Environmental Engineering Reference
In-Depth Information
O
O
O
O
2
2
2
O
3
3
O
1,2-Dioxane
o -Dioxane
1,3-Dioxane
m -Dioxane
1,4-Dioxane
p -Dioxane
FIGURE 7.39
Structure of dioxane isomers.
7.9 Summary and Conclusion
There are thousands of contaminants existing everywhere, and many of the more unsa-
vory ones are concentrated within urban areas. They are in the air we breathe, the water
we drink, the food we eat, and in the dirt we play in. They are organic and inorganic. Many
naturally occur—many do not. Some we know about and some we do not. Some are more
toxic than others. Some may cause cancer and some may not. All of them have the ability
to cause some adverse health effect in humans, to other organisms, or negatively impair
or impact the environment if the exposure and dose are just right. Otherwise, they would
not be considered contaminants.
This now leads us to the next set of questions we will explore. How do contaminants
behave once they are released into the environment? Do they degrade? Where would we
go to find them? How long do they last?
Evaluating the behavior of contaminants in the environment is commonly referred to
as fate and transport assessment. Analysis of the fate and transport of contaminants once
released into the environment is crucial for accurately assessing the risk posed by a spe-
cific compound. Just because a contaminant exists does not mean there will be a risk to
human health or the environment. There must be a completed pathway—the contaminant
must be transported from its point of release to a place where exposure can occur. Chapter
8 discusses this central concept, and describes the fate and transport of many contami-
nants introduced in this chapter.
References
American Chemical Society. 2009. CAS Registry Numbers. http://www.cas.org/expertise/
cascontent/registry/regsys/html (accessed October 20, 2009).
American Conference of Governmental Industrial Hygienists (ACGIH). 2009. Guide to Occupational
Exposure Values . ACGIH, Cincinnati, OH.
Agency for Toxic Substances and Disease Registry (ATSDR). 1989. Bromodichloromethane . CAS
Registry Number 75-27-4. ATSDR ToxFAQs. Atlanta, GA.
Agency for Toxic Substances and Disease Registry (ATSDR). 1995a. 2-Hexanone . CAS Registry
Number 591-78-6. ATSDR ToxFAQs. Atlanta, GA.
Agency for Toxic Substances and Disease Registry (ATSDR). 1995b. Chlordane . CAS Registry Number
57-74-9. ATSDR ToxFAQs. Atlanta, GA.
Agency for Toxic Substances and Disease Registry (ATSDR). 1996. Polycyclic Aromatic Hydrocarbons .
General Contaminant Class. ATSDR ToxFAQs. Atlanta, GA.
 
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