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Parabens are used as preservatives in many thousands of cosmetic, food and pharmaceutical products to which the human population is exposed. Although recent reports of the oestrogenic properties of parabens have challenged current concepts of their toxicity in these consumer products, the question remains as to whether any of the parabens can accumulate intact in the body from the long-term, low-dose levels to which humans are exposed. Initial studies reported here show that parabens can be extracted from human breast tissue and detected by thin-layer chromatography. More detailed studies enabled identification and measurement of mean concentrations of individual parabens in samples of 20 human breast tumours by high-pressure liquid chromatography followed by tandem mass spectrometry. The mean concentration of parabens in these 20 human breast tumours was found to be 20.6 +/- 4.2 ng x g(-1) tissue. Comparison of individual parabens showed that methylparaben was present at the highest level (with a mean value of 12.8 +/- 2.2 ng x g(-1) tissue) and represents 62% of the total paraben recovered in the extractions. These studies demonstrate that parabens can be found intact in the human breast and this should open the way technically for more detailed information to be obtained on body burdens of parabens and in particular whether body burdens are different in cancer from those in normal tissues.
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PARABENS IN HUMAN BREAST TUMOURS 5
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
Concentrations of Parabens in Human Breast
Tumours
P. D. Darbre,1,* A. Aljarrah,2 W. R. Miller,2 N. G. Coldham,3 M. J. Sauer4 and G. S. Pope1
1Division of Cell and Molecular Biology, School of Animal and Microbial Sciences, University of Reading, Reading
RG6 6AJ, UK
2The Edinburgh Breast Unit Research Group, Paderewski Building, Western General Hospital, Edinburgh EH4 2XU,
UK
3Department of Bacterial Diseases, Veterinary Laboratories Agency, Weybridge, New Haw, Addlestone, Surrey KT15
3NB, UK
4Department of TSE Molecular Biology, Veterinary Laboratories Agency, Weybridge, New Haw, Addlestone, Surrey
KT15 3NB, UK
Key words: parabens; xenoestrogens; oestrogenic activity; HPLC–MS–MS; human breast cancer; preservatives; cosmetics.
Parabens are used as preservatives in many thousands of cosmetic, food and pharmaceutical products to which
the human population is exposed. Although recent reports of the oestrogenic properties of parabens have
challenged current concepts of their toxicity in these consumer products, the question remains as to whether
any of the parabens can accumulate intact in the body from the long-term, low-dose levels to which humans are
exposed. Initial studies reported here show that parabens can be extracted from human breast tissue and
detected by thin-layer chromatography. More detailed studies enabled identification and measurement of mean
concentrations of individual parabens in samples of 20 human breast tumours by high-pressure liquid chroma-
tography followed by tandem mass spectrometry. The mean concentration of parabens in these 20 human
breast tumours was found to be 20.6 ±±
±±
± 4.2 ng g
1 tissue. Comparison of individual parabens showed that
methylparaben was present at the highest level (with a mean value of 12.8 ±±
±±
± 2.2 ng g
1 tissue) and represents
62% of the total paraben recovered in the extractions. These studies demonstrate that parabens can be found
intact in the human breast and this should open the way technically for more detailed information to be
obtained on body burdens of parabens and in particular whether body burdens are different in cancer from
those in normal tissues. Copyright © 2004 John Wiley & Sons, Ltd.
JOURNAL OF APPLIED TOXICOLOGY
J. Appl. Toxicol. 24, 5– 13 (2004)
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jat.958
Received 23 June 2003
Revised 7 October 2003
Copyright © 2004 John Wiley & Sons, Ltd. Accepted 8 October 2003
* Correspondence to: Dr. P. D. Darbre, Division of Cell and Molecular
Biology, School of Animal and Microbial Sciences, University of Reading,
PO Box 228, Whiteknights, Reading RG6 6AJ, UK.
E-mail: p.d.darbre@reading.ac.uk
Contract/grant sponsor: Seedcorn Fund of the Veterinary Laboratories
Agency.
INTRODUCTION
The alkyl esters of p-hydroxybenzoic acid (parabens) are
used widely as preservatives in many thousands of cos-
metic, food and pharmaceutical products (Elder, 1984).
These simple esters have proved to be very effective anti-
microbial agents, with antimicrobial activity increasing with
the length of the alkyl grouping from methyl to n-butyl
(Murrell & Vincent, 1950), and it is the simplicity and
effectiveness of these compounds that have resulted in their
widespread use. As such, the human population is exposed
to parabens from a wide variety of sources on a daily basis.
Parabens are permitted as preservatives in food up to
0.1% and the average daily intake of parabens from food
by adult humans was estimated in 1984 to be 4–6 mg kg1
(Elder, 1984). In cosmetics, parabens are permitted in
concentrations of up to 1% (Elder, 1984). In 1984, it was
estimated that parabens were used in 13 200 different
cosmetic formulations (Elder, 1984) and a more recent
survey of 215 cosmetic products found that parabens were
used in 99% of leave-on products and in 77% of rinse-off
cosmetics (Rastogi et al., 1995).
Animal studies have shown that parabens are rapidly
absorbed, metabolized and excreted. Parabens are quickly
absorbed from the gastrointestinal tract and from blood,
hydrolysed to p-hydroxybenzoic acid, conjugated and the
conjugate excreted in the urine (Jones et al., 1956; Heim
et al., 1957; Tsukamoto & Terada, 1960, 1962, 1964;
Derache & Gourdon, 1963; Phillips et al., 1978; Kiwada
et al., 1979). Parabens also can be absorbed rapidly through
intact skin (Whitworth & Jun, 1973; Fischmeister et al.,
1975; Komatsu & Suzuki, 1979) and this can be influ-
enced by the presence of penetration enhancers found in
cosmetic preparations (Kitagawa et al., 1997). However,
the presence of carboxylesterases in skin and subcu-
taneous fatty tissues results in varying hydrolysis to p-
hydroxybenzoic acid (Lobemeier et al., 1996) and this can
also influence absorption (Bando et al., 1997). However,
the question remains as to whether any of the parabens
can enter the body intact from the long-term, low-dose
levels to which humans are exposed. Parabens have a high
oil/water partition coefficient and water solubility decreases
with increase in ester chain length (Elder, 1984). There-
fore, if any parabens do enter the human body intact, they
may be able to accumulate in fatty components of body
tissues in a similar manner to that of other lipophilic
6P. D. DARBRE ET AL.
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
pollutants that are known to bioaccumulate (Dobson
et al., 1989; Dobson, 1993; Sonawane, 1995; Hardell et al.,
1996; Guttes et al., 1998; Stellman et al., 1998, 2000; Darbre,
1998).
Most studies have indicated that parabens are not
mutagenic (Elder, 1984), but there are reports that they
can cause chromosomal aberrations (Ishidate et al., 1978),
particularly in the co-presence of polychlorinated biphenyls
(Matsuoka et al., 1979), and subcutaneous administration
of methylparaben has been reported to cause mammary
adenocarcinomas in rats (Mason et al., 1971). At a cellular
level, parabens have been shown capable of disrupting
cellular function through inhibiting secretion of lysosomal
enzymes (Bairati et al., 1994) and causing mitochondrial
dysfunction (Nakagawa & Maldeus, 1998). However, the
recent discovery that parabens possess oestrogenic activity
has challenged the concepts of their toxicity in new ways.
Because parabens can bind to oestrogen receptors, they
may be able to mediate unwanted effects at much lower
concentrations and more specifically than through non-
receptor mediated mechanisms.
The oestrogenic activity of parabens was first reported
in 1998 (Routledge et al., 1998). Since then, parabens have
been shown to bind to oestrogen receptors from different
sources, including rodent uterus (Routledge et al., 1998;
Blair et al., 2000; Fang et al., 2001) and MCF7 human breast
cancer cells (Byford et al., 2002; Darbre et al., 2002, 2003).
They have been shown to regulate oestrogen-responsive
reporter gene expression in yeast cells (Routledge et al.,
1998; Jin-Sung et al., 2000; Nishihara et al., 2000) and in
human breast cancer cells (Byford et al., 2002; Darbre
et al., 2002, 2003), and expression of the endogenous
oestrogen-regulated genes pS2 (Byford et al., 2002) and
progesterone receptor (Okubo et al., 2001) in breast
cancer cells. Parabens can increase the growth of MCF7
human breast cancer cells (Okubo et al., 2001; Byford
et al., 2002; Darbre et al., 2002, 2003), which can be blocked
with the antioestrogen ICI 182 780 (faslodex) (Byford
et al., 2002; Darbre et al., 2002, 2003), demonstrating the
growth effects to be oestrogen-receptor-mediated. Their
oestrogenic activity has been demonstrated also in animal
models in vivo in fish (Pedersen et al., 2000) and in
increasing uterine weight in immature rats (Routledge
et al., 1998) and immature mice (Darbre et al., 2002, 2003).
In line with other environmental oestrogens, butylparaben
has been shown also to be able to alter reproductive
function in male rats, including reduction in sperm counts
(Oishi, 2001). In general, the oestrogenic and antimicro-
bial activities of the parabens increase with the length and
branching of the alkyl ester (Darbre et al., 2002, 2003).
Because oestrogen is known to influence the incidence
of breast cancer (Lipworth, 1995) and ablation of oestro-
gen action remains the preferred treatment for hormone-
sensitive breast tumours (Miller, 1996), the presence of
oestrogenic chemicals in the breast area could potentially
influence both the incidence and treatment of breast
cancer. Parabens are used as preservatives in a range of
cosmetics applied to the underarm and breast area and it
has been suggested that regular application of such oestro-
genic chemicals could influence breast cancer development
(Darbre, 2001, 2003; Harvey, 2003). However, the outstand-
ing question remains as to whether parabens can enter
and accumulate in the human breast. Previous studies have
identified other environmental oestrogenic chemicals that
can accumulate in fatty tissue of the breast (Dobson, 1993;
Hardell et al., 1996; Guttes et al., 1998; Stellman et al.,
1998, 2000). This study has aimed to investigate whether
parabens also can be detected in human breast tissue,
using available breast tumour material. Initial experiments
enabled the extraction of total parabens from human breast
tissue to be visualized by thin-layer chromatography. More
detailed studies enabled identification and measurement
of individual parabens in human breast tumour samples by
high-pressure liquid chromatography (HPLC) followed by
tandem mass spectrometry (MS/MS).
MATERIALS AND METHODS
Human breast tumour material
Samples of human breast tumour material were collected
at the Edinburgh Breast Unit and stored in liquid nitrogen.
Chemical standards
Methylparaben, ethylparaben, n-propylparaben, n-
butylparaben and benzylparaben were purchased from
Sigma (Poole, UK). Isobutylparaben was a gift from Nipa
Laboratories (Mid-Glamorgan, UK). All compounds were
made as stock solutions of 0.1 M in ethanol.
Extraction of parabens from human breast material
and analysis by thin-layer chromatography
All glassware was pre-washed in 0.1 M NaOH and
extractions were performed using sterile polycarbonate
tubes (Falcon). Samples of human breast tissue (1 g) were
chopped finely with a sterile razor and homogenized in
5ml of hexane using a hand-homogenizer. Samples were
left in a sealed polycarbonate tube with mixing for 1 h and
then spun at 1500 rpm in a bench centrifuge at room tem-
perature for 2 min. The supernatant was placed in a sterile
polycarbonate tube, 5 ml of 0.1 M potassium bicarbonate
was added and the tube was inverted 40 times by hand.
The mixture was spun at 1500 rpm at room temperature
for 2 min to separate the phases. The upper yellow hexane
layer containing phenolic compounds was placed in a new
sterile polycarbonate tube, 5 ml of 0.1 M potassium car-
bonate was added and again the tube was inverted 40 times
by hand. The mixture was spun at 1500 rpm at room tem-
perature for 2 min to separate the phases. The lower aque-
ous layer containing the phenols as potassium salts was
taken into a new sterile polycarbonate tube and acidified
by the addition of 300 µl of concentrated hydrochloric acid
to give a pH in the 1–3 range (checked with pH paper).
The free phenolic compounds released on acidification were
extracted into 5 ml of diethyl ether by inverting the tube
by hand 40 times (Pope et al., 1990). The mixture was spun
at 1500 rpm at room temperature for 2 min to separate the
phases. The upper ether layer was removed and evaporated
to dryness under nitrogen overnight in a fume hood.
The extract was taken up in 50 µl of ethanol and ali-
quots were run against paraben standards (50–400 ng per
track) on thin-layer chromatography plates (DC-Alufolien
Kieselgel 60 F254, Merck; ca. 6 cm wide × 8 cm high) using
a solvent of 5% (v/v) ethanol–95% (v/v) chloroform. Para-
bens were visualized under ultravoiolet light. For quantita-
tion, the image under ultraviolet light was captured digitally
PARABENS IN HUMAN BREAST TUMOURS 7
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
and relative levels of bands were analysed by image analy-
sis using the software packages Transform 3.4 (Fortner)
and Origin 6.0.
Extraction of parabens from human breast tumour
material and analysis by HPLCMS/ MS
Samples of human breast tumour material (0.25 g) were
chopped finely with a sterile razor and homogenized in a
mixture of 6.25 ml of ethanol and 6.25 ml of acetone. This
mixture was left with periodic shaking overnight in a sealed
glass Corex tube. The next day, the mixture was spun at
2500 rpm for 10 min on a bench centrifuge at room tem-
perature. The supernatant was removed to a clean Corex
tube. The pellet was re-extracted with a further 1.5 ml of
ethanol and 1.5 ml of acetone, spun and the two supernat-
ants pooled. The total supernatant was dried under nitro-
gen at room temperature. To the residue was added 6 ml
of 70% (v/v) aqueous methanol; the mixture was vortexed
and then incubated overnight at 20 °C. The next day, the
mixture was spun at 3200 rpm for 20 min at 4 °C and the
supernatant was removed to a clean Corex tube. The pellet
was re-extracted with a further 1 ml of 70% (v/v) aqueous
methanol by vortexing and spun again at 3200 rpm for
20 min at 4 °C. The two supernatants were pooled and
dried under nitrogen for analysis by HPLCMS/MS.
The extracts were dissolved in HPLC mobile phase
(0.25 ml) and the paraben concentration determined by
HPLCMS/ MS. Samples (20 µl) of the final extracts were
chromatographed on a Hypersil Elite C18 column (150 ×
2.1 mm; 5 µm) at a flow rate of 0.3 ml min1 and eluted
with a linear binary gradient of 15 mM ammonium acetate
pH 4.5 (A) and acetonitrile (B) (t = 0 min A 70%, t =
15 min A 40%, t = 16 min A 70%, t = 25 min next injec-
tion). The HPLC retention times for the paraben stand-
ards are provided in Table 1. The parabens were detected
with a Sciex API 2000 triple quadrupole mass spectro-
meter equipped with a heated nebulizer probe operated
in the negative ion mode. Optimal setting of the instru-
ment for detection by mass reaction monitoring (MRM)
was established empirically by infusion of paraben stand-
ards (1 µgml
1). The mass transitions selected for MRM
detection utilized the fragmentation of the deprotonated
molecular ion and are listed in Table 1. Chromatographic
peaks corresponding to individual parabens were detected
automatically and the mass of analyte calculated after
interpolation from calibration curves prepared over the
working range 1–300 ng ml1 using the Analyst™ (PE
Biosystems) software package.
Extractions were performed in groups such that each
group of two to five tumour extractions had one blank
extraction carried out alongside, with all procedures iden-
tical except for the omission of tumour material. However,
analysis by HPLCMS/MS was carried out for all samples
on the same day sequentially. Final paraben concentrations
were calculated by subtraction of the values obtained from
the corresponding blank extraction. Because the blank
values showed variation, statistical analysis was performed
using the paired t-test method (Snedecor & Cochran, 1980).
RESULTS
Extraction of parabens from breast tissue and
detection by thin-layer chromatography
In initial exploratory experiments it was possible to
detect parabens in human breast tissue using the extrac-
tion procedures described in the Materials and Methods
section, followed by thin-layer chromatography against
paraben standards. Aliquots (10–400 ng) of methylparaben,
ethylparaben, n-propylparaben, n-butylparaben and iso-
butylparaben were run on thin-layer plates and could be
detected under ultraviolet light. Under these conditions all
the paraben standards ran to the same position, which was,
on average, 0.47 ± 0.03 of the distance to the solvent front.
Extracts of human breast tissue contained compounds
visible under ultraviolet light at the same relative position
as the paraben standards. From rough comparison by
eye of the relative levels of paraben standards, it was
estimated over six separate extractions that the samples
contained in the region of 10–50 ng paraben per g breast
tissue. Figure 1 shows the results of one experiment in
which three aliquots (97, 194 and 388 ng) of n-butylparaben
standards were run on thin-layer plates alongside the
extract of 1 g of breast tissue. The relative intensities of
the resulting bands under ultraviolet light were subjected
to image analysis and plotted as a standard curve shown in
Fig. 1. The relative intensity of the paraben band extracted
from 1 g of tissue was 11 730, which corresponded to 47.1 ng
paraben g1 tissue.
It was on the basis of these preliminary results that we
then proceeded to more detailed identification of individual
parabens by HPLCMS/MS
Extraction of parabens from human breast tumours
and analysis by HPLCMS/MS
Retention times and mass transition for MRM detection
for the six paraben standards are shown in Table 1.
Parabens were extracted from a sample of each of 20
human breast tumours and extracts were analysed by
HPLCMS/ MS against paraben standards as described in
the Materials and Methods section. Chromatographic peaks
due to methylparaben, ethylparaben, n-propylparaben,
n-butylparaben and isobutylparaben were seen in breast
tumour extracts and were well resolved from one another.
No peaks due to benzylparaben at its retention time
of 14.0 min were seen in any of the tumour extracts. A
typical chromatogram is shown in Fig. 2.
At a practical level, extractions were performed in
small groups such that each group contained between
two and five tumour samples together with one blank
extraction. The blank extraction was performed with all
procedures identical, except for the omission of tumour
Table 1—Paraben standards: HPLC retention times and mass
transition for MRM detection
Analyte HPLC retention Mass transition
time (min) (Q1–Q3;
m
/
z
)
for MRM detection
Methylparaben 4.6 151.1–92.1
Ethylparaben 7.3 165.1–92.1
n
-Propylparaben 10.6 179.1–92.1
Isobutylparaben 13.4 193.1–92.1
n
-Butylparaben 13.7 193.1–92.1
Benzylparaben 14.0 227.3– 92.1
8P. D. DARBRE ET AL.
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
Figure 1. Detection of parabens from human breast tissue by thin-layer chromatography. Three aliquots of
n
-butylparaben (97, 194 and
388 ng) were run as standards on thin-layer plates alongside the extract of 1 g of breast tissue, and the relative intensities of the resulting
bands under ultraviolet light were subjected to image analysis. The relative intensities of the bands for the three aliquots of
n
-
butylparaben were plotted as a standard curve as shown. The relative intensity of the paraben band extracted from 1 g of tissue was
11 730, which calculated to an equivalent of 47.1 ng of paraben.
material. The concentrations of parabens in the 20 tumours
as measured by HPLCMS/MS were corrected by subtrac-
tion of the corresponding blank value. Results are shown
in Table 2. Because the blank values showed variation, the
statistical significance of the mean corrected concentra-
tions of each paraben in the 20 tumour extracts was tested
by the paired t-test method, thus enabling the confidence
limits of these mean values to be calculated (Table 3).
The reasons for the blank values for parabens, and their
variation, are not clear. The MS data indicated that the
blank values were genuinely parabens and not other con-
taminating compounds. The blank values did not come
from the HPLCMS/MS procedure because blanks through
the equipment were entirely negative. The blank values
came from the extraction procedure itself. In a series of 30
blanks carried out on individual parts of the extraction
procedure, it was not possible to identify any one specific
reagent or procedure contributing to the blank value.
However, when blank values were subtracted from the
corresponding tumour extract values, 18/20 tumour extrac-
tions showed values of total paraben above the blank val-
ues. Values for total paraben present in the 20 tumour
samples were 0–54.5 ng g1 tissue, with an overall mean
value of 20.6 ng g1. Methylparaben was present at the high-
est level, with an average value of 12.8 ± 2.2 ng g1 tissue.
This represented 62% of the total paraben recovered in
the extraction. Benzylparaben was not detected in any
tumour extract.
Estimates of recovery of parabens from the extraction
procedure were made by spiking samples with benzylpara-
ben, because this was the only paraben not detected in
any blank or tumour extract. Analysis by HPLCMS/MS of
three extraction blank samples, each spiked with 200 ng of
benzylparaben, gave an average recovery of this paraben
of 48.5% ± 4.8%.
DISCUSSION
Mean concentrations of each of six parabens in extracts of
20 human breast tumours (in the range 0–12.8 ng g1 tissue;
Table 3) have been measured with acceptable confidence.
The reasons for the analytical blank values for parabens
in these studies have not been identified definitively but
probably relate to the ubiquitous use of parabens as pre-
servatives even in laboratory detergents and personal care
products of the operators. Analogous problems have been
encountered with the measurement of phthalate esters
because of their common use as plasticizers and their
ubiquitous dispersal as impurities in solvents, water, glass-
ware and many items of clinical and analytical laboratory
equipment (Lopez-Aviva et al., 1990; Leung & Giang, 1993;
Colon et al., 2000). More recent work in these laboratories
(unpublished) has shown that immersion of all glassware
in 1.0 M aqueous sodium hydroxide, followed by copious
rinsing with double-distilled water, prior to use of this glass-
ware in tissue extraction greatly reduces the blank values
of paraben concentrations as measured by HPLCMS/MS.
This addition to the analytical procedure is therefore
recommended for use in further studies on paraben
concentrations in tissues.
The total mean paraben level was found to be of the
order of 20 ng g1 tissue. This adds parabens to the list of
environmental oestrogenic chemicals that can be found
to accumulate in the human breast and already includes
polychlorinated biphenyls (PCBs) and organochlorine
pesticides (OCPs) (Dobson, 1993, Hardell et al., 1996;
Guttes et al., 1998; Stellman et al., 1998, 2000). Compar-
isons between the relative levels of parabens and other
pollutants are not easy because several factors have to be
PARABENS IN HUMAN BREAST TUMOURS 9
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
Figure 2. The HPLCMS/MS chromatograms for methylparaben, ethylparaben,
n
-propylparaben, isobutylparaben and
n
-butylparaben in
a human breast tumour extract. Tumour tissue was extracted as described in the text, chromatographed on a Hypersil Elite HPLC column
and detected by tandem mass spectrometry in the mass reaction monitoring mode. The annotated arrows indicate the identity of the
peaks evident in the chromatograms. Benzylparaben was not seen.
taken into account, including the source of tissue used and
the number of isomers or congeners. Most studies of
bioaccumulation of pollutant chemicals are carried out
by using serum or urine and studies using breast adipose
tissue are few. Furthermore, for parabens there are only
six commonly used forms whereas for PCBs there are 209
congeners. Studies of breast adipose tissue from women in
Long Island, New York, without breast cancer showed a
mean body burden for 14 PCB congeners of 267 ng g1 and
for seven OCPs of 707.5 ng g1 (Stellman et al., 1998).
However, Table 4 shows that levels in breast tissue of
individual pesticide residues and PCB congeners vary
substantially. Although knowledge of total body burdens
of these compounds is far from complete, the accumula-
tion of parabens in breast tissue does fall within the broad
range of these other compounds.
In the present study, paraben concentrations measured
in tumours were unequivocally of the esters themselves.
This demonstrates that at least a proportion of the parabens
present in cosmetic, food and pharmaceutical products can
be absorbed and retained in human body tissues without
hydrolysis by tissue esterases to the common metabolite p-
hydroxybenzoic acid. These results complement earlier
studies in which there was evidence that the oestrogenic
properties of these parabens in culture of human breast
cancer cells were also due to the esters themselves and not
to a common metabolite (Byford et al., 2002; Darbre et al.,
2002, 2003). However, these studies cannot identify either
the source of the parabens or whether they entered the
human body by an oral or by a topical route. Nor can they
identify whether the parabens entered the human breast
by a systemic route or through non-systemic mechanisms
involving simply local absorption and diffusion from chemi-
cal overload of topical preparations applied to the breast
area. Recent evaluation of parabens in uterotrophic assays
has shown them to give oestrogenic responses in immature
10 P. D. DARBRE ET AL.
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
Table 2—The HPLCMS/MS analysis of parabens in 20 human breast tumours
a
Tumour extract 12 34567891011121314151617181920Mean SEM
Benzylparaben 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Isobutylparaben 5.2 0.1 5.2 3.3 2.8 3.5 2.5 1.9 4.9 2.2 1.7 3.9 2.2 2.3 1.2 2.0 1.7 0.0 1.0 0.0 2.4 0.4
n
-Butylparaben 15.3 7.2 29.5 22.4 14.3 15.5 9.8 6.7 10.3 7.4 2.4 14.7 7.1 6.7 7.4 7.2 5.3 3.1 5.7 3.2 10.1 1.5
n
-Propylparaben 6.5 7.9 18.6 18.4 10.9 17.9 10.0 10.5 11.6 6.9 9.1 16.5 10.2 17.2 10.1 15.4 4.2 5.3 5.5 5.6 10.9 1.1
Ethylparaben 7.2 3.0 9.6 6.3 4.6 2.3 1.9 1.8 7.0 3.2 1.8 6.4 2.1 4.5 1.1 2.2 1.8 0.7 2.0 2.1 3.6 0.6
Methylparaben 34.2 20.6 53.0 49.9 34.4 37.6 27.3 19.6 35.7 16.0 17.2 36.4 21.6 39.6 18.5 28.8 36.7 8.2 12.0 10.7 27.9 2.8
Total paraben 68.3 38.8 115.9 100.3 67.0 76.9 51.4 40.4 69.5 35.7 32.1 77.9 43.1 70.3 38.3 55.6 49.7 17.3 26.2 21.6 54.8 5.8
Blank value 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Mean SEM
as 1 as 3 as 3 as 6 as 6 as 6 as 10 as 10 as 10 as 10 as 15 as 15 as 18 as 18
Benzylparaben 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Isobutylparaben 0.0 0.0 2.2 2.1 2.3 1.1 1.3 0.4
n
-Butylparaben 6.5 18.0 9.3 4.0 8.2 2.2 8.0 2.3
n
-Propylparaben 2.0 13.4 12.0 6.8 8.4 4.8 7.9 1.8
Ethylparaben 1.9 2.2 1.9 1.9 0.0 1.6 1.6 0.3
Methylparaben 10.1 27.8 20.5 10.3 11.6 9.9 15.0 3.0
Total paraben 20.5 61.4 45.9 25.0 30.6 19.6 33.8 6.8
Tumour less blank 12 3 4 567891011121314151617181920MeanSEM
Benzylparaben 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Isobutylparaben 5.2 0.1 5.2 3.3 2.8 1.3 0.3 0.3 2.7 0.2 0.4 1.8 0.1 0.2 1.1 0.3 0.6 1.1 0.1 1.1 0.9 0.4
n
-Butylparaben 8.8 0.7 11.5 4.4 3.7 6.2 0.5 2.6 1.0 3.4 1.6 10.7 3.1 2.7 0.8 1.0 2.9 1.0 3.5 1.0 2.3 1.0
n
-Propylparaben 4.5 5.9 5.2 5.0 2.5 5.9 2.0 1.5 0.4 0.2 2.3 9.7 3.4 10.4 1.7 7.0 4.3 0.5 0.7 0.8 2.6 0.9
Ethylparaben 5.3 1.2 7.4 4.1 2.4 0.5 0.0 0.1 5.1 1.3 0.2 4.5 0.2 2.6 1.1 2.1 1.8 0.9 0.4 0.5 2.0 0.5
Methylparaben 24.1 10.5 25.2 22.1 6.6 17.1 6.8 0.9 15.2 5.7 6.9 26.1 11.3 29.3 6.9 17.2 25.1 1.8 2.1 0.8 12.8 2.2
Total paraben 47.9 18.4 54.5 38.9 5.6 31.0 5.5 5.5 23.7 10.7 7.1 52.8 18.1 45.3 7.7 25.0 19.1 2.3 6.6 2.0 20.6 4.2
a
Paraben extractions were performed in small groups such that each group contained between two and five tumour samples together with one corresponding blank extraction. The blank
extraction was performed with all procedures identical except for the omission of tumour material. Results are shown in ng g
1
tumour for the 20 extractions and for the corresponding blank
values. The concentrations of parabens in the 20 tumours were then each corrected by subtraction of the corresponding blank value.
PARABENS IN HUMAN BREAST TUMOURS 11
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
epithelial cells in the human breast. Although in rodent
uterotrophic assays the levels of parabens were adminis-
tered at a higher range of 0.1–10 mg g1 body weight
(Routledge et al., 1998, Darbre et al., 2002, 2003), these
studies did not incorporate any measurements of paraben
levels reached in the uterus at the time of response, which
prevents assessment of the concentrations needed for physi-
ological response.
It is interesting that the paraben detected in greatest
amounts was methylparaben. This may reflect the more
widespread use of methylparaben in consumer products
(Rastogi et al., 1995). Alternatively, it may reflect the
greater ability of methylparaben to be absorbed into body
tissues and to resist hydrolysis by esterases of human skin
and subcutaneous fat tissue (Lobemeier et al., 1996). By
contrast, benzylparaben was not found in any of the 20
breast tumours and this may similarly be attributed to its
less frequent use in consumer products.
These measurements of paraben concentrations in breast
tumours open the way technically to more detailed
determinations of paraben levels in human body tissues.
This study used 20 breast tumour samples because of the
availability of the material. However, it will now be im-
portant to measure levels in corresponding normal tissue
to determine whether there is any difference between
normal and cancer tissues. Larger studies also are needed
to give more representative values for body burdens in
different tissues and across the human population. A main
problem with human breast tumour samples is the varied
infiltration of the tumour with fatty tissue and blood
vessels and it will be important in future work therefore to
have more precise histological information on the tumours
in order especially to be able to relate results to fatty versus
non-fatty tissue. It would be informative to ascertain
whether there are any gradients in the accumulation of
Table 3— Confidence limits of mean concentrations (ng g1) of
parabens in the 20 human breast tumours of Table 2
Tumour minus blank Mean Confidence limit
Benzylparaben 0.0 0.0– 0.0 (95%)
Isobutylparaben 0.9 0.1–1.7 (90%)
n
-Butylparaben 2.3 0.3– 4.3 (95%)
n
-Propylparaben 2.6 0.7–4.5 (95%)
Ethylparaben 2.0 1.0– 3.0 (95%)
Methylparaben 12.8 8.2 –17.4 (95%)
Total paraben 20.6 11.8–29.4 (95%)
Table 4—Summary of mean concentrations (ng g1) of individual pesticide residues and PCB congeners in human
breast adipose tissue from control and breast cancer patients from two published studies
Pesticide or PCB Control Breast cancer Control Breast cancer
HCB 206 343 16 18
β
HCH 72 84 16 20
Oxychlordane 39 46
trans
-Nonachlor 40 51
p
,
p
-DDE 450 838 374 419
o
,
p
-DDD 13 16
p
,
p
-DDT 24 30 12 12
PCB 74 27 30
PCB 99 14 19
PCB 118 58 85 24 30
PCB 138 176 241 22 29
PCB 146 79
PCB 153 437 664 63 76
PCB 156 61 64 9 11
PCB 167 12
PCB 170 229 259 11 14
PCB 172 22
PCB 178 34
PCB 180 258 400 34 42
PCB 183 46
PCB 187 13 16
Reference Guttes
et al.
(1998) Guttes
et al.
(1998) Stellman
et al.
(2000) Stellman
et al.
(2000)
Location Hesse, Germany Hesse, Germany New York, USA New York, USA
Number of samples
n
= 20
n
= 45
n
= 323
n
= 232
rodent uterus only when administered subcutaneously
or topically but not orally (Routledge et al., 1998; Hossaini
et al., 2000; Darbre et al., 2002, 2003), which suggests that
skin penetration may be an important route for entry to
the body.
A major issue in studies of accumulation of environ-
mental pollutants in body tissues is whether the levels
reached could be sufficiently high to exert any biological
action. In four of the 20 tumours, total paraben concen-
tration was more than twice the average level and, allow-
ing for a 50% recovery of parabens through the analytical
procedure, the corrected average level of parabens was
ca. 100 ng g1 tissue. This concentration may be compared
with the level (ca. 150 ng ml1; 106M) in culture med-
ium at which n-propylparaben, n-butylparaben and iso-
butylparaben stimulated growth of oestrogen-dependent
MCF7 human breast cancer cells (Okubo et al., 2001;
Byford et al., 2002; Darbre et al., 2002, 2003). It is there-
fore not inconceivable that the levels of parabens meas-
ured in this study could exert oestrogenic effects on
12 P. D. DARBRE ET AL.
Copyright © 2004 John Wiley & Sons, Ltd. J. Appl. Toxicol. 24, 5–13 (2004)
parabens across the human breast from axilla to sternum
in case the topical application of cosmetic at one place
influences the levels of parabens detectable. It will also
be important to know whether there is any difference
between levels detectable in breast tumours compared
with adjacent non-tumour material in order to determine
whether higher levels of paraben accumulation might be
present in the tumours. Such information, taken together
with that of concentrations in tissues of endogenous steroid
hormones and other xenoestrogens, should enable assess-
ment to be made of the impact of these weakly oestro-
genic parabens on human health, and whether paraben
accumulation from currently permitted levels in cosmetics,
foods and pharmaceuticals remains acceptable.
Acknowledgements
We are grateful for financial support from the Seedcorn Fund of the Veterinary
Laboratories Agency (P.D.D., N.G.S., M.J.S.) and for statistical advice from
Dr M. C. Denham, School of Applied Statistics, University of Reading.
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... Parabens are chemicals widely used as preservatives and bactericides in pharmaceuticals, food products, and cosmetics. Methylparaben (MP), a methyl ester of p-hydroxybenzoic acid, was found to penetrate the skin to a great extent and was found in large amounts in breast cancer tissues (Darbre et al. 2004;El Hussein et al. 2007;Dambal et al. 2017). Chronic MP exposure is shown to have defects in neural development, adverse effects on cardiac functions, and behavior which is depicted by the changes in serotonin level, ache activity and altered hypoxic gene expression (Thakkar et al. 2021). ...
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The biological fates of ethylparaben (EP) which has been widely used as a preservative for the pharmaceutical preparations and foods, and p-hydroxybenzoic acid (HB) which is the parent compound of EP, were investigated at the dose of practical usage (2 mg/kg) in rats. Although both EP and HB were metabolized to glycine conjugate (M1), ester type glucuronide (M3) and sulfate (M4) of HB and excreted in the urine and bile, the excretion ratios were different as compared with the results of higher dose experiments carried out by other authors, and a route dependency was also found in the rate of excretion in the bile. The excretion data obtained in this study are shown as follows: In intravenous administration of EP, the excreted total activity was 91.3% per dose in the urine and 5.97% in the bile, and percentages per dose of the major metabolites excreted in the urine were 8.14% of HB, 39.6% of M1, 29.5% of M3 and 6.48% of M4. In intraduodenal administration of EP, the excreted total activity (83.5%) and the activity excreted as HB (3.51%) decreased compared with the intravenous administration. In the HB administration, the route dependency of the total activity was not found, but a decrease in the excretion of HB in the intraduodenal administration was found. The excretion of total radioactivity almost ceased by 5 hr and the biological half-lives obtained from the β-phase of the sigma-minus plots of the metabolites excreted in the urine were 40-70 min. The results obtained in this study differ from those of other authors at the high dose experiments.
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Die bei 37,5° mit Sauerstoffgesättigter Tyrodelösung durchströmte Mäuseleber hydrolysierte mindestens 0,151 mg p-Oxybenzoesäureäthylester/g Leber/min zu p-Oxybenzoesäure. Nach peroraler Aufnahme von 10–20 mg Ester/kg Körpergewicht lassen sich im Serum des Menschen in den folgenden 4 Std kein freier Ester, aber p-Oxybenzoesäure nachweisen. Nach peroraler Verabreichung von 25, 100 und 500mg Ester/kg ist in den folgenden 8 Std im Serum des Hundes nur nach 500 mg/kg unveränderter Ester nachweisbar. Die p-Oxybenzoesäurekonzentrationen des Serums entsprechen den verabreichten Estermengen.
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An assay procedure comprising plasma oestrogen extraction into ether, separation of phenolic steroids (oestrogens) from non-phenolic matter, separation of oestrogens by chromatography on Sephadex LH20 and their radioimmunoassay (RIA), using oestrogen-specific antiserum, has shown sub-capsular, testis venous plasma, pooled from intact and hemi-castrated, prepubertal lambs to contain concentrations of oestradiol-17β in the range 80–120 pg/ml. By this same procedure, jugular plasma of these lambs contained significant (P < 0.05) concentrations of oestradiol-17β ranging up to 4.2 pg/ml. Jugular venous plasma of castrated lambs collected at 4 and 9.6 weeks of age also contained significant concentrations of oestradiol-17β (0.46 pg/ml and 1.03 pg/ml respectively).
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The frog, Rana pipiens, was found to take up certain p-hydroxybenzoates when partially immersed in a solution of these substances. The order of decreasing uptake rates for the benzoates was butyl, propyl, ethyl, and methyl. The presence of a nonionic surfactant, polysorbate 20, reversed the order; however, a biological surfactant, sodium cholate, appeared to increase the rate of uptake of the parabens. The process was first order.