Review of environmental airborne pyrene/benzo[a]pyrene levels from industrial emissions for the improvement of 1-hydroxypyrene biomonitoring interpretation

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants of significant public health concern, with several that are highly toxic to humans, including some proven or suspected carcinogens. To account for the high variability of PAH mixtures encountered in occupational settings, adjusting urinary 1-hydroxypyrene (1-OHP) levels by the total airborne pyrene (PyrT)/benzo[a]pyrene (BaP) ratio is essential for human biomonitoring (HBM). Given the complexity and cost of systematically monitoring atmospheric levels, alternative approaches to simultaneous airborne and HBM are required. The aim of this review was to catalog airborne PyrT/BaP ratios measured during different industrial activities and recommend 1-OHP-dedicated biological guidance values (BGV). A literature search was conducted. Seventy-one studies were included, with 5619 samples pertaining to 15 industrial sectors, 79 emission processes, and 213 occupational activities. This review summarized more than 40 years of data from almost 20 countries and highlighted the diversity and evolution of PAH emissions. PyrT/BaP ratios were highly variable, ranging from 0.8 in coke production to nearly 40 in tire and rubber production. A single PyrT/BaP value cannot apply to all occupational contexts, raising the question of the relevance of defining a single biological limit value for 1-OHP in industrial sectors where the PyrT/BaP ratio variability is high. Based upon the inventory, a practical approach is proposed for systematic PAH exposure and risk assessment, with a simple frame to follow based upon specific 1-OHP BGVs depending upon the occupational context and setup of a free PAH HBM interactive tool.

Bitumen fumes and PAHs in asphalt road paving: Emission characteristics, determinants of exposure and environmental impact

BACKGROUND

Asphalt road paving and its subsequent complex airborne emissions have raised concerns about occupational exposures and environmental impacts. Although several studies described bitumen fumes or Polycyclic Aromatic Hydrocarbons (PAH) emissions at specific worksites, no comprehensive studies have characterised road paving emissions and identified the main determinants of exposure.

METHODS

A 10-year study from 2012 to 2022 was performed to examine the pollutants resulting from bitumen fume emissions and covering the main processes used in road paving (asphalt production, mechanical rolled asphalt paving, manual paving, mastic asphalt paving, emulsion paving, and coal-tar asphalt milling). A total of 623 air samples were collected at 63 worksites (on 290 workers, in the environment and near emission sources), and bitumen fumes, PAHs, aldehydes and volatile organic compounds were analysed. Biomonitoring campaigns were performed on 130 workers to assess internal exposure to PAHs.

RESULTS

Fume emissions revealed complex mixtures of C₁₀-C₃₀ compounds, including linear saturated hydrocarbons (C₆-C₁₂), alicyclic hydrocarbons and aliphatic ketones. PAHs were dominated by 2-3 aromatic ring compounds (naphthalene, fluorene, and phenanthrene), and C₁-C₁₃ aldehydes were identified. Binder proportion, paving temperature, outdoor temperature, workload and job category influenced airborne concentrations. A significant temporal trend was observed over the time period of the study, with decreasing BF and PAH exposures. PAH biomonitoring was consistent with air samples, and urinary metabolites of 2-3 ring PAHs dominated over 4-5 ring PAHs. Occupational exposures were generally far lower than exposure limits, except coal-tar asphalt milling activities. Very low environmental concentrations were measured, which highlights a negligible contribution of paving emissions to global environmental pollution.

CONCLUSION

The present study confirmed the complex nature of bitumen fumes and characterised the main determinants of exposure. The results highlight the need to reduce the paving temperature and binder proportion. Recycled asphalt pavement use was not associated with higher emissions. The impact of paving activities on environmental airborne pollution was deemed negligible.

GuLF DREAM: A Model to Estimate Dermal Exposure Among Oil Spill Response and Clean-up Workers

Tens of thousands of individuals performed oil spill response and clean-up (OSRC) activities following the 'Deepwater Horizon' oil drilling rig explosion in 2010. Many were exposed to oil residues and dispersants. The US National Institute of Environmental Health Sciences assembled a cohort of nearly 33 000 workers to investigate potential adverse health effects of oil spill exposures. Estimates of dermal and inhalation exposure are required for those individuals. Ambient breathing-zone measurements taken at the time of the spill were used to estimate inhalation exposures for participants in the GuLF STUDY (Gulf Long-term Follow-up Study), but no dermal measurements were collected. Consequently, a modelling approach was used to estimate dermal exposures. We sought to modify DREAM (DeRmal Exposure Assessment Method) to optimize the model for assessing exposure to various oil spill-related substances and to incorporate advances in dermal exposure research. Each DREAM parameter was reviewed in the context of literature published since 2000 and modified where appropriate. To reflect the environment in which the OSRC work took place, the model treatment of evaporation was expanded to include vapour pressure and wind speed, and the effect of seawater on exposure was added. The modified model is called GuLF DREAM and exposure is estimated in GuLF DREAM units (GDU). An external validation to assess the performance of the model for oils, tars, and fuels was conducted using available published dermal wipe measurements of heavy fuel oil (HFO) and dermal hand wash measurements of asphalt. Overall, measured exposures had moderate correlations with GDU estimates (r = 0.59) with specific correlations of -0.48 for HFO and 0.68 for asphalt. The GuLF DREAM model described in this article has been used to generate dermal exposure estimates for the GuLF STUDY. Many of the updates made were generic, so the updated model may be useful for other dermal exposure scenarios.

Assessing Exposures from the Deepwater Horizon Oil Spill Response and Clean-up

The GuLF Study is investigating adverse health effects from work on the response and clean-up after the Deepwater Horizon explosion and oil release. An essential and necessary component of that study was the exposure assessment. Bayesian statistical methods and over 135 000 measurements of total hydrocarbons (THC), benzene, ethylbenzene, toluene, xylene, and n-hexane (BTEX-H) were used to estimate inhalation exposures to these chemicals for >3400 exposure groups (EGs) formed from three exposure determinants: job/activity/task, location, and time period. Recognized deterministic models were used to estimate airborne exposures to particulate matter sized 2.5 µm or less (PM2.5) and dispersant aerosols and vapors. Dermal exposures were estimated for these same oil-related substances using a model modified especially for this study from a previously published model. Exposures to oil mist were assessed using professional judgment. Estimated daily THC arithmetic means (AMs) were in the low ppm range (<25 ppm), whereas BTEX-H exposures estimates were generally <1000 ppb. Potential 1-h PM2.5 air concentrations experienced by some workers may have been as high as 550 µg m-3. Dispersant aerosol air concentrations were very low (maximum predicted 1-h concentrations were generally <50 µg m-3), but vapor concentrations may have exceeded occupational exposure excursion guidelines for 2-butoxyethanol under certain circumstances. The daily AMs of dermal exposure estimates showed large contrasts among the study participants. The estimates are being used to evaluate exposure-response relationships in the GuLF Study.

Estimation of Dermal Exposure to Oil Spill Response and Clean-up Workers after the Deepwater Horizon Disaster

The GuLF STUDY is investigating health outcomes associated with oil spill-related chemical exposures among workers involved in the spill response and clean-up following the Deepwater Horizon disaster. Due to the lack of dermal exposure measurements, we estimated dermal exposures using a deterministic model, which we customized from a previously published model. Workers provided information on the frequency of contact with oil, tar, chemical dispersants applied to the oil spill and sea water, as well as the use of protective equipment, by job/activity/task. Professional judgment by industrial hygienists served as a source of information for other model variables. The model estimated dermal exposures to total hydrocarbons (THC), benzene, ethylbenzene, toluene, xylene, n-hexane (BTEX-H), polycyclic aromatic hydrocarbons (PAHs), and dispersants in GuLF DREAM units (GDUs). Arithmetic means (AMs) of THC exposure estimates across study participants ranged from <0.02 to 5.50 GDUs for oil and <0.02 to 142.14 GDUs for tar. Statistical differences in the estimates were observed among the AMs of the estimates for some broad groups of worker activities over time and for some time periods across the broad groups of activities. N-Hexane had ranges similar to THC for oil exposures (e.g. AMs up to 2.22 GDUs) but not for tar (up to 5.56 GDUs). Benzene, ethylbenzene, toluene, and xylene, in contrast, were characterized by higher exposure levels than THC for oil (AMs up to 12.77, 12.17, 17.45, and 36.77 GDUs, respectively) but lower levels than THC to tar (AMs up to 3.69, 11.65, 42.37, and 88.18 GDUs, respectively). For PAHs, the AMs were as high as 219.31 and 587.98 for oil and tar, respectively. Correlations of these seven substances to each other were high (>0.9) for most of the substances in oil but were lower for some of the substances in tar. These data were linked to the study participants to allow investigation of adverse health effects that may be related to dermal exposures.

Occupational Exposure during Asphalt Paving-Comparison of Hot and Warm Mix Asphalt in Field Experiments

OBJECTIVES

Several studies have demonstrated an increased risk of adverse health effects, including reduced lung function and lung cancer among asphalt pavers, which has been related to occupational exposure to contaminants during asphalt paving. Consequently, occupational exposure among asphalt pavers must be reduced. The aim of this study was to compare the impact of hot mix asphalt (HMA) and warm mix asphalt (WMA) paving on occupational exposure levels during road paving in field experiments. Asphalt temperatures when paving with WMA are usually lower than when paving with HMA due to differences in the asphalt's composition and method of application.

METHODS

On 11 different road sections, one lane was paved with WMA and one with HMA during the same work shift under approximately identical weather conditions. The weather conditions and asphalt surface temperature were monitored during paving. Fifty-seven samples of fumes and vapor, organic and elemental carbon, amines, and respirable, thoracic, and inhalable particulate matter (PM) fractions were collected by stationary sampling. In addition, 30 samples of fumes and vapor were collected by personal sampling.

RESULTS

Compared to paving with HMA, paving with WMA significantly (P < 0.05; paired Student's t-test) reduced the geometric mean (GM) air concentration of asphalt vapor (0.04 versus 0.08 p.p.m.), organic carbon (OC; 0.09 versus 0.18 mg m-3), and respirable PM (0.12 versus 0.22 mg m-3). Additionally, the air concentration of OC correlated strongly with the respirable fraction of PM (Pearson's correlation coefficient 0.83).

CONCLUSIONS

Measured airborne concentrations of respirable PM, OC, and asphalt vapor were lower when paving with WMA than with HMA. Because exposure to airborne contaminants generated during asphalt paving is believed to be responsible for the adverse health effects observed among asphalt pavers, paving with WMA rather than HMA may have health benefits.

Asphalt-related emissions are a major missing nontraditional source of secondary organic aerosol precursors

Asphalt-based materials are abundant and a major nontraditional source of reactive organic compounds in urban areas, but their emissions are essentially absent from inventories. At typical temperature and solar conditions simulating different life cycle stages (i.e., storage, paving, and use), common road and roofing asphalts produced complex mixtures of organic compounds, including hazardous pollutants. Chemically speciated emission factors using high-resolution mass spectrometry reveal considerable oxygen and reduced sulfur content and the predominance of aromatic (~30%) and intermediate/semivolatile organic compounds (~85%), which together produce high overall secondary organic aerosol (SOA) yields. Emissions rose markedly with moderate solar exposure (e.g., 300% for road asphalt) with greater SOA yields and sustained SOA production. On urban scales, annual estimates of asphalt-related SOA precursor emissions exceed those from motor vehicles and substantially increase existing estimates from noncombustion sources. Yet, their emissions and impacts will be concentrated during the hottest, sunniest periods with greater photochemical activity and SOA production.

Oxidative contribution of air pollution to extrinsic skin ageing

•Epidemiological evidence links exposure to poor air quality to lentigines and wrinkles. •Experimental studies provide mechanistic explanations involving oxidative stress. •Polluted air may hasten skin ageing through indirect systemic effects via the lung and/or direct effects on cutaneous tissue. •Prevention measures would need to combine strategies that target both ‘routes’. •Air pollution is one of several environmental stressors that combined, may have additive/synergistic effects on the skin.

Emissions into the Air from Bitumen and Rubber Bitumen-Implications for Asphalt Workers' Exposure

The risk among asphalt workers of developing adverse health effects may increase due to their occupational exposure. One area of special concern arises when rubber granules are mixed into bitumen to enhance asphalt properties. This research characterizes and compares bitumen and rubber bitumen regarding the emissions of and workers' exposure to particulates, polycyclic aromatic hydrocarbons (PAHs) and benzothiazole. A laboratory and a field study were carried out. In the laboratory, two types of bitumen, one with and one without rubber, were heated up to two temperatures (140°C and 160°C). The concentrations and chemical compositions of the emissions were determined. In the field at asphalt work sites, both emissions and worker exposure measurements were performed. The methods applied included direct-reading sampling techniques next to the asphalt work area and personal sampling techniques on asphalt workers. The exposure measurements on asphalt workers for respirable dust, total dust, particle number and mass, and total PAH concentrations showed similar concentrations when both standard and rubber bitumen were used. The asphalt-surfacing machine operators were the workers with the highest observed exposure followed by the screed operators and roller drivers. Both laboratory and field measurements showed higher concentrations of benzothiazole when rubber bitumen was used, up to 7.5 times higher in the laboratory. The levels of naphthalene, benzo(a)pyrene, and total particles were lower for both types compared with the Swedish occupational exposure limits, 8-h time weighted average concentrations. Benzo(a)pyrene exceeded however the health-based guideline value given by the WHO for both types of bitumen. The study concludes that several air pollutants such as benzothiazole and PAHs are emitted into the air during asphalt work, but it is not evident if exposure to rubber bitumen possesses a higher risk than exposure to standard bitumen in terms of asphalt worker exposure.

Effects of asphalt source and mixing temperature on the generated asphalt fumes

Asphalt fumes generated in pavement construction have been extensively studied from the perspective of occupational health. In this paper, they are examined from the perspective of material and construction. Asphalt binders from different sources were used to create standard mixtures. An asphalt fume generation and collection system was designed and built for generating fumes at simulated construction conditions and collecting fumes similar to the procedure used in field exposure studies. Total particulates (TP) in the fume samples were analyzed gravimetrically, and the chemical components of the samples were identified by using GC/MS. Results indicate that the TP concentration and chemical component of asphalt fumes are dependent on asphalt source and temperature. The concentration from one asphalt can be several times higher than that from another. With a temperature rise in 20 °C, the concentration increases about 3-7 times. At 140 °C, the total number of detected PAHs ranges from 4 to 9; at 160 °C, the number ranges from 4 to 12. The hazardous potentials of asphalt fumes vary with asphalt source and mixing temperature. Therefore, standardized laboratory test procedures are needed for risk assessment, based on which proper material selection and construction strategies may be chosen for hazard mitigation.

Occupational exposure to asphalt mixture during road paving is related to increased mitochondria DNA copy number: a cross-sectional study

BACKGROUND

Asphalt workers are exposed to polyaromatic hydrocarbons (PAHs) from hot mix asphalt via both inhalation and dermal absorption. The use of crumb rubber modified (CRM) asphalt may result in higher exposure to PAHs and more adverse effects. Our aim is to assess occupational exposure to PAHs from conventional and CRM asphalt paving by measuring PAH metabolites in urine, and to investigate the effects on mitochondrial DNA copy number (mtDNAcn) and telomere length.

METHODS

We recruited 116 workers paving conventional asphalt, 51 workers paving CRM asphalt and 100 controls in Sweden, all males. A repeated-measures analysis included 31 workers paving both types of asphalt. Urine and blood samples were collected pre-working on Monday morning and post-working on Thursday afternoon after 4 days working. PAH metabolites: 1-hydroxypyrene (1-OH-PYR) and 2-hydroxyphenanthrene (2-OH-PH) were measured in urine by LC-MS/MS. Relative mtDNAcn and telomere length were measured by quantitative PCR.

RESULTS

Conventional and CRM asphalt workers showed higher 1-OH-PYR and 2-OH-PH than controls (p < 0.001 for all). Relative mtDNAcn were 0.21 units (p < 0.001) higher in conventional asphalt workers and 0.13 units (p = 0.010) higher in CRM asphalt workers compared to controls. Relative telomere length did not differ across occupational groups, but it was positively associated with increment of 2-OH-PH (β = 0.075, p = 0.037) in asphalt workers. The repeated-measures analysis showed no difference in either increment of 1-OH-PYP, or changes in effect biomarkers (mtDNAcn or telomere length) between paving with conventional and CRM asphalt. Increment of 2-OH-PH was smaller after paving with CRM asphalt.

CONCLUSIONS

Road asphalt paving in open areas resulted in PAHs exposure, as shown by elevation of PAH metabolites in urine. Asphalt workers may experience oxidative stress, evidenced by alternation in mtDNAcn; however the effects could not be fully explained by exposure to PAHs from the asphalt mixture.

Short-term markers of DNA damage among roofers who work with hot asphalt

BACKGROUND

Roofers are at increased risk for various malignancies and their occupational exposures to polycyclic aromatic hydrocarbons (PAHs) have been considered as important risk factors. The overall goal of this project was to investigate the usefulness of phosphorylated histone H2AX (γH2AX) as a short-term biomarker of DNA damage among roofers.

METHODS

Blood, urine, and dermal wipe samples were collected from 20 roofers who work with hot asphalt before and after 6 h of work on Monday and Thursday of the same week (4 sampling periods). Particle-bound and gas-phase PAHs were collected using personal monitors during work hours. γH2AX was quantified in peripheral lymphocytes using flow cytometry and 8-hydroxy-2-deoxyguanosine (8-OHdG) was assessed in urine using ELISA. General linear mixed models were used to evaluate associations between DNA damage and possible predictors (such as sampling period, exposure levels, work- and life-style factors). Differences in mean biomarker and DNA damage levels were tested via ANOVA contrasts.

RESULTS

Exposure measurements did not show an association with any of the urinary biomarkers or the measures of DNA damage. Naphthalene was the most abundant PAH in gas-phase, while benzo(e)pyrene was the most abundant particle-bound PAH. Post-shift levels of γH2AX and 8-OHdG were higher on both study days, when compared to pre-shift levels. Cigarette smoking was a predictor of γH2AX and urinary creatinine was a predictor of urinary 8-OHdG. Between-subject variance to total variance ratio was 35.3 % for γH2ax and 4.8 % for 8-OHdG.

CONCLUSION

γH2AX is a promising biomarker of DNA damage in occupational epidemiology studies. It has a lower within-subject variation than urinary 8-OHdG and can easily be detected in large scale groups. Future studies that explore the kinetics of H2AX phosphorylation in relation to chemical exposures may reveal the transient and persistent nature of this sensitive biomarker of early DNA damage.

A review of the current state of the art of physiologically-based tests for measuring human dermal in vitro bioavailability of polycyclic aromatic hydrocarbons (PAH) in soil

Polycyclic Aromatic Hydrocarbons are classed as Persistent Organic Pollutants, a large group of compounds that share similar characteristics. They are lipophilic, resistant to degradation in the environment and harmful to human and environmental health. Soil has been identified as the primary reservoir for Polycyclic Aromatic Hydrocarbons in the United Kingdom. This study reviews the literature associated with, or is relevant to, the measurement and modelling of dermal absorption of Polycyclic Aromatic Hydrocarbons from soils. The literature illustrates the use of in vivo, in vitro and in silico methods from a wide variety of scientific disciplines including occupational and environmental exposure, medical, pharmaceutical and cosmetic research and associated mathematical modelling. The review identifies a number of practical shortcomings which must be addressed if dermal bioavailability tests are to be applied to laboratory analysis of contaminated soils for human health risk assessment.

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 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/m(3) 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.

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-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.

Impact of some field factors on inhalation exposure levels to bitumen emissions during road paving operations

Variability in occupational exposure levels to bitumen emissions has been observed during road paving operations. This is due to recurrent field factors impacting the level of exposure experienced by workers during paving. The present study was undertaken in order to quantify the impact of such factors. Pre-identified variables currently encountered in the field were monitored and recorded during paving surveys, and were conducted randomly covering current applications performed by road crews. Multivariate variance analysis and regressions were then used on computerized field data. The statistical investigations were limited due to the relatively small size of the study (36 data). Nevertheless, the particular use of the step-wise regression tool enabled the quantification of the impact of several predictors despite the existing collinearity between variables. The two bitumen organic fractions (particulates and volatiles) are associated with different field factors. The process conditions (machinery used and delivery temperature) have a significant impact on the production of airborne particulates and explain up to 44% of variability. This confirms the outcomes described by previous studies. The influence of the production factors is limited though, and should be complemented by studying factors involving the worker such as work style and the mix of tasks. The residual volatile compounds, being part of the bituminous binder and released during paving operations, control the volatile emissions; 73% of the encountered field variability is explained by the composition of the bitumen batch.

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

An exposure assessment of hot-mix asphalt (HMA) paving workers was conducted to determine which of four exposure scenarios impacted worker exposure and dose. Goals of this report are to present the personal-breathing zone (PBZ) data, discuss the impact of substituting the releasing/cleaning agent, and discuss work practices that resulted in the highest exposure concentration for each analyte. One-hundred-seven PBZ samples were collected from HMA paving workers on days when diesel oil was used as a releasing/cleaning agent. An additional 36 PBZ samples were collected on days when B-100 (100% biodiesel, containing no petroleum-derived products) was used as a substitute releasing/cleaning agent. Twenty-four PBZ samples were collected from a reference group of concrete workers, who also worked in outdoor construction but had no exposure to asphalt emissions. Background and field blank samples were also collected daily. Total particulates and the benzene soluble fraction were determined gravimetrically. Total organic matter was determined using gas chromatography (GC) with flame ionization detection and provided qualitative information about other exposure sources contributing to worker exposure besides asphalt emissions. Thirty-three individual polycyclic aromatic compounds (PACs) were determined using GC with time-of-flight mass spectrometry; results were presented as either the concentration of an individual PAC or a summation of the individual PACs containing either 2- to 3-rings or 4- to 6-rings. Samples were also screened for PACs containing 4- to 6-rings using fluorescence spectroscopy. Arithmetic means, medians, and box plots of the PBZ data were used to evaluate trends in the data. Box plots illustrating the diesel oil results were more variable than the B-100. Also, the highest diesel oil results were much higher in concentration than the highest B-100 results. An analysis of the highest exposure results and field notes revealed a probable association between these exposures and the use of diesel oil, use of a diesel-powered screed, elevated HMA paving application temperatures, lubricating and working on broken-down equipment, and operation of a broom machine.

Using urinary biomarkers of polycyclic aromatic compound exposure to guide exposure-reduction strategies among asphalt paving workers

INTRODUCTION

Paving workers are exposed to polycyclic aromatic compounds (PACs) while working with hot-mix asphalt (HMA). Further characterization of the source and route of these exposures is necessary to guide exposure-reduction strategies.

METHODS

Personal air (n=144), hand-wash (n=144), and urine (n=480) samples were collected from 12 paving workers over 3 workdays during 4 workweeks. Urine samples were collected at preshift, postshift, and bedtime and analyzed for 10 hydroxylated PACs (1-OH-pyrene; 1-, 2-, 3-, 4-OH-phenanthrene; 1-, 2-OH-naphthalene; 2-, 3-, 9-OH-fluorene) by an immunochemical quantification of PACs (I-PACs). The air and hand-wash samples were analyzed for the parent compounds corresponding to the urinary analytes. Using a crossover study design, each of the 4 weeks represented a different exposure scenario: a baseline week (normal conditions), a dermal protection week (protective clothing), a powered air-purifying respirator (PAPR) week, and a biodiesel substitution week (100% biodiesel provided to replace the diesel oil normally used by workers to clean tools and equipment). The urinary analytes were analyzed using linear mixed-effects models.

RESULTS

Postshift and bedtime concentrations were significantly higher than preshift concentrations for most urinary biomarkers. Compared with baseline, urinary analytes were reduced during the dermal protection (29% for 1-OH-pyrene, 15% for I-PACs), the PAPR (24% for 1-OH-pyrene, 15% for I-PACs), and the biodiesel substitution (15% for 1-OH-pyrene) weeks. The effect of PACs in air was different by exposure scenario (biodiesel substitution>dermal protection>PAPR and baseline) and was still a significant predictor of most urinary analytes during the week of PAPR use, suggesting that PACs in air were dermally absorbed. The application temperature of HMA was positively associated with urinary measures, such that an increase from the lowest application temperature (121°C) to the highest (154°C) was associated with a 72% increase in ΣOH-fluorene and 1-OH-pyrene and an 82% increase in ΣOH-phenanthrene. Though PACs in hand-wash samples were not predictors of urinary analytes, the effects observed during the PAPR scenario and the week of increased dermal protection provide evidence of dermal absorption.

CONCLUSIONS

Our results provide evidence that PACs in air are dermally absorbed. Reducing the application temperature of asphalt mix appears to be a promising strategy for reducing PAC exposure among paving workers. Additional reductions may be achieved by requiring increased dermal coverage of workers and by substituting biodiesel for diesel oil as a cleaning agent.