Experts conducting an environmental analysis into the effect of diesel emissions on the environment have discovered that modern cars are not as green as first thought.
Mark Jacobson of Stanford University told Reuters that many of the supposed eco-friendly diesel cars currently on the market are damaging to the environment.
"Even with a particle trap (filter), all the diesels have an impact," said Stanford University's Mark Jacobson.
"Each effect will vary from vehicle to vehicle but the point is they are not accounting for this. The claim that barely detectable black carbon causes no warming is misinformation."
Diesel engines also produce more particulate matter than petrol-fuelled cars.
These particles of soot can exacerbate health problems such as asthma and can contribute to global warming.
New diesel car tailpipes are fitted with filters that trap both particulate matter and nitrogen oxide fumes. But these don't necessarily cure the problem, says Jacobson. "You have a trade-off - a particle trap reduces the efficiency of the nitrogen oxide filter, and vice versa," he says. According to Jacobson, cars fitted with filters still emit more nitrogen oxide than petrol vehicles.