Every day, satellites pass over the UK measuring the amount of ammonia gas in the atmosphere. Ammonia is a powerful pollutant because it combines with other pollutants in the air to create very small particles, known as PM2.5, which are harmful to human health when inhaled.

Ammonia is released into the atmosphere from the storage and spreading of cattle manure, slurry and nitrogen fertilisers. According to Defra, 87% of ammonia released into the air comes from agriculture, much more than from industry. Defra reports that cattle are the largest source, and that the number of dairy cattle and emissions have risen over the past decade. Devon is home to more cattle than any other county in England.

Agricultural ammonia, made up of nitrogen and hydrogen, reacts with pollutants from vehicle exhausts to form PM2.5. Ammonia emissions are carried for days on the wind causing high PM2.5 in both rural areas and in cities. Ammonia from rural agriculture is now the main source of particulate pollution in UK cities. The government calculates the health costs from these particles at £8 billion a year.

The human costs of ammonia pollution and PM2.5 are cardiovascular and respiratory disease, COPD and reduced lung function, lung cancer, bronchitis and increasing rates of asthma in children in agricultural areas. When air quality is poor, symptoms of eye, nose and throat irritation, coughing, sneezing, runny nose, and shortness of breath can be mistaken for hayfever.

Ammonia in the air also pollutes the environment by depositing excess nitrogen across the landscape raising the acidity and nitrogen concentration in the soil which suppresses wild plants, reducing plant biodiversity and the insects and animals that depend on them. Moorland habitats, like Dartmoor, are particularly vulnerable to ammonia emissions.

Nitrates and phosphates in the run-off from livestock manure and fertilisers cause eutrophication of our rivers and lakes, where excess nutrients increase algae growth, removing oxygen from the water, killing fish and aquatic organisms. Concentrated animal waste also contaminates river water with pathogens.

There are multiple health and environmental benefits from tacking agricultural ammonia. Other parts of Europe have for years had stronger regulations on the amount of manure and fertiliser that can be applied. The Netherlands and Germany require manure to be injected into fields rather than sprayed on the surface, cutting ammonia emissions in the Netherlands by 64%.

In 2022, the Environment Agency reported that Devon farms are not even meeting the UK’s weaker regulations on slurry storage and manure spreading, and that livestock numbers in the county exceed the capacity of the land to absorb their waste.

If the UK Government is to meet its modest commitment of reducing ammonia by 16% by 2030, better monitoring and enforcement of the rules is needed. However, if the government is genuinely committed to curbing farm pollution and improving public health, it needs to support farmers to reduce livestock numbers to the carrying capacity of the land.