Generation and characterization of diesel engine combustion emissions from petroleum diesel and soybean biodiesel fuels and application for inhalation exposure studies.

Biodiesel made from the transesterification of plant- and animal-derived oils is an important alternative fuel source for diesel engines. Although numerous studies have reported health effects associated with petroleum diesel emissions, information on biodiesel emissions are more limited. To this end, a program at the U.S. EPA assessed health effects of biodiesel emissions in rodent inhalation models. Commercially obtained soybean biodiesel (B100) and a 20% blend with petroleum diesel (B20) were compared to pure petroleum diesel (B0). Rats and mice were exposed independently for 4 h/day, 5 days/week for up to 6 weeks. Exposures were controlled by dilution air to obtain low (50 µg/m(3)), medium (150 µg/m(3)) and high (500 µg/m(3)) diesel particulate mass (PM) concentrations, and compared to filtered air. This article provides details on facilities, fuels, operating conditions, emission factors and physico-chemical characteristics of the emissions used for inhalation exposures and in vitro studies. Initial engine exhaust PM concentrations for the B100 fuel (19.7 ± 0.7 mg/m(3)) were 30% lower than those of the B0 fuel (28.0 ± 1.5 mg/m(3)). When emissions were diluted with air to control equivalent PM mass concentrations, B0 exposures had higher CO and slightly lower NO concentrations than B100. Organic/elemental carbon ratios and oxygenated methyl esters and organic acids were higher for the B100 than B0. Both the B0 and B100 fuels produced unimodal-accumulation mode particle-size distributions, with B0 producing lower concentrations of slightly larger particles. Subsequent papers in this series will describe the effects of these atmospheres on cardiopulmonary responses and in vitro genotoxicity studies.

Soy biodiesel emissions have reduced inflammatory effects compared to diesel emissions in healthy and allergic mice.

Toxicity of exhaust from combustion of petroleum diesel (B0), soy-based biodiesel (B100), or a 20% biodiesel/80% petrodiesel mix (B20) was compared in healthy and house dust mite (HDM)-allergic mice. Fuel emissions were diluted to target fine particulate matter (PM(2.5)) concentrations of 50, 150, or 500 µg/m(3). Studies in healthy mice showed greater levels of neutrophils and MIP-2 in bronchoalveolar lavage (BAL) fluid 2 h after a single 4-h exposure to B0 compared with mice exposed to B20 or B100. No consistent differences in BAL cells and biochemistry, or hematological parameters, were observed after 5 d or 4 weeks of exposure to any of the emissions. Air-exposed HDM-allergic mice had significantly increased responsiveness to methacholine aerosol challenge compared with non-allergic mice. Exposure to any of the emissions for 4 weeks did not further increase responsiveness in either non-allergic or HDM-allergic mice, and few parameters of allergic inflammation in BAL fluid were altered. Lung and nasal pathology were not significantly different among B0-, B20-, or B100-exposed groups. In HDM-allergic mice, exposure to B0, but not B20 or B100, significantly increased resting peribronchiolar lymph node cell proliferation and production of T(H)2 cytokines (IL-4, IL-5, and IL-13) and IL-17 in comparison with air-exposed allergic mice. These results suggest that diesel exhaust at a relatively high concentration (500 µg/m(3)) can induce inflammation acutely in healthy mice and exacerbate some components of allergic responses, while comparable concentrations of B20 or B100 soy biodiesel fuels did not elicit responses different from those caused by air exposure alone.