A long-awaited public health assessment into the "Calne Pong" has found there is minimal risk to public health from a toxicological perspective.
However, it also concludes that periods of odour may cause temporary symptoms for some residents and recommends further action to reduce off-site odours.
The independent assessment, carried out by the UK Health Security Agency (UKHSA), is based on air quality monitoring undertaken by the Environment Agency between 15th October 2025 and 16th April 2026 near Lower Compton Landfill.
The report found that levels of hydrogen sulphide, methane and particulate matter remained below the relevant health-based guidance values throughout the monitoring period. However, it also found there were periods when hydrogen sulphide exceeded the World Health Organization's odour annoyance guideline.
In simple terms, the report says the smell is unlikely to cause toxic health effects at the levels measured. However, it accepts that the odour itself can be unpleasant enough to cause temporary symptoms for some people and recommends further action to reduce it.
UKHSA says that during those periods, some people living near the site may experience temporary symptoms including headaches, nausea, dizziness, watery eyes, a stuffy nose, an irritated throat, coughing, sleep disruption and stress. It adds that people with pre-existing respiratory conditions may be particularly affected and that some individuals are more sensitive to hydrogen sulphide odour than others.
The report concludes: "Overall, the results for H2S and the other substances monitored do not indicate an exceedance of the relevant standards or health-based guidance values. Based on the monitoring data provided in the EA report... UKHSA concludes that there would be minimal risks to public health at these levels of exposure from a toxicological perspective."
The full assessment also states that directional analysis showed the highest concentrations of hydrogen sulphide came from the direction of Lower Compton Landfill. The Environment Agency said the monitoring results confirm its own inspections and off-site odour assessments, supporting previous decisions to require Hills Waste Solutions to bring forward capping works and change the way odour is managed at the site.
UKHSA has recommended that all appropriate measures continue to be taken to reduce off-site odours from the landfill site. It also advises residents with concerns about their individual health to contact their GP.
Residents in parts of Calne have reported odour issues, commonly referred to as the "Calne Pong", for many months. Earlier this year, the Environment Agency said air monitoring and site inspections indicated the source of hydrogen sulphide and methane was in the direction of Lower Compton Landfill. It required Hills Waste Solutions to bring forward capping works and make changes to the way the site is managed.
The Environment Agency has announced it will host a community drop-in event at Calne Town Hall on Tuesday 21st July, from 4pm to 7pm.
Representatives from the Environment Agency, UKHSA, Wiltshire Council and Hills Waste Solutions will be available to answer questions about the report, air quality monitoring, the work being carried out at the landfill site and public health.
Environment Agency Area Environment Manager Ben Shayler said: "This drop in event will give residents the opportunity to understand the work we are doing to regulate Hills, and ask questions of the agencies involved.
"We have taken extensive action to require Hills to address the source of the odour, and these works are now nearing completion.
"We will continue to regulate the site closely and monitor to ensure the works have been effective."
Lucy McCann, Consultant in Health Protection at UKHSA South West, said: "UKHSA has reviewed the Environment Agency's public health risk assessment and provided an independent public health risk assessment. While there is no evidence of a toxicological risk, there is strong evidence of odour annoyance.
"Individuals can react differently to hydrogen sulphide (H2S) odour, and some people may be more sensitive to it than others. People living near the site may experience temporary symptoms including headaches, nausea, dizziness, watery eyes, a stuffy nose, an irritated throat and coughing. Those with pre-existing respiratory conditions may be particularly affected, and some residents may also experience sleep disruption and stress.
"If you have concerns about your individual circumstances and require health advice, please contact your GP."
The Environment Agency says the improvement works required at the landfill site are now nearing completion and that it will continue to regulate the site closely, taking further enforcement action if necessary to ensure compliance with the site's environmental permit.
Residents wishing to discuss the findings or ask questions are invited to attend the drop-in event at Calne Town Hall on Tuesday 21st July between 4pm and 7pm.
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