The major impact of it entering the environmental ecosystem is that it catalyzes the breakdown of ozone. NOx reacts with other substances and therefore plays a role in forming smog, acid rain, ground-level ozone, and increased levels of fine particles (PM), which are associated with deforestation, surface water acidification, reduced crop yield, and adverse health effects. Health effects are mostly related to the human respiratory system causing inflammation of the airway, respiratory diseases, and increased sensitization to allergens.