How ammonia feeds and pollutes the world

Ammonia, with the chemical formula NH3, is a common ingredient in many industrial and agricultural applications and plays a pivotal role in producing the fertilizers needed to produce enough food for 7.9 billion people. However, the agricultural use of ammonia also negatively affects the environment, resulting in the loss of biodiversity and the pollution of water, air, and soil (1). Ammonia contributes to the formation of nitrous oxide, a powerful greenhouse gas, worsening the problem in most scenarios but also curbing it somewhat through cooling by aiding the formation of particulate matter and clouds (2). On page 758 of this issue, Gu et al. (3) show that the economic cost associated with the loss of human life—owing to ammonia’s contribution to air pollution alone—far outweighs the economic cost to curb ammonia emission.