Fumes from diesel engines have been classified as carcinogenic

The International Agency for Research on Cancer (IARC) found sufficient
evidence that exposure to diesel exhausts is associated with an increased risk
of lung cancer. They also noted limited evidence that exposure could lead to an
increased risk of bladder cancer.

The IARC had previously categorised diesel exhausts as ‘probably carcinogenic
to humans'. The updated classification follows the findings earlier this year
of a US study of occupational exposure to such emissions in underground miners,
which showed an increased risk of death from lung cancer in exposed workers.

The IARC also warns that people are not only exposed to motor-vehicle exhausts
but also to exhausts from other diesel engines, including other modes of
transport, such as diesel trains and ships, and from power generators.

More info - Source: International Agency for Research on Cancer (IARC)