Cancer potency of diesel exhaust is more than double than that of petrol cars in India. In other words, one diesel car is equivalent to two petrol cars if all gases emitted by the vehicles are taken into consideration. However, if only particulate emission is considered, the carcinogenic effect of one new diesel car is equivalent to 24 new petrol cars on the road, according to a study conducted by Peter Ahlvik and Ake Brandberg at Ecotraffic.

Diesel exhaust has traces of over 40 substances that are listed by the us epa as hazardous air pollutants and by carb as toxic air contaminants. Based on epidemiological studies, different countries have ascribed different estimates for cancer potencies to these compounds which is measured as unit risk. Unit risk of a compound indicates the risk of developing cancer due to lifetime (that is, 70 years) exposure to one microgramme per cubic metre (