Acute exposure means exposure of up to 14 days, while chronic exposure is for much longer periods, including years. Acute exposure to benzene will affect a person's central nervous system and cause respiratory depression. Chronic exposure , such as with a worker exposed to low levels over a longer period of time, will destroy a person's liver. One of the greatest dangers of chronic exposure to many chemicals is the possibility of cancer. A third feature to keep in mind is how toxic chemicals enter the body.
Some routes are more dangerous than others.
The safest way, surprisingly, to have toxic chemicals enter a person is orally, particularly on food products or with drinking water. Only part of the chemical gets into the bloodstream, usually about 50 percent, and the rest is excreted. Entry by inhalation is the most dangerous route. When a person breathes in a toxic chemical, as did the people in Bhopal, it goes to the lungs and straight into the bloodstream in almost a 100 percent concentration. Chemicals entering the body through the skin either by absorption through the air or by direct skin contact are almost as dangerous as through the lung because they make their way quickly into the bloodstream.