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The Japan Association of Activation Analysis
NII-Electronic Library Service
The JapanAssociation of Activation Analysis
Selenium
in
human nails: a preliminary
study using INAA
Boon Siong
Weei',
Mohd.
Fahmi
Abdul Rahman2, Mohd, Suhaimi Hamzahi
iMal4ysian NticlearAgency,
Bangi,
43000 Kdjang, Selango4 Malaysia.
2thculty ofSbience
and 11echnology, Uhiversity Kebangsaan
Malaysia,
43600 Bangi,
SelangoL Malaysia.
'Corresponding author. E-mail: wee@nuclearmalaysia,gov.my
Abstract
Selenium (Se)
is an essential trace element for healthy body fimctions
in
humans. Deficiency
of Se
may
cause diseases
such as cancer and cardiovascular disease. However, Se toxicity or selenosis can also
occur in
humans as a result of high doses of dietary intake or industrial exposure. This study aims to use
human nails for biomonitoring of Se in a healthy Malaysian adult. The results are used to assess
long-terrn
Se status and comparisons are made with literature values. Instrumental
neutron activation
analyses (INAA)
were used to
deterrnine
Se in nail samples collected in a 5-month period.
There were 1O
fingernail
sarnples and 3 toenail samples. Results showed that fingernails contain an average of 1.06
±
O.05 pg/g Se (range:
O.98 - 1.13 pglg Se) and toenails contain an average ofO.94 ± O.07
pglg
Se (range:
O.89 - 1.02 pgfg
Se), Temporal variations of fingernail and toenail
Se contents were rather small with
RSD of less
than
10%.
Fingernails
show slightly higher Se contents than those of toenails. Both
fingernails
and toenails show reproducibility of Se concentrations taken during
the sampling period.
These
results are in agreement with literature values for
healthy
individuals,
which show no deficiency
or
chronic exposures to Se in
the
past
months. Thus, there is no potential
health risk in the subject studied.
Kayworzts: Biomonitoring, Slelenium, human nails, LNAA.
Introduction
Selenium
(Se)
is
an essential trace
element for producing
Se-containing proteins
or selenoproteins
important
fbr
biological
functions.
Reilly [1]
reported that diseases and conditions of humans associated
wnh Se
deficiency
include dial)etes, cystic fibrosis, Keshan disease, cancer and muscular dystrophy,
Selenium deficiency can be prevented
through dietary intake
of fbod
with high
Se content such as meat,
fish
and eggs. Besides,
Se supplement in the fbrm of sodium selenite, sodium selenate,
L-selenomethionine
and selenium-emiched yeast
can be used to compensate a low dietary intake [2].
The
U.S.
Recomrnended Dietary
Intakes (RDIs)
for Se is 55 pg/d
and the tolerable Upper Intake
Level
(UL)
is
400 pgfd
[3],
In
Malaysia,
the
Recommended Nutrient Intakes (RNIs)
for men and women are 33 pg Se/d
and 25
pg Seld,
respectively [4],
Through sufficient dietary intake, Se compounds can help
to prevent
and
to treat cancer [5],
However, excess of Se intake
may cause genotoxic
effects but
the mechanisms are not
fu11y understood [5].
Because of potential
harmfu1 effects of Se deficiency and toxicity,
it
is
of great
importance
to
monitor the level
of Se in
humans through the use of biomonitors. To date, Se contents in
various
biological
samples such as blood, skeletal muscle, urine, intemal organs, breast milk, hair
and nails have
been
reported (e.g.
[6]).
For recent Se intake, blood and urine are commonly used whereas human nails
are analyzed for long-term (6
to 12 month period)
Se intake,
The chemical composition ofnail is
stable
after its
formation
and will not be affbcted by blood chemistry or chemical exposure [7],
The growth rate
of fingernails is about O.1 mmlday and toenails grow O.03-O.05 mmlday [8].
Collection
and storage of
nails is simple and small amounts (about
50 - 100
mg) are adequate for
chemical analysis. The INAA
method utilized in
this
study is
sensitive
for determination of Se contents in nail samples. The
biomonitoring
of
trace
elements such as Se using nail samples is still lacking in Malaysia.
Therefbre,
this
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The Japan Association of Activation Analysis
NII-Electronic Library Service
The JapanAssociation of Activation Analysis
study aims to use human nails for biomonitoring of Se in a healthy Malaysian adult. The results are used
to assess the Se status and comparisons are made with literature
values.
Materials
and Method
Sample collection andpreparation
Fingernails
and toenails
from every digit were collected from a healthy
male volunteer with no
history
ofsmoking and selenium supplement use. The age ofthe subject is 35 years
old. Sampling
period
was from January
to
May 2011 (Table
1).
The numbers oftoenails collected in this study were less than
fingernails
due to slow growth rate. All nail samples were collected using a clipper and kept
in
polyethylene
bags.
The samples were washed with acetone for 20 minutes in ultrasonic bath.
After
that,
the
samples were washed twice with deionized
water for 20 minutes. Finally, the samples were washed
with acetone for 20 minutes and kept in desiccators for
drying.
instrumentat neutron activation analysis
Each nail sample (about
60 - 1OO mg) was packed separately into cleaned polyethylene
vials. About
50 mg ofreference materials namely NIST SRM 1566b (Oyster
tissue) and IAEA-086 (Human
hair)
were
included
as comparative standard and quality
control material, respectively. Empty
vial was also included
for
blank
correction. Gold standard solutions (about
10 pg Au) were pipetted
onto filter
papers
and
attached to
all
samples and reference materials as neutron flux monitor for flux correction during
irradiation.
All
samples, blank and reference materials were subjected to
6 hours
irradiation
at the IMW
TRIGA MKII reactor ofMalaysian Nuclear
Agency
with a thermal neutron flux
of about 10i2
n･cm-2-s-i.
After
the
irradiation,
gold
monitors were counted first after 4 days decay while the other samples and
standards were counted after 4 weeks decay and counting time for each sample was about 24 hours.
Gamma-ray measurements were perfbrmed using a calibrated HPGe detector
with GammaVision
software [9], The Au was measured using the
41
1.8
keV gamma-ray peak of i98Au (halfilife
2.69 days).
The decay-corrected
specific activity of Au for NIST SRM 1566b (Oyster
tissue)
was used as a reference
and all other Au monitors were compared against it. Results showed that variations of the
specific
activities of Au monitors were ranged from -7,4% to +1,8%. Therefore,
all Se concentrations were
corrected accordingly. Selenium was analyzed using the 136 and 264 keV gamma-rays of 7SSe (halflife
120.4
day). Computation of Se concentrations was based
on comparative method. Concentration
values
were reported as dry
weight basis.
Results
and Discussion
euality
control results
Selenium
in
IAEA-086
was determined
along with the nail samples as quality
control sample. The
result obtained in
this
study was 1.04
± O.1 1 pglg Se and in good agreement with the
reference value of
1.00
± O.09
pglg Se [1O].
Selenium concentration ofblank was O.O03 pgfg Se assuming a representative
sample mass ofO.2 g.
The limit
ofdetection (3u
ofblank) was about O.03 pglg Se,
Selenium concentrations in nail samples
The Se concentrations of nail samples are presented
in Table 1.
Average Se concentration of
fingernails
was 1.06
± O.05
pglg Se (range:
O.98 - 1.13 pglg Se) and toenails was O.94
± O.07
pglg Se
(range:
O.89
- 1.02
pgtg Se).
It
is evidenced that Se concentration in fingernails and toenails
show no
sigriificant difference.
On average the
Se of fingernails was al)out 13% higher than those
of toenails,
which concurs with previous
findings
[1
1].
The lower Se concentrations found in toenails is 1ikely related
to
a depletion
of Se in
the
blood supply to the feet and toes. Besides, no external exposure could be
directly
identified
to explain the slight variation between
fingernail
and toenail
Se contents. If
contamination did
occur, anomaly in
Se contents of
fingemails
could be detected in this study. Because of
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The Japan Association of Activation Analysis
NII-Electronic Library Service
The JapanAssociation of Activation Analysis
potential
contamination in fingernails, many previous
studies only analyze toenails (e.g.
[1
1], [12]).
This
study showed that temporal variations of fingernail and toenail Se contents were rather small with relative
standard deviation
(RSD)
ofless than 10%. The reproducibility of Se in fingernails and toenails indicates
that
no drastic
changes in
exposure or behaviors over the sampling period.
Besides, the Se values taking
into
consideration oftemporal variations could be very usefu1 in
estimating the average and ranges of Se
contents in
an individual. This study showed that data from both
fingernails and toenails
are informative
and should be assessed collectively when computing elementa1 composition.
Table
1:Seleniumconcentrations'entratlons
infinernailsandtoenails.Errorsare
Samle CollectiondateConcentration
Fl21Jan2011O.98 ±O.11
F28Feb20111.00 ±O.09
F319Feb20111.06 ±O.12
F41Mar20111.05 ±O.11
FingernailsF5F615Mar2011
27Mar20111.121.07
±
±
O.12O.11
F78Apr20111.12 ±O.11
F822Apr20111.13 ±O.12
F93Ma20111.06 ±O.10
Averae L06 ±e.os
Tl21Jan2011O.93 ±O,09
ToenailsT28Mar2011O.89 ±O.09
T319Apr20111.02 ±O.10
Averae O.94 ±e.o7
implicationsfrom Se contents in nail samples
The Se contents found
in
human nails may provide
some information
for
health
risk
assessment.
The monitoring carried out in this study would provide
meaningfu1 data
of Se levels
in
nails for
the
assessment ofhealth risk. Combining Se data of fingernails and toenails, the Se values fbund in this study
were within a therapeutic
range ofO,75 to 1.25 pgfg Se as reported by Morris et al. [1
1]. Thus, the present
data show no likely health risk in the subject studied.
There may be possible
health
risk
if
the
Se values
were lower or higher than the therapeutic range. A compilation of Se in nail samples from literature is
presented
in Table 2. Results from different
countries showed that
the
mean values of Se in
nails show
some similarities (O.8
- O.9 pglg) except for Denmark, New Zealand and Poland,
which are in
a lower
values (-
O.5 pg/g).
Variations ofnail Se contents could be related to geography,
diets
and lifestyle.
Data
from India, Sweden and America were within the therapeutic range where no adverse health risks are
expected. The Se centents lower than O.75 pg/g were reported (Table
2) fbr sarnples from Denmark, New
Zealand and Poland. Person having low Se may require supplementation of Se to increase the Se level in
the
body.
Research
showed that toenail Se content increases after taking selenium-enriched yeast
for
periods
ranging from 1 year
to 24 years [2],
Low Se contents in nails collected from older adults ofNew
Zealand were related to impaired physical
function [13].
In Poland, more than 90% of the studied
population
is at risk efchronic disease due to low Se
level [12],
Previous
studies have showed that
low Se
contents were related to some form ofdisease in humans. In order to prevent
these diseases, sufficient Se
intake should be recommended and the Se content in nails should be monitored periodically,
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The Japan Association of Activation Analysis
NII-Electronic Library Service
The JapanAssociation ofActivationAnalysis
Tal)le
2: Comparison of nail Se concentrations (pglg)
from different countries.
Coun Sam les Avera e± S.D. Reference
Denmark
India
Malaysia
Malaysia
New Zealand
Poland
Sweden
U,S.A.
U.SA.
Toenails (n
= 7)
Fingernails (n
= 33)
Fingernails (n
= 13)
Toenails (n
= 3)
Toenails (n
=- 507)
T,oenails (n
= 33 1)
Fingernails (n
- 96)
Toenails (n
- 3575)
Nails
n=285
O.49
± O.04
O.81
± O.04
1.06
± O.05
O.94
± O.07
O.60±O.40
O.58±O.13
O.94
± O.21
O.919±O.249
O.98
±
O.40
Behne
et al.
[2]
Samanta
et al. [14]
This
work
This
wotk
Islam
et al.
[13]
Zukowska et al. [12]
Rodushkin and Axelsson [15]
Morris et aL [11]
Mason et al. 16
Conclusions
The application of INAA method was able to determine Se reliably and accurately, and minimized
the possibility
of contarnination during sample preparations.
This study presents
the initial
investigation
using nail samples for biomonitoring of Se in
a healthy
person
in
Malaysia.
Selenium concentrations
reported here showed very good agreement to literature values that is within the range of O.75 to 1.25
pg/g.
No chronic exposure or deficiency of Se could be detected. Therefore,
no likely
health
risks
are
anticipated from
the subject studied. Considering the benefit of this study, a biomonitoring prograrn
of Se
status in Malaysian could be initiated.
References
[1]
Reilly C (1998)
Trends Food Sc Tech 9, 114-1 18.
[2]
Behne D, Alber D, Kyriakopoulos A. (201O)
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[3]
Otten JJ, Hellwig JP, Meyers LD (eds)(2006).
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requirements, National Academy of Science, U.S,A,
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