This chapter discusses the uses, physical and chemical properties, environmental fate and bioaccumulation, eco and mammalian toxicology, sources of exposure, industrial hygiene, health effects and its diagnosis, and biological markers and silo fillers' disease (SFD) of nitrogen compounds. Reactive nitrogen includes all forms of nitrogen that are biologically, photochemically, and radioactively active. Compounds of nitrogen that are reactive include the following: nitrous oxide (N2O), nitrate (NO3), nitrite (NO2). Nitrogen oxide is a key component of the formation of ground level ozone or smog. Molecular nitrogen is modified via discharge of lightening. The initial symptoms of exposure to nitrogen oxides include cough, burning of the throat and chest, nausea, fatigue, and shortness of breath. Nitrogen oxides are skin irritants and corrosives. Nitrogen oxide exposure to the skin and eyes causes inflammation and irritation. Nitrogen oxides have been evaluated as potential biological markers.