Inflammatory marker and aryl hydrocarbon receptor-dependent responses in human macrophages exposed to emissions from biodiesel fuels.

Biodiesel or renewable diesel fuels are alternative fuels produced from vegetable oil and animal tallow that are being considered to help reduce the use of petroleum-based fuels and emissions of air pollutants including greenhouse gases. Here, we analyzed the gene expression of inflammatory marker responses and the cytochrome P450 1A1 (CYP1A1) enzyme after exposure to diesel and biodiesel emission samples generated from an in-use heavy-duty diesel vehicle. Particulate emission samples from petroleum-based California Air Resource Board (CARB)-certified ultralow sulfur diesel (CARB ULSD), biodiesel, and renewable hydro-treated diesel all induced inflammatory markers such as cyclooxygenase-2 (COX)-2 and interleukin (IL)-8 in human U937-derived macrophages and the expression of the xenobiotic metabolizing enzyme CYP1A1. Furthermore, the results indicate that the particle emissions from CARB ULSD and the alternative diesel fuel blends activate the aryl hydrocarbon receptor (AhR) and induce CYP1A1 in a dose- and AhR-dependent manner which was supported by the AhR luciferase reporter assay and gel shift analysis. Based on a per mile emissions with the model year 2000 heavy duty vehicle tested, the effects of the alternative diesel fuel blends emissions on the expression on inflammatory markers like IL-8 and COX-2 tend to be lower than emission samples derived from CARB ULSD fuel. The results will help to assess the potential benefits and toxicity from biofuel use as alternative fuels in modern technology diesel engines.

Fine organic particle, formaldehyde, acetaldehyde concentrations under and after the influence of fire activity in the atmosphere of Riverside, California.

Concentrations of gas-phase organic carbons (formaldehyde (HCHO) and acetaldehyde (CH(3)CHO)) and fine particle-phase carbons (organic carbon (OC) and elemental carbon (EC)) were measured under and after the influence of fire activity in southern California. The measurement was conducted after the start of the wildfire activities from October 27 through November 6, 2003 at a site in Riverside, southern California. Under the influence of the fire activities, HCHO, CH(3)CHO and EC concentrations were found to be over two times as high as those after the fire activities ended. The total lifetime cancer risk estimated by HCHO and CH(3)CHO concentrations measured was significantly higher under the influence of the wildfire activities than that after the activities ended. OC showed a larger difference in concentrations between the two event periods as compared with gas-phase organic carbons and EC. OC/EC ratios ranged from 3.7 to 12.5 during the study period with the highest OC/EC ratio observed when the study area was under the influence of the fire activities. Correlation analysis and multiple linear regressions between OC/EC concentrations and visibility were performed. It was found that the visibility was even worse under the influence of fire activity as compared to the period after fire activity ended. EC was a stronger contributor to the visibility reduction compared to OC. The influence of air mass pathways on HCHO, CH(3)CHO, OC, and EC concentrations during the wildfire activities was addressed using a backward trajectory model developed by NOAA.

Secondary organic aerosol formation from the photooxidation of p- and o-xylene.

The formation of secondary organic aerosol (SOA) from the photooxidation of xylene isomers (m-, p-, and o-xylenes) has been extensively investigated. The dependence of SOA aerosol formation on the structure of xylene isomers in the presence of NO was confirmed. Generally, SOA formation of p-xylene was less than that of m- and o-xylenes. This discrepancy varies significantly with initial NOx levels. In a NOx-free environment, the difference of aerosol formation between o- and p-xylenes becomes insignificant. Several chemical pathways for the SOA dependence on structure and NOx are explored, with the experimental findings indicating that organic peroxides may be a major key to explaining SOA formation from aromatic hydrocarbons.

Secondary organic aerosol formation from m-xylene in the absence of NOx.

Formation of secondary organic aerosol (SOA) from m-xylene photoxidation in the absence of NOx was investigated in a series of smog chamber experiments. Experiments were performed in dry air and in the absence of seed aerosol with H2O2 photolysis providing a stable hydroxyl radical (OH radical) source. SOA formation from this study is exceptionally higher than experiments with existence of NOx. The experiments with elevated HO2 levels indicate that organic hydroperoxide compounds should contribute to SOA formation. Nitrogen oxide (NO) is shown to reduce aerosol formation; the constant aerosol formation rate obtained before addition of NO and after consumption of NO strongly suggests that aerosol formation is mainlythrough reactions with OH and HO2 radicals. In addition, a density of 1.40 +/- 0.1 g cm(-3) for the SOA from the photooxidation of m-xylene in the absence of NOx has been measured, which is significantly higherthan the currently used unit density.

Impact of propene on secondary organic aerosol formation from m-xylene.

Propene is widely used in smog chamber experiments to increase the hydroxyl radical (OH) level based on the assumption that the formation of secondary organic aerosol (SOA) from parent hydrocarbon is unaffected. A series of m-xylene/NO(x) photooxidation experiments were conducted in the presence of propene in the University of California CE-CERT atmospheric chamber facility. The experimental data are compared with previous m-xylene/N0(x) photooxidation work performed in the same chamber facility in the absence of propene (Song et al. Environ. Sci. Technol. 2005, 39, 3143-3149). The result shows that, for similar initial conditions, experiments with propene have lower reaction rates of m-xylene than those without propene, which indicates that propene reduces OH in the system. Furthermore, experiments with propene showed more than 15% reduction in SOA yield compared to experiments in the absence of propene. Additional experiments of m-xylene/ NO(x) with CO showed similar trends of suppressing OH and SOA formation. These results indicate that SOA from m-xylene/NO(x) photooxidation is strongly dependent on the OH level present, which provides evidence for the critical role of OH in SOA formation from aromatic hydrocarbons.

Effect of ammonia on secondary organic aerosol formation from alpha-pinene ozonolysis in dry and humid conditions.

This study examines the influence of ammonia (NH3) on secondary organic aerosol (SOA) formation from the alpha-pinene/ozone oxidation system for dry and humid conditions. Aerosol yield differed depending on which OH scavenger was used, with the highest yield noted for CO, followed by cyclohexane and 2-butanol. Number and volume concentrations were quickly increased within the reactor by 15 and 8%, respectively, when NH3 was added after the reaction ceased. The increase in number concentration indicated the formation of new particles resulting from gas-to-particle conversion. Moreover, average particle size increased from 242 to 248 nm. The resulting aerosol growth was attributed to ammonium salts formed by the reaction between organic acids and NH3. When NH3 was added to aerosolized cis-pinonic acid in the environmental reactor, a dramatic increase in both number and volume concentrations of cis-pinonic acid was observed. This provides further evidence that NH3 can interact with gas-phase organic acids forming condensable salts and thereby enhancing SOA formation. Initially present NH3 significantly enhanced aerosol yield in alpha-pinene-ozone reactions, regardless of the presence of water vapor. The role of NH3 on SOA formation in the dry and humid conditions is discussed in terms of a theoretical modeling study.

Promotion of noise-induced cochlear injury by toluene and ethylbenzene in the rat.

Ethylbenzene + toluene are known individually to have ototoxic potential at high exposure levels and with prolonged exposure times generally of 4-16 weeks. Both ethylbenzene + toluene are minor constituents of JP-8 jet fuel; this fuel has recently been determined to promote susceptibility to noise-induced hearing loss. Therefore, the current study evaluates the ototoxic potential of combined exposure to ethylbenzene + toluene exposure in a ratio calculated from the average found in three laboratories. Rats received ethylbenzene + toluene by inhalation and half of them were subjected simultaneously to an octave band of noise (OBN) of 93-95 dB. Another group received only the noise exposure which was designed to produce a small, but permanent auditory impairment while an unexposed control group was also included. In two separate experiments, exposures occurred either repeatedly on 5 successive days for 1 week or for 5 days on 2 successive weeks to 4000 mg/m(3) total hydrocarbons for 6 h based upon initial pilot studies. The concentration of toluene was 400 ppm and the concentration of ethylbenzene was 660 ppm. Impairments in auditory function were assessed using distortion product otoacoustic emissions and compound action potential testing. Following completion of these tests, the organs of Corti were dissected to permit evaluation of hair cell loss. The uptake and elimination of the solvents was assessed by harvesting key organs at two time points following ethylbenzene + toluene exposure from additional rats not used for auditory testing. Similarly, glutathione (GSH) levels were measured in light of suggestions that oxidative stress might result from solvent-noise exposures. Ethylbenzene + toluene exposure by itself at 4000 mg/m(3) for 6 h did not impair cochlear function or yield a loss of hair cells. However, when combined with a 93-dB OBN exposure combined solvent + noise did yield a loss in auditory function and a clear potentiation of outer hair cell death that exceeded the loss produced by noise alone. No evidence was found for a loss in total GSH in lung, liver, or brain as a consequence of ethylbenzene + toluene exposure.

JP-8 jet fuel can promote auditory impairment resulting from subsequent noise exposure in rats.

We report on the transient and persistent effects of JP-8 jet fuel exposure on auditory function in rats. JP-8 has become the standard jet fuel utilized in the United States and North Atlantic Treaty Organization countries for military use and it is closely related to Jet A fuel, which is used in U.S. domestic aviation. Rats received JP-8 fuel (1000 mg/m(3)) by nose-only inhalation for 4 h and half of them were immediately subjected to an octave band of noise ranging between 97 and 105 dB in different experiments. The noise by itself produces a small, but permanent auditory impairment. The current permissible exposure level for JP-8 is 350 mg/m(3). Additionally, a positive control group received only noise exposure, and a fourth group consisted of untreated control subjects. Exposures occurred either on 1 day or repeatedly on 5 successive days. Impairments in auditory function were assessed using distortion product otoacoustic emissions and compound action potential testing. In other rats, tissues were harvested following JP-8 exposure for assessment of hydrocarbon levels or glutathione (GSH) levels. A single JP-8 exposure by itself at 1000 mg/m(3) did not disrupt auditory function. However, exposure to JP-8 and noise produced an additive disruption in outer hair cell function. Repeated 5-day JP-8 exposure at 1000 mg/m(3) for 4 h produced impairment of outer hair cell function that was most evident at the first postexposure assessment time. Partial though not complete recovery was observed over a 4-week postexposure period. The adverse effects of repeated JP-8 exposures on auditory function were inconsistent, but combined treatment with JP-8 + noise yielded greater impairment of auditory function, and hair cell loss than did noise by itself. Qualitative comparison of outer hair cell loss suggests an increase in outer hair cell death among rats treated with JP-8 + noise for 5 days as compared to noise alone. In most instances, hydrocarbon constituents of the fuel were largely eliminated in all tissues by 1-h postexposure with the exception of fat. Finally, JP-8 exposure did result in a significant depletion of total GSH that was observable in liver with a nonsignificant trend toward depletion in the brain and lung raising the possibility that the promotion of noise-induced hearing loss by JP-8 might have resulted from oxidative stress.

Determination of VOC source signature of vehicle exhaust in a traffic tunnel.

This study describes the methodology used to obtain the volatile organic compound (VOC) source signature of vehicle exhaust. To accomplish this, C(2)-C(9) VOCs were measured in a traffic tunnel located in Seoul, South Korea. The effect of VOC concentrations from the outside ambient air was considered in the determination of the source signature. To examine the effects of ambient air on VOC concentrations inside the tunnel, the ratio of propane to the total VOC concentrations was compared between the entrance and middle sites in the tunnel. Propane was used as a standard not only because of its insignificant contribution to vehicle exhaust gas, but also the fact that propane is the most abundant VOC in the atmosphere of Seoul. The ratio of propane to the total VOC concentrations was higher at the entrance site than at the middle location by, on average, 60%. This suggests that ambient air affects the inside tunnel air to a greater extent at the entrance site as compared to the middle site. The contribution of ambient air to the air inside the tunnel at the entrance location varied from 30% to 67%, with an average of 55%. This is 1.5 times higher than the value measured at the middle location, which ranged from 20% to 48%, with an average of 36%. This shows that ambient air substantially affects the inside air of the tunnel. Excluding the effects of ambient air on the air inside the tunnel can provide an improved chemical composition for vehicle exhaust using tunnel measurements. We believe that the concentration difference between the two sites within the tunnel provides a more accurate chemical composition of vehicle exhaust as compared to that obtained from a measurement taken at only one point inside the tunnel.

Impact of the hydrocarbon to NOx ratio on secondary organic aerosol formation.

A series of m-xylene/NOx experiments were conducted in the new Bourns College of Engineering-Center for Environmental Research and Technology dual 90 m3 indoor smog chamber to elucidate the role of NOx on the secondary organic aerosol (SOA) formation potential of m-xylene. The results presented herein demonstrate a clear dependence of m-xylene SOA formation potential on NOx, particularly at atmospherically relevant organic aerosol concentration. Experiments with lower NOx levels generated considerably more organic aerosol mass than did experiments with higher NOx levels when reacted m-xylene was held constant. For example, SOA formation from approximately 150 microg m(-3) reacted m-xylene produced 0.6-9.3 microg m(-3) aerosol mass for NOx concentrations ranging from 286 to 10 ppb. The increase in SOA formation was not attributable to changes in ozone and nitrate concentration. A general discussion about possible influences of NOx on SOA formation for this system is included.

Chemical composition of major VOC emission sources in the Seoul atmosphere.

This paper describes a chemical analysis of volatile organic compounds (VOCs) for five emission sources in Seoul. The source categories included motor vehicle exhaust, gasoline evaporation, paint solvents, natural gas and liquefied petroleum gas (LPG). These sources were selected because they have been known to emit significant quantities of VOCs in the Seoul area (more than 5% of the total emission inventory). Chemical compositions of the five emission sources are presented for a group of 45 C2-C9 VOCs. Motor vehicle exhaust profiles were developed by conducting an urban tunnel study. These emissions profiles were distinguished from the other emission profiles by a high weight percentage of butanes over seasons and propane in the wintertime. It was found that this is due to the wide use of butane-fueled vehicles. To obtain gasoline vapor profiles, gasoline samples from five major brands for each season were selected. The brands were blended on the basis of the marketshare of these brands in Seoul area. Raoult's law was used to calculate gasoline evaporative compositions based on the liquid gasoline compositions. The measured and estimated gasoline vapor compositions were found to be in good agreement. Vehicle and gasoline evaporation profiles were made over seasons because of the seasonal change in their compositions. Paint solvent emissions profiles were produced based on a product-use survey and sales figures. These profiles are a composite of four major oil-based paints and thinning solvent. The source profile of natural gas was made on a methane-free basis. It was found that Ethane and propane were the most abundant compounds accounting for 95% of the natural gas composition. LPG was largely composed of propane and ethane and the remaining components were minor contributors.