In an historical session that was held earlier this week, panelists updated the research on diesel and gasoline noting that recent research has found associations between exposure to motor vehicle emission and other health outcomes such as respiratory symptons. In 2012, the International Agency for Research on Cancer designated diesel exhaust as a "known human carcinogen" and gasoline exhaust as a "possible human carcinogen." Yet, panelists noted there is some controversy surrounding the strength of the evidence that points to diesel exhaust as a carcinogen, noting that it is difficult to assess human expsoure to diesel exhaust alone as it is almost always inhaled as part of the larger air pollutant mixture, and there are no specific monitors in place to measure diesel exhaust specifically. They also pointed out there are still very few data on health effects in animals, and none in humans, of exhaust from the newest generation of diesel engines. The session was well attended and offered an excellent historical perspective about diesel and gasoline.