(544d) Biofuel and Reference Diesel Particles: Differences in Inflammatory and Oxidative Effects

Particulate matter (PM) from engine exhaust has become an increasing concern due to its links to numerous adverse effects on human health and the environment. Recent efforts to reduce PM emissions and the associated climate change impacts from combustion include new technologies, such as the installation of diesel particulate filters and the use of biofuels. However, studies comparing the biological effects of PM from biodiesel and petroleum-based diesel provide conflicting results, and interpretation of these results is difficult because of different methods for particle generation and for biological assays.

This study aims to systematically evaluate the effect of particles generated from two biofuel blends, one biodiesel (BD) and one alcohol diesel (AD) and one reference standard diesel particle sample (NIST SRM 2975) on selected biological outcomes associated with responses to diesel particles in lung cells and in animals. These include: (a) CYP1A1 and 1B1 enzymes that can both detoxify and bioactivate PAHs in human airway epithelial cells, human bronchial epithelial cellsand human macrophage cells lines, and (b) IL-8 and TNF-a that play critical roles in pulmonary host-defense and inflammatory responses. We also examined the role of activation of the transient receptor potential ankyrin-1 (TRPA1) cation channel, which is a target for diesel exhaust and similar combustion-derived particles and mediator of pro-inflammatory and irritant responses.Because PM deposits in small airways and the alveolar space, cell lines derived from small airway epithelial cells (H441) and modeling alveolar macrophages (THP-1) were selected for this study. PM was generated from simple surrogate fuels and characterized under well-controlled combustion conditions.

The results show that particle extracts caused similar responses compared to whole particles in both upper airway epithelial and macrophage cells. This suggests that the soluble organic components adsorbed on the particle surface are highly associated with the cellular responses we examined. When comparing the particles from the different fuel sources, BD particles are capable of activating key enzymes involved in PAH metabolism to very high levels compared to RD and AD. BD particles also had the greatest surface area, soluble organic fraction and oxidative potential. In contrast, RD was more pro-inflammatory than BD or AD, an effect that involved TRPA1 activation. This study adds to the growing body of evidence that biodiesel PM results in adverse lung health effects, potentially via different pathways than conventional diesel PM.