Tohoku
J. exp.
Med.,
1975, 116, 379-384
Mercury
in Red
Mercury
in
Blood
Cells
in Relation
to Organic
Hair
TSUGUYOSHI SUZUKI and
TOMOYO MIYAMA*
Department of Public Health, Tohoku University School of Medicine,Sendai, and Departmentof Public Health,* Japan Women's Collegeof Physical Education, Tokyo
SUZUKI, T. and MIYAMA, T. Mercury in Red Blood Cells in Relation to Organic Mercury in Hair. Tohoku J. exp. Med., 1975, 116 (4), 379-384To check the usefulness of the hair mercury value for evaluation of intake of mercury, total mercury in red cells and organic mercury in hair were measured and compared on islanders whose fish consumption varied to a considerable extent. On both the male and the female, correlations of these two mercury levels were significant. The slopes of regression lines did not differ between the male and the female, but the level of hair organic mercury was higher in the male than in the female. Age-differences were observed in the red cell-to-hair relationship of mercury, i.e. the age-group aged 50 and over had much milder slopes than the group aged 20-49 in both the male and the female. The importance of agematching was mentioned. mercury; organic merucry; mercury in hair; mercury in red blood cells
There have been several reports dealing with the relation between total mercury levels in hair and in blood on populations including heavy fish-eaters (Tejning 1967; Sumari et al. 1969; Birke et al. 1972). But, as our knowledge on environmental mercury has increased, this relation becomes of necessity to be studied again in consideration of newly emerged or unsolved problems (Friberg and Vostal 1972; Hartung and Dinman 1972; Miller and Clarkson 1973). The first problem is associated with the chemical form of mercury in the environment. In populations without any occupational and pharmaceutical exposure to mercurials, the most prevailing is methylmercury, which is usually taken into humans via fish-consumption. The red blood cell-to-plasma ratio of methylmercury in human blood has been reported to be dependent upon the level of it in blood (Suzuki et al. 1971a), but usually as high as 9 to 1 (Swensson et al. 1959; Suzuki et al. 1971a). Thus, as far as methylmercury is concerned, not the level of mercury in blood but that in red blood cells is regarded as suitable in discussions of relation between mercury contents in blood and in hair. As to mercury in hair, it is naturally better to use methylmercury levels instead of total mercury ones on account of external contamination with ambient inorganic mercury or mercury vapor, or mercurials in cosmetics (Yamaguchi et al. 1975). Received
for publication,
May
21, 1975. 379
380
T. Suzuki
and
T. Miyama
The second is the sampling of hair, i.e. the mercury content may differ according to body sites of hair sampling and the sampled part of the hair grown (Skerfving 1974; Ishihara et al. 1974; Yamanaka and Ueda 1974). If only the basal part of hair be sampled, the relation between mercury levels in blood and in hair may be more direct compared with the case that the end of hair is sampled. When the intake of mercury fluctuates seasonally, this is the problem of great importance. Hitherto, the age or the sex has not been taken into account of for examining the relation. Some authors become to claim the sex-difference on the level of mercury in hair (Nishima et al. 1971; Ohmoto et al. 1975), and the influence due to sex and/or age has been reported on copper, zinc and lead concentrations in hair (Klevay 1970, 1972; Klevay and Forks 1973). For reasons mentioned above, the relation of total mercury contents in red blood cells to organic mercury concentrations in hair was studied in islanders on the Tokara Islands of Japan and Americans of Japanese ancestry living on Oahu Island, Hawaii. SUBJECT On
three
located islanders; 11
Tokara
southwest 55
and
of
Japanese
examined.
tion
are
shown
in
on
(Suzuki
the
veiwpoint
Methods
of
oxidized
and
the
and
of
human
ecology.
with
(1969). Hair
cm
in
any
detergent, was for as
from
the
blood
a centrifugation. of were
were end
with
min.
to
The
to
examined
in
notes
the
results detail
of
habits,
will of
on
course
fish-eating
main the
male
be
the
will
112
islanders
and
7
fish
consump on
the in
be
,
female
studies and
published
study
are
islands,
Tokara
4
brief
which of
these
Hawaii; and
were
which
by
the
The
oxidized
correspond
addition
Island,
activities,
of
extracted
oxidized 30
subjects
in
solution
samples
were
at
metry
a
length
extract
ml
solutions
Cernik
60•Ž
10 separated
Hair.
the
Takarajima,
Ryukyu-arc
, the
intake
a separate
described
from
determination
oxidized
2-3
to
preparation),
were
Oahu
the
age-distributions,
island-ecosystems. in
and
to In
on
subsistence
al.
About
cells
were
small
All human
belong
examined.
living
study,
et
mercury
Blood. blood
1.
and
were
of
among
mercury
article
female,
year
Suwanosejima,
Island
ancestry
Table
METHODS
Kuchinoshima,
Kyushu
57
The
inter-relationship of
the
male
Americans
were
Islands; of
AND
acid by
from
organic
solution of
red
nitric
of
of of
1
by
obtained
concentration
or a
head cut
and the by
(Miyama
2 ml
reflux
.
mercury
the et
.
were
washed
with
, and the permanganate
HCl-
vapor
photo
was
proved
procedure al
,
Magos
cuttings
, not acid
potassium
same
Red
plasma
by
The
hair
. of
condenser
photometry
hydrochloric
acid
measured value
the
finely
N
heparinized
cells
using
vapor
part mg
and blood
acid
sulphuric
was The
of
mercury
occipital
a
solution
mercury
and
hundred
solution samples.
venipuncture ml
the
A
with
a mixed oxidized
the
hair.
by One
measured
cut of
sampled
sulphuric
twice
blood
the
were
1973).
RESULTS Correlations in
between
levels
of
total
mercury
in
red
blood
cells
and
of
organic
mercury
hair
The
difference
of
levels
in
red
blood
cells
and
in
hair
according
to
islands
will
Mercury
TABLE 1.
in Hair
and Erythrocytes
381
Number and age of subjects studied
be described and discussedin relation to the kind and quantity of fish consumed in the separate report (Suzuki et al. in prep.). Therefore,in this report, the relation between hair levels and red blood cell levels is presented. There are significant correlations between levels of total mercury in red blood cells and of organic mercury in hair as is shown in Fig. 1. Two regressionequations: Y (organic mercury in hair) on X (total mercury in red cells), and X on Y, are calculated by sex, and all the regressioncoefficientsare statistically significant. As to the slope of regressions,there is no sex-difference, but the level of organic mercury in hair is significantlyhigher in the male than in the female. There is no significantdifferencebetween the male and the female on the level of total mercury in red blood cells. Age-differences in the relation of total mercuryin red bloodcellsto organicmercuryin hair Table 2 shows the levels of total mercury in red blood cells and of organic mercury in hair by age-groups, and correlation coefficientsand regression equa tions between red blood cell levels and hair levels. The youngest age group had the lowestlevel both in total mercury in red bloodcellsand in organicmercuryin hair on both sexes, and no significant correlation was found on either male or female. Two adult groups of each sexes had nearly identical averages on the levels in red blood cells and in hair. Significant correlations were found in all the adult groups, but the slope of regression was steeper in the group of 20-49 years old than in the group of 50 and over in both sexes. DISCUSSION In this study, the end of hair was sampled. This means that the period of
382
T. Suzuki
and T. Miyama
Fig. 1. The relationship between the organic mercury content in hair and the total mercury content in red blood cells. The solid line is a regression line of the organic mercury content in hair (Y) on the total mercury content in red blood cells (X), and the broken line is a regression line of X on Y, and the equations obtained are as follows: Male: Y=59X+4.4, X=0.0074Y+0.0015, Female: Y=48X+2.2, X=0.0106Y+0.0036. All the regression coefficients are significant by the F-statistic (p
J. exp.
Med.,
1975, 116, 379-384
Mercury
in Red
Mercury
in
Blood
Cells
in Relation
to Organic
Hair
TSUGUYOSHI SUZUKI and
TOMOYO MIYAMA*
Department of Public Health, Tohoku University School of Medicine,Sendai, and Departmentof Public Health,* Japan Women's Collegeof Physical Education, Tokyo
SUZUKI, T. and MIYAMA, T. Mercury in Red Blood Cells in Relation to Organic Mercury in Hair. Tohoku J. exp. Med., 1975, 116 (4), 379-384To check the usefulness of the hair mercury value for evaluation of intake of mercury, total mercury in red cells and organic mercury in hair were measured and compared on islanders whose fish consumption varied to a considerable extent. On both the male and the female, correlations of these two mercury levels were significant. The slopes of regression lines did not differ between the male and the female, but the level of hair organic mercury was higher in the male than in the female. Age-differences were observed in the red cell-to-hair relationship of mercury, i.e. the age-group aged 50 and over had much milder slopes than the group aged 20-49 in both the male and the female. The importance of agematching was mentioned. mercury; organic merucry; mercury in hair; mercury in red blood cells
There have been several reports dealing with the relation between total mercury levels in hair and in blood on populations including heavy fish-eaters (Tejning 1967; Sumari et al. 1969; Birke et al. 1972). But, as our knowledge on environmental mercury has increased, this relation becomes of necessity to be studied again in consideration of newly emerged or unsolved problems (Friberg and Vostal 1972; Hartung and Dinman 1972; Miller and Clarkson 1973). The first problem is associated with the chemical form of mercury in the environment. In populations without any occupational and pharmaceutical exposure to mercurials, the most prevailing is methylmercury, which is usually taken into humans via fish-consumption. The red blood cell-to-plasma ratio of methylmercury in human blood has been reported to be dependent upon the level of it in blood (Suzuki et al. 1971a), but usually as high as 9 to 1 (Swensson et al. 1959; Suzuki et al. 1971a). Thus, as far as methylmercury is concerned, not the level of mercury in blood but that in red blood cells is regarded as suitable in discussions of relation between mercury contents in blood and in hair. As to mercury in hair, it is naturally better to use methylmercury levels instead of total mercury ones on account of external contamination with ambient inorganic mercury or mercury vapor, or mercurials in cosmetics (Yamaguchi et al. 1975). Received
for publication,
May
21, 1975. 379
380
T. Suzuki
and
T. Miyama
The second is the sampling of hair, i.e. the mercury content may differ according to body sites of hair sampling and the sampled part of the hair grown (Skerfving 1974; Ishihara et al. 1974; Yamanaka and Ueda 1974). If only the basal part of hair be sampled, the relation between mercury levels in blood and in hair may be more direct compared with the case that the end of hair is sampled. When the intake of mercury fluctuates seasonally, this is the problem of great importance. Hitherto, the age or the sex has not been taken into account of for examining the relation. Some authors become to claim the sex-difference on the level of mercury in hair (Nishima et al. 1971; Ohmoto et al. 1975), and the influence due to sex and/or age has been reported on copper, zinc and lead concentrations in hair (Klevay 1970, 1972; Klevay and Forks 1973). For reasons mentioned above, the relation of total mercury contents in red blood cells to organic mercury concentrations in hair was studied in islanders on the Tokara Islands of Japan and Americans of Japanese ancestry living on Oahu Island, Hawaii. SUBJECT On
three
located islanders; 11
Tokara
southwest 55
and
of
Japanese
examined.
tion
are
shown
in
on
(Suzuki
the
veiwpoint
Methods
of
oxidized
and
the
and
of
human
ecology.
with
(1969). Hair
cm
in
any
detergent, was for as
from
the
blood
a centrifugation. of were
were end
with
min.
to
The
to
examined
in
notes
the
results detail
of
habits,
will of
on
course
fish-eating
main the
male
be
the
will
112
islanders
and
7
fish
consump on
the in
be
,
female
studies and
published
study
are
islands,
Tokara
4
brief
which of
these
Hawaii; and
were
which
by
the
The
oxidized
correspond
addition
Island,
activities,
of
extracted
oxidized 30
subjects
in
solution
samples
were
at
metry
a
length
extract
ml
solutions
Cernik
60•Ž
10 separated
Hair.
the
Takarajima,
Ryukyu-arc
, the
intake
a separate
described
from
determination
oxidized
2-3
to
preparation),
were
Oahu
the
age-distributions,
island-ecosystems. in
and
to In
on
subsistence
al.
About
cells
were
small
All human
belong
examined.
living
study,
et
mercury
Blood. blood
1.
and
were
of
among
mercury
article
female,
year
Suwanosejima,
Island
ancestry
Table
METHODS
Kuchinoshima,
Kyushu
57
The
inter-relationship of
the
male
Americans
were
Islands; of
AND
acid by
from
organic
solution of
red
nitric
of
of of
1
by
obtained
concentration
or a
head cut
and the by
(Miyama
2 ml
reflux
.
mercury
the et
.
were
washed
with
, and the permanganate
HCl-
vapor
photo
was
proved
procedure al
,
Magos
cuttings
, not acid
potassium
same
Red
plasma
by
The
hair
. of
condenser
photometry
hydrochloric
acid
measured value
the
finely
N
heparinized
cells
using
vapor
part mg
and blood
acid
sulphuric
was The
of
mercury
occipital
a
solution
mercury
and
hundred
solution samples.
venipuncture ml
the
A
with
a mixed oxidized
the
hair.
by One
measured
cut of
sampled
sulphuric
twice
blood
the
were
1973).
RESULTS Correlations in
between
levels
of
total
mercury
in
red
blood
cells
and
of
organic
mercury
hair
The
difference
of
levels
in
red
blood
cells
and
in
hair
according
to
islands
will
Mercury
TABLE 1.
in Hair
and Erythrocytes
381
Number and age of subjects studied
be described and discussedin relation to the kind and quantity of fish consumed in the separate report (Suzuki et al. in prep.). Therefore,in this report, the relation between hair levels and red blood cell levels is presented. There are significant correlations between levels of total mercury in red blood cells and of organic mercury in hair as is shown in Fig. 1. Two regressionequations: Y (organic mercury in hair) on X (total mercury in red cells), and X on Y, are calculated by sex, and all the regressioncoefficientsare statistically significant. As to the slope of regressions,there is no sex-difference, but the level of organic mercury in hair is significantlyhigher in the male than in the female. There is no significantdifferencebetween the male and the female on the level of total mercury in red blood cells. Age-differences in the relation of total mercuryin red bloodcellsto organicmercuryin hair Table 2 shows the levels of total mercury in red blood cells and of organic mercury in hair by age-groups, and correlation coefficientsand regression equa tions between red blood cell levels and hair levels. The youngest age group had the lowestlevel both in total mercury in red bloodcellsand in organicmercuryin hair on both sexes, and no significant correlation was found on either male or female. Two adult groups of each sexes had nearly identical averages on the levels in red blood cells and in hair. Significant correlations were found in all the adult groups, but the slope of regression was steeper in the group of 20-49 years old than in the group of 50 and over in both sexes. DISCUSSION In this study, the end of hair was sampled. This means that the period of
382
T. Suzuki
and T. Miyama
Fig. 1. The relationship between the organic mercury content in hair and the total mercury content in red blood cells. The solid line is a regression line of the organic mercury content in hair (Y) on the total mercury content in red blood cells (X), and the broken line is a regression line of X on Y, and the equations obtained are as follows: Male: Y=59X+4.4, X=0.0074Y+0.0015, Female: Y=48X+2.2, X=0.0106Y+0.0036. All the regression coefficients are significant by the F-statistic (p
