In an announcement that caused concern in the auto industry, the France-based International Agency for Research on Cancer (IARC), part of the WHO, reclassified diesel exhausts from its group 2A of probable carcinogens to its group 1 of substances that have definite links to cancer.
The experts, who said their decision was unanimous and based on "compelling" scientific evidence, urged people worldwide to reduce their exposure to diesel fumes as much as possible.
It concluded that the exhausts were definitely a cause of lung cancer and may also cause tumours in the bladder
The decision was the result of a week-long meeting of independent experts who assessed the latest scientific evidence on the cancer-causing potential of diesel and gasoline exhausts.
It puts diesel exhaust fumes in the same risk category as a number of other noxious substances including asbestos, arsenic, mustard gas, alcohol and tobacco.