Editing Nitrogen cycle (section)

=== Impacts on human health: air quality ===
Human activities have also dramatically altered the global nitrogen cycle by producing nitrogenous gases associated with global atmospheric nitrogen pollution. There are multiple sources of atmospheric [[reactive nitrogen]] (Nr) fluxes. Agricultural sources of reactive nitrogen can produce atmospheric emission of [[ammonia]] ({{chem2|NH3}}), [[nitrogen oxide]]s ({{chem|NO|x}}) and [[nitrous oxide]] ({{chem|N|2|O}}). Combustion processes in energy production, transportation, and industry can also form new reactive nitrogen via the emission of {{chem|NO|x}}, an unintentional waste product. When those reactive nitrogens are released into the lower atmosphere, they can induce the formation of smog, [[particulate matter]], and aerosols, all of which are major contributors to adverse health effects on human health from air pollution.<ref name="Kampa 2008" /> In the atmosphere, {{chem|NO|2}} can be [[Redox|oxidized]] to [[nitric acid]] ({{chem|HNO|3}}), and it can further react with {{chem|NH|3}} to form [[ammonium nitrate]] ({{Chem2|NH4NO3}}), which facilitates the formation of particulate nitrate. Moreover, {{chem|NH|3}} can react with other acid gases ([[Sulfuric acid|sulfuric]] and [[hydrochloric acid]]s) to form ammonium-containing particles, which are the precursors for the secondary [[Organic compound|organic]] [[aerosol]] particles in [[Smog|photochemical smog]].<ref name="Erisman 2013" />