Environmental Engineering Reference
In-Depth Information
TABLE 7.1 (continued)
Common Uses of VOCs
Compound (Listed
Alphabetically)
CAS Registry
Number
Common Uses
Vinyl acetate
108-05-4
Solvent, caffeine extraction, dry cleaning, paint and
ink, rubber
Vinyl chloride
75-01-4
Polymer
Xylenes
i
1330-20-7
Rubber, paper, and glass industries, PVC
manufacturing
Gasoline component, paint thinner ingredient,
plasticizer
Source:
United States Geological Survey (USGS),
Volatile Organic Compounds in the Nation's Ground Water
and Drinking-Water Supply Wells
, USGS Circular 1292, Reston, VA, 2006; United States Environmental
Protection Agency,
Latest Findings on National Air Quality: Status and Trends Through 2006
,
EPA454/R-07-007, Research Triangle Park, NC, 2008c.
a
Levy (2009).
b
Lide (2008).
c
ATSDR (2007a).
d
Holleman and Wiberg (2001).
e
Doherty (2000).
f
ATSDR (1995a).
g
ATSDR (2005a).
h
ATSDR (2001).
i
ATSDR (2007b).
BTEX compounds are aromatic hydrocarbons with a
benzene ring
forming the backbone of its molecular struc-
ture (Jensen 2009). As depicted within the compound ben-
zene shown in Figure 7.2, the benzene ring consists of a
hexagonal arrangement of six carbon atoms located at the
vertices. Each atom is bonded to its adjacent atoms by a
single covalent bond and by an unusual ring bond of elec-
trons shared by all six carbon atoms. The chemical formu-
las and carcinogenicity for the BTEX compounds are listed
in Table 7.2.
C
6
H
6
Benzene
H
C
H
H
C
C
C
C
H
C
H
H
FIGURE 7.2
Benzene and the benzene ring.
TABLE 7.2
Chemical Formulas and Carcinogenicity for Each BTEX Compound
Compound
Carcinogenicity Rating
Chemical Formulas
Benzene Group: A1 C
6
H
6
Toluene Group: A4 C
7
H
8
or C
6
H
5
CH
3
Ethyl Benzene Group: A1 C
8
H
10
Xylenes
a
Data not adequate to currently evaluate C
8
H
10
, C
6
H
4
(CH
3
)
2
, or C
6
H
4
C
2
H
6
MTBE Data not adequate to currently evaluate C
5
H
12
O
Source:
United States Environmental Protection Agency, Integrated Risk Information System
(IRIS), http://www.epa.gov/ncea/iris/intro.htm (accessed October 21, 2009),
2009b.
a
Three isomers exist that include
o
-,
m
-, and
p
-xylene.
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