller temperature as a factor affecting particle formation rate has been postulated, its impact has never been quantified. To address this gap in knowledge, this study measured emissions from 30 laser printers in chamber using a standardized printing sequence, as well as monitoring fuser roller temperature. Based on a simplified mass balance equation, the average emission rates of particle number, PM2.5 and O3 were calculated. The results showed that: almost all printers were found to be high particle number emitters (i.e. >1.01×1010particles/min); colour printing generated more PM2.5 than monochrome printing; and all printers generated significant amounts of O3. Particle number emissions varied significantly during printing and followed the cycle of fuser roller temperature variation, which points to temperature being the strongest factor controlling emissions. For two sub-groups of printers using the same technology (heating lamps), systematic positive correlations, in the form of a power law, were found between average particle number emission rate and average roller temperature. Other factors, such as fuser material and structure, are also thought to play a role, since no such correlation was found for the remaining two sub-groups of printers using heating lamps, or for the printers using heating strips. In addition, O3 and total PM2.5 were not found to be statistically correlated with fuser temperature.
Airborne particles are present throughout our environment. They come in many different forms, such as dusts, fumes, mists, smoke, smog, or fog. These aerosols affect visibility, climate, and our health and quanlity of life. This book covers the properties, behaviour, and measurement of aerosols. This is a basic textbook for people engaged in industrial hygiene, air pollution control, radiation protection, or environmental science who must, in the practice of their profession, measure, evaluate, or control airborne particles. It is written at a level suitable for professionals, graduate students, or advanced undergraduates. It assumes that the student has a good background in chemistry and physics and understands the concepts of calculus. Although not written for aerosol scientists, it will be useful to them in their experimental work and will serve as an introduction to the field for students starting such careers. Decisions on what topics to include were based on their relevance to the pratical application of aerosol science, which includes an understanding of the physical and chemical prinicples that underlie the behaviour of aerosols and the instruments used to measure them. (from preface)
The properties and behavior of suspended particles (dust, smoke, clouds), and the physical principles underlying their behavior are covered. Applications such as filtration, respiratory deposition, sampling, and the production of test aerosols are discussed. Physical analysis rather than mathematical analysis is emphasized.
Objectives: Thermoplastics may contain a wide range of additives and free monomers, which themselves may be hazardous substances. Laboratory studies have shown that the thermal decomposition products of common plastics can include a number of carcinogens and respiratory sensitizers, but very little information exists on the airborne contaminants generated during actual industrial processing. The aim of this work was to identify airborne emissions during thermal processing of plastics in real-life, practical applications. Methods: Static air sampling was conducted at 10 industrial premises carrying out compounding or a range of processes such as extrusion, blown film manufacture, vacuum thermoforming, injection moulding, blow moulding, and hot wire cutting. Plastics being processed included polyvinyl chloride, polythene, polypropylene, polyethylene terephthalate, and acrylonitrile-butadiene-styrene. At each site, static sampling for a wide range of contaminants was carried out at locations immediately adjacent to the prominent fume-generating processes. Results: The monitoring data indicated the presence of few carcinogens at extremely low concentrations, all less than 1% of their respective WEL (Workplace Exposure Limit). No respiratory sensitizers were detected at any sites. Conclusions: The low levels of process-related fume detected show that the control strategies, which employed mainly forced mechanical general ventilation and good process temperature control, were adequate to control the risks associated with exposure to process-related fume. This substantiates the advice given in the Health and Safety Executive's information sheet No 13, 'Controlling Fume During Plastics Processing', and its broad applicability in plastics processing in general.
A review of literature was undertaken to ascertain the current knowledge of the nature of the thermal decomposition products generated from ABS and the toxicity of these evolved products in toto. The literature review encompasses English language publications available through June 1984. This literature surveyed showed that the principal ABS thermooxidative degradation products of toxicologic importance are carbon monoxide and hydrogen cyanide. The experimental generation of these and other volatile products is principally dependent upon the combustion conditions and the formulation of the plastic. The toxicity of ABS thermal degradation products has been evaluated by fire methods. The LC50 (30 min exposure + 14 day post-exposure period) values for flaming combustion ranged from 15.0 mgl−1 to 28.5 mgl−1. In the non-flaming mode of combustion, the LC50 values ranged from 19.3 Mgl−1 to 64.0 mgl−1. Therefore, no apparent toxicological difference exists between the flaming mode and the non-flaming mode. The toxicity of ABS degradation products was found to be comparable with the toxicity of the thermal decomposition products of other common polymeric materials.