Environmental Engineering Reference
In-Depth Information
Currently, there is inadequate information to establish
whether PCBs are a human carcinogen (USEPA 2009b), but
the World Health Organization (2003) suspects they are
(Group: A2). Notwithstanding cancer, they pose significant
other dangers to human health. PCBs have been shown to
cause cancer in laboratory animals, and have also been
shown to cause a number of serious noncancer health effects
in animals, including the immune system, reproductive sys-
tem, nervous system, endocrine system, and others (USEPA
2009e).
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
FIGURE 7.8
Basic PCB structure.
7.6 Semivolatile Organic Compounds
SVOCs are a group of organic-based compounds much less volatile than VOCs. A variety
of SVOCs are used in clothing and building materials to provide flexibility, water resis-
tance, or stain repellence, and to inhibit ignition or as flame retardants (ATSDR 2002a).
Common groups of organic compounds associated with SVOCs are phthalates, phenols,
amines, and esters.
7.6.1 Phthalates
The name phthalates is derived from phthalic acid—itself derived from naphthalene
and previously discussed earlier in this chapter. Phthalates exhibit low water solubility,
high oil solubility, and low volatility (Fetzer 2000). There are approximately 25 distinctive
phthalate compounds, including the common ones shown in the following:
• Diethyl phthalate (DEP)
• Di-
n
-butyl phthalate (DBP)
• Bi or Bis(2-ethylhexyl) phthalate (DEHP)
The structural formula and CAS registration number are each of the three common phthal-
ate compounds are listed in Table 7.8 (USEPA 2009b).
Figure 7.9 depicts the general structure of a phthalate molecule, and Figure 7.10 shows
the structure of Di(2-exthylhexyl) phthalate (USEPA 2009b).
TABLE 7.8
Structural Formula and CAS Registration Numbers for Three Common Phthalates
Name
CAS Registration Number
Chemical Formula
Diethyl phthalate (DEP)
84-66-2
C
6
H
4
(COOC
2
H
5
)
2
Di-
n
-butyl phthalate (DBP)
84-74-2
C
6
H
4
[COO(CH
2
)
3
CH
3
]
2
Di or Bis(2-ethylhexyl) phthalate (DEHP)
117-81-7
C
6
H
4
[COOCH
2
CH(C
2
H
5
)(CH
2
)
3
CH
3
]
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.
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