Student uses urban moss to monitor lockdown pollution levels

We don’t talk about Polycyclic Aromatic Hydrocarbons(PAHs) often but a PhD student at the University of Aberdeen has brought them into the spotlight, having found that moss can act as an effective way of monitoring this pernicious pollutant.

There are multiple sources of  PAHs and road traffic is a substantial one. At the other end of the scale, incense is also a source. The main danger associated with exposure to PAHs in humans is cancer, while cardiovascular disease and poor fetal development have also been linked.

Thomas Daniya with his daughter Beomhinya who helped him collect moss samples as part of his study.

Thomas Daniya, a PhD student at the University of Aberdeen, had planned to set out study how common plant species could help measure PAH levels in different cities but, when Covid landed, he found himself restricted to the Granite City.  

In Aberdeen he turned his attention to moss, collecting a total of 120 samples between June 2020 and May 2021 from ten localities representing five different types of site.

Throughout the year a variety of travel restrictions were in place, allowing Thomas to compare how PAH levels were affected by different levels of traffic.

Thomas explains his findings: ‘When travel restrictions were enforced, car usage significantly decreased. So each fluctuation in Aberdeen’s Covid-19 restriction level became an unplanned experiment, allowing me to examine the impact of cars and traffic on PAH.

‘One of the most intriguing findings was the variations between different localities. While I anticipated that roadside mosses would contain significant levels of PAH, the same was true of residential areas when restrictions lifted and regular travel activity resumed.

‘In some of these residential areas the PAH levels in mosses went from very low to having as much PAH as mosses growing next to busy roads, which was very surprising and demonstrates just how much impact individual travel decisions can have on local air quality.’

Of particular note was that mosses from residential car parks, which were a sufficient  distance from main roads that they might have been expected to be less exposed to passing traffic, had the highest PAH concentrations during periods without travel restrictions.

Thomas’s PhD supervisor, Dr Stephen Bowden, added: ‘Thomas’s research highlights the potential for mosses as accessible and efficient indicators of urban air quality, providing valuable insights into the effects of travel restrictions on pollution levels.

‘This innovative approach creates new opportunities for widespread monitoring of PAH by citizen scientists, which could lead to a deeper understanding of the connection between individual behaviours and environmental quality.

‘This could be especially useful in terms of measuring the potential impact of low emission zones and other environmental initiatives in town and cities worldwide, contributing to the evidence available to policymakers responsible for improving local air quality.’

The full research can be read here