Navigation at Sea, History of. The first Western civilization known to have developed the art of navigation at sea were the Phoenicians, about 4,000 years ago (c. 2000 B.C.E. ). Phoenician sailors accomplished navigation by using primitive charts and observations of the Sun and stars to determine directions.
Air pollution risk is a function of the hazard of the pollutant and the exposure to that pollutant. Air pollution exposure can be expressed for an individual, for certain groups (e.g. neighborhoods or children living in a county), or for entire populations.ther examples include carbon monoxide gas from motor vehicle exhaust, or the sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact.
Particulate matter under 2.5 micrometers in diameter, also known as PM2.5 or fine particles, are generally accepted to be the most severe type of air pollution, since Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs [1].