FAQ's | BBC Pollution Postcode Checker 

Our MappAir® data powers the BBC's Pollution Postcode Checker. We have put together information pack to help you better understand the data used. 


1. The MappAir® Dataset


What is MappAir® & The Pollution Postcode Checker?

MappAir® is a global map of ambient air pollution.

The MappAir® data used to power the pollution postcode checker on the BBC website provides a strong indication of pollution from traffic which has been averaged over the year (2016) for an area (postcode) and cannot be used as a site-specific measurement. 

The postcode checker service used on the BBC website is based on a dataset of air quality at 100m x 100m resolution.

Within each area, there will be a combination of pollution peaks and troughs. Roadside hotspot measurements of Nitrogen Dioxide [NO2] pollution will naturally be higher for residential postcodes for instance, simply because busy roads will normally have more vehicular emissions than quiet streets near houses. (There will always be exceptions, see next FAQ).


How Will This Affect My Postcode Average?

Therefore, the postcode average will probably provide a lower indicative figure than roadside measurements which have been taken in the area, near traffic vehicles and their exhaust emissions.

MappAir® is designed to be indicative of concentrations around houses and gardens in addition to roadside levels, giving a comprehensive, indicative figure for your area.

What is a Pollution Hotspot?

This is an area where pollutant concentrations can be significantly higher

than expected and will merit further investigation.


Our Zephyr® air quality sensors would be perfectly suited to this purpose, which is exactly what the residents of King’s Heath Birmingham, did. Knowing where these hotspots are will help with avoiding them or even provide the evidence needed to introduce clean air initiatives around

your area.


Where Does MappAir® Data Come From?

Our MappAir® data is modelled from a variety of data sources including road traffic data, satellite information and street map data.

It uses best available data sources, but those will be limited in varying ways in their ability to provide detailed information. Each data source is subject to its own variations due to weather, seasonal changes and daily patterns of traffic. Local variations can be attributed to other emission sources and topography which we do not currently capture in the 2016 dataset.


Why is MappAir® Useful to Me?

MappAir® is a revolutionary product that aims to make air pollution data accessible to anyone in the form of an easy-to-use map. This means that you have the information to make active choices on how best to protect yourself and your family. We can also help your community to enforce that change by working with local councils and central governments.

2. Pollution Categories used in the Postcode Checker


My postcode check says I live in a Category 1 area, what does that mean?

Category 1: The air in your area is generally clean and well below the legal levels for pollutants such as NO2.


Does That Mean I’m Safe?

We are all only as safe as we make our air, it is a complex interplay of many factors including the weather, topography, vehicle and fuel type, and the factors discussed above.


Traffic emissions are consistently found to be the main cause of toxic NO2 emissions, and being a man-made source, we can easily do something to make the air safer for everyone. 


My postcode check says I live in a Category 2 area, what does that mean?

Category 2: The air in your area is generally cleaner than the regulatory limits and should not cause health concerns except in exceptional weather conditions.


My postcode check says I live in a Category 3 area, what does that mean?

Category 3: The annual average concentrations of pollutants in this area are likely to be marginally above the regulatory guidelines. In stagnant weather conditions, peak traffic flows may cause higher levels which merit some caution.


Health studies suggest a marginal health impact for most individuals in these conditions. Please check Public Health England for up to date information.

My postcode check says I live in a Category 4 area, what does that mean?

Category 4: There are likely to be regular episodes of moderate pollution in these areas, with annual average concentrations above regulatory guidelines. Sensitised individuals (e.g. Asthma sufferers) should manage exposure and exercise levels accordingly and there are likely to be some health impacts of long-term exposure.

All of us will have some exposure to air pollution some of the time, as we share our air. This category highlights trends in pollution over time, (ie: traffic jams) helping vulnerable people to plan around these areas.


My postcode check says I live in a Category 5 area, what does that mean?

UK wide, air pollution in terms of NO2 seems to be slowly improving, particularly as we move away from diesel and petrol car models. It is precisely for this reason that more needs to be done, and quickly!

Category 5: Pollution concentrations in this area are likely to frequently exceed WHO guidelines and regulatory limits. Annual average concentrations are highly likely to be above 40 ug/m3 of NO2 with associated health impacts. Residents should monitor air quality forecasts and manage exposure appropriately. Always check with your GP if in doubt and stay informed.

My postcode pollution reading doesn’t seem to match my experience of air pollution in my area.

The dataset is modelled data and is averaged over the whole year so will not directly relate to your day to day experience. As it is modelled data it can only provide a generalised and not highly detailed view of the air quality in your local area.

Additionally, the MappAir® data used provides a modelled indication of the traffic pollution at the postcode level and, although we use the best data sources, it has certain limitations due to available data.


We are planning to release improved versions throughout the year, including a particulate dataset, cumulating in near real-time data which will provide better indications as to the pollution level.  We are also aiming to include other emission sources.  


We recommend signing up to our mailing list so you can hear about future data releases.


3. What can I do? 

If you are concerned about actual measurements in your local area, we suggest you talk to your local council. 


You can also take similar action to the King’s Heath CAN project (Fighting for Air BBC Programme) where a community came together and accurately measured air pollution using Zephyr® sensors in the specific areas they were concerned about. The community action group put into place various interventions including planting shrubs, closing roads to vehicles and worked with local bus companies to arrange free travel to the High Street and reduced air pollution by 20% in just one day.