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.
Radon for Children. Harmful Effects of Radon. Radon is the second leading cause of lung cancer (diagram to the right) and a serious public health concern. The primary adverse health effect associated with chronic exposure to radon is lung cancer (typically bronchogenic): -squamous cell carcinoma. -small cell carcinoma.
1 Radon causes about 21,000 lung cancer deaths each year in the U.S. 2  Radon is produced from the natural breakdown of uranium in soil, rock and water. 3  Radon is found all over the U.S. It can be detected in any type of building-homes, offices, and schools. 4  It is impossible to smell or taste radon.