Exposure continued level

Most chemical agents are essentially cumulative in their effects. The reason is that the human body detoxifies them very slowly or not at all. For example, a 1-h exposure to HD or CG followed within a few hours by another 1-h exposure has about the same effect as a single 2-h exposure. Continued exposure to low concentrations of HD may cause sensitivity to very low concentrations of HD. Other chemical agents also have cumulative effects. For example, an initial exposure to a small (less than lethal) amount of Sarin (GB) would decrease cholinesterase levels a second quantity less than the FDS0... 

NRC (National Research Council). 1985a. Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants, Vol. 4. Washington, DC National Academy Press. 

TABLE 23-17 Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants... 

Continuous ethyl acetate process, 10 483 Continuous Exposure Guidance Levels (CEGL), 21 837 Continuous extractors, 10 751 Continuous falling film SO3 sulfonation process, 23 544, 550-552 Continuous fiber composites, fabrication of, 26 766, 767... 

NRC (National Research Council). 1987. Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants, Vol. 7. Washington, DC National Academy Press. NRC (National Research Council). 1988. Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants, Vol. 8. Washington, DC National Academy Press. 

There is also a well-established record that should be highlighted the ubiquitous presence and levels of PFOS and PFOA in human milk and blood. However, transplacental studies to elucidate the process involving and the risks associated with early life exposure continue being required. 

In another pattern of sensitization response, a worker who has had only minimal upper respiratory symptoms or no apparent effects from several weeks of low-level exposure may suddenly develop an acute asthmatic reaction to the same or a slightly higher level. The asthmatic reaction may be severe, sometimes resulting in status asthmaticus, which may be fatal if exposure continues. ... 

In severe cases of exposure to toxicants, a population may go to zero and stay there so long as exposure continues or, if the toxicant is removed, until immigration from outside the ecosystem restores the population. In other cases, the population is reduced and remains at a lower level so long as exposure to the toxicant continues. Another possibility is for a population to decline, and then rise again as the population develops resistance to the effects of the toxic substance. This effect has been observed in the case of exposure to insecticides of insects whose short reproductive times enable natural selection to build populations resistant to the insecticides. 

NRC. 1986. Emergency and continuous exposure guidance levels for selected airborne contaminants. Vol 6. Washington, DC National Research Council, National Academy Press, 7-33... 

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