SUPPORTING INFORMATION

Plastic burning impacts on atmospheric fine particulate matter at urban and

rural sites in the United States and Bangladesh
Md. Robiul Islam1, Josie Welker1, Abdus Salam2, Elizabeth A. Stone1,3*
1
University of Iowa, Department of Chemistry, Iowa City, IA, 52242 USA
2
University of Dhaka, Department of Chemistry, Dhaka 1000, Bangladesh
3
Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA, 52242 USA
*Corresponding author e-mail: betsy-stone@uiowa.edu

Supplemental Text 1.

Thermal desorption (TD) is a method of introducing ambient PM collected on substrates into a gas
chromatograph (GC).1-4 In this technique, a small strip of aerosol containing filter is packed into a GC
inlet liner. This liner then loaded into GC inlet and heated to 275-300 oC to desorb the volatile and semi-
volatile compounds. During the desorption, the column temperature is maintained at 30 oC to
concentrate and focus the analytes at the GC column head. Then the GC column temperature is
gradually raised to facilitate the chromatographic separation.

The optimization of the GC inlet temperature for thermal desorption is a balance of fully desorbing
analytes without thermal decomposition. Standard solutions containing TPB with benzo(a)anthracene-
D12 as an internal standard were spiked on blank filters and analyzed at four different temperatures:
200, 250, 275, and 300 oC. The time required for the injector to reach 200, 250, 275, and 300 oC was 6.5,
9.0, 11.0, and 12.5 min respectively. For all experiments, the GC oven temperature ramp was initiated
14 min after the start of thermal desorption to maintain a constant total thermal desorption time.

The responses of TPB and benzo(a)anthracene-d12 at four thermal desorption temperatures were
normalized by their responses at 300 oC and are plotted in Figure S2a. The responses of both
compounds increased as the temperature increased from 200 to 275 oC. Increasing inlet temperature
further to 300 oC increased the response for benzo(a)anthracene by 9%, however it also decreased the
response for TPB by 2%. These results indicated that temperatures of 250 oC or lower are not sufficient
for complete thermal desorption of TPB. The temperature of 275 oC was selected, because further
increase in temperature did not increase the analyte response. This same desorption temperature was
determined to be optimum for the analysis of semi-volatile compounds including polycyclic aromatic
hydrocarbons (PAHs), alkanes, and phthalates in prior studies.5, 6

The optimum duration for thermal desorption is the minimum time that is required for complete
desorption of analytes from the filter substrate and their subsequent deposition at the GC column head.
After the injector reached to 275 oC, four time intervals, 1, 2, 3, and 5 min, were allowed to elapse
before the GC temperature program was started. The responses of TPB and benzo(a)anthracene-d12 at
these four elapsed times are plotted in S2b. Increasing the elapsed desorption time from 1 min to 2 min,
increased the responses of both analyte by 5-8% indicating a better desorption. Further increase in
elapsed time to 3 min increased the response of TPB by 11-14%, however decreased the response of
benzo(a)anthracene by 3-5% compared to their responses at 1 min elapsed time (Figure 2.4b). A
subsequent increase in desorption time did not alter the responses for any of the analytes. Based on

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these observations, the 2 min elapsed time was selected as optimum desorption time as it was the
minimum required time with maximum desorption efficiency for both analytes. The same elapsed time
was used in the analysis of PAHs, alkanes, and phthalates in prior studies.6, 7

Table S1. Summary of gas chromatography mass spectrometry (GCMS) operating conditions for the
solvent extraction and thermal desorption methods.
Component Operating Conditions Solvent extraction GCMS Thermal Desorption-
GCMS (with direct sample
introduction)
Injector Injection volume (μL) 2 -
Solvent wash draw speed (μL/min) 300 -
Inlet Carrier gas Helium (99.999%) Helium (99.999%)
Mode Splitless Splitless
Heater (°C) 300 (See Figure S1)
Pressure (psi) 8.5204 11.084
Total flow (mL/min) 70.2 70.681
Septum purge flow (mL/min) 3 3
Purge flow to split vent (mL/min) 66.2 at 1 min 66.2 at 13 min
GC Column HP-5MS (Agilent, 30 m x HP-5MS (Agilent, 30 m x
0.25 mm x 0.25 µm) 0.25 mm x 0.25 µm)

Oven Program Initial 65 °C; hold 10 min, Initial 30 °C, hold 13 min,
ramp at 10 °C/min to 300 ramp at 10 °C/min, to 120
°C, hold 25 min °C, ramp at 8 °C/min to
310 °C, hold 13 min
GC Transfer Setpoint (°C) 300 300
Line
MS Data Solvent delay (min) 11 16
Acquisition Mass range (m/z) 50-500 50-500
Mode Scan Scan
MS source (°C) 230 230
MS Quad (°C) 150 150

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Table S2. Summary of PM and TPB emissions data for the combustion of I) plastic and II) mixed waste containing plastic.
Combusted materials Burning Location of PM EFPM TPB/PM TPB/OC Reference
conditions testing size (mg kg-1) (ng mg-1) (ng mgOC-1)
I. Plastic
Polystyrene (PS) stove Romania PM10 53 ± 15 800 nm Hoffer et al. 20218
Polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), PS open burning Chile TSP nmA 208 nm Simoneit et al. 20059
PET stove Romania PM10 11 ± 1.6 100 nm Hoffer et al. 20218
PE (new bags) open burning Chile TSP nm 63 nm Simoneit et al. 20059
Acrylonitrile-butadiene-styrene (ABS) stove Romania PM10 82 ± 27 24 nm Hoffer et al. 20218
mixed plastics (predominantly PE) open burning Nepal PM2.5 84 ± 13 7 11 Jayarathne et al. 201810
PVC stove Romania PM10 35 ± 10 6.2 nm Hoffer et al. 20218
Polypropylene (PP) stove Romania PM10 33 ± 18 0.5 nm Hoffer et al. 20218
PE (new bags) open burning USA TSP nm 0.2 nm Simoneit et al. 20059
PE stove Romania PM10 18 ± 7 bdlB nm Hoffer et al. 20218
median of plastics C
100 200 D

II. Mixed waste containing plastic

landfill waste, 3.2% plastic (PE 17.3%, PET 29.7%, PVC 39.3%, PS 2.9%, unidentified
open burning Chile TSP nm 57 nm Simoneit et al. 20059
10.8%)
rags made of a mixture of cotton, polyester and polyamide fabrics stove Romania PM10 8.7 ± 0.22 15 nm Hoffer et al. 20218
paper, including colorful glossy-coated and uncoated stove Romania PM10 2.2 ± 0.11 75 nm Hoffer et al. 20218
furniture made of low density fiber board, including laminated coating and plastic Hoffer et al. 20218
stove Romania PM10 3.2 ± 1.3 23 nm
borders
mixed waste (damp food waste, paper, plastic bags, cloth, diapers, and rubber shoes) open burning Nepal PM2.5 125 ± 23 15 25 Jayarathne et al. 201810
mixed waste (damp food waste, paper, plastic bags, cloth, diapers, and rubber shoes) open burning Nepal PM2.5 82 ± 13 12 20 Jayarathne et al. 201810
mixed waste (dry domestic waste, containing cardboard and chip bags) open burning Nepal PM2.5 7 ± 1 51 45 Jayarathne et al. 201810
foil wrappers (damp) open burning Nepal PM2.5 50 ± 9 5 7 Jayarathne et al. 201810
PET (bottles) co-combusted with beech wood (7:93% by weight) boiler Czech Republic TSP 1.8 ± 0.3 13 nm Tomsej et al. 201811
PE (new bags) co-combusted with beech wood (7:93% by weight) boiler Czech Republic TSP 1.7 ± 0.2 4 nm Tomsej et al. 201811
PET (bottles) co-combusted with beech wood (reduced output, 7:93% by weight) boiler Czech Republic TSP 5.8 ± 0.7 13 nm Tomsej et al. 201811
PE (new bags) co-combusted with beech wood (reduced output, 7:93% by weight) boiler Czech Republic TSP 7.5 ± 0.5 1 nm Tomsej et al. 201811

A) Not measured, B) below detection limit, C) Excludes values < 10, which are not expected to contribute appreciably to ambient TPB concentrations; D) Estimated by assuming that OC accounts for 50% of PM mass.

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Table S3. Estimates of plastic burning contributions to PM2.5 organic carbon (OC) at four sites in the USA and in
Dhaka, Bangladesh. Lower and median values were calculated using TPB-to-PM emission ratios for polystyrene
(Hoffer et al. 2021) and the median of select literature values (Table S2), respectively.

Site Dates of Study n Lower estimate Median estimate

PM2.5 OC PM2.5 OC PM2.5 OC PM2.5 OC
(μgC m-3) (%) (μgC m-3) (%)
Atlanta, Georgia, USA 24-27 Aug 2015 4 0.002-0.02 0.06-0.6 0.02-0.2 0.5-5
Atlanta, Georgia, USA 19-22 Jan 2016 4 0.01-0.04 0.8-0.9 0.09-0.3 6-7
Houston, Texas, USA 18-20 May 2015 3 0.006-0.02 0.2-0.6 0.05-0.1 1-5
Iowa City, Iowa, USA 14-17 Nov 2015 4 0.002-0.03 0.1-1 0.07-0.2 1-10
Iowa City, Iowa, USA 16 Oct – 12 Nov 2020 10 0.02-0.04 1-2 0.1-0.4 6-17
Centreville, Alabama, USA 12-14 July 2013 4 0.002-0.01 0.04-0.3 0.01-0.08 0.4-2
Dhaka, Bangladesh Feb – April 2013 3 0.1-2 1-3 1-17 8-26

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Figure S1. Time events and temperature programs for GC inlet and column oven during the TD-GCMS
analysis.

Figure S2. Optimization of inlet temperature and desorption time for the TD-GCMS analysis of TPB.

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Figure S3. Mass spectra for 1,3,5-triphenylbenzene (TPB) collected under electron ionization at 70 eV using the
solvent-extraction GCMS and thermal desorption-GCMS conditions outlined in Table S1. The three m/z marked
were used to identify and quantify TPB.

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Figure S4: TPB concentrations measured in Iowa City, Iowa, USA in 2020.

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