MPs pledge to investigate toxic gas from animal farming

Farm muck gives off ammonia, a gas that can mix with others in the air and become toxic to humans and harmful to wider ecosystems.

In 2024, TBIJ and the ‘i’ newspaper revealed that ammonia emissions linked to industrial-scale chicken farming were surging in parts of the UK. It was front-page news and raised concerns about how the health of people living near the farms could be affected.

Now, MPs will investigate. As part of the environment audit select committee’s inquiry into air pollution, MPs will look into how pollution affects different parts of the country. And it will look into ammonia from agriculture specifically.

We found that, while ammonia levels had fallen nationwide since 2017, they had risen sharply in areas with large numbers of US-style factory farms. These included part of Wales, Norfolk, Lincolnshire and counties surrounding the River Wye.

“The more farms you add in an area, the more total ammonia is released,” said an employee at an environmental regulator. “This is a real weakness as you do not have a single ammonia emission limit set [for the region].”

Announcing the inquiry last month, Toby Perkins MP, the committee’s chair, called air pollution “a scourge of our precious natural environment and a profound threat to our health”. He said that it disproportionately affected some of society’s most disadvantaged groups and that any just transition to a net zero society needed to tackle the problem urgently.

The committee will explore whether the government’s air quality targets are enough to protect our health and the environment. It’ll also examine other farming practices linked to air pollution, including the spreading of slurry – liquid livestock waste often used as fertiliser – on farmland. It will consider evidence submitted via the parliament portal until March 3.

Inquiries like these normally publish a report on their findings, including recommendations for policy changes. This puts pressure on the relevant minister to respond, but they aren’t required to act on the advice. We’ll be submitting the evidence from our reporting.

Experts and campaigners have called for restrictions on new chicken farms in areas with already high numbers of farms.

“With US-style megafarms on the rise in the UK, blighting our communities, we applaud the environmental audit committee’s decision to include air pollution linked to agriculture in the scope of its inquiry,” Natasha Hurley, deputy director of the campaign group Foodrise, told TBIJ. She added that the companies polluting our air must be held to account.

Professor Alistair Lewis, from the National Centre for Atmospheric Science at the University of York, said: “Whilst there has been visible progress in reducing emissions of pollutants such as nitrogen dioxide, as cars and lorries have got cleaner and electrified, some less obvious pollutants such as ammonia have seen little improvement over the last decade.”

Ammonia comes mainly from farming but it reacts in the air with other pollutants to form PM2.5, tiny particles so small they can penetrate deep into the lungs and enter the bloodstream. A surprisingly large amount of PM2.5 breathed in by people in UK cities has some of its origins in farming emissions, Lewis said.

However, leaders in the poultry industry said the situation was complicated. “Ammonia emissions are influenced by a range of factors, including housing design, weather conditions, and mitigation technologies,” said Richard Griffiths, chief executive of the British Poultry Council. He added that modern units are designed with pollution controls built in, and the industry had invested significantly in improvements.

Griffiths also said that although there was a 1% increase in emissions from intensive farms between 2023 and 2024, there was a clear, long-term decline in emissions from these sites in the past 10 years. “The poultry meat sector accepts responsibility for managing its emissions, but we do not accept the claim that there is an automatic relationship between the number of poultry units and pollution. The focus should always be on outcomes and effectiveness of mitigation measures, rather than assumptions based solely on scale,” he added.

Professor Mark Sutton, from the UK Centre for Ecology & Hydrology, said: “Intensive poultry farms are both a threat and an opportunity. The threat comes from their expansion, increasing emissions with major local impacts on biodiversity, as they are among the largest point sources. At the same time, the economies of scale for such large farms mean that it is easier to implement cost-effective ammonia mitigation measures.”

Back in 2024, Sutton told us that the problem of ammonia pollution wasn’t just confined to large farms. Small farms don’t always have to report their emissions, but when they end up clustered together in an area, there’s a higher risk that their combined ammonia pollution will rise to the level that affects nature, he said. For that reason, he wants local planners to take this into account when approving applications from small farms.

A Defra spokesperson said: “We are committed to reducing ammonia emissions from agriculture, which are harmful to nature and human health. We will continue to work with farmers and the wider sector on practical solutions.”

Experts, non-government organisations and members of the public can submit evidence to the inquiry. The committee has not yet announced a timeline for its report.