Journal of Occupational and Environmental Hygiene

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Airborne Exposures to Polycyclic Aromatic Compounds Among Workers in Asphalt Roofing Manufacturing Facilities David C. Trumbore, Linda V. Osborn, Kathleen A. Johnson & William E. Fayerweather To cite this article: David C. Trumbore, Linda V. Osborn, Kathleen A. Johnson & William E. Fayerweather (2015) Airborne Exposures to Polycyclic Aromatic Compounds Among Workers in Asphalt Roofing Manufacturing Facilities, Journal of Occupational and Environmental Hygiene, 12:8, 564-576, DOI: 10.1080/15459624.2015.1022651 To link to this article: http://dx.doi.org/10.1080/15459624.2015.1022651

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Journal of Occupational and Environmental Hygiene, 12: 564–576 ISSN: 1545-9624 print / 1545-9632 online c 2015 JOEH, LLC Copyright  DOI: 10.1080/15459624.2015.1022651

Airborne Exposures to Polycyclic Aromatic Compounds Among Workers in Asphalt Roofing Manufacturing Facilities David C. Trumbore,1 Linda V. Osborn,2 Kathleen A. Johnson,3 and William E. Fayerweather3 1

Owens Corning, Summit, Illinois Heritage Research Group, Indianapolis, Indiana 3 Owens Corning, Toledo, Ohio

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We studied exposure of 151 workers to polycyclic aromatic compounds and asphalt emissions during the manufacturing of asphalt roofing products—including 64 workers from 10 asphalt plants producing oxidized, straight-run, cutback, and wax- or polymer-modified asphalts, and 87 workers from 11 roofing plants producing asphalt shingles and granulated roll roofing. The facilities were located throughout the United States and used asphalt from many refiners and crude oils. This article helps fill a gap in exposure data for asphalt roofing manufacturing workers by using a fluorescence technique that targets biologically active 4–6 ring polycyclic aromatic compounds and is strongly correlated with carcinogenic activity in animal studies. Worker exposures to polycyclic aromatic compounds were compared between manufacturing plants, at different temperatures and using different raw materials, and to important external benchmarks. High levels of fine limestone particulate in the plant air during roofing manufacturing increased polycyclic aromatic compound exposure, resulting in the hypothesis that the particulate brought adsorbed polycyclic aromatic compounds to the worker breathing zone. Elevated asphalt temperatures increased exposures during the pouring of asphalt. Co-exposures in these workplaces which act as confounders for both the measurement of total organic matter and fluorescence were detected and their influence discussed. Exposures to polycyclic aromatic compounds in asphalt roofing manufacturing facilities were lower than or similar to those reported in hot-mix paving application studies, and much below those reported in studies of hot application of built-up roofing asphalt. These relatively low exposures in manufacturing are primarily attributed to air emission controls in the facilities, and the relatively moderate temperatures, compared to built-up roofing, used in these facilities for oxidized asphalt. The exposure to polycyclic aromatic compounds was a very small part of the overall worker exposure to asphalt fume, on average less than 0.07% of the benzene-soluble fraction. Measurements of benzene-soluble fraction were uniformly below the American Conference of Governmental Industrial Hygienists’ Threshold Limit Value for asphalt fume. Keywords

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asphalt, asphalt fume, fluorescence, polycyclic aromatic compounds, roofing manufacturing, worker exposure

Address correspondence to David. C. Trumbore, 4618 N. Dover St., Chicago, IL 60640; e-mail: [email protected] Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/uoeh.

INTRODUCTION

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sphalt, or bitumen as it is called in Europe, is used extensively in the roofing and paving industry; in fact most roads and residential roofs in the United States (U.S.) are made using asphalt.(1,2) Asphalt is the residuum recovered when petroleum is refined and, as such, is a complex mixture of hydrocarbons, including a small amount of polycyclic aromatic compounds (PACs).(3) PACs include parent polycyclic aromatic hydrocarbons (PAHs) as well as alkylated PAHs and heterocyclic derivatives where one or more of the carbon atoms in the benzenoid rings have been replaced by a heteroatom of nitrogen, oxygen, or sulfur. Asphalt can be used as produced without modification, in which case it is called straight-run asphalt, or it can be modified by a number of processes and materials. Asphalt can be modified by blowing air through it at high temperatures to produce a material, known as oxidized asphalt, that is widely used for built-up roofing and asphalt shingles.(1) It can be emulsified with water or mixed with solvents to make materials that can be applied at ambient temperatures, or it can be mixed with waxes or polymers to enhance materials used in paving and roofing.(3) U.S. asphalt roofing is manufactured in approximately 100 facilities employing 3000–4000 workers, while in Europe there are about 120 plants employing about 3000 workers.(1) Asphalt and asphalt emissions have been studied for decades as to their impact on human health. The American Conference of Governmental Industrial Hygienists (ACGIH) in 2001 found asphalt fume to be not classifiable as a human carcinogen and recommended a threshold limit value

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(TLV-TWA) for occupational exposure of 0.5 mg/m3 as benzene-soluble inhalable aerosol to minimize acute eye and respiratory tract irritation.(4) Also in 2001, the National Institute for Occupational Safety and Health (NIOSH) judged roofing asphalt fumes to be a potential occupational carcinogen, but found insufficient evidence that exposure to paving asphalt fumes was a potential occupational carcinogen. They continued their Recommended Exposure Limit (REL) of 5 mg/m3 (15 min sample) based on total particulate.(5) Recently, the International Agency for Research on Cancer (IARC) concluded that: (1) occupational exposure to oxidized asphalt and its emissions during roofing was a probable human carcinogen (IARC 2A); and (2) occupational exposure to straight-run asphalt and its emissions during paving was a possible human carcinogen (IARC 2B).(6,7) It should be noted that the term “asphalt fume” is used in the literature both in its strict definition as a condensed vapor,(4) but also is commonly used in a broader sense to indicate all airborne material emitted from heated asphalt.(3) In this article, we use the term “fume” when referring to benzene soluble fraction of total particulate (BSF) results or when referencing literature that specifically used the term; and we use the term “emission” to indicate all the airborne material coming from asphalt (particles, fume, vapor, and gas) and when referring to total organic matter (TOM) results. Many asphalt-based roofing products and some paving products are applied in the field at ambient temperature, with de minimis airborne exposure from asphalt.(1,2) These include: asphalt shingles; asphalt felt underlayment; peel and stick underlayment; asphalt cements; some modified bitumen membranes; asphalt coatings and adhesives in the roofing industry; and emulsions and cutback asphalt in the paving industry. The only significant worker exposure to asphalt emissions with these products is encountered during their manufacture. In the case of the manufacture of asphalt roofing, extensive databases of worker exposures to asphalt fumes using measurements of total particulate (TP) and benzene-soluble fraction (BSF) have been published.(8,9) It is widely recognized that the biologically active components of asphalt emissions that could cause cancer are the 4–6 ring PACs present in small amounts in the asphalt.(5,10,11,12) Data exist in the literature on exposure to PACs in hot-mix asphalt paving application and in hot application of asphalt on roofs.(13–17) These studies measured some specific PAHs in the worker breathing zone samples as surrogates for the exposure to all PACs of interest, and/or made measurements that are sensitive to the total amount of PACs in the emissions. An example of the latter technique is the fluorescence method (FL-PAC) described by Osborn(10) that optimizes the response to the PACs present in the fume condensate fractions that were found by NIOSH to be most potent in causing animal tumors in skin painting studies.(18) These fume condensate fractions and other asphalt emissions have also been characterized using the Modified Ames Assay.(5,10,11,19) Correlations of individual asphalt emission study results have been reported between both

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of these measures and carcinogenic index per gram(10,11,20) and data from the relevant dermal cancer assay studies have been aggregated by Trumbore.(12) In contrast to paving and hot roofing application, the literature is largely silent on the inhalation exposure to PACs in the manufacture of asphalt roofing products.(1,7) The current study was designed to help fill this void by using the FL-PAC technique(10) to examine worker exposure to relevant PACs in Owens Corning’s (OC) roofing manufacturing facilities producing asphalt shingles and granulated roll roofing, and their asphalt manufacturing facilities supplying the roofing industry with asphalts. Use of this technique allows comparison to recent data in the paving and roofing application sectors that used the same fluorescence method performed by the same laboratory.(14–17) METHODS Sampling Populations and Conditions The population studied in this paper included workers in 10 asphalt manufacturing facilities and 11 roofing manufacturing facilities owned by OC and located across the U.S. Measurements were taken over the period from May 2011 to September 2013. Sampling was focused on jobs with reasonable potential for asphalt fume exposure, i.e., office workers were not included in the surveys, for as close to full shift as possible, and if abnormal conditions were observed they were noted. These same OC facilities have been part of two previously published studies: (1) a case-control epidemiology study by Georgetown University that found no significant link between asphalt fume exposure and death from lung cancer or non malignant respiratory disease;(21) and (2) a study of worker exposure to asphalt fume, total particulate, and respirable crystalline silica over a period from 1977–2006 that shows a sharp reduction in asphalt fume exposures over time.(9) Because of the difference in time of year and geographic location of the facilities, sampling took place under widely varying ambient conditions. Asphalt plant exposures are outdoors and in these facilities the ambient temperatures varied from −12◦ C to 37◦ C, relative humidity from 36–85%, and wind speed from 0–8 km/h. Roofing plant exposures are indoors and the temperature varied from 14–38◦ C and the relative humidity from 19–80%. Process and material information were collected during the sampling. Particular note was made of asphalt temperatures, production materials used during the testing period, and non asphaltic organic materials used in the facilities that could be co-exposures contributing to, and confounding the interpretation of, the worker exposure measurements. Samples of the potential co-exposure materials were taken for analysis by the same methods used to analyze TOM. Materials Used and Manufactured The OC asphalt manufacturing facilities produce a variety of asphalt products. They oxidize asphalt to make

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multiple products including coating used in the manufacture of asphalt shingles and roll roofing, built-up roofing asphalts (BURA), and high softening-point specialty asphalts. They blend straight-run asphalts (both vacuum distilled and in some cases propane deasphalted residue) both for input to the oxidizers and to meet product specifications. Some produce polymer- or wax-modified asphalts, and some make cutback asphalt by blending solvents with asphalt. Products are shipped hot in trucks or poured into cartons for cooling prior to shipping. The occupational hygiene measurements were taken on: (1) operators working across the entire facility; (2) workers pouring hot asphalt products into cartons; (3) laboratory technicians testing products; and (4) maintenance workers. Workers pouring asphalt were exposed to oxidized asphalt. Other workers were exposed to both oxidized and straight-run asphalts. The roofing manufacturing facilities all produce asphalt shingles and, in some cases, the same process equipment is used to make granulated roll roofing. The hot end process and thus exposures are similar regardless of which product is being produced. These products are based on a glass-mat substrate that is coated with oxidized asphalt filled with limestone mineral filler, then surfaced with sand or limestone back dust that is applied to the back of the sheet after the coating step to act as a release agent, and then colored rock granules are added to the top of the sheet. Occupational hygiene measurements were taken on workers at different stages of the manufacturing process (coater, cooling section, laminator operators, etc.) and on maintenance workers. All workers were exposed to oxidized asphalt. In some facilities they were also exposed to straight-run asphalts used to make adhesives applied during the process. The term “asphalt roofing products” in this article refers to both the asphalt manufactured to be used in making roofing products, as well as the roofing products themselves. The source of asphalt in these facilities varied widely. In all, more than twenty different refineries provided the asphalt used in these facilities and at least 20 different crude oils were used to make the asphalts, with most of the asphalts being made from a blend of crude oils. Sampling Methods Total Particulates and Benzene-Soluble Fraction Personal samples of airborne asphalt fumes to determine TP and BSF were collected in the worker’s breathing zone using calibrated personal sampling pumps equipped with preweighed 37mm poly-tetrafluoroethylene (PTFE) membrane filter laminated to PTFE (2 µm pore size; Cat. No. 22527-07, SKC, Inc., Eighty Four, PA). Collection and sample management was performed by EnSafe, Inc. (Cincinnati, OH). Samples were analyzed by Galson Laboratories(East Syracuse, NY), according to NIOSH Method 0500 for total particulate and NIOSH Method 5042 for asphalt fumes.(22,23) Sampling times ranged from 282–656 min with a median of 453 min.

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Total Organic Matter and Fluorescence To measure the exposure to total organic matter (TOM) and to PACs as measured by fluorescence (FL-PAC) workers wore an additional sorbent tube sampler composed of XAD-2 and charcoal (150 mg XAD-2 followed by 50 mg activated charcoal; Cat. No. CPM032509-001, SKC, Inc. Eighty Four, PA). A 1-in piece of Teflon tubing (Cat. No. 14-176-272, Fischer Scientific, Pittsburgh, PA), dichloromethane rinsed, was added to the end of the tube, once broken, to protect workers from the sharp edges. Care was taken to break the inlet end of each tube to 4-mm to equal the inlet size of the NIOSH sampler. Set to a flow rate of 2.0 +/− 0.2 L/min, the pumps were calibrated pre-shift and re-measured post-shift. Typically, one background sample was collected each day, positioned in an area not directly affected by asphalt emissions. A field blank sampling tube was opened and closed on each day in the field. Field blanks were analyzed with each sample set and any detectable results subtracted from all samples within that set. The sorbent tube was eluted with 5 mL dichloromethane (HPLC Grade OmniSolv High Purity, Cat. No. DX0831–1, EMD, Gibbstown, NJ) with charcoal positioned at the top. On two occasions, due to sampling logistics, the filter used for TP and BSF using NIOSH Method 5042 was collected in series with the XAD-2 and charcoal sorbent tube. This was done in Plants A and the second trip to Plant I (See supplemental tables), and in these cases air was passed through the filter first, then XAD-2 + charcoal and after sampling Galson Laboratories performed NIOSH Method 5042,(23) and then sent the remaining BSF extract to Heritage Research Group (HRG) (Indianapolis, Indiana) for combination with the sorbent tube eluent prior to TOM and fluorescence analysis. Equivalence of these techniques for monitoring TOM has been established by HRG.(24) The available comparisons from this study support that conclusion. Plant I had a geometric mean FL-PAC exposure of 0.014 µg/m3 with the combined filters vs. 0.012 µg/m3 without. Plant A had geometric means for FL-PAC exposure of 0.03 µg/m3 for roofing vs. an overall 0.05 µg/m3 for the entire study, and on the asphalt side both Plant A and the entire study had FL-PAC exposures of 0.04 µg/m3. Gas chromatography with flame ionization detection (GC/FID) was used to quantify the TOM using a modified SW846–8015B method(25) previously described.(26) This test allowed quantification of and chromatographic profiling of the exposures, providing insight into the composition. To assist in co-exposure investigation discussed below the GC/FID analysis was completed on not only asphalt emission samples but also on other organic materials used in the facilities. Quantification of the TOM was achieved by comparison to a five-point calibration curve using the most similar standard(s) to the pattern detected from the occupational hygiene exposure. All TOM extracts from air samples were analyzed using this technique, providing valuable qualitative information relative to the source and nature of the exposures.

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FIGURE 1. Left: GC/FID Chromatogram of the asphalt operator in Asphalt Plant D, 11-17-11. This pattern is similar to the mineral spirit sample taken from the same OC site (right). Trace levels of components possibly from asphalt-fume exposures may be masked by the mineral spirits. The primary components were tentatively identified as D-Limonene (another cleaning solvent commonly used), and Undecane. Right: GC/FID Chromatogram of a mineral spirit sample taken from the OC asphalt plant laboratory during this survey. Undecane is the largest peak. For quantitation of asphalt emissions, the front peaks in the rectangle that are not a part of the mineral spirits standard were compared to the kerosene calibration standards using the same peak range. It is clear for this worker’s exposure, that mineral spirits is the primary exposure, with the possibility of low levels of asphalt emissions exposure.

FL-PACs measurements were performed using a Perkin Elmer Luminescence Spectrometer LS50B following the fluorescence test protocol outlined by Osborn.(10) This is a screening test designed to optimize response to a subset within asphalt emissions, optically isolating the 4–6 ring PACs that may themselves contain a subset of compounds that are potentially carcinogenic. Since emission units per gram (EU/g) values are being compared to previously published data, the emission units were multiplied by the ratio of current response factor/reference response factor to normalize the results using a diphenylanthracene (DPA) 5-point calibration curve. For many of the roofing samples, filtration was required due to particulates in the extracts. FL-PAC results were calculated in two ways in this study: fluorescence concentrations in air (µg/m3 as DPA) and fluorescence response per gram of TOM in one mL (EU/g). The former is referred to as FL-PAC exposure and the latter is referred to as FL-PAC potency in this paper. An average limit of detection (LOD) for the FL-PAC exposure data of 0.005 µg/m3 was determined for the study as three standard deviations above the gross blank signal. Any values below this were reported as below the detection

limit (BDL) at 0.005 µg/m3 as DPA. Because the FL-PAC potency value divides the fluorescence signal by the amount of organic matter collected as determined by the TOM, the GC/FID results needed to be above the limit of detection to report this number. Consequently, if the GC/FID result for TOM was < 0.0005 grams, FL-PAC potency was indicated as NR (not-reportable). Sampling times for TOM and FL-PACs ranged from 49–658 min with a median of 437 minutes, a first quartile of 402 min, and only 3 values less than 200 min. All TOM and FL-PAC analyses were performed by HRG, Indianapolis. Co-Exposure Analysis As described above, TOM extracts from air sampling were analyzed using GC/FID that, when compared to standards, not only provided the total amount of organic material but also provided insight as to the chemistry of the emissions, that aided in the determination of exposure source. Figure 1 shows an example of a common co-exposure found using GC/FID; mineral spirits which was widely used as a solvent in these facilities. TOM was quantified as described above. However,

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FIGURE 2. Left: GC/FID Chromatogram of Cooling Section Operator 1 in Plant D 11/15/11. No asphalt-emission related pattern was apparent although FL-PAC potency was elevated. The primary components were identified using GC/MS as Nonane, alpha-Pinene, beta-Pinene, decamethylcyclopentasiloxane and 4-ethyloctane. The areas from these labeled individual components were subtracted from the area used to quantify asphalt fumes and the result was BDL. Right: This is a worker sample that contains an asphalt emission pattern that is free of detectable confounders or co-exposures. None of the peaks identified in the left chromatogram were identified in the right chromatogram.

to estimate the actual level of exposure to AFOM compared to TOM we use the peaks shown in the rectangle, which were absent in the mineral spirits sample taken at the plant. This area was then compared to the kerosene calibration standards using the same retention time range. In some cases, BSF extracts were concentrated, then reanalyzed to look at the chemistry of those emissions. Selected TOM samples were also analyzed by gas chromatography/mass spectrometry (GC/MS) using a program similar to EPA SW-8468270C (28) to identify some of the prominent individual non-asphalt related peaks to assist in the determination of co-exposure source. This GC/MS identification was accomplished by library search against the NIST library. Figure 2 shows an example of individual peaks atypical of asphalt emissions found in a worker sample. These were identified by GC/MS and labeled accordingly. This chromatogram shows little indication of asphalt exposure. The area from these labeled individual components was subtracted from the area used to quantify asphalt emissions in order to estimate the level of exposure from asphalt. Our investigation of the chemistry of the emissions revealed if the exposure were from asphalt emissions, from another source, or more commonly, a combination. This was helpful since the BSF is a gravimetric, non-descript test. Previous studies have described the use of elution profiles and GC/MS

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to identify the source of non-asphalt organic material in the samples.(26,27) As a result, the non-asphalt sources of airborne organic matter were subtracted from the TOM to estimate a value reported here as asphalt fume organic matter (AFOM), solely to provide an indication of the level of organic coexposures. This adjustment only impacted the TOM analysis. FL-PAC measurements were not adjusted and are reported as measured. Data Analysis Worker exposure data were tested for normality using the Anderson-Darling (AD) test and were found to be highly nonnormal (all p values 0.2) and is detectable in nearly all cases. The FL-PAC exposure was a very small part of the overall asphalt-related worker exposure, being on average 0.04% (asphalt manufacturing) to 0.065% (roofing manufacturing) of the BSF, and 0.009% (asphalt) to 0.014% (roofing) of the AFOM. In both roofing and asphalt manufacturing there were three outliers. In roofing manufacturing the three were: a shingle cutter operator, a coater operator, and a maintenance worker, all in different facilities. Only the coater operator exposure appeared to be from asphalt; GC/FID profiles indicated the shingle cutter exposure was probably from d-limonene present in a cleaning material and the maintenance worker exposure was probably from lubricating oil. In asphalt manufacturing the

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FIGURE 3. Asphalt manufacturing worker FL-PAC exposure. Notes: FL-PAC is exposure to polycyclic aromatic compounds by fluorescence. Boxplot Key: the box contains the lower quartile (Q1), median, and upper quartile (Q3), the upper whisker extends to an upper limit of Q3 + 1.5 (Q3–Q1), that is commonly used to define outliers; and the lower whisker extends to a similar lower limit. Finally, the circles indicate outliers.

outliers were: an operator, a pourer of hot asphalt into cartons, and a lab technician—again across three different facilities. GC/FID profiles indicated the lab technician’s exposure was probably from parts washer solvent, not asphalt.

FL-PAC potency was lower in asphalt manufacturing than in roofing manufacturing (p < 0.002 Kruskal-Wallis and Mood’s median tests). Of the four outliers observed in asphalt facilities, three were from high temperature pouring of specialty

FIGURE 4. Roofing manufacturing worker FL-PAC potency. Notes: FL-PAC, polycyclic aromatic compounds by fluorescence. Boxplot Key: the box contains the lower quartile (Q1), median, and upper quartile (Q3), the upper whisker extends to an upper limit of Q3 + 1.5 (Q3–Q1), that is commonly used to define outliers; and the lower whisker extends to a similar lower limit. Finally, the circles indicate outliers.

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TABLE II. Test Results from Roofing Plant Using Fine Limestone Back Dust

Conditions Asphalt Source Coater Temperature Back Dust Silo Dust Control System Date Ambient Conditions

Original Test

Retest

55% Asphalt A 45% Asphalt B 193 to 198◦ C Fine Particulate Segregation Partially Plugged October 25 to 27, 2011 19–21◦ C; 37–55% Relative Humidity

50% Asphalt A 50% Asphalt B 193 to 196◦ C Normal Operation Normal Operation January 30, 2012 17◦ C; 31% Relative Humidity

10

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Number of Workers Monitored Exposures TP (mg/m3) BSF (mg/m3) FL-PAC Exposure (µg/m3) FL-PAC Potency (EU/g)

Geometric Mean 3.96 0.14 0.09 75

Maximum Value 30.00 0.44 0.22 197

Geometric Mean 2.00 0.07 0.04 N/AA

Maximum Value 3.00 0.07 0.10 28

Notes:AOnly one value so mean not reported. TP, total particulate; BSF, benzene soluble fraction; FL-PAC, polycyclic aromatic compounds by fluorescence.

asphalt and one was from a maintenance worker. The elevated pouring exposures appeared to be asphalt-related, but the maintenance worker exposure did not. All of the asphalt facility outliers were below 100 EU/g, a value roughly midway between the highest field generated hot mix paving emissions value and the lowest field generated BURA emissions value in a study of both workplace settings.(16) By contrast seven roofing manufacturing FL-PAC potency values were above the 100 EU/g value. Of these seven, GC/FID profiles indicated two were probably from non-asphalt exposure, but the remaining five were asphalt related and were from a single facility. The concentration of all high asphalt-related FL-PAC potency values in a single facility warranted further investigation. Impact of Particulate The concentration of asphalt-related FL-PAC potency values above 100 EU/g in one of the 11 roofing manufacturing facilities coincided with the observation that dust levels in that facility were unusually high during the sampling. The high dust levels were due to three factors: (1) the limestone back dust used as a release agent on the back of the sheet, that is finer than sand back dusts used in all the other roofing facilities; (2) a process malfunction that caused segregation in the back dust silo supplying the roofing shingle line, resulting in even finer material being applied than normal; and (3) a partially plugged dust-collection system. Follow-up testing was performed in the same facility after the two process issues were fixed. The conditions and results of these two testing periods are compared in Table II. TP levels decreased once the process malfunctions were fixed (p < 0.05 with both Kruskal-Wallis and Mood Median one-tail tests). With essentially the same asphalt, coater temperature, and ambient

conditions, the BSF and FL-PAC exposure and potency results were dramatically lower once the limestone particulate in the air was reduced (BSF p < 0.001 Kruskal-Wallis and Mood Median one-tail tests; FL-PAC exposure p = 0.014 Mood Median one-tail test). During the retest period a sampling tube inadvertently was dipped into accumulated limestone fines and then sampled for a short period. Analysis showed that higher molecular weight asphalt emission components were indeed adsorbed on the limestone particles. Some roofing manufacturing facilities in the study that used sand as a back dust had higher TP values for some workers but did not show increases in FL-PAC or BSF values when TP was elevated. These observations led to the hypothesis that elevated levels of fine limestone particulate in the plant air can trap and carry high molecular weight PACs to the worker breathing zone. Impact of Temperature Temperature is important to asphalt emissions generation. In this study there were two job categories that saw consistent elevated asphalt temperature throughout their job function: (1) workers pouring asphalt into cartons in asphalt plants; and (2) workers in the coater area in roofing plants. A significant correlation (r2 = 0.5, p < 0.001) between worker FL-PAC exposure and temperature while pouring cartons is shown in Figure 5. The range of asphalt temperature studied was quite large, 149–257◦ C. On the other hand, no trend between FLPAC data and temperature was observed in the roofing coater area where the range of temperature was only 184–218◦ C. Any effect over this small temperature difference could have been overcome by the large effect of high particulate levels in the one facility, and the variability in effectiveness of emissions control systems.

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FIGURE 5. FL-PAC exposure vs. pouring temperature. Notes: FL-PAC, polycyclic aromatic compounds by fluorescence. r2 = 0.50, p value = 0.000, residuals normally distributed.

Correlation between PAC exposure and BSF Given that BSF measurement is more common than is PAC exposure measurement it is of interest to explore how well the two measures correlate. Taking all the data as a whole, a least squares regression analysis suffered from residuals not being normally distributed. However, if only the 15 BSF results that were above the LOD were considered, all had FL-PAC values above the LOD and a regression of FL-PAC vs. BSF was significant (p = 0.013), the r-squared value was 39%, and the residuals were normally distributed (AD = 0.449, p = 0.238). DISCUSSION

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s NIOSH pointed out in their Health Hazard Review, no occupational exposure limits have been established for any measure of PACs associated with asphalt fumes.(5) In order to judge the potential impact of the FL-PAC exposures measured in this study some other comparison is needed. It is therefore useful to compare these worker exposure measurements to industry benchmarks that have been assessed as to their potential hazard from asphalt and PAC exposure. Two asphalt exposures have been studied in great detail and can serve as these benchmarks: (1) exposure during hot-mix paving and (2) exposure during hot application of built-up roofing asphalt. Both have been the subject of significant epidemiology research and both have been studied in animal cancer assay studies. Looking at epidemiology literature, both IARC(6,7) and NIOSH(5) judged the link between cancer and field exposure

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to asphalt fumes or emissions during hot mix paving to be inadequate. NIOSH relied heavily on the Partanen and Boffetta meta-analysis that did not find evidence of a lung cancer risk among pavers.(31) IARC also had access to their own extensive nested case-control study that concluded there was no suggestion of an increase in lung cancer risk with various metrics of emission exposure during asphalt use, most of which was in paving.(32) On the animal study side, paving asphalt emissions matched to the chemistry of worker fumes during hot-mix paving were collected in separate studies in Europe and the U.S. Emissions from a paving asphalt made by mixing oxidized asphalt with straight-run asphalt did not show any tumor formation in a two year European inhalation study.(33) In the U.S. study, emissions from a commonly used paving asphalt did not show any tumor formation in a two-year skin painting study.(20) Additionally, the Modified Ames Assay, a measure of mutagenicity, showed values for the field paving emissions(16) that were below a well-established safe threshold level for petroleum products.(34) Both IARC(6,7) and NIOSH(5) judged that the animal cancer assay data for paving fume or emission exposure did not show any health hazard effects. IARC did give a possibly carcinogenic rating (2B) to paving based on mechanistic considerations. While asphalt is used in roofing in many different products leading to different types of exposure,(1) health studies have focused on the hot application of BURA asphalt in the field—either workers applying the asphalt or animal cancer assay studies of emissions generated by that asphalt at typical BURA application temperatures. In contrast to paving, both IARC(6,7) and NIOSH(5) rated roofing fume or emission

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TABLE III. Comparison of Worker BSF and FL-PAC Exposures to Benchmark Studies Roofing and Asphalt Manufacturing Referenced Study

Current Study

Workers in Cohort OC Roofing OC Asphalt

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BSF Exposure (mg/m3) Number Geometric Mean Maximum

Hot Mix Paving Application NAPA Study Data(14,17) All

DieselA Bio-dieselA

Hot Roofing Application

Kriech 2007(16) All

Kriech 2004(15)

Kriech 2007(16)

Kettle Roof Top KettleB Roof TopB

83 0.08 0.44

58 0.10 0.27

144 0.04C 0.97

109 0.04 0.97

35 0.03 0.28

12 0.12 N/A

10 0.65 9.63

32 0.20 1.02

4 0.75 1.50

12 0.39 0.95

FL-PAC Exposure (µg/m3) Number 87 Geometric Mean 0.05 Maximum 0.23

64 0.04 0.28

144 0.13 2.5

107 0.14 2.5

36 0.11 0.7

N/A

10 1.51D 8.5D

32 0.53D 2.2D

4 1.78 3.5

12 0.75E >0.87E

FL-PAC Potency (EU/g) Number 36 Geometric Mean 35 Maximum 237

46 10 97

N/A

107 19 179

36 29 94

12 51E >79E

4 196 328

12 147E >202E

N/A

Notes:ASome values taken from Osborn 2013 JOEH Supplemental Tables, or calculated from values in those tables. BPublication contained BSF and FL-PAC potency averages. Individual data, where available, and FL-PAC exposure data provided by authors. CAuthors also modeled FL-PAC exposures at different application temperatures—0.21µg/m3 at 149◦ C and 0.09 µg/m3 at 127◦ C. DOriginal publication used a different calculation scheme. The author’s provided recalculated values using the same technique as in this paper EUsed worker composite numbers to calculate geometric mean and max. Equal n for each data set gives accurate means but max is lower limit. BSF, benzene soluble fraction; FL-PAC, polycyclic aromatic compounds by fluorescence; N/A, not available.

exposure a potential or probable human cancer hazard. For human data both used the Partanen and Boffetta meta-analysis(31) that indicated a possible link between roofing work and lung cancer, although confounding with coal tar exposure and other

FIGURE 6.

agents was indicated as another possible explanation. Coal-tar confounding has since been confirmed to be a viable explanation of the results.(35) Also, in contrast to paving, both IARC(6,7) and NIOSH(5) found BURA fumes or emissions to be carcino-

Comparison of FL-PAC exposure across industry sectors. Notes: FL-PAC, polycyclic aromatic compounds by fluorescence.

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FIGURE 7.

Comparison of FL-PAC potency across industry sectors. Notes: FL-PAC, polycyclic aromatic compounds by fluorescence.

genic to animals in skin-painting studies. Both referenced work conducted at NIOSH on laboratory-generated emissions,(18,36) while IARC also had access to studies conducted on emissions matched to the chemistry of airborne material that BURA workers were exposed to in the field that showed a weak tumor response,(20) and that showed that the fume acted as a genotoxic initiator.(37) Table III and Figures 6 and 7 present comparisons of the FL-PAC exposure, FL-PAC potency, and BSF, measured in the current study to values in published studies of hot mix paving and hot BURA workers. These published studies are: (1) a large paving study that reported both overall results and also lower exposure scenarios;(14,17) (2) a BURA work practices study(15) that reported FL-PAC exposure; and (3) a study that generated field matched emissions(16) that reported limited exposure data in preparation for both paving and BURA cancer assays.(20) The large paving study and the cancer assay prework both used identical methodology to the current study allowing for direct comparison of reported values. The BURA work practices study reported FL-PAC exposure after both a cyanopropyl cleanup and an adjustment of the fluorescence signal to subtract 2–3 ring PACs. The authors of the work practices and cancer assay pre-work study have provided the unmodified data from the former to provide a direct comparison to this work, and more detailed exposure numbers from the latter to give more specific detail to the comparison and to provide FL-PAC exposure as well as potency. The additional data are provided in supplemental tables. (L.V. Osborn, Heritage Research Group, February and May 2014). These comparisons show FL-PAC exposures in both OC roofing manufacturing and asphalt manufacturing facilities 574

to be quite low. Compared to paving they were not only less than half the geometric mean from the total study, but lower than either of the two low exposure conditions: (1) the 127◦ C application temperature results calculated from a model and (2) the biodiesel data set. Both the paving and the OC manufacturing numbers were much lower than that seen in BURA application—with the numbers in manufacturing more than an order of magnitude lower. Because the OC roofing manufacturing and asphalt manufacturing FL-PAC exposure data were not significantly different they were combined for statistical comparisons with the paving and BURA benchmarks. Statistically, the OC data were significantly lower than all benchmark comparisons where individual values were available (all paving, diesel paving, biodiesel paving, 2004 BURA kettle, 2004 BURA rooftop) with Kruskal-Wallis and Mood’s median p values ≤ 0.001. Comparisons of FL-PAC potency showed OC values to be similar to those in paving, and both manufacturing and paving to be much lower than BURA application. Statistical analysis was not possible for potency since individual paving values were not available, and since the BURA rooftop numbers were averages with no access to the individual values. Note that all FL-PAC data from the current study were included in these comparisons regardless of the analysis of outliers. BSF levels measured in the current study were all well below the ACGIH TLV, similar to those measured in the paving study(14) and in previous studies of asphalt roofing manufacturing,(8,9) and they were lower than those reported for BURA application.(1,15,16) The low FL-PAC and BSF numbers in asphalt roofing manufacturing are consistent with the use of air pollution

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emission controls on these stationary sources of emissions and the fact that temperatures used in these facilities for oxidized asphalt are significantly lower than those commonly used in BURA, both at the kettle and on the roof. The impact of oxidization on lowering PAC content of asphalt(12,38) may also contribute to the low values. The focus of this study was the exposure to airborne PACs present in asphalt emissions. It did not include separate dermal sampling techniques. In the OC manufacturing facilities, the use of mandated personal protective equipment greatly limits the exposure of skin to asphalt or to condensed asphalt fume. The measure of airborne emissions detects all the inhalation exposure and would be an indicator of the potential for dermal exposure from condensed fumes. One limitation of this study is that it only includes samples from one company’s manufacturing facilities. Others may use different materials, process conditions (e.g., temperature), and may have different fume collection systems, all of which may affect results. Another is that it was not designed in a way to allow detailed analysis of multiple days of exposure of the same employee performing the same task, although it did allow multiple analyses of different employees performing the same or similar tasks. CONCLUSIONS

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he study reported here helps fill a gap in PAC exposure data during the manufacture of asphalt roofing products. The findings include the following. • The FL-PAC exposure in asphalt roofing manufacturing was a very small part of the overall worker exposure to asphalt emissions, on average less than 0.07% of BSF and less than 0.02% of AFOM. • Mean FL-PAC exposures in asphalt roofing manufacturing are lower than the lowest exposure conditions from available hot-mix paving studies. • Mean FL-PAC potencies in asphalt roofing manufacturing are similar to that seen in available data from hot-mix paving. • FL-PAC exposures and potencies in asphalt roofing manufacturing are much lower than is seen in application of hot BURA on roofs. • High levels of fine limestone particulate in roofing plant air may be a factor raising measurements of FL-PAC (and BSF) exposure. • Elevated asphalt pouring temperature can significantly impact exposures to FL-PACs. • FL-PAC exposure and potency appear to be confounded in some cases in these manufacturing facilities by co-exposure to airborne emissions from other organic materials used in the manufacturing process. Notable among these are d-limonene (present in cleaning materials), solvents, and lubricating sprays. • TOM is helpful to assess the existence of confounding co-exposures, but is a poor indicator of asphalt emission

exposure in these manufacturing facilities because so much of the signal is from co-exposure to solvents, lubricants, and cleaning liquids rather than asphalt. ACKNOWLEDGMENTS

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he assistance of Ensafe, Inc. in performing occupational hygiene sampling for asphalt fume exposures is appreciated as is the cooperation and assistance of manufacturing personnel in the facilities monitored. The Asphalt Roofing Environmental Council, composed of the Asphalt Institute, the Asphalt Roofing Manufacturers Association, and the National Roofing Contractors Association, provided access to unpublished data from previous studies that made the comparisons to benchmarks more robust. FUNDING

T

his project was funded by Owens Corning. The findings and conclusions are those of the authors alone and do not necessarily represent the interpretations of Owens Corning. SUPPLEMENTAL MATERIALS

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upplemental 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/. REFERENCES 1. Asphalt Roofing Manufacturers Association (ARMA), Bitumen Waterproofing Manufacturers Association, National Roofing Contractors Association, and the Roof Coatings Manufacturers Association: The Bitumen Roofing Industry—a Global Perspective: Production, Use, Properties, Specifications and Occupational Exposure, Second Edition. 2011. Free copy available at: http://www.asphaltroofing.org/get-yourcopy-bitumen-roofing-industry-global-perspective 2. National Asphalt Pavement Association (NAPA), European Asphalt Pavement Association: The Asphalt Paving Industry—A Global Perspective: Production, Use, Properties, and Occupation Exposure Reduction Technologies and Trends, third edition. 2011 Free copy available at: at: http://store.asphaltpavement.org/index.php?productID=725 3. Asphalt Institute (AI), Eurobitume: The Bitumen Industry—a Global Perspective, Production, Chemistry, Use, Specification, and Occupational Exposure, second edition. No. 230 (IS-230). 2011. Available at: https:// mxo.asphaltinstitute.org/webapps/displayItem.htm?acctItemId=286 4. American Conference of Governmental Industrial Hygienists (ACGIHR ): Asphalt (Bitumen) Fumes, Cincinnati Ohio: ACGIH, 2001. 5. National Institute for Occupational Safety and Health (NIOSH): NIOSH Hazard Review: Health Effects of Occupational Exposure to Asphalt. Cincinnati, OH: DHHS (NIOSH) Publication No. 2001–110. 2001. 6. Lauby-Secretan, B., R. Baan, Y. Grosse, et al., on behalf of the WHO International Agency for Research for Cancer Monograph Working Group: Bitumen and bitumen emissions, and some heterocyclic polycyclic aromatic hydrocarbons. Lancet 12:1190–1191 (2011). 7. IARC Monograph: Volume 103, Bitumen and Bitumen Emissions, and some N- and S- Heterocyclic Polycyclic Aromatic Hydrocarbons, available free at http://monographs.iarc.fr/ENG/Monographs/vol103/index.php.

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8. Axten, C.W., W. Fayerweather, D. Trumbore, D. Mueller, and A. Sampson: Asphalt fume exposure levels in North American asphalt production and roofing manufacturing operations. J. Occup. Environ. Hyg. 9:1–13 (2012). 9. Fayerweather, W.E., D.C. Trumbore, K.A. Johnson, R.W. Niebo, and L.D. Maxim: Quantitative exposure matrix for asphalt fume, total particulate, and respirable crystalline silica among roofing and asphalt manufacturing workers. Inhal. Toxicol. 23(11):668–679 (2011). 10. Osborn, L.V., J.T. Kurek, A.J. Kriech, and F.M. Fehsenfeld: Luminescence spectroscopy as a screening tool for the potential carcinogenicity of asphalt fumes. J. Environ. Monit. 3:185–190 (2001). 11. Kriech, A.J., J.T. Kurek, L.V. Osborn, G.R. Blackburn, and F.M. Fehsenfeld: Bio-directed fractionation of laboratory-generated asphalt fumes: relationship between composition and carcinogenicity. Polycycl. Aromat. Cmpd. 14&15:189–199 (1999). 12. Trumbore, D., L. Osborn, G. Blackburn, R. Niebo, A. Kriech, and L.D. Maxim: Effect of oxidation and extent of oxidation on biologically active PACs in asphalt products. Inhal. Toxicol. 23(12):745–761 (2011). 13. Kriech, A.J., J.T. Kurek, H.L. Wissel, L.V. Osborn, and G.R. Blackburn: Evaluation of worker exposure to asphalt paving fumes using traditional and nontraditional techniques. Am. Ind. Hyg. Assoc. J. 63(5):628–635 (2002). 14. Cavallari, J.M., L.V. Osborn, J.E. Snawder, et al.: Predictors of airborne exposures to polycyclic aromatic compounds and total organic matter among hot-mix asphalt paving workers and influence of work conditions and practice. Ann. Occup. Hyg. 56(2):138–147 (2012). 15. Kriech, A.J., L.V. Osborn, D. Trumbore, J.T. Kurek, H.L. Wissel, and K. Rosinski: Evaluation of worker exposure to asphalt roofing fumes: influence of work practices and materials. J. Occup. Environ. Hyg. 1:88–98 (2004). 16. Kriech, A.J., L.V. Osborn, H.L. Wissel, A.P. Redman, L.A. Smith, and T.E. Dobbs: Generation of Bitumen Fumes Using Two Fume Generation Protocols and Comparison to Worker Industrial Hygiene Exposures. J. Occup. Environ. Hyg. 4(S1):6–19 (2007). 17. Osborn, L.V., J.E. Snawder, A.J. Kriech, et al.: Personal breathing zone exposures among hot-mix asphalt paving workers; Preliminary analysis for trends and analysis of work practices that resulted in the highest exposure concentrations. J. Occup. Environ. Hyg. 10(12):663–673 (2013). 18. Sivak, A., R. Niemeier, D. Lynch, et al.: Skin carcinogenicity of condensed asphalt roofing fumes and their fractions following dermal application to mice. Cancer Lett. 117:113–123 (1997). 19. Machado, M.L., P.W. Beatty, J.C. Fetzer, et al.: Evaluation of the relationship between PAH content and mutagenic activity of fumes from roofing and paving asphalts and coal tar pitch. Fund. Appl. Toxicol. 21:492–499 (1993). 20. Clark, C.R., D.M. Burnett, C.M. Parker, et al.: Asphalt fume dermal carcinogenicity potential: I. dermal carcinogenicity evaluation of asphalt (bitumen) fume condensates. Regul. Toxicol. Pharmcol. 61:9–16 (2011). 21. Watkins, D.K., L. Chiazze, C.D. Fryar, and W.A. Fayerweather: Casecontrol study of lung cancer and non-malignant respiratory disease among employees in asphalt roofing manufacturing and asphalt production. J.O.E.M. 44(6):551–558 (2002). 22. National Institute for Occupational Safety and Health (NIOSH): Particulates Not Otherwise Regulated, Total: Method 0500, Issue 2. In NIOSH Manual of Analytical Methods (4th ed.) Issued August 15, 1994. Available online at: http://www.cdc.gov/niosh/docs/2003154/pdfs/0500.pdf. 23. National Institute for Occupational Safety and Health (NIOSH): Benzene solubles fraction and total particulate (asphalt fume): Method 5042. In NIOSH Manual of Analytical Methods, 4th ed., 2nd Supplement)., P.M.

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Journal of Occupational and Environmental Hygiene

August 2015

Airborne Exposures to Polycyclic Aromatic Compounds Among Workers in Asphalt Roofing Manufacturing Facilities.

We studied exposure of 151 workers to polycyclic aromatic compounds and asphalt emissions during the manufacturing of asphalt roofing products-includi...
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