Maps, compasses, astrolabes, and calipers are among the early tools used by ocean navigators. In the modern era, these tools have been largely replaced by electronic and technological equivalents. Despite these early beginnings, it would take many centuries before global navigation at sea became possible.
Harmful Effects of Radon. 1  Radon is the second leading cause of lung cancer (diagram to the right) and a serious public health concern. 2  The primary adverse health effect associated with chronic exposure to radon is lung cancer (typically bronchogenic): -squamous cell carcinoma.
Exposure to radon is the second leading cause of lung cancer in the United States, after smoking. Radon gas occurs naturally. It forms when uranium breaks down to radium, which in turn breaks down to form radon. As radon decays, it releases radioactive byproducts that are inhaled and can cause lung cancer.