"AIR QUALITY INDICATORS" (AQIs) - WHAT THEY MEAN
Because I use the Plume Laboratory "Flow" device for monitoring and reporting on this website, here is what they say about each band/colour:-
GREEN: 0 - 20 LOW POLLUTION.
The air is clear - perfect for outdoor activities! Pollution levels are under the recommended exposure thresholds set by the World Health Organisation (WHO) for one year of pollution exposure. Nothing to worry.
AMBER: 21 - 50 MODERATE POLLUTION.
Air quality is considered acceptable, though over the recommended WHO threshold for one year. This means that, unless you have these kinds of conditions all year round, you shouldn't be experiencing adverse health effects. However, there may be certain health concerns for people with specific sensitivities. Always consult your physician!
RED: 51 - 100 HIGH POLLUTION.
The is highly polluted - above twenty-four hour exposure recommendations from the World Health Organisation. Everyone may start to feel adverse health effects, and those with sensitivities should take care when performing outdoor activities.
PURPLE/VIOLET: 101+ VERY HIGH POLLUTION AND ABOVE
Everyone may start to experience more serious health effects at these levels, and long term exposure constitutes a real health risk. Levels have exceeded the recommended WHO exposure threshold for one hour.
In certain regions, or during exceptional pollution peaks, you may experience higher levels of pollution over 200 or even 300. These warnings constitute emergency conditions. There can be harmful impacts on the general public, even in the case of short-term exposure. All individuals should avoid physical activities until pollution subsides, regardless of sensitivities.
The Greenstreet position summarised - "always polluted"
Every day since 22nd February 2019, the lowest pollution we have experienced is Amber/Moderate Pollution. That means that anyone whose health is already under stress from chronic conditions or those who are very young will be suffering additional health burdens with each passing day.
The data collected so far records many episodes of much higher pollution that can harm our health over much shorter periods of only 24 hours or even one hour. Check out the Pollution Diary. This is certainly associated with the congestion we experience regularly - with the future seeing more pollution as the road struggles to cope with added traffic of all types and at all times.
Exceedances: There have been "exceedances" for all pollutants (Particulate Matter, NOx and VOCs) take a look at the Pollution Diary!
UK and EU Standards
"Air UK" (DEFRA) provides a good summary of where the UK currently stands with standards and thresholds. Follow this link ...
Here is the UK/EU example of how colour-coding is helpful - even if the scales differ, the colours mean the same. A simple idea and really helpful if you just want to know "is it bad or not?"!