Diesel combustion exhaust is a major source of atmospheric soot and fine particles, which is a fraction of air pollution implicated in human heart and lung damage. Diesel exhaust also contains nanoparticles. While the study of nanoparticles and nanotoxicology is still in its infancy, and the full health effects from nanoparticles produced by all types of diesel are unknown. At least one study has observed that short term exposure to diesel exhaust does not result in adverse extra-pulmonary effects, effects that are often correlated with an increase in cardiovascular disease.[24] Long term effects still need to be clarified, as well as the effects on susceptible groups of people with cardiopulmonary diseases. It should be noted that the types and quantities of nanoparticles can vary according to operating temperatures and pressures, presence of an open flame, fundamental fuel type and fuel mixture, and even atmospheric mixtures. As such, the resulting types of nanoparticles from different engine technologies and even different fuels are not necessarily comparable. In general, the usage of biodiesel and biodiesel blends results in decreased pollution. One study has shown that the volatile component of 95% of diesel nanoparticles is unburned lubricating oil.[25]Diesel combustion exhaust is a major source of atmospheric soot and fine particles, which is a fraction of air pollution implicated in human heart and lung damage. Diesel exhaust also contains nanoparticles. While the study of nanoparticles and nanotoxicology is still in its infancy, and the full health effects from nanoparticles produced by all types of diesel are unknown. At least one study has observed that short term exposure to diesel exhaust does not result in adverse extra-pulmonary effects, effects that are often correlated with an increase in cardiovascular disease.[24] Long term effects still need to be clarified, as well as the effects on susceptible groups of people with cardiopulmonary diseases. It should be noted that the types and quantities of nanoparticles can vary according to operating temperatures and pressures, presence of an open flame, fundamental fuel type and fuel mixture, and even atmospheric mixtures. As such, the resulting types of nanoparticles from different engine technologies and even different fuels are not necessarily comparable. In general, the usage of biodiesel and biodiesel blends results in decreased pollution. One study has shown that the volatile component of 95% of diesel nanoparticles is unburned lubricating oil.[25]