Bitumen Fumes Research Articles

Bayesian modelling of lung cancer risk and bitumen fume exposure adjusted for unmeasured confounding by smoking

Objectives:Residual confounding can be present in epidemiological studies because information on confounding factors was not collected. A Bayesian framework, which has the advantage over frequentist methods that the uncertainty in...

MONITORING POLYCYCLIC AROMATIC COMPOUNDS IN ENVIRONMENTAL AND WORKPLACE SAMPLES USING CONVENTIONAL METHODS AND THE AMES MUTAGENICITY ASSAY OF THEIR NITRATED DERIVATIVES

The development of sensitive methods for monitoring polycyclic aromatic compounds (PACs) has been a central focus of industrial hygiene studies in those industries where workers are exposed to petroleum oils, bitumen fumes or fuel combustion products. The work reported here focuses on one aspect of that effort—workplace monitoring of airborne PAC levels in the hot-mix asphalt paving industry. During the manufacture, transport, and roadway application of hot-mix asphalt (HMA), workers are exposed to low levels of bitumen fumes emanating from the hot product. Over the last twenty-five years, concerns about the health effects of these exposures have prompted numerous studies of the airborne levels of asphalt fumes in the workplace. By and large, these studies have shown that PAC exposures are extremely low—often below the detection limits of standard analytical techniques. For the present study, we have used standard industrial hygiene methods, together with a newer, biologically based assay called the Nitration Assay to measure relative ambient levels of fumes and/or PACs in various paving workplace settings. The latter assay was also used to test bitumen fumes generated in the laboratory by a new “microfuming” technique and to determine specific activities of the 16 PAHs designated by the US EPA as priority pollutants. The Nitration Assay takes advantage of two properties of 3–7-ring PACs: the ease with which they can be chemically nitrated and the high mutagenic potency of the nitrated products in the Ames Salmonella mutagenicity assay. Measurements of fumes and nitratable PAC levels on seven different hot-mix paving jobs showed reasonable correlations between the various methods, as well as patterns of exposure consistent with proximity to fume source.

Sensitivity of the association between increased lung cancer risk and bitumen fume exposure to the assumptions in the assessment of exposure

A multi-centre IARC-coordinated European cohort study provided evidence of an association between lung cancer risk and bitumen fume exposure. Sensitivity analyses were conducted to assess whether these associations were robust to assumptions in the exposure assessment for which support could not be obtained due to lack of either measurements or direct observations. New exposure estimates were generated by changing assumptions on exposure levels, specific tasks, lags, and coal tar use. Subsequently, Poisson regression models estimated relative risks (RRs); change in fit of models was evaluated. The influence of these assumptions was minimal, with log-likelihood deviations between -5.0 and 4.7% and similar patterns in dose-dependent increases of lung cancer risk. In the highest exposure categories, point estimates of RRs ranged 2.07-2.83 for average, and 1.22-2.23 for cumulative exposure. The small increase in lung cancer risk associated with bitumen fume exposure depends only to a limited extent on the subjective judgments made in the exposure assessment for this cohort.

Biological Monitoring as a Useful Tool for the Detection of a Coal-Tar Contamination in Bitumen-Exposed Workers

In our research project entitled “Chemical irritative and/or genotoxic effect of fumes of bitumen under high processing temperatures on the airways,” 73 mastic asphalt workers exposed to fumes of bitumen and 49 construction nonexposed workers were analyzed and compared with respect to polycyclic aromatic hydrocarbons (PAHs) exposure and exposure-related health effects. In order to assess the internal exposure the monohydroxylated metabolites of pyrene, 1- hydroxypyrene (1-OHP), and phenanthrene, 1-, 2- and 9-, and 3- and 4-hydroxyphenanthrene (OHPH) were determined in pre- and post-shift urinary samples. Significantly higher concentrations 1-OHP and OHPH were detected in the post-shift urine samples of 7 mastic asphalt workers working on the same construction site compared to the reference workers and all other 66 mastic asphalt workers. The adjusted mean OHPH in the reference, 66 mastic worker, and 7 worker subgroups was 1022, 1544, and 12919 ng/g creatinine (crn) respectively, indicating a marked rise in the 7 worker subgroup. In addition, there was a more than 12-fold increase of PAH metabolites from pre- to post-shift in these 7 workers, whereas in the other mastic asphalt workers there was only a twofold rise in PAH-metabolite concentration between pre- and post-shift values. The analysis of a drilling core from the construction site of the seven workers led to the detection of the source for this marked PAH exposure during the working shift as being coal tar plates, which were, without knowledge of the workers and coordinators, the underground material of the mastic asphalt layer. The evaluation of the stationary workplace concentration showed enhanced levels of phenanthrene, pyrene, fluorene, anthracene, and acenaphthene during working shifts at the construction site of these seven workers. Our study shows that biological monitoring is also a useful tool for the detection of unrecognized sources with high PAH concentrations.

Destruction of Highly Diluted Volatile Organic Components (VOCs) in Air by Dielectric Barrier Discharge and Mineral Bed Adsorption

In the past few years, air pollution control has been a priority of the European Union. In this paper, we present a new process specifically designed to treat bitumen fumes from covering plants: this process couples the destruction of the pollutant by activated (radicals and ions) molecules produced by a dielectric barrier discharge (DBD), a nonthermal plasma, and adsorption of converted pollutant molecules on a mineral bed. The process worked at atmospheric pressure and ambient temperature. Bitumen fumes contain volatile organic components (VOCs) and sulfured molecules responsible for the foul smell. Hydrodynamical simulations predicted that active species and the pollutant mix properly in the reactor, favoring plasma treatment. As a result, pollutant molecules were softly oxidized on ketones or alcoholic functions; their S−C bonds were broken by oxidative species, which led to the production of sulfur dioxide, and converted molecules formed aggregates. Plasma treatment also enhanced pollutant retention by mineral filters. Tests performed on half-scale laboratory pilots showed that the process is efficient in decreasing the VOC concentration, and a larger scale prototype is now being tested on a bitumen plant in France.

Polycyclic aromatic hydrocarbons emitted from a hot-mix drum, asphalt plant: study of the influence from use of recycled bitumen

Asphalt mixing is an industrial activity of which energy consumption can reach 60% of the total energy consumed by the construction and maintenance of a road over a 30-year service life. Hot mix asphalt plant represents the most common process found in the road sector. Hot bitumen fumes however contain polycyclic aromatic hydrocarbon (PAH) compounds, and, moreover, the use of recycled bitumen can lead to generating various emissions. Polycyclic aromatic hydrocarbons may also be emitted from the process itself, a step that requires warming and drying aggregate through combustion. In the aim of minimizing emissions, it has become necessary to identify the set of major influential parameters. A joint research program involving several institutions has been laid out to conduct an experimental campaign on the Blois Hot Mix Asphalt plant, with quantification of the 16 PAH listed by the USEPA. Variations in asphalt recycling rate favour emissions of heavy molecular weight PAH, among those analysed.

Evaluation of airborne respirable particulate matter and polycyclic aromatic hydrocarbon exposure of asphalt workers

Introduction: Assessment of exposure to the airborne respirable particles (PM10) and polycyclic aromatic hydrocarbons (PAHs) of asphalt manufacturing and road paving workers in the Campania region (Italy). Materials and Methods: A study was carried out during 2006 and involved 5 firms producing and employing bitumen in road paving activities. The workers studied were categorized on the basis of their job as workers in bitumen manufacturing, in road paving and in workers not exposed at bitumen fume considered like controls. Results: In the manufacturing plants the average concentrations of airborne PM10 were 1125±445 ìg/m3 in the HMA manufacturing workers’ areas; 314±81 ìg/m3 in the process surveyors’ cabins and 92±27 ìg/m3 in the controls’ areas (administrative offices). Within the breathing zones of the worker, the average PAHs levels in air were as follows: 367±198 ng/m3 for HMA manufacturing workers; 348±172 ng/m3 for process surveyors; 21±2 ng/m3 for the controls. At the road paving sites the average airborne PM10 levels were 1435±325 ìg/m3 for roller operators; 1610±356 ìg/m3 for paver operators; 319±108 ìg/m for the controls (traffic controllers). PAHs in the breathing zones were 1220±694 ng/m3 for the paver operators; 1360±575 ng/m3 for the roller operators’ and 139±135 ng/m3 for the traffic controllers’. The results show that the more consistent hazard for asphalt workers’ health is derived from exposure to airborne PM10 both in exposed and in non-exposed (controls) workers.

Risk assessment of workers exposed to fumes of bitumen: genotoxic effects and urinary metabolites of naphthalene, phenanthrene, and pyrene

Risk assessment of workers exposed to fumes of bitumen: genotoxic effects and urinary metabolites of naphthalene, phenanthrene, and pyrene

Bitumen products alter bax, bcl‐2 and cytokeratin expression: An in vivo study of chronically exposed road pavers

The skin of road pavers is chronically exposed to bitumen fumes, a mixture of volatile compounds and particles, containing several carcinogenic and non-carcinogenic polycyclic aromatic hydrocarbons. Bitumen fumes can alter cutaneous barrier integrity in various ways and induce skin diseases. The present study was devised to investigate the expression of apoptosis proteins (bax and bcl-2) and the cytokeratin pattern in skin specimens from road paving workers exposed to bitumen fumes using immunohistochemical techniques. Skin forearm punch biopsies from 16 occupationally exposed workers and an unexposed control group were processed for immunohistochemistry using a broad-spectrum anti-cytokeratin antibody and monoclonal antibodies for bax and bcl-2 immunostaining. Urinary 1-hydroxypyrene (1-OHP) was also determined. Morphological specimen evaluation showed epidermal thinning of exposed skin and flattened dermal papillae. In sections from exposed subjects, grade 3 bax overexpression and cytokeratin immunoreaction was detected in all layers, while bcl-2 expression was downregulated (grade 1) and confined to the basal layer. There was a significant difference in 1-OHP values between road pavers and the control group (p < 0.05). Overexpression of the cytokeratin pattern and bax and underexpression of bcl-2 in chronically bitumen-exposed skin suggest that bitumen fumes induce activation of apoptosis as a defense mechanism.

Importance of DNA-Adduct Formation and Gene Expression Profiling of Disease Candidate Genes in Rats Exposed to Bitumen Fumes

The equivocal experimental and epidemiological evidence of bitumen fumes and the possible mechanisms of toxicity remain uncertain. This study therefore aimed at investigating the genotoxicity of bitumen fumes, the biotransformation and urinary excretion of PAHs, and altered expression of a selected number of genes in lung, nasal epithelium, and white blood cells of rats. Animals were exposed to three different concentrations (low: 4 mg/m 3 ; medium: 20 mg/m 3 ; high: 100 mg/m 3 ) of bitumen fume condensate for 5 days, 30 days, and 12 months (6 hours per day) or ambient air. Notably, no dose-related signs of intolerance were observed throughout the inhalation period but dose dependent uptake of bitumen fumes was observed based on urinary excretion of PAHs and metabolites. At best, measurements of naphthols enabled an estimate of dose-dependent body burden. Excretion of 1-hydroxy- and 2-hydroxyphenanthrene was dose dependent and their production is catalyzed by the CYP1A1 monooxygenase which we found to be strongly induced upon exposure to bitumen fumes. Furthermore, pyrene, a minor component in bitumen fumes, produced hydroxypyrene levels close to the detection limit in rat urine. We additionally determined DNA adduct formation by the 32 P-postlabelling assay and observed a dose and time dependent increase of 3 to 4 stable DNA adducts in lung, nasal, and alveolar epithelium. DNA adduct levels were highest in nasal epithelium, the relative adduct level (RAL) being 450 adducts per 10 9 nucleotides. For lung and alveolar epithelium the RAL was 114 and 76 adducts per 10 9 nucleotides, respectively. However, we did not observe micronucleated red blood cells of the peripheral blood or with polychromatic erythrocytes of the bone marrow (after 12 months). It is important to note that erythrocyte cell count in bone marrow smears was reduced in four out of six animals after 12 months of exposure, clearly demonstrating that components of bitumen fume had reached the bone marrow. Finally, we investigated by reverse transcription polymerase chain reaction regulation of genes with known functions in inflammation, asthma and other pulmonary diseases. Gene expression changed during the time of exposure. With the monooxygenases CYP1A1 and CYP2G1 we observed dose dependent regulation in nasal and lung tissue. We also observed significant, but dose independent, regulation of cathepsin K and D, cadherin 22, platelet activating factor acetylhydrolase isoform 1b alpha subunit and the regulator of G-protein signalling in nasal epithelium of male rats after exposure to bitumen fumes. We found bitumen fumes to be genotoxic in target tissue of exposure and observed altered regulation of genes involved in the metabolic activation of polycyclic aromatic hydrocarbons and cellular inflammatory processes. These findings are consistent with the histopathology observed in the respiratory tract of rats chronically exposed to bitumen fume. An understanding of the regulation of suspected disease candidate genes in target tissues of exposure will be an interesting objective for further research into the mechanisms of toxicity.

Generation of Bitumen Fumes Using Two Fume Generation Protocols and Comparison to Worker Industrial Hygiene Exposures

This study had two fundamental goals. The first was to collect sufficient quantities of bitumen fumes used in both the roofing and paving industry in the United States to do detailed chemical and biological testing in preparation for a two-year animal skin painting study on select samples. These bitumen fumes need to be similar to the fumes to which workers in these industries are actually exposed. In this first phase, bitumen from four geographical regions of the United States were selected, which produced bitumen from four different major crude sources in roofing and four sources in paving. Each source was supplied to projects where workers were monitored for exposure. The industrial hygiene samples from workers were then tested for physical and chemical properties. These results were used to guide collection of fumes from each source using the vapor headspace of tanks containing each bitumen. Bitumen fumes were collected using the same protocol that the Fraunhofer Institute of Technology and Medicine employed in a recent animal inhalation study. The second goal of this study was to better understand previous studies conducted by NIOSH which generated fumes for mouse skin painting studies using a roofing bitumen in a laboratory fume generator. In the current study, bitumen fumes from the four roofing sources were generated using the NIOSH protocol and compared to fumes collected in the roofing work sites and taken from the tank headspace. One of the sources was selected to generate enough fumes for a chronic two-year animal skin painting study. Results from an array of physical, chemical and biological tests were used to characterize the subsequent fumes. Acceptance criteria were designed to match parameters that could be analyzed both on the workplace samples and the bitumen fumes collected from the tank and involved three basic categories: simulated distillation, fluorescence and gas chromatography/mass spectroscopy for polynuclear aromatic hydrocarbon analysis and extracted ion fingerprinting. Methods employed for the collection of these fumes were selected to optimize the capture of the most toxicologically relevant components. Distinctions between paving and roofing fume samples are outlined. Bitumen fumes from the paving sources produced from four different crude sources were quite similar to each other in a number of the tests performed. Bitumen fumes from the roofing sources also were very similar to each other. On the other hand, fumes generated using the NIOSH protocol show results that significantly differ from the corresponding worker exposures.

Assessment of Irritative Effects of Fumes of Bitumen on the Airways by using Non-Invasive Methods—Results of a Cross-Shift Study in Mastic Asphalt Workers

Data concerning the irritative effects of current exposure to fumes of bitumen on the airways in humans are limited. To assess the effects of fumes of bitumen on the airways a cross-shift study was conducted with monitoring of inflammatory process in upper and lower airways of workers exposed to fumes of bitumen and a reference group. All workers were examined immediately before and after shift. At both time points, spirometry was performed and nasal lavage fluid (NALF), induced sputum and spot urine were collected. Cellular composition and inflammatory mediator profile of the NALF and sputum samples were analyzed. Personal air sampling in each mastic asphalt worker's breathing zone was carried out to measure exposure to fumes of bitumen. The present cross-shift study with 202 mastic asphalt workers exposed to fumes of bitumen and 55 roadside construction workers as the reference group showed that fumes of bitumen released under high processing temperatures by mastic asphalt handling can exert acute and (sub-)chronic irritative effects on the upper and lower airway assessed with nasal lavage and induced sputum analysis. Airborne personal exposure to fumes of bitumen was associated with significant cross-shift declines in lung function parameters. Pre-shift lung function parameters (forced expiratory volume in 1 s [FEV 1 ] and forced vital capacity [FVC]) were significantly higher in the exposure group that pointed to a “healthy worker effect.” Possible carry-over effects could be observed in elevated pre-shift levels of several inflammation parameters in exposed workers indicating a (sub)chronic inflammation in these groups. Elevated interleukin-8 and protein levels in bitumen-exposed workers in sputum samples were found, but not in the nasal lavage fluid. The results emphasize irritative effects on the upper and lower airways under high exposure to fumes of bitumen. A more detailed analysis will be provided when all workers will be enrolled in that study.

Laboratory Generated Bitumen Fumes Under Standardized Conditions. Clean-up Scheme and Ion Trap GC-MS Analysis of VOC, Semi-Volatile and Particulate PAH and PASH

This article reports the applicability of an efficient clean-up and enrichment procedure for the determination of polycyclic aromatic compounds (PAC) including polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic sulfur heterocyclic hydrocarbons (PASH) in the gas and particulate phases in raw bitumen and bitumen fumes by gas chromatography-ion trap mass spectrometry. The scheme includes a liquid-liquid partition to eliminate the aliphatics, a solid phase extraction on SiO2 cartridge to remove the polar compounds and an HPLC fractionation to isolate the aromatic fraction. The purified extract enables the determination of PAH profile from 2 to 7 rings including their methyl derivatives and 3 carcinogenic benzonaphthothiophene isomers. The reproducibility of the method was estimated by analyzing 6 bitumen replicates and is around the 30% overall uncertainty or less. In bitumen fumes generated at 170°C under standardized conditions, VOC and semi-volatile PAH were sampled with XAD-2 tubes and were also determined in six replicates. The VOCs are mainly monoaromatic derivatives (4% of fumes) and aliphatics essentially from C6 to C17 (27%). With regards to the particulate phase PAC, the coefficients of variation from 6 replicates are 5–24% for PAH and 6–10% for PASH. Data on VOC and PASH represent new contribution in the characterization of bitumen fumes.

Assessment of the Pulmonary Genotoxicity of Bitumen Fumes in Big Blue® Transgenic Rats

Occupational and environmental exposures to bitumen fumes during road paving or roofing activities represent a safety issue since this complex mixture of volatile compounds and particles contains carcinogenic polycyclic aromatic hydrocarbons (PAH). However, epidemiological and experimental animal studies failed to draw unambiguous conclusions concerning bitumen fumes toxicity. In order to gain better insights on their genotoxic potential, we used an experimental device able to generate bitumen fumes at 170°C (upper range used during road paving operations) with a total particulate matter of 112 ± 13 mg/m3 and a mass median aerodynamic diameter of 4.6 μ m. The nose-only exposure of Big Blue® transgenic rats was performed 6 h/day for 5 consecutive days. Biological exposure to this aerosol was monitored by measuring the rat urinary levels of 1-hydroxypyrene and lungs were collected at various time-points after the end of treatment for further analysis. As determined by the 32P post-labeling method, no DNA bulky adduct was found in control animal lungs, while one was detected in exposed rats 3 and 30 days after the end of treatment, suggesting that this genetic alteration was rather stable. However, there was no correlation between the amount of DNA adduct and the level of urinary of 1-hydroxypyrene. The pulmonary mutagenic properties of bitumen fumes were determined by analyzing the mutation frequency and spectrum of the neutral reporter gene cII inserted into the transgenic rodent genome. Thirty days after exposure, the cII mutant frequency was similar in control and exposed rat lungs. However, a modification of the mutation spectrum was noticeable in treated animals. The most striking difference was an increase of G:C to T:A and A:T to C:G transversions in exposed rodents. In addition, the increased occurrence of G:C to T:A transversions at CpG dinucleotides in treated animals was consistent with DNA adduction by PAH. Even though these data failed to demonstrate a clear pulmonary mutagenic potential of bitumen fumes in our experimental conditions, the analysis of the mutational spectrum provides a sensitive measure of a quantitative increase of specific mutations which may be associated with DNA adduct formation. The weak mutagenic response might also be related to the small inhalable fraction of bitumen fume particles reaching the deep lung. In conclusion, these results could give insights on the mechanism of action of bitumen fumes and provide additional information concerning human risk assessment associated with bitumen exposure.

Review of Skin Permeation Hazard of Bitumen Fumes

The potential for health hazards arising from dermal exposure and possible uptake of bitumen fume or components is unclear. In 2001 the German MAK committee has assigned a “H-notation” to bitumen fumes. However, the assignment of a skin notation to bitumen fumes is under debate. The American Conference of Governmental Industrial Hygienists (ACGIH®) concluded in 1999 that assigning a skin notation was not justified. NIOSH did not develop a conclusion on this aspect in their health hazard review of bitumen fumes in 2000. The present study aimed to update and review the strength of evidence of scientific knowledge on the skin permeation hazard of bitumen fumes among workers.

Ambient and Biological Monitoring of Exposure and Genotoxic Effects in Mastic Asphalt Workers Exposed to Fumes of Bitumen

Mastic asphalt workers may be exposed to polycyclic aromatic hydrocarbons (PAH) present in bitumen. We conducted a cross-shift study to determine genotoxic effects after exposure to bitumen. For this purpose, external and internal exposure of 202 mastic asphalt workers exposed to bitumen and 55 construction workers without exposure to bitumen was assessed. Exposure by inhalation to fumes of bitumen during the shift was measured by personal ambient monitoring. To assess overall exposure to bitumen (by inhalation and dermal absorption), 1-hydroxypyrene (1-OHP) and the sum of 1-, 2 + 9-,3-,4-hydroxyphenanthrene (OHPhe) were determined in pre- and postshift urine. 8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) adducts, anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (anti-BPDE) DNA adducts, DNA strand breaks and alkali-labile sites, and micronucleus frequencies were determined as biomarkers of genotoxic effects in white blood cells (WBC). Concentrations of fumes of bitumen were correlated with a moderate association with 1-OHP and OHPhe after work shift (r s = 0.25, P < 0.001 and r s = 0.36, P < 0.001). Significantly increased 8-oxodGuo adduct levels were observed after shift in both exposure groups (P < 0.0001). Paradoxically, decreased DNA strand break frequencies were observed after shift in both groups (P < 0.05). Postshift values in DNA strand break frequency were associated with 1-OHP (Spearman rank correlation coefficient 0.19, P = 0.01). Significantly more 8-oxodGuo adducts and DNA strand breaks were found in workers exposed to bitumen before and after shift compared with the reference group. However, no dose-dependent association was observed between exposure and genotoxic effects. Nevertheless, the findings indicate that workers exposed to bitumen exerted a higher level of DNA damage (8-oxodGuo and DNA strand breaks) in WBC compared with reference subjects.

Assessment of Exposure to Polycyclic Aromatic Hydrocarbons (PAH) in Italian Asphalt Workers

The purpose of the work was the assessment of exposure to Polycyclic Aromatic Hydrocarbons (PAH), a family of ubiquitous pollutants of which some are carcinogens, in 100 Italian asphalt workers (exposed to bitumen fumes and diesel exhausts) and in a reference group of 47 ground construction operators (exposed only to diesel exhausts, reference group). The protocol included interview via questionnaires, environmental air-monitoring (active personal sampling during the work shift), dermal contamination measures (six pads placed on worker's wrist, neck, arm, chest, thigh, and ankle), and biological monitoring (determination of 1-hydroxypyrene in urine spot samples collected three at different moments: baseline after two days of vacation, before shift, and at end shift on a day in the second half of the week). Analysis of the most relevant PAH, according to the American Environmental Protection Agency, EPA, was performed by High Performance Liquid Chromatography (HPLC) by fluorimetric detector. Median airborne levels of PAH ranged from 426 to below 0.03 ng/m3. Vapor-phase PAH, apart from naphthalene, were significantly higher in asphalt workers than in the reference group. Particle-phase PAH were similar and very low (< 1 ng/m3) in both exposure groups. Exposure levels did not vary in different work-tasks. Excretion of urinary 1-hydroxypyrene (expressed by ng/g creatinine) showed a significant increase at different sampling moments in asphalt workers, smokers, and non-smokers: baseline was lower than at the beginning of the workshift, and values were even higher in the end workshift sample. Comparing the two groups, a significant difference in the levels of metabolite does not appear, whereas this trend can be viewed observing the non-smokers. All body regions monitored by pads showed equivalent values levels of Dermal Deposition Density in both exposure groups. The measured amount of dermal contamination was significantly higher in asphalt workers than in ground construction operators. In asphalt workers, skin contamination was significantly higher during asphalt paving than during asphalt mixing. Dermal Exposure Rate was calculated about threefold higher than Airborne Exposure Rate; whereas considering toxicokinetical information (Kp, lag time, experimental dermal absorption data) and hygienistic data (particle size of bitumen fume), the relevance of dermal absorption is lower than respiratory. The results of this study demonstrate that asphalt workers experience slight occupational exposure to PAH, both by inhalatory and dermal routes, resulting in a significant increase of urinary 1-hydroxypyrene during the workweek.

Physical and Chemical Characterization of Asphalt (Bitumen) Paving Exposures

The purpose of this research was to characterize the physical and chemical properties of asphalt (bitumen) fume and vapor in hot mix asphalt roadway paving operations. Area and personal air samples were taken using real-time equipment and extractive sampling and analytical methods to determine worker asphalt exposure, as well as to characterize the properties of the particulate and vapor phase components. Analysis of personal inhalation and dermal samples by gas chromatography/mass spectroscopy showed that the polycyclic aromatic hydrocarbon profile is dominated by compounds with molecular weights below 228, and that substituted and heterocyclic polycyclic aromatic hydrocarbons comprised approximately 71% of the detectable mass concentration (vapor and particulate combined). Principal components analysis shows that the polycyclic aromatic hydrocarbons with molecular weights greater than 190 are the driving force behind the polycyclic aromatic compound exposures measured for the dermal and particulate phases; there was no clear trend for the vapor phase Most of the aerosol particles are fine (mass median aerodynamic diameter 1.02 μ m; count median diameter 0.24 μ m).

Determination of Sequence Variants of Metabolizing Enzymes After Occupational Exposure to Fumes of Bitumen Under High Processing Temperatures

Data concerning the influence of sequence variants of metabolizing enzymes on the effect modulation of current exposure to fumes of bitumen in humans are limited. To assess effect modulation of genetic variants of metabolizing enzymes, 18 single nucleotide polymorphisms (SNPs) in metabolic enzymes were analyzed regarding their impact on the urinary levels of metabolites of polycyclic aromatic hydrocarbons. Based on personal ambient monitoring data for bitumen emissions a group of 180 workers exposed to fumes of bitumen under high processing temperatures during a shift were divided into two exposure groups: 24 with high exposure (> 10 mg/m3) and 156 with low (≤ 10 mg/m3) exposure. Additionally, 55 roadside construction workers without exposure to bitumen but with similar working tasks served as a reference group. SNP determination was performed by real-time PCR using the LightCycler technology based on DNA aliquots from blood samples. The impact of sequence variants on the urinary levels of 1-OH pyrene (1-OHP) and sum of OH-phenanthrenes (OHPhe) was estimated with mixed linear models, adjusted for exposure, smoking, and other factors. Bitumen exposure was a significant predictor of the urinary concentrations of 1-OHP and OHPhe. Both metabolite levels were modulated by the GG variant of the cytochrome P450 SNP CYP3A4 −392A > G , which showed increased levels of 1-OHP (p = 0.013) and OHPhe (p = 0.001). The GG variant of EPHX1 15543A > G showed a significant effect (p = 0.006) only on OHPhe. Selected variants of metabolic enzymes can modulate the metabolite levels under exposure to bitumen. The SNP-related modulation of these biomarkers did not exceed a factor of two and is more pronounced for OHPhe than for 1-OHP.

Percutaneous Absorption of Polycyclic Aromatic Compounds from Bitumen Fume Condensate

Bitumen fume condensate was obtained from the headspace vapors of a bitumen storage tank containing a lightly oxidized paving-bitumen for the purpose of developing an in vitro procedure to estimate the percutaneous absorption, through human skin, of the very low levels of polycyclic aromatic compounds found in the condensate. The Fraunhofer Institute of Toxicology and Medicine provided the fume condensate and analyses of the individual polycyclics present. Heritage Research Group provided analyses of total 3–6 ring polycyclics. Sections of human back skin were sliced with a dermatome to a thickness of ∼ 250 μ m, and 1-inch circular pieces were mounted in 6 Franz diffusion cells. Tissue integrity was assured by electrical resistance measurement. Neat condensate was applied to the stratum corneum at “infinite dose” (200 μ l) while the dermis was in direct contact with a receptor fluid consisting of an aqueous solution of polyoxyethylene 20 oleyl ether. Receptor fluids were sampled at 12 intervals over 48 hours, and analyzed by an HPLC system equipped with a variable wavelength detector and a fluorescence detector connected in series. The UV detector was generally operated at 254 nm, and the fluorescence detector at ex360nm/em400nm, 18 nm bandpass. The mobile phase was a 60–100% acetonitrile/water gradient. Penetration rates of anthracene, fluoranthene-pyrene, and total 3–6 ring polycyclic aromatic compounds (PAC) were measured. The neat condensate was 32.7 μ g/g anthracene, 7.4 μ g/g fluoranthene, 7.3 μ g/g pyrene, and 1.8 mg/g total 3–6 ring PAC. The rates of dermal penetration (ng/cm2/hr ± SD) were: anthracene 6.5 ± 0.9; fluoranthene-pyrene 1.8 ± 0.3; and 3–6 ring PAC 120 ± 30. Percentages of applied dose absorbed were: anthracene 5.3%, fluoranthene-pyrene 3.3%, and 3–6 ring PAC 1.8%. The apparent permeability coefficient Kp (Kp = flux rate/applied concentration) for anthracene was 2 × 10− 4 cm/hr. These results demonstrate that penetration of PAC, at the low concentrations found in bitumen fume condensates, can be measured by an appropriately designed in vitro method. Rates of PAC percutaneous absorption will be further evaluated in the future with other fume condensates obtained from several different straight run paving asphalts.