Rudolf Diesel designed his engine because he was appalled at how inefficient petrol and steam engines were in the 19th century.
It used to be thought that diesel engines, although more expensive to buy, were superior to petrol engines for mileage, but improvements in technology mean that is no longer always the case.
And when the full environmental cost of car engines was coming to be realised, diesel engines were favoured over petrol engines because it was thought that petrol’s greater carbon dioxide emissions were doing the most damage. But now just in environmental terms that is being challenged because the particulates that diesel engines give off are also believed to cause climate warming.
But it is the health impact of diesel engines that is now becoming clearer. In 2012 the International Agency for Research on Cancer, part of the World Health Organisation, classified diesel engine exhaust as carcinogenic to humans, saying exposure is associated with an increased risk for lung cancer. Diesel is the primary source of nitrogen dioxide in urban areas and is linked to health problems.
Now 300 health professionals have written to Prime Minister Theresa May, highlighting evidence of the impacts of pollutants particularly for children.
There is technology that can help reduce diesel emissions, and although that is unlikely to be retro-fitted to existing cars it does mean future diesel vehicles will be less harmful.
But the long-term solution here is in the huge steps forward for electric cars and hybrids, and in calculating the benefits of these vehicles the health impact should not be underplayed.