Farming emissions of ammonia are a leading cause of air pollution health damage and premature deaths in Europe and eastern United States.
Every year 3.3 million people die prematurely from the effects of outdoor air pollution worldwide – a figure that could double by 2050 unless clean-up measures are taken. This is shown in a study carried out by a team of researchers at the Max Planck Institute for Chemistry in Mainz, Germany, recently published in the journal Nature.
The study focuses on the most critical outdoor air pollutants, namely fine particulate matter (PM2.5) and ozone. It is estimated that nearly three-quarters of the deaths are due to strokes and heart attacks, and one quarter to respiratory diseases and lung cancer.
This is the first study to single out different outdoor air pollution source-sectors and estimate the number of premature deaths they each cause, considering seven source categories: residential and commercial energy use; agriculture; power generation; land transport (i.e. excluding shipping and aviation); industry; biomass burning; and natural sources.
A surprising discovery, according to the authors, is that the two largest sources of health damage from air pollution are not industry and transport, but small domestic fires and agriculture.
Residential and commercial energy use is the largest source category worldwide, contributing nearly one-third of the premature deaths, and with particularly high shares in countries such as India and Indonesia. This category includes diesel generators, small stoves and smoky open wood fires, which many people in Asia use for heating and cooking. (Note that this study’s estimate of 1.0 million deaths per year from this sector is in addition to the 3.54 million deaths per year due to indoor air pollution from essentially the same source.)
By contrast, a leading cause of air pollution in Europe, Russia, Turkey, Japan and the eastern United States is agriculture. Ammonia is emitted into the atmosphere as a result of intensive livestock farming and use of fertilizers. It then reacts with other air pollutants, namely sulphur dioxide and nitrogen oxides, to form ammonium sulphate and ammonium nitrate, which are tiny airborne particles.
Globally, agriculture is the cause of one-fifth of all deaths due to air pollution. In many European countries, its contribution is 40 per cent or higher. Since the abundance of ammonia is often a limiting factor in PM2.5 formation, a reduction in its emissions can make an important contribution to air quality improvements.
The finding that agriculture is the second-largest contributor to global mortality from PM2.5 is highly valuable, said environmental health expert Professor Michael Jerrett, at the University of California, because agriculture has generally not been seen as a major source of air pollution or premature death, and because it suggests that much more attention needs to be paid to agricultural sources, by both scientists and policymakers.
Other major sources are coal-fired power plants, industry, biomass combustion and motor vehicles. Taken together, they account for another third of premature deaths. Just under a fifth of premature deaths are attributed to natural dust sources, particularly desert dust in North Africa and the Middle East.
The authors conclude that: “Our results suggest that if the projected increase in mortality attributable to air pollution is to be avoided, intensive air quality control measures will be needed, particularly in South and East Asia.”
Christer Ågren
Source: Max Planck Institute press release 16 September, 2015
The article: “The contribution of outdoor air pollution sources to premature mortality on a global scale.” By J. Lelieveld, J. S. Evans, D. Giannadaki, M. Fnais and A. Pozzer. Published in Nature, 17 September 2015; doi: 10.1038/nature15371
