Compared to petrol engines, diesels produce 22 times as many particulates, and far more NOx. Large pieces are captured by hairs in our noses and airways and do relatively little harm.
But diesel contains high levels of tiny particulates – 100 times smaller than the thickness of a human hair – which get deep into the lungs and bloodstream, triggering asthma, inflammation, heart attacks and strokes.
Manufacturers reckoned they would struggle to persuade US consumers to pay a premium for more expensive diesel cars.
My mother, who lives in Tamworth in Staffordshire, went to Co-op and ASDA to get some water for us, but it had sold out there too.
They contain a cocktail of more than 40 toxic pollutants, including cancer-causing benzene, arsenic and formaldehyde.
The greatest concern centres on tiny sooty particulates and nitrogen oxides, or NOx – gases including nitrogen dioxide and nitrogen oxide.
The International Council on Clean Transport found modern diesels emit on average seven times the EU limit for nitrogen oxides when tested in laboratories, and not on the roads.
Diesel drivers worried about pollution could always tell themselves that they were helping to cut greenhouse gas emissions.