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United States
Environmental Protection
Agency
Health Effects
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S1 -86/004 Nov. 1986
Project Summary
Cadmium Intake Via Oysters
and Health Effects in New
Zealand: Cadmium Intake,
Metabolism and Effects in
People with a High Intake of
Oysters in New Zealand
Joan McKenzie, Tord Kjellstrom, and Ram Sharma
The aim of this study was to confirm
the high dietary intakes of cadmium
and other trace elements from oysters
in a population associated with the oys-
tering industry, and to determine (i) the
impact of those high intakes on cad-
mium concentrations in accessible tis-
sues of the study subjects and (ii) the
occurrence of health effects in the pop-
ulation resulting from their dietary ex-
posure to cadmium.
Methods for the analysis of cadmium
in whole blood, urine and hair by flame-
less atomic absorption spectrophoto-
metry were established. The analysis of
Bluff oysters (Ostrea lutaria) confirmed
a high cadmium content (27 jig/g dry
wt); the content of other trace ele-
ments (zinc, copper, manganese, sele-
nium) was also determined, and differ-
ences in the proportions of the trace
elements compared with other species
of oysters and other shellfish found in
New Zealand were observed.
Seventy-eight subjects participated;
from forty-eight of them samples of
faeces (3 day), blood, urine (overnight)
and hair were obtained both pre-
season and end-season (i.e., 6 months
later). Questionnaires on oyster intake
were administered; dietary and medi-
cal questionnaires were administered
at the end of the season when height,
weight and blood pressure were meas-
ured. The subjects were classified into
four categories of oyster intake with av-
erage consumptions being <0.5, 0.5-
<2,2-<6 and a6 dozen/week for Cate-
gories I, II, III and IV, respectively. The
faecal output of cadmium confirmed
the high intakes; e.g.. Category IV sub-
jects were ingesting about 250 |tg cad-
mium/day at the end of the season; cal-
culated intakes for Categories I, II and III
were 34 jig/d, 75 pg/d and 116 |ig/d,
respectively, at the end of the season.
Intakes of zinc were also elevated, and
selenium intake would have been dou-
bled for those subjects consuming
many oysters.
The concentration of cadmium in
whole blood was higher in the smokers
than in the non-smokers. In the non-
smokers the increase in whole blood
cadmium due to oyster consumption
was only 1.2 ng/ml for Category IV.
Whole blood selenium concentration
also was higher in Category IV subjects
but their serum zinc and copper con-
centrations were unaffected. The con-
centrations of cadmium, zinc and B2-
microglobulin in the urine were
unaffected by oyster consumption;
there was no indication of glycosuria or
proteinuria that could have been at-
tributed to a high intake of cadmium.
Hair cadmium, zinc and copper also ap-
peared to be unaffected by oyster con-
sumption. There were no indications of
any medical problems that could have
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been attributed to a high cadmium in-
take; although the blood pressure of
Category III and especially Category IV
subjects was relatively higher than that
for Categories I and II and they also had
a greater body size.
This Project Summary was devel-
oped by EPA's Health Effects Research
Laboratory, Research Triangle Park, NC,
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
During recent years there has been a
keen interest among researchers and
public health administrators in the toxi-
city of cadmium, with particular refer-
ence to the possible increase of cad-
mium intake due to increased use of
sewage sludge for soil treatment. The
risk of an actual increase in the cad-
mium intake has been well documented
and a major remaining question is
whether such an increase is likely to
lead to any health effects.
So far, only in Japan have population
groups with exceedingly high cadmium
intakes via food been found. In the high
cadmium intake groups in Japan, the
prevalence of cadmium-induced
proteinuria might be as high as 50% or
more. Some studies in Japan demon-
strate clear dose-response relationships
and these data have been used to
analyse the dose-response at relatively
low dose levels. Calculations have been
supported by metabolic models which
involve a number of assumptions, and
therefore uniform agreement on the
health hazards involved with slight in-
creases of average cadmium intake has
not been reached.
Preliminary data from New Zealand
indicated that the oysters had such high
cadmium levels that a small subgroup
of the population who consumed a
large number of oysters annually, could
have cadmium intakes as high as the
affected populations in Japan. The
present study endeavoured to docu-
ment oyster intake in the group with the
alleged high oyster consumption, their
cadmium intake and also their cadmium
concentrations in various biological me-
dia such as blood, urine and hair. As the
oysters had relatively high levels of se-
lenium, zinc, copper and manganese,
these trace elements were also ana-
lyzed in most of the biological materials
collected.
This New Zealand cadmium-exposed
group is the only one found outside
Japan with such high cadmium intake
via food, and it is envisaged that further
studies of this group will give valuable
data for the explanation of the
metabolism as well as the toxic mecha-
nism of cadmium.
The aim of this study was to confirm
the high dietary intakes of cadmium and
other trace elements from oysters in a
population associated with the oyster-
ing industry, and to determine (i) the
impact of those high intakes on cad-
mium concentrations in accessible tis-
sues of the study subjects and (ii)the
occurrence of health effects in the popu-
lation resulting from their dietary expo-
sure to cadmium.
This project covered an initial 18-
month period of which the specific aims
were the following:
(a) to develop methods for cadmium
analysis in the tissues studied.
(b) to evaluate the cadmium content of
various shellfish in New Zealand
and the daily cadmium intake in
groups with a high shellfish con-
sumption.
(c) to measure the individual and
group-average daily cadmium in-
take of workers in a New Zealand
oyster industry.
(d) to measure the interrelationship of
cadmium concentrations (and of
other trace metals) in serum, blood,
urine and hair in the group with a
high cadmium intake from oysters
and to measure the effect of sea-
sonal variations on the cadmium in-
take and tissue concentrations.
(e) to measure the occurrence of tubu-
lar proteinuria in the group with a
high cadmium intake.
Procedure
About 70 male and female workers
are employed in the oyster canning in-
dustry and 50 male fishermen are in-
volved full time in the fishing during the
season from March to August. In addi-
tion, there are 50 retired workers from
this industry still living in the same area.
Meetings were held with the oyster
fishermen and canning workers in the
fishing port of Bluff before the season
started in 1981, and everyone was en-
couraged to take part in the study. As
the study involved the collection of
faeces, urine, blood and hair samples as
well as keeping dietary records, etc., it
was not expected that everyone would
be willing to participate.
The aim was to find a same-sized ref-
erence group of meat industry slaugh-
termen with a low oyster intake, but it
turned out that many of these workers
in the area also had a high oyster intake,
and furthermore, it was even more diffi-
cult to convince them to take part as
they had no personal involvement with
the oyster industry.
A number of people were found in
Bluff and in small communities adjacent
to Bluff with a low oyster intake but with
similar living conditions, etc., to the oys-
ter fishermen; these people were in-
cluded in the group as a reference. All in
all, 76 people were selected and they
were classified according to average
oyster consumption during the season
into 4 groups. All these people lived in
the Bluff or Invercargill areas. An addi-
tional reference group for the Study of
blood cadmium and urine cadmium
was found in the city of Dunedin.
Samples were collected at two times,
and for a subgroup of 18 people at three
times. The first samples of faeces, urine,
blood and hair were collected in the
week before the season started on
March 1, 1981. However the equipment
on the oyster fishing boats is checked in
the presence of a Ministry of Agriculture
and Fisheries Inspector in the few days
preceeding the opening of the season.
Since the oysters reputedly taste better
at the beginning of the season some
fishermen had already eaten a few oys-
ters in that week preceeding the official
opening of the season, and their faecal
output of cadmium reflected that intake.
In the middle of the season in July 1981
additional samples of blood and a faecal
specimen were collected from 18 peo-
ple who were keen to cooperate; they
also kept a daily diary of oyster intake
from then until the next sampling. Fi-
nally, at the end of the season in August
1981 a full set of faeces, urine, blood
and hair samples were collected again,
as well as an interview to obtain a di-
etary history and a medical history.
With this design of the study, we
could evaluate the relationship between
oyster intake and cadmium intake on a
quantitative basis and we could study
its time relationship, because at the be-
ginning of the season the intake was
likely to be less than in the middle or the
end of the season. The group studied
covered the age range 20-75 years and it
included 57 men and 19 women. Since
we were describing mainly the short-
term relationship between cadmium in-
take and cadmium in tissues it was con-
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sidered that any age effect on the
cadmium concentration in tissues was
not likely to cause bias in the results.
In order to evaluate the possible ef-
fects of cadmium, urinary beta-2-
microglobulin as well as total protein-
uria and glycosuria were measured,
blood pressure was measured and the
medical history was recorded in an in-
terview.
Faeces were analyzed for cadmium,
zinc, copper, and manganese. Urine
was analyzed for pH, specific gravity,
cadmium, zinc, creatinine, urea, glu-
cose, protein, and beta-2-microglobulin.
Blood was analyzed for packed cell vol-
ume, hemoglobin, cadmium, selenium,
zinc, copper, and beta-2-microglobulin.
Hair was analyzed for cadmium, zinc,
and copper. Dietary history was evalu-
ated for energy, protein, calcium, zinc,
and iron.
Results and Conclusions
Methods for the estimation of cad-
mium in blood, urine and hair have
been established , and to date appear to
be reasonably accurate and reliable.
Further inter-laboratory comparisons
will be carried out.
Bluff oysters have a high cadmium
content; although all species of oysters
have a relatively high cadmium content
compared to most other foodstuffs, dif-
ferent species show large differences in
concentrations of cadmium as well as
other trace elements. This is of great in-
terest because a high consumption of
different shellfish might reveal differ-
ences in cadmium metabolism due to
interactions among the elements.
Intakes of cadmium in the population
studies were high. Analysis of faeces
confirmed the high intakes of cadmium
based on analyses of cadmium concen-
tration in oysters and estimates of daily
consumption. There was a close agree-
ment between the observed content of
cadmium, zinc and copper in faeces and
estimated output. Some of the subjects
with the highest oyster consumption
had daily cadmium intakes greater than
500 \j.g, which are higher intakes than
those shown to be associated with a
high incidence of renal tubular damage
in people exposed to contaminated rice
in Japan. The New Zealand oyster con-
sumers also had intakes of zinc greater
than twice the normal New Zealand in-
take, and intakes of selenium about
twice a normal New Zealand intake. The
limited data available indicate that the
Japanese people with a high cadmium
exposure also had intakes of zinc and
selenium similar to those of the oyster
consumers.
In spite of the very high intake of cad-
mium from oysters the concentration of
cadmium in whole blood was not in-
creased greatly in proportion to the in-
creased intake. The data clearly show
increased blood cadmium concentra-
tions due to smoking in the four groups
with different levels of oyster consump-
tion. Among non-smokers the increase
in blood cadmium due to oyster con-
sumption was only 1.2 ng/ml. There was
a good correlation between blood cad-
mium concentration and oyster intake
at the beginning as well as at the end of
the oyster season. There were no ob-
served changes during the season or
between groups in urinary cadmium
output or in hair cadmium concentra-
tion. There was a close correlation be-
tween blood cadmium and blood sele-
nium concentration, whereas neither
serum zinc nor serum copper concen-
tration increased with an increasing
blood cadmium concentration. There
were no differences in hair zinc or cop-
per concentration.
The dipstick proteinuria and glyco-
suria tests did not show any indication
of cadmium-induced renal damage. The
frequency distribution of urinary beta-
2-microglobulin concentration was sim-
ilar to "control groups" from other epi-
demiological studies, and none of the
participants had a beta-2-microglobulin
concentration higher than 250 (j.g/1 (ad-
justed to specific gravity 1.025).
There was a tendency for higher
blood pressures than expected in the
groups with the highest oyster intakes.
This tendency was influenced by smok-
ing habits but an effect of cadmium on
blood pressure could not be ruled out.
Finally, the present study showed that
the cadmium in Bluff oysters does not
appear to be absorbed to the extent that
is considered normal for other foods.
The mechanism for this diminished ab-
sorption could be interactions with sele-
nium and/or other trace elements, but
could also be unusual chemical specia-
tion in oysters compared to other food-
stuffs. It could also be that cadmium
from oysters is metabolised differently
from cadmium from other foods after it
has been absorbed.
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Joan McKenzie and Ram Sharma are with University of Otago, Dunedin, New
Zealand; and Tord Kjellstrom is with University of Auckland, Auckland, New
Zealand.
Normal Kowal is the EPA Project Officer (see below).
The complete report, entitled "Cadmium Intake Via Oysters and Health Effects in
New Zealand: Cadmium Intake, Metabolism and Effects in People with a High
Intake of Oysters in New Zealand," (Order No. PB 86-219 144/AS; Cost:
$16.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S1-86/004
0000329 PS
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