Alternatives to fossil fuels receive a lot of attention. In particular, oil derived of specific crops forms a promising fuel. In order to warrant global expectance of such novel fuels, safety issues associated with combustion of these fuels needs to be assessed. Although only a few public reports exist, recently potential toxic effects associated with biofuels has been published. Here, we report the analysis of a comprehensive study, comparing the toxic effects of conventional diesel, biodiesel and blends thereof in various in vitro assays. Besides the toxicological evaluation also chemical analysis and the particle size of the emission was measured.