A recent study in Science, to which JRC contributed, highlights the role of man-made emitted nitrogen oxides and ammonia into the atmosphere on global level, and states that relatively cheap interventions in agricultural practices can lead to substantial health and welfare benefits.
Air quality and health
Fine particulate matter (PM2.5, airborne particles with a diameter smaller than 2.5 micrometer) in the atmosphere causes severe negative impacts on human health. Globally, PM2.5 exposure is associated with near 4 million premature deaths annually, corresponding to over 100 million healthy life years lost.
PM2.5 is a mixture of several substances from different sources, including crustal and carbonaceous material, as well as products of emitted sulphur dioxide, nitrogen oxides and ammonia. The latter, after undergoing chemical reactions in the atmosphere, form ammonium sulfate and ammonium nitrate in PM2.5 which we call nitrogen-derived PM2.5. Man-made nitrogen oxide emissions are generally driven by fossil fuel combustion in power plants and transport, while ammonia is mostly emitted by the agricultural sector.
Nitrogen share in PM2.5 health impacts
The present study finds that globally, the nitrogen share in PM2.5 has increased from 30% in 1990 to 39% in 2013 and the total number of life years lost, due to nitrogen-derived PM2.5 pollution, increased from 19.5 to 23.3 million. In Asia, Europe and North America the share is around 45% in 2013. In most countries, the ammonia contribution to PM2.5 exceeds the share from nitrogen oxides.
Costs and benefits of nitrogen mitigation
By applying a country-specific welfare cost to each life year lost, the study estimates an average marginal cost of premature mortality of 4.8 USD per kg nitrogen emitted in 2013. On the other hand, the global average abatement costs are 1.5 USD per kg ammonia-nitrogen and 16 USD per kg NOx-nitrogen. Therefore, the social benefit of reduced mortality from ammonia abatement is substantially larger than the abatement cost, while the opposite is true for NOx. The highest benefit/cost ratio for ammonia abatement occurs in North America, followed by Europe and Asia.
The main opportunities for ammonia abatement concern agricultural practices, e.g. by optimising nitrogen fertilisation. In practice, many measures to control ammonia can have a zero-cost implementation or represent a net economic benefit for farmers. On the contrary, most cost-effective NOx emission reduction measures are already in place in high-income countries. Consequently, the abatement costs for NOx are larger than the benefit of reduced mortality. Considering the overall costs and benefits, the analysis highlights the priority for air pollution policies to give increased attention to controlling ammonia emissions, complementing past successful policies on nitrogen oxides and sulphur.
- Publication date
- 5 November 2021