Environmental Engineering Reference
In-Depth Information
Cl
Cl
Tetrachloroethene (PCE)
C
C
Cl
Cl
Cl
H
Trichloroethene (TCE)
C
C
Cl
Cl
H
Cl
H
Cl
H
H
Dichloroethene (DCE)
C
C
C
C
C
C
H
Cl
Cl
Cl
Cl
H
H
H
Vinyl chloride (VC)
C
C
Cl
H
FIGURE 7.4
Degradation sequence of PCE.
TABLE 7.3
Chemical Formula and Carcinogenicity for Each BTEX Compound
Compound
Carcinogenicity Rating
Chemical Formula
Tetrachloroethene (PCE)
Currently under review
C
2
Cl
4
Trichloroethene (TCE)
Currently under review
C
2
HCl
3
cis
-1,2-Dichloroethene (DCE)
Group: A4
C
2
H
2
Cl
2
trans
-1,2-Dichloroethene (DCE)
Group: A4
C
2
H
2
Cl
2
Vinyl chloride
Group: A1
C
2
H
3
Cl
1,1,1-Trichloroethane (TCA)
Inadequate information
C
2
H
3
Cl
3
or CH
3
CCl
3
1,1-Dichloroethene (DCE)
Group: A2
C
2
H
2
Cl
2
Methylene chloride
Inadequate information
CH
2
Cl
2
Carbon tetrachloride
Group: A2
CCl
4
Chloroform
Group: A2
CHCl
3
Chlorobenzene
Inadequate information
C
6
H
5
Cl
1,2-Dichlorobenzene
Inadequate information
C
6
H
4
Cl
2
Source:
United States Environmental Protection Agency, Integrated Risk
Information System (IRIS), http://www.epa.gov/ncea/iris/intro.htm
(accessed October 21, 2009), 2009b.
7.3.3 Trihalomethanes
THMs are a group of VOCs in which three of the four atoms of methane (CH
4
) are
replaced by halogen atoms. Many THMs are used as refrigerants, solvents, and are
also by-products produced during water purification and chlorination. During water
treatment, THMs can form as a by-product when chlorine and bromine are used to
Search WWH ::
Custom Search