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.
1 Radon is a naturally occurring radioactive gas which may be found in indoor environments such as homes and workplaces. 2  Radon is the most important cause of lung cancer after smoking. 3  Radon is estimated to cause between 3 and 14% of all lung cancers, depending on the average radon level in the country.