It was only some months ago that Volkswagen was revealed to have breached the standard about the emission gas. And recently, it was clarified this scandal was not limited to Volkswagen.
Actually, 97% of all diesel cars are considered not to adhere the official limit concerning toxic nitrogen oxide gas. Ironically, most of the rest 3% were composed of Volkswagens.
The Guardian: Revealed: nearly all new diesel cars exceed official pollution limits
I predicted this situation. It was unlikely Volkswagen was the only car need a defeat software to meet the environment standard.
My past entry: Volkswagen emission scandal
London is planning to introduce ultra-low emission zone by 2020 in which only cleanest vehicles will be acceptable. There are similar regulations also in Tokyo. Air pollution is one of the biggest and urgent problems in urban areas regardless of countries.
On the other hand, car providers have little incentive to commit the sustainability of the current environment. It is unsure that car owners will choose an environment-friendly car for a higher cost. People who are damaged by air pollution is not the person having inflicted the pollution but their descendants. Therefore, forecasting the future is necessary for considering this matter. However, companies, as well as politicians, are occupied in gaining the benefit at present.
It means that environmental issue can hardly be fixed with the market mechanism. The government, international treaty, or other authorities have to address this issue so that companies and consumers become patient. It is interesting that these emission scandals occurred in Europe firstly, not in the US.
Anyway, we are still in the confusion. I recommend you to take a wise choice when you buy a vehicle.