Nitrogen-based pollution driven by agriculture causing almost 200,000 years of ‘life lost’ every year

Air pollution is the single largest environmental threat to human health, with small particulate matter, less than 2.5 microns across (PM2.5), associated with severe impacts on every organ in the body. Now new research from the Centre For Ecology and Hydrology, published in the journal Science, shows that exposure to nitrogen-based air pollutants is on the rise globally.

Professor Mark Sutton, co-author of the research, has urged journalists and delegates at Cop26, “now is the time to rediscover nitrogen”.

The researchers found that nitrogen accounted for 39 per cent of global PM2.5 exposure in 2013, up from 30 per cent in 1990. In total, for that year, nitrogen emissions caused an estimated 23.3 million years of life lost, which the researchers said cost economies a total of $420bn (£311bn). In the UK, the research found that for 2013, nitrogen pollution resulted in almost 200,000 years of “life lost”.

A “significant” source of atmospheric PM2.5 is generated through agricultural use of nitrogen-based fertilisers, which release ammonia (a compound of nitrogen and hydrogen), which bonds with nitrogen oxides and sulphur dioxide to create the fine particles.

While nitrogen-based air pollution has long been recognised as a major concern, the new research reveals that one of the most cost-effective ways of cleaning up the air would be to reduce the levels of ammonia being released – largely through a shift in farming methods.

Prof Sutton explained, “What we’re saying is that during Cop26, now is the time to rediscover nitrogen again.

“You’ve heard about the carbon dioxide, you’ve heard about this big methane initiative, but action on nitrogen is needed too.”

According to the Centre For Ecology and Hydrology report, “The main opportunities for NH3 (ammonia) abatement concern agricultural sources, for which abatement measures are relatively easy and inexpensive.”

Agriculture is responsible for around 75 per cent of ammonia released by humans, and Prof Sutton said, “The way we are using nitrogen is extremely inefficient. Around 80 per cent of [our] nitrogen resources are lost to the environment.

“Ammonia nitrate is the major source of fertiliser for farms in the country, but that is big pellets of 2-3mm in size.

“These large pellets are much less liable to volatilising (becoming volatile) and creating ammonia. Around the world lots of farmers are using urea fertiliser (from animal waste).

“What’s happened with financial cuts and prices being difficult, is that urea is cheaper than ammonium nitrate, so a lot of farmers have started increasingly using urea instead of using ammonium nitrate because it’s cheaper, although it’s lost more to the air.”

Prof Sutton said a key solution was for farmers to switch from using urea to using ammonium nitrate.

Another method would be for those farmers using urea as fertiliser to also spread particular inhibitors, which reduce ammonia emissions, and would “allow the fertiliser to last longer in the soil, giving the crops a better chance to take up those nutrients”.

Sutton said in Germany, using such inhibitors was already legally required, but such legislation has not yet been introduced in the UK.

According to the research published in Science, cutting ammonia emissions would cost just 10 per cent of what it would take to eliminate an equivalent amount of nitrogen oxide.

“Thus, reducing NH3 (ammonia) emissions would be a more cost-effective way to limit PM2.5 and mitigate its harmful health impacts rather than solely focusing on reducing NOx (nitrogen oxide),” the report concludes.

Jan Erisman, a professor of environmental sustainability at Leiden University said the research shows “the global burden of disease associated with nitrogen air pollution exposure is estimated to cause millions of deaths and lost years of healthy life annually and, together with economic setbacks, will cost far more to fix tomorrow than it would if action is taken today”.