Calne Air Quality Monitoring Data & UKHSA Public Health Risk Assessment

The UK Health Security Agency (UKHSA) has now completed and published a public health risk assessment using data collected by the Environment Agency's Mobile Monitoring Facility (MMF) in the Calne community, located at Priestley Primary School.

The MMF provides continuous air quality monitoring, including measurements of hydrogen sulphide, methane and particulate matter concentrations. We recognise the community's desire for transparency and openness; therefore, the full ratified dataset used to inform the assessment is available on our website.

The full UKHSA report, together with an executive summary, can be accessed here:

UKHSA PHRA Summary

UKHSA PHRA Full Report

We have also provided the Environment Agency Study of Ambient Air Quality at Lower Compton:

Environment Agency Air Quality Study

MMF Air Quality Dataset (Excel)

We, Wiltshire Council and UKHSA have also prepared a Questions and Answers (Q&A) to help explain the findings and address some of the questions residents may have when reading the report.

The ambient air monitoring data produced by the Environment Agency, and analysed in this report, shows that there is a source of hydrogen sulphide and methane in the direction of the Lower Compton Landfill Site. 

This confirms the findings of our inspections and off-site odour assessments, and supports the Environment Agency’s regulatory decisions, including requiring Hills to bring capping works forward and change the ways they manage odour.

Community Drop-in Event 21 July 2026

We are hosting a multi-agency drop-in event where residents can discuss the report's findings directly with representatives from the agencies involved in responding to the odour issues in Calne.

Calne Landfill Odour Response Drop-in Event

Date: 21 July 2026
Time: 4:00pm – 7:00pm
Location: Large Hall, Calne Town Hall, SN11 0EN

Representatives from multiple agencies will be available to answer questions and provide information:

  • Environment Agency - Air quality monitoring, monitoring methodology and site regulation. Contact: wessexenquiries@environment-agency.gov.uk
  • UKHSA - Technical findings of the UKHSA assessment and further information on UKHSA advice. Contact: enquiries@ukhsa.gov.uk
  • Wiltshire Council – Environmental Health Team and statutory nuisance investigations. For more information: www.wiltshire.gov.uk/article/1833/Smells-and-odours
  • Health concerns, medical advice and Public Health issues – Wiltshire Council and UKHSA advise if you have any concerns about your health, please contact your GP or NHS 111 for individual medical advice in the first instance. If you have any further public health-related queries, you can email Wiltshire Council Public Health at publichealth@wiltshire.gov.uk, who can help direct your query to the most appropriate organisation for a response.
  • Hills Waste Solutions – Site operations. Contact: www.hills-group.co.uk/contact-us/

About the Monitoring Programme

The monitoring location at Priestley Primary School was carefully selected using a range of factors, including prevailing wind patterns, the predicted movement of landfill emissions and the geographical distribution of odour reports received from the community.

In addition to measuring air quality, the Mobile Monitoring Facility collected meteorological information such as wind speed, wind direction, temperature and atmospheric pressure. This data helps us understand when emissions may have occurred and whether they could be linked to landfill operations.

The monitoring programme supported our extensive field observations from Environment Agency officers who responded to odour reports across the community. Together, these sources of information have provided a comprehensive evidence base to support our ongoing regulatory work.

You can read more about the monitoring programme in our Questions and Answers.

Environment Agency regulation

The Environment Agency is responsible for regulating the landfill site and ensuring compliance with the conditions of its environmental permit.

As the environmental regulator, we have taken extensive action to require Hills Waste Solutions to address the source of the odour affecting the Calne community. These improvement works are now nearing completion.

We will continue to regulate the site closely and will take further enforcement action where necessary to ensure permit compliance and minimise environmental impacts.

Responsibility for investigating odour nuisance sits with Wiltshire Council. Public health matters are the responsibility of the UKHSA and Wiltshire Council through their director of public health. We will continue to work closely with both organisations.