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Effect of Temperature and Process on Quantity and Composition of Laboratory-generated Bitumen Emissions a

b

a

c

Christophe Bolliet , Anthony J. Kriech , Catherine Juery , Mathieu Vaissiere , Michael A. b

b

Brinton & Linda V. Osborn a

TOTAL Refining & Chemicals, Solaize, France

b

Heritage Research Group, Indianapolis, Indiana

c

TOTAL Marketing & Services, Paris, France Accepted author version posted online: 03 Feb 2015.Published online: 15 Jun 2015.

Click for updates To cite this article: Christophe Bolliet, Anthony J. Kriech, Catherine Juery, Mathieu Vaissiere, Michael A. Brinton & Linda V. Osborn (2015) Effect of Temperature and Process on Quantity and Composition of Laboratory-generated Bitumen Emissions, Journal of Occupational and Environmental Hygiene, 12:7, 438-449, DOI: 10.1080/15459624.2015.1009982 To link to this article: http://dx.doi.org/10.1080/15459624.2015.1009982

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Journal of Occupational and Environmental Hygiene, 12: 438–449 ISSN: 1545-9624 print / 1545-9632 online c 2015 JOEH, LLC Copyright  DOI: 10.1080/15459624.2015.1009982

Effect of Temperature and Process on Quantity and Composition of Laboratory-generated Bitumen Emissions Christophe Bolliet,1 Anthony J. Kriech,2 Catherine Juery,1 Mathieu Vaissiere,3 Michael A. Brinton,2 and Linda V. Osborn2 1

TOTAL Refining & Chemicals, Solaize, France Heritage Research Group, Indianapolis, Indiana 3 TOTAL Marketing & Services, Paris, France

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2

In this study we investigated the impact of temperature on emissions as related to various bitumen applications and processes used in commercial products. Bitumen emissions are very complex and can be influenced in quantity and composition by differences in crude source, refining processes, application temperature, and work practices. This study provided a controlled laboratory environment to study five bitumen test materials from three European refineries; three paving grade, one used for primarily roofing and some paving applications, and one oxidized industrial specialty bitumen. Emissions were generated at temperatures between 140◦ C and 230◦ C based on typical application temperatures of each product. Emissions were characterized by aerodynamic particle size, total organic matter (TOM), simulated distillation, 40 individual PACs, and fluorescence (FL-PACs) spectroscopy. Results showed that composition of bitumen emissions is influenced by temperature under studied experimental conditions. A distinction between the oxidized bitumen with flux oil (industrial specialty bitumen) and the remaining bitumens was observed. Under typical temperatures used for paving (150◦ C–170◦ C), the TOM and PAC concentrations in the emissions were low. However, bitumen with flux oil produced significantly higher emissions at 230◦ C, laden with high levels of PACs. Flux oil in this bitumen mixture enhanced release of higher boiling-ranged compounds during application conditions. At 200◦ C and below, concentrations of 4–6 ring PACs were ≤6.51 μg/m3 for all test materials, even when flux oil was used. Trends learned about emission temperature-process relationships from this study can be used to guide industry decisions to reduce worker exposure during processing and application of hot bitumen. Keywords

bitumen emissions, fluorescence, polycyclic aromatic compounds, simulated distillation, total organic matter

Address correspondence to: Linda V. Osborn, Heritage Research Group, 7901 W. Morris St., C, Indianapolis, IN 46231; e-mail: linda. [email protected]; Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/uoeh. 438

INTRODUCTION

B

itumen is a product processed from the vacuum distillation of crude oil in petroleum refining. Depending on the properties of the initial crude oil, the vacuum distillation residue can be blended with products obtained by further separation in a deasphalting process or with residue processed by blowing air through it at elevated temperatures to alter its physical properties for commercial application. Bitumen treated in the blowing unit is used in both roofing and industrial specialty products. According to the assessment performed for Registration, Evaluation, Authorization and Restriction of Chemical substances (REACh) registration, bitumen is classified as a nonhazardous product.(1) During the manufacturing process of crude oil, lowest boiling molecules are removed; thus the residuum from vacuum distillation of crude oils (bitumen) does not emit fumes under ambient service conditions. During application at elevated temperatures, small quantities of hydrocarbon emissions may be released. In October 2011, the International Agency for Research on Cancer concluded that “Occupational exposures to oxidized bitumens and their emissions during roofing are ‘probably carcinogenic to humans’ (Group 2A); occupational exposures to hard bitumens and their emissions during mastic asphalt work are ‘possibly carcinogenic to humans’ (Group 2B); and occupational exposures to straight-run bitumens and their emissions during road paving are ‘possibly carcinogenic to humans’ (Group 2B).”(2,3) A large epidemiologic study conducted by Olsson et al. showed no increased incidence of lung cancers for European bitumen industry workers.(4) Inhalation animal studies conducted by Fuhst et al.,(5) on air-rectified paving bitumen showed no significant tumor formation in rats. Clark et al.(6) summarized recent mouse skin painting study results which highlight that the paving fume condensate was not carcinogenic under their test conditions whereas field-matched Type

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III Build-Up Roofing Asphalt (BURA) (oxidized bitumen) fume condensate produced a weak tumorigenic response. Trumbore et al.(7) showed that the oxidation process does not appear to increase the formation of biologically active. However, the higher application temperature required for roofing as compared to paving, allows them to be more readily released. By design, bitumen information was not disclosed for the Fuhst(5) and Clark.(6) Studies. This study provides physical/chemical properties of the bitumen test articles and discloses the refining processes used. Manufacturing and application of paving hot mix asphalt is typically conducted between 140 and 160◦ C. In some roofing applications, bitumen is heated between 200 and 230◦ C. In the United States., roofing kettles are typically heated to temperatures exceeding 260◦ C and common excursions above 290◦ C are pushing the industry to try to put an absolute maximum on kettle temperatures regardless of flashpoint. To avoid uncontrolled parameters involved in construction and industrial workplaces, fume generations to study temperature effects have been performed in the laboratory with various designs. Brandt et al. designed a laboratory rig for bitumen fume generation that has been validated against field samples.(8) However, this validation has been performed only for the aerosol fraction using a benzene soluble fraction (BSF) that does not include the vapor phase. Although other systems may also be suitable, this method was selected because it requires only ∼500 grams of material and produces reproducible results. Results obtained with the Brandt et al. method(8) do not represent real world fumes, but do provide a method of comparison between products. Measurement of known toxic compounds or toxicological markers is important to characterize the hazard of the fume condensate. A select group of polycyclic aromatic compounds (PACs) are recognized as priority molecules of concern, i.e., the 4–6 ring PACs.(9) PACs are naturally present in crude oil and petroleum products, including bitumen. Some of these compounds have been identified as known carcinogens. Numerous studies have shown that the chemistry and quantity of fume is dependent on the temperature at which the fumes are produced. Reinke et al.(10) compared the chemistry of PACs and sulfur (S)-PACs and mutagenic potency of fieldand laboratory-generated bitumen fumes. Summary data from the sulfur heterocyclic PAC analyses showed that at higher temperatures, there were substantially higher concentrations of the 4-ring S-PACs, which are the size of concern. Kriech et al.(11) conducted a field study on 42 bitumen-roofing workers at 7 built-up roofing sites across the United States which evaluated exposure to bitumen fumes when using standard BURA and fume suppressing BURA. Personal exposure was reduced by reducing temperature and improving work practices. Cavallari et al.(12,13) have shown that temperature is an important determinant of both airborne and dermal exposures. Reducing the application temperature of hot mix asphalt from 149◦ C to 127◦ C reduced airborne exposures by 42–82%. The purpose of our laboratory-based study was not to characterize occupational exposure in the field, but rather to con-

duct an investigation of how composition and temperature dependence may differ in bitumen emissions. To characterize the bitumen emissions generated, aerodynamic particle size, total organic matter (TOM), simulated distillation (Sim-Dis), concentration of individual PACs with gas chromatography with time-of-flight mass spectrometry (GC/TOF-MS) and fluorescence (FL-PACs) were studied. MATERIALS AND METHODS Bitumen Samples and Characterization Several manufacturing methods are available to produce bitumen to meet physical performance specifications depending on crude oil sources and processing capabilities.(9) The most common refining process used for producing bitumen is straight reduction to grade from petroleum crude oil blend using atmospheric and vacuum distillation. The product is called straight run bitumen (CAS #64741-56-6).(14) Blown bitumen (CAS#64742-93-4) is made in a specific unit known as the bitumen blowing unit (BBU). The BBU consists of passing air through bitumen feedstock at elevated temperatures to alter its physical properties. From this, two types of products with distinctly different properties are produced: air rectified and oxidized bitumen.(15) Functionally, air rectified bitumens are identical to straight-run bitumens. Deasphalting pitches (CAS#91995-23-2) are produced by processing through a solvent deasphalting unit. In a visbreaking unit, the thermally cracked residue (CAS#92062-05-0) is subjected to vacuum distillation to remove the distillate fractions. The final bitumen product must meet technical specifications, which can be achieved directly in the refining process or by blending different grades of bitumen. Flux oil (heavy vacuum gas oil) can be used to soften the feed of the BBU to reach specific properties useful in roofing applications or other industrial specialty products. Any flux oil must be registered for use in the manufacture of blown bitumen; the manufacturer is required to identify the flux oil, its hazards, and its risks.(16) Five bitumen samples, B1 to B5, representative of the processes described above, were selected for this study and represent commercial bitumen from three different European refineries, except B3. B3 is oxidized bitumen sold for blending with soft base bitumen obtained by distillation similar to a Type 3 BURA, produced by oxidation without addition of flux oil used in the Clark et al., (6) skin painting studies. B4 is industrial specialty bitumen that has a very high penetration index. Fume generations and respective characterizations started in June 2011. All bitumen samples were submitted to the laboratory without substance identification until data were generated (denominations in Table I). To determine the reproducibility of the fume generation methodology, B5 was blindly studied at the same temperature (170◦ C) in triplicate and the other two fume generations referred to as B6, B7. Physical properties of the neat bitumen were characterized by determination of the penetration (pen: EN 1426:2005),(17) softening point (SP: EN 1427:2005),(18) kinematic viscosity at 100◦ C (EN 12595:2007), and open cup flash point (EN

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TABLE I. Details of Study Test Materials Name Bitumen 1 (B1) Bitumen 2 (B2) Bitumen 3 (B3) Bitumen 4 (B4)

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Bitumen 5 (B5) Bitumen 6 (B6) Bitumen 7 (B7)

Description

Comments

Distillation vacuum residue Air rectified bitumen (PI ≤ 2) Oxidized bitumen (PI > 2) – Pen < 20 1/10mm) from distillation vacuum residue Oxidized bitumen (PI > 2– Pen > 20 1/10mm) with incorporation of flux oil in the feed of blowing bitumen unit Blend of distillation vacuum residue, air rectified bitumen, visbreaker, vacuum residue, and deasphalting pitches

Refinery 1 - Paving application Refinery 2 - Paving application Refinery 2 - Hard base for paving similar to BURA Type III Refinery 3 - Industrial bitumen application

22592:1994) (19) Penetration Index (PI) provides an evaluation of the thermal susceptibility and is determined mathematically using penetration and SP values according to Pfeiffer and Van Doormal’s equation: (20): PI =

192 − 500 × log(pen) − 20SP 50 × (pen) − SP − 120

Thermal Gravimetric Analysis (TGA)(21,22) was also performed on these test materials. TGA is an analytical technique used here to determine the bitumen’s thermal stability and its fraction of volatile components by monitoring the weight change that occurred as the bitumen was heated. The instrument program was optimized to examine the temperature region that corresponds to bitumen use temperatures. In addition to typical overlays, the weight loss (%) was reported for each test article at 250◦ C. In addition to these physical testing measurements, PACs in bitumen were tested using a GC/MS method EN 15527.(23) This is a British-adopted European standard method. All samples were analyzed in duplicate. Emission Generation Apparatus and Characterization Methodology Emissions used in this study were generated using a method similar to one described by Brandt.(8) Laboratory-generated emissions are typically higher than those found in the workplace environment due to the semi-closed reactor used and the continuous stirring of bitumen required to avoid localized overheating, providing worst-case results. Bitumen samples were pre-heated in an off-line oven to the desired temperature. Then 200 ± 1 grams of the heated bitumen were transferred to the reactor, retained under controlled temperature and a controlled stirring rate of 125 rotations per min (rpm), a departure from Brandt (8) conditions required to prevent overloading of the sampling system at the higher temperatures. Once equilibrated to the specified temperature, emissions were captured on three sorbent tubes: two XAD2 sorbent tubes followed by one XAD-2 + charcoal sorbent tube sequentially connected. Emissions from the reactor were

440

Refinery 2 - Paving application B5, B6, B7 is the same product to check the validity of protocol

drawn through this sampling train using a vacuum pump calibrated to a flow rate of 2.0 L per min (lpm) for 10 min. Emissions collected on the XAD-2 + charcoal sorbent tubes were eluted using dichloromethane. Each tube is eluted separately, and then an equal aliquot of each combined for analyses. The five samples of bitumen were studied at varying temperatures ranging from 140 to 230◦ C (see Table II) which were selected because they encompass typical temperature ranges of product use. A total of 21 laboratory generation tests and a blank were performed in the study with emissions characterized. One bitumen was blindly tested in triplicate (labeled B5, B6 and B7) at 170◦ C to check the repeatability of the emission generation apparatus. Figure 1 provides an overview of the test methods selected to characterize the bitumen emissions in this study. A Model 3320 Aerodynamic Particle Sizer Spectrometer (TSI, Inc., St. Paul, MN) was used to determine the aerodynamic size measurements and light scattering intensity in real time using low particle accelerations and to check the homogeneity of emissions. Mean number particle size information was collected for each sample along with mass

TABLE II. Outline of Fume Generations for the Study Fume Generation Temperatures (◦ C) Samples Bitumen 1 Bitumen 2 Bitumen 3 Bitumen 4 Bitumen 5 Bitumen 6 Bitumen 7

140

155

X X X

170 X X X X X X X

185

200

230

X X

X X X X

X X X X

X

Note: X = trial on the bitumen at the defined temperature; blank not shown.

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FIGURE 1. Overview of Analytical Scheme for Bitumen Emissions. GC = gas chromatography, FID = flame ionization detection, MS = mass spectrometry, PACs = polycyclic aromatic compounds, TOM = total organic matter, PRE-CN indicates that no cyanopropyl clean-up was performed.

particle size concentration. Mass particle size concentration represents the total mass of the particles per unit volume of air sampled (i.e., mass concentration expressed as μg/cm3). The instrument, calibrated by the manufacturer (TSI), provides two measurements: aerodynamic size and relative light-scattering intensity. It detects particles in the 0.37 to 20 micrometer range, with high resolution sizing from 0.5 to 20 micrometers. To quantitate the concentration of bitumen emissions released (TOM) and allow compositional comparisons of the emissions generated, we used gas chromatography equipment with flame ionization detection (GC/FID) following a modified SW 846-8015D method.(24) No internal standards or surrogates were used due to the multiple tests conducted on the

same extracts. We quantified the amount of emissions using kerosene external standard calibrations for all samples except B5, quantified using diesel #6 fuel oil. Complementary to the TOM, simulated distillation (SimDis) using ASTM D-2887 (25) permitted the determination of boiling point distributions at various generation temperatures as compared to a series of n-alkane standards from C6 to C44. The theoretical calculation involves relating analyte retention times to the boiling points of the various hydrocarbons. A calibration curve is generated from a standard sample, where the retention time of each n-alkane is plotted against its boiling point. It is known that occupational exposure to bitumen emissions is often measured using a National Institute for Occupational Safety and Health (NIOSH) method 5042 that includes determination of benzene soluble fraction BSF of the total particulate exposure. Indeed, this fraction of the emissions contains the majority of 4–6 ring PACs, in which most carcinogenic PACs, identified in animal skin painting test,(26) are found. However, all emissions (volatile and aerosol) that workers are exposed to are important; TOM represents all of these emissions and has been used in animal studies.(5,6) To determine the relative amounts of the total 4–6 ring PACs in the emissions, a fluorescence method was used using a Perkin Elmer (Waltham, MA) Luminescence Spectrometer LS50B following protocol previously described.(27) Modifications to this method included that the samples were analyzed directly in dichloromethane and did not include the cyclohexane cleanup step. This was because many samples yielded

FIGURE 2. This overlay of actual thermogravimetric (TGA) measurements of the five different bitumens shows the weight loss percent as the temperature increases, in the range that emissions would be produced. B1 was a weight loss of only 0.50% at 250◦ C, with B5 following a nearly identical pattern (weight loss = 0.53% at 250◦ C). B2 and B3 resulted in a weight loss of 0.80 and 1.15%, respectively, at 250◦ C. B-4 yielded a substantially different pattern at 5.07%.

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TABLE III. Physical Properties of Bitumens Used in This Study Tests Matrix Pen 25◦ C Softening Pt. Penetration Index Flash point Total  PACs REACh 8 PACs (36)

Units

Standards

B1

B2

B3

B4

B5-7

1/10mm C – ◦ C mg/g mg/g

EN 1426:2005 EN 1427:2005 – EN 22592:1994 EN 15527 EN 15527

43 52.4 –0.9 362 7.2 2.65

43 58.8 0.4 334 6.80 1.60

17 89.5 3.0 326 25.0 59.9

41 106.5 6.8 272 21.3 49.0

45 52.6 −0.8 338 3.75 19.6



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Note: PACs = polycyclic aromatic compounds; REACh = registration, evaluation, authorization, and restriction of chemicals.

a response too low to perform the cleanup step and it was important to be consistent across the board to allow direct internal comparison. Osborn et al.(27) demonstrated that the fluorescence method correlated extremely well (R2 = 0.98) with results of the NIOSH dermal cancer assays. Results are reported as EU/g, which represents emission units per gram calculated as EU/TOM (g/mL)/10,000 fluorescence results normalized using Total Organic Matter. Providing a more in-depth look at the compositions, 40 PACs listed in Supplemental Table I were determined using GC/TOFMS following the guidelines of EPA SW-846 8270C(28) with published modifications outlined by Trumbore et al.(7) This list includes 9 of the 13 heterocyclic PACs recently reviewed by the International Agency for Research on Cancer (IARC) as agents with bitumen and bitumen fumes for Monograph Volume 103. The four remaining PACs had

no standards readily available. Using a Leco (St. Joseph, MI) Pegasus II GC/TOFMS, the required perfluorotributylamine tuning procedure was successfully achieved followed by a decafluorotriphenylphosphine tuning check. An Agilent (Santa Clara, CA) column was used (30 m × 0.25 mm × 0.15 μm CP7462), which resulted in resolution of all 40 PACs. Although bitumen emissions contain PACs not contained on this list of 40, these parent compounds are used as indicators and summary 4–6 ring PACs here do not represent the alkylated versions of these constituents. RESULTS Physical and Chemical Properties of Bitumen Samples Physical properties and PAC measurements for each bitumen in this study are presented in Table III. Results of

FIGURE 3. Evolution of Total Organic Matter (TOM) as mg/m3 as a function of temperature. B1 shows a steady increase in TOM as the temperature increases. B2 and B3 generally show an increase in TOM with increased temperature. However, B4 (industrial specialty bitumen) shows a distinctly different pattern. B5 –7 show similarities at 170◦ C and a slight increase at 185◦ C. Error bars are based on + 20% per US EPA protocol.

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penetration and SP confirmed that the samples selected cover the entire range of PI from 1.0 to +7.0. To characterize the volatility of bitumens, TGA overlays are shown in Figure 2 at temperatures ranging between 130◦ C and 250◦ C. The TGA% weight loss was compared with the softening point data, which showed a similar rank order. B1 showed a weight loss of only 0.50% at 250◦ C, and B5 followed a similar pattern with a weight loss of 0.53% at 250◦ C. B2 and B3 resulted in a weight loss of 0.80 and 1.15%, respectively, at 250◦ C and had nearly identical curves. B-4 yielded a substantially different pattern with 5.07% weight loss at 250◦ C. PAC measurements of the bitumen binder show that B1, B2, and B5–7 contain fewer PACs compared to B3 and B4. Summation of all detectable PACs resulted in 7.2 mg/kg, 6.8 mg/kg, and 19.6 mg/kg for B1, B2, and B5-7, whereas B3 and B4 were 60.0 mg/kg and 49.0 mg/kg, respectively. When summing the REACh 8 PACs that include benz[a]anthracene, benzo[a]pyrene, benzo[e]pyrene, benzo [b]fluoranthene, and the j and k isomers, chrysene, and dibenzo[a,h]anthracene, results were 2.65 mg/kg, 1.60 mg/kg, and 3.75 mg/kg for B1, B2, and B5-7, whereas B3 and B4 were 25.0 mg/kg and 21.3 mg/kg, respectively. Since oxidizing reduces PACs, the values for total PACs of B3, which has no flux oil added, indicates that it is from a much different crude source than B1 and B2. Validation of Emission Generation Methodology B5, B6, and B7 correspond to separate samples of the same bitumen, blindly submitted. Triplicate generations of this bitumen were collected at 170◦ C. TOM measurements resulted in a relative standard deviation (RSD) of 8.0% (TOMaverage = 59 +/−4.7 mg/m3). For PAC measurements, fluorene, naphthalene, phenanthrene, and dibenzothiophene were the more prominent PACs detected in emissions, all with similar concentrations. For these triplicate tests, the arithmetic mean of the sum of PACs detected in emissions was 103 μg/m3 (RSD = 9.1%). Summary data are shown in Table IV. Additionally, duplicate fume generations and analyses for B-2 at 200◦ C and 230◦ C are shown in Table IV. According to these results on different types of bitumen, the repeatability of the emission generation and characterization procedure has been confirmed. Physical and Chemical Properties of Bitumen Emissions From European refineries, various bitumen samples were selected to include different manufacturing processes. Operating conditions associated with each emission generation are described in Supplemental Table II. Results of emission extracts at each temperature are reported in Supplemental Table III, with individual PACs listed in Supplemental Table IV. Aerodynamic particle size data are shown in Supplemental Table V which shows the homogeneity of the emissions in terms of mean number particle size. Within a given bitumen, increase in temperature yielded larger particle sized materials and higher particle concentrations. This behavior has a linear

trend for B1, B2, and B3. B4 has a behavior close to the others for temperatures ≤200◦ C; however, for 230◦ C, the particle size increased more dramatically. TOM data (Figure 3) show that within a given bitumen, as the emission generation temperature increased, the TOM concentration increased. Similar to the aerodynamic particle size concentrations, B4 reveals different behavior with a greatly increased emission generations at a temperature of 230◦ C. At 170◦ C, the TOM content is similar [∼100 mg/m3] for all bitumens. However, as temperature increases, two trends appear; a linear increase of TOM versus temperature between 140◦ C and 230◦ C (B1, B2, B3) and a more dramatic increase of TOM versus temperature between 170◦ C and 230◦ C (B4). Sim-Dis results on all emissions are shown in Supplemental Table III and represented in Figure 4 for paving emissions and Figure 5 for roofing emissions. Results clearly show how the simulated distillation curves increased with the increased temperature. Production of higher molecular weight compounds also increased with increasing temperature. Differences between the lowest and highest emission generation temperature, within a given bitumen, are significantly different. B3 is compared to TR-A since physical properties are most similar to the Type 3 BURA, in terms of pen, SP and flash point, used by Kriech et al.(29) Excluded from Figures 4 and 5, B4 generated the highest boiling emissions as compared to the other bitumens. At temperatures close to 170◦ C, the Sim-Dis from B4 emissions is similar to the other bitumens up to ∼60% distilled; however, > 60%, the boiling point of B4 emissions increased substantially suggesting that high molecular weight compounds are present. At the 230◦ C emission generation temperature, the Sim-Dis profile from B4 is completely different than the others indicative of higher molecular weight compounds in these emissions. A summation measure of 4–6 ring PACs, FLU-PACs (EU/g TOM) are reported in Supplemental Table III and reflect the potency of the material.(7) For a given bitumen, FLU-PACs increased with increasing temperature as shown in Figure 6. Determining concentrations of individual parent PACs for each of the emissions allowed us to see the impact of temperature on the release of these compounds. Results of PACs for each test are reported in Supplemental Table IV. Of the 40 individual PACs tested, 25 were below the limit of detection (LOD) for each of the 21 emission generations in this study. Benz[a]anthracene, benzo[b]fluoranthene, and chrysene were always below LOD. Of the nine IARC Monograph 103 PACs evaluated, only carbazole and dibenzothiophene were detected. Dibenzothiophene was detected in all samples, whereas carbazole was only detected in B4 at 230◦ C at a concentration near the LOD. Benzo[a]pyrene was not detected in any of the emission samples; in fact, no 5- through 6-ring PACs were detected. Therefore it is unlikely that the four 6-ring IARC PACs are present. In the paving bitumen emissions, pyrene, a noncarcinogenic PAC, was the only 4-ring PAC detected. Figure 7 represents the PAC concentrations detected in each sample for each emission generation temperature and include the 2-ring

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TABLE IV.

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Duplicates

Replicability Study Results B2-200◦ C

Temperature (◦ C) 200 Air Volume (L) 18.68 Mass (g) 200.1 Stir rate (rpm) 125 1.53 Particle Size Concentration (mg/m3) 132 Total Organic Matter (mg/m3) Fluorescence Analysis (EU/g) 220 Simulated Distillation (◦ C) 10% Distilled 192 20% Distilled 226 30% Distilled 249 40% Distilled 265 50% Distilled 281 60% Distilled 296 70% Distilled 314 80% Distilled 335 90% Distilled 365 Polycyclic Aromatic Compound (μg/m3) Anthracene 5.19 Fluoranthene bdl Fluorene 176.8 Naphthalene 38.6 Phenanthrene 41.2 Pyrene bdl Dibenzothiophene 77.2 Sum of detected PACs 339 Sum of detected 16 US-EPA PAHs 262 All other individual PACs were bdl (below limit of detection). Triplicates B-5 170◦ C Number Particle Size (μm) 0.893 57.1 TOM (mg/m3) 179 10% Distilled (◦ C) 258 50% Distilled (◦ C) 344 90% Distilled (◦ C) 98 Sum of 15 detectable PACs (μg/m3)

B2-200◦ C

B2-230◦ C

B2-230◦ C

200 18.73 200.2 125 1.36 119 198

230 18.38 200.6 125 2.22 202 310

230 18.41 200.1 125 2.46 298 262

195 227 249 265 280 295 312 334 364

214 251 272 292 309 326 344 363 388

210 250 272 293 310 328 344 364 389

3.96 bdl 139 28.9 33.7 bdl 63.3 269 206

11.9 9.65 265 32 70.8 10.8 143 544 400

21.2 13.6 318 37.8 79.3 11.6 175 656 481

B-6 170◦ C 0.896 64.3 175 260 365 108

B-7 170◦ C 0.897 55.4 174 264 363 104

%RSD 0.23 8.02 1.50 1.17 3.24 4.87

Note: PACs = polycyclic aromatic compounds%RSD = % relative standard deviation.

PACs, 3-ring PACs, and 4+-ring PACs as determined by the number of benzene rings in the molecule. The chart breaks down the concentrations into 2, 3, and 4+-ring concentrations. Results show that at 140◦ C, only 2-ring PACs are present in emissions; for temperatures ranging from 140◦ C and 170◦ C, 2and 3-ring PACs are present in the emissions. For temperatures ranging from 185◦ C up to 230◦ C, 2–4 ring PACs were detected. However, the proportion of the sum of 4+- ring PACs is low (less than 3% mass) compared to 2 and 3 rings. Relationships between the PAC concentrations versus temperature are shown in Figure 7 with linear behavior as temperature increases. Emissions from the industrial bitumen with flux oil (B4) contained pyrene and five additional 4-ring PACs (benz[a]anthracene, benzo[b]fluoranthene, 5-methylchrysene, 444

chrysene, and benzo[e]pyrene) at a generation temperature of 230◦ C. Four-ring PACs appeared at 170◦ C but represented a low percentage of the sum of all detected individual PACs (less than 3% mass) for temperatures ≤200◦ C. At 230◦ C, the quantity of emissions increased in a quadratic manner for B4 and the proportion of 4+-ring PACs also increased similarly. At 230 ◦ C, the 4+- ring PACs represented ∼ 15% of the sum of all detected PACs. As seen in Figure 7, PAC concentrations for B4 dramatically increase with an increase in temperature. DISCUSSION

W

e evaluated and quantified the relationship between application temperature, refining manufacturing

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FIGURE 4. Paving emission simulated distillation curves that include the arithmetic mean for the emissions from this study as dotted lines (average at each temperature) and the Kriech et al.(29) (arrowed lined) paving fume condensate TP-D. (170◦ C include B1, B2, B5, B6, B7 emissions; 200 and 230◦ C include B1 and B2 emissions).The horizontal line indicates the boiling point of pyrene, the first 4-ring PAC, below which no 4–6 rings would be expected to be present. For paving bitumen, emissions generated at 230◦ C and below show no evidence of a boiling point range that would include 4–6 ring PACs.

processes, and chemical emission concentrations from five bitumen products. Our results suggest temperature is the main driver of PAC emissions under studied experimental laboratory conditions. However, the concentration of 4–6 ring PACs indicates that some manufacturing processes involved in the production of bitumen products can substantially affect emission composition. Emission concentrations were evaluated for different types of bitumen suited for various applications that encompass a portion of their typical application temperature at 140 –230◦ C. We observed a linear relationship between TOM and temperatures for three of the four bitumens studied. B-4 was an anomaly; with increased temperature, TOM values increased in a quadratic manner for this limited number of data points. This variant behavior of B4 may be caused by flux oil used in the feedstock before processing in the blowing bitumen unit. A recent study (30) shows that the blowing process itself does not create PACs in the bitumen, however, the incorporation of certain flux oils in the blowing operation may increase the PAC concentration, dependent on the quality of the flux oil and amount used. The presence of this flux oil could cause a decrease in the flash point and an increase of emissions. During work with hot bitumen, exposure to PACs can potentially arise from many different sources such as emissions from bitumen, exhaust gases from the plant and equipment at the workplace, dust from the removal of old surfacing, and so on. PAC exposure data show 2–3 ring PACs (such as naphthalene, fluorene, anthracene, phenanthrene), which

have boiling points below 340◦ C, are generally present in the emission extract in higher concentrations than the 4–6 ring PACs.(6,12,29) It is not known how emissions generated from this modified Brandt laboratory fume generation (8) apparatus compare to typical worker exposures since no direct comparisons have been made using these collection and analytical methods. Here we investigated different crude sources and bitumen bases and determined what happened under controlled conditions. The more energy put into the system, the more biologically relevant materials that are trapped in the bitumen can be released. An increase of temperature allowed increase in the ring size of PACs and boiling point distributions in the resultant emissions. Recent studies demonstrated the same conclusions of increasing PAC concentration when comparing laboratory paving bitumen emissions generated at 150–180◦ C (Law et al.,(31) Cavallari et al.(32)) as well as 232◦ C – 316◦ C (Machado et al.,(33) and Cavallari et al.(32)). In the study of Kriech et al., (29) characterization of fume from the four Type III BURA bitumen with crude sources based on prominence of use within the US roofing industry are presented; however, no information on the process was reported. In the study by Clark et al.,(6) the BURA fumes were evaluated in 2-year dermal carcinogenicity assays in male mice and the authors concluded that fume extract from the field BURA III condensates produced a weak tumor response, while paving bitumen did not. In our study, the fume condensates used were generated, collected, characterized, and compared to these reference materials.

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FIGURE 5. Roofing emission simulated distillation curves that include five temperatures from this study (B3) as a solid line and the Kriech et al.(29) (dashed lined) Type III BURA fume condensate TR-A, and LR-A produced using the NIOSH fume generation protocol. At a fixed temperature, the percentage distilled of B3 at all temperatures is lower than the TR-A or LR-A sample. The horizontal line indicates the boiling point of pyrene, the first 4-ring PAC, below which no 4–6 rings would be expected to be present. Using roofing bitumen at 230◦ C and above, the boiling point range is such that 4–6 ring PACs would be slightly possible, but less than that of either TR-A or LR-A in the Kriech et al. (29). B3 is compared to TR-A since physical properties are similar to the Type 3 BURA used in the Kriech Study.

Sim-Dis results from LR-A (lab-generated roofing), TRA (field-matched roofing), and TP-D (field-matched paving) emissions described by Kriech et al.(29) have also been included in Figure 4 or Figure 5. The simulated distillation curve of TP-D is most similar to that of the paving bitumen

at 170◦ C used in this study. The horizontal line shown in Figures 4 and 5 represents the boiling point of pyrene, the first 4-ring PAC, below which no 4–6 rings would be expected to be present. Field results show the presence of pyrene, a 4ring PAC that is non-carcinogenic. McClean et al.(34) reported

FIGURE 6. Fluorescence (FLU-PAC) results - Emission unit per gram (EU/g) per mL of TOM for each fume generation. Error bars represent+/3 standard deviation of two measurements

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FIGURE 7. Summary of PAC concentrations for each emission generation including delineation of 2-, 3-, and 4-ring sums (μg/m3) - Error bars are 3 times the standard deviation.

0.18 μg/m3 of pyrene, and Hicks (35) showed 0.13 μg/m3 of pyrene. The combination of TGA and Sim-Dis provides a unique way to screen bitumens for potential worker exposure to compounds of concern. Focusing on the region that is in line with application temperature ranges, if the TGA shows high volatility (i.e., B4 at 230◦ C in Figure 2), and the Sim-Dis shows compounds boiling above 404◦ C (B4 at 75% distilled and above in Figure 5), then the potential is there for workers to be exposed to compounds of health concern. Further testing to investigate this potential is needed. On the other hand, if the TGA shows low volatility (i.e., B1 at 230◦ C in Figure 2), and the Sim-Dis shows no compounds boiling above 404◦ C (B1 in Figure 5), then the potential for 4 –6 ring PAC exposure is not present. In the fume condensate from Type III BURA (Kriech et al.(29)), 16 PACs have been investigated; 11 PACs are in common with the 15 PACs quantified in B4—naphthalene, acenaphthene, anthracene, fluorene, phenanthrene, benzo[a] anthracene, chrysene, fluoranthene, pyrene, benzo[b] fluoranthene, and benzo[e]pyrene. Additionally, Type III BURA condensate contained 4 and more ring PACs including triphenylene, benzo(k)fluoranthene, benzo(a)pyrene, indeno (1,2,3-cd)pyrene, and benzo[g,h,i]perylene. In the two studies, phenanthrene and fluorene are the most prominent parent PACs in the fume condensates. In the Kriech et al.(29) study, pyrene, a 4-ring PAC, is also mainly present, whereas in our present study, naphthalene and dibenzothiophene are present (2-ring PAC). Measurements of PACs in bitumen have been performed according to EN 15527. (23) Results show that the sum of the REACh 8 (36) PACs in bitumen B1, B2, and B5 – 7 contain ∼5 times less than B3 and B4 (Table III). Despite

the similarity, B3 and B4 have completely different behavior with increased temperature due to the addition of the flux oil. Considering PAC mass balance (mg/kg) for each bitumen, B4 has the lowest results with a TOM concentration one order of magnitude higher as compared to the others. Thus, no relationship between the PACs in liquid phase and total PACs in emissions is apparent. The presence of flux oil in B4 influences release of high molecular weight compounds in the emissions, having significant impact on the fume quality. Such additives make it impossible to relate the emissions’ PAC concentration to the base bitumen PAC content. Individual parent 4 – 6 ring PACs were detected in emissions from B2 at 230◦ C, B3 and B4 at 185◦ C/ 200◦ C / 230◦ C, and B7 at 185◦ C. No individual parent 4 – 6 ring PACs were detected in B1 emissions. Cavallari et al.(32) characterized fume condensates from paving and roofing emissions at various temperatures (120◦ C – 315◦ C). The results were statistically summarized and showed that temperature has a significant impact on fume qualities. For paving and roofing bitumen, the PAC concentration increase was not linear with temperature; the lower boiling 2-ring PACs dominated and the concentration of PACs decreased with increased ring-size. We noticed in the Cavallari et al.(32) publication that temperature alone did not explain the difference between paving bitumen and BURA concentrations for 5- to 6-ring PACs. In our present study, the nonlinear relationship between PAC concentration and temperature was observed only for B4 in the temperature range of 170◦ C – 230◦ C. Regarding the relationship between others bitumen, it seems to be linear in the temperature range of 140◦ C – 230◦ C for B1 and B2, and 155 – 230◦ C for B3.

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Cavallari et al., (32) conclude that BURA fumes are different from paving fumes and showed higher levels of 5–6 ring PACs as compared to paving fumes at the same temperature. The authors suggest that these differences are linked to the reaction that occurs during the air-blowing and oxidation process. Our data suggest that emission concentration temperature relationship was only different for B4 compared to the others. B4 had a behavior comparable to others in the temperature range (140◦ C – 230◦ C). Trumbore et al.(7) compared emissions from five bitumens before and after the oxidation reaction controlled under laboratory conditions. The authors reveal that the oxidation reaction significantly decreased the PACs that have been linked previously to tumor incidence in rodent bioassays. Mutagenicity index was also reduced by a range of 41% to 50% from the feedstock. Our laboratory data also suggest that the oxidation process is not directly responsible for an increase of 5–6 – ring PACs in bitumen emissions. Reducing the temperature while bitumen is handled appears to reduce both the hazard and potential risk. The hazard is decreased because fewer 4 – 6 ring PACs are released (10,29,32) and worker risk is diminished because both the hazard level and occupational exposure levels decrease with decreased temperature of use.(12) The laboratory measures used in this study appear to provide good indicators to help guide industry to make healthbased determinations of critical application and process temperatures and procedures.

GC/FID: GC-MS: GC/TOF-MS: IARC: LOD: MI: NIOSH: PAC: Pen: PI: REACh: SARA: Sim-Dis: SP: TOM: VacRes: XAD-2:

ACKNOWLEDGMENTS

CONCLUSION

W

I

FUNDING

n summary, our data show that for temperatures lower than 200◦ C, the manufacturing process seems to have minimal impact on the qualitative and quantitative emission composition. For temperatures higher than 200◦ C, the presence of flux oil in bitumen seems to drive high molecular weight PACs into the emissions yielding an increase of 4 – 6 ring PACs. In all cases, there were no detectable levels of benzo[a]anthracene, benzofluoranthenes, benzo[a]pyrene, or dibenz[a,h]anthracene in the emissions for temperatures below 200◦ C.

= Gas chromatography / Flame ionization detector = Gas Chromatography-Mass Spectrometry = Gas chromatography/Time-of-flight-mass spectrometry = International Agency for Research on Cancer = Limit of detection = Mutagenicity index = National Institute for Occupational Safety and Health = Polycyclic aromatic compound = Penetration - used as a grading system to characterize consistency of bitumen = Penetration index = Registration, evaluation, authorization and restriction of chemical substances = Superfund Amendments and Reauthorization Act = Simulation distillated = Softening point = Total organic matter = Vacuum residue = polymeric sorbent for collection of emissions including hydrocarbons and PACs

T

e acknowledge the constructive comments of many colleagues.

his work was financially supported by Total Marketing & Services and Total Refining & Chemicals.

SUPPLEMNTAL MATERIAL

S

Supplemental data for this article can be accessed at tandfonline.com/uoeh. AIHA and ACGIH members may also access supplementary material at http://oeh.tandfonline.com/.

ACRONYMS AND ABBREVIATIONS = Asphalt Institute = American Society for Testing and Materials BB: = Blown bitumen BBU: = Blown bitumen unit BDL: = Below Detection limit Bp: = Boiling point BSF: = Benzene soluble fraction BURA: = Built-up roofing asphalt EN: = European standard EUROBITUME: = European Association Between Bitumen Producers, established in 1969; based in Brussels AI: ASTM:

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Effect of Temperature and Process on Quantity and Composition of Laboratory-generated Bitumen Emissions.

In this study we investigated the impact of temperature on emissions as related to various bitumen applications and processes used in commercial produ...
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