Bristol’s air pollution

Our scientists have revealed why we cause air pollution and carbon emissions in Bristol through our transport choices. Surprisingly, car travel to shopping and leisure activities contributes over half of our emissions – that’s more air pollution than through commuting and business travel.

Across all ages, genders, and income brackets, leisure-time activities generate the most emissions of nitrogen oxides (NOx) and PM10 (40%)*. The data also shows that people use different modes of travel to get to different activities and places – it is less likely to only use one form of transport for all activities. This is despite most current efforts to change travel behaviours being focused on rush hour travel, when people typically commute to and from work.

Air pollution causes five deaths per week in Bristol. Poor air quality disproportionately harms children and the elderly, causing respiratory diseases, cancer and exacerbating heart conditions. Bristol City Council is legally required to reduce air pollution levels and has recently released a Clean Air Plan.

The activities polluting our air are also the same ones producing carbon emissions – the major cause of climate change. Reducing carbon emissions in cities is critical to achieve major cuts in carbon globally, so reducing climate risks. Bristol City Council and the surrounding authorities have pledged to be carbon neutral by 2030.

Air pollution is a social justice issue

We also looked at what demographic groups create the most emissions. 26-49-year olds produce the most air pollutants, through greater use of their cars for leisure activities and commuting to work.

People with higher incomes travel more often by car than those from lower incomes – resulting in higher emissions. The overall proportions for travel to each activity stays the same, but the amount of travel, and therefore emissions, increases. This means that richer people travel by car to more work locations, more leisure activities, and more business trips.

Bristolian men contribute 10% more to road NOx emissions than Bristolian women (40% vs 30%). This is largely due to the fact they use their car for commuting and business more. Women and men contribute about the same NOx from buses, although they use them slightly differently.

How did we work this out?

A fine granular dataset of road transport emissions was generated that allowed source allocation not only at the typical level of travel choice (e.g. car, bus, taxi, cycling, walking etc) but also the underlying behaviour or motive (e.g. shopping, commuting, leisure etc) and socio-economic properties of the people travelling (e.g. gender, age, income etc). The scientists say the scientifically robust yet flexible methodology is designed to allow it to use different types of public datasets, which can be applied to different cities in similar fashion. Two produce these findings, they followed two steps:

  1. Create a network model of the city to understand traffic flows at links in road networks to calculate total emissions; and
  2. Merge the emission dataset from step 1 with national travel survey data, which include information on the underlying motives and socio-economic data of travellers of individual trips.

So now what?

Professor Enda Hayes of the Air Quality Management Resource Centre at UWE, Bristol is one of the lead researchers. He explains: “Traditional air quality and carbon policy has often been orientated towards addressing peak travel (i.e. morning and evening commuting) but this evidence helps to reformulate the air quality and carbon policy debate so that societal behaviour and the need for societal change becomes central to achieving low carbon, healthy futures for our cities”.

ClairCity has been involving city residents in future policy ideas since 2016.  Policy suggestions will be combined with citizen preferences and aspirations, in order to generate sophisticated future scenarios that model the options available to each city. This unique approach is raising awareness of air quality in our cities and ultimately allows us to work towards a future with clean air.

We can all make a difference to air pollution. There’s individual changes, such as choosing to change the way we get around the city; collective choices such as working with parents, colleagues, friends or campaign groups to influence group behaviour (e.g. walk to school clubs, cycle to work schemes); or systemic changes made by policy and law makers. We need change on every level – where can you make the biggest difference?

To help you make a change we’ve produced some shareable graphics for you – please download and share widely!

* Nitrogen Oxides (NOx) is a common air pollutant that comes from the combustion of fuels, such as diesel in cars. Particulate Matter 10 (PM10)’s are airborne particles so small that they can penetrate our lungs. PM10 and PM2.5 (even smaller) mainly derive from road transport, such as the dust that is released when we break, from tyres, road dust or from soot from exhausts.

Download our PDF full of shareable graphics – Tweet, post and print till your heart’s content!