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.
The EPA lists Radon risk exposure to 4.0 pCi/L for a lifetime (18 hours per day) to cause 7 additional lung cancers in a thousand non-smokers or 62 additional lung cancers in 1000 smokers. The risk is considered linear which means even 2 pCi/L for a lifetime would cause 3 additional cancers in a 1000 non-smokers.