Rotten egg smell breached guidelines

Concerns over the smell were first reported in 2023

A rotten egg smell that has persisted for more than a year surpassed World Health Organization (WHO) "annoyance" levels, the Environment Agency (EA) has said.

An air quality monitor near the Aycliffe Quarry landfill site in County Durham recorded hydrogen sulphide over the WHO guidelines threshold for 16 hours and methane levels higher than normal background concentration.

The UK Health Security Agency said it "did not expect" any long-term health consequences, but said the unpleasant odour could cause discomfort and some short term health effects.

The quarry's owner said there were a number of other potential sources of the odour.

The EA air quality monitor in Brafferton village collected data for 98 days between June and September.

Hydrogen sulphide levels were detected above the WHO odour annoyance threshold of 7 micrograms per cubic meter for 16 hours out of 2,352, equating to 0.7% of the time.

WHO guidance states "odour annoyance" cannot be regarded as an adverse health effect in a strict sense, but does affect the quality of life.

The EA said the hydrogen sulphide had not been present at "any significant levels or for any concerning periods of time".

Its report said there was no health standard for methane in ambient air but the average concentration over the monitoring period was 1.8mg per cubed metre, which is above the northern hemisphere background concentration of approximately 1.31mg.

'Horrific' smell

Katie Louise, who lives in nearby Brafferton village, said: "We've had no apologies or any level of understanding from the landfill operator at any point."

She said the smells, which had been reported since 2023, had been "horrific" and had affected her and her family's mental health.

"We couldn’t open windows, dry clothes outside or use the garden," she said.

"It was made worse as we never knew when it would occur so you ended up dreading weekends."

Ms Louise also said the air monitoring results were an "unrepresentative snapshot".

"As a community we've felt hugely let down by so many groups and agencies - it really does feel as if the little person doesn't matter."

The EA said it was investigating Aycliffe Quarry, which is owned by the Ashcourt Group, after issuing an enforcement notice in February.

Ashcourt Group said the EA report did not identify the source of the odour.

It added it was close to finishing infrastructure works on the site.