The findings of the Health Assessment Document for Diesel Engine Exhaust, released last week by the United States Environmental Protection Agency, were revealed as latest figures showed UK fleet diesel sales had risen by 47.2% so far this year.
Its authors stress their research is based on mid-1990's diesels, but warn they are not certain whether engine and fuel improvements in recent years will have done enough to eliminate the risks they have uncovered.
A spokesman said: 'The health hazard conclusions are applicable to engines currently in use, which include many older engines.
'As new diesel engines with cleaner exhaust emissions replace existing engines, the applicability of the conclusions will need to be re-evaluated.'
The report gives a damning assessment of the dangers to health of diesel emissions from some engines. It concludes: 'Long-term exposure to diesel engine exhaust emissions is likely to pose a lung cancer hazard as well as damage the lungs in other ways depending on exposure.
'On the basis of extensive animal testing evidence, diesel engine emissions are judged to pose a chronic respiratory hazard to humans'.
Short-term effects are also apparent, the report claimed, saying: 'The most readily identified non-cancer health effect on humans is its ability to elicit subjective complaints of eye, throat and bronchial irritation and symptoms such as headache, lightheadedness, nausea, vomiting and numbness and tingling of the extremities.
'Evidence also shows that it can induce allergic responses, some of which are also typical of asthma and/or exacerbate existing respiratory allergies.'
The 'weight of evidence' conclusions on the health risks of diesel exhaust emissions are the second major health scare for the fuel in just over three months, but are the first to be so direct about the potential health effects.
Earlier this year, Fleet NewsNet highlighted an American study that for the first time pinpointed how diesel exhaust fumes cause allergies and respiratory diseases. Despite the earlier warnings, fleet decision-makers said it would do nothing to damage the burgeoning demand for diesel cars among fleet drivers.
A recent Fleet Panel was asked 'Will the link recently established between diesel and respiratory diseases alter the standing of diesel-powered cars and vans on your fleet?'. An overwhelming 92% of fleet decision-makers said no.
Copies of the report can be accessed by clicking here.