Polychlorinated Biphenyls (PCBs) Brief Introduction - The ...

Polychlorinated Biphenyls (PCBs)
Brief Introduction
Larry W. Robertson, M.P.H., Ph.D.
University of Iowa College of Public Health
Occupational & Environmental Health
&
Iowa Superfund Basic Research Program
October 22, 2007

PCBs as Persistent Organic
Pollutants
Persistent Organic Pollutants (POPs) are defined
as
“chemical substances that persist in the
environment, bio-accumulate through the food
web, and pose a risk of causing adverse effects
to human health and the environment.”
(United Nations Environment Programme (ENEP)

Dirty Dozen Structures (1): Cyclodienes
http://www.chem.unep.ch/pops
Aldrin
Dieldrin
Endrin
Heptachlor
Chlordane
Toxaphene

Dirty Dozen Structures (2)
http://www.chem.unep.ch/pops
DDT Hexachlorobenzene Mirex
PCBs Dioxins Dibenzofurans

F 3 C
F 2
C
F 2
C
C
F 2
F 2
C
C
F 2
F 2
C
C
F 2
O
S
OH
Cl
Cl
Cl
Perfluorooctane sulfonic acid
O
Br
Br
O
Br
Br
Cl
Cl
2-(4-chlorobenzene)-1,1,1-trichloroethane
Br Br
Br
Br
Br
Br
Br
Br
Br
Br
Decabromodiphenylether
Br
2,2',4,4',5,5'-hexabromobiphenyl
Br
Cl
Cl
Cl
O
Cl
Cl
Cl
Cl
2,2',4,4',5,5'-hexachlorobiphenyl
Cl
Cl
O
2,3,7,8-tetrachlorodibenz-2-dioxine
2,3,7,8-tetrachlorodibenzo-p-dioxin
Cl

HALOGENATION CONFERS UPON ORGANIC
MOLECULES:
Stability against chemical and biological oxidation,
including diminished flammability.
Increased melting points, diminished volatility, diminished
water solubility.
Halogenated compounds may persist in the environment and,
due to their lipophilic nature, bioconcentrate, bioaccumulate
in fatty tissues.

Terminology
• Bioconcentration
– the increase in concentration of a contaminant within
the organism, compared to its concentration in its
environment
• Biomagnification
– the incremental increase in concentration of a
contaminant at each level of a food chain
• Bioaccumulation
– is the process by which organisms (including humans)
can take up contaminants more rapidly than their bodies
can eliminate them, thus the amount of a contaminant
accumulates over time
– http://water.usgs.gov/wid/FS_216-95/FS_216-95.html

Biphenyl
3
2
2' 3'
4
4'
5 6
6'
5'

PCBs Production
•PCBs were commercially produced in the
US from the 1920’s until the 1970’s.
•Worldwide, about 2 million tons, but that
number may increase.
•PCBs are considered food chain
contaminants – body burdens increase with
age.

PCB Batch Production
HCl
gas
2 3
HCl acid
Cl 2
H 2
O
4
water vapor
H 2
O
1
water vapor
(1) chlorinator (2) sublimate (3) absorber (4) tank for hydrochloric acid
Iza Korwel

Biphenyl
3
2
2' 3'
4
4'
5 6
6'
5'

Commercial PCB Mixtures
Aroclor
1242
Aroclor
1248
Aroclor
1254
Aroclor
1260
Clophen
A 30
Clophen
A 60
% of chlorine 40-42 48 52-54 60 40-42 60
average Cl per
molecule 3.4 4.1 5.1 6.3 3.1 6.2
average molecular
weight 261 288 327 372 261 372
monochlorobiphenyl 1 - - - - -
dichlorobiphenyl 13 1 - - 20 -
trichlorobiphenyl 45 21 1 - 52 -
tetrachlorobiphenyl 31 49 15 - 22 1
pentachlorobiphenyl 10 27 53 12 3 16
hexachlorobiphenyl - 2 26 42 1 51
heptachlorobiphenyl - - 4 38 - 28
octachlorobiphenyl - - - 7 - 4
nonachlorobiphenyl - - - 1 - -
decachlorobiphenyl - - - - - -
Modified from Silberhorn et al, 1990

PCBs in Transformers
http://www.tdh.state.tx.us/beh/asbestos/TSCA/pcbs

Toxic Effects – Skin
Dark ‘‘cola-colored’’ hyperpigmentation
characteristically seen in some Yusho
babies
Chloracne and brownish hyperpigmentation
who was exposed decades earlier to PCBs in
the Yusho rice oil incident.
(Kuratsune et al., 1996)
• Kuratsune M., Yoshimura H., Hori Y., Okumura M., and Matsuda Y.
(1996) Yusho —A human disaster caused by PCB and related
compounds (Fukuoka: Kyushu University Press) 361 pp.

PCBs in Two Groups:
Higher Chlorinated Biphenyls
Higher chlorinated biphenyls, traditionally stabile,
food chain PCBs, and receptor ligands, inducers
of drug-metabolism and promoters of
hepatocarcinogenesis.
PCBs are considered food chain contaminants –
body burdens increase with age.

Episodic or Airborne PCBs
Lower Chlorinated Biphenyls
PCBs may be divided into lower chlorinated
biphenyls –fewer chlorines, more susceptible to
environmental breakdown and biologic attack,
more volatile = substrates for metabolism.
(Episodic PCBs)

Physical Properties
Physical Chemical Properties
Octanol-Water Partition Coefficient, 25 o C
Vapor Pressure, 25 o C (Pa)
10 10
10 9
10 8
10 7
10 6
10 5
10 4
Octanol-Air Partition Coefficient, 20 o C Relative retention time, GC, DB-5
10 12
10 1
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 11
10 10
10 9
10 8
10 7
10 6
1 50 100 150 200
50 100 150 200
PCB Congener Number (IUPAC #)
Edited by Luthe, G., from Hornbuckle, K.; Carlson, D.; Swackhamer, D.; Baker, J.; Eisenreich, S. "Polychlorinated Biphenyls
in the Great Lakes", In The Handbook of Environmental Chemistry; Persistent Organic Pollutants in the Great Lakes. Hites, R. A.,
Ed.; Springer-Verlag: Heidelberg, 2006, pp 13-70 and from EST 18, 468 (1984).

PCB Congener Profile in Chicago Air
0.12
5 & 8
0.1
0.08
33 52
0.06
0.04
28
15 &17
18
31
44 95
84 & 92 110
101
0.02
0
1
5
9
13
17
21
25
29
33
37
41
45
49
53
57
61
65
69
73
77
81
85
89
93
97
101
105
109
113
117
121
Elution order of PCB congeners
Fraction of the SPCB

Levels of PCBs and PBDEs

Comparison between North
American and European PBDEs