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.

Emissions of acrolein and other aldehydes from biodiesel-fueled heavy-duty vehicles.

Aldehyde emissions were measured from two heavy-duty trucks, namely 2000 and 2008 model year vehicles meeting different EPA emission standards. The tests were conducted on a chassis dynamometer and emissions were collected from a constant volume dilution tunnel. For the 2000 model year vehicle, four different fuels were tested, namely California ultralow sulfur diesel (CARB ULSD), soy biodiesel, animal biodiesel, and renewable diesel. All of the fuels were tested with simulated city and high speed cruise drive cycles. For the 2008 vehicle, only soy biodiesel and CARB ULSD fuels were tested. The research objective was to compare aldehyde emission rates between (1) the test fuels, (2) the drive cycles, and (3) the engine technologies. The results showed that soy biodiesel had the highest acrolein emission rates while the renewable diesel showed the lowest. The drive cycle also affected emission rates with the cruise drive cycle having lower emissions than the urban drive cycle. Lastly, the newer vehicle with the diesel particulate filter had greatly reduced carbonyl emissions compared to the other vehicles, thus demonstrating that the engine technology had a greater influence on emission rates than the fuels.

Evaluation of the impacts of biodiesel and second generation biofuels on NO(x) emissions for CARB diesel fuels.

The impact of biodiesel and second generation biofuels on nitrogen oxides (NO(x)) emissions from heavy-duty engines was investigated using a California Air Resources Board (CARB) certified diesel fuel. Two heavy-duty engines, a 2006 engine with no exhaust aftertreatment, and a 2007 engine with a diesel particle filter (DPF), were tested on an engine dynamometer over four different test cycles. Emissions from soy- and animal-based biodiesels, a hydrotreated renewable diesel, and a gas to liquid (GTL) fuel were evaluated at blend levels from 5 to 100%. NO(x) emissions consistently increased with increasing biodiesel blend level, while increasing renewable diesel and GTL blends showed NO(x) emissions reductions with blend level. NO(x) increases ranged from 1.5% to 6.9% for B20, 6.4% to 18.2% for B50, and 14.1% to 47.1% for B100. The soy-biodiesel showed higher NO(x) emissions increases compared to the animal-biodiesel. NO(x) emissions neutrality with the CARB diesel was achieved by blending GTL or renewable diesel fuels with various levels of biodiesel or by using di-tert-butyl peroxide (DTBP). It appears that the impact of biodiesel on NO(x) emissions might be a more important consideration when blended with CARB diesel or similar fuels, and that some form of NO(x) mitigation might be needed for biodiesel blends with such fuels.

Polycyclic aromatic hydrocarbons in edible grain: a pilot study of agricultural crops as a human exposure pathway for environmental contaminants using wheat as a model crop.

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were investigated in a pilot study of field wheat grain as a model indicator for environmental contamination. The edible grain would serve as a portal for human exposure. Wheat grain was initially studied since it is one of the major food crops consumed internationally by many including infants and children. Wheat grain samples from five different geographical growing locations in California that span approximately 450 km were collected during the same growing season. The same variety of grain was harvested and analyzed for PAHs that ranged from 2- to 6-rings. PAHs were detected in all grain samples and were mainly 2- to 4-ring PAHs with naphthalene the most abundant among them. There were geographical differences in the levels of PAHs in the grain. The sources of the PAHs were not known in this pilot study, but the principal component analysis indicates that the major source is similar in all locations except for naphthalene. Grain naphthalene concentrations may reflect local naphthalene emissions. Diesel-fueled harvesting operations did not appear to contribute to the observed PAH concentrations in the grain. An estimate of naphthalene intake from eating grain compared to inhalation intake demonstrated the potential importance of field contamination of grain as a possible portal of human exposure. The relationship between PAH concentrations in grain and air should be quantitatively investigated to better quantitate exposure and to identify effective measures to lower the risk from PAH exposure through eating grain.

Controlled exposure chamber study of uptake and clearance of airborne polycyclic aromatic hydrocarbons by wheat grain.

Polycyclic aromatic hydrocarbons (PAHs) can partition from the atmosphere into agricultural crops, contributing to exposure through the dietary pathway. In this study, controlled environmental chamber experiments were conducted to investigate the transfer of PAHs from air into wheat grain, which is a major food staple. A series of PAHs ranging in size from naphthalene to pyrene were maintained at elevated gas-phase concentrations in the chamber housing mature and dry wheat grain both on the plant and with the husk removed. The PAHs did not achieve equilibrium between the air and grain over the 6.5 month monitoring period used in this study. Therefore, PAH uptake under field conditions is expected to be kinetically limited. A clearance study conducted for the grain showed the half-life of clearance was approximately 20 days for all compounds studied. The results suggest that atmospheric contaminants that partition into grain may remain in the grain long enough to contribute to dietary exposure for humans. Mass transfer across the air/grain interface appeared to be limited by grain-side resistance. The grain may act as a multicompartment system with rapid exchange at the surface followed by slower transfer into the grain. A grain/air concentration relationship was derived for the uptake time that is relevant to field conditions.

Unregulated emissions from compressed natural gas (CNG) transit buses configured with and without oxidation catalyst.

The unregulated emissions from two in-use heavy-duty transit buses fueled by compressed natural gas (CNG) and equipped with oxidation catalyst (OxiCat) control were evaluated. We tested emissions from a transit bus powered by a 2001 Cummins Westport C Gas Plus 8.3-L engine (CWest), which meets the California Air Resources Board's (CARB) 2002 optional NOx standard (2.0 g/bhp-hr). In California, this engine is certified only with an OxiCat, so our study did not include emissions testing without it. We also tested a 2000 New Flyer 40-passenger low-floor bus powered by a Detroit Diesel series 50G engine (DDCs50G) that is currently certified in California without an OxiCat. The original equipment manufacturer (OEM) offers a "low-emission" package for this bus that includes an OxiCat for transit bus applications, thus, this configuration was also tested in this study. Previously, we reported that formaldehyde and other volatile organic emissions detected in the exhaust of the DDCs50G bus equipped with an OxiCat were significantly reduced relative to the same DDCs50G bus without OxiCat. In this paper, we examine othertoxic unregulated emissions of significance. The specific mutagenic activity of emission sample extracts was examined using the microsuspension assay. The total mutagenic activity of emissions (activity per mile) from the OxiCat-equipped DDC bus was generally lower than that from the DDC bus without the OxiCat. The CWest bus emission samples had mutagenic activity that was comparable to that of the OxiCat-equipped DDC bus. In general, polycyclic aromatic hydrocarbon (PAH) emissions were lower forthe OxiCat-equipped buses, with greater reductions observed for the volatile and semivolatile PAH emissions. Elemental carbon (EC) was detected in the exhaust from the all three bus configurations, and we found that the total carbon (TC) composition of particulate matter (PM) emissions was primarily organic carbon (OC). The amount of carbon emissions far exceeded the PM-associated inorganic element emissions, which were detected in all exhaust samples, at comparatively small emission rates. In summary, based on these results and those referenced from our group, the use of OxiCat for the new CWest engine and as a retrofit option for the DDCs50G engine generally results in the reduction of tailpipe toxic emissions. However, the conclusions of this study do not take into account OxiCat durability, deterioration, lubricant consumption, or vehicle maintenance, and these parameters merit further study.

Emissions of toxic pollutants from compressed natural gas and low sulfur diesel-fueled heavy-duty transit buses tested over multiple driving cycles.

The number of heavy-duty vehicles using alternative fuels such as compressed natural gas (CNG) and new low-sulfur diesel fuel formulations and equipped with after-treatment devices are projected to increase. However, few peer-reviewed studies have characterized the emissions of particulate matter (PM) and other toxic compounds from these vehicles. In this study, chemical and biological analyses were used to characterize the identifiable toxic air pollutants emitted from both CNG and low-sulfur-diesel-fueled heavy-duty transit buses tested on a chassis dynamometer over three transient driving cycles and a steady-state cruise condition. The CNG bus had no after-treatment, and the diesel bus was tested first equipped with an oxidation catalyst (OC) and then with a catalyzed diesel particulate filter (DPF). Emissions were analyzed for PM, volatile organic compounds (VOCs; determined on-site), polycyclic aromatic hydrocarbons (PAHs), and mutagenic activity. The 2000 model year CNG-fueled vehicle had the highest emissions of 1,3-butadiene, benzene, and carbonyls (e.g., formaldehyde) of the three vehicle configurations tested in this study. The 1998 model year diesel bus equipped with an OC and fueled with low-sulfur diesel had the highest emission rates of PM and PAHs. The highest specific mutagenic activities (revertants/microg PM, or potency) and the highest mutagen emission rates (revertants/mi) were from the CNG bus in strain TA98 tested over the New York Bus (NYB) driving cycle. The 1998 model year diesel bus with DPF had the lowest VOCs, PAH, and mutagenic activity emission. In general, the NYB driving cycle had the highest emission rates (g/mi), and the Urban Dynamometer Driving Schedule (UDDS) had the lowest emission rates for all toxics tested over the three transient test cycles investigated. Also, transient emissions were, in general, higher than steady-state emissions. The emissions of toxic compounds from an in-use CNG transit bus (without an oxidation catalyst) and from a vehicle fueled with low-sulfur diesel fuel (equipped with DPF) were lower than from the low-sulfur diesel fueled vehicle equipped with OC. All vehicle configurations had generally lower emissions of toxics than an uncontrolled diesel engine. Tunnel backgrounds (measurements without the vehicle running) were measured throughout this study and were helpful in determining the incremental increase in pollutant emissions. Also, the on-site determination of VOCs, especially 1,3-butadiene, helped minimize measurement losses due to sample degradation after collection.