It is universally acknowledged that smoking causes cancer. Perhaps less well known is that diesel fumes are also linked to several types of cancer. But what exactly about smoking cigarettes or inhaling diesel exhaust can result in malignant tumors? The answer is that both contain cancer causing agents called carcinogens.

As for diesel fumes, the exact composition of diesel exhaust is difficult to ascertain as it changes depending on the type of engine, the speed and load at which it is run, and the composition of the fuel used. However, in 2000 the National Toxicology Program added diesel particulate matter (DPM) to their list of carcinogens and proclaimed that DPM is “reasonably anticipated to be a human carcinogen” and according to a 2002 Environmental Protection Agency report more than 100 carcinogenic of potentially carcinogenic components have been specifically identified in diesel emissions. For example, diesel exhaust contains identified mutagens and carcinogens, such as PAHs (polycyclic aromatic hydrocarbons – several of which are known carcinogens), benzene, formaldehyde, benzanthracene, benzofluoranthene, benzofluoranthene, benzopyrene, dibenzacridine, and indenopyrene. For a list of further chemicals associated with diesel exhaust go to

As for Cigarettes, different factors, like the type of tobacco product, chemical additives, pH, the type of paper and filter, affect the composition of tobacco smoke. Mainstream tobacco smoke contains a significant number of chemicals. Many of these chemicals are known carcinogens including several that are also found in diesel exhaust, such as benzene and formaldehyde.