Pollution solutions: Behavioural change
When I started first reporting on pollution in London, many moons ago, the real concern was particulate matter - the tiny particles mainly from traffic - that can cause health problems.
We still have episodes of high particulates in London - there was one a few weeks ago compounded by high levels of wood burning.
The focus now though is nitrogen dioxide (NO2) mainly from diesel engines and how that can be reduced.
London Mayor Sadiq Khan estimates thousands of Londoners every year have their lives shortened by pollution.
Ironically, London is probably at the forefront of anti-pollution policy.
We have had a low emission zone for many years and have tried green walls and dust suppressants for example, with limited success. But the capital still breaches pollution limits.
London air pollution
Premature deaths a year in London linked to air pollution
500,000 aged under 19 who live in areas that breach EU limits
443 schools that have unsafe pollution levels
86 of these are secondary
2025 year London is expected to meet EU limits
Pollution is also now very prominent in the minds' of the public - for one thing, it receives a lot more publicity than it used to.
The response to a recent mayoral consultation on pollution was the highest ever.
And while many ideas are touted to reduce pollution, the real solution, clean air campaigners will tell you, is to reduce emissions and even ban diesels.
But something interesting is happening in the wider court of public opinion. Changes are happening in the vehicle market.
Yesterday, it was announced the sales of diesel cars dropped 9.2% compared to a year ago. That was combined with a record 48.9% increase in electric cars and other alternatively-fuelled vehicles.
And while this is not a pollution solution, drivers' behaviour is changing and it seems diesel is in decline.