Scientific Symposium on the Toxicology of Alternate Fuels

September 13, 2013

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(EurekAlert) "Biofuel" has become a global buzzword, with cars and trucks powered by fuel made from corn, corncobs and stalks, switchgrass and even waste oil from cooking french fries, envisioned as a way to stretch out supplies of crude oil and cope with global warming.
A symposium being held here today at the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society, considers a topic that has received less attention: What are the health and environmental effects of green gasoline, biodiesel and other alternative fuels, and how do they stack up against conventional gasoline and diesel?
The talks in the symposium, among almost 7,000 presentations on scientific and other topics at the meeting ... will discuss topics that include:

New evidence that emissions from biodiesel vehicles are less mutagenic than those from petroleum-based diesel.
Research on the toxicity of conventional diesel and traditional diesel.
Human health effects of biofuels.
How engines have changed with changing fuels.

Abstracts
Mutagenicity and bioassay-directed fractionation of diesel and biodiesel emissions
David M DeMarini¹, demarini.david@epa.gov, Esra Mutlu², Sarah H. Warren¹, Peggy P. Matthews¹, Andrew D. Kligerman¹, Charly King¹, William P. Linak¹, David G. Nash³, M. Ian Gilmour¹. (1) US EPA, RTP, NC 27711, United States, (2) UNC, Chapel Hill, NC 27599, United States, (3) ORISE, Oak Ridge, TN 37831, United States
Biofuels are being developed as alternatives to petroleum-derived products, but published research is contradictory regarding the mutagenic activity of such emissions relative to those from petroleum diesel. We performed bioassay-directed fractionation and chemical analysis of organics extracted from particles generated using petroleum diesel (B0) and those from soy-based biodiesel where the soy accounted for 20, 50 or 100% of the fuel (B20, B50, B100) from a Yanmar L70 diesel engine. The particles were extracted with dichloromethane (DCM), and the percentage of extractable organics (%EOM) determined. Extracts were solvent exchanged into dimethyl sulfoxide and evaluated for mutagenicity in various Salmonella strains +/-S9. We calculated the mutagenic emission factors (revertants/megajoule, rev/MJ) from data from strain TA100 +S9, which responds to PAH-type mutagenicity. The %EOM was 25, 20, 30, and 60% for B0-B100. The mutagenic emission factors for the whole extracts in TA100+S9, which detects PAHs preferentially, were 0.3, 0.1, 0.05, and 0.04 rev/MJ for B0-B100. These mutagenic emission factors for the biodiesel emissions were 3X less (B20), 6X less (B50), and 8X less (B100) than that of petroleum diesel (B0). The whole extracts of the diesel and biodiesel organics were sequentially fractionated with solvents of increasing polarity. More than 50% of the mass for all the whole extracts of B0-B100 eluted in fraction 1 (hexane), and this fraction was not mutagenic. Most of the PAH-type mutagenicity (TA100+S9) eluted in fraction 2 (hexane/DCM), whereas most of the nitroarene activity (TA98-S9) eluted in fraction 3 (DCM). Fraction 4 (methanol) contained polar compounds. Sub-fractionation of the 4 fractions by HPLC confirmed these activity/chemical class distributions. We conclude that under these experimental conditions, emissions from biodiesel were less mutagenic than those from petroleum diesel, and most of the activity is associated with PAHs. [Abstract does not necessarily reflect the views or policies of the U.S. EPA.]
Exposure profiling of potentially genotoxic constituents in complex mixtures such as vehicle exhausts
Gunnar Boysen, GBoysen@uams.edu, Julie Evans-Johnson, Nadia I Georgieva, Shilpi Goel. Environmental and Occupational Health, University of Arkansas for Medical Sciences, LITTLE ROCK, AR 72205, United States
Humans are constantly exposed to mixtures, such as exhaust from diesel, gasoline and bio-fuels, containing several thousand compounds, including many known human carcinogens. Understanding health effects of exposure to mixtures is a daunting task and requires accurate characterization of the exposure and understanding of potential compound interaction. The main approach is to monitor as many potentially hazardous constituents as possible in air and water. However, it is well recognized that it will be a huge if not impossible undertaking to fully characterize complex exposures that constantly change and vary significantly between individuals and time. Therefore, internal biomonitoring such as metabolite profiling in urine and blood are considered to be more relevant since they represent actual absorbed constituents. To increase selectivity, analysis of DNA and protein adduct profiles have been proposed as most suitable because covalent binding to DNA and formation of stable adducts is believed to be the causal link between exposure and carcinogenesis. Most importantly, DNA and protein adducts retain sufficient chemical and structural information to ascertain individual compounds and are well established biomarkers for the internal dose. In this presentation we will outline current approaches and discuss advantages and limitations of technologies currently under development. We will present our latest results using hemoglobin adduct profiles as biomarkers for exposure to various mixtures.
Composition and toxicity of biodiesel vs. conventional diesel
Jacob D. McDonald, Mcdonal@LRRI.org, Chemistry and Inhalation Exposure Program, Lovelace Respiratory Research Institute, Albuquerque, NM 87108-5127, United States
Diesel engine exhaust is one of the most well studied environmental pollutants. After inhalation of exhaust there are dose dependent responses that include pulmonary and cardiovascular responses. The magnitude and response to inhaled engine exhaust has been shown to be linked to both the dose and the composition of the materials. Although few studies have evaluated the toxicity of biodiesel after inhalation, we performed a 90 day inhalation study to evaluation toxicity in rodents as a component of the registration process. Ames mutagenicity studies showed the presence of mutagenic material in the exhaust from biodiesel. Limited to no inflammatory or clinical response was observed in rodents exposed up to 1 mg/m3 of particulate matter for up to 90 days. In comparison, a 6 month inhalation study to diesel exhaust from a conventional fuel was conducted. When evaluating similar biological endpoints, there were similar observations of mutagenicity of the exhaust and limited biological response when evaluating pathology and clinical endpoints in rodents (rats). Several more sensitive biological endpoints evaluated in conventional diesel studies revealed cardiovascular and other responses. However, there are no known studies that enable comparison of these responses with biodiesel. The composition differences in the fuels will result in an increased emisisons of compounds related to the presence of the biodiesel fuel, and in general include increased oxygenated volatile organics and aliphatic acids. There are a typically lower corresponding concentrations of complex organics such as polycyclic aromatic hydrocarbons compared to conventional diesel.
Past, present, and future diesel engines: Design trends and emissions
David B. Kittelson, kitte001@umn.edu, Center for Diesel Research Facilities, University of Minnesota, Minneapolis, MN 55455, United States
Changes the diesel engines and their fuels over the last 30-40 years have led to dramatic reductions in emissions and changes in their composition. Until the mid-1980s, a wide variety of diesel engine designs and technologies were available. Increasingly stringent emission regulations led to convergence to a common diesel engine architecture: a 4-stroke cycle, high pressure electronically controlled direct injection, 4-valve heads and turbochargers. With further tightening of emission standards aftercoolers, EGR, and then cooled EGR were introduced. Fuel technology also changed as fuel sulfur was reduced to enable diesel engines to meet the PM standards and to introduce cooled EGR. The first aftertreatment devices applied to diesel engines were diesel oxidation catalysts (DOC) which came into relatively wide use in light and medium duty applications in the 1990s. They effectively reduce CO, hydrocarbons and particle bound organic carbon but have little influence on elemental carbon or NOx emissions. Diesel particle filters (DPF) were applied to European passenger cars in the 1990 and have been used in the US since 2007 to meet newer heavy-duty PM emission standards. Catalyzed DPFs are extremely effective at removing CO, hydrocarbons and particulate matter - especially elemental carbon and ash. Advanced catalyzed emission control systems would not have been possible without parallel development of very low sulfur fuels. Currently available biofuels for diesel engines are fatty acid methyl esters (FAME). Also available but less common are bio-based hydrocarbon fuels - Fischer-Tropsch liquids and hydrotreated vegetable oil. These fuels generally reduce but do not qualitatively change engine out emissions and still require DPFs and NOx control. Next generation biofuels like dimethyl ether (DME) burn virtually soot-free eliminating the need for DPFs but still require DOCs for CO and hydrocarbon control and will likely require NOx control as well.
Human health effects of diesel exhaust and traffic exposures
Eric Garshick, eric.garshick@channing.harvard.edu, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, United States
Epidemiologic evidence suggests that the adverse health effects attributable to diesel exhaust and traffic exposures include lung cancer, worsening of chronic respiratory disease, including chronic obstructive pulmonary disease and asthma, progression of cardiovascular disease, abnormal children's lung growth, and adverse birth outcomes. Most recently, in June 2012, a Working Group met at the International Agency for Research on Cancer (IARC; Lyon, France) to review the carcinogenicity of diesel engine exhaust. The most influential epidemiological studies assessing cancer risks associated with diesel-engine exhausts investigated occupational exposure among railroad workers, workers in the trucking industry, and non-metal miners. The assessment of lung cancer risk in trucking industry workers and in non-metal miners included the finding of a positive exposure-response relationship with occupational elemental carbon exposure. This presentation will review the epidemiologic studies that supported the conclusion of the Working Group that diesel engine exhaust is carcinogenic to humans (IARC Group 1) and key studies providing evidence of non-malignant health effects of traffic related exposures.
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