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.
Breathing even a little tobacco smoke can be harmful (1-4). Of the more than 7,000 chemicals in tobacco smoke, at least 250 are known to be harmful, including hydrogen cyanide, carbon monoxide, and ammonia (1, 2, 5). Among the 250 known harmful chemicals in tobacco smoke, at least 69 can cause cancer.