Nitrogen dioxide(NO2) has absorption features in the ultraviolet, blue, and green regions of the optical spectrum. Values of total columnar NO2 range from 0.4¿10-3 to about 5¿10-3 cm NO2(STP) and yield optical depths from 0.008 to 0.087 at 390 nm, the wavelength of maximum absorption. The presence of NO2 absorption must be considered in precision multiwavelength atmospheric turbidity studies. Previous reported values of the Angstrom power law coefficient are probably too large because NO2 absorption was not accounted for.