Foul smell 'an annoyance' but not a health risk

A bad smelling gas at a landfill site which has reportedly been causing headaches and nausea for locals does not exceed UK air quality standards but does at times exceed World Health Organization (WHO) guidelines, experts say.

It comes after the Environment Agency (EA) monitored the Lower Compton site in Calne, Wiltshire, for six months amid thousands of complaints.

The UK Health Security Agency (UKHSA) said the gas showed a "minimal" long-term health risk, however hydrogen sulphide (H2S) - which smells "eggy" - was at times excessive.

UKHSA South West's Lucy McCann said there was "odour annoyance" but no "toxicological risk". Hills Waste said it had increased clay capping and gas wells.

The overall monitoring results for particulate matter, methane and H2S did not exceed the relevant standards or health-based guidance values.

However, from 15 October 2025 to 16 April there were 106 occasions recorded where the H2S concentration exceeded the WHO "odour annoyance" guideline level of 7 μg/m3 (micrograms of H2S per cubic metre of air).

McCann said some people may be more sensitive to H2S odour than others and anyone with concerns should contact their GP.

"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," McCann said.

The EA's findings supported its previous decision to require Hills to bring capping works forward and change the ways it manages odour.

In May, the EA also deployed heat-seeking drones to identify "gas hotspots" that may be causing the smell.

The EA's Ben Shayler said: "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."

Hills said it welcomes the report and has been working with the EA consistently.

"Since May, Hills has accelerated the rate at which completed areas of landfill have been clay capped

"Hills is also increasing the number of gas wells at the landfill with captured emissions being used for the generation of electricity," the spokesperson said.

A community drop-in event - where residents will be able to discuss the findings with representatives from the EA, UKHSA, Wiltshire Council and Hills - is set to take place at Calne Town Hall on 21 July.

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