Editing Acid rain (section)

==== Nitrogen Dioxide Effects ====
Exposure to air pollutants associated with acid rain, such as [[nitrogen dioxide]] (NO<sub>2</sub>), may have a negative impact on respiratory health.<ref name=":10" /> Water-soluble nitrogen dioxide accumulates in the tiny airways, where it is transformed into [[Nitric acid|nitric]] and [[nitrous acid]]s.<ref name=":11" /> [[Pneumonia]] caused by [[nitric acid]]s directly damages the epithelial cells lining the airways, resulting in [[pulmonary edema]].<ref name=":13" /> Exposure to nitrogen dioxide also reduces the immune response by inhibiting the generation of inflammatory [[cytokine]]s by [[alveolar macrophage]]s in response to bacterial infection.<ref name=":14" /> In animal studies, the pollutant further reduces respiratory immunity by decreasing [[mucociliary clearance]] in the lower respiratory tract, which results in a reduced ability to remove respiratory infections.<ref name=":15" />