Red and orange are bad news.
Red and orange dots mean that the pollution at that site is breaking the national and EU limits for air pollution – specifically, for the average measurement of nitrogen dioxide. Yellow means the site is below the limit, but the locations are at risk of breaking the rule and so should be monitored. Overall, more than five deaths a week in Bristol are linked to air pollution. This number would decrease if our air pollution levels were lower.
The council monitors other pollutants as well and have ways to monitor hourly emissions to check for extreme pollution events. You can find out more on their website.
Air pollution is caused by a combination of factors. The first is how much air pollution is being emitted: how busy is the road. However, the level of air pollution also depends on how much the air is circulated or where the wind takes polluted air. So higher, windier places will tend to have less pollution, but low-lying places like Bedminster may have worse pollution.
The green/grey area on the map is the council’s “Air Quality Management Area.” This is where the council are most concerned about the level of pollution. The management area is the focus of their monitoring and action on air pollution. For Bristol, the council are particularly concerned about the levels of nitrogen dioxide (shown on the map) and the level of PM10, tiny particles that are small enough to get deep into our lungs and which is also significantly caused by diesel emissions.
The main cause of air pollution in Bristol is traffic, especially diesel engines. In recent research on Bristol specifically (see p.105 of this document) it was found that 40% of Bristol’s nitrogen dioxide emissions are from diesel cars. Buses and coaches cause 23% of emissions. Diesel LGV (light goods vehicles like delivery vans) cause 22% and HGV (big lorries) cause 11%. Even though bigger vehicles may use more fuel, their engines are required to meet tougher standards and there are fewer of them.
The council decide where to locate the monitors. They are not evenly spread across the city because the council concentrate them where two conditions apply: areas where they know we risk breaking the nitrogen dioxide limits; and near to where people are living. This means the sites are targeted at main roads and busy central areas, or where there have been concerns about hotspots.
This map currently shows the data from Bristol City Council. We are in contact with South Gloucestershire council to try to include their data on the map as well. If you want to find out more about air pollution in South Gloucestershire, please check the council website.
Anywhere with a red or orange dot on the map is a location that is failing to meet the national and EU standards for air pollution. The rule we are breaking is the “annual mean of nitrogen dioxide,” which is 40 µg/m3 (40 micrograms per cubic metre). The problem you can see is a chronic level of air pollution that is too high overall, rather than specific short-term incidents that might make it bad for a few days, but then fine the rest of the year. Air pollution is linked to heart attacks, strokes and other conditions affecting thousands of people in our city.