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UNITED
NATIONS
SC
UNEP/POPS/POPRC.11/INF/15
Distr.: General
9 October 2015
Stockholm Convention
on Persistent Organic
Pollutants
English only
Persistent Organic Pollutants Review Committee
Eleventh meeting
Rome, 1923 October 2015
Item 5 (b) (i) of the provisional agenda*
Technical work: consideration of draft risk profiles:
dicofol
Additional information on dicofol
Note by the Secretariat
The annex to the present note sets out additional information on dicofol submitted to the
Secretariat by Mr. Marcus Richards (Saint Vincent and the Grenadines), the Chair of the intersessional
working group on dicofol, on 8 October 2015. The present note, including its annex, has not been
formally edited.
*
UNEP/POPS/POPRC.11/1.
121015
UNEP/POPS/POPRC.11/INF/15
Annex
Additional information on dicofol
Table 1: Endocrine related effects of dicofol
Species /
Formulation
Results
Study type/
/Dose
In vivo
Alligators, field
study
Pesticide mixture,
composed primarily
of dicofol
Alligators, field
study
Accidental spill of
pesticides
Rat, In vivo
30, 40 and 50 mg/kg
body weight,
administered orally to
normal virgin rats for
30 days
Dog, in vivo
2.5 mg/kg
Mouse, in vivo,
uterine weight
20% commercial
dicofol
Daphnia magna,
sex ratio
Rotifier test
Fish
EstradiolUDPGT activity
in carp liver
microsomes
1 mM dicofol
Synthesis of sex
hormones in
fish microsomes
Females: 17ß-estradiol plasma
levels were >2 times higher than
in the control lake, abnormal
ovarian morphology. Males: <3x
testosterone levels than in control
males, poorly organized testes
and abnormally small phalli
Decreased egg availability and
juvenile recruitment, altered
gonadal morphology and serum
hormone concentrations
Significant decrease in healthy
follicles with concomitant
increase in atretic follicles at
higher doses; dose-dependent
effect, significant decrease in
number of estrous cycles,
duration of proestrus and diestrus,
and increase in the duration of the
estrus phase.
Inhibition of adrenocorticotrophic
hormone (ACTH)-stimulated
cortisol release in dogs
Significantly elevated uterine
weight on immature mice
Comments
Reference
Mixture effects
have to be taken
into account
Guillette et al.,
1994
Effects couldn’t be
contributed to
dicofol alone, rather
to a mixture of
pesticides, e.g. DDT
among others
Concentration levels
lead to significant
toxic effects in
multiple organs in a
number of studies.
Finger & Gogal,
2013
Jadarmkunti &
Kaliwal, 1999
US EPA, 1998;
WHO 1996
Article in Chinese
Zhao et al., 2000
(IPEN, 2015)
1 mM dicofol significantly
inhibited testosterone
glucuronidation by 81% (IC50
value = 293±11 µM) with no
significant effect on estradiolUDPGT
Dicofol could interfere with the
synthesis of sex hormones in fish
microsomes
Lavado et al., 2004
Dicofol gave rise to a statistically
significant inhibition of aromatase
activity
Vingaard, 2000
Significant promotion of human
breast cancer MCF-7 cell
proliferation
Du & Xu, 2001
Induction of estrogen receptor
alpha and beta transcriptional
activity and inhibition of
androgen receptor transcriptional
activity.
Dicofol showed the ability to bind
to both androgen receptors and
Kojima et al., 2004
Thibaut & Porte,
2004
Human cell lines and tissues
Aromatase
50 mM.
activity in
human placental
microsomes
Human breast
20% commercial
cancer MCF-7
dicofol formulation
cell proliferation 4x10-11 and 4x10-6
in vitro
g/mL
Estrogen and androgen receptor
In vitro, Chinese
hamster ovary
cells, estrogen
receptor activity
Estrogen
receptor2
Dicofol also showed
estrogenic activity
Okubo et al., 2004
UNEP/POPS/POPRC.11/INF/15
Species /
Study type/
Formulation
/Dose
Results
Comments
dependent
MCF-7 cell
proliferation
assay
Reporter assay
in yeast cells
transfected with
human ovarian
estrogen
receptor alpha
Yeast-based
steroid hormone
receptor gene
transcription
assay designed
with the human
estrogen
receptor (hER).
Estrogen and
androgen
receptor in vitro
reporter gene
binding in
Chinese hamster
ovary cells
In vitro utilizing
transiently
transfected
African green
monkey kidney
(COS-7) cells
estrogen receptors in an MCF-7
cell proliferation assay.
in MCF-7 cell
culture, causing
proliferation of the
cells.
indication that
dicofol can bind to
ER alpha in vitro
Estrogen
receptor
competitive
binding assay
for use in multispecies
comparisons
Competition
binding assay if
alligator
oestrogen and
progesterone
receptors
p,p’-dicofol displaced up to 83%
of 17 ß-estradiol from alligator
ERa and was an equivocal binder
to human ERa, displacing a
maximum of 58% 17 ß-estradiol.
Dicofol stimulated a positive
estrogenic response, indicating
that dicofol can bind to ER alpha
in vitro
Dicofol acts as a weak hER
agonist due to the activity of the
p,p’-isomer and the (-)-o,p’enantiomer
Estrogenic activity of dicofol
The dicofol metabolite, p,p’dichlorobenzophenone showed
potent antiandrogenic properties
At concentrations
measured in alligator
eggs from Lake
Apopka, USA
45.6 μM (inhibitor
concentration for
50%)
Transactivation
system utilising
transiently
transfected
African green
monkey kidney
(COS-7)
Thyroid hormone interference
Rana
IC50 of 2.2 μM
catesbeiana
tadpole red
Reference
Vinggaard et al,
1999
Estrogenic activity
of (+)-17-bestradiol
(positive control)
and dicofol
enantiomers was
measured via
quantification of bgalactosidase
Screening of 200
pesticides by in
vitro reporter gene
assays
Hoekstra et al.
2006
This finding was
confirmed by
further studies in
T47D human
mammary
carcinoma cells by
measuring mRNA
and protein
expression of
androgen dependent
genes i.e. TRMP-2
(testosteronerepressed prostate
message-2) mRNA
and PSA (prostatespecific antigen)
protein
using baculovirus
expressed fulllength recombinant
oestrogen receptors
in a 96-well plate
competitive binding
assay
Thiel et al. 2011
Kojima et al., 2004
Rider et al. 2010
Dicofol was able to compete for
binding to tritiated 17β-estradiol
of alligator oestrogen receptors;
and reduced binding to alligator
progesterone receptors by 40%.
Vonier et al., 1996
Degradation of dicofol to p,p’dichlorobenzophenone (DCBP)
under alkaline conditions as well
as induced by UV-light, and
potent antiandrogenic properties
of DCBP in vitro
Thiel et al., 2011
Dicofol was a powerful inhibitor
of the 3,5,3’-triiodothyronine
(T3)-uptake system on the plasma
Shimada &
Yamauchi 2004
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UNEP/POPS/POPRC.11/INF/15
Species /
Study type/
blood cells,
triiodothyronine
T3 -uptake
system on the
plasma
membrane
T3 binding to
transthyretin
and thyroid
hormone
receptor in
chicken and
bullfrog
Competitive
binding assay
Formulation
/Dose
Results
Comments
Reference
membrane inhibiting more than
80% of the saturable initial
uptake. Dicofol significantly
depressed the T3 response.
10-10-10-7 M
Thyroid
Induction at 0.8 and
hormone (TH)
10 µM.
inducible
primary
screening assay
with a Xenopus
laevis cell line
Computer based modelling
molecular
dynamic
simulations
Dicofol exhibited a biphasic,
nonmonotonic effect on thyroid
hormone binding totransthyretins.
Up to 170%, 0 transthyretins.
However, at 4x10-5 M it inhibited
T3 binding by 83%.
Dicofol exhibited relatively
strong interference with the T4
binding site of transthyretin,
Dicofol (dicofol) had 3,3‘,5-Ltriiodothyronine- T3- antagonist
activity
Binding affinity of dicofol to
human estrogen receptor ERalpha, using
Ishihara et al., 2003
Indicating the
potential to lower
plasma thyroid
hormone levels
through interference
with hormone
transport carriers
Self-inactivating
(SIN) lentivirus
vector (LV)
containing a
luciferase gene.
van den Berg et al.,
1991
Sugiyama et al.,
2005
Zhuang et al., 2012
References
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Toxicology 67(6):0795–99.
Finger JW, Gogal RM (2013): Endocrine-disrupting chemical exposure and the American alligator: a review of the
potential role of environmental estrogens on the immune system of a top trophic carnivore. Archives of
Environmental Contamination and Toxicology 65(4):704-714.
Guillette, LJ, Gross TS, Masson GR, Matter JM, Percival HF, Woodward AR (1994): "Developmental Abnormalities
of the Reproductive System of Alligators (Alligator mississippiensis) from Contaminated and Control Lakes in
Florida." Env. Health Perspectives, 102 (8): 680-688.
Hoekstra PF, Burnison BK, Garrison AW, Neheli T, Muir DCG. (2006): Estrogenic activity of dicofol with the human
estrogen receptor: Isomer- and enantiomer-specific implications. Chemosphere 64, 174-177
Ishihara A, Sawatsubashi S, Yamauchi K. (2003): Endocrine disrupting chemicals: interference of thyroid hormone
binding to transthyretins and to thyroid hormone receptors. Molecular and Cellular Endocrinology 199(1-2):105-17.
Jadaramkunti UC, Kaliwal BB (2002): Dicofol formulation induced toxicity on testes and accessory reproductive
organs in albino rats. Bulletin of Environmental Contamination and Toxicology 69(5):741-8.
Kojima H, Katsura E, Takeuchi S, Niiyama K, Kobayashi K (2004): Screening for estrogen and androgen receptor
activities in 200 pesticides by in vitro reporter gene assays using Chinese hamster ovary cells. Environmental Health
Perspectives 112:524-531.
Lavado R, Thibaut R, Raldu´a D, Martı´n R, Porte C (2004): First evidence of endocrine disruption in feral carp from
the Ebro River. Toxicology and Applied Pharmacology 196, 247– 257.
Okubo T, Yokoyama Y, Kano K, Soya Y, Kano I. (2004): Estimation of estrogenic and antiestrogenic activities of
selected pesticides by MCF-7 cell proliferation assay. Archives of Environmental Contamination and Toxicology
46(4):445-453.
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UNEP/POPS/POPRC.11/INF/15
Rider CV, Hartig PC, Cardon MC, Lambright CR, Bobseine KL, Guillette Jr LJ, Gray Jr LE, Wilson VS (2010):
Differences in Sensitivity but not Selectivity of Xenoestrogen Binding to Alligator Versus Human Estrogen Receptor
Alpha. Environmental Toxicology and Chemistry 29:9, 2064-2071
Shimada N, Yamauchi K (2004): Characteristics of 3,5,3’-triiodothyronine (T3)-uptake system of tadpole red blood
cells: effect of endocrine-disrupting chemicals on cellular T3 response. Journal of Endocrinology 183:627–637.
Sugiyama, S., Shimada, N., Miyoshi, H., Yamauchi, K. (2005): Detection of Thyroid System-Disrupting Chemicals
Using in Vitro and in Vivo Screening Assays in Xenopus laevis. Toxicological Sciences 88:2, 367-374.
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US EPA (1998) RED: Reregistration Eligibility Decision Dicofol
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Vonier PM, Crain DA, McLachlan JA, Guillette LJ, Arnold SF (1996): Interaction of environmental chemicals with
the estrogen and progesterone receptors from the oviduct of the American alligator. Environmental Health
Perspectives 104(12):1318–1322.
WHO (1996): International Programme on Chemical Safety, Dicofol, WHO/FAO Data Sheets on Pesticides No. 81
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