Research and analysis

Thermal transport of air pollution from regulated industries: summary

Published 23 February 2026

Applies to England

1. Chief Scientist’s Group report summary

This project explored how certain local weather patterns - thermal flows such as sea breezes, warm city air, or cold air flowing downhill - can affect how air pollution is transported by the wind from industrial and waste sites.

The project used real-world examples, data analysis, and computer modelling to explore how often these weather patterns occur, how much they impact air quality, how they might change in the future. We also considered how current assessment methods might be refined to take them into account.  Current Environment Agency regulatory processes were checked to determine if they consider thermal flows, and the project explored how some processes might be refined to take more account of them. This work can be used to inform Environment Agency decision-making about industrial activity, pollution monitoring, and how to better protect communities and the environment.

1.1 Background

Air pollution is one of the biggest environmental threats to health in the UK, contributing to tens of thousands of deaths each year. The Environment Agency plays a crucial role in controlling such pollution from major industries and waste sites. We check that emissions and ambient levels of air pollution are kept within safe limits by conducting monitoring and/or using models to assess and/or predict how air pollution moves locally. However, basic models often rely on simplified assumptions, like flat terrain and typical weather conditions, and so may sometimes overlook details that may be significant; in certain situations, local factors can influence winds and so change how air pollution spreads.

This project looked at once such factor, local thermal flows driven by differences in temperature. These may lead to unexpected pollution hotspots, especially near industrial sites, coasts, in hilly areas or in urban areas. As climate change and urban development continue, these thermal flows are likely to become more common and more significant.

1.2 Approach

The project used a mix of research methods. These included reviewing existing scientific studies, consulting with experts and stakeholders, analysing monitoring data, and running atmospheric dispersion models (computer simulations that predict how pollutants spread in the atmosphere).

Published research was reviewed to understand what is already known about local thermal air flows and how they influence pollution. This was supported with a survey of 23 experts and practitioners to gather real-world experiences and identify practical needs.

Monitoring data from relevant sites across England were analysed to assess how often thermal flows occur and how strong they are. This helped identify where and when they might be most impactful. Case studies from coastal and inland sites were used to identify what information might help predict when thermal flows occur.

Data from these case studies were also used to explore the performance of dispersion models. The performance of a standard commercial regulatory assessment model was compared against a modified version of that dispersion model. The project also evaluated the performance of an experimental model normally used for exploring thermal comfort in cities, and of a simple topographical analysis that used existing Environment Agency tools to predict flows of cold air at selected case study sites.

Finally, the findings were shared with stakeholders through workshops to explore how this new knowledge could be used in practice. These sessions helped shape ideas for new tools and guidance to support better decision-making.

1.3 Results

The project found that local thermal flows can significantly affect how air pollution spreads locally from industrial and waste sites. They can carry pollutants in unexpected directions, so that elevated concentrations sometimes occur in areas that conventional models would not predict. This means that people living near these sites could be exposed to higher levels of pollution than previously thought, especially under certain weather conditions.

This research also showed that current techniques used to assess air quality do not sufficiently account for these local effects. More advanced models can do this, but they require detailed data and are more complex to use. However, advanced modelling is not always essential to make improvements, because relatively simple methods can indicate how air pollution may move in thermal flow situations.

Stakeholders expressed a clear need for better guidance and simple practical tools to help them consider thermal flows in their work, and therefore the project explored simple approaches that would indicate where local thermal flows could occur and what their impact might be.

While the project provided valuable insights, there were some limitations. More UK-specific research is needed. Some types of thermal flows, like those caused by urban heat islands, were harder to study due to limited data. The models used in the project could not fully capture complex or changing air movements; more work is needed to improve their accuracy and usability and to determine where more sophisticated models might add sufficient value to offset the extra work involved in using them.

1.4 Conclusions

This research shows that local differences in air temperature can significantly affect how pollution spreads from industrial and waste sites. These effects are often overlooked in standard assessments, which means local pollution risks may be underestimated in some areas.

The findings are especially relevant for people involved in regulating, planning, and assessing industrial activities. For the Environment Agency, this means having a clearer picture of when and where pollution might travel in unexpected ways. This can help improve decisions about land-use planning, site permitting, pollution monitoring, and responses to complaints from nearby communities.

The results also offer practical insights for consultants, local authorities, and developers. By understanding how local thermal flows work they can better assess risks when planning new housing or industrial development, especially in coastal areas, valleys, or near cities.

Overall, the findings highlight the importance of considering thermal flows in local air quality assessments and the need for better guidance, tools and data to support this.

1.5 Publication details

This summary relates to information from project SC240014, reported in detail in the following outputs:

• Report: SC240014/R1

• Title: Thermal transport of air pollution from regulated industries: project summary and overview of key findings

• Report: SC240014/R2

• Title: Thermal transport of air pollution from regulated industries: a quick scoping review

• Report: SC240014/R3

• Title: Thermal transport of air pollution from regulated industries: stakeholder consultation 

• Report: SC240014/R4

• Title: Thermal transport of air pollution from regulated industries: case studies on thermal flow conditions

• Report: SC240014/R5

• Title: Thermal transport of air pollution from regulated industries: exploring application and implication of outcomes.

• Project manager: Philippa Douglas, Chief Scientist’s Group.

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency