If you subscribe to the AirText messaging service you will have received a number of SMS alerts recently saying “MODERATE air pollution”.
Notice how their website calls them Air Quality Alerts, thus leading one to think that quality is moderate, leading people to think that it is not so bad.
Indeed, why use the word “moderate” rather than “medium” or indeed “poor”?

Let’s assume you want to clear this bullshit fog with actual numbers and guidelines.
Sadiq Khan has made Air Quality his spitzen policy, so let’s see how he communicates with citizens. His policy page is here. The only map does not show the dire situation of today’s air, rather “the Mayor’s air quality actions across London”.

What a stupendous piece of self-aggrandising bullshit! The information on it is useless. For instance, the “Current Air Quality Data” is actually three years old …

Khan awarded a contract to friends to set up the BreatheLondon network of monitors. These seem to record lower levels than the official monitoring stations. Notice how most official stations show a level of 3

whereas the BreatheLondon monitors are all 2s

The above screenshots were taken at the same time. We don’t know if the numbers are comparable (but if they weren’t, what is the point?).
Let’s look at London Air which has comprehensive data from all the main official monitoring stations in London. We can see for example that on Monday 23rd January 2023, the Horseferry Road station (which is right next to a school playground) recorded unacceptably high levels of both NO2 and PM2.5 particulates

The London Air website is fairly comprehensive, but it takes time to understand how to extract precise information. Its RSS feed of incidents of medium to high pollution events is no longer working.
What about other sources?
The BBC has for many years refused to provide accurate pollution information. Notice how wind, rainfall, temperature is measured accurately, whereas air quality just has an undefined badge, with uncertain provenance.

It is also probably wrong. At the same time the screenshot above was taken, another site, AQICN was calling air pollution in London “Moderate” – again that weasel word (If I find the asshole who started this ruse, I will give him a moderate smack in the head, and he will know what is coming)

AccuWeather uses data from PlumeLabs and this morning they were calling the Air Quality “Poor”, with PM2.5 at more than twice the safe limit (Where exactly?)

So we get a very mixed picture according to where we look, and numbers which are not easy to compare.
Knowing how slimy Khan is, we cannot help deducing that this obfuscation is deliberate. The reason is that if citizens knew exactly how bad sometimes the air we breath becomes, we would demand what other European cities do: forbid half or more of the drivers from using their poisoning vehicles at times of poor air quality.
But that takes cojones, which Khan does not have. So Londoners are told not to exercise outdoor, so that poisoners can keep on poisoning.