Within the last decades the growing concern for anthropogenic pollution and its extensive effects have taken center stage influencing global technology, politics and business. After the Kyoto Protocol came about in 1997, the EU initially promoted diesel as the more environmentally friendly fuel, as carbon dioxide emissions tend to be reduced. Motorists were given incentives in order to buy more diesel cars, in the hopes that this would help to reduce greenhouse gas emissions. New research developments on diesel effects, emissions scandals, continued climate change advances and dependence on diminishing fossil fuel supplies have contributed to a shift in focus to renewable biofuels. “Green”, “eco- “, “bio- “, “sustainable”, “carbon-neutral” are just a few of the environmental buzzwords seen around us each day in order to now evoke a positive reaction. The most common biofuel within the EU is currently a biodiesel, RME (rapeseed oil methyl ester). It has been shown to emit fewer exhaust particles compared to standard petrodiesel and this purported “green fuel”, being of biological origin, is projected to be less harmful to human health. Whilst standard petrodiesel is now widely known to contribute to the onset and mortality of respiratory and cardiovascular diseases, the consequences to public health remain unexplored in regards to the majority of biofuels on the marketplace today. In a series of studies performed by our group, healthy volunteers were exposed to filtered air, petrodiesel or biodiesel dilute exhaust in a controlled chamber or by specially-designed mask. Following exposures in the first two studies, numerous cardiovascular endpoints were assessed as well as characterization of the exhaust. In further studies autonomic nervous system function was evaluated utilizing microneurography. Compared to petrodiesel, RME exhaust contained less elemental carbon, fewer polyaromatic hydrocarbons, lower levels of hydrocarbons and higher concentration of nitrogen oxides. RME also showed a shift in the particulate matter size distribution towards the ultrafine range and a significantly increased concentration of a range of metals relative to petrodiesel. These ultrafine particles have a greater surface area per mass and can access further into the respiratory tract making them potentially more damaging per mass than larger particles. The collective results in these studies demonstrated that despite their varying composition and particle reactivity, RME exhaust exposure induced comparable adverse health effects as exposure to standard petrodiesel exhaust through similar underlying mechanisms. Replacing petrodiesel with biodiesel may have certain advantageous ecological impacts, however, it would be well advocated that adverse health effects be addressed alongside environmental concerns when new fuel policies are considered due to potential major public health impacts.