But, over time, it has become clear that air pollution also contributes to land and water pollution which affects the health of the Chesapeake Bay's valuable living resources - its fish, shellfish, and other animals. Over the last thirty years, research has provided us with more knowledge on how air pollution can directly affect the Bay. Since the passing of the Clean Air Act and the Clean Water Act in the early 1970's, air pollution and water pollution were largely considered two separate problems. In recent years research has led to a better understanding of the link between these two environmental threats. Atmospheric deposition is one of the main contributors to the problems facing the Chesapeake Bay.
Deposition is when the air pollution hits the earth's surface.
Air pollution can be washed out of the sky by rain or snow, in a form called wet deposition or gravity acts on air pollution, depositing pollution without the benefit of rain, as dry deposition, such as dust or gases. Airborne pollutants that deposit on the land can be transported into waterbodies by runoff or through groundwater flow. The Chesapeake Bay Program is at the leading edge of addressing the role of air pollutants, particularly, in affecting land and water quality. Computer models estimate that the primary nitrogen oxide emission's airshed is approximately 418,000 square miles, this six and half times larger than the Chesapeake Bay watershed. This airshed shows that not only are nitrogen oxide emissions deposited to the Bay and its watershed from local sources BUT also from sources in places far away, such as Kentucky, Indiana, and Canada.