Atmospheric Aerosol: Does a Background Level Exist?

Measurements of light-scattering made with an integrating nephelometer at Point Barrow, Alaska, and Mount Olympus, Washington, are in agreement in magnitude, and both sets of measurements also are in agreement with other measurements of light-scattering and turbidity made in remote locations. This agreement suggests that a background level of aerosol exists and that the concept of a background is applicable.