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.
Radon is a radioactive gas that causes cancer. Approximately 21,000 people die each year from radon exposure. Radon is found in water, earth, and the air we breathe in our homes, schools, and workplaces.