Hidden Figures

Am I breathing illegal levels of air pollution? Basically, yes. That’s what the 2018 Clean Air Zone consultation was all about. But even if we can actually ‘limbo dance’ under the legal limit, scientists have made it pretty clear:

There is no safe level of air pollution.

In other words, we need to drastically clean up our air, not just try to achieve an arbitrary legal limit based on averages. Daily spikes in air pollution are also really damaging to health, especially if you are more vulnerable to its effects. In Southampton this relates to more people than you might think:

  • children (24% of the population);
  • older people i.e. 65 years+ (13%);
  • those with existing health problems – by the age of 45-49 years, over half of Southampton registered patients have at least one chronic health condition; and
  • Over 45% of Southampton’s population live in neighbourhoods within the 30% most deprived nationally (around 117,000 people).

What’s the air quality like on my street? In 2019 we partnered with the University of Southampton to install 11 particulate matter sensors in and around St Denys. We are producing real-time data on local air pollution, including Portswood High Street and across the river in Bitterne Park and Bitterne. We found that ‘quiet’ streets are no guarantee of clean air and it’s essential that air pollution is tackled on a city-wide scale.

There are also a handful of Government monitoring stations in Southampton which measure and record real-time levels of pollutants – e.g. Nitrogen Dioxide (NO2) and particulate matter (PM10, PM2.5) – and a number of diffusion tubes which take a monthly average of NO2 levels across the city.

What do the graphs mean? In general they show how levels of different pollutants go up and down, both on a daily basis and due to seasonal differences during the year. Usually calculations are made in the middle of the following year to see whether the annual average has exceeded legal limits.

Image: Anna Shvets/Pexels

Was the air cleaner during lockdown in April? This is a tricky question to answer but across the country, levels of Nitrogen Dioxide fell to two-thirds of ‘business as usual’ levels. Unfortunately in Southampton, we only saw a slight improvement (8%) on the A33 and a 2% increase in the city centre. Levels of Ozone, another important pollutant, also rose across the country. A detailed analysis by a researcher at the University of Southampton can be found here.

If we look at the data from our particulate matter sensors in St Denys, comparing 2019 and 2020, there isn’t a great deal of difference in air quality over the period.

A graph comparing average levels of fine particles from our St Denys sensors Mar-May 2019 and Mar-May 2020

Why was Southampton such an air pollution hotspot during lockdown? There are lots of possible reasons for this: ships in port were still running their engines; being stuck at home many people were having barbeques and bonfires; and the lockdown period coincided with both strange meteorological conditions and the ‘Spring Smog’. This is an annual spike in NO2 concentrations from agriculture (from ammonia-based fertilisers) which are used in large amounts in both the UK and on the continent. Videos of air pollution moving across from Eastern Europe in early April from the EU Copernicus satellite can be seen here (scroll down to animations).

Screenshot from animation of satellite imagery over Europe – NO2 concentrations

Aren’t there laws which are meant to protect us from dirty air? Yes, but the limits they set need to be tightened. Concentrations of fine particles have plateaued in recent years, meaning that much more stringent measures are needed to protect our health. Having the WHO guidelines on PM2.5 enshrined in the Government’s upcoming Environment Bill would be a good next step.

Can we think more broadly, not just about clean air? Yes! Air quality can be a lever for change but considering routes to a more liveable city would also greatly help improve our quality of life. For example, most people would agree that having safer streets is a good objective. In Southampton, the rate of road traffic casualties is close to double the national rate and higher than cities of a similar size. So reducing the numbers of vehicles on our roads can only help to reduce this terrible toll.

And when you combine poor air quality with high numbers of injuries on our roads you create a city with some of the highest levels of deprivation for outdoor living environment in the UK. How is this acceptable in 2020?

Almost the whole of Southampton ranks very high on the Index for Multiple Deprivation in terms of air pollution and road traffic casualties (2019) https://data.southampton.gov.uk/Images/17-IMD2019-LE-Outoors-EngDec_tcm71-422242.jpg

Air pollution around schools in Southampton (map)

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