Exposure to carcinogenic polycyclic aromatic compounds and health risk assessment for diesel-exhaust exposed workers

Updating a diesel engine exhaust job-exposure matrix with published measurement data

A job-exposure matrix (JEM) is a tool that can estimate diesel engine exhaust (DEE) exposures. JEMs based on expert judgment or measurement data are limited by the information available at the time of development. Over time, more information about hazardous exposures is understood through additional measurements and peer-reviewed publications. This study presents a systematic approach to updating an existing DEE JEM using published data to better reflect current scientific knowledge. The literature was searched for occupational exposure studies that measured DEE as elemental carbon (EC) between January 2010 and May 2022. Four-digit North American Industry Classification System (NAICS) 2002 and National Occupational Classification-Statistics (NOC-S) 2006 codes were assigned to each identified subgroup within the studies. EC exposures were categorized as low (0-10 µg/m3), moderate (10-20 µg/m3), or high (>20 µg/m3). Weighted arithmetic means were calculated for each industry-occupation intersection (IOI) identified in the literature. These means were used to adjust, or retain, the existing exposure level within the JEM cells using a decision tree based on the number of studies, workplace locations, and pooled sample size of the weighted mean. Concordance was measured between the updated JEM (Diesel Exhaust in Canada JEM (DEC-JEM)), the previous (existing) JEM, and the Canadian Job-Exposure Matrix (CANJEM). Thirty-seven studies were identified from the published literature reporting on 53 unique IOIs (20 NAICS and 34 NOC-S codes), including occupations in the mining, construction, and transportation industries. Exposure levels for 66% of identified IOIs increased, most in construction and mining. After the decision tree's results were expanded to the full DEC-JEM, the exposure level of 486 IOIs (12.5% of DEC-JEM) and 286,710 workers (15.8% of DEE-exposed workers) increased. There was a significant correlation between qualitative exposure levels in the updated DEC-JEM and CANJEM (Kendall's τ = 0.364, p < 0.001). This study describes a systematic approach to updating an existing JEM to incorporate new scientific knowledge. The updated DEC-JEM better reflects existing exposure knowledge in several industries, particularly construction. Future analyses include investigating its use as an exposure assessment tool in disease surveillance.

Engineering Modular and Highly Sensitive Cell-Based Biosensors for Aromatic Contaminant Monitoring and High-Throughput Enzyme Screening

Although a variety of whole-cell-based biosensors have been developed for different applications in recent years, most cannot meet practical requirements due to insufficient sensing performance. Here, we constructed two sets of modular genetic circuits by serial and parallel modes capable of significantly amplifying the input/output signal in Escherichia coli. The biosensors are engineered using σ⁵⁴-dependent phenol-responsive regulator DmpR as a sensor and enhanced green fluorescent protein as a reporter. Cells harboring serial and parallel genetic circuits displayed nearly 9- and 16-fold higher sensitivity than the general circuit. The genetic circuits enabled rapid detection of six phenolic contaminants in 12 h and showed the low limit of detection of 2.5 and 2.2 ppb for benzopyrene (BaP) and tetracycline (Tet), with a broad detection range of 0.01-1 and 0.005-5 μM, respectively. Furthermore, the positive rate was as high as 73% when the biosensor was applied to screen intracellular enzymes with ester-hydrolysis activity from soil metagenomic libraries using phenyl acetate as a phenolic substrate. Several novel enzymes were isolated, identified, and biochemically characterized, including serine peptidases and alkaline phosphatase family protein/metalloenzyme. Consequently, this study provides a new signal amplification method for cell-based biosensors that can be widely applied to environmental contaminant assessment and screening of intracellular enzymes.

Occurrence, source apportionment, and carcinogenic risk assessment of polycyclic aromatic hydrocarbons in urban road dusts in Shanghai

Polycyclic aromatic hydrocarbons (PAHs), as a class of important environmental pollutants, have received considerable concern due to their widespread existence and biological toxicity. The main purpose of this study was to determine concentrations, spatial distribution, possible sources, and potential health risk of PAHs in urban road dust in Shanghai, China. The concentration of Σ₂₆PAHs ranged from 53.0 to 28,700 ng g^-1 in road dust samples from Shanghai, which is at the low to medium level compared with other areas around the world. PAHs with 4-5 rings were predominant components in road dust. The level of PAHs in road dust was significantly higher than those in soil and river sediment in Shanghai. Six possible sources of PAHs were apportioned by PMF model. The contribution of pyrogenic PAHs accounted for 91.3% of the total PAHs in road dusts. The motor vehicular emission, natural gas, and coal combustion were main sources for urban road dust PAHs from Shanghai. Four dibenzopyrene (DBP) isomers were contributed averagely 75% of total TEQ_BaP concentration. DBalP, BaP, DBaiP, BbF, and DBA were main contributors to total carcinogenic potency, which totally contributed from 69.6 to 91.8% (median 89.1%) to total TEQ_BaP in urban road dusts of Shanghai. The results of incremental lifetime carcinogenic risk (ILCR) assessment showed that the total risk values exposed to 24 PAHs in road dust were lower than 10^-4 at all sampling sites, indicating that exposure to dust-bound PAHs at present level was unlikely to result in high carcinogenic risk for both children and adults in Shanghai.

Diesel Engine Exhaust Exposure in the Ontario Civil Infrastructure Construction Industry

OBJECTIVES

Diesel engine exhaust (DEE) is a known lung carcinogen and a common occupational exposure in Canada. The use of diesel-powered equipment in the construction industry is particularly widespread, but little is known about DEE exposures in this work setting. The objective of this study was to determine exposure levels and identify and characterize key determinants of DEE exposure at construction sites in Ontario.

METHODS

Elemental carbon (EC, a surrogate of DEE exposure) measurements were collected at seven civil infrastructure construction worksites and one trades training facility in Ontario using NIOSH method 5040. Full-shift personal air samples were collected using a constant-flow pump and SKC aluminium cyclone with quartz fibre filters in a 37-mm cassette. Exposures were compared with published health-based limits, including the Dutch Expert Committee on Occupational Safety (DECOS) limit (1.03 µg m-3 respirable EC) and the Finnish Institute of Occupational Health (FIOH) recommendation (5 µg m-3 respirable EC). Mixed-effects linear regression was used to identify determinants of EC exposure.

RESULTS

In total, 149 EC samples were collected, ranging from <0.25 to 52.58 µg m-3 with a geometric mean (GM) of 3.71 µg m-3 [geometric standard deviation (GSD) = 3.32]. Overall, 41.6% of samples exceeded the FIOH limit, mostly within underground worksites (93.5%), and 90.6% exceeded the DECOS limit. Underground workers (GM = 13.20 µg m-3, GSD = 1.83) had exposures approximately four times higher than below grade workers (GM = 3.56 µg m-3, GSD = 1.94) and nine times higher than above ground workers (GM = 1.49 µg m-3, GSD = 1.75). Training facility exposures were similar to above ground workers (GM = 1.86 µg m-3, GSD = 4.12); however, exposures were highly variable. Work setting and enclosed cabins were identified as the key determinants of exposure in the final model (adjusted R2 = 0.72, P < 0.001). The highest DEE exposures were observed in underground workplaces and when using unenclosed cabins.

CONCLUSIONS

This study provides data on current DEE exposure in Canadian construction workers. Most exposures were above recommended health-based limits, albeit in other jurisdictions, signifying a need to further reduce DEE levels in construction. These results can inform a hazard reduction strategy including targeted intervention/control measures to reduce DEE exposure and the burden of occupational lung cancer.

7H-Dibenzo[c,g]carbazole: Metabolic pathways and toxicity

7H-Dibenzo[c,g]carbazole (DBC), a local and systemic carcinogen in animal studies, is a common environmental pollutant. It generally co-occurs in a variety of organic complex mixtures derived from incomplete combustion of organic matter. Despite high lipophilicity, DBC is more water-soluble and faster metabolized than the homocyclic aromatics. Moreover, greater polarity, high bioaccumulation potential, and persistence in the environment may imply DBC's higher biological significance and impact on human health, even at lower concentrations. The biotransformation pathways of DBC are incompletely known and the ultimate carcinogenic metabolite(s) are not clearly identified as yet. Structure-biological studies suggest two ways of activation: at the ring carbon atoms and at the pyrrole nitrogen. It is supposed that the particular pathway of biotransformation might be connected with the tissue/organ specificity of DBC. Cytochrome P450 (CYP) family of enzymes plays a pivotal role in the metabolism of DBC; though, the one-electron activation and the aldo-keto reductase-catalyzed oxidation are also involved in metabolic activation. Additionally, DBC can be photoactivated even at physiologically relevant doses of UVA light due to the extended aromatic ring system resulting in strong genotoxicity and oxidative stress. The goal of this review is to summarize current knowledge on mechanisms of DBC activation and possible implications for toxicity, genotoxicity, and carcinogenicity.

Biomonitoring of polycyclic aromatic hydrocarbons and synthetic musk compounds with Masson pine (Pinus massoniana L.) needles in Shanghai, China

Twenty-six polycyclic aromatic hydrocarbons (PAHs) and four synthetic musk compounds (SMCs) accumulated by Masson pine needles from different areas of Shanghai were investigated in the present study. Concentrations of Σ₂₆PAHs (sum of 26 PAHs) ranged from 234 × 10^-3 to 5370 × 10^-3 mg kg^-1. Levels of Σ₂₆PAHs in different sampling areas followed the order: urban areas (Puxi and Pudong) > suburbs > Chongming. Total concentrations of 16 USEPA priority PAHs ranged from 225 × 10^-3 to 5180 × 10^-3 mg kg^-1, ranking at a relatively high level compared to other regions around the world. Factor analysis and multi-linear regression model has identified six sources of PAHs with relative contributions of 15.1% for F1 (vehicle emissions), 47.8% for F2 (natural gas and biomass combustion), 7.8% for F3 (oil), 10.6% for F4 (coal combustion), 15.7% for F5 ("anthracene" source) and 3.0% for F6 (coke tar). Total concentrations of 4 SMCs varied between 0.071 × 10^-3 and 2.72 × 10^-3 mg kg^-1 in pine needles from Shanghai. SMCs with the highest detected frequency were Galaxolide and musk xylene, followed by musk ketone and Tonalide. The highest level of SMCs was found near industrial park and daily chemical plant. The results obtained from this study may have important reference value for local government in the control of atmospheric organic pollution.

Development of a novel aerosol generation system for conducting inhalation exposures to ambient particulate matter (PM)

In this study, we developed a novel method for generating aerosols that are representative of real-world ambient particulate matter (PM) in terms of both physical and chemical characteristics, with the ultimate objective of using them for inhalation exposure studies. The protocol included collection of ambient PM on filters using a high-volume sampler, which were then extracted with ultrapure Milli-Q water using vortexing and sonication. As an alternative approach for collection, ambient particles were directly captured into aqueous slurry samples using the versatile aerosol concentration enrichment system (VACES)/aerosol-into-liquid collector tandem technology. The aqueous samples from both collection protocols were then re-aerosolized using commercially available nebulizers. The physical characteristics (i.e., particle size distribution) of the generated aerosols were examined by the means of a scanning mobility particle sizer (SMPS) connected to a condensation particle counter (CPC) at different compressed air pressures of the nebulizer, and dilution air flow rates. In addition, the collected PM samples (both ambient and re-aerosolized) were chemically analyzed for water-soluble organic carbon (WSOC), elemental and organic carbon (EC/OC), inorganic ions, polycyclic aromatic hydrocarbons (PAHs), and metals and trace elements. Using the aqueous filter extracts, we were able to effectively recover the water-soluble components of ambient PM (e.g., water-soluble organic matter, and water-soluble inorganic ions); however, this method was deficient in recovering some of the important insoluble components such as EC, PAHs, and many of the redox-active trace elements and metals. In contrast, using the VACES/aerosol-into-liquid collector tandem technology for collecting ambient PM directly into water slurry, we were able to preserve the water-soluble and water-insoluble components very effectively. These results illustrate the superiority of the VACES/aerosol-into liquid collector tandem technology to be used in conjunction with the re-aerosolization setup to create aerosols that fully represent ambient PM, making it an attractive choice for application in inhalation exposure studies.

Source-specific lung cancer risk assessment of ambient PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) in central Tehran

In this study, source-specific cancer risk characterization of ambient PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) was performed in central Tehran. The positive matrix factorization (PMF) model was applied for source apportionment of PAHs in the area from May 2012 through May 2013. The PMF runs were carried out using chemically analyzed PAHs mass concentrations. Five factors were identified as the major sources of airborne PAHs in central Tehran, including petrogenic sources and petroleum residue, natural gas and biomass burning, industrial emissions, diesel exhaust emissions, and gasoline exhaust emissions, with approximately similar contributions of around 20% to total PAHs concentration from each factor. Results of the PMF source apportionment (i.e., PAHs factor profiles and contributions) were then used to calculate the source-specific lung cancer risks for outdoor and lifetime exposure, using the benzo[α]pyrene (BaP) equivalent method. Our risk assessment analysis indicated that the lung cancer risk associated with each specific source is within the range of 10^-6-10^-5, posing cancer risks exceeding the United States Environmental Protection Agency's (USEPA) guideline safety values (10^-6). Furthermore, the epidemiological lung cancer risk for lifetime exposure to total ambient PAHs was found to be (2.8 ± 0.78) × 10^-5. Diesel exhaust and industrial emissions were the two sources with major contributions to the overall cancer risk, contributing respectively to 39% and 27% of the total risk associated with exposure to ambient PAHs. Results from this study provide an estimate of the cancer risk caused by exposure to ambient PAHs in highly crowded areas in central Tehran, and can be used as a guide for the adoption of effective air quality policies in order to reduce the human exposure to these harmful organic species.

Diesel Exhaust Exposure Assessment Among Tunnel Construction Workers-Correlations Between Nitrogen Dioxide, Respirable Elemental Carbon, and Particle Number

Objectives

Occupational exposure to diesel exhaust is common due the widespread use of diesel-powered combustion engines. Diesel exhaust is chemically complex and consists of thousands of compounds present as gases and particulate matter. Both nitrogen dioxide (NO2) and elemental carbon (EC) have been used as markers for diesel exhaust exposure. Currently EC is regarded as the best surrogate of diesel exhaust. The objective was to quantify the occupational exposure to diesel exhaust in underground tunnel construction work using a multi-metric approach, and to investigate the correlations between NO2, respirable EC, respirable organic carbon (OC), respirable total carbon (TC), respirable dust (RD), and particle number. Also, the use of NO2 as a proxy for diesel exhaust was evaluated, how much of the variability in the diesel exhaust exposure was attributed to within and between individual factors and if there was a difference between expert and self-administered measurements of NO2.

Methods

The personal exposure to diesel exhaust was assessed by expert supervised measurements of NO2, EC, OC, TC, RD and particle number in the breathing zones of underground tunnel workers. Stationary sampling of NO2, EC, OC, TC, RD, size-fractioned mass concentration, and particle number were conducted. The personal and stationary measurements were conducted on three occasions simultaneously. The workers measured their exposure by repeated self-administered measurements of NO2. The self-administered measurements were performed twice for each worker with at least one month lag between the samplings.

Results

In the simultaneous sampling of diesel exhaust, the geometric mean (GM) concentration of NO2 and respirable EC were 72 µg m-3 (10th-90th percentile 34-140 µg m-3) and 2.6 µg m-3 (10th-90th percentile 1.6-7.3 µg m-3), respectively. The GM for OC and TC was 28 µg m-3 (10th-90th percentile 20-42 µg m-3) and 31 µg m-3 (10th-90th percentile 20-50 µg m-3), respectively. The GM for RD and particle number was 180 µg m-3 (10th-90th percentile 20-530 µg m-3) and 47 900 cm-3 (10th-90th percentile 27500-94100 cm-3), respectively. A significant correlation was found between NO2 and respirable EC [Spearman's correlation r = 0.53 (P = 0.05)]. The within-worker variability of NO2 was 45.5% and the between-worker variability was 54.5%. The self-administered measured concentrations of NO2 (GM 70 µg m-3) did not statistically differ from the NO2 concentrations measured by an expert (P > 0.35).

Conclusion

The diesel exhaust exposure in tunnel construction work was low. A significant correlation between NO2 and EC was observed. This indicates that NO2 could be used as a proxy for diesel exhaust in tunnel work if diesel exhaust is the only source of NO2 and if the ratio between EC and NO2 is known and constant. Passive sampling of NO2 is much easier and cheaper to perform compared with active sampling of EC. It is possible to utilize self-administered NO2 measurements in extreme and inaccessible work environments. This study adds support to continued use of NO2 as an exposure marker in combination with EC for diesel exhaust exposure. In tunnel construction work, the variability in the diesel exhaust exposure was high both between- and within-workers.

Distribution of coal and coal combustion related organic pollutants in the environment of the Upper Silesian Industrial Region

In this study, a large sample set (276) was separated into up to 15 groups, including coal, fly ash, total particulate matter, coal wastes, river sediments, and different water types. Grouping the sample set into these categories helped to identify the typical features of combustion or water-washing and compare them using newly developed polycyclic aromatic hydrocarbon diagnostic ratios. A wide range of organic pollutants were identified in samples, including aromatic and polycyclic hydrocarbons, nitrogen-heterocycles, sulphur-heterocycles + trithiolane, and polycyclic aromatic hydrocarbons substituted with oxygen functional groups. The distribution of compounds was significantly influenced by water washing or combustion. During the self-heating of coal wastes, secondary compounds such as chlorinated aromatics (chlorobenzene, chloroanthracene, etc.) or light sulphur compounds (e.g. benzenethiol and benzo[b]thiophene) were formed (synthesised). Since these compounds are generally absent in sedimentary organic matter, their origin may be connected with high-temperature formation in burning coal dumps. These compounds should be identified as persistent organic pollutants (POPs) in the environment. The newly defined diagnostic ratios have worked well in separating samples (petrogenic and pyrogenic) and have pointed out the effect of incomplete combustion on self-heated coal waste, ash from domestic furnaces, or water washing and biodegradation of the studied compounds.

Diesel engine exhaust exposure in underground mines: Comparison between different surrogates of particulate exposure

Exposure to diesel particulate matter (DPM) is frequently assessed by measuring indicators of carbon speciation, but these measurements may be affected by organic carbon (OC) interference. Furthermore, there are still questions regarding the reliability of direct-reading instruments (DRI) for measuring DPM, since these instruments are not specific and may be interfered by other aerosol sources. This study aimed to assess DPM exposure in 2 underground mines by filter-based methods and DRI and to assess the relationship between the measures of elemental carbon (EC) and the DRI to verify the association of these instruments to DPM. Filter-based methods of respirable combustible dust (RCD), EC, and total carbon (TC) were used to measure levels of personal and ambient DPM. For ambient measurements, DRI were used to monitor particle number concentration (PNC; PTrak), particle mass concentration (DustTrak DRX and DustTrak 8520), and the submicron fraction of EC (EC_1;Airtec). The association between ambient EC and the DRI was assessed by Spearman correlation. Geometric mean concentrations of RCD, respirable TC (TC_R) and respirable elemental EC (EC_R) were 170 µg/m³, 148 µg/m³, and 83 µg/m³ for personal samples, and 197 µg/m³, 151 µg/m³, and 100 µg/m³ for ambient samples. Personal measurements had higher TC_R:EC_R ratios compared to ambient samples (1.8 vs. 1.50) and weaker association between EC_R and TC_R. Among the DRI, the measures of EC₁ by the Airtec (ρ = 0.86; P < 0.001) and the respirable particles by the DustTrak 8520 (ρ = 0.74; P < 0.001) showed the strongest association with EC, while PNC showed a weak and non-significant association with EC. In conclusion, this study provided important information about the concentrations of DPM in underground mines by measuring several indicators using filter-based methods and DRI. Among the DRI, the Airtec proved to be a good tool for estimating EC concentrations and, although the DustTrak showed good association with EC, interferences from other aerosol sources should be considered when using this instrument to assess DPM.

Spatial variations, source apportionment and potential ecological risks of polycyclic aromatic hydrocarbons and synthetic musks in river sediments in Shanghai, China

The aims of this study were to investigate the levels, possible sources and potential ecological risks of 26 polycyclic aromatic hydrocarbons (PAHs) including highly carcinogenic dibenzopyrene (DBP) isomers and 4 synthetic musks (SMs) in river sediments from Shanghai. 74 sediment samples were collected from the Huangpu River and its main tributaries. The total concentrations ranged from 52.0 to 11400 ng g^-1 for Σ₂₆PAHs, 25.1-9910 ng g^-1 for 16 USEPA priority PAHs (Σ₁₆PAHs), 0.769-384 ng g^-1 for Σ₄DBPs, and 0.080-63.3 ng g^-1 for Σ₄SMs, respectively. Seven sources of PAHs in river sediments were identified by positive matrix factorization (PMF) model. Coal combustion, vehicle and creosote were the major emission sources for PAHs. SMs came mainly from domestic and industrial wastewaters. The toxic equivalent quantities of the benzo[a]pyrene (TEQ_BaP) ranged from 7.64 to 3920 ng g^-1 for Σ₂₄PAHs, 2.07-1150 ng g^-1 for Σ₁₆PAHs, and 5.53-3150 ng g^-1 for Σ₄DBPs. The TEQ_BaP of Σ₄DBPs made up 73.9% of Σ₂₄PAHs, which indicated that DBPs were the major carcinogenic contributors to total PAHs in sediments. According to sediment quality guidelines (SQGs) and mean PEL-Q values, the risks posed by PAHs in sediments were at medium level at most sampling sites, and SMs posed a low ecological risk to sediment-dwelling organisms in Shanghai.

Characterization of indoor diesel exhaust emissions from the parking garage of a school

Diesel exhaust (DE) emissions from a parking garage located in the basement of a school were characterized during spring and winter using direct reading devices and integrated sampling methods. Concentrations of CO and NO₂ were evaluated using electrochemical sensors and passive colorimetric tubes, respectively. Elemental and total carbon concentrations were measured using the NIOSH 5040 method. Particle number concentrations (PNCs), respirable particulate matter (PM_resp) mass concentrations, and size distributions were evaluated using direct reading devices. Indoor concentrations of elemental carbon, PNC, CO, and NO₂ showed significant seasonal variation; concentrations were much higher during winter (p < 0.01). Concentrations of the PM_resp and total carbon did not show significant seasonal variation. Pearson correlation coefficients were 0.9 (p < 0.01) and 0.94 (p < 0.01) between the parking garage and ground floor average daily PNCs, and between the parking garage and first floor average daily PNCs, respectively. Since DE is the main identified source of fine and ultrafine particles in the school, these results suggest that DE emissions migrate from the parking garage into the school. Our results highlight the relevance of direct reading instruments in identifying migration of contaminants and suggest that monitoring PNC is a more specific way of assessing exposure to DE than monitoring the common PM_resp fraction.

Diesel exhaust exposures in port workers

Exposure to diesel engine exhaust has been linked to increased cancer risk and cardiopulmonary diseases. Diesel exhaust is a complex mixture of chemical substances, including a particulate fraction mainly composed of ultrafine particles, resulting from the incomplete combustion of fuel. Diesel trucks are known to be an important source of diesel-related air pollution, and areas with heavy truck traffic are associated with higher air pollution levels and increased public health problems. Several indicators have been proposed as surrogates for estimating exposures to diesel exhaust but very few studies have focused specifically on monitoring the ultrafine fraction through the measurement of particle number concentrations. The aim of this study is to assess occupational exposures of gate controllers at the port of Montreal, Canada, to diesel engine emissions from container trucks by measuring several surrogates through a multimetric approach which includes the assessment of both mass and number concentrations and the use of direct reading devices. A 10-day measurement campaign was carried out at two terminal checkpoints at the port of Montreal. Respirable elemental and organic carbon, PM1, PM2.5, PMresp (PM4), PM10, PMtot (inhalable fraction), particle number concentrations, particle size distributions, and gas concentrations (NO2, NO, CO) were monitored. Gate controllers were exposed to concentrations of contaminants associated with diesel engine exhaust (elemental carbon GM = 1.6 µg/m(3); GSD = 1.6) well below recommended occupational exposure limits. Average daily particle number concentrations ranged from 16,544-67,314 particles/cm³ (GM = 32,710 particles/cm³; GSD = 1.6). Significant Pearson correlation coefficients were found between daily elemental carbon, PM fractions and particle number concentrations, as well as between total carbon, PM fractions and particle number concentrations. Significant correlation coefficients were found between particle number concentrations and the number of trucks and wind speed (R(2) = 0.432; p < 0.01). The presence of trucks with cooling systems and older trucks with older exhaust systems was associated with peak concentrations on the direct reading instruments. The results highlight the relevance of direct reading instruments in helping to identify sources of exposure and suggest that monitoring particle number concentrations improves understanding of workers' exposures to diesel exhaust. This study, by quantifying workers' exposure levels through a multimetric approach, contributes to the further understanding of occupational exposures to diesel engine exhaust.

Evaluation of the reactivity of exhaust from various biodiesel blends as a measure of possible oxidative effects: A concern for human exposure

Diesel exhaust particles (DEP) are a major constituent of ambient air pollution and are associated with various adverse health effects, posing a major safety and public health concern in ambient and occupational environments. The effects of DEP from various biodiesel blends on biological systems was investigated using glutathione (GSH) as a marker of possible oxidative effects, based on the decrease in the concentration of GSH at physiological pH. The fluorophoric agent 2,3-naphthalenedicarboxaldehyde (NDA) was used as a selective probe of GSH in the presence of any likely interferents via fluorescence detection. Three different polar solvents (acetonitrile, methanol and water) were used to extract DEP generated during the combustion of different biodiesel blends (5%-99%). Oxidation of GSH to the disulfide (GSSG) was confirmed using electrospray ionization mass spectrometry. A decrease in the concentration of GSH was observed in the presence of DEP extracts from all of the biodiesel blends studied, with reaction rates that depend on the biodiesel blend. Interestingly the reactivity peaked at 50% biodiesel (B50) rather than decreasing monotonically with increased biodiesel content, as was expected. Organic solvent DEP extracts showed wider variations in reactivity with GSH, with methanol extracts giving the largest decrease in GSH concentrations. This may imply a more organic nature of the oxidants in the biodiesel exhaust. It is therefore important to consider ways of reducing concentrations of organic components in biodiesel exhaust that can cause different toxic activity before any blend is offered as a preferred alternative to petroleum diesel fuel.

Adsorption of naphthalene onto high-surface-area nanoparticle loaded activated carbon by high performance liquid chromatography: response surface methodology, isotherm and kinetic study

Naphthalene removal from aqueous solution was investigated using zinc sulfide nanoparticle loaded activated carbon (ZnS-NPs-AC).

Statistical Modeling of Occupational Exposure to Polycyclic Aromatic Hydrocarbons Using OSHA Data

Polycyclic aromatic hydrocarbons (PAHs) are a group of pollutants with multiple variants classified as carcinogenic. The Occupational Safety and Health Administration (OSHA) provided access to two PAH exposure databanks of United States workplace compliance testing data collected between 1979 and 2010. Mixed-effects logistic models were used to predict the exceedance fraction (EF), i.e., the probability of exceeding OSHA's Permissible Exposure Limit (PEL = 0.2 mg/m3) for PAHs based on industry and occupation. Measurements of coal tar pitch volatiles were used as a surrogate for PAHs. Time, databank, occupation, and industry were included as fixed-effects while an identifier for the compliance inspection number was included as a random effect. Analyses involved 2,509 full-shift personal measurements. Results showed that the majority of industries had an estimated EF < 0.5, although several industries, including Standardized Industry Classification codes 1623 (Water, Sewer, Pipeline, and Communication and Powerline Construction), 1711 (Plumbing, Heating, and Air-Conditioning), 2824 (Manmade Organic Fibres), 3496 (Misc. Fabricated Wire products), and 5812 (Eating Places), and Major group's 13 (Oil and Gas Extraction) and 30 (Rubber and Miscellaneous Plastic Products), were estimated to have more than an 80% likelihood of exceeding the PEL. There was an inverse temporal trend of exceeding the PEL, with lower risk in most recent years, albeit not statistically significant. Similar results were shown when incorporating occupation, but varied depending on the occupation as the majority of industries predicted at the administrative level, e.g., managers, had an estimated EF < 0.5 while at the minimally skilled/laborer level there was a substantial increase in the estimated EF. These statistical models allow the prediction of PAH exposure risk through individual occupational histories and will be used to create a job-exposure matrix for use in a population-based case-control study exploring PAH exposure and breast cancer risk.

Occurrence, sources and health risk assessment of polycyclic aromatic hydrocarbons in urban (Pudong) and suburban soils from Shanghai in China

A comprehensive investigation was conducted to the urban (Pudong) and suburban soils in Shanghai. A total of 154 soil samples were analyzed for 26 PAHs including highly carcinogenic dibenzopyrenes (DBPs). The total concentrations ranged from 25.8 to 7380 μg kg(-1) for Σ26PAHs and 18.8 to 6320 μg kg(-1) for 16 USEPA priority PAHs (Σ16PAHs), respectively. The BaP toxic equivalent (BaPeq) concentrations were between 6.41 and 2880 μg kg(-1) for Σ24PAHs, 1.11 and 620 μg kg(-1) for Σ16PAHs and 2.72 and 2250 μg kg(-1) for Σ4DBPs. The high PAH contamination in green land soils might originate mainly from local road traffic and industrial activities, and sewage sludge application or waste water irrigation for soil. Seven sources of soil PAHs in Shanghai were identified by positive matrix factorization (PMF) model. The mean risk quotient (m-RQ) values indicated that there were medium to high ecological risks in 9.10% of soil samples, pyrene (Pyr), benzo[b]fluoranthene (BbF) and benz[a]anthracene (BaA) were the major ecological risk drivers under agricultural use. The cancer risk (CR) values were within the acceptable range at 35.7%, 35.1% and 31.2% of sampling sites for children, youths and adults, respectively. The total lifetime carcinogenic risk (TLCR) values at 57.8% of sampling sites were within the acceptable range. Overall, cancer risks of soil PAHs in all sampling sites in the studied area were below the highest acceptable risk, suggesting that soil PAHs are unlikely to pose a significant cancer risk for population based on ingestion, dermal contact and inhalation exposure pathways.

Factors and Trends Affecting the Identification of a Reliable Biomarker for Diesel Exhaust Exposure

The monitoring of human exposures to diesel exhaust continues to be a vexing problem for specialists seeking information on the potential health effects of this ubiquitous combustion product. Exposure biomarkers have yielded a potential solution to this problem by providing a direct measure of an individual's contact with key components in the exhaust stream. Spurred by the advent of new, highly sensitive, analytical methods capable of detecting substances at very low levels, there have been numerous attempts at identifying a stable and specific biomarker. Despite these new techniques, there is currently no foolproof method for unambiguously separating diesel exhaust exposures from those arising from other combustion sources. Diesel exhaust is a highly complex mixture of solid, liquid, and gaseous components whose exact composition can be affected by many variables, including engine technology, fuel composition, operating conditions, and photochemical aging. These factors together with those related to exposure methodology, epidemiological necessity, and regulatory reform can have a decided impact on the success or failure of future research aimed at identifying a suitable biomarker of exposure. The objective of this review is to examine existing information on exposure biomarkers for diesel exhaust and to identify those factors and trends that have had an impact on the successful identification of metrics for both occupational and community settings. The information will provide interested parties with a template for more thoroughly understanding those factors affecting diesel exhaust emissions and for identifying those substances and research approaches holding the greatest promise for future success.

Characterization of occupational exposure to air contaminants in modern tunnelling operations

OBJECTIVES

Personal air measurements of aerosols and gases among tunnel construction workers were performed as part of a 11-day follow-up study on the relationship between exposure to aerosols and gases and cardiovascular and respiratory effects.

METHODS

Ninety tunnel construction workers employed at 11 available construction sites participated in the exposure study. The workers were divided into seven job groups according to tasks performed. Exposure measurements were carried out on 2 consecutive working days prior to the day of health examination. Summary statistics were computed using maximum likelihood estimation (MLE), and the procedure NLMIXED and LIFEREG in SAS was used to perform MLE for repeated measures data subject to left censoring and for calculation of within- and between-worker variance components.

RESULTS

The geometric mean (GM) air concentrations for the thoracic mass aerosol sub-fraction, α-quartz, oil mist, organic carbon (OC), and elemental carbon (EC) for all workers were 561, 63, 210, 146, and 35.2 μg m(-3), respectively. Statistical differences of air concentrations between job groups were observed for all contaminants, except for OC, EC, and ammonia (P > 0.05). The shaft drillers, injection workers, and shotcreting operators were exposed to the highest GM levels of thoracic dust (7061, 1087, and 865 μg m(-) (3), respectively). The shaft drillers and the support workers were exposed to the highest GM levels of α-quartz (GM = 844 and 118 μg m(-3), respectively). Overall, the exposure to nitrogen dioxide and ammonia was low (GM = 120 and 251 μg m(-) (3), respectively).

CONCLUSIONS

Findings from this study show significant differences between job groups with shaft drilling as the highest exposed job to air concentrations for all measured contaminants. Technical interventions in this job should be implemented to reduce exposure levels. Overall, diesel exhaust air concentrations seem to be lower than previously assessed (as EC).

PAH fluxes to Siskiwit revisted: trends in fluxes and sources of pyrogenic PAH and perylene constrained via radiocarbon analysis

Trends in concentrations and radiocarbon content of pyrogenic PAHs and perylene were determined 20 years after a previous study by Mcveety and Hites (1988). Pyrogenic PAH fluxes to sediments were observed to continue to decrease over the period from 1980 to 2000 at this remote site in contrast to observations in more urban areas. Radiocarbon analysis of pyrogenic PAHs showed a 50% decrease in the proportion of pyrogenic PAH derived from fossil fuel combustion over the past 50 years, consistent with decreasing emissions from regional coal-fired power-generating plants. Fluxes of pyrogenic PAHs related to biomass burning were consistent over this same period and found to exceed fossil fuel sources in the most recent samples. Fluxes of biomass-derived pyrogenic PAHs were similar in magnitude to total pyrogenic PAH fluxes in early 1900, suggesting that these fluxes may represent wildfire inputs. Not only did perylene concentrations in these sediments increase with depth as previously observed but also concentrations from the same sedimentary layers analyzed 20 years previously showed large increases in perylene concentrations. Radiocarbon analysis of perylene indicated that 70-85% of perylene observed in the deeper sediments could be explained by production from total organic carbon.

Polycyclic aromatic hydrocarbons (PAHs) in urban soils of the megacity Shanghai: occurrence, source apportionment and potential human health risk

A comprehensive investigation was conducted to the urban soil in the megacity Shanghai in order to assess the levels of PAHs and potential risks to human health, to identify and quantitatively assess source contributions to the soil PAHs. A total of 57 soil samples collected in main urban areas of Shanghai, China were analyzed for 26 PAHs including highly carcinogenic dibenzopyrene isomers. The total concentrations ranged from 133 to 8,650 ng g for ΣPAHs and 83.3 to 7,220 ng g for ΣPAHs, with mean values of 2420 and 1,970 ng g, respectively. DBalP and DBaeP may serve as markers for diesel vehicle emission, while DBahP is a probable marker of coke tar as distinct from diesel emissions. Six sources in Shanghai urban area were identified by PMF model; their relative contributions to the total soil PAH burden were 6% for petrogenic sources, 21% for coal combustion, 13% for biomass burning, 16% for creosote, 23% for coke tar related sources and 21% for vehicular emissions, respectively. The benzo[a]pyrene equivalent (BaP) concentrations ranged from 48.9-2,580 ng g for ΣPAHs, 7.02-869 ng g for ΣPAHs and 35.7-1,990 ng g for ΣDBPs. The BaP concentrations of ΣDBPs made up 72% of ΣPAHs. Nearly half of the soil samples showed concentrations above the safe BaP value of 600 ng g. Exposure to these soils through direct contact probably poses a significant risk to human health from carcinogenic effects of soil PAHs. The index of additive cancer risk (IACR) values in almost one third of urban soil samples were more than the safe value of 1.0, indicating these urban soil PAHs in the study area may pose a potential threat to potable groundwater water quality from leaching of carcinogenic PAH mixtures from soil.

A comparative assessment of PM2.5 exposures in light-rail, subway, freeway, and surface street environments in Los Angeles and estimated lung cancer risk

According to the U.S. Census Bureau, 570000+ commuters in Los Angeles travel for over 60 minutes to work. Studies have shown that a substantial portion of particulate matter (PM) exposure can occur during this commute. This study represents the integration of the results from five commute environments in Los Angeles. Personal PM exposures are discussed for the: (1) METRO gold line, a ground-level light-rail route, (2) METRO red line, a subway line, (3) the 110, a high volume freeway with low heavy-duty vehicle (HDV) fraction, (4) the 710, a major corridor for HDVs from the Port of Los Angeles, and (5) Wilshire/Sunset Boulevards, major surface streets. Chemical analysis including total and water-soluble metals and trace elements, elemental and organic carbon (EC/OC), and polycyclic aromatic hydrocarbons (PAHs) was performed. The focus of this study is to compare the composition and estimated lung cancer risk of PM2.5 (dp < 2.5 μm) for the five differential commute environments. Metals associated with stainless steel, notably Fe, Cr, and Mn, were elevated for the red line (subway), most likely from abrasion processes between the rail and brakes; elements associated with tire and brake wear and oil additives (Ca, Ti, Sn, Sb, and Pb) were elevated on roadways. Elemental concentrations on the gold line (light-rail) were the lowest. For water-solubility, metals observed on the red line (subway) were the least soluble. PAHs are primarily derived from vehicular emissions. Overall, the 710 exhibited high levels of PAHs (3.0 ng m−3), most likely due to its high volume of HDVs, while the red and gold lines exhibited low PAH concentrations (0.6 and 0.8 ng m−3 for red and gold lines, respectively). Lastly, lung cancer risk due to inhalation of PAHs was calculated based on a commuter lifetime (45 years for 2 hours per workday). Results showed that lung cancer risk for the 710 is 3.8 and 4.5 times higher than the light-rail (gold line) and subway (red line), respectively. With low levels of both metal and PAH pollutants, our results indicate that commuting on the light-rail (gold line) may have potential health benefits when compared to driving on freeways and busy roadways.

Generation of polycyclic aromatic hydrocarbons (PAHs) during woodworking operations

Occupational exposures to wood dust have been associated with an elevated risk of sinonasal cancer (SNC). Wood dust is recognized as a human carcinogen but the specific cancer causative agent remains unknown. One possible explanation is a co-exposure to; wood dust and polycyclic aromatic hydrocarbons (PAHs). PAHs could be generated during incomplete combustion of wood due to heat created by use of power tools. To determine if PAHs are generated from wood during common wood working operations, PAH concentrations in wood dust samples collected in an experimental chamber operated under controlled conditions were analyzed. In addition, personal air samples from workers exposed to wood dust (n = 30) were collected. Wood dust was generated using three different power tools: vibrating sander, belt sander, and saw; and six wood materials: fir, Medium Density Fiberboard (MDF), beech, mahogany, oak and wood melamine. Monitoring of wood workers was carried out by means of personal sampler device during wood working operations. We measured 21 PAH concentrations in wood dust samples by capillary gas chromatography-ion trap mass spectrometry (GC-MS). Total PAH concentrations in wood dust varied greatly (0.24-7.95 ppm) with the lowest being in MDF dust and the highest in wood melamine dust. Personal PAH exposures were between 37.5-119.8 ng m(-3) during wood working operations. Our results suggest that PAH exposures are present during woodworking operations and hence could play a role in the mechanism of cancer induction related to wood dust exposure.

Determination of benzo[a]pyrene and dibenzopyrenes in a Chinese coal fly ash certified reference material

Air pollution from coal combustion is of great concern in China because coal is the country's principal source of energy and it has been estimated that coal combustion is one of the main sources of polycyclic aromatic hydrocarbon (PAH) emissions in the nation. This study reports the concentrations of 15 PAHs including benzo[a]pyrene, dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene in a coal fly ash certified reference material (CRM) from China. To the best of our knowledge, dibenzo[a,l]pyrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene concentrations in coal fly ash particles have not previously been reported. Benzo[a]pyrene is the only one of the studied hydrocarbons whose concentration in the coal fly ash CRM had previously been certified. The concentration of this species measured in this present work was twice the certified value. This is probably because of the exhaustive accelerated solvent extraction method employed. Consecutive extractions indicated an extraction recovery in excess of 95% for benzo[a]pyrene. For the other determined PAHs, repeat extractions indicated recoveries above 90%.

Modern and fossil contributions to polycyclic aromatic hydrocarbons in PM₂.₅ from North Birmingham, Alabama in the southeastern U.S

Analyzing the radiocarbon ((14)C) content of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate matter can provide estimates on the source contributions from biomass burning versus fossil fuel. The relative importance of these two sources to ambient PAHs varies considerably across regions and even countries, and hence there is a pressing need to apportion these sources. In this study, we advanced the radiocarbon analysis from bulk carbon to compound class specific radiocarbon analysis (CCSRA) to determine Δ(14)C and δ(13)C values of PAHs in PM(2.5) samples for investigating biomass burning and fossil fuel source contributions to PAHs from one of the Southeastern Aerosol Research and Characterization (SEARCH) sites in North Birmingham (BHM), Alabama during winter (December 2004-February 2005) and summer (June-August 2005) by accelerator mass spectrometry. To compare our ambient samples to known sources, we collected and analyzed fenceline samples from the vicinity of a coke plant in BHM. As expected, PAHs from the coke plant fenceline samples had very low radiocarbon levels. Its Δ(14)C varied from -990 to -970‰, indicating that 97 to 99% were of fossil source. PAHs in the ambient PM(2.5) had Δ(14)C from -968 to -911 ‰, indicating that 92-97% of PAHs were from fossil fuel combustion. These levels indicated the dominance of fossil sources of ambient PAHs. The radiocarbon level of ambient PAHs was higher in winter than in summer. Winter samples exhibited depleted δ(13)C value and enriched Δ(14)C value because of the increased contribution of PAHs from biomass burning source. However, biomass burning contributed more to heavier PAHs (modern source accounting for 6-8%) than lighter ones with a modern contribution of 3%.

Polycyclic aromatic hydrocarbons with molecular weight 302 in PM 2.5 at two industrial sites in South China

Daytime and nighttime PM(2.5) samples were collected between August 5 and 16, 2009 and between January 24 and February 4, 2010 in an industrial complex site (site A) and an electronic waste recycling site (site B) to determine the seasonal and diurnal variations of 19 individual polycyclic aromatic hydrocarbons (PAHs) with molecular weight 302 (MW302) including four highly carcinogenic dibenzopyrene (DBP) isomers dibenzo[a,l]pyrene (DBalP), dibenzo[a,e]pyrene (DBaeP), dibenzo[a,i]pyrene (DBaiP), and dibenzo[a,h]pyrene (DBahP). This is the first report on DBP isomers in air particles from South China. The total concentration of PAH MW302 isomers ranged from 1.65 to 3.60 ng m(-3) in summer and 3.82 to 9.81 ng m(-3) in winter. The strongest peaks in the chromatograms of the MW302 isomers were naphtha[2,1-a]pyrene (N21aP), dibenzo[j,l]fluoranthene (DBjlF), naphtha[1,2-b]fluoranthene (N12bF), naphtha[1,2-k]fluoranthene (N12kF) and dibenzo[a,e]fluoranthene (DBaeF), constituting 52.0 to 55.4% of the total MW302 isomers. All the MW302 isomers showed notable seasonal variations. Most of the MW302 isomers in site B showed distinctive diurnal variations with higher concentrations occurring in the night. Taking into account both concentration and potency equivalence factors (PEFs), the strongest carcinogen in the analyzed samples was DBaiP, and the ratios of sum carcinogenic potency of four highly carcinogenic DBP isomers to benzo[a]pyrene (BaP) was about 0.94 in winter to 1.89 in summer, indicating the importance of DBP isomers for the risk assessment. Health risk assessment indicated that on average, 1 in 100 000 residents in the two industrial sites may have an increased risk of cancer due to PAH exposure.

Biomarkers of oxidative stress and its association with the urinary reducing capacity in bus maintenance workers

BACKGROUND

Exposure to particles (PM) induces adverse health effects (cancer, cardiovascular and pulmonary diseases). A key-role in these adverse effects seems to be played by oxidative stress, which is an excess of reactive oxygen species relative to the amount of reducing species (including antioxidants), the first line of defense against reactive oxygen species. The aim of this study was to document the oxidative stress caused by exposure to respirable particles in vivo, and to test whether exposed workers presented changes in their urinary levels for reducing species.

METHODS

Bus depot workers (n = 32) exposed to particles and pollutants (respirable PM4, organic and elemental carbon, particulate metal content, polycyclic aromatic hydrocarbons, NOx, O3) were surveyed over two consecutive days. We collected urine samples before and after each shift, and quantified an oxidative stress biomarker (8-hydroxy-2'-deoxyguanosine), the reducing capacity and a biomarker of PAH exposure (1-hydroxypyrene). We used a linear mixed model to test for associations between the oxidative stress status of the workers and their particle exposure as well as with their urinary level of reducing species.

RESULTS

Workers were exposed to low levels of respirable PM4 (range 25-71 μg/m3). However, urinary levels of 8-hydroxy-2'-deoxyguanosine increased significantly within each shift and between both days for non-smokers. The between-day increase was significantly correlated (p < 0.001) with the concentrations of organic carbon, NOx, and the particulate copper content. The within-shift increase in 8OHdG was highly correlated to an increase of the urinary reducing capacity (Spearman ρ = 0.59, p < 0.0001).

CONCLUSIONS

These findings confirm that exposure to components associated to respirable particulate matter causes a systemic oxidative stress, as measured with the urinary 8OHdG. The strong association observed between urinary 8OHdG with the reducing capacity is suggestive of protective or other mechanisms, including circadian effects. Additional investigations should be performed to understand these observations.

Effect of dibenzopyrene measurement on assessing air quality in Beijing air and possible implications for human health

Size fractionated particulate matter (PM) was collected in summer and winter from Beijing, China for the characterization of an expanded list of PAHs and evaluation of air pollution metrics. Summertime ΣPAHs on PM was 14.6 ± 29(PM 1.5), 0.88 ± 0.49(PM 1.5-7.2) and 0.29 ± 0.076(PM 7.2) ng m(-3) air while wintertime concentrations were 493 ± 206(PM 1.5), 26.7 ± 14(PM 1.5-7.2) and 5.3 ± 2.5(PM 7.2) ng m(-3) air. Greater than 90% of the carcinogenic PAHs were concentrated on PM(1.5). Dibenzopyrene isomers made up a significant portion (∼30%) of the total carcinogenic PAH load during the winter. To our knowledge, this is the first report of dibenzopyrenes in the Beijing atmosphere and among the few studies that report these highly potent PAHs in ambient particulate matter. Lifetime risk calculations indicated that 1 out of 10,000 to over 6 out of 100 Beijing residents may have an increased risk of lung cancer due to PAH concentration. Over half of the lifetime risk was attributed to Σdibenzopyrenes. The World Health Organization and Chinese daily PM(10) standard was exceeded on each day of the study, however, PAH limits were only exceeded during the winter. The outcomes of the air pollution metrics were highly dependent on the individual PAHs measured and seasonal variation.

The diesel exhaust in miners study: I. Overview of the exposure assessment process

This report provides an overview of the exposure assessment process for an epidemiologic study that investigated mortality, with a special focus on lung cancer, associated with diesel exhaust (DE) exposure among miners. Details of several components are provided in four other reports. A major challenge for this study was the development of quantitative estimates of historical exposures to DE. There is no single standard method for assessing the totality of DE, so respirable elemental carbon (REC), a component of DE, was selected as the primary surrogate in this study. Air monitoring surveys at seven of the eight study mining facilities were conducted between 1998 and 2001 and provided reference personal REC exposure levels and measurements for other agents and DE components in the mining environment. (The eighth facility had closed permanently prior to the surveys.) Exposure estimates were developed for mining facility/department/job/year combinations. A hierarchical grouping strategy was developed for assigning exposure levels to underground jobs [based on job titles, on the amount of time spent in various areas of the underground mine, and on similar carbon monoxide (CO, another DE component) concentrations] and to surface jobs (based on the use of, or proximity to, diesel-powered equipment). Time trends in air concentrations for underground jobs were estimated from mining facility-specific prediction models using diesel equipment horsepower, total air flow rates exhausted from the underground mines, and, because there were no historical REC measurements, historical measurements of CO. Exposures to potentially confounding agents, i.e. respirable dust, silica, radon, asbestos, and non-diesel sources of polycyclic aromatic hydrocarbons, also were assessed. Accuracy and reliability of the estimated REC exposures levels were evaluated by comparison with several smaller datasets and by development of alternative time trend models. During 1998-2001, the average measured REC exposure level by facility ranged from 40 to 384 μg m⁻³ for the underground workers and from 2 to 6 μg m⁻³ for the surface workers. For one prevalent underground job, 'miner operator', the maximum annual REC exposure estimate by facility ranged up to 685% greater than the corresponding 1998-2001 value. A comparison of the historical CO estimates from the time trend models with 1976-1977 CO measurements not used in the modeling found an overall median relative difference of 29%. Other comparisons showed similar levels of agreement. The assessment process indicated large differences in REC exposure levels over time and across the underground operations. Method evaluations indicated that the final estimates were consistent with those from alternative time trend models and demonstrated moderate to high agreement with external data.

Lung cancer and diesel exhaust: a critical review of the occupational epidemiology literature

The diesel exhaust (DE)-lung cancer hypothesis is evaluated. Diesel power became common after World War II, exposure was to traditional diesel exhaust (TDE) before 1988. In the next, 20 years, emissions were modified to new-technology diesel exhaust (NTDE) containing 1% of pre-1988 levels of diesel particulate matter (DPM). Nearly all pre-1990 studies were cohorts with primarily pre-diesel exposures. This review focuses on the proportion of cases with >20 years since initial DE exposure; strength of association; biological gradients; roles of chance, bias, and confounding; and consistency in 13 diesel studies. Five studies had adequate latency, six had a minority of workers with >20 years' latency, and in two studies most workers had inadequate latency. This pattern suggests too few relevant studies for evaluating the DE-lung cancer hypothesis. The 16 highest exposure categories showed 7 with probable associations (relative risk [RR] > 1.5), 7 with improbable or no associations (RRs < 1.2), and 2 with possible associations (RRs 1.2-1.5). This random pattern with many weak RRs does not support the DE-lung cancer hypothesis. Ten of 34 exposure-response (E-R) analyses showed positive trends and 24 had indeterminate or negative trends. This small number of positive biological gradients does not support causality. Weight of evidence suggests 70% of studies are indeterminate, whereas 30% are positive or negative, indicating a lack of consistency. To support a traditional diesel exhaust-lung cancer hypothesis requires more studies with longer follow-up and quantitative E-R analyses.

Do Standard Risk Assessment Procedures Adequately Account for Cumulative Risks?

Existing risk assessment data and procedures can be used to address the estimation of cumulative risk, but there are several uncertainties. These are explored in the context of the State of California’s Air Toxic Hot Spots program. Hazard identification for single agents is an established procedure but is much more complex for incompletely characterized or variable mixtures. Hazards from exposure to multiple agents are often only identified by chance. Similar concerns affect dose-response assessment. Although additivity is assumed by default for similar effects at low doses, exceptions are known for specific mixtures and for higher dose rates. Exposure assessment is especially complex for multiple sources, multiple agents from different sources, and target populations or individuals who face cumulative, but not necessarily simultaneous, impacts. With these contributory uncertainties, providing an integrated analysis that can inform risk management and presenting this to a diverse and often already stressed community are challenging.

Occupational exposure to diesel engine exhaust: a literature review

Diesel exhaust (DE) is classified as a probable human carcinogen. Aims were to describe the major occupational uses of diesel engines and give an overview of personal DE exposure levels and determinants of exposure as reported in the published literature. Measurements representative of personal DE exposure were abstracted from the literature for the following agents: elemental carbon (EC), particulate matter (PM), carbon monoxide (CO), nitrogen oxide (NO), and nitrogen dioxide (NO(2)). Information on determinants of exposure was abstracted. In total, 3528 EC, 4166 PM, 581 CO, 322 NO, and 1404 NO(2) measurements were abstracted. From the 10,001 measurements, 32% represented exposure from on-road vehicles and 68% from off-road vehicles (30% mining, 15% railroad, and 22% others). Highest levels were reported for enclosed underground work sites in which heavy equipment is used: mining, mine maintenance, and construction (EC: 27-658 microg/m(3)). Intermediate exposure levels were generally reported for above-ground (semi-) enclosed areas in which smaller equipment was run: mechanics in a shop, emergency workers in fire stations, distribution workers at a dock, and workers loading/unloading inside a ferry (generally: EC<50 microg/m(3)). Lowest levels were reported for enclosed areas separated from the source, such as drivers and train crew, or outside, such as surface mining, parking attendants, vehicle testers, utility service workers, surface construction and airline ground personnel (EC<25 microg/m(3)). The other agents showed a similar pattern. Determinants of exposure reported for enclosed situations were ventilation and exhaust after treatment devices. Reported DE exposure levels were highest for underground mining and construction, intermediate for working in above-ground (semi-) enclosed areas and lowest for working outside or separated from the source. The presented data can be used as a basis for assessing occupational exposure in population-based epidemiological studies and guide future exposure assessment efforts for industrial hygiene and epidemiological studies.

The generation of diesel exhaust particle aerosols from a bulk source in an aerodynamic size range similar to atmospheric particles

The influence of diesel exhaust particles (DEP) on the lungs and heart is currently a topic of great interest in inhalation toxicology. Epidemiological data and animal studies have implicated airborne particulate matter and DEP in increased morbidity and mortality due to a number of cardiopulmonary diseases including asthma, chronic obstructive pulmonary disorder, and lung cancer. The pathogeneses of these diseases are being studied using animal models and cell culture techniques. Real-time exposures to freshly combusted diesel fuel are complex and require significant infrastructure including engine operations, dilution air, and monitoring and control of gases. A method of generating DEP aerosols from a bulk source in an aerodynamic size range similar to atmospheric DEP would be a desirable and useful alternative. Metered dose inhaler technology was adopted to generate aerosols from suspensions of DEP in the propellant hydrofluoroalkane 134a. Inertial impaction data indicated that the particle size distributions of the generated aerosols were trimodal, with count median aerodynamic diameters less than 100 nm. Scanning electron microscopy of deposited particles showed tightly aggregated particles, as would be expected from an evaporative process. Chemical analysis indicated that there were no major changes in the mass proportion of 2 specific aromatic hydrocarbons (benzo[a]pyrene and benzo[k]fluoranthene) in the particles resulting from the aerosolization process.

Identification and determination of highly carcinogenic dibenzopyrene isomers in air particulate samples from a street canyon, a rooftop, and a subway station in Stockholm

This study presents determined levels of the highly carcinogenic dibenzopyrene isomers dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,l)pyrene, and dibenzo(a,h)pyrene as well as three other polycyclic aromatic hydrocarbons (PAHs)--benzo(a)pyrene, perylene and coronene--in ambient particulate material samples from a street canyon, a rooftop, and an underground subway station in Stockholm, Sweden. To our knowledge, these are the first reported determinations of dibenzopyrene isomers in air particles from either Stockholm or a subway station. Taking into account both concentration and toxic equivalence factors (TEFs), the PAH with the highest carcinogenic potency in the analyzed samples was dibenzo(a,l)pyrene, and the sum carcinogenic potency of the determined dibenzopyrenes was about 1-4 times higher than that of benzo(a)pyrene in the analyzed samples. These findings indicate that it is important to analyze the dibenzopyrene isomers as well as benzo(a)pyrene; the common approach of using benzo(a)pyrene as an indicator substance could lead to underestimates of the potential carcinogenic potency of PAHs in ambient air. The results also indicate that the relative carcinogenic potency of the determined dibenzopyrenes and benzo(a)pyrene in air particles from Stockholm is similar to that of air particles sampled in Washington in 1976-1977, despite general improvements in air quality in the intervening period. However, more data are needed to characterize temporal variations in dibenzopyrene levels in locations such as subway stations, suburbs, road tunnels, and metropolitan areas. There is also a need to identify and characterize both stationary and mobile PAH sources with respect to emission of dibenzopyrene isomers.

Standard reference materials (SRMs) for determination of organic contaminants in environmental samples

For the past 25 years the National Institute of Standards and Technology (NIST) has developed certified reference materials (CRMs), known as standard reference materials (SRMs), for determination of organic contaminants in environmental matrices. Assignment of certified concentrations has usually been based on combining results from two or more independent analytical methods. The first-generation environmental-matrix SRMs were issued with certified concentrations for a limited number (5 to 10) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Improvements in the analytical certification approach significantly expanded the number and classes of contaminants determined. Environmental-matrix SRMs currently available include air and diesel particulate matter, coal tar, marine and river sediment, mussel tissue, fish oil and tissue, and human serum, with concentrations typically assigned for 50 to 90 organic contaminants, for example PAHs, nitro-substituted PAHs, PCBs, chlorinated pesticides, and polybrominated diphenyl ethers (PBDEs).

Overview of particulate exposures in the US trucking industry

As part of a large epidemiologic study of lung cancer, 55,000 subjects, we have conducted a nation-wide survey of particulate exposures in the US trucking industry. The goal is to differentiate the risks from various types of particulate exposures, such as traffic emissions and general air pollution. We hypothesize that exposures defined by job and work site characteristics can be linked with subjects using their personal job histories. This report covers exposures at 36 randomly chosen large truck freight terminals in the US. Measurements were made of PM2.5, elemental carbon (EC), and organic carbon (OC) upwind of the terminal (background) and in work areas, and by personal samples. Significant differences in exposure intensity, microg m(-3), were found for work locations and jobs relative to background levels (GM[GSD]) at terminal sites: PM2.5 9.8[2.34], EC 0.5[3.24], and OC 5.0[1.76]. Using EC as a marker for diesel particles, work locations varied significantly: office 0.3[3.7], dock area 0.7[2.89] and shop area 1.5[3.52]), as did job titles (non-smokers): clerk 0.1[9.98], dock worker 0.8[2.13], and mechanic 2.0[3.82]. Cigarette smoking contributed substantially to personal exposures, approximately doubling PM2.5 and OC, but having less of an effect on EC. Large differences were seen across the terminal sites due to differences in local regional air pollution levels from traffic and other sources. We conclude that it will be possible to estimate current exposures of the cohort using an exposure assignment matrix based on job title, work location, and terminal site. This distribution overlaps substantially with the general public's exposure to these sources.

Modeling particle exposure in U.S. trucking terminals

Multi-tiered sampling approaches are common in environmental and occupational exposure assessment, where exposures for a given individual are often modeled based on simultaneous measurements taken at multiple indoor and outdoor sites. The monitoring data from such studies is hierarchical by design, imposing a complex covariance structure that must be accounted for in order to obtain unbiased estimates of exposure. Statistical methods such as structural equation modeling (SEM) represent a useful alternative to simple linear regression in these cases, providing simultaneous and unbiased predictions of each level of exposure based on a set of covariates specific to the exposure setting. We test the SEM approach using data from a large exposure assessment of diesel and combustion particles in the U.S.trucking industry. The exposure assessment includes data from 36 different trucking terminals across the United States sampled between 2001 and 2005, measuring PM2.5 and its elemental carbon (EC), organic carbon (OC) components, by personal monitoring, and sampling at two indoor work locations and an outdoor "background" location. Using the SEM method, we predict the following: (1) personal exposures as a function of work-related exposure and smoking status; (2) work-related exposure as a function of terminal characteristics, indoor ventilation, job location, and background exposure conditions; and (3) background exposure conditions as a function of weather, nearby source pollution, and other regional differences across terminal sites. The primary advantage of SEMs in this setting is the ability to simultaneously predict exposures at each of the sampling locations, while accounting for the complex covariance structure among the measurements and descriptive variables. The statistically significant results and high R2 values observed from the trucking industry application supports the broader use of this approach in exposure assessment modeling.

Determination of dibenzopyrenes in standard reference materials (SRM) 1649a, 1650, and 2975 using ultrasonically assisted extraction and LC-GC-MS

A method has been developed for analysis of the highly potent polycyclic aromatic hydrocarbon (PAH) carcinogens dibenzo(a,l)pyrene, dibenzo(a,h)pyrene, and dibenzo(a,i)pyrene (molecular weight 302) present in small amounts in diesel and air particulate material. The method can also be used for analysis of the PAH benzo(a)pyrene, coronene, and perylene, for which reference and certified values are available for the standard reference materials used for validation of the method--SRM 1649a (urban dust) and SRM 2975 (diesel particulate matter). The only NIST values that have been published for these dibenzopyrene isomers in the analyzed SRM are reference values for dibenzo(a,i)pyrene and dibenzo(a,h)pyrene in SRM 1649a. The concentrations determined in the SRM were in good agreement with reported NIST-certified and reference values and other concentrations reported in the literature. Standard reference material 1650 (diesel particulate matter) was also analyzed. The method could not, however, be validated using this material because certification of SRM 1650 had expired. The method is based on ultrasonically assisted extraction of the particulate material, then silica SPE pre-separation and isolation, and, separation and detection by hyphenated LC-GC-MS. The method is relatively rapid and requires only approximately 1-5 mg SRM particulate material to identify and quantify the analytes. Low extraction recoveries for the analytes, in particular the dibenzopyrenes, when extracting diesel SRM 2975 and 1650 resulted, however, in the dibenzopyrenes being present in amounts near their limits of quantifications in these samples. The method's limit of quantification (LOQ), based on analyses of SRM 1649a, is in the range 10-77 pg. By use of this method more than 25 potential PAH isomers with a molecular weight of 302 could be separated.

The organic composition of diesel particulate matter, diesel fuel and engine oil of a non-road diesel generator

Diesel-powered equipment is known to emit significant quantities of fine particulate matter to the atmosphere. Numerous organic compounds can be adsorbed onto the surfaces of these inhalable particles, among which polycyclic aromatic hydrocarbons (PAHs) are considered potential occupational carcinogens. Guidelines have been established by various agencies regarding diesel emissions and various control technologies are under development. The purpose of this study is to identify, quantify and compare the organic compounds in diesel particulate matter (DPM) with the diesel fuel and engine oil used in a non-road diesel generator. Approximately 90 organic compounds were quantified (with molecular weight ranging from 120 to 350), which include alkanes, PAHs, alkylated PAHs, alkylbenzenes and alkanoic acids. The low sulfur diesel fuel contains 61% alkanes and 7.1% of PAHs. The identifiable portion of the engine oil contains mainly the alkanoic and benzoic acids. The composition of DPM suggests that they may be originated from unburned diesel fuel, engine oil evaporation and combustion generated products. Compared with diesel fuel, DPM contains fewer fractions of alkanes and more PAH compounds, with the shift toward higher molecular weight ones. The enrichment of compounds with higher molecular weight in DPM may be combustion related (pyrogenic).

Effects of exposure to diesel exhaust particles (DEP) on pulmonary metabolic activation of mutagenic agents

Exposure of rats to diesel exhaust particles (DEP) or carbon black (CB) has been shown to induce time-dependent changes in CYP1A1and CYP2B1 in the lung. The present study evaluated the role of these metabolic enzymes on the pulmonary bioactivation of mutagens. Male Sprague-Dawley rats were intratracheally instilled with saline (control), DEP or CB (35 mg/kg body weight) and sacrificed at 1, 3, or 7 days post-exposure. Both control and exposed lung S9 increased the mutagenic activity of 2-aminoanthracene (2-AA), 2-aminofluorene (2-AF), 1-nitropyrene (1-NP), and the organic extract of DEP (DEPE) in Ames tests with Salmonella typhimurium YG1024 in a dose-dependent manner. Lung microsomes prepared form control or particle-exposed S9, but not cytosolic protein, activated 2-AA mutagenicity. Compared to saline controls, CB-exposed S9 was a less potent inducer of 2-AA mutagenicity at all time points, whereas DEP-exposed S9 was less potent than control saline at 3 and 7 days but not 1 day post-exposure. At 3 days post-exposure, DEP- or CB-exposed lung S9 did not significantly affect the mutagenicity of DEPE or 1-NP, when compared to the controls. The mutgenicity of 2-AA, 2-AF, 1-NP, and DEPE were significantly decreased in the presence of inhibitors for CYP1A1 (alpha-naphthoflavone) or CYP2B (metyrapone), but markedly enhanced by CYP1A1 or CYP2B1 supersomes with all the cofactors, suggesting that both CYP1A1 and CYP2B1 were responsible for mutagen activation. These results demonstrated that exposure of rats to DEP or CB altered metabolic activity of lung S9 and S9 metabolic activity dependent mutagen activation. The bioactivation of mutagens are metabolic enzyme- and substrate-specific, and both CYP1A1 and CYP2B1 play important roles in pulmonary mutagen activation.