IN THE

 A Toxicological and Epidemiological Appraisal
            Stockholm, April 1971


INTRODUCTION                                      1-1



  2.1  DITHIZONE METHODS                          2-2


  2.3  NEUTRON ACTIVATION                         2-4


  2.5  CONCLUSIONS                                2-7



       EXPOSURE                                   3-1

    3.1.1  Cadmium in air                         3-2

    3.1.2  Cadmium in water                       3-5

    3.1.3  Cadmium in soil                        3-6

    3.1.4  Cadmium in food                        3-7

    3.1.5  Cadmium in cigarettes                  3-8

  3.2  DAILY INTAKE OF CADMIUM                    3-10

  3.3  CONCLUSIONS                                3-11



  4.1  UPTAKE AND ABSORPTION!                      4-1

    4.1.1  Respiratory deposition, clearance
           and absorption                         4-1  Respiratory deposition             4-1  Respiratory clearance              4-2  Respiratory absorption             4-3  Conclusions                        4-7

    4.1.2  Gastrointestinal absorption            4-0  In animals                         4-8  Single exposure                4-8  Repeated exposure              4-9  Influence of dietary factors
                   upon absorption of cadmium     4-10

   Calcium                    4-10

   Vitamin D                  4-10

   Protein                    4-11  In human beings                    4-11  Conclusions                        4-13

    4.1.3  Placental transfer                     4-14  In animals  .                       4-14  In human beings                    4-15  Conclusions                        4-15

     OF CADMIUM  IN ANIMALS                      4-16

  4.2.1  Uptake  to and clearance from blood     4-16   Fate of cadmium in blood after
             single injection                   4-16   First hours after injection    4-16   First weeks after injection    4-19   Fate of cadmium in blood after
             repeated injections                4-19

  4.2.2  Tissue  distribution and retention      4-21   Single exposure                    4-21   Repeated exposure                  4-24

  4.2.3  Distribution within organs             4-76   Single exposure                    4-26   Repeated exposure                  4-20

  4.2.4  Excretion                              4-70   Urinary excretion                  4-20   Excretion via the alimentary
             tract                              4-30   Excretion via hair                 4-32

  4.2.5  Biological half-life                   4-33

  4.2.6  Cadmium metabolism in relation to
         zinc metabolism                        4-35

  4.2.7  Influence of other compounds on the
         metabolism of cadmium                  4-37

  4.2.8  Discussion of mechanisms for trans-
         port, distribution and excretion       4-30

       BEINGS                                     4-41

    4.3.1  Transport and distribution in blood    4-41

    4.3.2  In organs                              4-44  In liver and kidney                4-44  Other organs                       4-48

    4.3.3  Excretion                              4-49  Urinary excretion                  4-49  Fecal excretion                    4-52  Excretion via hair                 4-52

    4.3.4  Total body burden and renal burden     4-54


    4.4.1  Relationship between concentrations
           of cadmium in blood ana organs         4-59  In animals                         4-59  In human beings                    4-60

    4.4.2  Relationship between concentrations
           o^ cadmium in urine and organ or
           blood concentrations                   4-60  In animals                         4-60  In human beings                    4-61

    4.4.3  Conclusions                            4-63


    4.5.1  In animals                             4-63

    4.5.2  In human  beings                        4-65





       RELATIONSHIPS                              5-1

       RELATIONSHIPS                              5-5

    5.2.1  In human beings                        5-5  Industrial exposure                5-5  Respiratory effects reported -
                   exposure to caomiurn dust       5-5  Respiratory effects reported -
                   exposure to cadmium oxide
                   fume                           5-7  Respiratory effects not
                   reported                       5-9  Ambient air exposure               5-11  Prognosis                          5-13

    5.2.2  In animals                             5-14

  5.3  CONCLUSIONS                                5-15


SHIPS                                             6-1

       RELATIONSHIPS                              6-1

    6.1.1  Acute effects and dose-response
           relationships                          6-1  In human beings                    6-1  In animals                         6-2  Influence of chelating agents      6-3

  6.1.2  Chronic effects and dose-response
         relationships                          6-5  In human beings                    6-5  Proteinuria and renal
                 function                       6-5  Nature of proteinuria          6-8  Renal stones                   6-10  Autopsy and biopsy findings    6-11  In animals                         6-13  Mechanisms for the development
             of the renal injury                6-17  Dose-response relationships        6-19

      6,  Evaluations starting from
                 data on exposure in the en-
                 vironment                      6-20  Evaluations starting from
                 data on cadmium concentra-
                 tions in blood and urine       6-20  Evaluations starting from
                 data on cadmium concentra-
                 tions in the kidneys           6-21  Estimations of how much long-
                 term exposure is required to
                 cause the human cortex to
                 reach concentrations of 200
                 ppm (wet weight)               6-22

     DOSE-RESPONSE RELATIONSHIPS                6-24

  6.2.1  Acute effects and dose-response
         relationships                          6-24

  6.2.2  Chronic effects and dose-response
         relationships             .             6-24  In human beings                    6-24  In animals                         6-25

  6.2.3  Dose-response relationships            6-27


  6.3.1  Acute effects ancl dose-response
         relationships                          6-27

  6.3.2  Chronic effects and dose-response
         relationships                          6-28  In human beings                    6-28  In exposed workers             6-28  In the general population      6-2H  In animals                         6-31
  6.3.3  Discussion and conclusions             6-34

     RELATIONSHIPS                              6-36

  6.4.1  In human beings                        6-36

  6.4.2  In animals                             6-38

  6.4.3  Discussion and conclusions             6-39

     RELATIONSHIPS                              6-41

  6.5.1  Acute effects and dose-response
         relationships                          6-41

  6.5.2  Chronic effects and dose-response
         relationships                          6-43  In human beings                    6-43  In animals                         6-43  Dose-response relationships        6-45

     RELATIONSHIPS                              6-45

  6.6.1  Acute effects in animals               6-46

                                                           Vlll  Events in cadmium induced
               testicular necrosis                6-46  Sensitivity of different animals
               to testicular necrosis and doses
               applied                            6-47  Mode of administration             5-49  Mechanisms for testicular
               necrosis                           6-41  Protective measures                6-50

    6.6.2  Chronic effects                        6-52  In animals                         6-5?  In human beings                    6-54

    6.6.3  Dose-response relationships            6-54

  6.7  OTHER EFFECTS                              6-55

    6.7.1  In human beings                        6-55

  6.8  CONCLUSIONS                                6-59



  7.1  CARCINOGENIC EFFECTS                       7-1

    7.1.1  In animals                             7-1

    7.1.2  In human beings                        7-2

  7.2  GENETIC EFFECTS                            7-6

  7.3  CONCLUSIONS                                7-7



  8.1  INTRODUCTION                               8-1

8.2  CLINICAL FEATURES                          8-2

  8.2.1  Symptoms and signs                     8-2

  8.2.2  Laboratory examinations                8-3  Blood findings                     8-3  Urinary findings and renal
             funtion tests                      8-3

  8.2.3  Histo-pathological changes             8-4  Kidneys                            8-5

    8..2.3.2  Bone                               8-5

8.3  DIAGNOSIS   .                               8-5

8.4  EPIDEMIOLOGY                               8-8

  8.4.1  Epidemiological studies in Toyama
         Prefecture                             8-8  1962-1965 Epidemiological
             research                           8-8  1967 Epidemiological research      8-9   Groups studied  and selection
                 of subjects for final dia-
                 gnostic procedure              8-9   Final diagnostic examina-
                 tion (Third examination)        8-9  Total number of cases of  Itai-
             itai disease                       8-10  Age and sex                        8-10  Frequency of new cases of Itai-
             itai disease                       8-11  Geographical distribution of
             Itai-itai patients                  8-11

-------  Prevalence of proteinuria and
               glucosuria                         8-12  Hereditary and dietary factors     8-',3  Hereditary factors             8-13  Dietary factors                fl-14  Profession and other factors       8-15 Concentrations of heavy metals
               in urine                           3-16 Concentrations of cadmium in
               organs                             fl-16 Concentrations of heavy metals
               in the environment                 8-17

    8.4.2  Other areas in Japan under survey for
           Itai-itai disease                      8-19  Sasu and Shiine basins, Tsushima
               Island, Nagasaki Prefecture        8-20

        8.4.2,1.1  Medical examinations           8-20

        8.4.2,1.2  Cadmium exposure               8-24  Other areas under observation      6-25

  8.5  ETIOLOGY                                   8-26

    8.5.1  Vitamin D deficiency                   8-26

    8.5.2  Malabsorption syndrome                 8-27

    8.5.3  So-called Vitamin D resistant osteo-
           malacia (renal osteomalacia)           8-28

    8.5.4  Cadmium as an etiological factor       8-28

  8.6  CONCLUSIONS                                8-31


NEED FOR FURTHER RESEARCH                         9-1

REFERENCES                                        R~l

                       CHAPTER  1

This review on cadmium in the environment has been performec
under a contract between the U.S. Environmental Protection
Agency and the Department of Environmental Hygiene of the
Karolinska Institute, Sweden. The Project Officer of the Air
Pollution Control Office of the U.S.  Environmental Protection
Agency has been Robert J. M. Norton,  M.D.

The focus of the report is upon information essential to the
understanding of the toxic action of  cadmium and the relation-
ship between dose (exposure) and effects on human beings and
animals. The therapy of cadmium poisoning has not been discussed

The report is intended to serve as  a  background paper for a
future Air Quality Criteria document  on cadmium. Therefore,
particular attention has been given to information relevant
for the evaluation of risks due to  long-term exposure to low
concentrations of cadmium. Acute effects from short-term expo-
sure to high concentrations are dealt with briefly. In vitrc
studies without bearing on the main problem have not been dealt

The report is not limited to effects  from exposure via in-
halation. Newly accessible information, showing that large popu-
lations may be exposed consideraoly via the oral route,  can
elucidate chronic effects of cadmium in general. Man and animals
can be victims of secondary exposure  through vehicles such as
food and water which have been contaminated by cadmium in air.

Cadmium is in the air as an aerosol. Hitherto only inorganic
cadmium compounds have been found in nature and there are no
data available on the toxicity of organic compounds. This re-
view deals only with inorganic cadmium compounds.

Although data presented are based mainly on a literature survey
and on our own experience, we wish to express our deep appre-
ciation for the additional information made available to us
through correspondence with and personal visits to scientists
in several countries. Most of the information from Japan would
not have been possible to evaluate and include in this report,
had we not had the advantage of a most generous collaboration
with the Japanese Ministry of Health and Welfare, the Prefectural
Departments of Public Health in Toyama, Nagasaki and Gumma, the
Japanese Association of Public Health, industries, particularly
the Kamioka Mine of the Mitsui Mining and Smelting Company, as
well as independent researchers in Japan. We wish to express our
gratitude especially to Drs. Michio Hashimoto, M.D. and Yoshima
Yamamoto, M.D., former and present chiefs, respectively, of
Environmental Pollution Control Section, Bureau of Environmental
Sanitation, Ministry of Health and Welfare, and to Kenzaburo
Tsuchiya, M.D., Professor of Preventive Medicine and Public Health,
School of Medicine, Keio University, Tokyo, Japan.

We express our thanks to Miss Pamela Boston for assistance in
editing the English of the report.  Part of the expense for a
visit to Japan was provided by the Swedish National Environ-
mental Protection Board, the assistance of which is acknowledged.

                           CHAPTER 2

                     PROBLEMS OF ANALYSIS
Biological effects of cadmium cannot be discussed without
taking into account the analytical methods used. When con-
centrations of cadmium in air,  water, food, body fluids and
organs are compared to each other or related to effects, one
must be sure that a proper method is being used for the deter-
mination of cadmium, otherwise  erroneous conclusions may be

The following properties of an  analytical method are of in-
terest :

1)  Specificity;   The method used must measure only cadmium.
If other substances interfere,  they must be either eliminated
or a correction must be made allowing for their presence.

2)  Sensitivity;  The minimum amount or concentration that the
method will detect.

3)  Precision; The error of the method, often expressed as the
coefficient of variation, is evaluated by a number of analyses
on the same sample over a certain period of time. Precision is
often dependent on the concentration.

4)  Repeatability; By running duplicates of the samples and ay
having the deviation of the two values from  their mean
       expressed  as a percentage repeatability is obtained.

5)  Accuracy;   This means the systematic deviation from the
true values.

Many methods have been used for the determination of cadmium,
but during the last two decades four methods have been domi-
nating, and as it is expected that all four will be used for
many years to come, they are being discussed here. These me-
thods are:  1) Colorimetric determination after wet digestion
and extraction with dithizone (Dithizone methods); 2) Emission
spectroscopy;   3) Neutron activation and 4) Atomic absorption
spectrophotometry. These methods have recently been discussed
also by Yamagata and Shigematsu, 1970.


The basic principle is that cadmium forms a stable complex
with dithizone at an alkaline pH.       The many other metals,
that form complexes with dithizone           must first be eli-
minated. Examples of dithizone methods which have been used
for the determination of cadmium are the ones by Church, 1947,
Saltzman, 1953 and by Smith, Kench and Lane, 1955. With regard
to precision etc., there is scarce information in the literature.
If proper steps are taken to remove other metals, the method
must be regarded as being specific, but, on the other hand, there
is always a risk of contamination with cadmium from reagents
during all the steps. If blanks and standards are treated exactly
in the same way as the samples, this error will be eliminated.

Dithizone'methods have been used for the determination of cadmium
in urine, where normally only a few micrograms per liter are found,
and for the determination of cadmium in food stuffs and organs.
The results obtained by this method seem to compare favorably
with results obtained by other methods. (See table 2:1). In the
following chapters, the dithizone method will be regarded as a
useful method for determination of cadmium in biological material.


The basic principle is that by exciting metal atoms by high
energy sparks or electric arcs, the atoms will emit light of
a characteristic spectral distribution. The spectral lines may
be recorded on a film, which makes it possible to get a quali-
tative or quantitative estimate of the metals. Tipton et al.,
1962, studied the precision for determinations in organs and
found that the coefficient of variation was 19 percent at con-
centrations of 220-3,400 ppm cadmium in the ash. The repeat-
ability varied between 5 and 7 percent for liver and kidney.
The sensitivity was 50 ppm cadmium in ash.

Geldmacher-v. Mallinckrodt and Pooth, 1969, have also used a
spectroscopic method for the determination of metals, including
cadmium, in biological material. After wet ashing, the metals
were extracted with diethylammonium-diethyldithiocarbamate in
chloroform and after removal of the solvent the analysis was
performed.  They stated that they could detect 1 yug of cadmium,
but made no further studies on the method. Imbus et al., 1963,
determined cadmium in urine and blood after extraction with
dit&izone. The lower limit of sensitivity was 0.1 yug per sample
and by using 25 ml of blood or 250 ml of urine, about 0.4 jag
could be detected in 100 ml and 1,000 ml respectively.

The sensitivity has been improved during recent years and at
present 0.02 JLig can be detected in samples with modern equipment,
that is, that it is possible to determine 0.2 jug per 100 ml
blood, by using 10 ml samples.
It seems that some earlier spectrographic methods have had/re-
latively low sensitivity and that accurate quantitative deter-
minations of cadmium could only have been obtained in organs


with relatively large concentrations, such as liver and kidneys.


The basic principle is that by irradiation of the sample with
elementary particles, chiefly neutrons, radioactive nuclides
will be obtained. Elements can be identified with the aid of
their energies and half-lives. It is often necessary to intro-
duce separation steps by chemical methods. This is a method
which should be quite specific for cadmium, but until now neutron
activation has only been used in a few investigations on cad-
mium and the number of determinations has been small (Westermar*.
and Sjostrand, 1960, Axelsson and Piscator, 1966a, Piscator and
Axelsson, 1970, Plantin, 1964, Lieberman and Kramer, 1970, Westsr,
1965, Henke, Sachs and Bonn, 1970).


The basic principle is that the sample is passed  into a high
temperature burner, so that the excited atoms will pass tbtrough
a path of light emitted from a lamp with a cathode of a specific
metal. If the  sample contains the actual metal, the atoms from
that metal will absorb the light and the absorbance can be read
on a meter.

At present, atomic absorption is the most commonly used method
for the determination of cadmium. The sensitivity is high and
concentrations as low as 0.005 ppm can be determined in pure wa-
ter solutions. There has been a lot of optimism about atomic
absorption, but the difficulties have often been  overlooked.
Pulido, Fuwa and Vallee, 1966, have thoroughly discussed the
determination  of cadmium in biological material.  They studied
interference by other substances and found that phosphate in

concentrations above 0.1 M could decrease the absorbance and
that sodium chloride  in concentrations above 0.01 M could in-
crease absorbance. By using a hydrogen lamp, they could allow
for the presence of NaCl in serum and urine and obtain more
true values. The specificity of cadmium determinations with
atomic absorption is thus dependent on the amount of i\aCl and
other compounds in the sample, but still cadmium in urine and
serum has been determined in several investigations without
taking the presence of NaCl into account. It should be pointed
out that Pulido, Fuwa and Vallee, 1966, found in tan normal
urines, a mean value of 0.009 ^ig per ml urine, which is highar
than that reported when/extraction methods have been used
(see section 4.3.3). It is possible that there are factors
hitherto not investigated that might influence the determination
of cadmium in, for example, normal urine. Pulido, Fuwa and Vallee,
1961, used a special apparatus giving a very high sensitivity,
but with commercially available apparatus, it will not be poss-
ible to determine cadmium in urine without a preliminary con-
centration of cadmium.

If interfering substances are not present, the accuracy is
very high. Pulido, Fuwa and Vallee, 1965, reported on two
samples with a concentration of 0.165 and 0.051 ppm of cadmium
(National Bureau of Standards' sample) where they found an
accuracy of 99.4 and 104.5 percent. Repeatability was 2 percent
when nine duplicate! analyses of cadmium in metallothionein we're
done. When atomic absorption was compared with emission spectro-
graphy, values were obtained from 95-113 percent of those ob-
tained with the latter method.

The difficulties encountered when investigating cadmium in
biological materials at a low concentration of cadmium are net
found to the same degree when analyzing tissues with a high

cadmium content such as kidney add liver.  Repeatability was
3.2 percent for determination of cadmium in liver and kidneys
as reported by Morgan, 1969, and similar values were found
by Piscator for cadmium in renal cortex (unpublished data).

During recent years, it has been recognized that it might
be necessary to extract the metals into an organic solvent
before analysis.  This will give a higher concentration, and
interfering salts will be eliminated. One method is to digest
the sample with acid, adjust the pH to around 3 and extract it
with a chelating agent such as ammoniumpyrrolidine dithiocarba-
mate (APDC) in methylisobutylketone (MIBK). Such a method for
the determination of cadmium in urine and serum has been de-
scribed by Lehnert, Schaller and Haas, 1968.

In a Japanese report (Japanese Public Health Association,
1970 c) it is seen  that most laboratories used first an ex-
traction with dithizone of the digested sample and then once
again extracted cadmium with acid before determination with
atomic absorption was done. Table 2:1 shows the results from
analyses in 6 different laboratories of urines from cadmium
exposed workers and patients         with Itai-itai disease.
There is a good agreement between most of the laboratories.

The latest improvement in cadmium determination is the flame-
less atomic absorption in a graphite atomizer, which makes  it
possible to determine about 0.01 ng in 20 yul of urine, accord-
ing to preliminary  results, provided that a deuterium back-
ground corrector is used (Linnman and Lind, unpublished data).


There are several methods that can be used for the determina-
tion of cadmium in biological material, such as blood, urine,
organs and food.  At present, the most commonly used method
is atomic absorption spectrophotometry, but interference from
salts, such as NaCl, may give erroneous results especially when
low concentrations are determined. Such interference may be
avoided by using extraction technics or background correctors.

Except for one Japanese investigation, no collaborative study
has been performed by laboratories engaged in research on b io-
logical effects of cadmium. Such a study is necessary as this
would facilitate comparisons in the future of parameters such
as cadmium in food, cadmium in urine or blood.

           (From Japanese Public Health Association, 1970c).




.0 12
.0 12
.8 8
.0 14
— - — " —
b a
.7 19.
.4 23.
.4 12.
.9 12.
.6 28.
.7 178.
.1 64.
.3 143.
.5 63.
.9 47.
.4 7.
.8 141.
.1 17.

4 14.6
0 18.6
3 9.3
1 9.3
3 24.8
0 154.8
8 51.6
6 123.3
1 53.2
1 35.5
8 4.5
9 108.4
6 12.9

147.4 1
11.6 1
11 .8







methods were used:
: Dit
: Dit
: Dit
: Di I
: Uit
: D i \
^ I zone
h j.^une
hi zune
!> i . fne
: APDC-i-iBK
- atomic

extraction (without
- atomic
- atomic
- atomic
- atomic

absorpt ion
absorpt ion


Elmer apparatus

atomic ab



                          CHAPTER 3

Cadmium is closely related to zinc and will be found wherever
zinc is found in nature. The cadmium to zinc ratios will vary.
In most minerals and soils ratios of 1:100-1:12,000 have been
found (Bowen, 1966, and Schroeder et al.,  1967). Zinc is an
essential metal for most life-forms  (Underwood, 1GG2,
Bowen,  1966,  Schroeder, 1967 and Yamagata  and Shigematsu,  19700.
Thus it is probable that no naturally occurring material will be
completely free from cadmium.

Cadmium is obtained as a by-product in the refining of zinc and
other metals. However, as it is difficult  to separate zinc and
cadmium,  the latter will often be found in small amounts in com-
mercially available zinc compounds, as pointed out by Schroeder
et al., 1967.

Though  cadmium has been recognized for only a relatively short
period  of time, copper, lead, zinc and some other metals have
been used for several thousand years. Thus, as soon as man
started to produce metals,  he also started to pollute the
environment with cadmium. In this century  cadmium and cadmium
compounds have been used increasingly by industries, causing

a sharp increase in environmental contamination. Cadmium will
be emitted to air and water by mines, by metal smelters,
especially lead, copper and zinc smelters and by industries
using cadmium in alkaline accumulators, alloys, paints, and
plastics. The burning of oil and waste in scrap metal treatment
will also contribute. The use in agriculture of fertilizers,
either as chemicals or as sludge from sewage plants and the use
of cadmium-containing pesticides might also contribute to the

Some, of the cadmium emitted to the air will be inhaled by people
bnd animals/'but most of it will be deposited in soil or water.
The cadmium deposited in water may then increase the concentra-
tions of cadmium in edible water organisms. In the event
of flooding or  irrigation, cadmium in water might also
increase the concentrations in soil, in turn causing an
increase of cadmium in agricultural products, such as rice
and wheat. However, very little is known about the transfer
of cadmium from deposits in soil or water to microorganisms
or plants and very little is known about the forms in which
cadmium exists. It has been suspected that organic cadmium
compounds could exist similar to the ones described for
mercury, but it has not been possible to prove the existence
of such compounds (Westermark, personal communication).

3.1.1  Cadmium  in air
During the last decades, yearly determinations of cadmium in
air have been performed in several areas in the United States
(Air Quality Data, 1966). Since the analytical methods were
not always sensitive enough, some cities in the U.S. have been
recorded as having zero levels of cadmium in air. The highest
yearly mean concentrations in 1964 were found in Covington,
Kentucky, where an average level of 0.05 /ug/m  was recorded.
The highest quarterly average level in the 3rd quarter in 1964,

also found in Covington, Kentucky, was p .H/jg/m  .  Kneip et al.,
1970, made daily determinations for one year at several sites
in New York City and surrounding areas. They found that lower
Manhattan had a yearly mean level of 0.023 /jg/m , whereas a
non-urban site had 0.003 /Jg/m . In Sweden weekly means of 0.3
jjg/m  were recorded on several occasions 500 meters -from a
factory using copper cadmium alloys. At a distance of  100
meters from the source, a monthly mean value of 0.6 yug/m  was
recorded. The highest concentration found in a  24-hour sampling
was 5.4 ug/m . In the center of Stockholm, weekly means of 0.005
      were found, whereas in a rural area far from cadmium-emitt-
ing factories, a monthly mean of 0.0009 /u/m  was found  (Piscator,
unpublished data). In Erlangen, West Germany, Essing et al.,
1969, found a level of 0.0015 /Jg/m  (sampling time not  stated).
In Japan weekly means of 0.5 jug/m  (based on 8-hour sampling
periods) have been reported at a distance of 100 meters from
a zinc smelter. At a distance of 400 meters, the mean levels
recorded were 0.2 *jg/m  (Hasegawa, Ministry of Health and Wel-
fare, personal communication). Near another smelter, 8-hour
values of 0.16-0.32 /ug/m  were obtained at a distance of 500
meters from the source (Kitamura, personal communication).
It thus seems that in areas around cadmium-emitting factories,
cadmium concentrations in air several hundred times greater than
those in non-contaminated areas will be found.

Monthly deposition of cadmium has been measured around some
factories. The results from the years 1968-1970 at locations
near a Swedish factory are shown in table 3:1 (Olofsson, 1970).
It should be noted that a considerable deposition was sometimes
even found at 10 kilometers from the source. Deposition measure-
ments near a Japanese factory during a period of six months
showed a mean value of 6.2 mg/m /month at a distance of 500 meters
from the source and a mean value of 1.8 mg/m /month at a dis-

tance of 1,400 meters, whereas in two control; areas in two
cities; values of 0.1 and 0.4 mp,/m /month, respectively, were
found (Kitamura, personal communication). In the United States,
Hunt et al., 1970, determined cadmium in  dustfall in residential,
commercial and industrial areas in 77 cities and found montnly
means of 0.040, 0.063 and 0.075 mg/m  in  the respective areas.

Deposited cadmium has been measured by determining cadmium in
mosses (Ruhling,  1969, Ruhling and Tyler, 1970 and Olofssor.,
1970). Figure  3:1 shows  how the spreading of cadmium around
a factory producing  copper cadmium alloys can be determined
by this technique. According  to Ruhling and Tyler, concentra-
tions of cad?um in moss  in the more heavily industrialized and
more densely populated south  of Sweden were between 0.5-1
ppm  (dry weight) whereas  in the north, they were less  than 0.2
ppm. The spread of cadmium from a cadmium-emitting factory can
also be studied by determining cadmium in leaves from shrubs,
as shown in figure 3:2.  These data are from an investigation
by Kobayashi et al. ,  1969, (quoted by Yamagata and Shigematsu,
1970) .

The  influence  of  cadmium emissions upon cadmium  concentrations
in soil has been  studied by Kitamura  (personal communication).
Test pots containing soil were placed 500 meters from the e-
mission source and in a  control area. The results are shown in
table 3:2. Within a  few  years, a  ten-fold increase in the
cadmium concentration occurred in the soil placed near the
emission source.  At  that same location, deposited cadmium was
measured as 6.2 mg/m /month during a  six-month period.

It is important to know  the state in  which cadmium exists in
air, but at present,  no  data  concerning this question are
available. Even if it can be  presumed that cadmium oxides will

constitute a large part of the airborne cadmium,  the possibil-
ity that other compounds are formed can not be excluded. Par-
ticle size is also essential for calculating deposition and
absorption in the lungs, but only one  report has  supplied such
information. In Cincinnati, Ohio, cadmium  concentrations in
the air and mass median diameters of the particles were mea-
sured downtown and in a suburb (Lee, Patterson and Wagman,
1968). Concentrations averaged 0.08 and 0.02/ug/m , respect-
ively and FIND averaged 3.1 and 10 microns,  respectively. In
both areas about 40 percent of the particles were below 2 mi-
crons .

3.1.2  Cadmium in water
In areas not known to be polluted by cadmium, values of less
than 1 ppb have been reported in water. Values exceeding 10
ppb have been recorded both in natural waters and in water for
consumption. Increased amounts of cadmium  can be  due to the
contamination of the water either by industrial discharges or by
the metal or plastic pipes used in distribution (Schroeder et
al., 1967).

Yamagata and Shigematsu, 1970, have pointed out that in rivers
polluted by cadmium,the metal will often be undetectable in the
w'ater phase while large concentrations will be found in suspended
particles and in the bottom sediments. This is especially true
at neutral or alkaline pH. A similar finding was  obtained in
Sweden, where 500 meters downstream from a  cadmium-emitting factory
4 ppb of cadmium were found in water, while 80 ppfn (dry weight)
were found in the mud (Piscator,  unpublished data). To avoid
errors when determining the degree of contamination in water,
cadmium in the suspended particles or the  sediments must be
measured. The contamination of rice fields surrounding the Jintsu
River, the area in Japan where the Itai-itai disease has occurred,
is probably due to the transport of cadmium-containing suspended

particles to the.:paddy soil by irrigation with river water
(Yamagata and Shigematsu,  1970).

3.1.3.  Cadmium  in soil
It has already been mentioned that both airborne and waterborne
cadmium can cause increased concentrations of cadmium in soil.
In areas not known to be polluted, the cadmium concentrations
in soil have been reported to be  less than 1 ppm, with great
variations  (Schroeder et al., 1967and Yamagata and Shigematsu.
1970) . In Japan  levels of  1-50 ppm have been found in rice fields
in areas under observation for suspected contamination from cad-
mium  (Hasegawa,  personal communication, Yamagata and Shigematsu,

There are other  ways by which soil can be contaminated with
cadmium. Od§n (personal communication) has found high concen-
trations of cadmium in sludge from .-sewage treatment plants in
Sweden. The use  of this sludge as fertilizers could increase
cadmium concentrations in  soil. Superphosphate fertilizers
also contain relatively large amounts of cadmium, as pointed
out by Schroeder and Balassa, 1963, and Schroeder et al., 1967.

Information is lacking on what factors determine the uptake
of cadmium by plants and on the extent to which selective
mechanisms will  operate. It is conceivable that such factors
as pH and concentrations of other metals will influence the
uptake. Two important foodstuffs, rice and wheat, are able to
take up considerable quantities of cadmium from soil. Kobayashi
et al., 1969, (qouted by Yamagata and Shigematsu, 1970) added
cadmium oxide to soil in pots where rice and wheat were
growing. The results are shown in table 3:3. It is note-
worthy that wheat grains accumulated more cadmium than rice.
It can also be noted that concentrations above 10 ppm in

soil brought about less yield of both  rice and  wheat.

3.1.4  Cadmium in food
During later years several investigations concerning  the  cenmijm
content of common foodstuffs have been performed  (United  States:
Schroeder et al., 1967; West Germany:  Kropf and Geldmacher  v.
Mallinckrodt, 1968, and Essinp et al., 19G9; Czechoslovakia:
Lener and Bibr,   1970; Roumania: Rautu  and Sporn,  1970; Japan:
Ishizaki, Fukushima and Sakamoto, 1970a). In table  3:4, some
basic foodstuffs are compared. It will be seen that these reports
indicate that "normal" levels of cadmium in food  are  below  0.05
ppm. In the table, only the U.S. values reported  by Schroeder
and Balassa, 1961, have been included. The data by  Schroeder et
al., 1967, have.been excluded because  in the investigation  re-
ported in 1967 atomic absorption spectrophotometry  was used
without any preliminary extraction. For example,  cadmium  levels
in milk were reported to be 0.1-0.4 ppm. Interference from  sod-
ium chloride might have been the cause. In the reports quoted
it will also be   seen that certain foodstuffs may  contain  higher
concentrations of cadmium.

Some seafood, especially shellfish and cuttlefish,  has been re-
ported to contain above 0.05 ppm (Schroeder and Balassa,  1961,
and Schroeder et al., 1967, and Ishizaki, Fukushima and Sakamoto,
1970a). Such concentrations seem to occur in areas  not known to
be polluted while much higher concentrations have been reported
in areas known to be polluted. Ishizaki, Fukushima  and Saka-
moto, 1970a, reported values of 10-110 and 92-420 ppm, wet
weight, in livers of cuttlefish and shellfish (see  also sec-
tion   Pringle et al., 1968,  reported that cadmium
concentrations varied from 0.1-7.8 ppm, wet weight, in oysters
from the east coast of the United States and from 0.2-2.1 ppm

 x/ Schroeder and Balassa 1961,

in oysters  from  the west  coast.  Rice  and wheat  from most parts
of the world contain  less  than  0.1  ppm, but  rice  and wheat  from
contaminated areas  in Japan  have been  shown  to  contain  consid-
erably higher  concentrations,  around  1 ppm (see sections
B.4.1.12  and  It  is  not  always clear  whether  Japa-
nese data on rice and wheat  refer to  wet or  dry weight. However,
this distinction  is of minor importance, as  the difference  will
be only about  10  percent.  Liver and kidney,  such  as from calves
or swine, often  contain  more than  0.05 ppm,  whereas meat usual-
ly contains less  than 0.05  ppm of  cadmium. An exception seems
to be whale meat, as  Ishizaki,  Fukushima and Sakamoto,  1970a,
reported  levels  of  0.25  and  0.4 ppm in two samples.

3.1.5  Cadmium in cigarettes
That smoking might  be a  source  of exposure to cadmium has been
recognized  the last years.  Szadkowski  et al.,  1969, found a mean
content of  1.4 jug per cigarette when  they  determined the cadmium
content of  8 cigarette brands  in West  Germany.  Cigarettes were
smoked in a smoking apparatus  with the following  experimental
parameters: two  puffs a  minute, each  of  two  seconds duration,
suction volume,  30  ml with  a pressure  of 80-120 mm H^O. The
mainstream  smoke  particles  were collected  on a•Cambridge-fiIter
and  the gases  in  nitric  acid.  They found a mean value of 0.15
yug cadmium  per cigarette  in  the particle phase  of the 8 brands
and  0.03  iig in the  gaseous  phase.  From their data it can also
be seen that about  0.5 jug went  into the  side stream smoke,  i.e.,
about 35  percent.

Nandi et  al.,  1969, investigated six  different  brands of ciga-
rettes. The mean  total content  was about  1.2 yug per cigarette.
They also used a  smoking machine,  but  the  experimental  condi-
tions were  not described in  detail. Intermittent  suction was
used 5 seconds every  minute  to  make the  cigarette burn. The
smoke was not  collected  on  filters. Cadmium  was only determined

in the ashes and the filters of the cigarettes. With  the method
used, they found that about 30 percent of cadmium was  recovered
in ash and filter and they calculated that  about 70 percent
passed with the smoke. As they did not separate mainstream  and
side stream smoke, it can not be known how  much cadmium was  in
the mainstream.

Linnman and Lind (to be published) studied  the influence of
different numbers of puffs per cigarette and  different numbers
of puffs per minute in one brand of cigarettes. They  used a
duration of 2 seconds per puff, a suction volume of 35 ml.
They found that one puff per minute and  10  puffs altogether
resulted in a collection of 0.14 tug cadmium per cigarette on
a Cambridge filter. Two puffs per minute and  15 puffs  alto-
gether resulted in 0.19 /ug per cigarette on the filter. The
.same result was obtained with 3 puffs per minute and  15 puffs
altogether. The difference between the first  value and the
second and third ones was statistically  significant.  These
data agree well with the above mentioned findings of  Szadkow-
ski et al., 1969, showing that 0.1-0.2 /jg of  cadmium  might
be inhaled by smoking one cigarette. Smoking  habits will to
some extent affect the amount of cadmium in the mainstreams,
as shown by the influence of puff intervals on the cadmium

Piscator and Rylander (unpublished data) exposed guinea pigs
to free cigarette smoke for one month (1 cigarette per day  for
one week, 4 cigarettes per day for 3 weeks).  The method used
was the one by Rylander, 1969. By means  of  a  suction  device,
the animals were exposed for two seconds every minute  to the
smoke from a puff of two seconds' duration. About 10  puffs
from each cigarette were given.  In table 3:5 the concentra-
tions of cadmium and zinc in the renal cortex of exposed

animals compared with  controls  are  shown.  The  cadmium  concen-
trations  are  significantly  higher in  the exposed  animals  than
in the controls. There  is also  a difference  in zinc  concentra-
tions .

Estimates of  the daily  intake of cadmium based mainly  on  the
data  on cadmium  concentrations  in food  have  been  made  in  sev-
eral  countries,  as  shown  in table 3:6,  together with results
from  investigations  in  which an aliquot from the  total  24-hour
diet  has  been  examined  (Tipton  and  Stewart,  1970,  and  Bostrom
and Wester,  1968).  There  is a marked  discrepancy  when  the  re-
sults of  Schroeder et  al.,  1967, and  Tipton  and Stewart,  1970,
are compared  with  those of  the  other  investigators.  It should
be noted  that  atomic absorption without extraction of  the  metal
was used  in  these  two  investigations. As has been pointed  out in
Chapter 2,  there is  a  risk  of .obtaining values that  are too high
with  this particular method because of  interference  from  sodium
chloride. It  should  also  be noted that  in  non-polluted areas
in Japan,  the  intake  of  cadmium  does not seem to differ markedly
from  the  intake  in  the  European countries  included.

At concentrations  below 10  ppb, cadmium in water  will  contribute
very  little  to the  daily  intake. A  concentration  in  drinking
water around  20  ppb  would increase  the  daily intake  with  20-40
fug at a consumption  of  1-2  liters per day.

Cadmium in  air will  also  contribute very little in non-polluted
areas. If it  is  assumed that normally around 20 m of  air are
inhaled every .day,  concentrations of  0.001-0.01 yug/m  would not
give  more than 0.02-0.2 yug  per  day  via  the respiratory route.
The deposited  amount would  be less  than that.  It  has been  men-
tioned that  concentrations  of 0.1-0.5 yug/m  have  been  found
around cadmium-emitting factories.  These concentrations would

cause an inhalation of 2-10 ug per day. This is still  less  than
the oral intake, but as will be discussed in the next  chapter,
the absorption rates for the gastrointestinal  route and  the
respiratory route are quite different. Thus, exposure  via  air
can be an important factor.

An additional source might be smoking. Twenty  cigarettes per
day will probably cause the inhalation of 2-4 jug.

It should also be pointed out that there is a  possibility  of
respiratory exposure to cadmium in areas contaminated  by cadmium
when in dry seasons deposited dust is again tranferred to  the
air by whirlwinds, etc. Sporting areas and playgrounds for
children could be sources of this type of exposure.

Human beings will be exposed to cadmium via food, water  and air.
Exposure via food is the most important. In uncontaminated  areas
most foodstuffs will contain less than 0.05 ppm of  cadmium, wet
weight, and the daily intake will be about 50  ug. Liver  and kid-
ney from animals and shellfish are among foodstuffs that may have
concentrations larger than 0.05 ppm, even under normal circum-
stances. When certain foodstuffs are contaminated by cadmium in
soil and water, the cadmium concentrations may increase  consid-
erably. Among these are rice and wheat, in which concentrations
around 1 ppm have been reported. This may result in increases  in
daily intake of cadmium.

In water the normal concentration of cadmium is less than  1 ppb.
If the cadmium concentration in drinking wate.r exceeds 10  ppb,
it might contribute significantly to the daily intake  of cadmium.

Whereas the "normal" concentrations  of cadmium  in air,  about 0.001
^ug/m , will not  contribute  significantly  to  the  daily  intake of
cadmium, in areas where  cadmium-emitting  factories  are  situated
concentrations of 0.1-0.5 /ug/m  (weekly or monthly  means) have
been recorded. This may  result in  the inhalation of 2-10 /ug cad-
mium per day. It should  be  remembered that a  considerably larger
percentage of inhaled  cadmium  compared with  ingested cadmium will
be expected to be absorbed.

Heavy smoking might also contribute. It can  be  expected that the
smoking of 20 cigarettes per day will cause  the  inhalation of 2-
4 tig of cadmium.

           (mg/m2/month). EMISSION OF CADMIUM: 460 KG/MONTH (from
           Olofsson 1970).
                Distance and direction from the source
Period          0.1   0.3   0.3   0.5   0.7   1.0   10.4 km  Note
                S     NE    N     NNW   NE    SW    ENE
10.10-20. 11.69
1.2 0.5
1.9 0.7
(0.9) (0.1)
3.7 2.3
4.7 2.5
5.3 2.4
(0.4) (0.8)
0.4 2.1
4.0 3.5
(1.3) (1.3)
0.8 1.2
2.0 1 .1
1.7 1.0
0.6 0.2
0.7 <0.03
(0.1) «0.1)
1.1 <2
1.3 0.7
0.8 0.3



           (Kitamura, personal communication)
Cd ppm
0.5 kilometers
from emission

Control area




Table 3:3
YIELD. (Kobayashi,  1969).
of Cd
to soil
(% CdO)
0. 16
1 .37

Cd ippm)
whole grain
41 .4

Table 3:4  CADMIUM IN FOOD (ppm wet weight).

Wheat flour
Schroeder and Balassa (1961)
Essing et al. (1959)
Lener and Bibr (1970)
Rautu and Sporn (1970)
Ishizaki, Fukushima and
(Won polluted
                                                                Sakamoto (1970)

           Rylander,  unpublished data).
                    ppm dry weight
              n     cadmium     zinc

Controls      15    8.4*1.2     13319
                    p<0.025    p *£. 0.0025
Smokers       22    10.0±2.8   151119

Table 3:6

U.S.A.        4-60

Germany       48

Roumania      38-64

Czechoslova-  60
Japan (Non-   59
               Atomic absorp-
               tion after


               Dithizone or
               isotope dilu-
               tion or atomic

               Dithizone or
               atomic absorp-
               tion after
                         Schroeder and
                         Balassa 1961

                         Essing et al. 1969

                         Rautu and Sporn

                         Lener and Bibr
                         Yamagata and Shige-
                         matsu 1970

The isocurves  are at the 10,  3 and 2 ppm levels.
Figure 3:1
Concentration of Cadmium in Moss (ppm dry weight)
in an Area Surrounding a Cadmium-Emitting Factory
(from Olofsson,  197H).

     Cadmium in Mows Leaves
     ppm dry weight.





          500    1000    1500   2000    2500    Control area
                                           Distance in meters
                                           from the factory.
 Figure  3:2
    Concentration  of Cadmium in
    delation  to  Distance  from a
    in Annaka City.  -Taoan  (from
                              Leaves of a Shrub in
                              Cadmium-Emitting Factory
                              data by Kobayashi. 1969)

                         CHAPTER 4

There is abundant evidence from human data that cadmium  is  found
in different organs in concentrations increasing with  age  (see
section 4.3.2). Data from workers exposed to cadmium as  well  as
from animal experiments show also that cadmium is absorbed  after
exposure:. For the human being there are two main ways  of absorption,
via the  .respiratory and gastrointestinal tracts.

4.1.1  Respiratory deposition, clearance and absorption
Some conclusions can be drawn from general knowledge about  dep-
osition and clearance of particulate matters in human  beings.
Apart from that, virtually all evidence of deposition, clearance
and absorption of cadmium compounds is based on animal experiments.  R_es_pi_ra_tp_ry_ jdep_os_iMp_n_
There are no data elucidating the immediate respiratory  deposi-
tion after inhalation of cadmium or cadmium compounds. As cadmium
exposure via inhalation will be in the form of an aerosol,  there
is every reason to believe that the deposition will follow  gener-
al physical laws governing deposition of particulate matters  (See
e.g. Task Group on Lung Dynamics, 1966, Air Quality Cri teria  for
Particulate Matter, 1969). Thus particle size will have  a deci-
sive importance and in humans breathing at a moderate  work  rate
(20 1/min), the deposition in the pulmonary compartment  will  vary

from about 10 to about 50 percent for particles with a mass median
diameter of from about 5 microns to 0.01 microns.
Although deposition patterns  for particles of different sizes are
fairly well known, clearance  rates are not. However, certain gen-
eral tendencies can be stated. Particles deposited on the bronchial
mucosa, for example,  are  usually cleared by means of ciliar activity
within hours.  Thus, particles with high probability of deposition in
.the tracheobronchial  compartment (relatively large particles) should
be cleared relatively  fast. For particles  deposited in the pulmonary
compartment, however,  solubility and other physico-chemical proper-
ties of these  particles will  be the most important factors. Half-1
lives in the lungs are reported from a few days to about a year for
different substances.  This question was dealt with to some extent
by the Task Group on  Lung Dynamics and is  for the moment the subject
of a new review by another task group under the ICRP on respiratory
absorption and elimination mechanisms (chairman: Thomas Mercer, Ph.D.,
Rochester, N. Y. ) .

Concerning cadmium specifically, no precise information seems to be
available on the several  clearance mechanisms and their rate con-
stants. However, some  data have been reported by Harrison et al.,
1947. They exposed dogs via an atomizer to a 25 percent solution of
cadmium chloride over a period of  30 minutes. The exposure varied
                     3                        33
between 280-360 mg/m   with an L0go of 320  mg/m  or 9600 min  ' mg/m  .
They measured  the concentration of cadmium in lungs, kidneys and
liver at autopsies at  different times after the exposure. The lung
data are shown in figure  4:1.

As can be seen, clearance was rapid during the first two weeks with
a half-life of approximately  five  days. With all probability, the

initial clearance was still mora rapid, even if this is not shown
in the figures (no data from the very early post-exposure period
are reported). The long-term clearance seems to have been slow as
no further decrease was evident at the 10 weeks' observations. No
information was given concerning particle size. The very high ex-
posure, as a rule leading to the deaths of the animals, makes it
impossible to extrapolate clearance rates for lower concentrations
An initial rapid clearance has also been reported by Gerard,  1944
(as quoted by Harrison et al., 1947). Gerard exposed mice to  atom-
ized radioactive cadmium chloride and found that about one-fourth
of the cadmium initially retained in the lungs remained there for
forty-eight hours.

A report by Barrett, Irwin and Semmons, 1947, should also be  men-
tioned. They exposed groups of several animal species to cadmium
oxide fumes in order to determine the toxicity of cadmium (see
section 5.1). They reported retention values for cadmium in the
lungs at different times after the exposure. The percentage re-
tention (based upon cadmium concentrations in the lungs at post
mortem and exposure data) varied between about 5 and 20 percent
with an average of about 11 percent. No systematic differences
were found between values from the early post exposure period
and from the period beginning two weeks later. The exposure con-
ditions varied considerably, however, and few conclusions can be
stated concerning clearance rates.  Res_pj:r£t£ry_
Abundant evidence verifies that cadmium can be found in different
organs after industrial exposure in concentrations well above
those found in the organs of "unexposed" subjects, (see 4.3.2).
Thus, absorption via inhalation takes place. The information a-
bout exposure and lung deposition is, however, so scarce that

quantitative evaluations of absorption rates from such data can
not be made at this time.

Cadmium found in the internal organs such as the liver and kid-
neys coold be the result of a direct absorption from the lungs
or of secondary absorption via the gastrointestinal tract, fol-
lowing a mucociliary lung clearance. Which proportions of the
absorption can be attributed to either of these two means, res-
pectively, are not exactly known.

In the above mentioned report by Harrison, et al., 1947, the up-
take in the kidneys and  liver in dogs after an acute exposure
was studied. The results are shown in figures 4:2 and 4:3. An
increase in the concentration in the kidneys occurred simulta-
neously with a decrease  in the lungs. Thus, the concentration
in the kidneys reached about the same value (per gram dry weight)
as had been present in the lungs during the first stages following
exposure. Since no information was given concerning total lung and
kidney weights or the initial lung deposition of cadmium, a pre-
cise quantitative analysis is not possible. The data do. however,
fit with a high absorption, even taking into consideration that
the initial lung deposition certainly was considerably higher
than is evident from figure 4:1.

A conclusion that the absorption was high would also be reached
if a calculation starts  out from data concerning inhaled cadmium
and recovered cadmium in liver and kidneys. The dogs were exposed
to about 300 mg cadmium  chloride/m  for 30 minutes and at least
about 6 mg of cadmium/100 g dry weight (corresponding to about
2 mg/100 g wet weight) was found in the liver (figure 4:3) after
a couple of days. The concentration in the kidneys was at least
about 7 mg/100 g dry weight (figure 4:2), which would correspond

to  about  1.5  mg  cadmium/100  mg  wet  weight.  If it is assumed that
about  three fourths  of the  cadmium  in the body (not counting the
gut  content)  is  in  the liver and kidneys  (see section 4.3.4) and
that the  weights  of  the dogs were 20 kg,  with a lung ventilation
of  300  1  per  hour (Altman  and Dittmer,  1954)  and a liver weight
of  about  4 percent  and kidney weights of  about 0.4 percent of
the  body  weight,  the following  tentative  estimations could be
made.  About 50 mg cadmium  would have been inhaled and about 20
mg  of  cadmium would  have been retained in the body a few days
after  exposure.  This would  mean a retention of about 40 percent
of  the  inhaled cadmium.

In  regard to  the  mode of absorption, it seems highly probable
that a  direct absorption, was definitely the most important. The
absorption was very  rapid  and studies of  several animal species
show that the absorption of  cadmium via the gastrointestinal
route  is  low  (see

Potts  et  al., 1950,  reported about  cadmium absorption and reten-
tion in mice  a few  hours after  a single inhalation exposure to a
radioactive cadmium  chloride aerosol (particle size less than 2
/»)•  The concentration of cadmium in the exposure chamber was on
9                    3
an  average  100 mg/m   and the exposure time, about 30 minutes.
Because of several  inconsistencies  in the report, there are dif-
ficulties in  interpreting  the results as  they are presented. It
seems,  however,  that the data tend  to show  a  retention of in-
haled  cadmium in  internal  organs (not counting the gut content)
of  about  10-20 percent.

Two  chronic exposure studies,lasting for  several months, both of
which  are discussed  in detail in section  5.2*2, should be men-

Friberg, 1950, in experiments with rabbits inhaling cadmium iron
dust, found a high absorption as judged by concentrations of cad-
mium found in kidneys and liver. It can be calculated that the
rabbits had inhaled,on an average,a total of about 190 mg of cad-
mium iron oxide dust, corresponding to about 120 mg of cadmium
(data by Guyton,  1947, indicating a lung ventilation of about 50
1 per hour for rabbits of about 2 kg, have been used in the cal-
culations). The concentrations of cadmium in lungs, kidneys and
liver at autopsy were reported as generally varying from about
5 to 15, 30 to 70, and 10 to 40 mg/100 g wet weight, respectively
(spectrographic determinations). With weights of approximately 25,
15 and 65 g for lungs, kidneys and liver, respectively, the mean
values for the organ amounts of cadmium can be estimated to have
been as follows: the lungs contained about 2.5, the kidneys about
7.5 and the liver about 16 mg of cadmium, a total in these organs
of about 25 mg retained cadmium. It can be expected that these
organs contained about three fourths of the total body burden
(see 4.3.4). It seems thus that the pulmonary absorption
   25 " 10
(  	  percent  )  of the inhaled cadmium was high, about
   75 *120
30 percent. This of course means a considerably higher absorp-
tion of the cadmium that was deposited in the lungs.

Princi and Geever, 1950, made similar studies with dogs inhaling
cadmium oxide dust and cadmium sulphide dust, respectively. Avail-
able data do not  lend themselves to a detailed calculation like
the one referred to above. The absorption must have been lower
than in Friberg's studies, however, or the excretion of cadmium
must have been very large, as the concentration of cadmium in the
liver and particularly in the kidneys (dithizone method accord-
ing to Church, 1947)  was usually low. The kidney concentration
varied from 2.1 to 13.3 mg/100 g  -  probably wet weight, but no
information was given in the paper -  in animals exposed to cad-

mium oxide, and from 0.02  to 4.3  in  animals exposed  to  cadmium
sulphide. Corresponding values  in  the  liver were  1.2  to  4.7  and
less than 0.04 to  1.0 mg/100 g. The  reported  kidney  values are
of the same magnitude as has been  reported for  human  beings
without occupational exposure  (see section  The  liver
values for dogs exposed to cadmium oxide dust are considerably
higher than those  found in non-occupationally exposed human

The difference in  absorption found by  Friberg as  compared to
that reported by Princi and Geever is  not easily  explained.  Of
some relevance could be that the U.S.  cadmium dust differed
from the Swedish dust in regard to solubility in  water. The
Swedish dust was more soluble  (Ahlmark, Friberg and Hardy,
1956).             ^
It is clear that cadmium can be absorbed and retained to a con-
siderable degree in the body after inhalation. The absorption
is primarily direct from the lungs.

Observations on human beings do not give quantitative data on
absorption and retention. Animal experiments speak in favor of
a retention of between 10-40 percent of inhaled cadmium. A con-
siderable difference might well exist for different cadmium com-

There is a great need for more detailed studies on the absorp-
tion and retention of different cadmium compounds after inhala-
tion. Studies should be carried out on different species and
in connection with acute as well as chronic exposures.

4.1.2  Gastrointestinal absorption
4.1.2. 1   n  Single exposure
Several reports have described the fate of a single oral dose of
radioactive cadmium. Decker, Byerrum and Hoppert, 1957, gave about
6.6 mg/kg of    Cd as the nitrate to rats in stomach tube and
after 8 and 24 hours found 98-99 percent  in the stomach, the gut
and the feces. These results would indicate an absorption rate of
1-2 percent. Cotzias, Borg and Selleck, 1961, gave 40 /uCi    Cd
as the chloride to mice by intubation and found that after 4 hours,
0.5-8 percent had been absorbed  (mean not given). Richmond, Find-
lay and London, 1966, gave    Cd (dose and compound not stated) to
mice by intubation. They found a mean retention after a few days
of about one percent, (range: 0.5-3 percent) which means that on
an average at least one percent had been absorbed. Miller, Black-
mon and Martin, 1968, and Miller et al., 1969, gave goats    Cd-
chloride (0.04-0.06 mg/Cd per goat) in gelatine capsules and
found that more than 90 percent of the dose had been excreted in
the feces after 14 days. The absorption rate was not calculated,
but as Miller et al . , 1969, estimated, total body retention was
0.3-0.4 percent of the given dose and urinary excretion was in-
significant. Thus, not more than a few percent of the dose can
have been absorbed.

Suzuki, Taguchi and Yokohashi, 1969, gave mice on a normal diet
0.08 mg of    Cd as the chloride by stomach needle. They followed
the whole body retention ^digestive tract with contents removed)
between 0.5 and 164 hours in groups of three mice. Maximum reten-
tion was found after 11 hours, when 7 percent of the dose was in
the body (range: 4.5-12 percent). After 164 hours, 1.6 percent
(range: 1 - 2.3 percent) was present.   Kitamura  (personal com-
munication) found that about 2 percent was retained after 24 hours

 when mice were given a single oral dose of 250 Ljg cadmium
 nitrate.  Tomita and Togo (personal communication) obtained
 similar values (2.1 percent 24 hours after exposure and 1.8
 percent 76 hours  after exposure).

 4. 1.2. 1.2  Repeated exposure
 Decker et al., 1958, gave rats cadmium in drinking water in
 concentrations ranging from 0.1-10 ppm during 6 and 12-month
 periods.  (This experiment will also be discussed in section They did not measure total body retention,  but did
 determine the percentage of the administered dose retained in
 kidney  and liver  after one year.  As these organs will accumu-
 late most of the  cadmium, this estimate may indicate  the whole
 body retention.  Less than one percent of the total ingested
 amount  had been retained in these  organs (0.3-0.5 percent at
 all  exposure levels).  If it is assumed that 50-75 percent of
 the  total body burden  is in liver  and kidney (see 4.3.4),  to-
 tal  retention would be less than  one percent.   As urinary ex-
 cretion and excretion  into the intestines are  almost  insignif-
 icant before any  toxic effects are seen (see section  4.2.4),
 this would mean that absorption would be of the same  magnitude
 as  the  retention,  or around one percent on  the average.
Miller et al., 1967, administered about 5 mg Cd/kg to cows daily
for two weeks. During the second week, cadmium excretion in
feces was determined. Finding that 82 per cent of the daily dose
was excreted, they concluded that 18 per cent was retained. Until
more data have been obtained with regard to passage time of cad-
mium in the intestinal tract of cows, this figure must be re-
garded with caution, especially as the cow does not seem to accu-
mulate cadmium to any large extent. Investigations on cows in
cadmium contaminated areas in Sweden have shown renal levels of
cadmium around 1-2 ppm, wet weight, indicating a low absorption
rate (Piscator, unpublished data).

                                                             4-10.   Influence of dietary factors upon absorption of
            cadmi um Calcium
It has been indicated in several reports concerned with the
relationships among hardness of water, metal uptake and toxicity,
that calcium may play an important role in the uptake of metals
from the intestines. Schroeder, Nason and Balassa, 1967, gave
rats 5 ppm cadmium in "hard" and "soft" drinking water during
one to two years. Since the diet contained adequate amounts of
calcium, however, the difference in total intake of calcium was
only about 5 per cent. The authors found no difference between
the groups in the accumulation of cadmium in liver and kidney
and concluded that the hardness of the water was not in itself
an important factor. Larsson and Piscator (to be published)
gave female rats on low and high calcium diets 25 ppm Cd
as the chloride in drinking water for one and two months. They
found that the rats on the low calcium diet had accumulated
about 50 percent more cadmium in liver and kidney than the rats
on the high calcium diet, indicating a higher absorption in the
former group, as there is no reason to believe that there would
be differences in excretion (see table 4:1).

In addition to the results of these experiments, an influence of
calcium on cadmium transport through the digestive tract has been
found. Fleischman et al., 1968, and Suzuki, Taguchi and Yokohashi,
1969, found that a low content of calcium in the diet caused a
slower passage of cadmium through the digestive tract compared
with high calcium diets in rats and mice.  Vitamin D
Worker and Migicovsky,  1961, found that the uptake of cadmium
in the tibia after an oral dose of    Cd was greater in rachitic
chickens under  treatment with Vitamin D than in untreated chick-

                                                         4-1 1.
ens. They concluded that this difference was due to the effect
of Vitamin D on the intestinal absorption of cadmium, as th.ere
was no difference between similar groups in uptake in bone when
ll5Cd was injected.  Protein
Fitzhugh and Meiller,  1941, mentioned briefly that the toxicity
of cadmium was increased by a low protein diet. Suzuki, Taguchi
and Yokohashi, 1969, gave mice low and high protein diets for
24 hours before and after an oral dose of    Cd-chloride. The
low protein diet gave considerably higher levels of cadmium in
kidney, liver and whole body, irrespective of calcium content in
the diet, indicating an increase in the absorption of cadmium.
Whole body retention was about 9 (range 5-14) and 4.5 (range
3-10) per cent in rats fed low and high protein diets, respec-
tively.  ^n_hjjman_bj3ing£
The absorption can theoretically be studied through long-term
balance studies on intake and excretion of cadmium or on intake
and body burdens of cadmium found at autopsies. Long-term balance
studies have been performed on three subjects (Tipton, Stewart
and Dickson, 1969, and Tipton and Stewart, 1970). Cadmium was
determined daily by atomic absorption (without extraction) in
the diet, in the urine and in the feces during 140-347 days.
The mean daily intake of cadmium was about 170 pg and the mean
daily fecal excretion was about 40 jug. This would indicate an
absorption of about 75 percent.  In Chapter 2 it is mentioned that
sodium chloride is an interfering substance causing an increase
in absorption when cadmium is determined by atomic absorption.
It is highly probable that in the above mentioned investigations
the amount of sodium chloride in the diet has interfered with
the cadmium determinations. This is supported by the fact that

much lower values for cadmium in food (see table 3:5) have
been obtained when the metals have been extracted before ana-
lysis. The values for fecal excretion are within the range
reported by other authors (see section Schroeder and
Balassa, 1961, by using the dithizone method, estimated that the
daily intake of cadmium in the United States could vary between
4 and 60 tig, depending upon foods chosen. Bostrb'm and Wester,
1968, found that in one healthy subject, studied for two per-
iods of five days, the intake of cadmium was 12 tig per day in
both periods and the mean fecal excretion of cadmium was 5.3
and 4.5 ug, respectively. The determinations were done with
neutron activation. These data do not lend themselves to an eval-
uation of absorption, due to the short observation period..

The body burden  of cadmium for a "standard man", 50 years of
age, in the United Kingdom and Sweden can be estimated to be
about 15-20 mg and in the United States to about 30 mg (see
section 4.3.4). The cadmium content  in food during the past
50 years can of course not be estimated with any high degree
of certainty. If no substantial changes have taken place over
the years, it would probably be somewhere between 20 and 50 yug
with the higher values probably in the United States.

The newborn contains a total of about only one yug of cadmium.
Thirty mg at the age of 50 would mean a daily absorption of at
least 1.6 tig. In this calculation, a linear absorption rate over
the years has been assumed and also  that the excretion of cad-
mium is negligible. In any case the  last assumption  is with
all probability valid (see section 4.2.4).

An absorption of 1.6 jug/day could be reached with an absorption
rate of 3-8 percent, depending on variations in the  daily in-
take between 20-50 pg. Absorption via ambient air or industrial
exposure has been neglected. Furthermore, these calculations

 are  based  on  averages.  Individual  variations  have  not  been
 taken  into account.
 The  results  from  experiments  on  animals,  mainly  rats  and  mice,
 indicate  that  lass  than  10  percent  of  an  oral  dose  is absorbed.
 Most reports show an  absorption  rate of about  2  percent.  At
 present  there  are no  experimental data that  help us  in making
 an estimate  with  regard  to  absorption  in  human beings.  One way
 to estimate  the absorption  would be to use animal data. This
 would mean that the most  probable average absorption  rate would
 be about  2 percent, but  with  a  large individual  variation. Further,
 absorption of  cadmium has been  shown to be influenced by  other
 factors  in the diet,  suph as  the amount of calcium.  Vitamin D
 and  protein. The  cadmium absorption is increased considerably
 by a low  calcium  or a low protein intake. There  is  no reason
.to believe that the same  should  not hold  true  for human beings.

 Estimations  based on  body burdens of cadmium found  at autopsies
 of the "standard  man" in  the  United States together  with  estimated
 intake over  a  50  year period  point  to  an  average absorption of
 somewhere between 3-8 percent,  e.g. not very much different from
 the  estimations based on  animal  data.

 Until more exact  data are obtained, an absorption rate of about
 10 percent of  ingested cadmium  must be considered quite possible
 in the individual case under  certain circumstances,  such  as
 calcium and  protein deficiency.

 It is extremely important to  study  the question  in  human  beings
 further,  as  an absorption of  2  percent, 5 percent or  10 percent
 would make a substantial  difference from  a toxicological  point
 of view  as will be  discussed  later.

 4.1.3   Placental transfer  ^n_ariimaj.s

 Berlin  and  Ullberg,  1963,  gave  pregnant mice  single  intra-
 venous    Cd-chloride injections  of 10  LCi,  carrier free
   Cd on  the  18th day after conception. They  could not de-
 tect any  cadmium in  the  fetus  but could note  an accumula-
 tion of cadmium in the placenta.  After giving a single
 intravenous dose of  0.5-0.85 mg Cd/kg  to pregnant  hamsters
 on the  8th  day  of gestation, Perm,  Hanlon and Urban,  1969,
 found relatively high concentrations of cadmium both in the
 placenta  and  in the  fetus.. The  dose was considerably larger
 than the  one  given by Berlin and  Ullberg. In  addition, Perm,
 Hanlon  and  Urban administered  the metal at that period during
 wh.ich the major organ systems  are being established  in the
hamster embryo  and the embryologic  activity is  high, whereas
Berlin and Ullberg injected  the cadmium during  the last few
days  of pregnancy.

By exposing (rats  from  the  day of  conception to  cadmium oxide
dust  in concentrations of  about 3 mg/m  ,  Cvetkova, 1970,
found that the  livers  of the embryos after 22 days contained
more  than twice  the  amount of cadmium  contained, in controls.

Large doses of  cadmium will  destroy the placenta,  especially
the fetal part,  as shown by  Parlzek, 1964, who  gave  rats
subcutaneous  injections of 4.5  mg Cd/kg on the  17th-21st
days  of gestation. Parlzek,  1955, showed that 2.5  mg/kg by
the subcutaneous  route had the  same effect. He  also  noted
that  the  pregnant  rat  was  more  susceptible to the  action of

cadmium than the non-pregnant  rat. Parizek  et  al.,  1968,
found that the simultaneous administration  of  sodium
selenite protected the fetus from  the  destructive  action
of cadmium, but increased the  uptake of  cadmium  in -the
placenta. Holmberg and Perm, 1969, found that  selenite
protected the hamster embryo after intravenous injection
of 2 mg Cd/kg. Of additional interest  is the fact  that
chelating agents, such as EDTA, increase the transplacental
passage of cadmium (Eybl, Sykora and Plertl,  1966b).

4 . 1.3.2  In_huma_n_be_i£igs_
Henke, Sachs and Bohn, 1970, analysed  liver and  kidney  samples
from newborns in West Germany  by neutron activation and found
between 4 and 20 ng/g wet weight in four kidneys.  The concen-
tration was less than 2 ng/g in the liver.  This  means that
the total content of cadmium in the newborn  will be less  than
Cadmium will accumulate in the placenta during pregnancy. Con-
centrations of less than 10 ng/g wet weight have been  found  in
Swedish women (Piscator, unpublished data). As the placental
weight is about 500 grams, this means that not more than  5 ug
will accumulate. In comparison, a human kidney will usually
accumulate about 100 ug during a 9-month period  (see section  C_on_c^us_ip_ns_
Animal experiments indicate that the placenta constitutes a
barrier against transfer of cadmium when small doses are  given.
However,  when large doses are given, cadmium may destroy  the
placental barrier and enter the fetus.  In human newborns,
the total body content of cadmium is small, less than  1 pg.

 Cadmium will be  found in blood,  internal organs and excreta after
 absorption  following exposure via air, oral intake or injection.
 In  the  following sections,  the metabolism after both single and
 repeated exposure will be considered.  The distribution of cad-
 mium  after  respiratory exposure  has been discussed in section and will not be further treated in this section.

 4.2.1   Uptake to and clearance from blood
.In  section was mentioned  that after oral exposure only a
 few percent of the dose was absorbed.  Attempts to determine levels
 of  radioactive cadmium in blood  after a single dose have not been
 successful, so only cadmium in blood after injection will be
 considered  in this section.   Fat^e__o£ £admi_um i.n_bl_op_d_a£te_r_si_n£le_ i_n
 4.2. 1_.j.._l  First hours after injection
 Intravenous route
 During the first hours after injection, cadmium is found mainly
 in  the plasma,  as seen in dogs (Walsh and Burch, 1959), in rabbits
 (Kench,  Wells and Smith, 1962) and in rats (Perry et al., 1970).
 The last mentioned authors found 98-99 per cent of the blood cad-
 mi urn  in  the plasma 0.5 and 8.5 minutes after injection and Kench,
 Wells and Smith found 90 and 80 per cent 9 minutes and 1 hour,
 respectively, after injection. Perry et al. found that about two
 thirds of the plasma cadmium was dialyzable during the first 8.5
 mi nutes .

 The clearance of cadmium from the plasma is characterized by an
 initial  rapid phase followed by a slower phase, as shown in figure
 4:4 from Walsh  and Burch, who gave dogs 0.24-0.36 mg    Cd/kg
 as  cadmium nitrate. Perry et al. also found a rapid clearance
 in  rats  during  the first 8.5 minutes after an injection of 0.2

mg    Cd/kg. Kench, Wells and Smith  gave a  large  dose,  about
4 mg    Cd/kg as the sulphate to  two  rabbits  and  found  that
after 9 minutes about 45 per cent of  the dose  remained  in  the
plasma and after 1 hour, 6.5 par  cent. As they gave a lethal
dose and one rabbit died within 6 hours, their data can not
be regarded  as representative for the rabbit.

Perry et al. found a small uptake of  about  2  per  cent of the
blood cadmium in the erythrocytes after 0.5 minutes. Though
Walsh and Burch mentioned that a  small but  constant amount
of cadmium was found in the cells, they did not report  the

Intraperitoneal route
After an intraperitoneal injection of soluble cadmium compounds,
the maximum blood levels are reached within very  short periods.
In studies by Johnson and Miller, 1970, who gave  rats    Cd
(0.01-0.02 mg/kg) as the chloride, the maximum concentration
was reached after 5 minutes. In similar studies.CPerry and  Erlanger
to be published) maximum blood levels were  found  8  minutes after
injection (rats, '  Cd as chloride, 0.06-0.96 mg  Cd/KgJ. in
the last mentioned experiment,  it was calculated  that 3 per
cent of the injected dose was circulating in  the  blood.  In the
study by Johnson and Miller, the blood level  80 minutes  after
the injection was only 12 per cent of the maximum value, indi-
cating a rapid initial clearance  from the blood.   Perry and
Erlanger reported that the concentrations 120 minutes after
the injections had decreased to 44 and 16 per cent of the maximum
concentrations after injections of 0.24 and 0.96   mg Cd/kg,
respectively. They further stated that only a few per cent
of the cadmium in the blood were  in the red cells and  that
part of the plasma cadmium was  dialyzable.

Subcutaneous route

After a subcutaneous injection of soluble cadmium com-
pounds, cadmium will soon appear in the blood and maximum
levels have been reported after 10 minutes by Johnson and
Miller, 1970, and after 60 minutes, Eybl, Sykora and Mertl,
1966a. Johnson and Miller gave rats 0.01-0.02 mg    Cd/kg
as the chloride. They found that there was a rapid initial
clearance, so that 80 minutes after injection, the concentra-
tion in whole blood was only 16 per cent of the 10 minute
value. Eybl, Sykora and Mertl gave rats 1.25 mg    Cd/kg as
the chloride, and found that the concentration in blood after
1 hour was higher than after 20 minutes. The difference in
the results will probably be explained by the considerably
larger dose, given by the latter authors, which will have
resulted  in a large deposit at the injection site.

During the first 12 hours, there will be a decrease in blood
levels, as shown in Fig. 4:5, where data from the experi-
ment by Eybl, Sykora and Mertl, 1966a,are shown together
with data from Gunn, Gould and Anderson, 1968 a, who gave
mice 1.4  mg    Cd/kg as the chloride, and from Lucis,Lynk
and Lucis, 1969. who gave rats a tracer dose of    Cd as
the chloride. This decrease is mainly due to a decrease in
plasma levels of cadmium, as shown in Fig. 4:6, where data
are taken from the experiments by Eybl, Sykora and Mertl,
1966a,and Lucis, Lynk and Lucis, 1969. In Figure 4:6, it
will also be seen that there is an initial uptake in the
cells, and that the clearance from the cells during the
first  12  hours is smaller than the clearance from the plasma,
so that after about 12 hours, concentrations are of the same
magnitude in cells and plasma.

                                                              4-19.  First weeks after  injection
Whereas there are large differences  in  distribution during the
first hours after injection,  depending  on  how fast cadmium enters
the blood, distribution and clearance mechanisms  seem to be rrore
similar when some time has elapsed  since  injection. Figure 4:5
shows the levels in blood in  animals  exposed by  the subcutaneous
route. Blood levels decrease  during  the first 12  hours.  Then
a change occurs: the blood levels increase again.  In rats,
this increase is due to an increase  of  the cadmium content of
the erythrocy tes, as shown in  figure  4:6.

It should be noted that in both  the  experiment by  Gunn,  Gould
and Anderson, 1968a, on mice  and by  Lucis, Lynk  and Lucis, 1969,
on rats, there was a decrease  after  the 7th day.  IMiemeier, 1967,
followed rats after an intravenous  injection of     Cd sulphate
and found that after 16 days  the cadmium  level in  blood  was more
than twice the level at day one. In  the goat (Miller, Blackmon and
Martin, 1968) and the hamster  (Ferm,  Hanlon and  Urban,  1969), a
rise in the cadmium level between day  1 and day  7  and day 1 and
day 2, respectively, after intravenous  injections, has been noted.

These results indicate that after the first rapid  clearance of
cadmium from blood, a second phase will occur in which cadmium
will be released into the blood, probably  from the liver, where
the main part of the injected  cadmium will be found (see section
4.2.2).  F9.te_ £f_ca_dmi um_in_ b_lp_od^ £^e£ £ep_eate_d__inje_cjn.p_ns_ _
Friberg, 1952, found, in  rabbits given  subcutaneous  injections
of 115Cd-sulphate  (0.65 mg Cd/kg six  days  a  week for 4 and 10
weeks), that the cadmium  levels  in  blood  were  45  and
ml blood, respectively. He could  not  demonstrate  the presence

of cadmium in the plasma  and  concluded  that  the cadmium was  in
the blood cells.  Truhaut and Boudene,  1954,  gave  two  rabbits
subcutaneous injections of  cadmium sulphate,  13 injections of
2.1 mg/kg and 19 injections of  1.8 mg/kg. They found that the
concentration in the  erythrocytes was  18 and  10 times  greater,
respectively, than in  the plasma. Friberg,  1955, made  new exper-
iments with similar exposure  conditions as  in 1952. In one exper-
iment rabbits were given    Cd  during  70 days. In  another, they
were first given the  isotope  for 50  days and  then  ordinary cad-
mium for the remaining 20 days. In both experiments cadmium
levels rose steadily  until  the  50th  day, at which  time they
were around 200/jg/100 ml.. In  rabbits given  further injections
of    Cd, blood  levels of the isotope  remained around  200 yug/100
ml after 10 weeks. In  rabbits given  nonradioactive cadmium,
a decrease in    Cd levels  to about  125 ^ug/100 ml  in 20 days
was found. The results show that at  a  certain cadmium  level  in
the blood a plateau is reached. A continuous  exchange  between
cadmium accumulated in the  blood and newly  administered cadmium

Carlson and Friberg,  1957»  gave 1 mg    Cd/kg to two rabbits
daily for one week. The animals were killed  2 days after cessa-
tion of exposure. They also gave 0.65  mg     Cd/kg  to two other
rabbits daily for three weeks.  The animals were killed 3 weeks
after cessation  of exposure.  One to  six percent of the cadmium
in whole blood was found  in the plasma. When  red cells from
these rabbits were hemolyzed  and centrifuged,  all  cadmium was
recovered in the supernatant. Forty  and thirty-seven per cent,
respectively, of the  cadmium  in the  hemolysate was found to
be dialyzable through  polyvinyl tubings. Separation by zone
electrophoresis  in starch of  hemolysates  from two  other rabbits  exposed
2 and 4 weeks showed  that most  of the  cadmium in the hemolysate
was in the same  fractions as  hemoglobin and  the authors concluded
that part of the cadmium  was  bound to  hemoglobin.

4.2.2  Tissue distribution and retention   i
Oral route
The amount absorbed after a single dose  is small,  as  has  been
discussed in section 4.1.2. The distribution  in  organs  has  been
studied by several authors. Decker, Byerrum and  Hoppert,  1957,
gave rats    Cd-nitrate  (6.6 mg Cd/kg) and determined cadmium
distribution from 8 to 360 hours after the dose. After  8  hours
the largest total amount of cadmium was  in the liver while  the
highest concentration was in the kidneys. After  maximum concen-
trations in both organs were reached at  72 hours after  exposure,
a slow decrease seemed to occur in both  organs.  Miller, Blackmon
and Martin, 1968, gave a single oral dose of     Cd-chloride
to goats (0.04 mg Cd/goat) and found that after  14 days the
concentration in the kidneys was nearly  twice as high as  that
in the liver. Miller et al . ,  1966, gave about 0.06 mg  of    Cd
to groups of goats,  one group of which had been  pretreated  one
week with a diet containing 100 ppm of non radioacti ve cadmium.
                 1 09
Determination of    Cd content in organs was  made  14  days after
exposure. They did not find any differences between the groups.
Suzuki, Taguchi and Yokohashi, 1969, put mice on diets with
high calcium-low phosphorus and low calcium-high phosphorus
content, respectively, for 10 days and then gave then) a single
dose of    Cd-chloride (about 0.08 mg Cd/mouse). Liver and
kidney levels were measured after 24 and 72 hours, respectively.
No difference was found between the groups. However, within  the
groups differences in levels at the two times of measurement
could be seen. After 72 hours both kidney and liver levels were
only half of the 24 hour values,  indicating rapid clearance.

Injection route
The distribution of cadmium will  vary  considerably  depending  on
the dose and the time. The experiments mentioned  in,  in
which the fate of cadmium in blood after a single dose was  fol-
lowed showed in addition that most of  the cadmium initially goes
to the liver and relatively small amounts to  the  kidneys. With
increasing time after exposure, the kidney levels will increase
and will become higher than liver levels.

Gunn and Gould, 1957, gave a single intracardiac  injection  of
   Cd-nitrate to rats (dose not stated) and followed the  animals
for up to 8 months. From their data it is seen  that  during  the
first month there was a decrease  in liver levels  of    Cd and
an increase in kidney cortex levels, so that  after  a month  of
exposure, the concentration in the cortex was the same as that
in the liver (Figure 4:7). During the  following months liver
levels decreased very slowly while levels in  cortex  increased
so that after 5 months the ratio  between cortex and  liver levels
was 2.4 and after 8 months, 4-5.  The levels in  kidney medulla
also increased with time and after 8 months they  exceeded liver
levels. In addition, the authors  observed that  age  could  influence
uptake in the kidney in rats from 1-7  weeks old,  so  that  the
younger the rat, the less the uptake.  To the  contrary, liver
levels did not vary with age. This was explained  as  due to  the
smaller number of nephrons in the younger rats. Decker, Byerrum
and Hoppert, 1957, injected    Cd-nitrate into  rats  by the  intra.
venous route (approximately 0.65  mg Cd/kg). They  found that
from 4 hours to 5 weeks after injection the liver contained
between 62 and 70 per cent of the injected dose.  The kidney
contained between 1.6 and 2.4 per cent of the dose  from 4 hours
to 2 weeks. Then, at five weeks,  5.1 per cent of  the total  dose
was found in the kidney.

Burch and Walsh, 1959, found that in  dogs  given an  intravenous
injection of    Cd-nitrate  (0.24-0.36 mg Cd/kg),  the  concen-
tration in the  liver during the first 24 hours was  considerably
greater than that in the kidneys. After 20-30 days, the  concen-
tration in the  kidneys was  50-100 per cent of the  liver  levels.
Lucis, Lynk and Lucis, 1969, followed cadmium concentrations
for 14 days after giving a  tracer dose of    Cd-chloride  to rats
by subcutaneous injection.  They found that already  2  hours after
injection kidney levels were slightly higher than  liver  levels
and that 10 hours after injection, the concentration  in  the
kidneys was about 50 per cent higher  than  that in  the  liver.
At 2 weeks both the kidney  and liver  concentrations had  increased
compared with the concentrations at 30 hours. Miller,  Blackman and
Martin, 1968,  investigated the distribution in goats 14 days after a
single intravenous administration, using    Cd (0.04  mg/goat).
Concentrations  in liver were three times higher than  those in
kidney, whereas after an oral dose of the  same size,  the  concen-
trations in kidney were nearly twice  as high as those  in  liver.
Lucis and Lucis, 1969, studied four strains of mice and  found
considerable differences in organ concentrations 24 hours aftar
subcutaneous injection. Liver levels  varied between 37 and 52
per cent of injected dose per gram.

The liver and the kidney seem to be the two organs  of  greatest
interest with regard to cadmium storage. Cadmium will, however,
be found in most compartments of the body. The pancreas  and
the spleen will store relatively large amounts. Nordberg  and
Nishiyama (to be published) found that in mice cadmium levels
in the pancreas increased with time and exceeded  liver levels
110 days after injection (5 jug Cd/kg, intravenous).  Figure 4:8
shows the distribution of    Cd 110 days after a single  injec-
tion.  Berlin and Ullberg, 1963,  did not find cadmium  in  osseous
                                              ' 109
tissue after a single intravenous injection of    Cd-chloride,

but they did observe  that  cadmium was  accumulated  and  retained
in bone marrow and periostium. They  detected  traces  of cadmium
in the brain. Their  finding  of an accumulation  in  the  testis
and the hypophysis is  also of interest.  Rep_ea_te_d_ex_p£s^jre_
Oral route
Long-term experiments  with exposure  via  the oral route have
been made by Decker  et al.,  1958, who  gave cadmium in  drinking
water to rats for 6  and  12 months. The concentrations  of  cadmium
in the water were 0,  0.1,  0.5, 2.5,  5  and  10  /ug/ml.  They  found
that the concentrations  in kidneys and liver  were  roughly pro-
portional to the intake  of cadmium.  It was also found  that the
larger the dose, the  larger  the  ratio  became  between concentra-
tions in liver and kidneys,  as shown in  table 4:2. Data from  a
similar experiment on  dogs by Anwar  et al., 1961,are included in
the table.

Injection route
Friberg, 1952, gave  subcutaneous injections of     Cd-sulphate
(0.65 mg Cd/kg) to rabbits 6 days a  week for  4  and 10  weeks,
respectively. Four rabbits exposed for 4 weeks  had mean levels
of 1160, 600, 75 and  45  ppm  Cd (dry  weight) in  liver,  kidney,
pancreas and spleen,  respectively. After 10 weeks  the  correspond-
ing figures were 1480, 1000, 193 and 160 ppm. During the  period
of 4-10 weeks of exposure  the accumulation rate of liver  and
kidney decreased, that of  spleen increased and  that  of the pan-
creas showed no change.  Since cadmium will be excreted during
this period  (see section 4.2.4), these results  are partly ex-
plained. Friberg, 1955,  made a new experiment with similar ex-
posure for 10 weeks,  bu-t he  gave one group nonradioactive cad-
mium for the last 20  days. After 10  weeks  liver levels of    Cd

were considerably higher than kidney  levels.  In  animals  to which
nonradioactive cadmium had been  given  for the  last  20  days of
the exposure time, the level of  radioactive cadmium in the kidneys
was only about half of the level in animals given the  isotope
during the entire period. This indicates that  during those 20
days the kidneys had excreted part of  the stored cadmium.

Axelsson and Piscator, 1966a,gave rabbits cadmium chloride
(0.25 mg Cd/kg) by subcutaneous  injections 5  days a week  for
11-29 weeks. There was an increase in  liver and  renal  cortex
levels up to 17 weeks. The levels at that time were  about 450
and 400 ppm wet weight, respectively.  Further  exposure did not
increase the concentration in the liver. In the  renal  cortex,
there was a decrease so that the concentration was  about  275 ppm
wet weight after 23 and 29 weeks. As excretion of cadmium was
low until after 17 weeks but then increased considerably  (see
section, these findings agree with Friberg's  results
showing first an accumulation stage, followed  by an excretion
stage. Piscator and Axelsson, 1970, found in a follow-up  of
a group exposed for 24 weeks under similar conditions  (0.25
mg Cd/kg, subcutaneous injection, 5 days a week) and killed
7 months after the last injection that kidney  levels had only
decreased a little compared with the above mentioned
   concentrations at 23 or 29 weeks of exposure.  Liver  levels
were about half of the levels at the time exposure  ceased.

Bonnell,  Ross and King, 1960, gave intraperitoneal  injections
of cadmium nitrate to rats (0.75 mg Cd/kg 3 days/*eek  for 5-6'tnonths)
Exposure was then discontinued for two months, after which in-
jections were resumed for some animals (0.25 mg/kg). Other animals
received no further exposure. The total time for the experiment
was 12 months.  A linear increase of cadmium in liver was seen
during the first three months, when a plateau was reached at

about 350 ppm wet weight  (see figure 4:9). It is conceivable
that at this time excretion of cadmium began. Urinary cadmium was,
however, not determined.  The resumed exposure did not increase
the levels. A gradual decrease was actually seen. In the .kidneys
linear increase was also  seen during the first three months, when
a plateau was reached at  about 275 ppm wet weight (figure 4:10).
At the end of the experiment the levels were lower than at three
months. No difference in  cadmium levels between animals who re-
ceived further injections during the last five months and those
animals who did not, could be detected.
4.2.3  Distribution within organs
4.2.3. 1  Si
Friberg and Odeblad,  1957, gave a single subcutaneous injection
of    Cd-sulphate  (1.3 mg Cd/kg) to rats and killed the animals
after. 5.5 and 24 hours respectively. The renal cortex accumulated
more cadmium than  the medulla. In the pancreas distribution was
equal between exocrine and endocrine parts. Gunn and Gould, 1957,
gave a single intracardiac injection of    Cd to rats and  found
a selective accumulation of cadmium in the renal cortex. They
followed the animals  for 150 days. At that time the cortex con-
tained 4 times more cadmium than the medulla.

Berlin and Ullberg, 1963, gave a single intravenous tracer dose
of    Cd-chloride  to  mice and studied the distribution by  auto-
radiography. The animals were killed at times after injection
varying from 5 minutes to 16 days. In the renal cortex the authors
found scattered areas with high activity. In the liver the dis-
tribution was uniform during the first 24 hours, but after 8
days a higher concentration was found in the periphery of  the
liver lobules. In  the testes especially the interstitial tissue
contained cadmium.

A special study on the distribution in the kidneys was made by
Berlin, Hammarstrom and Plaunsbach, 1964. Mice were killed 24
hours after a single intravenous  tracer dose of    Cd-chlorice.
In the renal cortex the largest accumulation was found in the
outer cortex and corresponded to  proximal tubules. Especially
the first segment of the proximal tubules showed high activity.
The glomeruli did not retain cadmium to the same degree.

The subcellular distribution in the liver has been studied by
Kapoor, Agarwala and Kar,  1961. Rats were given a single sub-
cutaneous injection of cadmium chloride (10 mg/kg) and the
livers were fractionated by ultracentrifugation from 6-168
hours thereafter. The total concentration of cadmium was the
same at the different times. However, there was a change in
distribution with time, so that at 6 and 12 hours after injection
about 30 per cent was in the supernatant, whereas at 24, 40
and 168 hours,  about 60 per cent was in that fraction. This
corresponded to a decrease in the nuclear, mitochondrial and
microsomal fractions.-

Twenty-four hours after a single subcutaneous injection of
   Cd-chloride  to mice and to rats, cadmium was distributed
so that 80 per cent was in the supernatant (Shaikh and Lucis,
1969, 1970). Nordberg, Piscator and Lind (to be published)
found that change in distribution took place with time after
a single injection of cadmium chloride (3 mg Cd/kg) in mice.
During the first 24 hours  almost, more than 80 percent of the
rfd cadmium in  the supernatant was in the high molecular weight
proteins, as shown by gel  filtration, whereas later a change
occurred so that more than 50 percent of the cadmium was in
a low molecular weight fraction, probably metallothionein.
Shaikh and Lucis, 1970, had found a similar low molecular

weight fraction in their experiment.
Friberg, 1952, gave  rabbits subcutaneous injections of    Cd-
sulphate 6 days a week for  10 weeks  (0.65 mg Cd/kg) and found
by autoradiography that in  the kidneys the cortex contained 5
times more cadmium than the medulla. In the  liver more  activity
was in the periphery of the lobules  than in  the inner halves.
In the pancreas the  glandular part accumulated cadmium, while
no cadmium was found in the connective tissue. Friberg  did not
note any difference  between the exocrine and the endocrine
p a rt s .

Long-term experiments on  the rabbit  by Axelsson and Piscator,  1966a.
revealed that during exposure to subcutaneous injection of 0.25
mg cadmium/kg 5 days a week for 11-29 weeks, the ratio  between
cortex and medulla was 5.1  (2.5-9).  In rabbits exposed  in a simi-
lar way for 24 weeks and  then followed for another 30 weeks, the
ratio was 3.6 (2.4-5.5)   (Piscator and Axelsson, 1970).

By using a staining  method  for metals, Axelsson, Dahlgren and
Piscator, 1968, found the main metal accumumlat ion in renal
proximal tubules in  the above mentioned rabbits. Considerably
smaller amounts of deposited metals  were found in the glomeruli,
collecting tubules and medulla.

4.2.4  E x c re t i o n
When a single dose of cadmium has been given via the oral route
or via injection, only a small amount has been detected in the
urine. After a single oral dose of    Cd to goats. Miller,
Blackmon and Martin, 1968, found that on days  1, 2, and 3-7,
after exposure, 0.5, 1, and 0.1 per cent respectively of the

absorbed amount were excreted via the urine. The original  values
have been recalculated to fit an assumed absorption of 2 per-
cent. A dose of the same amount of cadmium as  the oral dose
in the previously mentioned experiment was administered by
intravenous injection. Excretion values were 0.025, 0.004  and
0.002- percent.                                   The authors
pointed out that these values/ could be too high, as fecal  con-
tamination  could'increase the cadmium levels.  In rats, Lucis,
Lynk and Lucis, 1969, found that 1 per cent of  a single subcutaneous
injection of    Cd solution had been excreted with the urine
after 1 week. Burch and Walsh, 1959, calculated the half-life after a
single intravenous  injection of    Cd as nitrate (5 dogs, followed
for 20-30 days). It can be calculated from their data that it would
take 3-7 years to eliminate 50 percent of the cadmium via  the urine
Friberg,  1952, gave subcutaneous injections of  cadmium sulphate
containing    Cd in daily doses of 0.65 mg Cd/kg to rabbits.
When the  excretion of the isotope was followed  for 10 weeks,
as shown  in figure 4:11, it was found that for  a period varying
between 6 and 7 weeks, the daily cadmium excretion was very small,
about 1 percent of the daily injected dose. During the last
weeks of the experiment there was a sharp rise  in cadmium  excre-
tion, up to about 100 times the amount excreted during the
first weeks. This rise in cadmium excretion coincided with
the appearance of proteinuria in the rabbits.

Further investigations were made by Friberg, 1955, under similar
experimental conditions as above. One group  of rabbits was given
first radioactive cadmium for 50 days and nonradioactive cadmium
for the remaining 20-50 days. Another group was given radioactive
cadmium for 70 days, whereafter cadmium excretion was followed
for another 30 days. During the administration  of nonradioactive

cadmium, the excretion of radioactive cadmium increased marked-
ly. In the group that received no more cadmium whatsoever after
the end of the exposure to radioactive cadmium, the concentra-
tion of radioactive cadmium in urine decreased rapidly. It was
thus clearly demonstrated that, at the time kidney damage existed,
the urinary cadmium excreted during exposure came partly from
accumulated deposits.

Axelsson and Piscator, 1966a, gave rabbits 0.25 mg Cd/kg as cad-
mi urn chloride for 5 days a week for 6 months by subcutaneous in-
jection. During the first 4 months there was an insignificant
excretion of cadmium but in the last 2 months there was such a
sudden rise in cadmium excretion that in some animals, the daily
excretion exceeded the daily dose. The increase in urinary excre-
tion of cadmium parallelled an increase in urinary protein. Six
months after an exposure for 6 months two rabbits in a group of
six still excreted large amounts of cadmium (Piscator and
Axelsson, 1970).

In summary,  there is evidence that during long-term exposure the
excretion of cadmium with the urine is only about 1 percent of
the dose. When renal dysfunction has occurred, there will be a
sharp increase in excretion, however. In experiments on rabbits
this increase was 50-100 fold.   xretior  ia the
Animal experiments have shown that injected cadmium will be
partially excreted with the f eces . Decker, Byerrum and Hoppert,
1957, gave the rat a single intravenous dose of    Cd (0.63 mg/kg)
After the first 24 hours, 7.3 per cent was found in the feces.
After 77 hours 18.5 percent of the given dose "fi ad been excreted
via feces.

Burch and Walsh, 1959, injected a single dose of    Cd  (0.32-
0.40 mg/kg) intravenously into dogs. They determined the amount
of the isotope in feces from five dogs for 20-30  days.  They cal-
culated that 419-659 days were required for elimination of half
of the injected cadmium by fecal excretion alone. Relatively
large amounts of the isotope were in the gastrointestinal tract,
especially the small intestine, the first two days after injec-
tion. Berlin and Ullberg, 1963, using whole-body  autoradiography
after a tracer dose of    Cd intravenously injected into mice,
found that cadmium rapidly accumulated in the mucous membrane
of the intestinal tract and that after 24 hours the cadmium in
the mucosa seemed to decrease. Cadmium accumulated mainly in the
secretory part of the gastric mucosa and in the colonic mucosa.
The investigators could also find radioactivity in the  contents
of the stomach and colon 20 minutes after injection. When Lucis,
Lynk and Lucis, 1969, gave a tracer dose of    Cd by a  single
subcutaneous injection into rats, they found that cadmium accu-
mulated rapidly in the wall of the stomach and detected only
traces in the contents of the stomach. In the intestines the
wall of the small intestine had the largest concentration. Radio-
activity in the intestinal contents increased during the first
24 hours.

Johnson and Miller, 1970, compared the results of single sub-
cutaneous and intraperitoneal injections of    Cd (0.02 mg/kg)
as chloride given to rats and with both techniques found cadmium
in the duodenum after 2 1/2 minutes. Miller,  Blackmon and Martin,
1968, gave a single intravenous dose of    Cd as chloride to
goats and found that 5.6 percent was excreted via feces within 5
days .

Ceresa, 1945, determined the daily excretion  of cadmium in 5
rabbits. The animals received 11 mg Cd/kg daily as the sulphate
by the subcutaneous route, which resulted in  the deaths of the

animals after 7-9 days. During the period of exposure, the mean
fecal excretion rate was  1.8 percent of the injected amount and
slightly higher than the  urinary excretion.

Long-term experiments have been performed by Axelsson and Pis-
cator, 1966a, on rabbits  given 0.25 mg Cd/kg as chloride 5 days
a week for 29 weeks by subcutaneous injections. Fecal excretion
was slightly higher than  urinary excretion after  11 weeks but
corresponded to only about 1.6 percent of the  daily dose. After
17 weeks the daily fecal  excretion corresponded to 2.8 percent
of the daily dose. After  23 and 29 weeks, when the urinary ex-
cretion of cadmium was greater, 11.2 and 6.6 percent, respec-
tively, were found in the  feces.

There is thus evidence that injected cadmium is excreted via
some parts of the alimentary tract. On the other  hand, the ex-
cretion is low, less than  5 percent during repeated exposure,
as judged from experiments on rabbits. That both  the gastric
mucosa and intestinal mucosa excrete cadmium is clear, but
as the parotic gland was  shown by Berlin and Ullberg, 1963, to
accumulate relatively large amounts and the pancreas has been
shown in several of the reports to store large amounts of cad-
mium, it is conceivable that excretion from these  two organs
is important. The role of the bile has also to be  taken into
account. Berlin and Ullberg, 1963, found activity  in the gall-
bladder after injection of    Cd as chloride to mice.  Excretion via hair
Truhaut and Boudene,  1954,  found  high  concentrations  of  cadmium
in hair from rats and  rabbits  injected with  cadmium and  suggested
that hair analysis could  be  of  value for  determining  cadmium
levels in exposed workers.  Berlin  and  Ullberg,  1963,  found  that
cadmium accumulated  in  hair of  mice given  a  single dose  of    Cd.

Miller, Blackmon .and Martin, 1968, found that the concentration
in goat hair was about 20 percent of the concentration in the
liver 15 days after a single oral dose of    Cd as chloride'.
After an intravenous dose the corresponding figure was about
one percent. When this experiment was repeated by Miller et al.,
1969, the concentrations in hair were only 3 percent of the
concentrations in the liver. Nordberg and Nishiyama (to be pub-
lished) found that in mice given a single intravenous injection
of    Cd-chloride (4.5 mg Cd/Kg), the decrease in cadmium levels
in hair parallelled the decrease in whole body retention. Less than
0.5 percent of the total excretion between day 41 and 105 was ex-
creted via the hair.
4.2.5  Biological half-life
After oral exposure to    Cd (intubation, compound not stated),
Richmond, Findlay and London, 1966, estimated the biological
half-life in female mice to be about 200 days. In figure 4:12
it can be seen that after a rapid clearance during the first
five days, representing the passage of non-absorbed cadmium
through the intestines, between 0.5 and 3 percent of the dose
is retained. The retained amount will then decrease slowly dur-
ing an observation period of nearly one year.

Cotzias, Borg and Selleck, 1961, gave mice    Cd as chloride
(carrier free, 17 yuCi) by intraperitoneal injection and determined
whole body retention during 20 days. After 5 days about 95 per-
cent of the injected dose remained and after 20 days, about 90
percent. The slow decrease during tho latter part of the obser-
vation period indicates a half-life of at least 100 days.

After injection via the intraperitoneal or intravenous route,
biological half-life was studied in female mice by Richmond,
Findlay and London, 1966. They gave    Cd (compound and dose
not stated) and made repeated determinations of whole body
retention for periods of more than 400 days. After an initial

rapid clearance during the first day, they estimated half-lives
from about 40 days and increasing to 200-300 days during the
latter part of the observation period. Other investigators
(Eybl, S^kora and Mertl,  1970, Nordberg and Nishiyama, to be
published, and Tomita, personal communication) have studied whole
body retention during 1-4 months after intravenous or subcu-
taneous injection of cadmium.  From their data, it can be calcu-
lated that if the first  rapid  clearance is excluded, biological
half-life in mice will vary  between 25-100 days,  generally  con-
firming the findings of  Cotzias, Berg and Selleck, 1961, and
Richmond, Findlay and London,  1966, for that period of time.

In  rats Durbin, Scott and Hamilton,  1957, estimated the  bio-
logical half-life to be  about  200 days after an  intramuscular
injection of    Cd  ( 2  uCi per rat, compound not  stated).   They
did not determine whole  body retention, but determined cadmium
in  organs after 1,  8 and 64  days and  estimated also the  excretion
via faeces and urine for 64  days. If  an estimate  is made using
their data after  8  days  compared with 64 days, thus eliminating
the initial excretion phase, a biological half-life of about
300 days will be  obtained.

Burch and Walsh,  1959, estimated that in dogs, it would  take
260-500 days to eliminate 50 per cent of an intravenously  in-
jected dose of    Cd  as nitrate. Also experiments on goats
by  Miller, Blackmon and  Martin,  1966, indicate a  long biologi-
cal half-life of  cadmium.

The explanation is  not quite clear  for the different  half-lives
obtained after injection  in mice  and rats during  different  time
periods,  but it is  known that  initially, cadmium will mainly be
stored in the liver, and that  during  the first week,  more  cadmium
will be excreted  via  the gastrointestinal tract  than  during the

 following weeks.  Because  cadmium will  probably  be  bound  to  dif-
 ferent proteins  during  this  stage,  it  will  take some  time before
 a steady state is  obtained.  This is  supported by  the  fact that
 blood  levels of  cadmium will  increase  during the  first week
 (figure 4:5). Eventually  blood  and  liver  levels will  decrease
 and  renal levels  of cadmium  will increase.  As the  cadmium   accumu-
 lated  in the kidneys will not be noticeably excreted,this accumu-
 lation will prolong the biological  half-life. This  is illustrated
 by the results of  Gunn  and Gould, 1957, who found  that 150  days
 after  an intracardiac injection of     Cd  as nitrate,  the kidney
 was  still accumulating cadmium.

 The  above mentioned values for  biological half-lives  of  cadmium
 will only be valid before renal damage has  occurred.  If  there is
 renal  tubular dysfunction, the  excretion  of cadmium will increase
 and  this might considerably  change  the biological  half-life.

4.2.6  Cadmium metabolism in relation to zinc metabolism
It was  mentioned  in Chapter 3 that  cadmium will  appear together
with  zinc in nature and it could be  expected that uptake of zinc
could give  rise to an  uptake of cadmium.  Zinc is an essential
metal for animals and  human beings  (see e.g. Underwood,  1962,
Bowen,  1966 and:.Schroeder et al.,  1967)  and zinc deficiency
will  give rise to disease, with symptoms from skin, gonads  and
hematopoietic system.  As it was known that  zinc deficiency  in
animals would give rife to effects  on the gonads, Parlzek,   1957,
studied the influence  of a simultaneous administration of zinc
on the toxicity of cadmium.  He found that in rats a large dose
of zinc salt could prevent the action of cadmium on the testes
 (see  also section 6:6).  Similar findings have since been reported
by Kar, Das and Mukerji,  1960, Gunn, Gould  and  Anderson,  1961,
 1963a and b, Kar and Kamboj,  1964,  Mason and Young, 1967, and
 Gunn, Gould and Anderson,  1968a and b. Not  only the acute toxic
effects of cadmium on  the testes but also some  long-term effects

of cadmium may be prevented by simultaneous administration of
zinc. Vigliani,  1969, gave rabbits injections of cadmium chlor-
ide for several months and found that the degree of proteinuria
was less in rabbits treated with zinc. Powell et al., 1964, found
that oral exposure to cadmium produced parakeratosis in calves
similar to that caused by zinc deficiency. Petering, Johnson and
Stemmer, 1969, reported that typical symptoms of zinc deficiency
appeared in rats given a diet low in zinc and in rats given a
sufficient amount of zinc and an equimolar amount of cadmium. Hill
et al., 1963, Bunn and Matrone,  1966, and Banis et al., 1969, found
that some of the effects of cadmium, especially anemia and weight
loss, will be corrected by the administration of zinc in rats and
mice .
Sporn et al., 1969, gave groups  of rats  10 ppm cadmium, 80 ppm
zinc and 10 ppm cadmium + 80 ppm zinc in food for 60 days. They
determined the activities of 9 different enzymes in the liver.
They found, for example, that cadmium caused decreased GOT-activity
and that zinc given together with cadmium did not prevent this de-
crease. Cadmium caused a significant decrease in the oxidative
phosphorylotion  in the liver mitochondria and zinc prevented this
action of cadmium. Exposure to cadmium will tend to increase zinc
levels in organs (Gunn, Gould and Anderson, 1962, Bunn and Matrone,
1966, and Banis et al., 1969). This  is probably due to the greater
burden placed upon zinc to counteract the action of cadmium. Part
of this zinc will probably be found  in metaliothionein together
with cadmium, as this protein will normally contain equimolar
amounts of cadmium and zinc.

There is thus abundant evidence  that cadmium and zinc oppose each
other in animals. As many enzymes are zinc dependent, it is con-
ceivable that part of the toxic  action of cadmium will be caused
by an exchange with zinc in some enzymes.

4.2.7  Influence of other compounds on the metabolism of cadmium
Kar, Das and Mukerji, 1960 and Mason and Young, 1967, found
that selenium could protect the testes against damage by
large doses of cadmium (see  section 6.6).  Gunn,  Gould and
Anderson, 196Ba and b showed that though the uptake 'of cadmium
in the testes increased after the administration of selenium
dioxide, the testes were not damaged. Gunn, Gould and Anderson,
1968a, gave mice    Cd  as  chloride  (1.4  mg/kg) ,s . c An jection .
One group was also given a subcutaneous injection of selenium
dioxide. One hour after injection, the latter  group had
a blood level of cadmium 11 times higher than  that of the
group given cadmium alone. Organ distribution  was also influ-
enced. The group given selenium dioxide showed lower concen-
trations in liver and pancreas. There was no difference
in kidney levels. Parizek et al., 1969, found  a similar
increase in blood levels of cadmium in rats given 2.2 mg
Cd/kg and sodium selenite. Selenium given in the diet had
a similar effect. Selenite was more effective  than selenate.
By separating plasma proteins by gel filtration they found
a large amount of cadmium in macromolecular fraction in
the selenite treated animals.

Injection of cysteine has also been shown to change the transport
and distribution of cadmium. Gunn, Gould and Anderson, 1968a,
found that cysteine prevented testicular damage by cadmium  chloride
in mice while kidnay damage was made more prominent. One hour
                            i uy
after a single injection of    Cd given simultaneously with
cysteine, kidney levels of Cd were 30 times higher than
in a group given Cd alone. At first the blood  level of cadmium
was also higher, but 7 days after injection, the cysteine
treated animals had lower values than the group given Cd

4.2.6  Discussion of mechanisms for transport, distribution
       and excretion
In this section, an attempt will be made to explain some of
the mechanisms for transport, distribution and excretion of
cadmium against the background of the data presented in the
previous sections.

It is not known in what form cadmium is transported from the
lungs, the intestines or injection sites to various organs.
The studies by Perry and Erlanger, to be published, and Perry
et al.,,1970, showed that, in the first hours after intraperi-
toneal and intravenous injections, cadmium in blood was mainly
in the plasma and partly dialyzable. This may mean that the in-
itial uptake in the kidneys after injection is the result of
glomerular filtration and reabsorption in the tubules of low
molecular weight compounds. As will be discussed later, a sim-
ilar mechanism probably holds true later when cadmium in plasma
is bound to metallothionein.

There will be a rapid decrease in plasma levels of cadmium,
whereas blood cell levels will decrease slowly. About 24 hours
after injection cadmium in blood will be mainly in the cells. At
that time there is a change in metabolism. Cadmium concentrations
begin to increase in the red cells. In the liver cadmium appears
in a low molecular weight protein fraction, probably metallo-
thionein, the cadmium and zinc binding protein described by Ka'gi
and Vallee in 1960 and 1961. The many unique oroperties of this
protein are given in appendix 4 :1. Metal lothionein must play an
important role for cadmium metabolism, ooth in normal and in
chronically exposed animals, but as it probably does not exist
in amounts large enough to handle injected doses in acute expo-
sure, it will only to a minor degree be involved in the transport
of cadmium during the first hours after injection.

After oral exposure only a relatively small percentage of the
given dose is absorbed. The capability of the intestinal walls
to produce metallothionei n is not clear, but Starchier, 1969, has
found a low molecular weight protein  (m.w. around 10,000) in the
duodenal mucosa of the chicken. This  protein had the ability to
bind copper and was thought to be important for the transport
of this metal. Cadmium and zinc could displace the copper. A
similar protein was found in the duodenal mucosa of the rat
(Evans and Cornatzer, 1970) and in the duodenal mucosa of the
bovine (Evans, Majors and Cornatzer,  1970). This protein might
be identical with metallothionein. However, it is not clear
whether it is synthesized in the duodenal mucosa or if it orig-
inates from the liver. Piscator, 1964, found large amounts of
the protein in liver from exposed rabbits, but other organs
might also contribute, as Lucis, Shaikh and Embil, 1970, found
that human fibroblasts could produce  a similar protein.

That pretreatment with small doses of cadmium will prevent some
of the effects of a larger dose has been shown in several experiments
(Terhaar et al.,  1965, Ito and Sawauchi, 1966, the National
Institute of Industrial Health, Tokyo, 19ti9, and Nordberg, Lind
and Piscator, to  be published). This  finding is consistent with
an induction of cadmium-binding protein by the small dose which
can then bind a large cadmium dose.

Metallothionein is probably one of the proteins responsible for
cadmium transport in the blood, but other proteins must also
be involved.  Carlson and Friberg,  1957, found that hemoglobin
probably plays a  role in cadmium metabolism. This was discussed
by Piscator,  1963 and Axelsson and Piscator, 1966b, in connec-
tion with the finding that rabbits exposed to cadmium for longer
periods of time developed hemolytic anemia, and that the release of

cadmium-containing hemoglobin from the cells could be important

for metabolism of cadmium.

As Carlson and Friberg, 1957, found that about one-third of the

cadmium in hemolysate was dialyzable, cadmium could also .be in

a lower molecular weight form. Nordberg, Piscator and Nordberg
                                                         1 09
(unpublished data) found that in mice exposed to D.25 mg    Cd/kg

by subcutaneous injection, part of erythrocyte cadmium was in

a fraction, corresponding to metallothionein. As metallothionein

has a molecular weight  (about 7,000) low enough to permit it to

enter the erythrocyte membrane, it could have entered the ery-

throcyte that way or could have been synthesized in the cells.

In the plasma a small amount of cadmium was found both in high

molecular and low molecular weight fractions, the latter corre-

sponding to metallothionein.

It is thus possible for cadmium to appear in at least 3 forms:

1) bound to metallothionein, 2) bound to hemoglobin, and 3) bound

to hemoglobin-haptoglobin. Then it can also be expected that al-

bumin and zinc-dependent enzymes may bind it, probably depending

upon the degree of exposure. By using a chelating agent (CaDTPA),

Eybl, Sykora and Mertl, 1966a, found that the bond of Cd to hemo-

globin was weaker than  that of Cd to albumin.

The selective accumulation in the kidneys has been thought
to be due to reabsorption of metallothionein in the renal
tubules (Piscator, 1964a and 1956c). The possibility that cadmium
bound to hemoglobin released through hemolysis reaches the kid-
neys has been pointed out by Piscator and Axelsson, 1966b. As
metallothionein is of low molecular weight, the small amount of
free metallothionein in plasma can be expected to be cleared
completely. As proteins in normal kidneys are almost completely
reabsorbed, only trace  amounts of the protein can be expected in
the urine. When the kidney has become saturated with cadmium, the
reabsorption decreases  and tubular proteinuria appears (see sec-
tion If metallothionein is still filtered, less will be re-
absorbed and it could be expected to appear in urine. Nordberg and
Nordberg (unpublished data) have recently shown that this might
happen. They found a low molecular weight protein fraction contai-
ning cadmium in urine from mice given injections of cadmium chlo-
ride for 5 months.


In section 4:2 it has been shown that cadmium will be retained
to a high degree in animals, especially in the kidneys and
liver.  Accumulation of cadmium in man is unavoidable, as even
in non-polluted areas, cadmium will be found in food, air and
water,  often appearing together with zinc in the environment.
For practical reasons, "normal" concentrations of cadmium are
here defined as those found in human beings without known ex-
posure  to cadmium in industry or to excessive amounts in food,
water and ambient air.

4.3.1  Transport and distribution in blood
Little is known about transport of cadmium in human beings but
data from Lehnert (personal communication) indicate that more
cadmium is in the plasma than in the cells in persons without
known exposure to cadmium. He found a ratio between plasma and
cell levels of 1.9 with a mean level in whole blood of 0.35 jug/
100 ml  (n = 18). Cadmium was determined by atomic absorption
spectrophotometry after extraction.

As has  been discussed in Chapter 2, it is difficult to determine
accurately low concentrations of cadmium in biological material.
Results from several investigations during the last ten years,
in which methods such as neutron activation, atomic absorption
spectrophotometry after extraction of metal, or spectrographic
analysis with modern equipment have been used, have indicated
that the average normal level, both in whole blood and in serum,
is well below 1 yug/100 ml whole blood (see table 4:3). In these
studies, there are still relatively larpp discrenancies among
values  reported by different authors. To what extent this reflects

differences in analytical methods  or  in  actual  cadmium levels
is not known.
Apart from those  data  listed  in  table  4:3,  there are some
reports in which  considerably  higher values  have been stated.
Butt et al.,  1964,  thus  reported an  average  level of cadmium
in whole blood of 209 fug/100  ml  and  in serum,  41 jug/100 ml.
flertz et al.,  1968,  reported  average normal  levels of 25 yug/
100 ml in serum.  They  used  spectrographic methods.  It is not
possible here  to  discuss  the  validity  of their methods but it
can be mentioned  that  the  values are in the  same range as the
one reported  by Friberg  in  1952  and  1955 in  the blood from rab -
bits given large  doses of  cadmium {    Cd) by injections. The
rabbits had symptoms  of  intoxication (see section
They are also  considerably  higher than the values given in
table 4:3 for workers  exposed  in industry.  In  this report,
the -high values stated by  Butt et al.  and Mertz et al . are
considered to  be  too  high  to  be  acceptable as  valid data for
h uman be i ngs.

In exposed workers,  Lehnert (personal  communication) found
more cadmium  in cells  than  in  plasma.  At a mean blood level
of 4.1 ug/100  ml,  the  ratio of plasma  to cells was 0.5 (n=22)
which is in accordance with the  findings in  animal experiments:
cadmium will  be bound mainly  to  the  blood cells during expo-
sure. In table 4:3 some  data  on  cadmium concentrations in
blood or serum of exposed  workers are  shown, but as exposure
conditions are not fully  known,  they can only  be used for
demonstrating  that cadmium concentrations in exposed workers
are considerably  higher  than  in  "normals".

There will be  fluctuations  in  blood  levels of  cadmium. Rogen-
felt (personal communication)  has determined cadmium concen-

                                                            4- 43.
trations 3-6 times a year for three years in blood of 20 work-
ers exposed to cadmium oxide fumes in a Swedish factory pro-
ducing a copper cadmium alloy. Production has varied to a
large extent. When levels of cadmium in air have been measured,
they have-varied between 0.01-0.36 mg/m . In figure 4:13. it
is seen that during exposure cadmium concentrations in blood
from one worker varied between 5.3-9.1 jjg/100 ml (spectro-
graphic method, "normal" concentration 
data) found that in a  group of workers, who  had  not been  exposed
for 20 years to cadmium oxide dust  (this  group included workers
examined by Friberg,  1950), the mean  cadmium concentration  in
blood was 0.9 /ug/100 ml (n  =  18; spectropraphic  method,  "normal"
concentration  ^ 0.2 ^ug/100 ml).

4.3.2  In organs
4.3.2. 1  l.n_li.v§.r_aHc'_kiud£ey_
In contrast to blood,  urine and hair,  analysis of  cadmium in
liver and kidney from  adult humans  will give  accurate  results
with most methods, as  the concentrations  usually are  relatively
high and thus  interference  from other compounds  will  be negligible.
The basic work in  this field  has been done by Tipton,  Schroeder,
Perry and co-workers.  In a  series of  papers,  they  presented nor-
mal values for cadmium and  many other metals  in  organs of subjects
from the United States and  from other parts  of the world.  (Tipton
and Cook 1963, Tipton  1960, Perry et  al.  1961, Schroeder  and
Balassa 1961,  Tipton et al. 1965, and Schroeder  et al. 1967).
During recent  years, other  investigators  have also studied  this  •
problem  (in Sweden: Piscator, 1964,  and  Piscator  and Lind  (un-
published data;  in Germany:  Geldmacher-v. Mallinckrodt and Opitz,
1968, and Henke, Sachs and  Bonn, 1970;  in Japan:  Kitamura, Sumino
and Kamatani,  1970, Ishizaki, Fukushima and  Sakamoto,  1970b;  in
the United States: Morgan,  1969, and  in the  United Kingdom: Curry
and Knott, 1970).  Data on exposed workers have been reported  by
Friberg, 1950, 1957, Bonnell, 1955, Smith, Smith and  McCall,  1960,
Kazantzis  et  al., 1963 and Piscator  (unpublished  data).

As the tissue  concentrations  have been expressed in different
ways, i.e., ppm wet weight, dry weight or ash,   and as with
regard to renal concentrations some authors  have determined
cadmium in whole kidney and some in renal cortex,  conversion

factors have been used. For liver, the ash values have been
multiplied by 0.013 (Tipton and Cook, 1963) and the dry
weight values have been multiplied by 0.29 to obtain wet
weight values (Piscator, unpublished data). For kidney the
ash values have been multiplied by 0.011  (Tipton and Cook,
1963) and the dry weight values by 0.21 (Piscator, unpublished
data) to obtain wet weight values. Whole  kidney values have
been multiplied by 1.5  (Geldmacher-v. Mallinckrodt and Opitz,
1968) to obtain cortex concentrations.

As seen in some of the above mentioned papers, the ratio between
kidney and liver concentrations in normal human beings is usual-
ly between 10 and 15 in the United States, the United Kingdom
and Sweden, and between 5 and 10 in Japan. In exposed workers,
on the other hand, considerably lower ratios have been seen, and
sometimes liver levels have even exceeded kidney levels  (Smith,
Smith and McCall. 1960).

With regard to distribution within organs, Geldmacher v.-Mallin-
ckrodt and Opitz, 1968, found at autopsy  in 9 normal human beings
a mean ratio of 2.2 (1.9-3.0) for cadmium in renal cortex to
cadmium in medulla.  Smith, Smith and McCall, 1960, found ratios
of 1.1-1.4 in 3 controls. From the data of Ishizaki, Fukushima and
Sakamoto, 1970b,  and Kitamura, Sumino and Kamatani, 1970, it has
been calculated that the ratios between cadmium concentrations in
cortex and medulla were 2.3 (0.6-9.6) and 2.9 (1.3-6.3)  in adults.
In four exposed workers, who died 2-18 years after the last exposure,
the ratios were 1.2-1.6 (Smith, Smith and McCall, 1960).

In .figure 4:14 the data from investigations of cadmium in liver
(ppm wet weight)  in relation to age have been assembled  for
"normals" in different countries,  occupationally exposed work-
ers and Itai-itai patients. As can be seen, the values for "nor-

mals" in the United States,  the United  Kingdom  and  Sweden  are
comparatively  low  and  the  average  values  do  not  exceed  2 ppm wet
weight. The normal values  from  two Japanese  studies are consider-
ably hi'gher, particularly  the values  reported by  Ishizaki,  Fuku-
shima and Sakamoto, 1970b,  from the Kanazawa Prefecture, where
the values are  5-10 times  the values  for  the United States,
the United Kingdom and  Sweden.  Kanazawa,  regarded as  having
relatively low  levels  of cadmium  in rice,  is not  included  in
the present investigation  of areas in Japan  suspected  for  pol-
lution with cadmium. As the  cadmium concentrations  in  the  liver
of the newborn  are less than 0.002 ppm  (section,  it is
obvious that there is  an accumulation with age.

It should be pointed out that the  Swedish  and  American investi-
gations were based upon cases of  sudden death,  whereas  in  the
British and two Japanese investigations,  autopsies  from hospita-
lized patients  were used.  In these materials, the basic disease
and terminal illness will  influence the results.  Morgan,  1969,
has shown that  especially  cancer  will cause  increased  liver
concentrations  of  cadmium  (see  Chapter  7). This  factor, however,
could only to  a minor  degree explain  the  higher levels  in  Japanese
groups studied.

As can be seen, the liver  values  in figure 4:14  for the occupa-
tionally exposed workees and the  Itai-itai patients are high,
with no substantial observable  difference. It is  also  noticeable
that the upper level in "normals"  from  the Kanazawa Prefecture
is within the  range of the  values  in  those occupational ly  exposed.

Of considerable importance  is to  what extent the  values for the
exposed workers can be  regarded as representative for the  actual
values during  exposure, as  all  of the workers included  had been
without exposure for a considerable time  before  death.  In  figure

4:15 the  liver  values have been  plotted  against  the  passage, of time
after the end of  the exposure. In  this  figure  the  actual  exposure
times for the workers are given. Workers  exposed to  cadmium dust
are separated from workers exposed to  cadmium  oxide  fumes.  As  can
be seen,  there  is no tendency  for  the  liver values  to  decrease
substantially with the  time  from the end  of exposure in workers
exposed to  cadmium oxide  dust. This would mean that  the biologi-
cal half-life in  the liver of  human beings  subjected to this  type
of exposure  is  extremely  long, 'as  there  is  no  evidence  that those
without exposure  for only a  short  period  had had a  different  expo-
sure than those without exposure for a  longer  period.  For cadmium
oxide fumes  there might be a tendency  toward a faster  clearance,
.but in summary, it can  be said that the  liver  values,  in  any  case
for cadmium  dustt in figure  4:15 should be  fai,rly  representative
for the values  during exposure,  provided  that  the  clearance during
the very  first  year did not  differ considerably  from the  later

In figure 4:15, values  for renal cortex  (ppm wet weight)  in
relation  to  age are given. It  con  be seen that the  Swedish  and
British values  are the  lowest, but even  these  show  a consider-
able accumulation with  time. The values  from the Kanazawa Prefec-
ture are  the highest among the "normals",  with the  other  Japanese
group and the American  group in-between.  Those occupationally  ex-
posed are scattered over  a wide  range, with about  two-thirds
of the values over 100  ppm and the rest between  20  and  100  ppm.
Jhe reason  that the concentrations in  some  occupationally ex-
posed workers and in the  Itai-itai  patients are  even somewhat
lower than  in the "normals"  is discussed  in detail  in  sections
6.1.2 and If  renal damage is present,  cadmium excre-
'tion will increase and  renal levels of cadmium will  decrease.

Figure 4:16 shows  that  cadmium  has  been  accumulated with age
in all groups studied,  thus  supporting  the  findings of Schroeder
and Dalassa in  1961.  It  will  also  be  seen  that  after 50-60 years
of age, a decrease  in cadmium levels  has  taken  place.  At present,
it is very difficult  to  explain this  decrease.  It  might be con-
nected with factors  related  to  exposure  or  related to  metabolic
changes in kidneys  or other  organs  in old  age.   The slight increase
in urinary excretion  of  cadmium with  age,  described by Szadkowski,
Schaller and Lehnert  in  1969, supports  the  latter  possibility
(figure 4:17).

The transport to and  metabolism of  cadmium  in  renal cortex are
closely related to  zinc  metabolism,  as  pointed  out by  Schroeder,
1967. Analysis  of  human  renal  cortex  from  36  normal persons, aged
6-50  years, showed  an  equimolor increase  in  zinc  content with
increasing cadmium  levels  (Zn  = 1.13  Cd  +  2.33)  (Piscator and
Lind, unpublished  data).  The  basic  level of zinc in the kidneys
was not affected.  The molar  relationship between cadmium and
zinc under normal  circumstances is  1:1  in  metallothionein, which
is found in human  kidneys  (Pulido,  Kagi  and Vallee, 1966). It is
possible that the  equimolar  relationship between increases in
zinc and cadmium in  normal renal cortex  reflects the metallo-
thionein content.

4. 3.2.2  Other  £rg_an_s_
In the pancreas the  levels of cadmium irr "normals" are usually
below 2 ppm wet weight.  Tipton  and  Cook  in  1963  found a median
value of about  1 ppm  in  U.S.  citizens,  whereas  Tipton  et al. in
1965 found a median  value  of 2.8 ppm wet weight  in subjects from
the Far East. None  of the  presently available  data has related
cadmium in pancreas  to  age.  In  exposed  workers,  39-80  ppm wet
weight have been recorded  by Friberg  in  1957  and Smith, Smith and
McCall in 1960, and  in  Itai-itai patients,  45-65 ppm,  by Ishizaki,

Fukushima and Sakamoto in  1970b.

"Normal" concentrations of cadmium  in  the  lungs  have  been reported
by Tipton and Shafer in 1964.  In subjects  from San  Francisco,  they
found a mean level of 0.34 ppm wet  weight.  Molokhia and Smith  in
1967 found in 21 Scottish subjects  (40.-7U  years  old)  a  mean level
of 0.26 ppm wet weight and Smith, Smith  and McCall  in 1960 found in
3 British subjects (mean age:  54) a mean level of 0.71  ppm wet
weight. In Germany Geldmacher-v. Mai 1inckrodt  and Opitz in 1968
found a mean level of 0.11 ppm wet  weight  in subjects who were 3-
62 years of age.                      Cadmium levels in  the lungs
seem to increase with age. In  most  other organs  cadmium will  be
found, as Tipton and Cook, 1963, and  Smith,  Smith and McCall,  1950,
have attested, but there are not enough  data on  accumulation  with
regard to age to draw any. conclusions. Concerning cadmium concen-
trations in other organs, it can be  mentioned  that  Smith,  Smith and
McCall in 1960 and Friberg in  1957  found relatively large concen-
trations of cadmium (25-03 ppm wet  weight)  in  the thyroid in  cases
of chronic cadmium poisoning.  In bone, cadmium levels normally are
low, below 1 ppm with accumulation  with  age, as  found by Kitamura,
Sumino and Kamatani, 1970.

4.3.3  E xcretion §.x£rH.t.i.on_
Also with regard to urine there have  sometimes been big differ-
ences in reported normal concentrations,  but most reports during
the last ten years have stated an average  normal  excretion of
less than 5 jjg/day, and in most studies,  1-2 pg/day (table 4:4).
In some reports, such as those by Schroeder et al.,  1967,  and  by
Tipton and Stewart, 1970, considerably higher  figures have been
given, which can not be accepted. In  some  European  countries  and
in the United States,  the daily intake of  cadmium is  less than 50

    (see Chapter 3). Even  if  a  calculation  is  based  on  as  high an
absorption as  10 percent in the  alimentary  tract,  it  will  be  seen
that less than 5 yug/day will  be  absorbed. We  can  not  thus  expect
more than a. few micrograms  to be  excreted via  the  urine every day.
There seems to be a slight  increase  with age,  as  shown  by  Szadkowski,
Schaller and Lehnert,  1969, but  even in people around 60 years of
age, cadmium excretion is  still  very low, as  illustrated in figure
4: 17.

Cadmium excretion in exposed  workers has been  extensively  studied
and documented by Truhaut  and Doudene,  1954,  Bonnell, 1955, Smith,
Kench and Lane, 1955,  Smith and  Kench,  1957,  Kazantzis  et  al.,1963,
Suzuki, Suzuki and Ashizawa,  1965, Tsuchiya,  19G7  and 1969, Adams,
Harrison and Scott, 1969,  and Lehnert  et al.,  1969.  It  will be seen
in table 4:5 that during exposure, cadmium  excretion  will  vary from
near zero to around 1  mg/day.
In several of  the above mentioned reports it  will  be  seen  that
exposure to cadmium has taken place  without  resulting in an in-
crease in urinary excretion of  cadmium. Tsuchiya,  1957,  found
that workers exposed to cadmium  oxide  fumes,  about 0.1  >ug/m ,
for less than  one year, did not  excrete more  cadmium than  con-
trols. In 1969 he found that  blood levels varied  between 1 and
10 /ug/100 ml in a group of 20 workers  in an  alkaline  battery  fac-
tory, indicating that  cadmium had been absorbed and  accumulated.
In two of these workers, urinary  excretion  of  cadmium was  1 xjg/l»
.. i.e., within normal limits.

Adams, Harrison and Scott,  1969,  determined  urinary  cadmium in
75 workers in  different departments  in an alkaline battery fac-
tory. In the assembly  department,  where cadmium concentrations
in air had been measured at around 0.1  mg/m  since 1957 and in
in the plate-making department,  where  concentrations  of cadmium
in air had varied between  0.1 and 0.5  mg/m  ,  9 out of 51 men  ex-

creted less than 2 yug/1'. Ten workers had proteinuria and excreted
30-170 /Jg/1•  The workers without increased excretion of cadmium
had thus been exposed for several years to aadmium concentrations
known to cause considerable accumulation of cadmium. They had no
proteinuria,  and it is conceivable that their renal levels of
cadmium had not yet reached the point at which renal damage
occurs and cadmium excretion begins. That during exposure ex-
cessive amounts of cadmium may be absorbed without an increase
in excretion of cadmium is in accordance with the findings in
animal experiments described in section

An increase in cadmium excretion has been reported in workers
without detected proteinuria by Smith and Kench, 1957, and Adams,
Harrison and Scott, 1969,  but it should be remembered that for
the determination of cadmium, quantitative methods were used,
whereas semiquantitatiVR methods were used for the determination
of urinary protein.

When proteinuria is present, there is always an increase in the
excretion of cadmium, which is also in accordance with the re-
sults from animal experiments (section   It has not been
possible to relate excretion of cadmium to excretion of protein
(Smith, Kench and Lane, 1955, and Smith and Kench, 1957).

After exposure has ceased, cadmium excretion will decrease,
whereas proteinuria will persist (see also section
Adams, Harrison and Scott, 1969, found that in a group of
workers under exposure and with proteinuria, the mean excre-
tion of cadmium was 94 ^ug/1, whereas in a group of retired work-
ers (not exposed for 0.5-5 years) with proteinuria, the mean
concentration of cadmium in urine was 28 yug/1.

Tsuchiya, 1969, determined urinary cadmium in three workers
at the time they were removed from exposure to cadmium and

 one  year later.  In one worker there was a decrease' from about
 250  to  125  Ajg/1,  whereas in the other two workers, cadmium
 excretion was  at  both times about 100 yug/1.

 Bonnell,  Kazantzis and King, 1959, found that urinary excretion
 of cadmium  could  be affected by general health. Acute illnesses,
 such  as  pneumothorax and pneumonia caused considerable increases
 in excretion  of cadmium. Terminal illnesses will also increase
 excretion as  pointed out by Smith, Smith and McCall, I960.

 The  relationship  between cadmium excretion and zinc metabolism
 has  been illustrated by the findings of Suzuki, Suzuki and
 Ashizawa,  1965.  They observed a decrease in the excretion of
 zinc  with an  increasing excretion of cadmium.

 4.3. 3.2   Fe£al_ £x£re_t^_o£
 Fecal excretion of cadmium has been determined in normal human
 beings  by Essing  et al., 1969, who found a mean level of 16
yug/100  g (  n  = 23). They estimated the daily amount in feces
 to be 31  ijg.  Tipton and Stewart,  1970, found a mean amount of
 42 jug/day in  3 persons in a long-term balance study. Tsuchiya,
 1969, found a  mean daily amount of 57 Lig in feces from 4
 3apanese men.  No  known excessive exposure was stated. It is
 not  known how  much cadmium will come from cadmium not ab-
 sorbed  from food  and how much will have been excreted via the
 intestines. It is also not known if cadmium excreted into the
 gastrointestinal  tract will be reabsorbed. Data from injection
 experiments on animals suggest that only a few per.cent : of the
 absorbed cadmium  will be excreted via feces.   Excretion via hair
 During the last years, the possibility of using hair as an  in-
 dicator of exposure has been investigated, as seen in table 4:6.

Analysis of metals in hair is difficult, as external contamination
both from dust and from metals in hair  lotions, hair sprays, etc.,
must be taken in account.

In the study by Schroeder and Mason, 1969, the influences of sex,
age and color of hair on the levels of  cadmium in hair were in-
vestigated. They found that male black  hair contained less cadmium
than brown, blonde or red hair. In women, grey hair contained less
cadmium than hair with natural color. Their data indicate that cad-
mium levels in hair are higher in the particular area investigated
(Brattleboro, Vermont) than in Stockholm, Sweden, and can be con-
sistent with the fact that organ levels of cadmium seem to be high-
er in the United States than in Europe.

Ishizaki, Fukushima and Sakamoto, 19G9, determined cadmium in
                      abovn -.ih years o.r age;
hair from men and women,from the endemic district of the Itai-
itai disease. They found mean concentrations of about 0.4 and
0.7 ppm, respectively. There were, however, no controls for
the men. There were only 3 controls for the women and they
had a mean concentration in hair of about 0.4 ppm.

Hammer et al., 1970, investigated 10 year-old children living
in areas with varying degrees of pollution. They found good
agreement between exposure levels and hair levels of cadmium.

In exposed workers, hair analysis will be of little value, as
external contamination will be great. Analysis of metals in
hair is a relatively new field. More information is needed about
the chemistry of hair, pre-analysis treatment and significance
of levels in hair in relation to organ  levels before the value of
cadmium analysis of hair can be ascertained.

4.3.4  Total body burden anri_ renal burden.

A "standard American" of 70  kg and about  50 years of age has
accumulated about 30 mg of cadmium as estimated by Schroecler
and Balassa, 1961, and Schroeder et al.f  1967, using the data
by Tipton and Cook, 1963, on cadmium concentrations in human
tissues. About one third of  the cadmium  is in the kidneys and
about 15 percent  in the liver. About half of the total body
burden of cadmium will thus  be found in  liver and kidneys to-.

Apart from  the abovementioned data there  is only one report
based on actual findings from which it is possible to get an
estimate of total body burden in normal  human beings. Smith,
Smith and McCall, 1960, determined cadmium in organs from 3
men about 50 years of age without known  exposure to cadmium.
Analysis was made of liver,  kidney, skin, muscle, stomach,
colon, heart etc.  From their data the following moan amounts
of cadmium  in different organs can be calculated. Liver: 3.9 mg,
Kidney: 4.1 mg. Muscle: 3.3  mg, Skin: 0.4 mg, Stomach and Colon:
0.6 mg,  ..  Those make a total of 14.5 mg, and the renal per-
centage of  total  cadmium was about 28 percent. About 55 percent
of total body burden was in  kidneys and  liver together.

Using the above.-mentioned estimate, that  half of the body burden
is in liver and kidneys, a corresponding  "standard man" in the
United Kingdom and Sweden would accumulate about 15-20 mg of
cadmium. This estimation is  based on data on concentration of cad-
mium in liver and kidney by  Curry and Knott,  1970,  Pisc-.ator and Line
to be published and Piscator, unpublished data, and on an assump-
tion of average liver and kidney weights  of 1,700 and 300 grams,
respectively. Similar estimates based on  the data from Kanazawa
in Japan (Ishizaki, Fukushima and Sakamoto, 1970) will give an

 "Lung: 0.7 mg. Bone marrow:  0.5 mg. Other organs: About 1 mg.

average total body burden of about  00 mg  in  a  Japanese  person  of
70 kg and 50 years of age in that  area.  If  data  from Kobe,  Japan,
are used instead  (Kitamura, personal communication), the  average
body burden will be lower, about 40 mg.  It  should  be remembered,
however, that body weights and thus also organ weights  in Japan
are lower than in Europe and the United  States.

If organ values are to be used to  calculate total  body  burden in
human beings during exposure to large  concentrations of cadmium
via inhalation or ingestion, the above mentioned proportions  can
not be used. During or immediately after exposure,  but  before
renal damage has occurred with increased excretion  of  cadmium,
the liver contains considerably more cadmium  than  the  kidneys.
This is shown by  the animal experiments  of  Decker  et al.,  1958.

Animal experiments have furthnr shown  thot  during  repeated  ex-
posure about 75 percent of the total administered  dose  will be
found in liver and kidneys before  renal  damage occurs  (Friberg,
1952, and Axelsson and Piscator, 1S6Ga). As excretion  during  that
period will be only a few percent  of the dose, the  amount of  cad-
mium in liver and kidney will be about 75 percent  of the  total
body burden. The main part will be in  the liver  and only  5-10
percent of the total body burden will  be in the ,kidneys.

There is no reason that human beings should differ much from  animals
in this respect. For calculating the total  body  burden  in a worker
during exposure before renal damage has  occurred,  it can  thus be
assumed that the amount of cadmium in  liver and  kidneys together
will be about 75 percent of the total  body  burden.  The  same would
probably hold true for people exposed  to excessive  amounts  of cad-
mium via the peroral route.

With regard to body burden  in workers  several  years  after exposure,
only the data by Smith, Smith and  McCall,  19GO,  lend themselves  to
a calculation of total body burden.  They  determined  cadmium in
most organs, including muscle, skin  and  fat.  In  three  workers with
slight renal dysfunction, autopsied  5-10  years after the  last ex-
posure, it was estimated  that between  40  and  70  percent of the  total
cadmium accumulation was  in liver  and  kidneys  together, about  10 per-
cent in the  kidneys.

In figures 4:14 and 4:16  liver and renal concentrations of cadmium
at autopsy of exposed workers are  shown  (see  also  table 6:1). With
assumed liver and  kidney  weights of  1,700 and  300  grams,  respective-
ly, the total amount of cadmium  in these  workers  in  liver and kidney
would have been between 50  and GOO mg. With  [50 percent of the cadmium
in liver and kidneys, the total  body burdan  at tims  of death would
have been  100-1,200 mg. Total body burden at  tho  time  exposure  ceased
must have  been higher as  excretion of  cadmium due  to renal disease
must have  caused losses of  cadmium.

Of special interest is the  percentage  in  the  kidneys of  the total
body burden of cadmium, as  such  data are  necessary  for a  later  dis-
cussion (see section, with  rrgard to- intake of cadmium and
critical levels in kidney.  In normal human beings  the  kidney contains
about one-third of the total cadmium,  whereas  in  workers  exposed to
high concentrations of cadmium oxide fumes for less  than  10 years
and with sufficient renal cortex concentrations  of  cadmium (about
300 ppm) to have caused slight renal damage,  about  10  percent of
the total  body burden has been found in  the'kidneys. It could thus  be
suspected  that the percentage of renal cadmium decreases  with  in-
creasing renal concentrations. Data  from investigations in the  United
States (Schroeder  and Balassa, 1961) and  in  Sweden  (Piscator,  un-
published  data) show that in people  2Q-59  years  of  age the ratios
between cadmium concentrations in  liver  and  renal  cortex  are about

 0.06  at  a  mean  concentration  of 20 and 30 ppm, respectively. Corre-
 sponding calculations  based on the data by Ishizaki,  Fukushima and
 Sakamoto,  1970b,  and  Kitamura, Sumino and Kamatani, 1970, in Japan
 give  ratios  of  about  0.11  at  mean renal cortex concentrations of about
 42  and  87  ppm,  respectively.  There could thus be a slight tendency for
 an  increase  in  ratio  with  increasing renal concentrations, but it
 should  be  remembered  that  the U.S. and Swedish data were obtained
 by  analysis  of  cases  of sudden death, whereas the Japanese results
 were  from  investigations of hospitalized patients who died from
 severe  diseases,  which might  have changed the ratios. To obtain
 a more  homogenous material covering a large concentration range,
 cadmium has  been  determined in liver and kidney cortex of slaughtered
 horses  mainly between 10 and  20 years of age and without known
 disease  (Piscator,  unpublished data). In figure 4:1B it will be
 seen  that  there is  no changn  in ratio with increasing renal con-
 centrations,  even as  high  as  100-250 ppm. It can thus be assumed
 that  during  prolonged exposure to relatively small amounts of
 cadmium and  before  renal dysfunction has appeared, the relative
 amount  of  cadmium in  the kidneys will be about the same at both
 high  and low  renal  concentrations of cadmium.

In summary  it can be stated that  in  a  "standard  man"  about  50
percent of the  total body  burden  is  in  liver  and  kidneys.  The
total body  burden in a  "standard  man"  in  the  United States  is
probably about  30 rr.g of  cadmium.  The  corresponding  values  for
the  United Kingdom and Sweden  are  probably  about  15-20  mg.
In Japan the total body,  burden  is  considerably higher,  in  one
area (considered  not to  have an excessive  exposure  to cadmium)
it could be estimated to be about  80  mg.

For workers during exposure to  cadmium,  a  higher  percentage  of
the  total body burden is probably  in  the  liver and  kidneys.
Animal experiments indicate about  75 percent  before renal  damage
occurs.  Considerable time  after cessation  of  exposure and when

renal damage is evident, the total amount of cadmium in the  liver
and kidneys is lower, probably around 50 percent of the total body
burden. In autopsies of workers with exposure to cadmium and with
signs of intoxication, total body burdens of 100-1,200 mg of cadmium
have been estimated. Total body burden at the time exposure  ceased
must havs been higher, as excretion of cadmium due to  renal dis-
ease must have caused losses of Cc3drnium. During prolonged expo-
sure to small amounts of cadmium and before renal dysfunction has
appeared, renal cadmium will constitute about one-third of  the
total body burden.

As it is of great importance to know to what extent deter-
mination of cadmium in blood or urine may be of assistance
in making an estimate of cadmium concentrations in organs
and total body burden, this question will be discussed in the
following sections.

4.4^1  Relationship between concentrations of cadmium in blood
       and organs  In animals
As mentioned in section, the concentration of cad-
mium in the blood of experimental animals given a single in-
jection of the metal salt displays a two-phase course during
the first two days after injection. As this course is not re-
flected in other organs, it is evident that blood values do
not depict the situation in any body organs during this first
period. Even if the elimination phase counted from the second
maximum seems to be slower, available data indicate that it
is considerably faster than the elimination, both from whole
body and critical organs. However, more data on these relation-
ships are necessary before any definite conclusions can be

Data from repeated exposure are scarce. Most of the avail-
able evidence is from Friberg, 1952 and 1955, and show that
blood concentrations increase continuously during continuous
exposure to cadmium - but only to a certain level. No estima-
tions of blood/organ concentrations or blood/whole body con-
centrations are available for different exposure levels.There
also are no data which elucidate to what extent fluctuations
in exposure are reflected in fluctuations in blood and organ

4.4,1 .2  In_hymanp.beings
The data which have been presented do show that blood levels of
cadmium in exposed workers might be considerably higher than in
people without known exposure to cadmium. There will be fluctu-
ations in blood levels of cadmium, possibly reflecting fluctu-
ations in recent exposure.

In a Swedish factory it was  found  (Piscator, unpublished data)
that amoung a group of 7 carpenters and  repairmen who had been
employed for more than 20 years but not  directly exposed to cad-
mium, two men had renal damage at  blood  levels of 2.1 and 3.1
jjg/100 ml blood, whereas two workers in  the cadmium department
with 3-4 years exposure had  cadmium concentrations in blood of
4.8 and 5.8 >jg/100 ml blood without any  renal damage. A low value
for cadmium in blood thus doer, not exclude a considerable accu-
mulation in the kidneys and  a hij',h value does not necessarily
mean that renal damage has occurred.

Piscator (unpublished data)  found  that in a group of workers
not exposed for 20 years, urinary  excretion of protein was re-
lated to cadmium concentrations in blood ( f i gure ' 4 : 19 ) . It had
earlier been shown (Piscator, 19C2a) that in these workers pro-
teinuria was related to exposure time, i.e., the larger .the ab-
sorbed and accumulated amount, the greater the renal  dysfunction.
That a correlation could be  found  between cadmium in blood and
proteinuria indicates that the blood levels reflected organ le-
vels in these workers when they were without exposure for sev-
eral years.

4.4.2  Relationship between  concentrations of cadmium in
       urine and or^an or blood concentrations   nan
After a single  injection  of  cadmium,  not  more  than  a  few  percent
will be excreted  during  the  first weeks.  During  that  period  levels

of cadmium in blood will both increase and decrease. Liver con-
centrations will slowly decrease and renal levels will increase.
Urinary excretion of cadmium is not related  to any of the above
mentioned changes in blood or organ concentrations. After repeated
exposure urinary excretion will be low for long periods of time,
during which levels in blood and organs will increase continuously,
A low concentration of cadmium in urine can  thus be associated
with both high and low concentrations of cadmium in organs or
in blood.

The simultaneous occurrence of proteinuria and increased excretion
of cadmium as shown by Friberg, 1952 and Axelsson and Piscator,
1966a, indicate there is a common mechanism  for the two para-
meters. Proteinuria during exposure to cadmium is a sign of  renal
tubular dysfunction (see section G.1.2.3).

Axelsson and Piscator, 19GGb, found alco that whereas there  was
no association between renal levels of cadmium and urinary excre-
tion of cadmium in rabbits subjected to repeated exposure, there
were significant negative correlations between excretion of  cad-
mium and renal tubular capacity to reabsorb  glucose and renal
activity of alkaline phosphatase. These results and the relation-
ship between proteinuria and cadmium excretion indicate that once
cadmium starts being excreted, the amount excreted will reflect
more the functional state of the kidney. Thus, the cadmium excre-
tion in itself will be a measure of renal function during expo-
sure rather than a measure of organ concentrations. The mechanisms
for this will be further discussed in section
4.4.2 .2  Inhjmanbei
Cadmium will accumulate in liver and kidneys from birth  up  to
50 years of age. Whereas the newborn has only about  1 yjg or
less in his body, the "normal" adult may have a total body  bur-

den of about  30  mg.  With  increase  in  age',  there  seems  to  be  a
slight increase  in  cadmium excretion.  Urinary  excretion  of cad-
mium  is  very  low all  of the tiiw,  however,  usually  less  than 2
/jg/day.  It  is  at pro-sent  not  possible  to  say  if  this  increase
parallels the  increase  in renal  levels.
The  findings' in  exposed  workers  confirm the  findings  in animal
experiments.  During  a  considerable  time,  the length of which
depends  on  exposure  conditions,  urinary excretion of cadmium
will be  within normal  levels.  Whon  rtjnal  damage  with proteinuria
and  other  functional  abnormalities  occurs,  there will also be in-
creased  excretion  of cadmium (sets section

Ts uchiy a/ dete'rrni ned  cadmium in blood and  in  urine in three groups
of workers.  One  control  group  (n =  9)   in an alloy factory,  not
directly exposed  to  cadmium,  ono group (n =  11)  exposed to cad-
mium oxide  fumes  in  the  alloy  factory, and one group (n = 20)
in an  alkaline accumulator factory  exposed to cadmium oxide  dust
were examined. In  the  control  group and in the group exposed
to cadmium  oxide  dust, blood concentrations  of cadmium varied
between  0.2  and  4 ^jg/100 ml and between 3 and- 7  /jg/100 ml, re-
spectively.  Corresponding values for urinary excretion were
2-10 and • 1-40 /ig/1.  In these, two groups there were no correlations
between  cadmium  concentrations in urine and  blood. In the
group  exposed to  cadmium oxide fume, blood levels were between
10-35  LJg/100  ml  and  urinary cadmium between  10-230 t-'/l. As
all  workers  showed an  increase in cadmium excretion,  it is
conceivable  that  all  had renal dysfunction.   In  that group
a correlation (  p  <^  0.05) was  found between blood levels
and  urinary  levels of  cadmium.

Tsuchiya's  data  thus  show no uniform findings in the three groups
with regard  to relationships between blood levels and urine  levels.

High levels of cadmium in blood may be  combined  with  low  urinary
concentrations of cadmium.

4.4.3  Conclusions
There are  thus no data which  shovv  that  concentrations of  cadmium
in blood or urine can be  usuri  for  estimating organ levels of cad-
mi urn in human beings. It  cannot be  recommended that  any fixed
level in blood or urine can he used  for control  of exposed
workers or populations exposed to  cadmium in food or ambient
air. Concentrations  of cadmium in  urine above "normal" would
indicate that signs  of cadmium induced  runal dysfunction  had
already occurred, provided  other  reasons  for the increased ex-
cretion could not be  demonstrated.

4.5.1.   In animals
The fate of cadmium in experimental animals  has  been  studied
after exposure via the respiratory, gastrointestinal  or injec-
tion  routes.  Absorption rates are not  known  exactly  with regard
to inhaled or ingested cadmium, but reasonable estimates  are about
10-40 and  2 percent, respectively. The  absorption of  ingested
cadmium may increase considerably  if  the  diet  is  deficient in
calcium and/or protein.  There are  also  considerable  individual
variations .

In blood,   cadmium has been studied after  single  and  repeated in-
jections.   After a single injection cadmium will  initially be
mainly  in   the  plasma, but during the  first 24  hours  after injec-
tion, a rapid  clearance  from plasma takes place,  so  that  eventu-
ally the concentration in the cells will  exceed  that  in the

After repeated exposure cadmium will mainly be1 ,found in the
blood cells, bound to proteins, such as metallothionein and
hemoglobin. During continuous exposure to cadmium, there
will be a continuous increase in blood levels of cadmium,
but at a certain level, a plateau will be reached and no 'fur-
ther increase will be seen. When exposure has ceased, the con-
centration in blood will decrease.

About 75 percent of the cadmium will be found in liver and kid-
neys together .before the occurrence of some rsnal damage. Imme-
diately after single exposure, the main part will be in the  liver,
but eventually renal levels will exceed liver levels. Repeated
exposure to small amounts will also result in the renal concen-
trations surpassing the liver concentrations, but with increasing
doses, liver concentrations will exceed renal concentrations.

In the kidney the highest concentrations of cadmium will be
found in the cortex. It is possible that it is transported to
the cortex with metallothionein. During exposure there will  be
a continuous accumulation of cadmium in the kidnnys and urinary
excretionfw"iTitTe low. When the cadmium level in the kidneys
reaches about 200-300 ppm wet weight (or about 400 ppm wet weight
in the cortex) , there will be no further increase and urinary
excretion of cadmium will increase considerably. As proteinuria
occurs at this time, this change in metabolism is thought
to be due to the renal tubular dysfunction. Whereas before
renal damage has appeared, the total excretion via urine,
feces and other routes will be less than 10 percent of the
daily administered dose, daily excretion may exceed the daily
dose after renal damage has appeared.

The biological half-life of cadmium after single oral exposure
has been estimated to be about 200 days in mice. After single in-

tramuscular injection the half-life  has  been  estimated  to  be
about 200 days in rats. If the  initial  clearance  during the  first
week is. not taken into account,  the  half-life  can be  estimated
to be 300 days. After single  intravenous  injection a  half-life of
about 400 days has been estimated  in  dogs,  including  the initial

The metabolism of cadmium is  intimately  connected with  zinc  meta-
bolism. The low molecular weight protein,  metallothionein,  is  able
to bind both cadmium and zinc,  and these  two  metals will thus  be
transported together. Zinc is an essential  metal  and  many  enzymes
are zinc-dependent. Cadmium seems  to  have  the  ability to exchange
with zinc and thus cause changes in  enzymatic  activity.  During
exposure to cadmium, organ levels  of  zinc  will  increase.

4.5.2  In human beings
Cadmium may be absorbed after inp.estion or inhalation of cad-
mium compounds, but  theru  are no experimental data at present
that allow  any conclusions  to be drawn  with regard to absorption
rates  in human beings.  Estimations starting from body burdens
found  at autopsies  together with estimated intake of  cadmium
in  the past point,  however,  to  an  average absorption  via the
oral route  of  somewhere between 3  and 8 percent.  Based  on the
animal data, an absorption  rate of about 10 percent of ingested
cadmium must be considered  quite possible in individual cases,
under  certain  circumstances  such  as calcium and protein de-

The  newborn contains  less  than  1 ug  of  cadmium, indicating that
the  placenta is an  effective  barrier to cadmium.

Normal concentrations  of  cadmium in  blood will be well  below  1
ijg/100 ml blood.  In  exposed workers  considerably higher values
have been reported,  usually between  1 and 10 ^ug/100 ml. In ex-

posed workers cadmium will be found mainly in the blood cells.
After exposure has ceased, concentrations of cadmium in blood
will decrease slowly.

In normal human beings the largest concentrations of cadmium
will be found in the kidneys. This accumulation in the kidneys
reaches its maximum when a person is around 50 years of age,
when mean concentrations in  the renal cortox have been shown to
be 20-50 ppm wet weight in persons living in the United Kingdom,
the United States and Sweden. In older persons, lower values are
seen. In two areas in Japan ./'normal levels of around 50 and 9D
ppm, respectively, have been found in the cortex.

In exposed workers concentrations of around 300 ppm have been
found in the cortex, but values within the normal range have also
been reported despite signs  of cadmium intoxication. Losses of
cadmium, due to renal dysfunction, are thought to be the cause
of  these low values.

In normal human beings in the United Kingdom, Sweden and the
United States, the .concentration in the  kidneys is often 10-15
times higher than that in the liver, and in normal Japanese
persons, 5-10 times higher,  whereas in workers exposed to cad-
mium, the ratio is still smaller and in  some cases liver con-
centrations of cadmium have  exceeded the renal levels. The
pancreas may contain high concentrations of cadmium.

As in animals, cadmium metabolism in humans will be intimately
related to zinc metabolism.  When cadmium is accumulated in  the
kidneys, .there will be a corresponding molar increase in renal
concentrations of zinc. The  cadmium and  zinc-binding protein,
metallothionein, has been found in normal human kidneys and
metallothionein probably plays an important role in the meta-

bolism of cadmium in human beings.

In normal human beings, the excretion  of  cadmium  via  the  urine
is very low, around 2 pg/day or  less.  There  is  a  slight  increase
in excretion with age. It ir, not known to what  extent  excretion
via the gastrointestinal tract plays a role  for the human  meta-
bolism of cadmium, but if the human being reacts  in the  same
way as animals, less than 5 percent of an absorbed dose  can be
expected to be excreted via fcces. Small  amounts  of cadmium
might also be excreted via hair, skin, sweat, etc., but  the to-
tal excretion will probably be much less  than 10  perceat of
an absorbed dose.

During occupational exposure to  cadmium,  a worker's excretion
of cadmium  via urine might for somH time  be  within normal  limits,
but sooner  or  later it will increase considerably. Proteinuria
in cadmium  workers is always combined  with increased  excretion
of cadmium  during exposure, indicating that  renal tubular  dys-
function plays a  role in the increased excretion. After  expo-
sure has ceased,  less cadmium will be  excreted, but the  normal
level will  not be reached.

Available data do not lend themselves  to  an  estimate  of  the
biological  half-life of cadmium  in man, but  as  the biological
half-life in such small animals  as mice and  rats  is 200  days
or more, it is conceivable that  cadmium will  be retained for
many years  in  man once it has been absorbed.  This is  supported
by findings in autopsies of workers which indicate a  very  slow
decrease in liver levels after exposure ceased. Renal  damage
will change the metabolism of cadmium  and shorten the  half-

As cadmium  concentrations in blood during exposure will  vary
independently  of renal concentrations of cadmium, the deter-

mination of cadmium in blood will be of limited assistance for
making an estimate of renal concentrations.

The determination of cadmium in urine will not be of any value
in investigations of suspected renal accumulation, as during the
period of accumulation before the occurrence of renal damage,
cadmium excretion will be within normal limits. Concentrations of
cadmium above "normal" would indicate that signs of renal-induced
dysfunction are already present, provided other reasons for the
increased excretion could not be demonstrated.

                        APPENDIX 4: 1.


In 1957 Margoshes and Vallee reported that equine renal cortex
possessed a cadmium-containing protein of low molecular weight.
Further work by Ka'gi and Vallee, 1960 and 1961, resulted in the
purification of a protein with a molecular weight around 10,000,
which they named metallothionein becuase of its high content
of metals, such as cadmium and zinc, and of sulphur.

This protein had many unique properties. In contrast to most
other proteins, metallothionein absorbed UV-light of a wave-
length of 250 nm, but not of 280 nm. The absence of amino
acids, suggested by the lack of absorption at 280 nm, was
verified by amino acid analysis. The absorption at 250 nm was
shown to be dependent on the cadmium-mercaptide bond by the
following procedure: The protein was dialyzed at a low pH or
against EDTA whereby a metal free protein, thionein, was ob-
tained. Thionein did not have any absorption at 250 nm because
the cadmium mercaptide bond had disappeared. Addition of cad-
mium or zinc to thionein gave cadmiumthionein and zincthionein,
respectively. By such addition the cadmium mercaptide bond
was reestablished in the cadmium thionein and the absorption
at 250 nm reappeared.

The amino acid analysis showed that the high sulphur content,
about 9 percent, was due to a very high percentage of cysteine
in the protein. In metallothionein obtained from horse kidney,
the cadmium content was 5.9 percent and the zinc content, about
2.2 percent.

Proteins almost identical with matallothionein from horse
kidney have been isolated and characterized from the liver
of cadmium exposed rabbits (Piscator, 1964, Kagi and Piscator,
to be published, and Nordberg et al., to be published), and
from human renal cortex (Pulido, Kagi and Vallee, 1966). Also
from the liver of horses a protein has been isolated which is
identical with horse kidney metal lothionein in its ami no acid
composition and in several other characteristics, but which has
mainly zinc bound to it (Kagi,  1970). Zinc constituted more
than 90 percent of the total metal content of this "hepatic
metallothionein" which contained 11 percent sulphur, corre-
sponding to 33 percent of thionein made up by cysteine. The
molecular weight was estimated  to be about 6,600, i.e., lower
than earlier mentioned values.  The ratio of cysteinyl resi-
dues to zinc was 3 and Kagi suggested that a negatively charged
complex had been formed CZn
In addition to the studies mentioned above, there are some
other reports of similar proteins in organs from other animals,
i.e., cadmium exposed rats and mice (Shaikh and Lucis, 1969,
Nordberg, Piscator and Lind, to be published) in, the rat liver
and kidney  (Wisniewska-Knypl and Jablonska, 1970 , in the
duodenum of the chicken (Starcher, 1969), of the rat (Evans and
Cor-;natzer. 1970) and of the bovine (Evans, Majors and Cornatzer,

Metals  other  than  cadmium  and  zinc can  be  bound  by metallo-
thionein.  Pulido,  Kagi  and Vallee,  1966,  found that  renal
metallothionein  from human beings  treated  with mercurial  di-
uretics  contained  mercury. By  experiments  with equine  metallo-
thionein,  Kagi  and  Vallee, 1961,  showed that  the bond  between
metallothionein  and mercury was  stronger than  the  one  to  cad-

mium, which in turn is about 3,000times stronger than the one
to zinc. Jabubowski, Piotrowski and Trojanowska, 1970, found
                                                       20 3
that part of the renal mercury from rats injected with    HgCl_
was in a low molecular weight protein, which had characteristics
in common with metallothionein.
A protein similar to metallothionein but containing mainly
copper was found in duodenum of different species (Starcher,
1969, and Evans, Majors and Cornatzer, 1970). Both zinc and
cadmium, however, could displace the copper bound to this

It is not known to what extent the above mentioned proteins
which bind the different metals are identical, but all con-
tained a lot of metal and were of low molecular weight. Thus
it is highly probable that they play an important role for
the absorption, transport and excretion of metals, especially
cadmium. It is of interest in this connection that a low mole-
cular weight substance, possibly metallothionein, binds an im-
portant part of cadmium in blood of mice exposed to this
metal (Nordberg, Piscator and Nordberg, unpublished data).

The importance of metallothionein for absorption, transport,
excretion and toxicity of cadmium has been discussed else-
where in this report (section 4.2.1) and will not be dealt
with further here.

                OF  WET WEIGHT OF THE RIGHT TIBIAX (from
                Larsson and Piscator,  to be published).

Group n
Cd + Ca 6
Cd - Ca 6
- Ca 6
Controls 6
CdyUg/g dry weight
mean and standard
de vi at ion

Renal. Cortex Liver
136-23 29-5
205-23 49-6
<5 <1.5
<5 ^1.5
Inorganic matter
percent of wet weight
mean and standard
de vi at i on
Right tibia
47. 12-0.58
48. 01-1. 20
Rats were treated for two months with cadmium and normal diet
(Cd * Ca),  cadmium and calcium deficient diet (Cd - Ca), calcium
deficient diet (  - Ca) and normal diet (controls). Cadmium was
given as 25 ppm in the drinking water to the cadmium exposed

Table 4:2
LEVEL (data from Decker et al., 1958, and Anwar et
al.,  1961 ) .

jug Cd/ml hUO
Ratio li
6 months 12
0.20 0.
0.38 0.
0.43 0.
0.67 0.
ver Cd/renal Cd

4 years







'U.S.. 4.

T/. Co many

B, Sr:eOcn (pre-
ul scntly exposed)
Sueder. (not
exooacd for
10-20 years)-
V/. Csrar.ny
'••'. Germany

=" W . Gcrrany



'it. Ccraany
.7. Gcrnp.ny











Mean Median




at r.l., 196







W. Ger-
W. Ger-

W. Ger-
H Mean Range Unit
154 1.59 0.5-10.8 ug/1

30 3.1 0-15.9 ijg/1

14 1.0 - ug/1
10 0.98 0.34-1.57 ug/24 hrs

169 1.25 0-5 fg/g crea-
phic after

Atomic abs.
after MIBK-
APCD extrac-
Imbus et al. ,

Suzuki, Suzuki
and Ashizawa,
Mappes, 1969
Schaller and
Haas. 1968

Schaller and
10   0.39   0.19-0.77
us/24 hrs
Lehnert, 1969

Linnman and
lished data)


Country n
France . 2
England 12
Japan 34
England 56
W. Germany 18
Range Unit
530-1120 jJg/24 hrs
12- 487 jjg/1
9- 36xjjg/l
14- 420 ^jg/1
16- 425 ;jg/l
0- 159 yg/1
3- 140 ug/1
0- 168 /Jg/l
6- 74xxjg/l
0.8-6.2 /ug/g crca-
Type of
CdO dust
CdO dust
CdO dust
CdO dust
CdO fume
Cd s tea-
CdO fume
CdO dust
CdO dust
CdO fume
Method Reference
Nephelome- Truhaut and
trie Boudene, 1954
Dithizone Smith, Kench and
Lane. 1955
" Smith and Kench,
" Smith and Ken ch,
" Smith and Kench,
" Suzuki, Suzuki
and Ashizawa,
" Tsuchiya, 19G7
" Ariams, Harrison
and Scott, 1969
" Adams, Harrison
and Scott, 1969
Atomic abs. Lehnert et al.,
after MIBK- 1969
APCD extrac-
 Workers in alkaline accumulator factory not directly exposed to cadmium

xxWorkers with proteinuria without present exposure.

                     Table 4:6   "NORMAL" CONCENTRATIONS OF CADMIUM  IN  HAIR

U.S. A



Yugos lavia
Rural area
Sex n
Male 82

Female 47
children* 45
Male 7
Female 8
Male 17

i s.o.
- 4.37

- 1.64
- 4.94
- 1.54
- 0.99
- 1.30
- 0.0
- 0. 14
- 0.2G
- 0.27
Median Range

0.43 0.24-0.60
0.92 0.41-1.27
0.45 0.20-1.43
Method Reference
Atomic abs. Hair Schroeder and
not treated with Nason, 1969
detergent solution
C " "
Atomic abs. Hair Hammer et al . ,
pretreated with 1970

Atomic abs. Hair Nishiyama
pretreated with (personal
detergent communication)
.1 n
'10 years of age  from 5 areas with  differing  degrees of  cadmium  contamination

    Cd mp./10U }* dry  weight
                    o    0
                      OQO o
                0 12 24.3 5 7  9  11 13.3 5 7 9 11 ft 15
               —hours-^ •   doys	*    weehs	
                       time after gassing
               O = conUelo  fatalities
               Q •• coaUoifc
F i gu re  4 : 1
Concentrations  of Cadmium in Lunp,s  of Dogs  at
Intervals Following Exposure to  Cadmium Chloride
Aerosols (modified from  a figure  by Harrison  et
a 1 . .  V.J 4 7 ) .

Cri mg/100 g dry  weight






                12 24|3  5  7  911 13i3 5  7  § 11 1315

             — hours-*	days	'	weeks	
                      time after gassing
              O = controls totalities

              O = controls •sacrificed
Figure  4:2
Concentrations of  Cadmium in Kidneys of Dogs  at
Intervals Following  Exposure to  Cadmium Chloride
Aerosols   (modified  from a figure by Harrison et
al..  1947).

 Cd mg/100  g dry weight







                 12 24 j 5  5  7 9 l'l 13,3  5  7  9 l'l
              —-hours-1 -   days	weeks —
                      time alter gassing —•	
               O =» cbnMolo fatalities
               O = contfola sacrificed
Figure  4:3
Concentrations of  Cadmium  in  Liver of  Dogs at
Intervals  Following Exposure  to Cadmium Chloride
Aerosols  (modified from a  figure by Harrison et
al.,  1947).

                                               33080t     -.121661     -10251
                                    CN-3IOO£       +8306      +206
                                     CN - 4i5oe-39346V90oe-'2552V3o£-03401t
«», ~,~~ -.462471 .,„-,
CM =8106 + 3201
V A l
0 30 60 90 120
Jisappearance of Cadmium from Plasma after an Intravenous Injection of

               (from Walsh and Burch,  1959).

   Relative concentrations
   of Cd in blood.
               •* Mouse 8.c. I4mg/kg
               • • Rat   s.c. tracer dose
               •o Rat   s.c. I25mg/kg
                                                       Hours after
In each  report the concentration in  blood after 24  hours has been
set at  1.U  and concentrations at other times are expressed in
relation  to the concentrations at 24  hours. For calculation of
whole blood values from cell and plasma concentrations  it has
been assumed that the  cells constitute about 45 percent of the
whole blood.
Figure  4:b   Concentrations of Cadmium in Rlood  Related to
              Time, after Subcutaneous  Injections  of  Cadmium
              in Rats  and Mice  [from  data bv f-'ybl,  Sykora
              and  Mentl,  VJtiBa, Gunn,  Hould and Andorson,
              19f.iOa, rjnri Lucir,, Lynk and Lucia, 1G6(J ) .

    R el olive concenlrotlons of Cd
    in cells and plasma
                                            Plasma Cd
                                            Rat s.c. 1.4mg/kg
                                            Erylhrocyte Cd

                                            Plasma Cd
                                            Rat s.c. tracer dose
                                         •••  Erythrocyte Cd
                Hours after
 In each  report the  concentration in  the cells  after 24 hours has
 been set  at 1.0  and the  concentrations  in cells  and plasma are
 expressed in relation to  the  concentration in  cells at 24  hours.
 F i g u re  4:6
Concentration  of  Cadmium  in  Cells and  Plasma
Rfilated to Time after Subr.utansous  Injections
in Rats (from  data by fiybl,  Sykora  and Mertl,
and  Lur.ii, Lynk and Lucis,  19li'J ) .

            X 200-
            9 175 -

            £ 150-

           .£ 125 -
          12     25H
                     I   30 60 90  120 150

                   Days post-injection Cd115
F i g u re 4:7
Accumulation of Cadmium in Kidney  and Liver of Rats
after  Intracardiac Injection (from Gunn and Gould,

           Brain                     Liver       Kidney

               '.;,..-"                    '              *,-.;;
                 '  '    •'•    -•—	•   .^••••^••aSiditafai
Fig 4:8 Autoradiographic distribution of     Cd in a Mouse 112 days after a Single

Intravenous Injection (from Nordberg, unpublished data).


        UyJB         ° Rats eiposed during
                     months 1-6 and 7-12.

                    • Rots eiposed during
                     months 1—6 only.
            2   o      o
I           -   °
0              o
                        ••    «
                                10  11   12
Int rapt? ri toneal injections  0.75  mp Cri/kg  three  times  a  week,
months  "-'j  or 6;   0.25 mg  Cd/kg  three  times a week, months  7-12.
Figure  4:9    Cadmium Concentrations in  Liver of  Rats  Exposed
               to Cadmium Chloride   (modified from a figure, by
               Bonnell,  Ross  and King,  1960)




                   KIDNEY    o Rait eiposed during
                    months 1—6 and 7—12.

      o            • Rats eiposed during
      0             months 1—6 only.
                                HT^ 11  12
Intrapsritonea1 injections:  0.75 m^  Cd/k£.  three  times  a  week,
months  1-5,  or 6; 0.25 mg  Cd/kp, three times a week,  months 7-12
Fip.ure  4:10   Latimi urn  Loni.-.Hnt rat. ions  in Kidnev of  Rats Lxposed
               to ("iadmiuni f'hloridr?   (motJifiod ffom  d fipure
               by Monnall. Kosn  nnd  Kinp,,  19LH1).

4      *
                   , ...uln mil Jin
                                    4      •  MM
                                   	.. LJ III Hill
                             Kd /*.+*
(*) • proteinuria demonstrated only with trichloracetic  acid
+ - +** > proteinuria demonstrated also with  nitric  acid
Figure 4:11  Cadmium Concentrations and  Occurrence  of Protein
             in Urine of Cadmium Exposed Rabbits   (from Friborg,

                          75l35  144 100  216  252 208  324 300

                          DAYS  AFTER ADMINISTRATION
F i g u re  4:12
Whole-Body  Retention of Orally  Administered     Cd

in 8 Mice   (modified from  a  figure by Richmond,

Findlay  and London, 19GB).

         •jugCd/lOOml blood
               1968             1969      1      1970
                      Exposure            I    No exposure
Figure 4:13
Cadmium Concentrations  in
during and after Exposure
(Spectropraphic Method)
personal communication).
Blood from a Worker
to Cadmium Oxide Fumes
(from Rogenfeldt,

Cadmium in liver
ppm wet weight.
                                               A  Workers eiposed to cadmium oxide dust
                                                  and fume
                                               a  Itai-itai patients
                                                 > Normals

                                                               I  Kanazawa lapon
                                                               jL Kobe Japan
                                                               KL USA
                                                                  Sweden (3areas)
tOO Age in years.
      Figure  4:14
                Cadmium  Concentrations  in  Liver from Norman  Human
                Beings in  Different Age Groups  (mean values).
                Exposed  Workers (single values) and Itai-itai
                Patients   (single values)   (data on normal human
                beings from Kanazawa, Japan  -  Ishizaki, Fukushima
                and Sakamoto,  1970b^
                Kobe, Japan  -  Kitamura,  Sumino and Kamatani,  1970
                U.S.A.   -   Schroeder and Balassa,  1961, Schroeder et.
                al..  19(i7
                United Kinpdom  -'  Curry and Knott, 1970
                Swodnn   -   Piscator, unpublished data
                data  on  Rxposed workers, sae figure 4:15
                rlata  on  Itai-itai patients   -   Ishizaki,  Fukushima and
                Sakamoto,  19 /'Jb).

         Cadmium In liver
          9pm wet weight.
                               o Exposure to CdO dust

                               • Exposure to CdO fume

                            7—32 Exposure time in years
                                           Years after last
Figure  4:15
Cadmium Concentrations  in Livers  of Exposed Workers

in Relation to  Time Since Exposure Ceased (from

data  by Bonnell,  1955,  Friberg,  1957, Smith, Smith

and McCall, 19bO,  Kazantzis et  al., 1963, and

Piscator,  unpublished  data).

Codmium in renal cortex
ppm wet weight.
 A Workers exposed to cadmium
  oxide dust and fume.
 a Itai-itai patients.

 X Kanazawa tapann
 I Kobe Japan
                                                    S Sweden (2 areas)


                                                      100 Age in years.
         Figure  4:16
                  Cadmium Concentrations in Renal  Cortex from
                  Normal Human  Beings in Different Age Groups
                  (mean values).  Exposed Workers  (single values)
                  and Itai-itai  Patients (single  values)
                  (data from  reports cited in fipures 4:14 and 4:15
                  and from  some  determinations of  renal cadnium in
                  biopsies  from  cadmium workers,  see  table 6:1).

  U   o
    o  „  o
       • o •     V o. !
          I   I   I   I •,[
                                               o    •
                                         •        •

                                               **o o
o    .*  •% "

  1°   «o»  ..
                                                 o» •
                                                  Age  in  years
Figure 4:17  Cadmium Excretion  in Relation  to  Age   (from

             Szadkowski, Schaller and Lehnert,  1969).

 t-0-4 liyer cadmium/renal cadmium.
                              • \   ••
                            •• •••    ••
                     10            too           1000
                                Cadmium in renal cortex
                                ppm wet weight.
  Figure 4:18    Ratio between Liver and Renal  Cortex Concentrations
                 of Cadmium in Relation to Cadmium Concentrations
                 in Renal Cortex in Horse  (from Piscator,  unpublished

   Urln» protein
   m g /gram c r • a 11 n I n«
                             y= 644i * 74

                             r= 0.76
                                   2.0  Cdpg/lOOml blood
 Figure 4:19
Urinary  Protein Excretion in Relation  to Blood
Concentrations of Cadmium in Workers with Earlier
Exposure  to Cadmium but  not Exposed  during the
Last 20  Years  (from Piscator, unpublished data).

                           CHAPTER 5
Much evidence has been collected and entered  in  the  literature
showing the severe and extensive respiratory  effects  in human
beings exposed in industries and in animals  exposed  in labora-
tories to various cadmium compounds. These symptoms  con be noted
in cases of acute exposure to high concentrations as  well as in
cases of chronic exposure to low concentrations  of cadmium. In
this review special attention will be given  to the effects of
chronic exposure. As the acute effects serve  to  show  the potential
hazards of cadmium, a brief review is given  also of  the nature of
such effects as well as the concentration ranges associated with

In 1932, Prodan reported acute effects in animals which had in-
baled cadmium compounds. Since that time, several reports veri-
fying the deleterious effects on the lungs of both animals and
human beings have been published. Some data  have been recorded
regarding doserresponse relationships for different  species.

Paterson, 1947, described in detail the pathology in  rats acute-
ly poisoned with cadmium through inhalation  of finely dispersed
cadmium oxide or cadmium chloride aerosols.   The  findings, simi-
lar for both exposure types, were confined to the lungs. The
three clearly demarcated stages were 1) acute pulmonary oedema,
developing within twenty-four hours of exposure, 2)  proliferative

interstitial pneumonitis, observed from the third to tenth days
after exposure, and 3) permanent lung damage in the form of peri-
vascular and peribronchial fibrosis. Similar findings, including
long-term effects of an emphysematous nature, have been reported
by Thurlbeck and Foley, 1963.

The first two of the demarcated stages described in animal studies
could be confirmed clinically or at autopsy on human beings ex-
posed during, for example, welding or cutting materials containing
cadmium (Paterson, 1947, Huck, 1947, Reinl, 1961, Lamy et al., 1963,
Kleinfeld, 1965, Blejer, Caplan and Alcocer, 1966, Beton et al.,
1966, and Townshend, 1968).

The question of whether a nonfatal acute exposure can produce  long-
term effects in human beings does not seem to have been properly
studied on a large number of cases. Townshend, 1968, reported  one
case of pulmonary oedema caused by acute cadmium poisoning which
was observed over a period of 4 years. Tests showed a gradual  im-
provement of the lung function during the first 6 months. Four
years later the CO diffusing capacity was normal but the forced
vital capacity was less than 80 percent of the predicted value.
Similar studies on larger groups exposed acutely to cadmium are
greatly needed.

Human data regarding dose-response relationships are quite.iscarce.
From animal experiments evidence is fairly well documented con-
cerning the acute mortality  rate after short-term exposure to  cad-
mium oxide fumes, the type of exposure occurring in connection
with most of the reported human cases.

Earlier mentioned studies by Harrison et al., 1947  ( show-
ed an LDgQ in dogs of 320 mg/m  over a 30-minute exposure to a

cadmium chloride aerosol  (9600  min  '  mg/m ).  Barrett,  Irwin and
Semmons, 1947, gave  data  from exposure  of a  substantial number
of rats, mice, guinea pigs,  rabbits,  dogs and monkeys  to cadmium
oxide fumes. The exposure  periods  lasted  from 10 to 30 minutes.
The LD,-n (cumulative mortality  up  to  7-28 days)  varied between
500 and 15,000 min  " mg/m  depending  on animal species (table
Based on the amount of cadmium  found  in  the lungs  and the lung
•ventilation for the different species,  the  authors calculated the
retention of cadmium, to  about  11  percent.  This  did not differ
markedly among the species.  They  also calculated the dose for two
fatal human cases described  by  Bulmer,  Rothwell  and Prankish, 1938,
and Paterson, 1947, to 2500  min  '  mg/m .  Starting  points were ob-'
served values of cadmium  in  the  lungs corresponding to 1.8 and 1.7
mg cadmium oxide per  100  g of dry  tissue,  respectively, and an as-
sumption that the percentage of  retention  of cadmium oxide fumes
for man was the same  as for  animals.

An independent check  on this calculated  dose was made by Barrett
and Card, 1947. They  tried to reproduce  the actual exposure condi
tions.and measured the cadmium  concentrations formed. They con-
cluded that a lethal  concentration  of thermally  generated cadmium
oxide fume for man doing  light  work is  not  over  2900 min ' mg/m
and would possibly be as  little  as  half  of  this  value for arc pro-
duced fume. Beton et  al.,  1966,  applied  to  a fatal case of cadmium
ptfisqning the type of calculations  used  by  Barrett,  Irwin and Sem-
mons, 1947. With an observed concentration  of cadmium oxide in
the lungs of 0.25 mg/100  g of wet weight,  they reached the con-
clusion that the concentration  times  exposure time should have
been around 2600 min  * mg/m  . The exposure  time  in this case was
five hours and the authors calculated an'average lethal concen-
tration for this exposure  time  to be  around 6.6  mg/m  for cadmium

oxide fumes. For 8 hours exposure, a lethal concentration would
then be around 5 mg/m  .

The authors pointed out the uncertainty in regard to some of the
assumptions necessary  for tho calculations. There could be no
doubt that such uncertainties existed. Furthermore, the used
"retention value" of 11 percent was with all probability consid-
erably lower than the  "retention value" immediately after the ex-
posure. As a value of  11 percent was used in both the animal studies
and in the calculations for human beings, any error tends to be can-
celled out, however. There are reasons to accept a figure of about
5 mg cadmium oxide fumes/m  o
lethal concentration for man.
5 mg cadmium oxide fumes/m  over an eight hour period as a probable
By no means must 5 mg/m  be the lowest which can give rise to fatal
poisoning. It is known from animal experiments  (Paterson, 1947)
that exposure to concentrations of only about one-fourth the LD5U
can give rise to acute symptoms and to a significant degree of
permanent lung damage. Even without applying a  safety factor when
extrapolating from animal data, there is thus reason to regard a
concentration of around  1 mg/m   over an eight  hour period as im-
mediately dangerous,  for human beings with reference to cadmium
oxide fumes.

For cadmium dust, the data necessary to perform similar estima-
tions are not available. Friberg, 1950, however, determined LuVn
for 7 groups of 8 rabbits for a cadmium-iron oxide dust (proportion
Cd to Fe: 3:1, observation period: 14 days). On an average, about
95 percent of the particles were smaller than 5 microns and about
55 percent smaller than  1 micron (coniometer method). The rabbits
were exposed for 4 hours and LD^ calculated as the product of
                                                  •   «     3
concentration and exposure time was about  11,000 min * mg/m .

Taking only the cadmium oxide part of the  dust  into  consideration,
                    I                                          3
the LDgQ for cadmi umoxi de dust would be about 8000 mi n  '  mg/m  ,
i.o., about three to four times the values  for  cadmium  oxide  fumes
(for rabbits: 2500). For an 8 hour exposure, this gives  a  concen-
tration of about 17 mg/m  of cadmium oxide  dust  for  rabbits.

5.2.1  In human beings
There are in the earlier literature, Stephens,  1920,  scanty  data
suggesting a chronic cadmium poisoning  in human beings.  With  the
knowledge available today, it can further 03 Efaid  that  some  early
reports of plumbism might instead have  been cadmium poisoning.
When Seiffert, 1897, described 65 cases of chronic  lead poisoning
among workers in a zinc smelter, he thus reported  emphysema  among
83 percent and proteinuria among 82 percent of  these  workers. No
doubt there must have been a considerable exposure  also to cadmium
and the symptoms described fit chronic  cadmium  poisoning.  Respiratory effects reported - exposure  to cadmium dust
The first reports of lung emphysema in  chronic  cadmium  poisoning
were given by Friberg. 1948a and b, and in more detail  by Friberg,
1950, in studies among male workers exposed to  cadmium  oxide  dust
in an alkaline accumulator factory in Sweden. Complaints of  short-
ness of breath were common. An impaired lung function was demon-
strated as an increased residual capacity in relation to total
lung capacity. It was shown that the impairment of  lung function
was closely associated with a poor physical working capacity  eval-
uated with a standardized working test  on a bicycle-e rgometer.
(figure 5:1).

The Swedish reports referred  to above covered  43 male workers
with an average time of employment of 20 years  (range: 9-34
years). Another group of  15 workers, similarly  exposed,  among
whom the lung function was normal, had been  employed for only
1-4 years. All workers had been exposed  to a mixture of  cadmium
iron oxide dust and nickel graphite oxide'dust. Quantitative
data concerning the exposure  were  incomplete,  as air analyses
were made only upon one occasion and only at five places (over
about  30 minutes on each  place) in the working  rooms. The  amount
of cadmium in the air varied  between 3 to 15 mg/m .  Time  weighted
6-hour averages values were not calculated but  were probably  lower.
Respiratory masks were provided but stated to  be used rarely.

The Swedish findings were confirmed at a similar German  factory
by Baader, 1951 and 1952. Out of 8 workers exposed 8-19  years, 6
had emphysema as judged by clinical and  X-ray  examinations.  Com-
plaints of coughing and shortness  of breath  were common. No  quan-
titative analysis about the exposure was given.

Several other reports of  lung damage have since been made. Vorobjeva,
1957,  reported "diffuse pulmonary  sclerosis" among female  workers
in the production of alkaline accumulators.  From the same  type of
factory in Britain, Potts, 1965, reported bronchitis in  6  men, and
associated emphysema in 4. Diagnostical  methods were not discussed.
In a later report from  the same factory, Adams, Harrison and Scott,
1969,  found a decrease  in forced expiratory  volume  CFEV  )  in male
workers.(figure 5:2). Twenty-seven male  workers were covered.  Their
exposure times were not obvious from the  report, but seem to have
varied from 15 to 40 years. Cadmium in air estimations were  reported
beginning from 1957. Before that time, regular analyses  were not
carried out. In one working area in the  factory, most values varied
between 0.5-5 mg Cd/m  , in a  second between  0.1-0.5, and in  a  third.

mostly around 0.1 mg Cd/m  .  It  is not possible  from  the  report
to evaluate the exposure before  1957. The  extent  to  which  res-
pirators were worn was not stated.

Kazantzis et al., 1963, reported emphysema in cadmium  pigment
workers. Thirteen men  had  been  exposed  to  a  variety  of cadmium
compounds, of which cadmium  sulphide based pigments  were by  far
the most abundant. In  addition  to cadmium  sulphide,  l.he  compounds
included cadmium seleno-sulphide, cadmium  zinc  sulphide, cadmium
.carbonate, cadmium hydroxide and cadmium oxido  dust  and  fume. Out
of 6 men engaged in the manufacture of  cadmium  pigments  for  25
years or more, 3 had mild  respiratory symptoms  and showed  slight
but definite impairment of ventilatory  function with a low FEV.
percentage (56-61) and a high time constant  (1.08  -  1.38 seconds).
A fourth man had died  at the age of 4u'  from respiratory  insuffici-
ency and right-sided heart failure due  to  emphysema. It was  con-
cluded that the emphysema was caused by exposure  to  cadmium. Con-
cerning the exposure,  the  report contains  no data  on air concen-
trations of cadmium. The exposure times were as follows: 25  to  31
years for 6 of the workers,  12  to 14 years  for  4  of  the workers,
and 1/2 to 2 years for 3 of  them.  Respiratory effects  reported -  exposure to  cadmium oxide  fume
British researchers have published several  reports on  chronic cad-
mium poisoning in men exposed to cadmium oxide  fumes in  casting
copper cadmium alloys. Emphysema has been  prominent  among  the symp-
toms. Lane and Campbell, 1954,  thus reported two  fatal cases among
men making a cadmium copper  alloy for less  than two  years. The  gen-
eral exposure was given as 0.1-0.4 mg Cd/m . For  very  short  periods,
however, the men had been exposed to high  concentrations of  cadmium
metal fume (actual concentrations not given). Bonnell,  1955, exam-
ined 100 exposed men and 104 controls from two  factories.  The res-

piratory function was tested by measuring the vital capacity, the
maximum ventilatory capacity at controlled  rates of breathing, and
the expiratory fast vital capacity. Swept fractions at given  res-
piratory rates were calculated. Among the exposed workers  11  were
diagnosed as having emphysema. There is no  mention of emphysema in
the controls. On a group basis significant  differences were found
between exposed and controls.  In factory A  the vital capacities
and the maximum ventilatory capacities were similar in the two
groups, but the mean swept fractions  at 30, 50 and 70 respira-
tions per minute were significantly lower in the exposed group.
A significant difference was also  found between the groups, for
the mean time constant of the  expiratory fast vital capacity
curve. In factory B the mean time  constant  for the expiratory
fast vital capacity curve differed significantly between the  ex-
posed group and the control group. The other test results  were
similar in the two groups. The results of these tests are  dis-
cussed in more detail by Kazantzis, 1956.

Some further studies were made on  37 exposed men from factory B
(Buxton, 1955). The men with more  than 10 years' exposure  showed
a significant increase in the  mean value of the residual air  ex-
pressed as a percentage of the total lung volume, (mean: 43.9%,
S.D.: 10.3%) compared with a control group  (mean: 34.6%, S.D.:
8.3%) and workers exposed less than 10 years (mean: 36.6%, S.D.:
10.9%). The workers in the "cadmium groups" had been exposed
from 1 1/2 to 28 years, and those  with a recognized emphysema
from 7 to 27 years. King, 1955, has made a  careful study to eval-
uate the exposure conditions at the time of Buxton's medical  in-
vestigations. It is obvious from King's data that the concentra-
tions of cadmium were considerably lower than in the accumulator
industries referred to. At one working area he found average
values for 6 hour working shifts over a 5-day period of from  13

 to  89  /jg  Cd/m.},  at  another place  (two different positions)  over
 a  9-day  period,  from 4  to  132>ug/m ,  and at a third working  place
 (four  different  positions)  over an 8-day period, from 1  to 270
/ug/m '. About  90  percent  by  weight  of  the particles had a size of
 less than  0.5  microns.  It  is obvious  from the report that the
 mean exposure  for the majority  of  the workers must have  been con-
 siderably  less  than  0.1  mg   Cd/m .  Unfortunately the study did
 not  show the  earlier exposure  conditions.  King pointed out that
 during recent  years,  the working conditions in the industry  had
 improved.   Respiratory  effects  not reported
 Above  have  been  discussed  studies  in  which pulmonary effects of
 chronic  cadmium  intoxication have  been observed. There are also
 reports  with  negative findings.

 Suzuki,  Suzuki  and Ashizawa,  1965,  examined workers exposed  to
 cadmium  stearate  dust and  lead  in  a vinyl  chloride film plant.
 The  study  comprised  27  male workers in 1963 and 19 male  workers
 (mean  age:  22.8  years,  S.D.:5.5  years, time of employment: 3.3
 years, S.D.:1.9  years)  as  well  as  24  controls- in 1964. They
 found  at the  examination in 1964 no increased occurrence of  res-
 piratory symptoms  in  the exposed group compared to the controls.
 Furthermore,  there was  no  difference  between the two groups  in
 the  outcome of  lung  function tests. The concentrations of cad-
 mium in  1963  (standard  impingers)  at  one occasion (sampling  time
 not  given)  were  at four  different  operations 0.03, 0.26, 0.55
 and  0.69 mg Cd/m . The  size of  the particles varied from 0.4 to
 20 microns  (cascade  impactor,  dare field microscopy).  The expo-
 sure took  place  three or four times a day  for twenty minutes
 each time.  Nothing was  mentioned about the use of respirators.

Apart  from  the  above  mentioned study,  no reports  are  known to
us  in.which  a  careful pulmonary examination,  including lung
function  tests,  has  revealed  negative  findings.  There are  some
reports,  however,  where  the use of more  insensitive  methods has
shown  normal or only  very slight changes.  These  reports  are re-
ferred to below.

Princi,  1947,  examined 20 workers in a cadmium smelter.  In the
clinical  examination  he  found no subjective  symptoms  which could
be  connected with  exposure to cadmium (no  controls were  examined).
Pulmonary X-rays  showed  normal conditions.  Lung  function studies
were  not  carried out. The average period of  employment for the
workers  examined  was  0 years  (range: 0.5 to  22 years, 7  workers
with  more than  10  years). All of them were  exposed  to cadmium in
the  form of  dust  or  fumes (CdO and/or CdS).  Princi  carried out
air analyses on three different occasions  at 11  different  areas
of  work.  In  this  connection he found values  which,  calculated as
metallic  cadmium,  varied as a rule from 0.04 to  1.44  mg/m . In  a
few  of the  working areas there were considerably  higher  concen-
trations  of  dust.  Thus in 2 places in  which,  to  judge from the
description  of  the working conditions, the  men were  probably ex-
posed  to  cadmium sulphide, values of 19  and  31 mg Cd/m  were mea-
sured. In another area of work, where  the  workers were probably
exposed  to  cadmium oxide, a content of 17  mg Cd/m was measured.
Since  many  of  the  men were stationed sometimes at the one, and
sometimes at the  other area of work, an  accurate  estimate  of the
individual  exposure  was  not possible.  Respirators were provided
.but  worn  infrequently.

Hardy  and Skinner, 1947, left open the question  of  the possibil-
ity  of chronic  cadmium poisoning. They examined  5 workers  exposed
for periods  from 4 to 8  years in the production  of  cadmium-faced

bearings. The workers complained of  unspecific  symptoms,  in-
cluding respiratory symptoms on damp  days.  Chest  X-rays  were
normal. No lung function tests were  carried out.  The authors
gave the average exposure to cadmium  as  approximately 0.1  mg
Cd/m  air.
L'Epee et al.. 1968, examined 22 workers  in  an  alkaline  accu-
mulator industry,  14 of whom had been  employed  for less  than
5 years and 8 for  more than 5 years. Unspecific respiratory
symptoms were found among 5 workers. No pulmonary  studies  were
made. The report included no quantitative  data  on  cadmium  expo-

Tsuchiya, 1967, examined 13 workers  (age  range:  19 to  32 years)
and 13 controls.  The workers had been  exposed to cadmium fumes
while smelting alloys of silver and  cadmium. No lung  function
tests were reported. Chest X-ray examinations did  not  reveal
any abnormalities. No persistent subjective  symptoms  could be
detected. The cadmium concentration  in the air  was reported  as
time weighted averages (electrostatic  precipitator)  at nose  lev-
el of the workers  for 5 days and values varying from  68  to 241
ug/rru were found.

5.2. 1.2  Amb_ie_n^ ,ai£ §.x£os_u£e_
Only scanty data are available concerning  a  possible  association
between respiratory disorders and exposure to cadmium via  am-
bient air. Lewis,  Lyle and Miller, 1969, studied the  cadmium,
copper and iron concentrations in water-soluble protein  fractions
of liver extracts  in connection with autopsies  of  patients with
chronic bronchitis and emphysema. The  samples were analyzed  by
atomic absorption  spectrophotometry. They  found a  higher concen-
tration of cadmium compared with a control group but  no  differ-

ences for iron and copper.  The  groups  consisted  of  adult  pa-
tients, but no age distribution  was  stated.  For  20  patients
with chronic  respiratory  problems,  the  cadmium concentrations
had a mean of 40.4 (S.E.:  6.0)>ug  cadmium  per g  protein.  The
corresponding value  for  38 controls  wan  10.6 (S.E.:  1.7)jug
cadmium per g protein.   Morgan  (unpublished  data) in  a  simi-
lar study also found  an  increased  hepatic  concentration  of
cadmium in deceased  patients with  a  diagnosis of emphysema.
For a discussion  of  this  study,  see  section  7.2.

Peacock (unpublished  data)  reported  a  study  of 127  residents,
aged 50 to 69, of Birmingham, Alabama.  They  were given  a  de-
tailed questionnaire  on  their health status  supplemented  by
a medical examination, including determination of serum cadmium
levels (atomic absorption,  analyses  carried  out  by  Morgan).  The
127 participants  were part of a total  sample of  464 individuals
who in turn comprised 7B  percent of  those  requested to  attend.
Pfeacock compared  the  prevalence  of an  extensive  number  of vari-
ables such as symptoms,  food, drinking  and smoking  habits and
social characteristics in groups of  high and low cadmium values.
The only statistically significant (p ^T .05) association  he
found, with vertigo,  certainly  was no  more than  would have been
expected by chance.  He also observed a  relation  (p  ^ .01) between
place of residence and cadmium  levels,  with  most of the  high se-
rum cadmium levels among  groups  who  might  have been exposed  to
cadmium as an air pollutant presumably  derived from the  industri-
al steel complex  in  Birmingham.  The  study  may serve as  basis for
further investigations with specified  hypotheses.

In summary,there  are  a few data  tending  to  show an increased  cad-
mium storage  in persons  with a  diagnosis of  emphysema and/or
chronic bronchitis at autopsies. No  information  concerning the
causes of the found  association  is available.

5.2. 1. 3
Friberg, 1950, showed that workers with emphysema had a poor
physical working capacity. He also reported one fatal case in
which the cause of death was a pronounced emphysema as well as
another case in which pronounced pulmonary symptoms were present
and hypertrophy of the right ventricular chamber was found at
post mortem. Baader, 1951, reported one fatal case due to severe
emphysema. From England reports of several cases in which the
cause of death was emphysema have been published (Lane and
Campbell, 1954, Bonnell, 1955, Smith, Kench and Smith, 1957,
Smith,  Smith and McCall, I960 and Kazantzis et al., 1963). The
British researchers have pointed out that they did not find
evidence either clinically or pathologically of chronic bron-
chitis. Figure 5:3 shows a whole lung section of a fatal case.
The prognosis of chronic cadmium poisoning is further eluci-
dated by data from two five-year follow-ups by- Friberg and
Nystrom, 1952 and by Donnell, Kazantzis and King, 1959, of
the two earlier mentioned studies by Friberg, 1950, and
Bonnell, 1955. When given respiratory function tests, exposed
groups showed a greater deterioration with increase in age
than the control group in the British study. The results in
individual cases showed a deterioration in the men who had
emphysema at the time of the original survey despite the fact
that the majority with chronic cadmium poisoning had not been
exposed to cadmium since the original examination. In the
Swedish follow-up study, subjective symptoms increased in
several of the cases. Though a general tendency toward poor
lung function remained, further impairment had not taken
place. Most of the workers had not been exposed to significant
concentrations of cadmium during the period of the follow-up

5.2.2  In animals
 Pulmonary changes have been found in animal experiments. Friberg,
 1950,  exposed 25 rabbits for 3 hours a day for 20 days per month
 for 8  months to about 8 mg cadmium iron oxide dust/m   (taken from
 the alkaline"accumulator factory where the clinical studies were
 carriad out, see section This corresponded to approx-
 imately 5 mg cadmium/m , or about 900 min ' mg/m  per exposure  day
 All rabbits showed signs of emphysema in addition to inflammatory
 changes.   As the workers in the accumulator factory were exposed
 also to nickel graphite dust, similar animal experiments were
 carried out with such dust. Emphysema and inflammatory changes
 were seen but to a much lesser extent, despite the fact that the
 actual dust concentrations were 10 to 20 times higher than in
 the cadmium experiments.

 Vorobjeva,  1957, installed intratracheally in rats cadmium oxide
 dust (0.25  mg/100 g bodyweight), cadmium iron dust (0.35 mg/100
 g bodyweight) as well as nickel graphite dust (2 mg/100 g body-
 weight).  After 4 to 7 months the animals were killed. In the cad-
 mium and cadmium iron groups there were signs of interstitial
 pneumonia,  sclerosis and emphysema. Similar changes were not seen
 among  the animals in the nickel graphite group. In a brief report
 from the U.S.S.R., Shabalina, 1968, mentioned that cadmium stea-
 rate did affect the lung tissue two months after an intratracheal
 installation. The studies were performed to evaluate symptoms of
 cadmium intoxication in human beings in the form of subatrophic
 cathars of the upper respiratory tract and hyposmia.

 Against these findings stands a study by Princi and Geever, 1950.
 They exposed dogs to cadmium oxide dust (10 dogs, 6 hours a day,
 5 days a week for 35 weeks) and cadmium sulphide dust  (10 dogs,
 B hours a day, 5 days a week for about 30 weeks) without finding
 any respiratory changes at post mortem compared with a control

group.  The concentrations of cadmium  in  the  air  varied  from
            3                                         3
3 to 7 mg/m   with an average concentration of  4  mg/m .  Nine-
ty-eight percent of the particles were  less than  3  microns  in
diameter. It'should be mentioned that  several of  the  animals
had to be killed because of severe  injuries received  while
fighting among themselves. Dogs that died  of  injuries had bron-
chopne umonia.
Brief inhalations of high concentrations  of  camium  compounds
can give rise to severe, often fatal, pulmonary  changes  (pul-
monary oedema). This has been shown  in human beings with  regard
to cadmium oxide fumes and in animals with regard to  cadmium
oxide fumes, cadmium chloride aerosols and cadmium  oxide  dust.

For human beings a fatal exposure to cadmium oxide  fumes  and
cadmium chloride aerosols is not higher,  probably lower,  than
                     3                                3
about 2500 min ' mg/m  (corresponding to  about 5 mg/m  for  8
hours). An exposure to about 500 min * mg/m  (corresponding to
about  1 mg/m  over 8 hours) is considered immediately  danger-
ous .
Dose-response relationships for cadmium oxide  dust  are  scarce
and uncertain. In rabbits LDj.,, was about  8000  mi n  *  mg/m ,  which
would correspond to about 15 mg cadmium oxide  dust/m for  an  8-
hour exposure.

Occupational exposure for longer periods  of  time to  lower  con-
centrations of cadmium compounds can give  rise  to  chronic  pul-
monary disorders, characterized as emphysematous changes.  These
changes as a rule have taken several years to  develop in human
beings but have been observed already after  a  couple of years'

exposure. Lung damage  has  been  observed  after exposure to cad-
mium oxide furnes as well  as  to  cadmium oxide  dust and cadmium
pigment dust.

Dose - response relationships  are  very  uncertain because time
weighted averages  are  not  available,  or  only  available for
short periods. Furthermore,  it  is  not  known what reduction
of exposure was brought  about  due  to  the use  of respiratory
masks. There  is reason  to  believe  that cadmium oxide fumes
are more dangerous  than  cadmium oxide  dust.  For cadmium oxide
fumes, a.prolonged  industrial  exposure to well below 0.1 mg/rn
might well be considered  hazardous, with reference to emphysema.

There exists  evidence  that non-occupationally exposed people
with chronic  bronchitis  and  emphysema  have on an average a
higher body burden  of  cadmium  than "controls." No information
on the cause  of the  found  association  is available.

           (from Barrett,Irwin  and Semmons,  1947)
           Time exposed:  10-30 minutes
                    min  " mp/m
Guinea Pigs
Less than 700.
Probably about
the same as for
rats .
160 animals
used in
groups of
from 10 to 25
only .


                         A  A
                  Maximal physical working capacity with working
                  test on bicycle ergometer:

                              A   S   600 kgm/min
                              o   =   900 kgm/min
                              Q   s£I 1,200 kp;m/min

                  The repression line represents the mean  residual
                  quotient for 200 non-exposed workers.

                  The individual symbols represent exposed workers
         • F-" i gure lj: 1
Lunp, Function ( residual quotiont) and Maximal
Physical Working Capacity in Delation to Age
in Workers Exposed to Cadmium Iron Oxide Dust
(Frihcrp,. IH',0).

                 F i g u re 5:2
FEV,  among Male Cadmium Workers in the  Production of
Alkaline Accumulators.  The Normal Range for Men of tho
Same  Age and Height  (from.Kory et al.. 1961) Shown in
Each  Case (from Adams,  Harrison and Scott, 1969).

Figure 5:3    Emphysema Due to Exposure to Cadmium Oxida Fumes
              (from Smith,  Smith and McCall,  1960).

                           CHAPTER  6

There is much evidence in the  literature  that  exposure  to  cad-
mium will cause impairment of  the  kidneys.  Investigations  have
covered workers exposed to different  cadmium compounds  in  in-
dustry as well as animal experiments.  Almost all  of  the  effects
referred to have resulted from prolonged  exposure  to  cadmium.
A brief mention of the acute effects  will  be made, particularly
against the background of possible enhancement  of  the  effects
due to simultaneous exposure to  chelating  agents.

6.1.1  Acute effects and dose - response  relationships   n
Exposure to high concentrations of cadmium  oxide  fumes  has
caused severe acute lung damage (see  section  5.1).  In  two  fatal
cases described by Bulmer, Rothwell and  Frankish,  1938,  "Cloudy
swelling" was found in the kidneys at microscopic  examination.
The authors ascribed this to a general toxemia.  Beton  et al.,
1966, reported on a fatal case in which  bilateral  cortical  ne-
crosis of the kidneys was found at autopsy. They  thought that
this was mainly .due to vascular changes  associated with  massive
pulmonary changes. The concentration  of  cadmium  in the  kidneys
was given as 5.7 ppm wet weight, which is below  the average
"normal" level for people of the patient's  age  (53 at  death).

In two other patients, who  recovered after exposure,  transient
proteinuria was noted. Electrophoretic examination of  the  urine
from one patient showed  that mainly albumin was excreted.  These
data on renal effects  in man do not allow any conclusions  re-
garding the direct action of cadmium on  the kidneys after  acute
exposure, as the general metabolic disturbances caused by  the
pulmonary oedema and accompanying pneumonia probably will  over-
shadow any other effects.  I.n_anil!3a2.s_
Acute effects of inhalation of cadmium have been studied on
cats by Prodan, 1932.  Two cats were exposed to high concentra-
tions (precise amount  not stated) of cadmium oxide fumes for
30 minutes. One of them  showed fatty degeneration, especially
in the convoluted tubules.  In another experiment three cats
were exposed for 24 hours to cadmium oxide fumes. The  concen-
tration of cadmium in  air at the beginning of the exposure,
       3                                  3
18 mg/m , was gradually  reduced to 4 mg/m at the end  of the
experiment. The cats were killed 5 and 9  days after exposure.
Histological examinations disclosed in all three a moderate
amount of fat in the tubular epithelium.  It was calculated
that the cats had inhaled between 6 and  12 mg of cadmium.

Regarding the dose-response relationship  after respiratory
exposure, no certain conclusions can be  drawn, as in  these
experiments the lung lesions were dominant and might  have
caused a general toxemia. As severe, probably lethal,  lung
damage will occur at cadmium concentrations which can  not
cause renal damage, the  kidney is not a  critical orgar after
acute exposure.

Experiments involving  a  subcutaneous injection have revealed
that the kidneys were  not damaged when rats were given soluble

cadmium salts (2.2 mg Cd/kg), a dose which did cause  testicular
necrosis (Parlzek and Zahor, 1956, Parfzek,  1957,  1960, and
Kennedy, 1968).  Favino and Nazari, 1967, observed  tubular  le-
sions of the nephrotic type in rats given a  single subcutaneous
injection of cadmium chloride (10 mg Cd/kg).

In the rabbit, Foster and Cameron, 1963, produced  renal lesions
with 2 subcutaneous injections of cadmium chloride (9 mg Cd/kg).
The most striking changes were found in the  proximal  tubules.
It has earlier been said that the treatment of cadmium poison-
ing will not be reviewed. However, some chelating agents  (e.g.
EOTA and NTA) have been introduced as components of detergents.
A possible role of these agents in changing the toxicity  of
cadmium in man's environment has been discussed. As most  of  .
the work on chelating agents is concerned with more or less
acute effects of cadmium, a brief mention of a few chelating
agents will be made in this section.

In 1946, Oilman et al . documented a decrease in the acute mor-
tality normally incurred after a single injection of cadmium
when rabbits were treated with 2 , 3-di mercaptopropanol (BAD.
However, several of the rabbits succumbed later from kidney
damage. In a follow-up of these studies, Tepperman, 1946,
showed that BAL increased the uptake of cadmium in the kidneys,
an observation confirmed by Niemeier, 1967. Also EDTA has been
shown to decrease the acute lethality from a single injection
of cadmium (Friberg, 1956, and Eybl, Sykora and Mertl, 1966a)
whereas the agent increased the nephrotoxicity of cadmium after
repeated exposure to cadmium (Friberg, 1956). Oalhamn and
Friberg, 1955, have presented evidence of a similar unfavorable
effect of BAL upon cadmium toxicity during prolonged exposure.

Tobias et al.,  1946, showed  that prophylactic  treatment with
BAL had a deleterious effect  upon mice exposed  to  cadmium
chloride dust by inhalation.  However, when BAL  was  given
promptly after  exposure  to the Cd-dust,  in an  optimal  course
of repeated injections,  it could reduce  the mortality  con-
siderably. Also in  these experiments BAL increased  the cad-
mium content of the kidneys,  but this seems not  to  have been
of importance for mortality  or pathological, as no
renal pathology was observed  following BAL-treatment of mic3
poisoned by inhaling cadmium.

All of the experiments performed by Tobias et  al.  consisted
of a short, single  exposure.  When the data by  Oilman et al.,
Tepperman and Dalhamn and Friberg are considered together
with what is known  about renal lesions as a main feature of
chronic cadmium poisoning, it is highly  probable that  BAL
also increases  the  toxicity  of inhaled cadmium  during  long-tarm
expos ure.

Chelating agents such as hydroxyethylene diaminetriacetic acid
(HEDTA), diethylenetriaminepentaacetic acid (DTPA)  and others
also had a preventive effect  upon acute  cadmium toxicity. Both
EDTA and DTPA (Eybl, Sykora  and Mertl, 1966a)  treatments de-
creased the uptake  of cadmium in the kidneys.  However, to what
extent the decrease in uptake meant a decrease  in  toxicity in
the kidney is not known.

In some contrast to the  above mentioned  diminuations in acuta
toxicities of injected cadmium, Chernoff and Courtney, 1970,
reported an increased acute  toxicity and increased  fetal
mortality in rats given  a single injection of  a  chelate of
cadmium with nitrilotriacetic acid  (NTA). However,  the pre-
liminary nature of  their information makes an  evaluation of

these findings difficult. Long-term  toxicity  has  often  been
influenced in a manner different  from  acute  toxicity  by ther-
apy with chelating agents.  It  is  of  great  importance  to in-
vestigate the influence of  NTA  and other chelating agents  on
long-term toxicity of cadmium.

6.1.2  Chronic effects and  dose - response relationships
6 . 1.2. 1  i.n_h-urna.n_J3EJ.i.£Es_  Proteinuria and  renal  function
In  1950 Friberg, having investigated a large  group of workers
exposed to cadmium oxide dust  in  an  accumulator  factory (for
further details see section,  showed  that prolonged
exposure to cadmium gave rise  to  renal damage. He  studied  two
groups, one of 43 workers with  a  mean  exposure  time of  20  years
(range: 9-34 years) and one of  15 workers  with a  mean exposure
time of 2 years (range: 1-4 years).  In the former group protein-
uria could be demonstrated  with the  nitric acid  test  in 65 per-
cent of the workers and with the  trichloracetic  acid  test  in 81
percent. However,  only 11 percent of the nitric  acid  positive
urines reacted positively to the  picric  acid  test. In the  other
group, with the mean exposure  time of  two  years,  no positive
reactions were obtained with any  of  the  tests. Tests  of renal
function disclosed that in  the  first group,  21 percent  (9  out  of
42) had decreased ability to concentrate the  urine (maximum
specific gravity _ 1.019).  Out  of those  9  people,  8 had a  conn
stant proteinuria. In 33 workers with  a  higher concentration
capacity (maximum specific  gravity —   1.020), only 11  (33%) had
a constant proteinuria.

As  the proteinuria differed from  ordinary  albuminuria concerning
precipitation reactions, a  special investigation  was  made  (Olhagsn,
1950.). Using electrophoretic and  ult racent ri f ugal  analysis.

Olhagen found that in the  urinary proteins  the amount of albumin
was relatively small and that  the dominating proteins migrated
as C\-globulins. The molecular  weight  for  the main component was
between 20,000 and 30,000.
Friberg, 1950, concluded  that prolonged  exposure  through
inhalation of cadmium oxide  dust  pave  rise  to, as a  rule,
relatively mild kidney  damage.  He  suggested  that  the kidney
injury was secondary to the  excretion  of low molecular weight
protei ns.

As late  as 1917 Princi  had claimed  that  prolonged exposure to
cadmium  did not constitute any  snrious health hazard. Having
investigated 20 smelter workers who  had  been exposed to  different
cadmium  compounds  during  a range  of  1  to 20  years, tin found no
proteinuria. As he  had  used  the boiling  test (personal communi-
cation), proteinuria would not  have  been detected. Friberg in
1950 and Piscator  in 1962b showed  that urinary proteins  from
cadmium  workers were not  precipitated  with  this test. The studies
by Princi thus did  not  prove  that  renal  damage had not occurred.

In 1950  Friberg described the common findings of  proteinuria
in workers in alkaline  accumulator factories also in Germany,
England  and France. Further  evidence for the high prevalence
of proteinuria in  cadmium workers  has  been  provided  by Baader
in 1951, Smith, Kench and Lane  in  1955,  Bonnell in 1955, Smith
and Kench in 1957,  Bonnell,  Kazantzis  and King in 1959,  Kazantzis
et al. in 1963, Potts in  1965,  Suzuki, Suzuki and Ashizawa in
1965, Tsuchiya in  1967, and  Adams,  Harrison  and Scott in 1969.
From these investigations, it is  seen  that  not only  cadmium
oxide dust, but also cadmium oxide  fume,  cadmium  sulphide and
cadmium  stearate may give rise  to  proteinuria, provided  exposure

has been prolonged. That proteinuria could appear after the
workers had'been removed from exposure has been indicated by
the findings of Friberg and Nystrom in 1952. They re-examined
38 workers and found proteinuria in 4 who had earlier had
negative test results.

In many of the above mentioned investigations only qualitative
tests had been used for detecting proteinuria. First when quan-
titative determinations were performed by Piscator in 1962a
and b was it possible to study protein excretion in more-'detai 1
in relation to exposure times and removal from work. IiT"1962a
Piscator studied a group of 40 workers, of whom 39 had been in-
cluded in Friberg's investigations in the 1950 report. By using
a quantitative method for the determination of the total urine
protein, Piscator, 1962a, has shown that in these workers, who
had not been exposed to cadmium for the last 10 years, there was
arrelationship between the exposure times, i.e., total dose,
and protein excretion, as shown in figure 6:1. Fourteen urine
samples were examined half a year later by Piscator, 1962a.
Essentially the same protein excretion values were obtained,
indicating that this proteinuria was constant. In additional
follow-ups it was found that, in 18 workers reexamined in 1963,
(Piscator, 1966a) and in 27 workers reexamined in 1969 (Piscator,
unpublished data) from the above mentioned group of 40 workers,
the protein excretion was in mo.c t cases virtually unchanged 3
and 10 years after the first quantitative determinations in
1959. As Friberg had not used a quantitative method for the
determination of protein, a similar comparison could not be
made with his original results. However, a comparison was made
between the results of nitric acid and trichloracetic acid tests
from the two investigations. No marked changes had occurred in
the group (Piscator, 1962b).

Proteinuria has thus been  a  common finding in cadmium workers.
Further evidence of a disturbed  renal function has been given
by the findings of glucosuria documented by Bonnell, Kazantzis
and King. 1959, Smith, Wells and Kench, 1961, Kazantzis et al.,
1963, Suzuki, Suzuki and Ashizawa, 1965, Piscator, 1966a, and
Adams, Harrison and Scott, 1969. Amino-aciduria has been observed
by Clarkson and Kench, 1956, Kazantzis et al., 1963, Piscator,
1966a, and Adams, Harrison and Scott, 1969. A decreased con-
centrating capacity was detected by Friberg,  1950, and by Ahlmark
et al., 1961.  Kazantzis et  al., 1963, and Adams, Harrison and
Scott, 1969, found changes also  in renal handling of uric acid,
calcium and phosphorus. Proteinuria can appear alone without
the other above mentioned  changBS, indicating that proteinuria
is often one of the earliest signs of cadmium intoxication.

Though glomerular function has not been extensively investigated,
the studies of Fribsrg, 1950, Ahlmark et al., 1961,and Adams,
Harrison and Scott, 1969 have shown that decreases in glomerular
filtration rates will appear in  cadmium workers. This symptom is
rather late, appearing after the other above mentioned changes
which are more indicative  of tubular dysfunction. Kazantzis et
al., 1963, found profound  changes in tubular  function but no
definite evidence of glomerular  malfunction.

There have been several deaths due to chronic exposure to cadmium,
However, almost invariably,  the  primary cause of death has not
been kidney disease, which is in agreement with the findings that
proteinuria is usually constant  for many years, with no marked
progress of renal dysfunction once exposure has ceased.
6.1.2* 1.2  Nature of proteinuria
In 19.58 Butler and Flynn described the so-called tubular protein-
uria which they found in cases with tubular dysfunction, as in

the Fanconi syndrome, galactosemia, etc. This proteinuria was
characterized by a relatively small albumin fraction and domi-
nance of proteins with mobility as 0C -,  p- and ^ - globulins
in paper electrophoresis.  By comparing urinary proteins from
cadmium workers with urinary proteins  from persons with other
tubular disorders, Butler and Flynn, 19G1, Butler et al., 1962,
Piscator,  1962a, and Kazantzis et al., 1963, were able to show
that the proteinuria in chronic cadmium poisoning was similar
to the tubular proteinuria described by  Butler and Flynn in 1958.
Typical patterns of urinary proteins in  chronic cadmium poisoning
are shown in figure 6:2. Further investigations by Piscator,
1966a and b, showed that the proteins  excreted by cadmium work-
ers were composed mainly of low molecular weight proteins, chief-
ly derived from the serum. Among these were low molecular weight
jp~ microglobulin enzymes  such as muramidase and ribonuclease
and immune globulin chains, the latter constituting nearly half
of the low molecular weight fraction.  It was not possible to
show the existence of any  proteins specific for cadmium poison-

Most researchers now accept that the early proteinuria in chronic
cadmium poisoning is of the tubular type and caused by decreased
reabsorption of proteins (Harrison et  al., 1968, Davis, Flynn
and Platt, 1968, Berggard  and Beam, 1968, Peterson, Evrin and
Berggard,  1969, and Rennie, 1971). However, Smith, Wells and
Kench in 1961 found in urine protein from two cases of chronic
cadmium poisoning a low molecula.r weight albumin, immunological ly
indistinguishable from normal serum albumin but with a consider-
ably lower molecular weight. They introduced 'the word "mini-
albumin" for this protein  which they considered the main feature
of chronic cadmium poisoning. Since their conclusions were
founded upon investigations of only two  samples, lyophilized and
stored for 8 years at room temperature before examination, fur-

ther data are needed,  (see also section* however).
Using the same methods, Piscator  (unpublished data) could detect
a small quantity of albumin in low molecular weight fractions ob-
tained by gel filtration from the urine of both normal men and
workers with chronic cadmium poisoning. Piscator considered this
due to the "tailing" of ordinary  albumin on the Sephadex column.

Vigliani, Pernis and Luisa. 1966, using specific anti-sera,
demonstrated that some 30 percent of the protein in the urine
from 3 Swedish cadmium workers consisted of L chains of  V -
globulin. These findings do not contradict the above mentioned
findings by Piscator despite the  fact  that Vigliani interpreted
his results as unfavorable to cadmium  proteinuria's being simply
an increased normal proteinuria caused by impaired tubular re-
absorption. In their first report, Vigliani, Pernis and Luisa,
1966, expressed the opinion that  cadmium proteinuria is mainly
caused by a defect in the assembling of polypeptide chains of
immunoglobulins, resulting in the excretion of low molecular
weight chains. Recently, in 1969, however, Vigliani abandoned
this theory in favor of the hypothesis that cadmium has an
effect upon the catabolism of immunoglobulins and other pro-
teins in the kidneys.

6.1.2,1.3  Renal stones
Especially in workers  in Sweden,  the formation of renal stones
has been a common feature (Friberg, 1950, and Ahlmark et al.,
1961). Ahlmark et al., 1961, found that 44 percent of a group of
workers exposed to cadmium dust for more than 15 years had a
history of renal stones. In 1963, Axelsson reported that the
stones were mainly composed of basic calcium phosphate. He stated
that the formation of such stones was  evidence of a disturbed
metabolism of calcium and phosphorus.

During later years, kidney stones have also been found in British
accumulator factory workers by Adams, Harrison and Scott, 1969.
It is noteworthy that both this later research group and Axelsson
in 1963 found a higher prevalence of renal stones in non-protein -
uric men, indicating that more developed tubular dysfunction means
less risk of developing kidney stones. This finding also indicates
that changes in reabsorption of calcium might occur early. Adams,
Harrison and Scott, 1969, stated that some of their workers had
hypercalcuria without proteinuria.Kazantais   (personal communica-
tion) has recently found renal stones in threevout of twelve work-
ers previously referred to (Kazantzis et al., 1963).

6.1.2. 1.4  Autopsy and biopsy findings
Information is available from a total of 11 autopsies (6 exposed
to cadmium oxide dust and 5 to cadmium oxide  fume) and 9 biopsies
(all exposed to cadmium oxide dust). In table 6:1 data are given
from 6 autopsies and 9 biopsies on workers exposed to cadmium
oxide dust.  In four of the autopsy reports (S;W;H., K.J., H. B.,
and A;B; ) the morphological changes in the kidneys were mainly
confined to the proximal tubules, whereas the glomeruli were less
affected.  Similar but less pronounced changes were seen in two
biopsies. In the other cases with morphological changes, the exact
nature of these has not been speci f ied./^The  data in the table
indicate that cadmium levels were lower in cases with morphologi-
cal changes than in cases without detectable  morphological altera-
tions, or with only minor changes. As exposure times were longer
in the former cases and the concentrations of cadmium dust con-
ceivably higher (after 1950 improvements in working conditions
were made in the Swedish factory), the lower  levels in these
cases can not be explained by less exposure.  There is some dif-
ference between the two groups in regard to the time which had
elapsed between the end of exposure and autopsy or biopsy. This
fact does not seem to have been of significance, though, as can

be seen if patients examined different times after the end of
exposure are compared. The combination of heavy exposure to cad-
mium, severe renal damage and relatively low levels of cadmium
in the kidneys indicates instead a considerable excretion of
cadmium. In workers with no impairment or only minor dysfunction
(latter group), the renal losses must have been smaller and thus
the renal levels of cadmium were higher.

The above mentioned findings in workers exposed to cadmium oxide
dust are further supported by data from autopsies on workers ex-
posed to cadmium oxide fumes. Smith, Smith- and McCall, 1960, re-
ported on autopies on 4 workers exposed for less than 10 years.
The autopsies were performed 5-18 years after the last exposure.
These workers had been removed from exposure because of respira-
tory symptoms. Proteinuria had been the only sign of renal im-
pairment in three of  them. Histological examination did not
reveal any renal alterations. Cadmium levels in the cortex were
between 150 and 395 ppm wet weight, i.e., in the same range as
in workers exposed to dust and without major renal changes.
Bonnell, 1955, on the other hand, reported on a worker exposed
for 32 years to fumes and autopsied only 2 years after the last
exposure. There was severe renal damage with both tubular and
glomerular involvement. The cadmium concentration in cortex was
relatively low, 62 ppm wet weight.

In animal experiments (section it has been shown that
morphological changes became evident and renal levels of cad-
mium ceased to rise after a certain period of exposure. Further
exposure then resulted in a lowering of the cadmium concentration
These findings agree  with the findings in exposed workers.

In conclusion, when a cadmium worker suffers severe renal damage
through the toxic action of cadmium, his kidney concentration of
cadmium will decrease considerably. Thus, he will have lower

levels in kidneys than a worker with only slight  renal  distur-
bances .   I.n_aJlil2aJLs_
Prodan,  1932, stated that renal lesions consisting of  fatty  de-
generations in the tubules developnd in cats given daily  oral
doses of 2, 10 and 100 mg of cadmium for  1-2 months. However,
controls were not included in the experiment and  no  certain   con-
clusions can be drawn from these results. Wilson, deEds and  Cox,
1941, added cadmium chloride to the diets of rats in concentra-
tions of 31, 63, 125, 250 and 500 ppm. Exposure time was  100  days,
after which the rats were killed. Histological examination showod
slight tubular changes and no glomerular  alterations in the  ani-
mals exposed to 63 ppm cadmium in the diet and no changes in  ani-
mals exposed to 31 ppm cadmium. Cadmium determinations  were  not
performed on the kidneys.

In 1950  Princi and Geever reported that they could not  find  evi-
dence of morphological changes in the kidneys of  dogs  subjected
to prolonged exposure to cadmium oxide dust or cadmium sulphide.
(average concentration: 4 mg Cd/m" ). They made routine  analyses
of urine but used only the boiling test,  and did  not detect  pro-
tein. In 1950, Friberg made a long-term experiment (for details,
see 5.2.2) in which he exposed rabbits for 3 hours a day  for 28
days per month for 8 months to about 8 mg cadmium iron  oxide
dust/m .  After 4 months of exposure, moderate proteinuria could
be demonstrated with the trichloracetic acid test. When the  ani-
mals were killed after 7-9 months of exposure, histological
examination did not disclose any structural changes. Cadmium
concentrations in the kidneys were generally between 300  and
700 ppm wet weight. When a group of rabbits was given  subcutane-
ous injection of cadmium sulphate,  0.65 mg  Cd/kg, 6 days a  week,
prpteinuria was demonstrated after 2 months. Analyses  of  cadmium


in the kidneys were not performed. Electrophoretic analysis of
urine proteins showed that the main component was not the same
as the one found in rabbits with kidney damage due to uranium
salts. In further experiments, Dalhamn and Friberg, 1957, found
that mainly tubular changes took place in rabbits injected with
cadmium, whereas the glomeruli were not affected.

Bonnell, Ross and King, I960, gave rats of both sexes an intra-
                                           Cd f
peritoneal dose of cadmium chloride (0.75 mg/kg) thrice weekly
(for details see After 5-6 months,  injections were
discontinued for 1-2 months. Thereafter, some animals were
given a reduced dose, while others were given no further injec-
tions. The total time for the experiment was  one year. Every
month animals were killed and histological examinations per-
formed. After 4 months of exposure, tubular  damage was evident.
From that time despite continued exposure there was no further
increase in kidney levels of cadmium; in fact, some decrease
in kidney concentration could be demonstrated (see figure 4:10).
After 4 months the renal concentration of cadmium was about 275
ppm wet weight and after 5 mo'nths, about 225  ppm. The correspond-
ing concentrations in cortexi would be about  400 and 325 ppm,

These data are in accord with the findings by Friberg, 1952. He
could show that rabbits given daily subcutaneous injections of
radioactive cadmium sulphate had very low urinary excretion of Cd
during the first two months,  while after 2  months of exposure,
the cadmium excretion abruptly increased 50-100 fold  (see figure
4:11). After one month of exposure the renal  concentration of
cadmium was on an average 126 ppm wet weight  whereas after
2 1/2 months of exposure the average concentration was 213 ppm.
Friberg reported also that the concentration  in cortex was
about 5 times higher than in medulla which means that in cortex
the concentrations would have been about 200  and 350 ppm,
respectively, under the assumption that the  mass of cortex is

equal to or slightly larger' than that of  the  medulla.   In  later
experiments, Friberg, 1955, ; alternating radioactive  and nonradio-
octive cadmium, demonstrated that a  large part  of  the  excreted
cadmium must have come fromi deposits in the kidneys.

Axelsson and Piscator, 1966a, gave rabbits subcutaneous injec-
tions of cadmium chloride,  0.25 mg Cd/kg  5 days  a  week. After
17 weeks, alkaline phosphatase activity of the  renal cortex  de-
cre-ased. After 23 weeks there was a  decrease  in  the  capacity to
reabsorb glucose, together  with considerable  proteinuria and
excretion of cadmium. Histological examination  (Axelsson,  Dahlgren
and Piscator 1968) revealed that already  after  11  weeks mild
alterations took place in the proximal tubules.  At that time
cadmium concentration in the renal cortex was about  250 ppm
wet weight (range:194-315). After 23 weeks, pronounced  changes
were found not only in the  proximal  tubules,  but also  in other
parts of the nephron. The collecting tubules  were  not  detectably
affected. Though the glomeruli showed some slight  alterations in
some cases, most cases were without  demonstrable alterations.

In another group of rabbits, exposure conditions were  similar
to those stated above, but  exposure was discontinued after 24
weeks, after which the animals were  followed  for another 30
weeks. Urine investigations showed that protein  excretion  was
significantly higher than in controls after 12 weeks of expo-
sure, with a maximum at about one month after exposure  had
ceased.  Then came a reduction in protein excretion. At  the end
of the observation time, there was no significant  difference
between exposed animals and controls. Electrophoretic  examina-
tion of urinary proteins showed a predominance of  proteins with a
mobility as ^ - and //-proteins. It was concluded  that  this  cor-
responded to the tubular proteinuria found in human beings.  Be-
fore these animals were killed,  kidney function  was  investigated.

After death, alkaline phosphatase activity and cadmium in renal
cortex were determined, as described by Axelsson and Piscator,
1970. Glucose reabsorption and protein excretion did not differ -
significantly between exposed and control animals. However, a
highly significant decrease in the activity of alkaline phospha-
tase was found. The renal cortex in the exposed animals contained
large amounts of cadmium, about 250 ppm wet weight, despite the
fact that the rabbits had been without exposure to cadmium for
30 weeks (see also Morphologically, there was an al-
most complete regeneration of the tubular epithelium. It was
concluded that in the rabbit, exposure to cadmium would give
rise to renal tubular damage, partly reversible, as judged by
functional and morphologic/investigations.

It was mentioned earlier  (section that Kench and co-
workers have reached the  opinion that the excretion of a low
molecular weight albumin  is the main feature of the proteinuria
in chronic cadmium poisoning in man. In experiments on rabbits
(Kench, Wells and Smith,  1962), on monkeys (Kench, Gain and
Sutherland, 1965, and Kench and Sutherland, 1966), and on rats
(Kench and Sutherland,  1966), they were able to isolate an al-
bumin of low molecular  weight (10,000) from urine. In these ex-
periments, however, animals were given very large doses of cad-
mium by intravenous injections (2 mg/kg twice a week) or a single
intraperitoneal injection (15 mg/kg.). Thus, the experimental con-
ditions did not reproduce the slow chronic cadmium poisoning in
man. At present, these  experiments are indicative that large
doses of cadmium may cause profound changes in protein meta-
bolism. More evidence is  needed before these experimental results
can be applied to chronic cadmium poisoning in man.

In some reports, such as  those by Princi and Geever in 1950 and
by Anwar et al. in 1961,  no effects on the kidneys were reported.

despite prolonged exposure to cadmium. Princi  and  Geever  stated
that "in no case was tubular damage  found  in the kidneys  (such
as might be expected from severe metal poisoning)."  Milder
tubular lesion, often reported in  chronic  cadmium  poisoning,
might not have been registered. Princi and  Geever  found rela-
tively large amounts of cadmium in the blood (38-119 /ug/100  g
whole blood) and urine (32-382 jjg/liter) of dogs exposed  to  cad-
mi urn oxide dust and, to some extent,  in  dogs exposed to cadmium
sulphide. However, kidney levels were  low,  in  the  same range as
those for normal human beings. On  the  other hand,  large amounts
of cadmium were found in the liver (12-47  ppm  in dogs exposed
to cadmium oxide), bile and feces. The authors  do  not mention
whether the values are calculated  as  ppm wet weight  or dry
weight. We have assumed that they  are wet weight values.

Anwar  et al. gave a total of  8 dogs  cadmium in drinking water  for
4 years  in  concentrations ranging  from 0.5-10  ppm. One  additional
dog was  used as control. They  stated in  their  summary  that patho-
logical  changes were not produced  in dogs  receiving cadmium. How-
ever,  in their textual discussion, they  described  the  findings
of  larger   amounts  of  fat in  the  proximal  convoluted tubules
and in some areas,  atrophied  tubules,  in one  dog  from  each of
the two  groups  receiving the  higher  concentrations (2  dogs:  5
ppm, 2 dogs: 10 ppm).  As the  authors thought  that some  animals
also were  infected  with Leptospira,  they concluded that  some of
the changes might be due to  leptospi rosis .  Because of  the small
number of  dogs  used, the data  are  of limited  value and  in any
case can not be taken  as evidence  that long-term  exposure to
orally ingested cadmium will  not  give rise to  kidney damage.   Me£ha_ni^sms_f£r_th_e_de_ve_l£pmen_t_o£ the_
 It  has been  shown  that  cadmium will  accumulate in the  kidneys.
 During the period  of  accumulation,  only  small  amounts  of cad-

mium will be excreted in the urine, whereas, when a certain
concentration has been reached in the kidneys, cadmium excre-
tion will increase and renal levels will remain the same or

A hypothesis on the development of renal injury as advanced at
our institute will now be set forth.  In section 4.2.8 it was
said that cadmium is probably transported to the tubules bound
to the low molecular weight protein,  metallothionein. During
normal conditions this protein will bo reabsorbed in the tubules
just as other proteins, and cadmium will accumulate in the renal
tissue. Cadmium excretion in "normal" people and in workers with
short periods of exposure to cadmium is thus low because proteins
are almost completely reabsorbed. With increasing exposure, more
cadmium than can be bound by metallothionein will eventually be
accumulated in the kidneys. Cadmium will then exchange with zinc
in enzymes necessary for reabsorption and catabolism of proteins.
Chiappino, Repetto and Pernis, 1968,  found inhibition of the
leucine-aminopeptidase activity in the renal cortex of cadmium
exposed rats and in rabbits exposed under similar conditions as
in the experiments by Axelsson and Piscator in 1966a. Leucine-
aminopeptidase is a zinc-dependent enzyme thought to play a
role in the renal handling of proteins. As a result of these
antienzymatic actions less protein will be catabolised or re-
absorbed, causing tubular proteinuria. Cadmium excretion will
increase as also less metallothionein wi11 be reabsorbed. At
this stage the accumulation rate of cadmium will become slower,
but cadmium will still be reabsorbed and cadmium levels in
the tissue may get still higher. The reabsorption defect will
be greater and eventually renal cadmium will cease to increase.
Tubular cells will be damaged by cadmium and it is conceivable
that cadmium will be excreted together with desquamated tubular
cells, resulting in a decrease in renal levels of cadmium. If

glomerular function is impaired, there  will also be  less  fil-
tration of metal loth ionei n .

What has been described above might be true  in  continuous  ex-
posure.  If exposure is discontinued when there is slight  or
no proteinuria, there is a possibility that  cadmium  levels  in
kidneys will increase for some time, probably depending  upon
liver levels. Proteinuria may thus appear some  time after  ex-
posure has ceased, as supported by findings  in  workers removed
from exposure (Friberg and Nystrom, 1952) and in animals
(Axelsson and Piscator 19G6a). The mechanisms mentioned  above
might also explain the poor correlations between proteinuria
and cadmium excretion in workers (Smith and  Kench, 1957),  as
the former will depend mainly on the tubular dysfunction while
the latter will depend upon both this dysfunction and  the  a-
mount of metal loth ionei n produced in the body,  which  in  turn
will depend upon recent exposure.

The findings in autopsy cases of chronic cadmium poisoning  and
in biopsies from exposed workers presented a paradox,  i.e., high
levels of renal cadmium were combined with h istologi cal ly  normal
kidneys while relatively low cadmium levels  were combined  with
long-standing proteinuria and gross structural  changes in  the
kidneys. The above mentioned mechanisms will explain  this  para-
dox, i.e., the more severe and long lasting  the renal  lesion,
the more cadmium will be excreted.
In order to evaluate dose- response  relationships,  concentra-
tions of cadmium in the kidneys at  different  effect  levels  would
probably be the most valid information.  Seemingly  less. valid
factors - exposure through food and  air  ,  or  concentrations in
blood and in urine-will first be  discussed.

                                                            6-20.  Evaluations starting from data on exposure in the en-
           vi ronment
The amount of cadmium that gives rise to kidney damage can
theoretically be evaluated from data on environmental exposure
(concentrations in food, water, industrial or ambient air) in
relation to effects. Unfortunately, available data are too in-
adequate to provide quantitative evaluations of the dose. Work-
ers in industries, for example, have often been exposed  for de-
cades. Determinations of cadmium in air, on the other hand,
have been performed only occasionally, and often show that ex-
posure varies considerably within  the same working place. Mea-
surements in the breathing zone of the workers have seldom been
performed. Further, the use of respirators may change the expo-
sure situation considerably. The long-term evaluation of ex-
cessive exposure via ingestion of  cadmium is hindered by sim-
ilar problems, as exemplified  in Chapter 8, where the Itai-itai
disease in Japan is disc.ussed.

6.  Evaluations starting from data on cadmium concentrations
           in blood and urine
As can be realized  from the detailed discussion in section 4.4,
cadmium levels in blood and urine  are of very limited value
for evaluating dose-response relationships. Blood levels can not
be used for estimating renal levels because they might vary con-
siderably during exposure, while the kidneys will accumulate cad-
mium continuously up to a  certain  level  (when damage will occur).
Though increased blood levels  show that exposure has taken place,
it will be impossible to differentiate whether they reflect accu-
mulated cadmium or  recent  exposure.

Neither can cadmi um concentrations i_ri urine be used, as  during
the period the kidneys are accumulating cadmium, there is not
a  corresponding increase in urinary excretion of cadmium. When

an increase in urinary cadmium levels can be seen,  renal  dys-
function will have already taken place  (Section 4.4.).  Evaluations starting from data on cadmium  concentrations
           in the kidneys
In table 6:1 data are given on workers  industrially exposed
for long periods to considerable amounts of cadmium.  As  can  be
seen,  the concentrations of cadmium in  the renal cortex  have
varied within wide ranges. In section it  was con-
cluded that the low values found in workers with morphologi-
cally  pronounced kidney damage resulted not from low  expo-
sure but from high excretion of cadmium. In table 6:1  there
can also be seen a group of workers with long exposure to cad-
mium but with no or only slight morphologically detectable
kidney damage. Only some of them had proteinuria. It  can  be
assumed that the kidney levels of cadmium in such a group
would  be fairly representative for concentrations at  the  time
at which the first signs of renal dysfunction appeared.  Re-
ported levels in such cases did, with one exception,  vary
between 150-450 ppm wet weight in renal cortex.

In the experiments on rabbits and rats  (section  func-
tional and morphological changes appeared when the  cadmium con-
centration in the renal cortex reached  about 200-400  ppm  wet
weight. Renal levels  of about 130 ppm  wet weight,  corresponding
to about 200 ppm wet weight in renal cortex (only one-month  ob-
servation time), were found in rabbits  with neither proteinuria
nor excretion of cadmium. The animal experiments thus  suggest
that about 200 ppm wet weight is a critical concentration in
the cortex.

Even if animal data are not immediately valid for man, it is
striking that they are within the range fo'r human beings  exposed

to cadmium for several years and with slight or no impairment.
It is considered justified to start out from a value of 200
ppm cadmium in renal cortex  (wet weight) when discussing which
exposures can bring about cadmium-induced detectable renal dys-
function in man. It should be strongly emphasized that with
renal dysfunction is here meant a dysfunction that has been
detected with fairly crude mefehods. With all probability cellu-
lar effects will appear at considerably lower levels. Further,
not much thought has been given to individual variations in

G.  Estimations of how much long-term exposure is
           required to cause the human cortex to reach con-
           centrations of 200 ppm (wet weight)
The calculations refer to a  70 kg "standard man" and a total
kidney weight of 300 grams.  The cadmium concentration in cortex
has been assumed to be 1'.5 times the average kidney concentra-
tion  (section

As has been discussed in section 4.3.4 approximately one-third
of the  total amount of absorbed cadmium can be estimated to be
in the  kidneys in a "normal", a man not excessively exposed to
cadmium. It is not known exactly what proportion will be in the
kidneys in relation to other organs after long-term exposure to
cadmium in amounts eventually giving rise to the critical level
of 200 ppm (wet weight) cadmium in renal cortex. As was discussed
in section 4.3.4, there is no reason to believe that the pro-
portions will differ considerably from what has been estimated
for a "normal" man. A decrease to about 25 percent is possible
but not probable.

In table 6:2 estimations have been entered on minimum cadmium
levels, via ingestion or inhalation, necessary for reaching 200

ppm wet weight in renal cortex after different exposure times
and different assumed absorption percentages. The results show,
for example, that with 50 years' exposure, a daily intake via
the peroral route of about 100-150 yug cadmium with a 5 percent
absorption may give rise to renal dysfunction. With a 10 percent
absorption, corresponding values would be about 50-75 yjg cadmium
Renal dysfunction could be reached via inhalation of cadmium in
the ambient air in concentrations of about 1-1.5 yug/m  if a 25
percent absorption is postulated. Corresponding values for a 40
percent absorption would be about 0.5-1.0
The values in table 6:2 refer to cadmium levels in renal cortex
which may give rise to renal dysfunction with proteinuria and
other effects. Such values of course can not be accepted as "safe"
values.  In table 6:3 similar calculations have been made but the
starting point has been a total body burden of 30 mg cadmium
(values  of a magnitude reported for "standard American man")
corresponding to about 50 ppm (wet weight) in renal cortex.
Such a kidney concentration would be reached with a daily per-
oral intake of about 25-40 ijg of cadmium with 50 years' expo-
sure and an assumed absorption of 5 percent. With an absorption
of 10 percent the necessary daily intake would amount to
about 12-20 jug. For exposure via ambient air a concentration
of about 0.25-0 . 4 ug/m  would suffice, with an assumed absorp-
tion of 25 percent of . inhaled cadmium. With an absorption of
40 percent concentrations of about 0.12-0.25 ug/m  would con
stitute a critic-al level.
Similar tables and calculations, of course, can be made for
other alternatives. If one would like, for example, to con-
sider the consequences of lowering the present renal cadmium
level in the United States with a factor of 2, the values in
the table should be divided by 2.

6.2.1  Acute  effects  and  dose-response  relationships
Effects  on  the blood  after respiratory  exposure  to  high  concentra-
tions  of cadmium have been noted both  in  human beings  (Beton  et
al.f 1966)  and in animals  (Prodan,  1932).  Beton  et  al.  found
elevated levels  of hemoglobin  in some  subjects.  This elevation
was probably  connected with  the hemoconcentration caused by the
oedema of the lungs.  A hemolytic effect after a  single  injection
of cadmium  sulphate  into  a dog (about  25  mg Cd/kg)  was  noted  by
'Athanasiu and Langlois in  1895, but  it  is  not known if  acute
respiratory exposure  in human  beings has  ever given rise to
such an  effect.

It is  not possible to establish any  dose-response relationships
with regard to effects on  the  hematopoietic system  in  man or
animals  after acute  expos'ure.  There  is  a  lack of data  and the
oedema of the lungs  and the  general  toxemia will probably over-
shadow any  other effects.

6.2.2  Chronic effects and dose-response  relationships
6.2.2. 1   JLn_h-uma.n_be_i£gs_
Anemia has  been  described  in workers exposed  to  cadmium oxide
dust (Nicaud,  Lafitte and  Gros, 1942,  and Friberg,'  1950) and
cadmium  oxide fumes  (Tsuchiya, 1967) but  is usually moderate.
In a group  of 16 workers  exposed for 5-30  years  to  cadmium, a
significant correltion was found between  high cadmium  levels  in
blood  and low hemoglobin  levels.  (Piscator, unpublished data).
The number  of white  cells  is generally  normal, but  there is an
increase in the  number of  eosinophile exposed  workers
(Nicaud,  Lafitte and  Gros,  1942, Princi,  1947, and  Friberg,
1950). No explanation has  yet  been  given  .

The bone marrow was examined microscopically by Friberg,  1950,
in 19 cadmium exposed workers but no pathological changes were
found.  2.n_aH^H!a2.s_
Anemia has been a common finding. Wilson, deEds and Gox,  1941,
gave rats food containing 31-500 ppm cadmium and found that the
lowest dose gave animals anemia after a couple of months. After
exposure had ceased, there was a tendency to normalization in
hemoglobin levels. In a group given 125 ppm cadmium for  up to 7
months, they noted also increases in reticulocytes and eosino-
phils. Examination of the bone marrow showed that it was  hyper-

Decker et al., 1958, noted that hemoglobin levels had already
decreased considerably after 2 weeks in rats given 50 ppm cad-
mium in drinking water. On the other hand, rats given 10  ppm
in water for one year did not become anemic. Friberg, 1950,
found that rabbits exposed to cadmium oxide dust developed a
slight anemia. A prominent finding was eosinophilia, as  25 per-
cent of the white cells in exposed rabbits were eosinophils
compared with 3 percent in a control group. In rabbits injected
with cadmium sulphate (0.65 mg/kg), 6 days a week, pronounced
anemia was evident after two months of exposure.

In further studies (Friberg, 1955, for exposure conditions, see
section it was found that simultaneous administration
of iron had a beneficial effect on the anemia, indicating that
the anemia was partly due to iron deficiency. By giving   Fe
to cadmium exposed rabbits (1 mg Cd/kg, 6 days a week, subcu-
taneous injection) , one group receiving the isotope before ex-
posure, another group receiving it after 2 months' exposure,
and comparing with controls, Berlin and Friberg, 1960, could

show that there was an increased destruction of erythrocytes,
even of those formed before exposure. There was no certain dif-
ference between controls and exposed animals with regard to
utilization of iron for hemoglobin synthesis. The beneficial
effect of parenterally given iron also indicated that cadmium
did not block hemoglobin synthesis, but that there could be a
decreased uptake of iron from the intestines. Berlin and Friberg
did not observe any decreased osmotic resistance in the erythro-
cytes as described by Swensson, 1957. Berlin, Fredricsson and
Linge, 1961, found that in rabbits given cadmium there were in-
creased deposits of iron in the bone marrow but no decrease in
erythropoietic activity. They found some other changes in the
bone marrow, but as the rabbits were rather severely intoxicated
after having received subcutaneous injections of 1 mg Cd/kg
daily .for several months, these changes were regarded as non-
specific and produced by general toxic effects. In a group of
rabbits followed after exposure (24 weeks, 0.25 mg Cd/kg, 5
days a week) ceased, hemoglobin levels rose again but were
still  significantly lower than those in a control group 30
weeks later (Piscator and Axelsson, 1970).

Fox and Fry, 1970, found that ascorbic acid had a beneficial
effect on the cadmium produced anemia in Japanese quail. They
thought that improved utilization of iron through the action
of ascorbic acid was responsible for the beneficial effect.

Berlin and Piscator, 1961, studied blood and plasma volume in
cadmium poisoned rabbits and concluded that the anemia could
partly be explained as caused by increases in plasma volume.
Axelsson and Piscator, 1966b, made long-term experiments on
rabbits (for details, see.section and found that
after 11 weeks of exposure, there was ahaptoglobinemia, in-

dicating hemolysis. They  thought  at  that  time  that  in  the  chron-
ically exposed  rabbit cadmium would  be  transported  to  the  renal
tubules together with hemoglobin  released through hemolysis.
However, recently. Nordberg, Piscator and Nordberg  (unpublished
data) have  found that cadmium in  erythrocytes  from  exposed mice
is stored also  in a low molecular weight  protein, probably
6.2.3  Dose-response relationships
The investigations on animals given  injections  of  cadmium  have
indicated that during exposure anemia will be  related  to the  accu-
mulated dose  (Friberg, 1955, Berlin  and Friberg,  1960,  Berlin and
Piscator, 1961 and Axelsson and Piscator,  1966a),  but  that  as soon
as exposure has ceased, hemoglobin levels will  tend  to  rise again.
When given cadmium in'drinking water in concentrations  between
0.5 and 10 ppm for one year, groups  of rats did not  differ  from
one another with regard to hemoglobin levels  (Decker et al.,  1958).
At these exposure levels, there was  thus no dose-response  rela-
tionship. Hemoglobin levels dropped  rapidly,  however,  in rats
given 50 ppm  in the watert. The accumulated amount of  cadmium
could not be  related to the anemia since levels in kidneys  and
liver were higher in rats exposed for one year  to  10 ppm in water
that in rats  given 50 ppm for 3 months.

With regard to human exposure, it is impossible at present  to any statement on dose-response  relationships.

6.3.1  Acute effects and dose-response relationships
Dalhamn and Friberg, 1954, found that an intravenous injection
of cadmium sulphate (0.3-0.5 mg Cd/kg) caused a rapid  fall  in

blood pressure within 15 seconds in the cat and the rabbit.
Perry and Yunice, 1965, found that an int raarterial injec-
tion of 0.1-0.4 mg/kg caused increased diastolic blood pres-
sure in rats, whereas larger doses (0.8-3 mg/kg) caused de-
creased pressure.  Schroeder et al., 1966, found an incre'ase
in the systolic pressure after an intraperi toneal injection
of 1-2 mg cadmium as cadmium citrate in rafes. Hypertension
was produced in rats by intravenous injections of cadmium
in doses of 0.02-2 mg/kg (Perry et al., 1970) and by intra-
peritoneal injections of 0.2-2.4 mg/kg (Perry and Erlanger,
to be published). The last mentioned authors also found con-
siderable increases in renin activity in blood of rats given
an intraperitoneal dose of about 1 mg Cd/kg. The maximum
activity was observed 8 hours after injection but a significant
increase took place up to one month after injection.

6.3.2  Chronic effects and doge- response relationships
6 . 3.2 . 1  In  In exposed workers
Friberg,  1950, examined 43 workers with a mean exposure time to
cadmium oxide dust of 20 years and 15 workers with a mean expo-
sure time of 2 years. The study included physical and roentgeno-
logical examination of the heart, electrocardiographic examination
at rest and after exercise, and the measurement of blood pressure.
No increased prevalence of cardiac disease was found. Electrocar-
diographic changes occurred to the same extent as in a group of
sawmill workers without exposure to cadmium. The majority of the
workers had completely normal blood pressures. Nothing supported
an assumption of higher frequency of hypertension in the cadmium
workers than that normally expected in workers in relevant age
groups. As Friberg did not examine a control group, with regard
to the prevalence of hypertension, it is impossible to use his

data for a more precise evaluation.

Chest examinations and blood pressure measurements have also
been made in other studies (Bonnell, 1955, Bonnell, Kazantzis
and King, 1959, Kazantzis et al.,  19G3, and Holden, 1969) but
none of the resulting reports contained findings of cardiac
disease or hypertension.caused by  cadmium exposure,  In the general population
Cadmium has been incriminated as one of the factors that may
cause hypertension in human beings  (Schroeder, 1964, 1965, and
1967).   Data by Tipton and Cook, 1963, shows that the cadmium
to zinc ratio was higher in people whose deaths were related to
hypertension than in other groups. Subjects dying of malignant
hypertension with renal failure had low values of both cadmium
and zinc in the renal tissues, presumably due to loss of renal
tissue. In earlier studies, it had been shown that patients with
hypertension excreted more cadmium  than did controls (Perry and
Schroeder, 1955). These findings,  supported by findings in cadmium
exposed animals (see next section), initiated epidemiological

Carroll, 1966, found a correlation between cadmium concentrations
in the  air of 28 American cities and death rates from hyperten-
sion and arteriosclerotic heart disease. Hickey, Schoff and
Clelland, 1967, made a similar study covering 26 cities and
found that cadmium together with vanadium was correlated with
mortality in heart disease. Hunt et al., 1970, upon reanalysis
of Carroll's data, reported a higher correlation between pop-
ulation density and death rates than between cadmium concentra-
tions in air and death rates.

Hunt at al.,  1970, made a study of 77 cities in the Middle West
of the United States with populations varying between 100,000
and 1,000,000. Cadmium, lead and zinc were measured in the dust-
fall in residential, commercial and industrial areas from Septem-
ber to December,  1968. Cadmium in milk was also determine-d in
the selected areas. The age-adjusted cardiovascular death rate
for 1959-1961 was studied against ten independent variables:
   Population density, dustfall, cadmium, lead zinc fallout,
total precipitation, average maximum and minimum temperatures
and cadmium and lead concentrations in milk. The authors did
not find a significant relationship between cadmium fallout
and mortality from cardiovascular disease in residential, com-
mercial or industrial areas. There was, however, a significant
relationship between mortality and each of the following in-
dependent variables: dustfall, lead fallout, and maximum and
minimum temperatures, in the residential areas. Minimum tem-
perature was the  only variable significantly related to cardio-
vascular mortality in the commercial and industrial areas.

Pinkerton and Murthy (personal communication) found a significant
correlation between cadmium levels in milk and cardiovascular
mortality in 58 cities in the United States. Population density
was not taken into account, and it is possible that urbanization
played a role. Furthermore, the levels reported for cadmium
in milk by Pinkerton and Murthy are considerably higher than
those stated in other reports (see Chapter 3). As they used the
atomic absorption method without extraction of the metal, the
possibility that  sodium chloride in milk influenced the analysis
can not be excluded.

Morgan, 1969, determined renal cadmium in autopsy cases and
did not find differences between a group with hypertension
and a control group. However, in Czechoslovakia, Lener (per-

sonal communication)  found  that  in  a  group  of  12  people  (mean
age:62) with histories of hypertension,  cadmium  concentrations
in kidney were 36 ppm wet weight, significantly  higher than  in  a
control group of 10 people  (mean age:59) with  a  concentration of
27 ppm wet weight.  Finally  it must be mentioned  that'according
to a report by Nogawa and Kawano, 1969,  hypertension  has  not
been found in patients with  Itai-itai  disease  nor in  people
living near the endemic  district where the  Itai-itai  disease
is found in Japan (see section 8.4).

'  In animals
Hypertension has been produced  in  rats  of  the  Long  Evans  strain,
especially in female rats, by giving  them  cadmium in  drinking
water for long periods of time  (Schroeder  and  Vinton,  1962,
Schroeder, 1964, and Kanisawa and  Schroeder,  1969b).  Control
rats were given a special cadmium-free  diet and  the animals
to be exposed were gi«ven 5 ppm  of  cadmium  (as  chloriJe)  in double
deionized water together with essential  elements.   In  rats
receiving cadmium in drinking water,  hypertension usually was
manifest after one year. When cadmium was  given  in  hard water
(Schroeder, Nason and Balassa,  1967)  there was less hypertension.
Analysis of cadmium in tissues  revealed  that  cadmium  concentra-
tions in the kidneys and liver  were of  the same  magnitude as
in American adults, around 40 /Lig/g and  6 tig/g  wet weight,  on an
average, respectively.  (In an  earlier  investigation  of Schroeder
and Vinton, 1962, with the same exposure conditions,  values
of only about one-tenth of these were reported).  When  t'he  cad-
mium to zinc ratio was above 0.8,  the animals  were  always hyper-
tensive. Histological examination  (Kanisawa and  Schroeder,
1969) disclosed renal, arterial, and  arteriolar  lesions.  Accord-
ing to these authors, the changes  were  indistinguishable  from
those accompanying benign hypertension  from other causes.

Hypertension has also been induced by parenteral injection of
cadmium salts. Schroeder et al., 1966, and Schroeder and Buckman,
1967, found that when one or two intraperitoneal injections of
cadmium citrate (1-2 mg Cd/kg) were given, hypertension develop-
ed and, over a month's period, became equal to the hypertension
appearing in rats on which partial constriction of one renal
artery had been performed. Similar results are reported by
Chiappino and Baroni, 1969, in Spraque-Dawfey rats.  They also
found a hyperplasia of the juxtaglomerular apparatus; and of
the glomerular zone of the adrenal cortex. They concluded
that the renin-aldosterone system probably was stimulated.

Recently Thind et al., 1970, have been able to induce hyperten-
sion in rabbits given weekly intraperitoneal injections of cad-
mi urn acetate  (2 mg/kg) for 7 weeks. During that period mortality
Was 25 percent. A decrease in vascular responsiveness to angiot
tensin was suggested as playing a role in the pathogenesis of
cadmium hypertension.

Schroeder, Nason and Mitchener, 1968, discontinued exposure to
cadmium after 515 days, when rats were hypertensive.. They found
a lowering of the blood pressure and after 715 days, blood pres-
sure was normal.

The hypertension induced by cadmium could be reversed by giving
the chslating agent Cyclohexane-1,2-diamine-NNN'N'-tetraacetic
acid (CDTA), which binds cadmium more firmly than zinc (Schroeder
and Buckman,  1967). When the disodium zinc chelate was given
by intraperitoneal injection to nine rats previously given cadmium
in drinking water, blood pressure was normal in all after 2
weeks. However, in rats given cadmium by injections, repeated
treatment with the chelate was sometimes necessary to achieve
normal blood pressure. After treatment, there was a decrease

in cadmium levels in the kidneys and the authors concluded
that the lowering of the cadmium to zinc ratio could be the
cause of the decrease in blood pressure. For a discussion of
the possible toxic effects of cadmium chelates, see section

There are also negative findings in regard to cadmium and
hypertension.  Lener, 1968, Lener and Bibr, 1970, and Lener
(personal communication) reported that hypertension did not
appear when Wistar female rats were given cadmium in drinking
water (5 ppm) and observed for 16 months. When Long Evans
rats were put on 2 percent NaCl for 12 days and then given
three intraperitoneal doses of cadmium citrate (1, 1 and 2
mg/kg) with intervals of 1 and 2 weeks, repeated determinations
of blood pressure up to 4 weeks after the last injection did
not show hypertension.  Castenfors and Piscator (unpublished
data), using female Spraque-Dawley rats, could not induce
hypertension by giving them injections of cadmium chloride
(0.5 mg Cd/kg) 3 days a week for 6 months. In another experi-
ment the rats were given cadmium in drinking water (5 ppm)
for one year, but monthly determinations of blood pressure
did not show any difference compared with controls. At the
end of this experiment, the intraarterial blood pressure had a
mean value in 13 exposed rats of 1.53 mm Hg (S.D.: 16) com-
pared with 151 (S.D.: 22) in 9 controls.  Lener (personal com-
munication) found that when a group of Long Evans rats were
put on 2 percent NaCl for 50 days before receiving 2 doses
of cadmium citrate (2 mg Cd/kg) with an interval of 84 days,
there was a significant increase in systolic blood pressure
in the cadmium exposed animals. Perry, Perry and Purifoy (to
be published) produced permanent sodium retention in female
rats with 4 injections of cadmium (1 mg/kg) at 1-month intervals
Vander,  1962, had earlier shown that intravenous doses of a

cadmium-cysteine complex enhanced sodium reabsorption in the
renal tubules. Thus both strain differences and sodium intake
might be determining factors in the development of hyperten-
sion in experimental animals.

6.3.3  Discussion and conclusions
Since the possibility that cadmium produces cardiovascular
disease, especially hypertension, has attracted much interest
during recent years, a special discussion on this subject is

The fact that hypertension has been associated with high kidney
levels of cadmium in certain studies can not be used for firm
conclusions concerning causality. The data have been obtained
by analyses of kidneys from people who died from vascular dis-
ease.  Nothing has been stated about the previous history or
the course of the disease, and the interpretation of the data
is subject to the usual difficulties met in this type of epi-
demiological analysis.

The results from epidemiological investigations are hitherto
ambiguous.  They have been obtained by associating cardiovas-
cular disease with dustfall data or cadmium concentrations in
air. Other, more important sources of cadmium exposure have not
been considered. The average cadmium concentration in a  "stan-
dard American man" seems  to be around 30 mg in  the age range of
40-50 years  (section 4.3.4). Even with such a high average cad-
mium concentration in the ambient air as 0.01 bg/m , the total
amount of  cadmium absorbed over a 50-year period would amount
to  only a  small  fraction  of  the total body burden. An absorp-
tion rate  of  inhaled cadmium of 25 percent and  a lung ventila-
tion of 20 m  /day would  thus give a total uptake of less than

1 mg of cadmium over a 50-year period. The cadmium fallout, of
course, could influence the cadmium levels of various foodstuffs
It does not seem probable, however, that the average cadmium in-
take via food by city dwellers in the U.S. is very much de-
pendent upon the local ambient air concentration of cadmium.
It was pointed out by Hunt et al. 1970, that population den-
sity is a factor of importance. Furthermore, smoking must be
taken into account.

In certain areas of Japan where there has been a considerable
exposure to cadmium for decades, hypertension has not been
associated with cadmium.. In addition, there are no reports
showing that workers exposed to cadmium have a higher pre-
valence of hypertension than other groups.

The results from investigations on animals are also ambiguous.
It is true that studies show that intraperitoneal injections
of cadmium will induce hypertension in rats and rabbits. Long-
term exposure via the oral route wi£h relatively low concentra-
tions of cadmium has induced hypertension in rats. There are
also negative findings and strain differences as well as other
factors might influence the response in rats When cadmium is

Even if thus far the available data do not support a hypothesis
that cadmium is causually associated with cardiovascular disease
in man, there are reasons to study the question further. The
findings, particularly in the animal studies, but even in the
epidemiological studies on human beings, merit further attention,
Epidemiological studies should be carried out on a longitudinal
basis with due consideration given to routes of exposure other
than air. Industrial workers with known exposure to cadmium

should be included in such studies. More animal experiments
should be developed, with particular emphasis upon the mechan-
isms of cadmium-induced hypertension, as the reasons for the
differing results reported by various investigators are not
Cadmium  does not accumulate to any considerable extent in osseous
tissue, as discussed in section A direct effect of cad-
mium upon such tissue is therefore unlikely. However, there is
evidence that the regulation of the calcium and phosphorus bal-
ance by the kidneys can be disturbed by cadmium exposure (see
section A disturbed calcium and phosphorus balance
can in turn give rise to bone changes but even though the ef-
fect upon the calcium balance becomes grave within a very short
time, the symptoms and changes in the skeleton require consider-
able .time to develop. Acute effects on bone are not reported
and the following account on effects on bone is concerned only
with long-term effects.

6.4.1  In human beings
Nicaud, Lafitte and Gros, 1942, described a group of workers
exposed to cadmium oxide dust in an accumulator factory. In
2 men (ages: 41 and 60; exposure time: 11 years), 3 married
women (ages: 48, 51 and 60; exposure times: 8, 16 and 14 years)
and one unmarried woman (age: 37; exposure time: 10 years),
there were symptoms of pain in the back and extremities and
difficulties in walking. Roentgenological examination disclosed
in all 6 workers lines of pseudo-fractures, especially in the
shoulder-blades, pelvis, femur and tibia. Proteinuria was not
found, but only the boiling test was used. The possibility of
tubular proteinuria can not be excluded. Later studies using

nitric and trichloracetic acid on other workers in that factory
(Friberg, 1950), revealed the presence of proteinuria. Electro-
phoretic examination of urine from one worker revealed that
it was the same type of proteinuria as was seen in the Swedish

Friberg made a roentgenological study of the skeletons of 11
workers from a group of 43 exposed to cadmium oxide dust for
9-34 years (for further details, see section but bone
changes were not found. Bonnell, 1955, found at autopsy severe
decalcification in a cadmium worker exposed to cadmium oxide
fume for 32 years. He died from chronic renal failure. Before
his death, proteinuria had been found at repeated examinations.
Electrophoretic analysis revealed that this proteinuria was
of the type common in chronic cadmium poisoning.

Gervais and Qelpech, ' 1963, found in 8 male workers (ages:49-
63; exposure times: 8-30 years) exposed to cadmium oxide fume
(7 of them) and cadmium oxide dust (1 of them) the same lines
of pseudo-fractures as described by Nicaud, Lafitte and Gros,
1942. These workers had not been exposed for 10-20 years and
the symptoms were diagnosed after exposure had ceased. In most
cases there was proteinuria which the authors   blarred upon
lead. Recently, Pujol et al., 1970, have shown that in a work-
er with bone changes in the same factory, tubular proteinuria
and other signs of tubular impairment were present.  Adams,
Harrison  and Scott, 1969, found one case of osteomalacia in
a group of workers exposed to cadmium oxide dust. These authors
expressed little doubt that this osteomalacia was caused by
renal disease since the worker had multiple tubular defects.

Chronic cadmium poisoning in  combination with certain dietary
deficiencies, i.e. lack of calcium and Vitamin D, seems to be

the causative agent for the Itai-itai disease, a bone disease
in Japan  (see Chapter 8). Of special interest is that the workers
in the Swedish factory had a heavy exposure to cadmium oxide
dust which gave rise to severe pulmonary and renal changes but
not to bone changes (Friberg, 1950). Also the British investiga-
tions have not disclosed high incidence  of bone dis-ease, except
the two above mentioned cases, even though disturbances in calcium
and phosphorus metabolism have been common findings (Kazantzis
et al., 1963, Adams, Harrison and Scott, 1969). Different nutri-
tional habits will probably play a role. The intake of fat soluble
vitamins such as Vitamin D and vof calcium is much higher in
Sweden and the United Kingdom than in Japan (see Chapter 8,
table 8:8). In France, the intake of milk is lower than in
Sweden or the United Kingdom. Furthermore, the poor nutritional
conditions during the Second World War must have played an
important role. It should be pointed out that some French patients
and almost all of the Japanese patients have been women and
thus more susceptible to calcium and Vitamin D deficiencies.

6.4.2  In animals
Animal experiments have also indicated that exposure to cadmium can
cause bone changes. Ceres'a> 1945, injected 1 mg CdSO. daily into
rabbits. After two months he observed decreased calcium levels in
serum and a decreased mineral content in bone. Maehara, 1968,
gave groups of male rats, female rats and ovariectomized rats
cadmium in a diet low in calcium (50 ppm Cd for 45 weeks followed
by 25 ppm  for 5 weeks). He found a decalcification and concluded
that this was probably caused by a disturbance of calcium absorp-
tion in the digestive tract. He did not report on levels of
cadmium in the organs or on proteinuria, so it can not be said
to what extent the bone changes were caused by renal dysfunction.

Larsson and Piscator (unpublished data) gave female rats 25
ppm cadmium as the chloride in drinking water. Exposure was
for 1 and 2 months and diets with normal and low contents,
respectively, of calcium were given. For data after 2 months,
see table 4:1.  A significant decrease in the mineral content
of the bones was found in groups exposed to cadmium and fed
a low calcium diet for two months. Cadmium exposure alone and
a low calcium diet alone did not cause such a decrease. Further-
more, cadmium levels in liver and kidneys from animals exposed
to cadmium and on low calcium diet were 50 percent higher than
in animals exposed to cadmium but on a normal intake of calcium,
indicating that a low intake of calcium will increase the absorp-
tion of cadmium.  Studies with injected   Ca showed that there
was the same calcium accretion in the. tibia in animals on low
calcium and in animals on this diet combined with cadmium exposure.
These findings suggested that there was not a direct action
of cadmium on bone tissue but that the osteoporosis in cadmium
exposed rats on a low calcium diet was caused by an increased
bone reabsorption for maintenance of blood calcium.

Zinc has been shown to be important for bone formation. In
calves given cadmium orally (350 ppm in the  diet for 7 days)
the uptake of zinc was increased in most organs but not in
bone, in which there was instead a decrease (Powell, Miller
and Blackmon, 1967). Lease, 1968, found in the chick that cadmium
caused a decrease in the zinc uptake in the tibia.
6.4.3  Discussion and conclusions
A direct action of cadmium upon bone is unlikely, as stated
in the introduction to this section. No data has been brought
forward to support such a possibility, so it will not be further

An effect of cadmium upon zinc metabolism, essential for bone
tissue, can not be ruled out. Available data, however, do not
permit any conclusions as to whether this possible action is
critical for bone effects of cadmium.

The effects on bone with all probability are secondary to effects
on calciurn-phosphorus metabolism. Theoretically, cadmium exposure
could influence metabolism of bone minerals in several ways:
by affecting the absorption of such minerals in the gastrointes-
tinal tract directly or by influence on Vitamin D activity,
by changing the parathyroid activity or by directly affecting
the renal regulation of the Ca/P balance.

None of these possibilities has been ruled out entirely by
available data. It was shown in section 6.1 that tubular kidney
damage and tubular proteinuria are typical features of chronic
cadmium poisoning. Increased excretion of bone minerals is
not an uncommon cause of kidney stones. An impairment of the
renal tubular regulation of Ca/P balance is therefore with
all probability the most important factor for elicitation of
bone changes in workers with proteinuria. The bone changes
reported in the French cadmium workers have features typical
of osteomalacia and it is well known that other forms of tubular
dysfunction, either hereditary forms or acquired forms can
give rise to osteomalacia. Further discussion on the mechanism
for elicitation of the so-called Itai-itai disease can be found
in Chapter 8.

Concerning the other possibilities for influence on the Ca/P
metabolism, the following could be said. The parathyroids
regulate blood calcium levels mainly by influencing bone: re-
sorption and renal excretion of phosphate and will therefore
invariably be involved when disturbances in bone salt meta-

                                                            6-41 .
bolism  occur. However, at present there is no reason to believe
that cadmium influences the parathyroids primarily.

An action on the uptake of calcium from the gastrointestinal
tract is most likely of some importance, especially when cadmium
exposure is by the oral route. The evidence from the animal ex-
periments by Larsson and Piscator (unpublished data) speaks in
favor of such an action.  Kidney levels were below those likely
to give rise to renal impairment.

The importance of dietary calcium supply for the elicitation
of bone changes make precise estimations regarding dose-response
relationships impossible. The evidence by Larsson and Piscator,
however, showsthat even a relatively  short exposure to moderate
concentrations of cadmium can influence bone mineralization
when the calcium content of the diet is low.

6.5.1  Acute effects and dose-response relationships
An influence on liver function has been recorded in several work-
ers with acute cadmium poisoning after exposure to cadmium
oxide fumes (see section 6.1.1). In lethal cases microscopic
changes have been noted in the liver and attributed to the
general toxemia. These changes have been slight .compared to
the changes in the lungs.

Prodan, 1932, exposed cats to high concentrations of cadmium
oxide fumes for short periods of time and found fatty infiltration
in the livers. Similar changes were found in cats exposed to
cadmium oxide dust.

Andreuzzi and Odescalchi, 1958, gave rabbits single intravenous
injections of doses varying from 1.25-3 mg Cd/kg and determined

the GOT-activity in the serum at different times during 72
hours. In the group given 3 mg/kg, the GOT-activity increased
considerably after 17 hours, but 60 percent of the animals
were dead within 24 hours. When 2.5 mg/kg was given, the GOT-
activity increased more than tenfold after 24 hours, but 40
percent of the rabbits died within 48 hours. Rabbits' given
2 and 1.25 mg/kg, respectively, survived more than 72 hours.
After 24 hours the increase in GOT-activity was about fourfold,
but after 72 hours the activity was within the normal range
again. These results indicate that a dose near the LDcn ^s
necessary in order to induce a severe liver lesion and that
the effect on GOT-activity produced by lower doses is reversible,

Kapoor, Agarwala and Kar, 1960, gave rats single subcutaneous
injections of 10 mg Cd/kg as chloride, a dose later shown to
produce morphologic alterations in rat liver (Favino and Nazari,
1967). The subcellular distribution of cadmium was studied
at times varying from 6 to 168 hours after injection. Initially
the cadmium concentration was greatest in the nuclear fraction,
but later, more was found in the supernatant. Nordberg, Lind
and Piscator (to be published) found a considerable decrease
in liver weights within  the first 6 days in mice given a single
subcutaneous injection of 3 mg Cd/kg but no difference in livor
weights compared to controls after 18 days.

That acute exposure will give rise to morphological and func-
tional changes in the liver is clear from the foregoing experi-
mental results. In Chapter 4 it was shown that after acute
exposure, both via the respiratory tract and via injection,
cadmium was accumulated in the liver. It is not known if changes
found at autopsy in livers from human beings exposed to high con-
centrations of cadmium oxide fumes are due to a direct action
of cadmium or to the general changes produced by the oedema

of the lungs. It is conceivable that cadmium will have a  direct
action on certain liver functions especially because  there
is no binding of cadmium to metallothionein during  the first
hours after injection (see section 4.5   ). However, the pos-
sibility that changes in the cardiovascular system  also influ-
ence the function of the liver can not be excluded.

6.5.2  Chronic effects and dose -response relationships  -n
Friberg, 1950, found that the Takata-reaction was positive  in 2
and the thymol test in 3 of 19 workers exposed to cadmium oxide
dust with a mean exposure time of 20 years. Increases in serum
gamma globulin levels were found in several workats.  In most
other investigations liver function has been little studied,
but it will be apparent from the reports of Bonnell,  1955,
Kazantzis et al.,  1963 and Adams, Harrison and Scott,  1969,
that compared to the pronounced changes in renal function,
gross changes in liver function are unusual findings  in cadmium
exposed workers,  in_ani!!!al.s_
Prodan, 1932, found changes in the livers of cats exposed to
cadmium via the respiratory or the oral route. Wilson,  deEds
and Cox, 1941, made similar observations in rats given  cadmium
orally, 250-500 ppm in the diet for several months. Friberg,
1950, injected cadmium sulphate (0.65 mg Cd/kg] into  rabbits
six days a week for 2-4 months and found cirrhotic changes.
Axelsson and Piscator, 1966a,  determined the GOT-activity in
serum from rabbits given injections of cadmium chloride (0.25
mg Cd/kg) 5 days a week for 11-29 weeks. They noted that com-
pared with controls,  there was no difference after 11 weeks of

exposure, whereas there were significant increases in activity
after 17 weeks. At that time the concentration of cadmium was
around 450 ppm wet weight. Piscator and Axelsson, 1970, made
similar determinations in a group of rabbits exposed in the
same way for 24 weeks and thereafter followed for another 30
weeks. At that time the GOT-activity was the same in" serum
from the exposed rabbits and controls. The concentration of
cadmium in .the liver was about 180 ppm.  There was no difference
in alkaline phosphatase activity of serum. These findings sug-
gest that the  liver damage is reversible.

Long-term studies on effects of cadmium on activities of certain
liver enzymes have been performed by Sporn, Oinu and Stoenescu,
1970. In one experiment, rats were given cadmium chloride (1
ppm cadmium) in drinking water for 335 days. An increase in the
activity of phosphorylase a_ and a decrease in the aldolase
activity were found, indicating that cadmium may interfere
with carbohydrate metabolism in the liver. When rats were given
larger amounts of cadmium (10 ppm Cd in food) for shorter periods,
an influence of cadmium on the oxidative phosphorylation in the
liver mitochondria not seen in the above mentioned long-term ex-
periment was noted.

When zinc was administered simultaneously via the oral route
to rats given  10 ppm cadmium in food for 60 days, it was
found that whereas zinc prevented the action of cadmium on the
oxidative phosphorylation in the .mitochondria, it did not pre-
vent changes in the activity of phosphorylase a_ or aldolase
(Sporn et al., 1969).

Cadmium was not determined in organs, so the effect on the en-
zymes cannot be directly related to liver concentrations. How-
ever, Sporn, Dinu and Stoenescu, 1970, estimated that the mean

total intake of cadmium in the rats  receiving  1 ppm  in  drinking
water for 335 days was 4 mg.

In an experiment by Decker et al.,  1958,  it was found that ani-
mals receiving 0.05 ppm cadmium  in  drinking water  for one year
had ingested a total amount of 5.8  mg.  In  these animals  the mean
cadmium concentration in the liver  was  1.1 ppm. It is conceiv-
able that in the above mentioned experiment by Sporn, Dinu and
Stoenescu,  1970, cadmium  levels in  livers were not  much dif-
ferent from the ones reported by Decker et al., 1958. This in-
dicates that cadmium might act upon  certain enzyme activities
at a liver concentration of the same magnitude as  can be found
in normal human adults (see figure  4:14).
As the liver will accumulate large amounts of  cadmium  during
exposure, functional disturbances could be expected. Liver
dysfunction has not been a common finding in exposed workers.
The results by Sporn, Dinu and Stoenescu, 1970,  indicate  that
in rats certain liver enzymes may be influenced  by cadmium
concentrations of the same magnitude as found  in normal human
adults, but it is not known at present to what extent  these
findings can be applied to the human liver.
Little attention had been drawn to effects of cadmium on testicles
prior to the mid-1950's when Parlzek described  the  destructive
effect on testicular tissue  (Parlzek and Zahor,  1956, and Parlzek,
1957). As early as 1919, however, a brief mention was made
of a "bluish discoloration of the testicles" of  experimental
animals in a report on the pharmacology of cadmium  (Alsberg
and Schwartze, 1919, and Schwartze and Alsberg,  1923), but

this information seems to have escaped attention at that time.
During the last 15 years, however, a vast literature has been
published on different aspects of the destructive action of
cadmium on this organ. The following review does not cover all
published articles, but  gives the more important aspects.

6.6.1  Acute effects in  animals
According to Parlzek's description in  1957, a subcutaneous injection
of 0.02 mM of cadmium chloride or lactate per kg (2.24 mg Cd/kg)
caused macroscopic changes in the testicles within the first
few hours after injection. The organs  first became swollen
and dark red or purple. The weight then decreased rapidly
and the testicles became small,' hard and yellowish. At the
same time the weight of the seminal vesicles and the prostate
decreased as a result of a decreased endocrine activity of
the testicles. Histologically a capillary stasis and oedema
of the interstitium were observed 2-4  hours after injection,
followed by extensive hemorrhages according to Parizek and
Zahor, 1956. Regressive changes of the seminiferous epithelium
were seen 4-6 hours after injection and progressed to a total
necrosis within 24-46 hours.

At a certain time Cabout one month in  the rat) after the acute
necrosis, a revasculari zation of testicles (Niemi and Kormano,
1965, and Kormano, 1970) and a regeneration of Leydig cells
occurred (Allanson and Deanesly, 1962). Simultaneously, the
endocrine activity of the testes returned (Parlzek, 1957,
Allanson and Deanesly, 1962). When the dose injected was large
enough, the germinal epithelium did not regenerate and the
testicles thus functioned as endocrine organs only (Kar and
Das, 1960, Allanson and Deanesly, 1962 and Gunn, Gould and
Anderson, 1963a). About one year after injection, interstitial

cell tumors developed (Gunn, Gould and Anderson,  1963a,  and
Roe et al.. 1964; see also Chapter 7).

The sterilizing effect of cadmium is very  rapid because  simulta-
neously with the alterations in the testicles, morphologic changes
in the spermatozoa of the epididymis and ductus deferens  occur.
Animals become permanently sterile as early  as 24  hours  after in-
jection (Kar and Das, 19G2a). Cadmium also  is extremely  toxic for
sperm cells in vitro (White, 1955). This sterilizing  effect  has
been studied in a number of  animal species  both by  systemic  (see
below) and i nt rates ticular (Kar, 19G1, 1952, Setty  and Kar,  1964,
Chatterjee and Kar,  1968, Kar and Kamboj,  19G3, and Kar  and  Das,
1962b) injections.  Sterisit ivit  ofdi
The observations of te"sticular necrosis by Parizek  and  Zahor,
1956, and Parizek, 1957, concerned mice and  rats. Extensive
later studies have confirmed these observations  (Meek,  1959,
Kar and Das, 1960, Gunn, Gould and Anderson,  1961,  1963a
and b, and Allanson and Deanesly, 1962). Similar changes
have been shown to occur after systemic administration  of
cadmium salts to other experimental animals  such as  rabbits
(Parizek, 1960, Cameron and Foster, 1963), monkeys  (Girod,
1964a and b), guinea pigs (Parizek, 1960, Johnson,  1969)
and golden hamsters (Parizek, 1960) as well  as domestic animals,
calves (Pate, Johnson and Miller, 1970). However some animal
species such as frog,  pigeon, rooster, armadilla and opos-
sum (Chiquoine, 1964)  and domestic fowl (Erickson and Pincus,
1964, and Johnson, Gomes and Van Demark, 1970) did  not  develop
testicular necrosis, in spite of such doses  as 10 and 20
mg CdCl7/kg  (corresponding to 6.2 and 12.4 mg Cd/kg)  given
to the species tested by Chiquoine, 1964. On  the basis  of

these findings, Chiquoine,  1964, suggested that cadmium necrosis
is common to species possessing scrotal testes and absent
from those possessing abdominal testes. Opossum was an exception
to that generalization.

Some strains of mice were also insensitive to subcutaneous in-
jections of 0.02-0.04 mM CdCl2/kg  (2.2 -4.4  mg Cd/kg) (Chiquoine
and Suntzeff,  1965). Even doses in the lethal range did not pro-
duce any testicular effects in some strains of mice, according
to experiments performed by Gunn,  Gould and Anderson,  1965.
They concluded that the amount of  cadmium needed to produce
minimal testicular damage varied within the susceptible strains.
It is of interest in this connection that Lucis and Lucis, 1969,
have shown that strains of  mice susceptible to cadmium induced
testicular necrosis exhibit a greater uptake of cadmium in the
testes than strains which are resistant 'to this action. The
lowest subcutaneous dose that has  been reported constantly
to give rise to testicular  necrosis in mice is probably 0.012
mMol/kg (1.34 mg Cd/kg), stated by Gunn, Gould and Anderson,
1968,to be effective for the CD-I  strain.

Gunn, Gould  and Anderson,  1965, also tested different  doses  in
different strains of rats.  They concluded that the  dose of cadmium
needed to produce minimal  testicular damage differed among various
strains and  even within the same strains of rats  derived  from
different commercial sources.   Usually 0.02- 0.05 mM CdCl^/kg
(2.2-5.6 mg  Cd/kg) has been used in rats (Parlzek,  1957,  Kar and
Das,  1960, and Gunn, Gould  and  Anderson, 1961, 1963a and  b).
In calves intravenous  administration of doses as  low as 0.20 mg
CdCl2 has been reported to  give rise to testicular  necrosis
(Pate, Johnson and Miller  1970).

All the studies mentioned are concerned with acute effects and
sequelae of a single injection of cadmium. Subcutaneous, intra-
peritoneal and intravenous inje.ctions of cadmium salts are
effective with regard to tssticular necrosis in various animal
species. Boissou and Fabre, 1965, tested several routes of
administration in rats.  Large doses  (0.25-0.57 mMol/kg, i.e.,
26 and 64 mg Cd/kg) administered by the oral route were also
reported to give rise to testicular changes similar to those
produced by the injection routes. In some large animals, such
as calves (Pate, Johnson and Miller, 1970), only the intra-
venous injection was effective. Kar and Kamboj, 1963, reported
that "scrotal inunction" (i.e. painting of CdC^ solution
on the scrotal skin) gave rise to testicular atrophy and sterility
in several animal species.  Mechanisms for testicular necrosis
The mechanism for development of acute necrosis of the testicles
after cadmium injection has been discussed in a number of papers.
Parfzek, 1957 and 1960, advanced two possibilities for the pri-
mary action of cadmium: Deirculatory failure and 2)action on
spermiogenic epithelium. Parfzek, 1957, considered the latter
possibility more probable. As zinc is essential for the main-
tenance of germinal epithelium (Elcoate et al., 1955), Parlzek
considered his own observation (Parizek, 1956) of an antagonistic
action of zinc against the necrotizing effect of cadmium sup-
portive of this last mentioned theory.  Later Dimow and Knorre,
1967, found changes in the enzymes of the germinal epithelium
before histological changes were evident in the testicles.
They considered their results to be in favor of a direct
action of cadmium on germinal epithelium. Hodgen, Gomes and

Van De Mark,  1970,  have  detected  an  isoenzyme  of carbonic
anhydrase  in  rat  testis  not  found in  rat  kidneys or erythrocy tes .
They suggested  that  this  organ  specific carbonic jnhydrase
was the primary site  of  action  of cadmium in the testicle.
Hodgen and his  colleagues  (Hodgen, Butler and  Gomes,  1969,
and Hodgen, Gomes  and Van  De  Mark, 1970)  also  showed  -that
the activity  of this  isoenzyme  decreased  already 30 minutes
after cadmium injection  and  later ceased  entirely. Hodgen,
Gomes and  Van De  Mark,  1969,  showed  that  the testicular  isoenzyme
was found  in  both  rat testicular  artery and  testicular parenchyma.
Thus these studies  did not reveal whether the  action  of  cadmium
took place in the  interstitium  or in  the  tubules of the  testicle.

Whatever may be the molecular basis for the cadmium action, it
has been well established  that  the vascular bed and the blood
flow of the testicles  are  affected very early  after injection
of cadmium. This has  been  shown with  histological (Kar and
Das, 1960 and Gunn, Gould  and Anderson, 1963b), electron micro-
scopical (Chiquoine,  1964  and Clcgg and Carr,  1967),  angiographic
(Niemi and Kormano,  1965), and  functional  (Waites and Setchell,
1966,  Clegg and Carr,  1967, Carr  and  Niemi, 1966, Johnson, 1969
and Setchell and Waites,  1970)  techniques. Because the injected
cadmium is concentrated  in the  interstitial tissue (Berlin and
Ullberg, 1963, and Nordberg, unpublished data), and never reaches
the germinal epithelium  in any  detectable  amounts, the changes
observed in this epithelium most  probably  are  secondary to the
vascular damage.
The necrotizing action of cadmium can be prevented by specific
treatments. The effectiveness of the administration of zinc in
this respect has already been mentioned. Totally 80-200 times
the molar equivalent of zinc acetate given in three injections:
5 hours before, simultaneously with and. 19 hours after the cad-

mium afforded complete protection of the testicles of the rat
against 0.04 mMol of Cd/kg (Parlzek, 1956, 1957 and 1960).
These observations have been confirmed by other investigators
(Gunn, Gould and Anderson, 1961) who used a total of 3 mMol/kg
of zinc to prevent testicular damage from 0.03 mMol Cd/kg in
Wistar rats. It was also shown that the duration of the pre-
vention made possible by zinc was dependent upon the breeding
of the animals. Animals bred immediately after injection of
Cd + Zn showed a sharp decrease in fertility 4 weeks later, whereas
animals bred 8 weeks after injection were still fertile 12 weeks
after injection.

Selenium (0.04 mMol/kg) also protects the rat testicles against
the necrotizing action of cadmium (0.02 mMol/kg) as shown by Kar
and Das,  1963. The same effect of selenium was studied in the
mouse by Gunn, Gould and Anderson, 1968b. The last mentioned
authors also showed irr an earlier communication (Gunn, Gould
and Anderson, 1966) that thiols such as cysteine and dimercap-
topropanol (BAD prevented cadmium induced necrosis in the
testicles. Cobaltous chloride given to rats in a dose of 30
mg CoCl2/kg 17 hours prior to administration of 6.60 mg cad-
mium chloride/kg also protected the testicles from damage
(Gabbiani, Baic and D6ziel, 1967).

Ito and Sawauchi, 1966, reported that injection of 1/2 to
1/4 of a testis destructive dose of cadmium chloride (0.1
ml of a 0.1% CdCl- solution per mouse) 2 days prior to the
injection of the normally testes destructive dose prevented
testicle destruction in more than half of the animals.
This protective effect of pretreatment  with the harmful
agent itself has later been confirmed in our own laboratory
(Nordberg, unpublished observation).

6.6.2  Chronic effects  In animals
From the point of view of environmental exposure, acute effects
of large doses are of limited interest. Histological changes
in the testicles of rats as a result of long-term administra-
tion of cadmium in the food were reported by Pindborg, 1950
and Ribelin, 1963. Pindborg gave doses of 0.025-0.1 percent
CdCl2 (= 150-610 ppm Cd) and Ribelin. 50-1270 ppm cadmium in
the diet. The changes reported by Ribelin were different from
those developing after a single injection but were not differ-
ent from those produced by several other toxic substances test-
ed by Ribelin.  On the whole it is difficult to judge the fre-
quency of the changes from the paper published by Ribelin as
no data are given concerning number of animals, frequency of
testicular alterations or the appearance of toxic reactions
in other organs. In a brie,f report by Richardson and Fox, 1970,
testiclar development was studied in Japanese quail which had
received 75 ppm Cd in the diet up to 4 weeks of age. Seminifer-
ous tubules lined with undifferentiated cells were said to have
occurred in more than half of the tubules. Though it is impossible
to judge the nature of the testicular damage from the short com-
munication, it seems that no total testicular necrosis occurred.

Piscator and Axelsson, 1970, reported on histological and electron
microscopic examinations of testicles from rabbits exposed by
repeated daily subcutaneous injections of cadmium for as long as
24 weeks and followed for another 30 weeks before killed. The
investigators did not observe any pathological changes in the
testicles, in spite of the presence of kidney damage. They
stated that the absence of testicular changes could be ex-
plained either by rabbits' comparative insensitivity to the
necrotizing action of cadmium or by the protection of the

 testicles  by  metallothionein formed in the liver.  In order to
 shed  some  light  on  this  question,  Nordberg (unpublished data)
 performed  studies  on  mice  of the  CBA strain which  is very sen-
 sitive  to  cadmium  induced  testicular necrosis.  By  repeated in-
 jections considerable amounts  of  cadmium were accumulated in
 the organs  including  the testicles but no histologically evident
 changes were  found  in this  organ.  These data evidently were in
 favor of the  second alternative suggesting a protective effect
 of metallothionein  against  the  necrotizing action  on the testi-
 cles. Such  a  metal  binding  protein was also found  in the livers
 of the  CBA  mouse  (Nordberg,  Piscator and Lind,  to  be published).
 Injection  of  cadmium  bound  to  metallothionsin did  not produce
 any testicular necrosis  in  doses  effective in this respect when
 injected alone (Nordberg,  unpublished data).  The earlier men-
 tioned  observations by  Ito  and  Sawauchi,  1966,  of  a protective
 action  of  small  doses of cadmium  are consistent with the finding
 that  no testicular  necrosis  has occurred in animals exposed re-
 peatedly to cadmium.

Another observation which might be relevant when discussing
long-term effects on  the testicles is  the  decrease  in protein-
uria  demonstrated in mice repeatedly injected w'ith  CdC^ for
several  months (Nordberg and Piscator,  unpublished  data).  Male
mice  normally  excrete  a high concentration  of protein in the
urine. The  major urinary protein is synthesized  in  the  liver
under the  influence of testosterone  (Finlayson and  Asofsky,  1965,
Roy and Neuhausi  1966 and Roy, Neuhaus  and  Harmison,  1966). The
observed decrease in proteinuria during cadmium  exposure might
therefore  be a result  of an action of  cadmium on the  production
of testosterone in  the interstitial cells  of  the testicles. The
observation that  cadmium accumulates in the interstitial tissue
(around the capillaries) of the testicle  (Nordberg,  unpublished
data)  favors such a possibility.

                                                              6-54.  I_n_
The reports of acute testicular necrosis after systemic admin-
istration of cadmium salts in a great number of animal species
strongly suggests that a similar effect is likely in human beings.
However, such testicular necrosis has not been reported to be a result
of cadmium exposure. Smith, Smith and McCall, 1960, found high
values of cadmium in the testicles of men industrially exposed
to cadmium fume. These authors also  reported some histological
changes in the testicles at post mortem examination. The changes
were of a rather unspecific nature,  however, and the authors
therefore ascribed them to the terminal illness. It is difficult,
however, to exclude the possibility  that these histological changes
had some association with  the cadmium exposure. Favino et al.,
1968, investigated the fertility of  10 cadmium workers and also
analyzed androgens in blood. In this investigation one case of
"impotency" with abnormally low testosterone levels vin the blood
was found. Further studies 'similar to those made by Favino et
al. are necessary before any conclusion can be drawn concerning
the possible effect of cadmium on the endocrine function of the
testicles of people exposed to cadmium.
The lowest dose effective for elicitation of acute testicular
changes in calves is 0.2. mg CdCl2/kg(0 . 12 mg Cd/kg) given by
the intravenous route  (Pate, 3ohnson and Miller 1970). A sub-
cutaneous injection of cadmium salts in a dose of 0.01 mMol/kg
(1.1 mg/kg) can produce a total testicular necrosis in some ani-
mals (e.g. certain strains of mice).  For other animals (e.g.
rabbits) higher doses are required. Some animal species or cer-
tain strains of a species are so  resistant to the acute necro-
tizing action of cadmium, that even doses in the lethal range
do not cause alterations. The dose-interval between no-effect and

total testicular necrosis is very narrow for a given kind of
animal. Testicular necrosis can be prevented by zinc, selenium,
cobalt, thiol compounds or pretreatment with a smaller dose of

All data on testicular necrosis are from animal experiments.
As many mammalian animal species including monkeys are sus-
ceptible to the action of cadmium on the testicles, it is
highly probable that a similar effect would occur also in human
beings. However, as cadmium is not used as a drug, people can
not be exposed by injections.  If the absorbed dose necessary
for elicitation of testicular changes is proportionally the
same as the lowest subcutaneous dose in animals (1 mg Cd/kg),
this means that 70 mg should be absorbed in a short time in a
70 kg man, an unrealistic exposure.

For chronic exposure no conclusive data are available concerning
effects on the testicles. Animal experiments suggest that there
might be a possibility for effects of a somewhat different
nature from those seen after a single injection. As yet, no
evidence on human exposure has proven an effect on the testi-
cles.   Accordingly no dose-response relationships for chronic
exposure can be discussed.

6.7.1  In human beings
During the years many different symptoms have been reported in
men exposed to cadmium. These  include loss of appetite, loss
of weight, fatigue, increases  in the E.S.R. etc. These unspeci-
fic symptoms can be related to the systemic effects.  More spe-
cific effects have been a yellow coloring on the proximal part
of the front teath (Barthelemy and Moline, 1946, and Friberg,

1950) and anosmia (Friberg, 1950),  The last mentioned effect
was found in about one-third of a group of workers with a mean
exposure of 20 years to cadmium oxide dust. That anosmia is
common in workers exposed  for long periods of time to cadmium
oxide dust was also noted  by Baader, 1951. Suzuki, Suzuki and
Ashizawa, 1965, and Tsuchiya, 1967, did not find an increased
prevalence of anosmia in workers exposed to cadmium stearate
and cadmium oxide fumes, respectively.

Pancreatic function has attracted very little interest, which
is regrettable as the high concentrations of cadmium in the
pancreas found at autopsy  of cadmium workers(section 4.3.2)
have indicated the possibility of a disturbed function. Ac-
cording  to Murata et al.,  1970, a decrease in pancreatic
function is a feature of the Itai-itai disease.

Gastrointestinal effects have been a common findings in earlier
reports:on acute cadmium poisoning due to ingestion of food high-
ly contaminated with cadmium. The contamination was usually caused
by storage of food in cadmium plated containers, cans, etc. Nausea,
vomiting, abdominal pains  and diarrhea have been reported symptoms
(Lufkin  and Hodges, 1944,  Gole and Bauer, 1944,.Report from United
States Public Health Service, 1942). Even if the outbreaks of
food poisoning due to cadmium have decreased considerably since
cadmium  has been prohibited in utensils for cooking and storing
food,after the Second World War, some reports during the later
years indicate that tfris problem might still exist:(Reine and
Peres, 1959, and Baker  and Ha^ner, 1961). The prognosis seems
good but there have been no reports on detailed follow-ups.

Symptoms from the nervous  system have been reported by Vorobjeva,
1957, who investigated  160 workers in an accumulator factory.
Subjective symptoms consisted of headache, vertigo, sleep distur,-
ances etc. Physical examination revealed increases in knee-joint

reflexes, tremor, dermographia and sweating. Special investiga-
tions on sensory, dermal, optic and motoric chronaxia showed
that the cadmium exposed workers with subjective disturbances
also had changes on these tests.

Cvetkova, 1970, studied 106 women (ages: 18-48) employed in
cadmium industries. Sixty-one worked in an alkaline accumulator
factory, 21 in a zinc smelter and 24 in a chemical factory. A
control group consisted of 20 women. Levels of cadmium in air
varied between 0.1-25, 0.02-25 and 0.16-35 mg/m , respective-
ly. Exposure times were not given in the report. In the alka-
line  accumulator factory and the zinc smelter groups, the
weights of newborn children, 27 in each group, both boys and
girls, were significantly lower than the weights of children
born to  members of the control group. In 4 of the 27 children
born to women in the zinc smelter group, signs of rachitis
and delayed development of teeth were recorded. The author
concluded that pregnant women should not work in a cadmium
contaminated environment.

Large doses of cadmium are toxic to nervous ganglia, as has
been shown by Gabbiani, 1966, who gave rats subcutaneous in-
jections of cadmium chloride (2.5-28 mg Cd/kg) and found severe
hemorrhagic ganglionic lesions. Gabbiani, Baic and D6ziel,  1966,
found that by giving rats as pretreatment 5 subcutaneous injec-
tions of cadmium chloride in a relatively small dose, (2mg/kg),
the ganglionic lesions produced by a single intravenous dose of
8 mg/kg were prevented. Damage to the cerebrum and cerebellum was
found in newborn rats and rabbits receiving cadmium (Gabbiani,
Baic and Deziel, 1967), whereas in mature animals, such changes
were not found.  Gabbiani, Gregory and Baic, 1967, found that pre-
treatment with zinc acetate prevented the development of ganglion-
ic damage.

There have not been any long-term experiments in which small
doses of cadmium were administered in order to investigate
nervous functions.
Cvetkova, 1970, exposed female rats via the respiratory route
to cadmium sulphate  (about  3 mg/m ) during pregnancy. On the
22nd day, half of the group was killed and the embryos were taken
out. There was the same number of embryos in exposed rats as in
a control group, but the mean weight was lower in the exposed
group.  Analysis of  liver from embryos showed a higher content
of cadmium in the exposed group. In the exposed group in which
pregnancies were  allowed to be full-term, the weight of the
newborns was lower than in  controls. After 8  month  ,  the
weights in the exposed group were still lower. The rats born
to the exposed group also had an increased mortality during
the first 10 days after'birth.
 ith regard to influence on endocrine glands it has been shown
that a single subcutaneous  injection of cadmium chloride (10
mg/ Cd/kg) given to  male rats causes a prompt decline in
pituitary FSH level  and an  increase in LH (Kar, Dasgupta and
Das, 1960). These changes were thought to be-caused by the
testicular damage and it is not known if cadmium exerts a
direct effect upon the pituitary. In this connection, it is of
interest that Berlin and Ullberg, 1963,noted an uptake in the
pituitary gland after a single dose of radioactive cadmium.
Influence on the thyroid has been demonstrated by Anbar and
Inbar, 1964, who gave  mice (weight not given] 0.12 mg Cd by the
intraperitoneal route. They found a decrease in the  uptake of
iodine, but as the dose was large and other mstals, both
essential and non-essential had the same effects, no certain
conclusions can be drawn from the experiment. A decrease in the
uptake of iodine was also found by Balkrishna, 1952, who gave
rats single intramuscular injections of cadmium chloride (10 mg

Baum and Northern, 1967, found amyloid deposits in the
glomeruli of rabbits given intramuscular injections of
cadmium chloride, 1 mg Cd/kg, a total of 68 injections
in 22 weeks,  or the same dose for 9 weeks, a total .of
47 injections.  Similar findings have also been described
by Vigliani, 1969, in rabbits exposed for 7-13 months to
cadmium (0.25 mg Cd/kg  subcutaneously,5  days a week).
He attributed the amyloid deposits to disturbances in
immunglobulin metabolism.
Acute manifestations in animals have been studied mainly
by injection of cadmium. It has been possible to show
effects from most organ systems, including hypertension,
testicular, liver and renal damage. Doses have varied be-
tween 1-20 mg cadmium/kg. The results show that cadmium
is an extremely toxic metal but they have only limited
bearings on the effects produced by long-term exposure to
cadmi urn.

In human beings acute poisonings with local symptoms from
the  gastrointestinal tract are known to have occurred due
to ingestion of cadmium contaminated food or beverages.
Systemic effects, however, are not known.

Long-term exposure gives rise to renal tubular damage in
animals. Workers with prolonged exposure to cadmium oxide
dust or cadmium oxide fumes will develop renal tubular dys-
function. A characteristic sign of the renal dysfunction is
proteinuria of the so-called tubular type. This is considered
to be due to a decreased tubular reabsorption of filtered

proteins. Cadmium seems to be transported to the kidney with
a low molecular weight protein, metallothionein. The reab-
sorption of this protein will also decrease and the result
will be an increased excretion of cadmium. Other signs of
the renal tubular dysfunction, usually appearing after the
proteinuria, are glucosuria and amino-aciduria and"changes
in the metabolism of calcium and phosphorus.

Evidence from animal experiments and from analyses of cadmium
in kidneys from workers exposed to cadmium indicates that
renal dysfunction may become manifest at levels around 200
ppm wet weight in renal cortex.  A daily peroral intake of
about 100-150 ug cadmium may result in a reaching  of this
level after 50 years of exposure with an absorption of 5 per-
cent.  Based on an absorption of 25 percent of inhaled cad-
mium, concentrations of cadmium in ambient air of  about 1-1.5
/ug/m  will Sxve the same results. In a factory, the necessary
concentration during 25 years of exposure would be about 8
ug/m . In these estimations, simultaneous exposure via food
has not been taken into account.  In table 6:2, the exposures
required to reach the critical level in the kidney are given to-
gether with other assumptions concerning absorption.

Osteomalacia has been observed in workers industrially exposed
to cadmium. It is considered to be mainly due to a disturbance
in calcium and phosphorus  metabolism caused by the renal tu-
bular dysfunction*
There is evidence that  hypertension  can be  induced  in animals
either by single injections  or by  repeated  exposure to cadmium
in drinking water.  In human  beings who have died  after a history
of hypertensive disease,  cadmium  levels in  kidneys  have been
higher than in people who have died  from  other  diseases. The

                                                             6-61 .
cause of the association found is not clear. Epidemiological
investigations have indicated a relationship between cadmium
levels in air and cardiovascular disease. There is reason to
believe that this association is spurious and in any case, no
causal association has been proven.

Other long-term effects that have been noted are anemia and
liver dysfunction, as shown in both animal experiments and
investigations on exposed workers. Animal data have indicated
that the activities of enzymes engaged in carbohydrate metabolism
might be changed at concentrations of cadmium in liver within
the range found in livers of normal human beings. The signifi-
cance of this finding for man is not known.

Testicular changes have been noted during long-term exposure.
These changes are milder than the pronounced testicular damage
caused by acute dos'es of cadmium. It is not known if the
testicles will be affected in man during long-term exposure.


Worker Morpho-


Cadmium Age
in cor-
tex n


Years of
or biopsy(B)



W.H. ** «•
N. $J) *
B. ** *
J. **
J. (*) *

K. (*)
L. - (*)
Y. - -
H. *
P. - *
N. +
N. -







Baader, 1
ed data.

al., 1963.
, 1952 and 1957.
and 1957.
and 1957.

Horstebrock, 1951
unpublished data.

Piscator, unpubl




J) Underlined figures are based on cadmium concentrations in whole kidney,  assuming that the cadmium
concentration in cortex is 1.5 times the average kidney concentration (section
$J) Results from histological examinations not reported but at examination  in 1946 (Friberg, 1950)  this
worker had the lowest kidney function tests of all (Inuline clearance:  42ml/min;  Concentration capacity:
1.016; NPN: 44 mg %.


           OR INGESTION  (total daily intake) NECESSARY FOR REACHING

           200 ppm (wet  weight) OF CADMIUM IN RENAL CORTEX '(total
           body burden:  120 mg cadmium) AFTER DIFFERENT EXPOSURE
Years of
 Ingest ion
 total daily
 intake,  jg Cd
          absorption percent

           2.5    5     10
1324   662   331
 530   265   132

 265   132    66
 Ambient  air

  /jg Cd/m
                  absorption percent

                   10     25     40
16.2   6.5    4.1

 6.5   2.6    1.6

 3.2   1.3    0.8
 Industrial air

   /jg Cd/m
                   absorption  percent

                    10     25      40
52.5  21      13.1
21.0   0.4    5.2
10.5   4.2    2.6
x)                         3
  A lung ventilation o^ 20 m  per day has been used for evaluation
of ambient air exposure. A lung ventilation of 10 m^ per 0 hours
225 days per year has been used for evaluation of industrial air
exposure. In no case have the cumulative effects of different
types of exposure been taken into account. The results have not
been corrected for excretion, as it has been considered insig-


           OR INGESTION (total daily intake) NECESSARY FOR REACHING

           50 ppm (wet weight) OF CADMIUM IN RENAL CORTEX (total

           body burden: 30 mg) AFTER DIFFERENT EXPOSURE TIMES AND


Years of
total daily
intake, jag Cd
absorption percent
2.5 5 10
331 166 83
132 66 33
66 33 17
Ambient air
^g Cd/m
absorption percent
10 25 40
4.0 1.6 1.0
1.6 0.7 0.4
0.6 0.3 0.2
Industrial air
^jg Cd/m
. x
absorption percent
10 25 40
1 i
13.0 5.1 3.3
5.1 2.1 1.3
2.6 1.1 0.7
x)                          3
  A lung ventilation of 20 m  per day has been used for evaluation
  of ambient air exposure. A lung ventilation of 10 m  per 8 hours
  225 days per ye«r has been used for evaluation of industrial air
  exposure.  In no case have the cumulative effects of different
  types of exposure been taken into account.  The results have not
  been corrected for excretion, as it has been considered insig-

Mg  protein / 26 hrs
    1500 -
    1000 -
            •   Means

           •	•  Range
15     20      25      30     35
          Exposure  time  in  years
 The values were obtained about 10 years after the  last exposure,
 F i g u re 6:1
Relation Between bxposure limn and Protein Excretion
for 40 Cadmium Workers Divided into 5-Year Exposure
Groups  (from t'iscator, 19GGc).

                          Alb.  cAl
Figure 6:2
Scanned Lleetrophorstic  Patterns for Urinary Proteins
A and B). Cadmium  Workers   C)„  Normal man  D). Person
with Chronic  Nephritis  (from Piscator, 19l56c).

                           CHAPTER 7

Information in regard to a possible carcinogenic effect of
cadmium and cadmium compounds is given primarily from animal
experiments. Only a very few reports dealing with such effects
in human beings have appeared.

7.1.1  In animals
In 1961 Haddow, Dukes and Mitchley reported that repeated sub-
cutaneous injections of rat ferritin produced sarcoma at the
site of injection in rats. Testicular atrophy and benign Ley-
dig cell tumors were also seen. The ferritin contained consid-
erable amounts of cadmium because it. had been, prepared from
rat-liver protein by precipitation with a cadmium salt. The
findings prompted further studies using cadmium alone and dif-
ferent investigators showed that cadmium and cadmium compounds
injected subcutaneously or intramuscularly in rats could induce
sarcoma. In 1964 Haddow et al. induced sarcoma at the site of
subcutaneous injection with cadmium sulphate in 14 out of 20
rats but observed no tumors in mice after similar injections.
In the same study.  Roe et al., 1964,  found testicular atrophy
and Leydig cell hyperplasia and neoplasia. Gunn, Gould and
Anderson, 1963a and 1964, induced interstitial cell tumors in
the testes of rats as well as subcutaneous sarcoma with a single

subcutaneous injection of cadmium chloride. Both forms of cad-
mium-induced tumors were inhibited by subcutaneous administration"
of zinc acetate. Later, the same authors (Gunn, Gould and Anderson,
1967) showed that a single subcutaneous or intramuscular injec-
tion of cadmium chloride in concentrations as low as 0.17 to 0.34
mg of cadmium induced sarcoma. No tumors arose in skin, liver,
salivary glands, prostate or kidney. The authors concluded that
cadmium may be one of the most potent metallic carcinogens yet

Kazantzis, 1963, and Kazantzis and Hanbury, 1966, showed that
sarcomata could also occur after injection of a single dose of
cadmium sulphide. Metastatic tumors were seen in regional lymph
nodes and lungs. Heath et al., 1962, showed that cadmium given
as a metal powder intramuscularly to rats induced sarcomata.
Such tumors could be maintained by transplantation. At the time
of publication, the cadmium tumors had been maintained for 6 years
and 75 transplants (Heath and Webb, 1967). Most of the inducing
metal was incorporated intracellularly by the primary tumors and
bound by the nuclear fraction. Smaller amounts were found in the
mitochondrial and soluble fractions.

Schroeder and collaborators (Schroeder, Balassa and Vinton, 1964
and 1965, and Kanisawa and Schroeder, 1969) reported on life-term
studies on the effect of trace elements on tumors in rats and
mice. The rats given cadmium had more tumors than their controls
while the opposite vas true for mice. Schroeder concluded that
the oral ingestion of cadmium can not be considered carcinogenic
in the doses given.

7.1.2  In human beings
Potts in 1965 reported on the prevalence of cancer among workers
exposed to cadmium oxide dust in the production of alkaline bat-

teries. Among 74 men with at least 10 years' exposure to cadmium,
8 had died, 3 of them from cancer of the prostate and 2 from other
forms of cancer. That the workers had been exposed to toxic amounts
of cadmium was obvious from the high prevalence of proteinuria and
anosmia. Potts did not examine any control group and did not draw
any firm conclusions. He recommended as a matter of urgency, however,
that the possibility of some association between cancer in man
and cadmium as used in industry must be fully explored.

Kipling and Waterhouse,  1967, briefly mentioned the incidence of
cancer in a group of 248 workers exposed for a minimum of one year
to cadmium oxide. The type of work was not stated. From annual in-
cidence rates supplied by the Birmingham regional cancer registry,
it was possible to compute expected values and to compare with ob-
served values. For cancer of the prostate, 4 cases were observed
versus an expected number of 0.58.

Out of the 58 male workers in an alkaline battery plant examined
by Friberg, 1950, (see sections 4.3.1 and 15 had died
in 1970 (Friberg, unpublished data). The cause of death in three
cases was cancer (urinary bladder, primary pulmonary and large
bowel, respectively). No control groups have been studied and no
conclusions have been drawn as yet.

Humperdinck,  1968, reported on a follow-up of 8 cases of chronic
cadmium poisoning described by Baader in 1951. Four deaths had
occurred, one due to primary cancer of the lung. Out of all work-
ers (536) who during 1949 to 1966 had had any contact with cad-
mium, 5 had contracted carcinoma (including the above mentioned
case of lung cancer). The author concluded that the data did not
support any causal relationship between cadmium exposure and can-
cer. It should be added,  though, that the majority of the workers

were relatively young with relatively short periods of contact
with cadmium   (269 for less than one year, only 4 for 7-11 years);
The study, thus, does not elucidate the question of a possible as-
sociation between cadmium exposure and cancer. It should be of
value to study the group on a longitudinal basis, particularly if
more detailed  information on exposure levels can be made available.

Holden, 1969,  very briefly reported one case of carcinoma of
the prostate and one of the bronchus among 42 men exposed to
cadmium fumes  from 2 to 40 years.

Winkelstein and Kantor, 1969', reporting data from the Erie
County and the Nashville Air Pollution Studies, found an asso-
ciation between prostatic cancer and concentrations of suspended
particulate air pollutants in both studies. The authors were
cautious in view of the small numbers but drew attention to
earlier reports of an association between cadmium exposure and
cancer of the  prostate.

Morgan, 1969,  studied the renal and hepatic cadmium levels for
different disease groups at autopsies. In cancer patients she
found such a wide variation in concentrations- of cadmium that
a further study was warranted. In two later investigations she
pursued similar studies of bronchogenic carcinoma and emphysema.
Cadmium was analyzed by atomic absorption spectroscopy with good
recovery and repeatability. In the first of these two further
investigations (Morgan, 1970) she compared the cadmium concen-
trations in a  group of male patients who had died from bron-
chogenic carcinoma with a control group and with a group who
had died from  other forms of neoplasia. The results are shown
in table 7:1.  The average cadmium concentrations in the group
who had died of bronchogenic carcinoma were statistically high-
er than those  in the other groups.

In the second of the later investigations Morgan (unpublished
data) reexamined her material and compared the controls with
3 groups: one group of patients with bronchogenic carcinoma
with emphysema, one group with bronchogenic carcinoma with-
out emphysema, and one group with only emphysema. The. purpose
was to examine whether both emphysema and bronchogenic car-
cinoma were associated with high cadmium levels. She found
that "renal cadmium content was elevated in both groups with
cancer.  Hepatic cadmium was increased in both emphysema alone
and in combination with lung cancer as well as lung cancer
alone."  In 36 controls, the average value for the liver (/ug/g
ash) was 170 (S.D.: 95) against 290 (S.D.: 155) in the group
with only emphysema. Corresponding values for the kidney were
2512 (S.D.: 1427) and 2921 (S.D.: 1252).

Morgan interpreted her findings with great caution. She pointed
for example to earlier observations (Olson et al., 1954, and
Teitz,  Hirsch and Neyman, 1957), in which tissue trace metal
concentrations were found to be abnormal in a wide variety of
neoplastic diseases. Furthermore, she added that there is no
convincing evidence that bronchogenic carcinoma has been asso-
ciated with industrial exposure to cadmium. Concerning emphy-
sema she was also cautious. In addition, Morgan discussed to
some extent the possibility of an increased exposure due to
smoking. This question is dealt with in detail in section 3.2
of our report. Finally, Morgan meant that her findings, for
cancer at least, may have been coincidental rather than etio-
logic,  but she had the opinion that additional studies are
clearly  needed.

There seem to have been no studies made concerning any possible
association between cadmium exposure and cancer of the gastro-
intestinal tract. The  incidence of stomach cancer in Japan is

extremely high, however. According to  the data on cancer inci-
dence in five  continents (Doll, Muir and Waterhouse,  1970), the
age standardized  incidence  rates  (5 year groups in the age range
from 35 to 64  years old standardized against a world  standard
population) for males  in two prefectures in Japan are 156 and
164, respectively, per 100,000. These  are by far the  highest
incidence rates found  in all of the countries studied. Next in
order comes Cape  Prov,  South Africa (Colored population), with an
incidence rate of 102  per  100,000. Other countries have a much
lower incidence rate of stomach cancer, as a rule between 20
and 40 per 100,000. Available  data from the contintental U.S.A.
show values between 11  and  33, while the Japanese and Hawaiian
populations of Hawaii  have  incidence rates of 62 and  80, respec-
tively. The incidence  rate  in  Sweden is 28 per 100,000. The in-
cidence rate for  women is  generally lower, but in Japan the rate
remains high (80  per 100,000 as compared to a usual 20 per
100,000 in other  countrites).

The high incidence of  stomach  cancer in Japan, of course, is no
proof whatsoever  that  cadmium  has some causal connection with
stomach cancer. The obvious exposure to cadmium  via  food  in  Japan
( and should, however, motivate further stud-
ies .

Little information is  available concerning possible genetic effects
of cadmium and cadmium compounds. Preliminary genetic experiments
with CdCl_ on Drosophila melanogaster were performed by Ramel and
K. Friberg (personal communication). Larvae were treated with
62 mg/1 substrate, which was the maximum dose in toxicity test
giving a delay of larval development without causing an excessive
lethality. As an  indication of chromosome breakage, the frequency
of sex chromosome loss was used. One experiment was also performed

on the combined affect of CdCl- and 3000 r X-irradiation on sex-
linked recessive lethals. The treatment with cadmium compound was
given as mentioned above. The results of these two experiments
(table 7:2 and 7:3) do not indicate any significant effect of
CdClp on chromosome breakage, induction of recessive lethals or
on chromosome repair mechanism. It must be stressed, however,
that the material is small and further investigations are needed.

The studies on animals show without doubt that cadmium and
cadmium compounds can give rise to malignant tumors in rats.
The carcinogenic evidence of cadmium in human beings is by no
means conclusive as yet but fully motivates furthei\and inten-
sified studies in groups exposed industrially as well as through
food and ambient air. Very few genetic studies have been performed.
In one study on Orosophila, no significant genetic effects could
be.seen. In view of other known effects of cadmium and its accu-
mulation in the human body, there is a great need for further


               (yug/g ash) IN PATIENTS (average age: 60) DYING


               AND IN CONTROLS (from Morgan. 1970).
Cancer of the lung
                        Number     Liver
                        exam-    Mean    S.D,
Other forms of cancer   50
                          Mean   S.D.
3513   1587

2937   2065

2406   1299

           TREATMENT WITH 62 mg CdCl2 / 1 IN THE SUBSTRATE
           (Ramel and K. Friberg, unpublished data).

Egg laying
period in
days after
- 2
- 4
- 6
- 8
- 10
- 12
Per cent Total
sex chromo- number
some loss counted
Per cent
sex chromo-
some loss
  0 - 12

Table 7:3
THE EFFECT OF CdCl2 (larval treatment with
62 mg CdCl2 / 1 in the substrate) ON RECESSIVE
X-RAYS TO MALES.  (Ramel and K. Friberg,  unpublished

Egg laying
period in
days after
0 - 2
2 - 4
6 - 8
Number of
Per cent
Number of Per cent
X-Chromo- recessive
somes lethals

                           CHAPTER 8

                     THE ITAI-ITAI DISEASE

In 1946, Doctor Hagino, a general practitioner returning from
the war. re-opened a private clinic, in operation in Fuchi-machi,
Toyama Prefecture, since his grandfather's time. Dr. Hagino was
visited by patients with a painful disease, which he called the
"Itai-itai byo", (meaning ouch-ouch disease). The disease had
occurred endemically in the area for several years and is proba-
bly identical with a "rheumatic disease" described by Nagasawa
et al., 1947, among inhabitants of Miya-gawa-mura in the Toyama
Prefecture. It was noted that the disease had a relationship
with the water of the Jintsu River and that a certain Kami oka
mine upstream often caused damage to crops. Drs. Hagino, Koba-
yashi and Yoshioka. examining river water, rice and fish, could
demonstrate high concentrations of certain heavy metals, par-
ticularly cadmium. The location of the endemic area is seen in
figure 8:1.

Hagino and Kono reported about the Itai-itai disease at the 17th
meeting of Nihotx-Rinsho-Geka-Ikai (The Japanese Society of Clin-
ican Surgeons) in 1955, making the first official use of the
name (Kato and Kono, 1966). The same year, Hagino et al. reported
on the disease at the 9th Hokuriku Medical Congress (Hagino,
1969a). In 1961. Hagino and Yoshioka reported that heavy metals,
especially cadmium, would play an important part as etiological
factors of the disease (Kato and Kono. 1968). Epidemiological

and clinical studies were started on a larger scale in the 1960's
by groups supported by the  Japanese government. The Japanese
Ministry of Health and Welfare in 1968 declared, "The Itai-itai
disease is caused by chronic cadmium poisoning, on condition of
the existence of such inducing factors as pregnancy, lactation,
unbalanced internal secretion, aging, deficiency of calcium,

8.2.1  Symptoms and signs
The clinical course of the  disease has been described by Takase,
et al., 1967 (summarized in English by Tsuchiya, 1969), Hagino,
1968a and b, 1969a. Ishizaki, 1969b, Murata et al., 1969, 1970,
and Tsuchiya, 1969. The greatest number of the patients have
been treated by Hagino and/or Murata. Figure 8:18 shows a patient
with advanced skeletal deformities. Figure 8:19 shows multiple
pseudofractures on X-ray of the ribs in one patient, (Murata
personal communication).

From Murata et al., 1970, the clinical manifestations can be
summarized as follows. Most of the patients are postmenopausal
women with several deliveries (average: 6). The most character-
istic features of the disease are lumbar pains and leg myalgia.
Pressure on bones, especially the femurs, backbone and ribs pro-
duces further pain. Another characteristic of the disease is a
waddling gait caused by bone deformation. Such conditions contin-
ue several years until one day the patient experiences a mild
trauma and finds herself unable to walk. She is then confined to
bed and the clinical conditions progress rapidly. Not only the
bones of the extremities but also the ribs and other bones are
suspeptible to multiple fractures after very slight trauma such
as coughing. Skeletal deformation takes place, with a marked de-
crease in body height.

6.2.2  Laboratory examinations   lood
Blood examination has shown hypochromic anemia in most patients.
Serum-Fe levels have been low in many. The erythrocyte sedimen-
tation rate has been elevated in some. Almost no deviation from
the normal has been observed in serum protein and albumin/globulin
ratios. The levels of calcium and inorganic phosphorus in serum are
often low, while the alkaline phosphatase level is high. Data from
studies by Murata et al . , 1970 are shown in figure 8:2.
6. 2. 2.2  LJri/ia.ry_
Proteinuria has always been found. In most cases, glucosuria has
also been present. While urinary calcium levels have been normal,
urinary phosphate has been reduced. The urinary amino acid levels
have been above normal (Takase et al., 1967, Takeuchi et al.,
1968, Ishizaki, 1969b, Murata et al., 1969 and Tsuchiya, 1969).
Quantitative determinations have shown an increase in cadmium
concentration and a decrease in zinc concentration in blood and
urine, in comparison with control subjects (see, for example,
Murata et al., 1970 and figure 8:11 from Ishizaki, 1969b).

In Itai-itai disease, proteinuria, glucosuria and ami no-aciduria
are considered signs of renal dysfunction. On separation by paper
electrophoresis,  a typical tubular protein pattern occurs in
cases of Itai-itai disease and also in the preceding stages (pro-
teinuria withouirbone changes), as shown recently (Piscator and
Tsuchiya, unpublished data). They examined 10 female patients
with Itai-itai disease and 12 persons (10 women and 2 men)  from
the endemic area with only proteinuria and glucosuria. The  pat-
tern found was similar to that observed in chronic occupational
cadmium poisoning. In figure 8:3 some of these patterns are shown
(compare with figure 6:2).

Further evidence that the proteinuria observed in women in
the endemic district is similar to the one seen in workers
exposed to cadmium and distinctly different from the one seen
in glomerular disease is shown in figure 8:4 (Piscator and
Tsuchiya, unpublished data). The figure shows patterns of
urinary proteins separated by electrophoresis in polyacryl-
amide gel (disc-electrophoresis).

Still further evidence that the proteinuria is of a tubular type
has been obtained by using gel filtration on Sephadex G-100,
(Piscator and Tsuchiya, unpublished data). The main part of
the urine proteins from cases and suspected cases of Itai-itai
had molecular weights less than that of albumin. Among these  low
molecular weight proteins, immune globulin chains and ^2-micro-
globulin were found, as has earlier been demonstrated in cadmium
workers by Piscator, 1966.

Electrophoretic examinations of urine proteins have also been
performed by Fukushima and Sugita, 1970. In 8 patients, they
found a relatively small percentage of albumin and a dominance
of 0(2- /3 - and ^f-proteins, also indicating a tubular type
of proteinuria.

Takeuchi et al., 1968, and Murata et al., 1970 investigated 4
and 3 patients,respectively, with Itai-itai disease especially
concerning renal function. They stated that tubular function  de-
fects were found/*whereas glomerular involvement was not detected

8.2.3  Histo-pathological changes
The following, though very incomplete, are the only data on
histological changes available to us (for cadmium concentrations
in organs, see section

6.2. 3.1  K.idne_ys_
Kajikawa et al., 1957, found in two resections senile arterio-
sclerotic contracted kidneys and nephropyelitis. Takeuchi et al.,
1968, found in biopsy specimens from three patients no marked
changes in the glomerules. In the tubules, atrophic changes, with
flattening of the epithelium, were seen.  Bone_
Ishizaki, 1969b, citing Kajikawa et al., 1957, and his ownAmate-
rial, has described histological findings in bone from autopsies.
The changes have been consistent with those found in osteomalacia.
X-ray findings were also characteristic of osteomalacia.  On the
basis of two resected cases and biopsy of seven cases, Ishizaki
and Fukushima, 1968, (quoting findings by Kajikawa et al., 1957)
concluded that the main pathological and histological findings
were characteristic of osteoid formation and osteoporosis. Kono
et al., 1961, found the Itai-itai disease very similar to common
forms of osteomalacia. However, they found fewer osteoblasts in
Itai-itai disease biopses than usually found in osteomalacia.

Ishizaki and Fukushima, 1968, discussed the clinical diagnosis
of Itai-itai disease. They pointed out that the first and second
stages could reasonably be considered to be renal dysfunction
and bone changes, respectively. However, even if a specific diag-
nosis of renal impairment were possible, patients so diagnosed
who can carry out their daily lives unhampered until bone symp-
toms develop cannot from a practical standpoint be included in
the Itai-itai group. Because the subjective symptoms and the
bone signs clinically observable through X-rays are very unsper
cific in the early stages, the diagnosis at that time could
reasonably be based on blood signs of osteomalacia, including

increased alkaline phosphatase and decreased serum inorganic

phosphate. The authors pointed out that a roentgenological diag-
nosis would not be helpful in the early stages because detect-

able X-ray changes would not be evident until the disease has
                    •            •  • •  ;».-••-•	..,.„».._....		
developed to some extent. Moreover* as the disease is frequent
in menopause  and in old age, menopausal or senile osteoporosis

could be mixed with the Itai-itai disease. To avoid such mis-

takes, it should be necessary to require specific signs of

osteomalacia (Milkman's pseudofracture) for the roentgenological

diagnosis of Itai-itai disease.

Based on elaborate discussions, the Itai-itai disease research

group of 1962-1965 has worked out a standard for the diagnosis

of Itai-itai disease, to be used in the epidemiological research
(Kato and Kono, 1966). The following observations should be noted:

   A. Subjective symptoms
      1. Pain (lumbago, back pain, joint pain)
      2. Disturbance of gait (duck gait)

   B. Physical examination
      1. Pain by pressure
      2. "Dwarfism"
      3. Kyphosis
      4. Restriction of spinal movement

   C. X-ray
      1. Milkman's pseudofractures
      2. Fractures (including callus formation)
      3. Thinned bone cortex
      4. Decalcification
      5. Deformation
      6. Fish-bone vertebrae
      7. Coxa vara

   D. Urine analysis
      1. Coinciding positive tests for protein and glucose
      2. Protein (*)
      3. Glucose (*)
      4. Decreased phosphorus /calcium ratio

   E. Serum analysis
      1. Increased alkaline phosphatase
      2. Decreased serum inorganic phosphate

The subjects are classified into the following five groups:
    I:    Surely Itai-itai patients
    i:    People deeply suspected for Itai-itai disease
    (i):  People suspected for Itai-itai disease '
    (0):  People needing follow-up
    0:    People with no suspicion of Itai-itai disease

The methods for diagnosis differed a little with each year, as
stated in Kato and Kono, 1966, and a sixth group (I) is some-
times named. In some reports the groups are defined as follows
(Ishizaki and Fukushima, 1966, arid Fukushima, personal communi-
cation) :
    I:    Patient (typical bone manifestations on X-ray)
    (I):  Person cured of Itai-itai disease
    i:    Person deeply suspected (bone signs but not typical *
          glucosuria  *  proteinuria  *  increased alkaline
    (i):  Person suspected (slight bone signs on X-ray *
          proteinuria *  glucosuria + increased alkaline
    0 . :  Person with need for continuous observation (urinary
     °    and/or blood signs)
    0:    Person with no suspicion

Sometimes only the I-type of patients is meant when the "number
of patients" is discussed, but in other circumstances, other
groups are also included in the "patients".

The question of the differential diagnosis of Itai-itai disease
has later been taken up in more detail by a study group organized
by the Japanese Association of Public Health in connection with
an evaluation of some suspected cases of Itai-itai  disease. As
the criteria applied have no direct bearing upon the material
referred to in the present report, they are not commented upon.
For further information, reference is made to a publication by
the Japanese Association of Public Health, 1970a.

Since the Itai-itai disease was first discovered in the Toyama
Prefecture, the most detailed epidemiological studies have been
performed in this area. However, the Japanese Ministry of Health
has recently promoted studies in other areas where exposure to
cadmium occurs. The studies' in the Toyama area and thereafter in
other areas will be described.

6.4.1  Epidemiological studies in Toyama Prefecture   96 2l965 EpidemioOia  research
The limited research on the epidemiology of the disease prior
to 1963 must be classified as preliminary or pilot studies.
Since no diagnostic standard had been agreed upon, the differ-
ent studies defined the disease differently. An epidemiological
survey made between 1962 and 1965 in Fuchu-machi, Toyama City,
Osawano-cho, Yatsu, Nyuzen-cho, and Tonami City was evaluated
according to the  1963 diagnostic standard (Kato and Kono, 1968).
All of these places are in the Toyama Prefecture. All females
over 40 years of  age were selected, except in Tonami City, where
males over 40 years of age were also included in the 1,100 sub-
jects examined. Under examination of a total ,of 3,645 subjects,
28 patients, 14 deeply suspected and 19 suspected subjects had
been found by 1965 in the endemic districts located along the
Jintsu River, (see table 8:1). On the other hand, in Ota (Toyama
City), located along another river in the endemic district, nei-
ther patients nor suspected patients were found among the 508
females over 40 years of age. 334 of whom were examined in 1964
in the same way as in the endemic districts. Also in Tonami
City and Nyuzen-cho, located along other rivers in Toyama Prefec-
ture, neither patients nor suspected patients were observed.  These
studies made clear that the Itai-itai disease was found only  in
specific districts in the Jintsu River basin. Further epidemiolog-
ical research therefore was concentrated along this river.

In 1967, a larger, better structured epidemiological study was
performed by the Toyama Prefecture Health Authorities in co-
operation with Kanazawa University in an attempt to find and to
treat all Itai-itai patients  (the data under this section are
from Kato and Kono, 1968, and Ishizaki, personal communication,
unless otherwise stated).  Groups studied and selection of subjects for final
           diagnostic procedure
A total of 6,717 subjects, all inhabitants over 30 years of age
and of both sexes of Fuchu-machi, certain parts of Toyama City,
Osawa-cho and Yatsuo-cho, were included in the first screening
made by a questionnaire, seen in table 8:2, and by semi-quanti-
tative determination of protein and glucose in urine.   This
screening was performed on 6,114 persons, 91 percent of the
6,717 subjects origiHally selected for the study,

Based on the results of the first screening, 1.911 persons were
selected for the second examination according to the procedure
referred to in figure 8:5. Out of the 1,911 people selected for
the second examination, 1,400 underwent the examination, which
included a medical interview, general clinical examination, and
X-ray of the right upper arm and shoulder. As a result of the
second examination, 451 persons were selected for a final exam-
ination. The exact basis for this selection has not been possi-
ble to elucidate^ but among important criteria were bone changes.

6.4. 1.2.2  Final diagnostic examination (Third examination)
Out of the 451 persons selected for a final examination, 419
were examined. The examination included a medical interview,
X-ray of the pubic region, orthopedic examination, urine analy-
sis for glucose, protein, calcium, phosphorus, creatinine, cad-

mi urn, lead, and zinc, as well as serum  analysis of alkaline
phosphatase and inorganic phosphorus. All of these analyses
were not performed on all persons.  X°jba^ n_umbe_r_of_ £as_es_ £"P_It^ai.~i.t£i__di^se_as_e__
It is not possible to precise a figure  on the  incidence of
Itai-itai disease over  the  years.  The 1967 epidemiological
survey is cross-sectional,  giving  only  prevalence data at the
time of the study.   It  is estimated that nearly 100 deaths
due to the Itai-itai disease have  occurred up  until the end of
1965 (Yamagata and Shigematsu, 1970). The following numbers of
persons with Itai-itai  disease were found: 1:50, i:17, (i): 31
and 0 . :136. See table  6:3  (from Ishizaki and  Fukushima,  1966)
for the distribution of examined persons according to place of
residence, sex and age. The abbreviations for  groups as used in
this particular report  are  explained in table  6:1. The Toyama
Prefectural Health Authorities now continuously register  all
living patients. Several new cases have been diagnosed since
the 1967 study. Figures from September, 1966,  are given in
table 6:4.

The latest available figures on the total number of cases are
stated by Ishizaki,  1969c.  as, until the end of 1966, 57  pa-
tients, 56  suspected,              and 200 requiring observation.
However, these figures  are  not directly comparable to those in
tables 6:3 and 8:4 because  Ishizaki defined the groups somewhat
differently than earlier. The "observation group" included sub-
jects who had recovered.

6.4. 1.4  A_ge_ and sex
According to table 8:4  from September,  1968, only one male was
placed in the group  of  patients. However, according to the 1967

.epidemiological  research.  5  male  patients  or suspected patients
were found, as seen  in  table 8:3.  The  reason for the registra-
tion of only one male patient  in  the  table from September,  1968,
is not clear. Among  the  observation subjects there were an  ap-
preciable number of  men.

Noting the age distribution  in table  8:3 from the 1967 report,
one can conclude that the  osteomalacia has been found only  in
women of 45 years of age or  older. No  patient was found in  the
age group below  44 years,  but  two observation cases were reg-
istered.  F_reqjjericy_ £f_new_ceJS£S_of_ l.t^i.l.ijtai. d_is_eas£
Hagino  (personal  communication)  had the  impression that the fre-
quency  of disease onsets was  higher in  the  1950-1960 period than
in the  1960-1970  period. At  the  same  time,  he pointed out that a
number  of cases not  known before are  still  diagnosed yearly.

By means of the 1967 epidemiological  research and the subsequent
registration of all  patients  by  the Toyama  Prefectural Health
Authorities, a year  of onset  was estimated  for each patient,  as
seen in table 8:5. From this  data,  it  is  evident  that a majority
of the  presently  registered  patients  first  complained of symp-
toms in the period between  1945-1964  but  10-15 percent did not
complain of symptoms until  1965  or later. As many Itai-itai pa-
tients  who contracted the disease several years ago must have
died by 1968 (see,  great caution must be exercised in
interpreting the  data.

6.4. 1.6
The locations of the different  population  centers  within the
Toyama Prefecture are seen on the  maps  in  figures  8:1  and 8:6.

It has become evident from the research that the disease has
only been found in a limited area around the parts of the Jintsu
River near Toyama City, where its water is used for irrigation
of rice fields. The prevalence of the Itai-itai disease in dif-
ferent parts of the endemic area has been best illustrated by
the detailed survey of  1967, the results of which can be seen
in figure 8:6. from Ishizaki and Fukushima, 1966. The frequency
of the disease is there illustrated by the percentage of women
over 50 years of age having or suspected of having the Itai-itai
disease. The 1967 research group also analyzed the cadmium con-
centration in the upper stratum of the soil in the paddy fields
(see and found a striking correlation with the preva-
lence of the Itai-itai  disease, even within the endemic area
(see figures 8:6Jand 8:7).  Prevalence of proteinuria a_ncJ £
In addition to sure or suspected cases of Itai-itai disease, a
great number of persons with proteinuria and/or glucosuria have
been found in connection with the 1967 epidemiological studies.
The total prevalence of proteinuria  (sulfosalicylic acid, tri-
chloracetic acid or testtape) and glucosuria (Benedict's reac-
tion) in males and females and in different a*ge groups is shown
in figure 8:8 from Ishizaki, 1969b.  The number of persons exam-
ined is given in table 8:6 (Ishizaki, personal communication).

As can be seen, about 50 percent or  more of inhabitants older
than 60 in the endemic area had proteinuria. Among those over
70, 70-60 percent had proteinuria. The prevalence was somewhat
higher among females. The prevalence for both sexes was con-
siderably higher than in a noa-endemic area of the Toyama Prefec-
ture. However, even in such a non-endemic district, the preva-
lence was high, especially in women. Thus, about 20 percent or
more of women older than 60 and 30-40 percent older than 70 in

non-endemic districts had proteinuria. From the methodologi-
cal point of view, exactly comparable figures from other parts
of Japan are not available. In a study of the epidemiology of
proteinuria on about 5,000 persons from Hiroshima and Nagasaki
(comprising a portion of the clinical sample under study at
the Atomic Bomb Casualty Commission), however,  considerably
lower prevalence data were found. The methods used were sulfo-
salicylic acid or testtape and positive reactions were con-
firmed with nitric acid. Results of the study are seen in table
8:7. The results of the study of people living on Tsushima Is-
land (section also showed considerably lower preva-
lence of proteinuria in the non-contaminated areas.

Since either proteinuria or glucosuria can indicate a renal
tubular impairment, the occurrence of both in a person is a
stronger indication of such a renal defect.  The concurrent
appearance of these two conditions in different age groups in
different areas of the Toyama Prefecture is  shown in figure 8:9,
Whereas the frequency in age groups up to 45 years has not been
different from that found in a non-endemic area, a very clear
difference can be seen in age groups, of 55 years and older, in
both women and men. No information on the number of persons
examined is available. Concurrent glucosuria and proteinuria
in women of the endemic area can also be. seen in figure 8:30,
The women born and spending their lives in the endemic area
have had a higher prevalence of proteinuria  and glucosuria
than women born elsewhere but living in the  endemic area at
least 20 years. It is not known whether or not the differences
are statistically significant.  H
6.4. 1. 6. 1  Hereditary factors
Dent,  1956, has described a number of renal tubular reabsorp-
tion defects based on heredity which have given rise to osteo-

malacia. Therefore it is of interest to seek evidence of simi-
lar hereditary factors in the Itai-itai disease. Ishizaki,  1969b.
reported that in many families in the endemic district, both the
farmer's mother and wife had contracted the disease. No cases
had occurred in women from the endemic district who had married
and moved to a family in the non-endemic district.  These facts
indicate that the etiology rests on environmental rather than
hereditary factors.  Dietary factors
The classical form of osteomalacia is based on a deficiency of
Vitamin D. In the beginning of the research on the  Itai-itai
disease, dietary and climatological factors were assumed to
play an important role in its etiology.

The Toyama Prefectural Health Authorities performed a survey on
the dietary conditions iVi 200 households in the endemic area
during 1955-1956. The results are given in table 8:8. For com-
parison, averages for Sweden in 1960 are also given. It is  evi-
dent that the dietary standard in the Itai-itai patients'  homes
and in the endemic area as a whole is not much different from
the mean in the Toyama Prefecture or from the Japanese average.
It is not known to what extent the figures for the  different
areas in Japan are comparable to the figures for Sweden, but
for certain dietary components, the large differences noted
are not likely to disappear, even if the figures are corrected
for the different methods of calculation. As Vitamin D is  a
known essential dietary factor when discussing osteomalacia,
it is unfortunate that no Japanese figures for this vitamin
are available. The Vitamin A and fat intakes in the Itai-itai
patients are lower than the Japanese average and considerably
lower than the Swedish average. It is therefore probable that
the Vitamin D intake is also lower. If such is the  case, a

great exposure to sunlight could compensate for the low intake
of Vitamin D. However, since the endemic area has a rainy cli-
mate, and since the women dress in such a way that they screen
off a great part of the sunshine, this compensation is not like
ly. A higher calcium intake could also partly compensate for a
low level of Vitamin D, but the calcium intake in Japan is very
low. The figures from the investigation of 1955-1956 in the
homes of the Itai-itai patients represented a mean intake for
all family members. Several investigations in various countries
have shown that the calcium intake is usually much lower in
women and therefore it is likely that the women in the endemic
area consume significantly less calcium than indicated by the

It must also be remembered that the nutritional situation in
Japan during and immediately after the Second World War was
poor. Insull, Oiso and Tsuchiya, 1968, documented acute gen-
eralized malnutrition problems arising in 1936 and 1945. They
cited evidence showing that the heights of children during
and directly after the war were significantly retarded.  Profession and other factors
In connection with the 1967 epidemiological study, information
on certain socio-economic factors about Itai-itai patients and
"controls" was obtained (Ishizaki, personal communication). For
each Itai-itai patient, a "control", matched for age and sex
and living in the endemic area very close to the patient, was
chosen. The results are given in table 8:9. There are certain
differences between the groups. The patients had lived longer
in the same area, had had more pregnancies, had drunk water
from the Jintsu River to a greater extent, and had lower in-
comes. No information was given on, for example, the occurrence
of proteinuria and/or glucosuria in controls.

8.4. 1 . 10  Cocenrati>nso   sv   Basi   rnB
The 1962-1965 research group analysed urine from inhabitants
of different parts of the Toyama Prefecture* The method of
sampling in the various patient categories can not be known
through literature available to us. Values reported, howaver,
showed that cadmium concentrations in urine from persons in
the endemic area were higher than from persons in other parts
of the Toyama Prefecture, (Ishizaki et al . , 1965. Tsuchiya,
1969, and Ishizaki, 1969a). Lead and zinc  values, on the oth-
er hand, showed no geographical differences (Ishizaki et al.,
1965, and Tsuchiya, 1969).  The  1967 research group, as referred
to in Ishizaki's report,  1969b, also analyzed urine concentra-
tions of  cadmium  (probably by  atomic absorption after extrac-
tion). Increased concentrations were found in persons coming
originally from the endemic area (see figure 6:11).
6.4,1.11  C^oruje^nt^rjjt^ons^oJ^  catJmi_um JL/»
Few values of cadmium  in organs  from Itai-itai patients have
been reported. Some early  data  from one patient described con-
centrations in bones.  However,  in  this case, the different or-
gans had been stored together in formaldehyde for several years,
(Kobayashi, personal communication), so that the values must be
considered unreliable.

Ishizaki, Fukushima and Sakamoto,  1970b,  reported organ values
(atomic absorption) from autopsies on four  Itai-itai patients.
The results are given  in table  8:10li Formaldehyde preservations
were not used. At the  same time, cadmium  analyses were per-
formed on organs from  38 controls  who died  in hospitals in Kana-
zawa. All of them had  been living  in non-endemic areas in or
near Kanazawa. Results are shown in figure  8:12. As can be seen
by comparing table 8:10 with figure 8:12, the cadmium content
of the liver was 5-10  times  higher in Itai-itai patients than

in the controls in the same age group. The patients' kidney
values, however, were lower than those of the controls. The
authors stated that the low kidney values in the Itai-itai pa-
tients could be explained by the advanced kidney damage. The
values given should also be compared with "normal values" from
Japan and other countries and with data from workers industri-
ally exposed, with signs of cadmium poisoning,  (see
and Such, a comparison stresses the accumulation of
cadmium in liver and pancreas of the Itai-itai patients.  Co£ce_n;trat;Ujns__of_ hea_vy_ fj]9tal.s_*!l £he_ env/ironme_nt_
As has been discussed, most of the Itai-itai patients displayed
their symptoms many years ago. If heavy metals caused the dis-
ease, even exposure several decades earlier must have been of
importance. However, no quantitative information on such expo-
sure is available.

After the theory about cadmium as a cause of the Itai-itai dis-
ease was advanced, the Jintsu River became suspected as the
carrier of the cadmium from the Kamioka mine to the endemic
area. Kobayashi, 1970, stated that the increased production at
the mine together with faulty treatment of waste water polluted
the Jintsu River heavily during the Second World War. He ex-
plained that particles carried by the river became deposited
in the rice fields. Damage to the rice crop prompted a severe
dispute between the farmers and the owners of the mine. Ishizaki's
studies (personal communication) on cadmium content in year rings
from cedar trees may also speak in favor of a higher concentra-
tion of cadmium in the Jintsu River several years ago.

In 1959 Kobayashi and Yoshioka, as cited in a report by Yamagata
and Shigematsu, 1970, analyzed samples of rice from the endemic

area. Values (ppm in ash) in polished rice were given as 120-
350 ppm in exposed areas, compared with 21 ppm in a control
area. In the root of rice plants, corresponding figures were
690-1300 and 35 ppm, respectively. No information about the
representativeness of the samples was reported.

In 1967, a study headed by Shigematsu on the distribution of
cadmium in the endemic area was made under a grant from the
Ministry of Health and Welfare. This study is included in
the above mentioned report by Yamagata and ShigematsU| 1970.
In water upstream from the Kamioka mine and tributaries of
the Jintsu River, cadmium was detected in trace amounts or
not at all in the samples taken. In water downstream from
the mine,  a maximum value of 0.009 ppm was found. Out of
four samples  from the drainage from the mine, three contained
0.005-0.06 ppm (pH about 7-8) and one contained 4 ppm (pH
2.8) of cadmium. Near the* drainage area of the mine, cadmium
concentrations of 363 and 382\were found in suspended materi-

Samples of paddy soils irrigated with water from the Jintsu
River and from its tributaries, respectively, were analyzed.
The comparison of concentrations of cadmium found is shown in
figure 8:7. The river-irrigated soil showed a much higher con-
centration. In figure 8:6, the prevalence of sure or suspected
cases of Itai-itai disease in different areas around the Jint-
su River and tributaries is shown. When figures 8:7 and 8:6
are considered together, the association between high concen-
trations of cadmium in the paddy soils and the Itai-itai dis-
ease is obvious.

Yamagata and Shigematsu also reported cadmium concentrations
in unpolished rice. Samples from paddy fields irrigated with

water from the Jintsu River contained 0.35-3.36 ppm (average:
1.0, wet weight), while samples from paddy fields irrigated
with water from the tributaries showed much lower values,
with a maximum concentration of 0.11 ppm. The normal concen-
tration of cadmium in polished rice from all areas in Japan
has shown an average value of 0.07 ppm. Ishizaki, Fukushima
and Sakamoto, 1970a, reported cadmium content in 340 samples
of foodstuffs on the market in Japan as a whole. The reported
cadmium levels in grain and vegetables were not higher than
those in the United States and in Germany. Organs of sea
mollusca and Crustacea contained high levels of cadmium. Very
high values were observed in livers of some sea mollusca,
for example, 10-110 ppm (wet weight) in some cuttlefish and
92-420 ppm in Babylonia Japonica, a roll shell. These findings
are in agreement with the known accumulation of several ele-
ments, including cadmium, by mo Husks (see e.g., Pringle et al.,

Based on the National Nutrition Survey of 1966 and on available
data on cadmium content in food, a representative value for
the daily intake of cadmium in a Japanese diet has been esti-
mated as 60 ^jg by Yamagata and Shigematsu, 1970.  A breakdown
of the 60 ;jg indicated that 23 ^ig of cadmium should come from
an intake of 335 g of polished rice with a concentration of
0.07 ppm. The daily intake of cadmium in the endemic area was.
calculated as 600 ^ug by assuming an average cadmium concentra-
tion in rice of 1 ppm and a concentration in other foodstuffs
produced and consumed locally about 10 times the value for
Japan as a whole.

6.4.2  Other areas in Japan under survey for Itai-itai disease
The occurrence of the Itai-itai disease along the Jintsu River
with cadmium as a suspected cause has stimulated a search for

signs of cadmium intoxication in other areas contaminated with
cadmium. Figure 8:13 shows the distribution of mines dealing
with sulphide ores of copper, lead and zinc as well as smelting
works. The figure also shows four areas, apart from the Jintsu
River basin, selected for more detailed study. In a statement
of March 27, 1969, the Ministry of Health and Welfare defined
these as the coastal areas of the Namari River and the Nihazama
River in Miyagi Prefecture,  the Usui River and the Yanase River
in Gumma Prefecture, and the Sasu River and the Shiine River on
Tsushima Island of Nagasaki  Prefecture. On May 28, 1969, the
coastal area of the Okudake  River of Ooita Prefecture was also
included. A considerable amount of information from Tsushima
Island has been made available to us.
6.4.2. 1  JSas_u_an_d_Shu i_n£  _._.
6.4.2. 1 . 1  Medical examinations
Preliminary medical studies were carried out in  1965. The re-
sults pointed out that Kashine, downstream from  a mine in the
River Sasu basin, was a most suspect area. New studies were
performed in 1968, and on a more comprehensive basis, in 1969.
The results of the last mentioned study are available in a re-
port by the Department of Health, Nagasaki Prefecture, March,
1970* The medical examinations were carried out  by the staff
of the Section of Health, Izuhara. Urine analyses were made at
the Laboratory of Hygienic Chemistry, Faculty of Pharmaceutical
Sciences, Nagasaki University.

The area under investigation consists of a control area: the
village Are in the basin of the Are River and of an observa-
tion area: villages in the basins of the rivers  Sasu and
Shiine; Hikage-Kamiyama (including Ohita, Kyozuka, Jifu, Himi
and Wakata), Shimobaru (including Tokoya and Nagon), Komoda
(including Komoda-hama) , Shiine (including Shiine-hama) and

X/ The report was  translated  into English through the curtesy
   of Professor  Eigo  Takabatake, Faculty of Pharmaceutical
   Sciences, Nagasaki University.

Kashine (including Uragochi). This area can be seen in figure
8: 14.

In the area under observation, 653 people over 40 years of age
had been living for at least 5 years. The corresponding number
for the control area was 176. Out of a total of 829 subjects,
541 were medically examined. The number of subjects and the
absolute and relative number examined in different areas di-
vided into men and women and into different age groups are
given in table 8:11. As can be seen, the relative number ex-
amined differed considerably among the different areas. This
variation is not so marked for women but for men it is note-
worthy that only 20 percent of those living in the control
area. Are, participated. It was not stated in the report wheth-
er or not the examined and the non-examined persons differed
from each other in any way.

The investigation included an interview, urinary protein (test-
tape) and glucose (testtape) determinations. X-ray examination
of chest, and analyses of urinary content of cadmium.  The pro-
tein and glucose examinations were performed on 522 subjects.
The results are given in table 8:12. There is' a considerably
higher prevalence of both proteinuria and glucosuria in the
Kashine, Shiine area than in the other areas.

In the report, prevalence of proteinuria in different age groups
is given for the areas grouped as follows: Kashine and Shiine,
Shimobaru and Komoda, Hikage-Kamiyama and Are. The results can
be seen in figures 8:15 and 8:16. It is not possible from the
report to know the exact number in the various age groups. If
the fact that protein examinations were carried out on only
522 of the 541 subjects examined is not considered, the age
distribution will be as shown in table 8:13.

No cases of Itai-itai disease with bone changes were diagnosed.
It is not clear how many persons were examined with regard to
chest X-ray and cadmium analyses. Concerning possible exposure
to cadmium, note in figure  8:14 that Hikage and Kamiyama are
upstream from the mines.

Figures 8:15 and 8:16 undoubtedly show a considerable difference
between the Kashine-Shiine  areas and the other areas. The dif-
ference increases with age  and time of residence in the area.
The increased prevalence of proteinuria is found in both men
and women. One must stress, however, that the number of exam-
ined subjects in some groups was extremely small, which invali-
dates any precise interpretation of the data. Furthermore, the
percentage of residents participating in the examination dif-
fered from area to area. As has been mentioned above, only 20
percent of the men in Are were examined. The bias of differ-
ences in the participation  in the different areas can not be
evaluated in detail. We see no reason, however, that the dif-
ferences found in prevalence of proteinuria and glucosuria was
due to any substantial degree to differences in participation
in the examinations.

From the report it is possible to separate farmers from other
occupational groups. The numbers are too small to divide into
age groups, but the total prevalence of proteinuria and glucos-
uria in farmers is presented in table 8:14. The high prevalence
of proteinuria and glucosuria among both sexes in the Kashine-
Shiine areas is again apparent.

Urinary cadmium analyses (atomic absorption after extraction)
were carried out on 45 of the persons who had had positive
results for protein and/or  glucose. Results of these exam-

inations are shown in figure 8:17. As can be seen, the cadmi
levels are high, particularly in the Kashine area.
From the group of men and women in Kashine with positive test
results for protein and/or glucose in urine but without hyper-
tension, nine were selected for more detailed examination. The
results were discussed within the group dealing with the dif-
ferential diagnosis of Itai-itai disease (Japanese Association
of Public Health, 1970a).

Three women, aged 47-67 years, agreed to hospitalization. Detailr-
ed examinations were carried out, including tests of renal and
hepatic function, determination of electrolytes in serum and
urine, determination of cadmium in urine, electrophoretic se-
parations of serum and urine proteins, urine cultures, pyelor
graphy, renograms and renal biopsy.

In one woman (47 years of age) with a daily excretion of 780 mg
protein, the electrophoretic pattern of the urinary proteins
was typical for a tubular proteinuria. She excreted more than
30 Jug of cadmium per day. Urine culture was negative. Histologi-
cal examination of renal tissue obtained by biopsy showed slight
changes mainly in the proximal tubules. There were no marked
changes in the interstitial tissue. Creatinine clearance was
normal, whereas the PSP-test showed tubular impairment. The
study team concluded that this was a case of pelvic nephritis.
It is of course difficult to make a detailed evaluation on the
basis only of the information in the publication. It seems,
however, that this patient showed many findings typical for
chronic cadmium poisoning.

The other two patients are more difficult to evaluate, but they
had a decreased PSP-excretion, which would indicate tubular im-

pairment. In one patient (67 years of age), the electropho-
retic pattern of the urinary proteins was of a mixed glomer-
ular-tubular type. Urinary protein excretion was 900 mg/day.
Histological examination of renal tissue showed no marked
changes in the glomeruli but .showed slight changes in the
tubules. This patient was judged by the study team to be suf-
fering from senile nephrosclerosis, but also in this case we
would not exclude cadmium as the cause of the tubular impair-
ment. The third patient  (55 years of age) was diagnosed as
having pelvic nephritis. The electrophoretic pattern was of
a more glomerular type and bacteria were found in the urine.  Cadmium exposure
Data concerning the concentration of cadmium in foodstuffs have
been obtained partly from personal communications with repre-
sentatives for the Department of Health, Nagasaki Prefecture
and partly from a published report (Japanese Association of
Public Health, 1970b), giving results from a cooperative study
on uptake and accumulation of cadmium in areas under observa-
tion. In the cooperative study, headed by I. Shigematsu, the
measured values from the various prefectural institutes were
cross-checked and considered to agree fairly well, so that it was
considered possible to refer to the  figures without correction.

The data from the Tsushima Island covered 23 samples of self-
stored rice and 19 samples of self-produced bean paste from 22
families in the contaminated areas and 9 families in the con-
trol area. The average concentration of cadmium in rice (ppm,
dry weight) in the contaminated areas taken as a whole was
0.37 ppm (range: 0.03-1.02). In the control area. Are, the
average content was 0.08 ppm (range: 0.02-0.15). The content
of cadmium in rice as well as in bean paste for the different

areas under observation and for the control area. Are, is seen
in table 8:15. For other foodstuffs, the different areas can
not be compared in a similar way, but the control area can be
compared with all other areas taken together as an observation
group. Values, given in ppm, wet weight, are shown in table 8:16.

For the evaluation of the total exposure via food, it is essen-
tial to know the consumption of different foodstuffs. In the
cooperative study mentioned above (Japanese Association of Pub-
lic Health, 1970b), this question was also explored in the
areas studied, (Namari and Nihazama basin in Miyagi Prefecture,
Usui and Yanase basin in Gumma Prefecture, Sasu and Shiine
basin in Nagasaki Prefecture and Okudake basin in Ooita Prefec-
ture). The total amount of food intake ranged from 972 g to
1586 g with an average of 1264 gram. For comparison, the aver-
age intake for farmers in Japan is given as 1216 g in 1967.
The daily intake of rice varied from 267 g to 404 g, of wheat
from 27 to 78 g, and of potato from 38 to 107 g. In other veg-
etables and mushroom, it varied from 153 to 357 g, in raw fish
from 22 to 94 g, in dried fish from 24 to 59 g and in milk from
9 to 54 g.   ther areas ijnder observatio
No medical data are available but the report by the cooperative
study group (Japanese Association of Public Health, 1970b), con-
tains data on cadmium content in foodstuffs. Table B:15  gives
data for self-stored rice and bean paste. It is obvious that
several of the areas under observation have considerably higher
contents of cadmium in these foods than control areas. The high
content of cadmium in rice from the control area in the Usui-
Yanase basin is noteworthy, meaning perhaps that this area is
in fact a contaminated area.

Some data on airborne cadmium exist from Annaka City district
in Gumma Prefecture. The cadmium in air is considered to be
due to emissions from a refinery with a capacity of 14,500
tons per month, the largest in Japan. Values from three sam-
pling stations in the district showed 0.008-0.235 (average:
0.104), 0.044-0.380 (average: 0.166) and 0.020-0.142 (average:
0.055) jjg/m3 (Yamagata and Shigematsu. 1970).
Clinical material has shown that the Itai-itai disease can be
classified as a form of osteomalacia. Generally, osteomalacia
can be divided into the following categories:
   A. Vitamin D deficiency
   B. Malabsorption of Vitamin D and bone minerals
   C. So-called Vitamin D resistant osteomalacia
Since hyperparathyroidism sometimes shows a clinical picture
similar to osteomalacia,' a differential diagnosis can be very
difficult. Therefore, it has also occasionally been difficult
to differentiate between the Itai-itai disease and hyperparathy-
roidism, as discussed by Takase et al., 1967, and in a recent
report on the differential diagnosis of the Itai-itai disease
(Japanese Association of Public Health, 1970a). In primary
hyperparathyroidism, the patients have an elevated blood calcium
level not seen in cases of osteomalacia. However, a more or less
decreased calcium level, seen in cases of osteomalacia, can
stimulate increased parathyroid activity, so-called secondary

6.5.1  Vitamin D deficiency
This type of osteomalacia is dependent on the combination of
lack or low intake of Vitamin D in the diet and deprivation of
ultraviolet irradiation. This combination, together with a low
intake of calcium, and a simultaneous high demand for calcium

and Vitamin D during pregnancy and lactation have in some cases
given rise to osteomalacia even in countries with much sunshine,
as documented by Groen et al., 1965 (see also the review by
Arnstein, Frame and Frost, 1967). In the areas where the Itai-
itai disease is seen, the consumption of foodstuffs rich in cal-
cium and Vitamin D such as milk and milk products is very low.
Thus, the Vitamin D and calcium intake is considerably lower
than in a country such as Sweden, as seen in table 8:8. However,
the consumption is not lower than in other parts of Japan where
Itai-itai disease is not seen. As we have said before, the weath
er in this part of Japan is very gloomy, with a lot of rain and
snow. The women also wear their clothes in such a manner that
the main part of the sunlight is screened away. Osteomalacia
and rickets have also been more frequently seen in the Toyama
Prefecture than in other parts of Japan (Kajikawa et al., 1957).
The dietary conditions can not explain the etiology of the dis-
ease, because conditi'ons are similar in nearby villages and
towns where the disease has not been found, but might be sub-
sidiary factors for the elicitation of the disease.

6.5.2  Malabsorption syndrome
Osteomalacia can also be caused by a deficient absorption of
Vitamin D and bone minerals. Chronic pancreatic disease, hepato-
biliary disease and resection of parts of the gastrointestinal
tract have given rise to such osteomalacia, as reviewed by
Arnstein, Frame and Frost, 1967, Bostrom, 1967 and Muldowney,
1969. In this context, the clinical observations reported by
Murata et al., 1970, concerning the function of the gastroin-
testinal tract and pancreas are of interest. In his 1970 paper
Murata mentioned that he had detected a tendency toward a de-
clined function of the pancreas in many cases. Furthermore,
examinations of the gastrointestinal tract have shown short-

ened ciliated epithelia as well as atrophy of the mucous mem-
brane and submucosal cell infiltration in the small intestine.
Fat absorption tests have shown decreased fat absorption in
many cases. These changes in the gastrointestinal tract have
been called "cadmium enteropathy" by Murata. At the present,
it is impossible to judge how frequent these changes are.
Murata did not state information about frequency. However, in
cases in which changes are present, they could act as a con-
tributory etiological factor of the Itai-itai disease.

j.5.3  So-called Vitamin D resistant osteomalacia jrenal osteomalacia)
This form of osteomalacia is caused by a renal tubular dysfunc-
tion which gives rise to losses of bone minerals, primarily
phosphate, through the kidneys. Hereditary forms have been de-
scribed by Dent, 1956, but a Fanconi syndrome caused by toxic
substances such as heavy metals can produce the same defect.
Persons with the Itai-itai disease always have proteinuria of
a tubular type. There is also an increased excretion of amino
acids and glucose. The osteomalacia seen in Itai-itai patients
is mainly of the same nature as hereditary forms but no hered-
itary factor has been found.

6.5.4  Cadmium as an etiological factor
It has been well established (Chapter 6) that exposure to cad-
mium can give rise to tubular damage of the kidneys with pro-
teinuria and glucosuria. The kidney damage seen in Itai-itai
disease has been very similar to that seen in classical indus-
trial chronic cadmium poisoning,.but bone changes have not been
a common finding in the latter condition. There are, however,
two French accounts by Nicaud, Lafitte, and Gros, 1942, and
Gervais and Delpech, 1963, and two British studies by Bonnell,
1955, and Adams, Harrison and Scott, 1969, which, taken togeth-
er, show that both in male and female workers occupationally

exposed to cadmium, bone changes similar to those seen in Itai-
itai disease have occurred (section 6.4).

Data from industrial exposure refer mostly to males, while al-
most all of the Itai-itai patients have been females. It should
be stressed, however, that in the endemic area, the prevalence
of proteinuria and glucosuria has been extremely high also in
males and only slightly lower than in females. Thus, if cadmium
is the cause of the disease,  there is no pronounced difference
in the prevalence of functional disturbances, but only in mani-
festations. When tubular dysfunction disturbs the metabolism of
calcium and phosphorus, women will be affected more than men.
This is particularly the case in the women involved who were
multiparas and who lived in an area with a low intake of calcium
and probably also of Vitamin D. Therefore, it is not contradictory
to a cadmium etiology that almost exclusively females have suffer-
ed from bone changes.

Although no data exist concerning the cadmium exposure several
years ago, when it was supposedly highest, available information
on cadmium concentrations in rice and paddy fields from recent
years has shown a close correlation between high cadmium concen-
trations and the occurrence of Itai-itai. Furthermore, an associa-
tion between cadmium concentration and the prevalence of protein-
uria and glucosuria has been shown in the endemic area as well
as in another area, Tsushima Island. This area has been selected
by the Japanese government for detailed studies on suspected cad-
mium intoxication.

The question remains whether or not the cadmium exposure has been
high enough to cause intoxication. This question can be approached
in two different ways. One can evaluate the exposure either from
data on cadmium concentrations in biological material <5r from

.data  on  exposure  via  food, water  and  air  together with  esti-
mations  of  absorption and  excretion rates.

Data  on  cadmium concentrations  in  biological materials  are avail-
able  only on  a limited  basis. Blood and urinary values  have
shown an increased  amount  of  cadmium  but  do not lend themselves
to a  quantitative evaluation  of risks. However, a few data on
cadmium  concentrations  in  organs  from deceased Itai-itai patients
have  shown  values for liver and pancreas  quite comparable with
those found in workers  with symptoms  of chronic cadmium poison-
ing.  The liver values are  about 50 times  higher than in people
in the United States,  the  United  Kingdom  and Sweden, not occu-
pationally  exposed  and  also considerably  higher than the average
in "control groups" in  Japan. Cadmium concentrations in kidney
are low, in fact, somewhat lower  than in  the "control groups"
from  Japan. There is  all reason to believe that these low values
are consistent with a pronounced  kidney damage in the Itai-itai
patients as discussed earlier in  this report.

As has been mentioned,  exposure data  from several years ago
are not  available.  Yamagata and Shigematsu, 1970, calculated
the daily intake  of cadmium during recent years in the  endemic
area  as  600 tig, making  200 mg per  year.

In section  it was  concluded that  a critical  level in
renal cortex  for  renal tubular dysfunction could be  estimated
to 200 ppm  (wet weight) of cadmium. In the same section it was
discussed which cadmium exposure  that is  necessary,  via the
peroral  route, to give  rise to  this kidney level under diffe-
rent  assumptions  concerning absorption rates of cadmium.
Table 6:2 gives data  on the necessary exposure for different
exposure times as well  as  for assumed absorptions of 2.5, 5
and 10 percent. As  can  be  seen  in  this table, 600 tig cadmium

per day may cause ranal dysfunction after only a few years
with a 10 percent absorption of cadmium. With an assumed ab-
sorption of 5 percent it would take about 10 years and with a
2.5 percent absorption about 20 years. There could thus be no
doubt that the cadmium exposure in the endemic area, even now,
is quite sufficient to cause renal damage, especially as the
estimations are based on a body weight of 70 kg. This weight
is well above the average body weight in the endemic area. One
does not have to postulate that the exposure in the past must
have been higher, even if this probably has been the case, in
order to explain the renal dysfunction. We do not know exactly
how severe the renal damage must have been to cause osteomalacia.
It seems quite clear, however, that possibilities of. a very high
absorption during long times have existed.

In conclusion, nothing essential has spoken against cadmium as
the etiological environmental agent causing the Itai-itai dis-
ease.  Since in fact, all available data strongly support a
hypothesis that cadmium is the cause, we have no doubts that
the Itai-itai disease is a manifestation of chronic cadmium
poisoning. It might well be, however, that cadmium has acted
upon a population particularly sensitive because of deficient
consumption of certain essential food ingredients and vitamins.
A low intake of calcium and Vitamin D may have been of particu-
lar importance.

It should be emphasized that the Itai-itai disease is only one
manifestation of chronic cadmium poisoning. The high prevalence
of proteinuria and glucosuria without bone changes in the en-
demic area certainly is a manifestation of chronic cadmium poi-
soning. There is every reason to believe that cadmium intoxica-
tion has occurred in other parts of Japan than the Toyama Pre-

fecture. Data from the Tsushima Island strongly support such
a hypothesis. It is impossible to estimate quantitatively the
extent of the cadmium problem in Japan solely on the basis of
available data. Because cadmium is used extensively in industry,
in mining and smelting operations which are common in Japan,
the cadmium problem may well be far-reaching. Only additional
epidamiological studies in potentially exposed areas can eluci-
date that question.


           1962-1965 epidemiological research.  Women over

           40 years of age.  Also men over 40  years  of age

           in Tonami City  (from Ishizaki and Fukushima,



Kumano, Fuchumachi
Shinbo, Toyama City
Ota, Toyama City
Tonami City

xNumber of
i (
 Decided mainly by X-ray
  Jintsu River basin
 I:    Patient  (typical bone
      signs  on  X-ray)

(I):  -Person cured  of Itai-
      itai  disease

 i:    Deeply suspected (bone
      signs  but  not  typical)

 (i):  Suspected  (bone signs,


            1967 EPIDEMIOLOGICAL STUDY  (from Kato  and Kono,

 Please answer all of the following questions.  Try to overcome  any
 difficulties you might have in recalling the answers,  "yes"  or

 1.   Have you ever been told that you are an
     Itai-itai patient?

 2.   Have you ever suffered from neuralgia or

 3.   Have you ever suffered from a bone or
     joint disease?

 4.   Have you ever suffered from a low back

 5.   Have you ever suffered from a kidney

 6.   Have you ever suffered from diabetes?

 7.   Do you have a low back pain now?

 8.   Do you have an arm, leg, or foot pain

 9.   Do you have a joint pain now?

10.   D° you have neuralgia now?

11.   Have you difficulty walking now?

12.   Have any of your family members (father,
     mother, brother, sister, husband, wife,
     or children) died of Itai-itai disease?

13.   Have any of your family members died
     of kidney diesase?

14.   Have any of your family members died of
     diabetes ?

15.   Have any of your family members suffered
     from rickets?
                                                  Yes         No

           (from Ishizaki  and Fukushima,  1968).

Fuchumach i
^ Toyama City
"{jj Osawano-cho
< 60-74
75 +
Mean age:
I: Patient
i : Deeply s
(i ) : Suspecte
0 .:' Need for
0 blood si
0: No suspi

d (bone s
bone si
(bone s
igns. s
- .
gns on
igns but not
continuous observation
gns )

( uri

typical )


nary and/or

                  1968 (from Kubota et al., 1969).
°ob   Total
Age hale Fern.
40-49 2
50-59 6
60-69 31
70-79 12
80-89 2
Total 53

1 6
1 27





3 14
12 40
14 30
3 5
32 91


3 22
12 90
14 53
4 14
33 184



For explanation of symbols for the Itai-itai classification,
see table 8:3.

           COMPLAINTS (patients registered by Toyama Prefecture,
           June 15, 1968)
           (from Kato and Kono, 1968).

Total 92 6
XI 51 4
i*(i) 41 2
Starting year
 For explanation of symbols for the Itai-itai classification,
 see table B:3.

           Men and women  in different  districts  and  in  different  age
           groups at the  1967  epidemiological  study   (Ishizaki,
           personal communication).
Age group 30- 40- 50- 60- 70-
39 49 59 69
district 394 382 291 255 160
district 97 95 73 66 32
district 306 220 202 17B 85
Total 797 697 566 499 277
Total 30- 40- 50- 60- 70- Total
39 49 59 69
1482 503 392 352 289 134 1670
363 109 99 95 78 47 428
991 349 245 265 184 116 1159
2836 961 736 712 551 297 3257

Table 8:7
al., 1967).

Age at
(years )

70 *

Posi ti ve
(percent )
Hi roshima
Number •

Posi ti ve
(percent )

3. 1
70 *


                   (Japanese data for 1955 and 1956 from
                    Takase et al., 1967, or Tsuchiya, 1969;
                    Swedish data for 1960 from Blix et al.,

P ro t e i n
Vit. A
Vit. B1
Vit. B2
Vit. C
Vit. D

(I.U. )
Itai- i tai
Patients '
Homes x

2. 139



i n
( Toyama
Pref. )



1. 1


5. 1
Total: 200 households


           PATIENTS AND CONTROLS (Ishizaki, personal

Factors studied
Itai-itai    Controls
(124 women,  (124 women,
 3 men, mean  3 men, mean
 age:67.6)    age:66.3)

1. Lived in same area
   40 years or more          96

2. Worked in agriculture     83

3. Six or more preg-
   nancies                   56
4. Drank water from
   Jintsu River              83

5. Total family income
   1,000,000 yen or more     15

6, "Better" condition of
   living room               61

7. Refrigerator in house     56

8. Area of rice field
   (mean)                    1 hectar








              1 hectar
 'Difference statistically significant

      Table 8:10  CADMIUM CONTENT (ppm. wet weight) IN
                  (from Ishizaki, Fukushima, and
                   Sakamoto, I970b).
Organ Patient 1
age: 79
Liver 94.1
Renal cortex 41.1
Renal medulla 39.5
Pancreas 45 . 1
Small intestine
Large intestine
Bone cortex
Bone marrow
Brain 0.6
Patient 2
age: 71
31 .8


1. 1

Patient 3
age: 60
19. 8X


11 .9


Patient 4
age: 73




Cortex and medulla not separated

            CROUPS (fron Departoent of Health, Nagasaki Prefecture, 1770)






Total of
Area under Obser-
Total of
Control Area

Nuaber at Risk
Number Examined
Percentage Examined
Nunber at Risk
Number Er.amlned
Percentage Examined
Number at Risk
Number Examined
Percentage Examined
lluaber at Risk
Nunber E::aained
Percentage Examined
Number at Risk
Hunbcr Examined
Percentage Examined
Nuaber at Risk
Dumber Examined
Percentage Examined
Number at Risk
Nunber Examined
Percentage Exaained
Hunbcr at Risk
Number Examined
Percentage Exaained
31 •
F e
' 5

            (from Department of Health,  Nagasaki
             Prefecture,  1970).


Kashine, Shiine
Shimobaru, Komoda
Hikage-Kamiyama, Are
Number Percent
Examined with
P ro t e i n -

73 14
99 3
46 0



Glucos -

Number Percent
Examined with
P ro t e i n -

96 14
101 5
107 6


P ro t e i n -
uri a

            numbers) IN DIFFERENT AREAS (from Department of
            Health, Nagasaki Prefecture, 1970).

Age :
Kashine, Shiine
Shimobaru, Komoda
Hikage-Kamiyama, Are
60- 70-
15 7
16 11
14 3
60- 70-
14 17
17 10
26 6

            IN FARMERS (from Department of Health,
            Nagasaki Prefecture,  1970).


Kashine, Shiine
Shimobaru, Komoda
Hikage-Kamiyama, Are
Number Percent
Examined with

30 20
29 10
23 0




Number Percent
Examined with
P ro t e i n -

65 18
47 4
71 6



Table 8:15  CONTENT OF CADMIUN IN SELF-STORED RICE (ppm dry weight)
            AND BEAN PASTE (ppm wet weight) IN
            Association of Public Health,  1970b).

Average Range
Sasu-Shiine basin
Areas under observation
Hikage and Kamiyama
Control area (Are)
Namari -Nihazama basin
Areas under observation
Control area
Usui-Yanase basin
Areas under observation
Naka j uku
Control area
Okudake basin
Areas under observation
Sanchi -Ts udome
Control area











. 14








                 (ppm, wet weight)
                 (from Department of Health, Nagasaki Prefecture; 1970)

Control area
Observation area
(Kashine, Shiine,-
Shimobaru, Komoda,
Wa terms Ion
Mush room

                      TOYAMA BAY
Figure 8:1
Location of Population  Centers within Toyama
Prefecture, with the  location of  the Kamioka
mine (from IshizaKi  and Fukushima,  1968).

normal 2.5
        Inorganic P.
               Bodansky unit
              Ca        Al. ph ase
          (in Serum)
  Figure 8:2  Inorganic  Phosphorus, Calcium and Alkaline
              Phosphatase  in Srrurn of Patients with Itai-itai
              Disease   ( rron^ ""-jrata et al.,  1970).

                                            Urine protein
                                            870mg/g creatlnlne
                               Urine protein
                               1400 mg/g creatlnine
                                            Urine protein
                                            960mg/g creatlnlne
                               Urine protein
                               1540 mg/g creatinlne
                                            Urine protein
                                            700mg/g creatlnlne
                               Urine protein
                               1180mg/g creatlnlne
                            Alb. *i   «*2   /*    ¥   *•

                   1. Male  Japanese worker occupallonally
                     exposed to cadmium oiide fumes.

               2 and 3. Men  from the endemic  district  with
                     proteinuria  and  glucosurla without
                     bone changes.
gure 6:4  Qisc-elactrophoretic  Patterns of Urinary Proteins from A) 19 Year-old Man with
          Nephrotic Syndrome,   8)  22  Year-old Cadmium Exposed Worker,  C) 67 Year-old Woman
          with Itai-itai  Disease,   D)  74 Year-old Woman with Proteinuria and Glucosuria. but
          without Bone  Disease,  Living in the Endemic Area for the Itai-itai Disease (from
          Piscator and  Tsuchiya,  unpublished data).

             A. Screening rank from urine analysis
                       Protein  (mg/dl)
          0   ±   10  20  30  40  50  60  70  80  90  100
     to second exam.
   The subject whose rank is 1 in either A or B —
   The subject whose rank number in total A * B is less than
   5 	» to second.
Figure 8:5
Selection of Subjects for the Second Examination
from the Results of Urine Analysis and Ouestionnaire~
(from Kato and Kono, 1968).

r J>
. i
• i
i i
/ A

     m  20-
     *g  10-19
     '///,   1-  9
Figure  6:6
Percentage of Women over 50  Years of Age with
Itai-itai Disease (I,  i,  or  (i) ) at the Examination
of 1967   (from Ishizaki  and  Fukushima, 1968, Kato
and Kono. 1986, or Yamagata  and Shigematsu,  1970).



            Irrigation water from Jintsu Riv.

                 "               Tributaries
Figure 8:7
Distribution of Cd in Paddy  Soil,  Surface  Layer
(from Kato and Kono,  1968, or Yamagata  and
Shigematsu,  1970).

             60 -\
                 30  40  50 60  70   30 40 50 60 70 years old
                 30 40 50 60 70   30 40  50  60  70 years old
                     •• Endemic district
                C	O Border district
                X	.X Non endemic district
Figure  6:8
Prevalence  of Protsinuria  (above)  and Glucosuria  (below)
in Different  Districts in  Men  and  Women in Different
Age Groups  at the 1967 Epidemiological Study
(from Ishizaki .  1969b).

                          • —o
              30   40    50    60    70  years old
             Women,  endemic  area
             Men,  endemic  area
             Women,  non- endemic  area
             Men,  non-endemic  area
Figure  8:9
Concurrent  Prevalence of Proteinuria  and Glucosuria
in Endemic  and Non-endemic Districts  in Men and
Women in  Different Age Groups at the  1967
Epidemiological Study (modified from  Ishizaki. 1969b).







               30   40,  50   60   70 years old
                • •  •  Women  born in endemic  area
                        and still  living there

                0--0--0  Women  born in another  area
                        but living in endemic  area
                        at least 20 years (since
                        1945 or earlier)
Figure  8:10  Concurrent Prevalence of Proteinuria and Glucosuria
            in  Women in Different Age Groups  in the Endemic
            District According to Place  Born   (Fukushima,
            personal communication).

                                Women   Men
****** * *o •
* 8 e
1 l1*^)! ,00b ° 1 °ob 1 ° i
Endemic area Slightly
* S. D.

°obl 0
^ V '
Non endemic
area in Toyama
Figure 8:11
           Cadmium Concentration in Urine of Persons  from
           Different Areas in Toyama Prefecture  (from
           Ishizaki, 1969b).

            120 H
                20     40    60     80    years old

                   6      8     17      7 number examined
Figure 8:12    Cadmium Content (ppm wet weight)  in  Controls
               who  died in hospitals in Kanazawa   (from
               Ishizaki,  Fukushima, and GaKamnto,  1970b).

    Remarks:  Circle:  nine
              Triangle: Smelting  works
              Oval:  District "to  be
         Jintsu  Riv.Basin, Toyama  Pref

         Kurihara-gun.  Miyagi Pref.

         Annaka  City.  Gunma Pref.
         Tsushima Is.,  Nagasaki Pref.
      5. Okudake  Riv.Basin, Ooita  Pref.
Figure b: 1 3
:'!.ir. tH but. ion  of 'Jiil fin i elf  i.'rer.  (Cu, Pl>, Zn)  and
CimcH. i nj-.  WorK::  in ."la pan   (from Ycim/.H-ot. n
:.ihi pir.ii.;jtsijf 1970).

                                                       j KAMIYAMA
   O- MINE
         0:14    Area  unrk»r  IOV/RT I. isation .  Tsushima  Island   (from
                 report;  by tho  Department of Una 11;h,
                 Prnfnature,  1rJ/!"!).





                  40   50  60   70
                          40   50  60   70 years old
 Kashine. Shilne

 Hikage-Kamiyama, Are  #	x

 Shimobaru.  Komoda     o—	o
                  No cases of proteinuria found among males
Figure  8:15
Prevalence of  Proteinuria in  Different  Areas  in
Men and Women  in Different Age  Groups   (from
report  by Department  of Health,  Nagasaki Prefecture,




                u   20   40                0   20   40 years
                                Residential  period

                Kashine, Shline        •	•

              x j
                Hikage-Kamiyama, Are   *.— ._*

                Shimobaru, Komoda      O——-o
                No cases of proteinuria found among males
Figure  8:16
Prevalence of Proteinuria in  Different  Areas
(Tsushima Island)  in Men and  Women in Relation
to Time  of Residence  (from a report by the
Department of Health.  Nagasaki  Prefecture.  1970)

   Urine Cd,/jg I.
                           Shimobaru    Are
Figure 8:17
Urinary Cadmium Concentration of Subjects  from
Different Areas of  Tsushima Island Positive  for
Urinary Protein and/or Glucose  (from report  by
Department of  Health,  Nagasaki  Precfecture,

Figure 8:18 Advanced Skeletal Deformities in Itai
            itai Patient (from Murata,  personal


Figure 8:19 Itai-itai Patient with Multiple Pseu-
            do-fractures of the Ribs (from Murata,
            personal communication).

                         CHAPTER 9


                    NEED FOR FURTHER RESEARCH
In the proceeding chapters a detailed review of the different
aspects of cadmium intoxication has been given. In each chapter
whenever motivated there are special sections for conclusions
drawn and these will not generally be repeated here. This chap-
ter,  instead, will deal with more general aspects on the problem,
pointing out some of the most important conclusions, and empha-
sizing the need for further studies.
Cadmium can undoubtedly constitute a most serious health problem.
There is much evidence that exposure to this metal in the environ-
ment, both the industrial and the general environment, has given
rise to serious intoxications in human beings. Such effects have
been shown from inhaled as well as from ingested cadmium.

The manifestations of cadmium, intoxication can take several forms
Inhalation of cadmium oxide fumes can produce acute damage in
the lungs in the form of pneumonitis or pulmonary oedema. Pro-
longed exposure to dust or fumes can cause an invalidating em-

Although dose-response relationships are generally uncertain,
it was concluded (Chapter 5) that an exposure to about 500 min.
mg/m  of cadmium oxide fumes is immediately dangerous from the
point of view of acute pulmonary manifestations. Chronic exposure

to cadmium oxide fumes, in concentrations well below 0.1 mg/m ,
is  considered hazardous with reference to emphysema.

Systemic effects arise after absorption of cadmium. With the
exposure that occurs from the general environment and also in-
dustrially, it is the effects due to long-term exposure to low
concentrations of cadmium that are of interest. The critical
organ is the kidney. Renal tubular dysfunction with proteinuria
is a common manifestation. The renal tubular dysfunction may
under certain circumstances give rise to severe secondary mani-
festations including a pronounced and invalidating osteomalacia.
This form of cadmium intoxication has been seen industrially
after inhalation of cadmium as well as after long-term ingestion
of contaminated food. Other systemic effects include anemia and
liver dysfunction.

In Japan the fully developed picture of cadmium intoxication
with kidney damage and osteomalacia is known under the name
"Itai-itai byo" (literally: ouch-ouch disease) because of the
severe pains accompanying the skeletal disorder. A large number
of cases of cadmium intoxication with renal dysfunction but without
known osteomalacia are also reported from Japan. Contamination
of the food, particularly rice, with cadmium is considered to be
the main cause of this disorder. The contamination of the food
has with all probability its primary cause in contaminated river
water and in some places perhaps also in the contaminated ambient
air. The reason why the manifestations of cadmium intoxication in
Japan often have come to such a.n advanced stage is not quite clear.
It may be that the exposure several years ago was very excessive,
but there is also the possibility that poor nutritional habits,
such as low intake of calcium, protein and Vitamin D have been
essential to the problem.

In some animal experiments it has been possible to produce
hyperten.sion after prolonged exposure to cadmium. There is no
conclusive evidence that cardiovascular disease in human beings
is causally associated with cadmium exposure, although some
statistical associations found in epidemiological studies merit
further investigations.

Animal experiments have clearly shown that injections of cadmium
salts cause malignancies. There are some data from human beings
which tend to show an association between cadmium exposure and
cancer. However, much more evidence is needed before any con-
clusions can be made concerning this causality.

The nature of the effects of cadmium on the cellular level has
been discussed in several sections of the report and the intimate
relationship between cadmium and zinc metabolism has been pointed
out.  There are mechanisms which are fairly well known, but much
needs to be done until the complete picture of the different mani-
festations of cadmium intoxications are understood.
What makes cadmium contamination of the environment a particularly
serious hazard is the pronounced tendency for cadmium to accumu-
late in the body. This is evident from autopsy data on human beings
as well as from animal studies. Animal experiments show that the
excretion of cadmium via urine and the gastrointestinal tract is
extremely low, only a few percent of the absorbed amount. This
in turn is reflected in a very long biological half-life of seve-
ral hundred days. In human beings the excretion via urine has
been shown to be very low, while data on gastrointestinal ex-
cretion are lacking.

Daily, human beings are exposed to a substantial amount of cad-
mium in food. Fortunately the absorption rate seems to be low.
Some data on known accumulation of cadmium in the human body
and estimated cadmium intake in the past, tend to show a re-
tention of about 5 percent for human beings not excessively
exposed to cadmium.  Based on animal and human data, it is con-
sidered quite possible that under certain circumstances absorp-
tion in human beings may reach 10 percent (section

The ambient air contains small amounts of cadmium and in the
vicinity of certain factories the concentration can be consid-
erable. High exposure is not uncommon in industries where cad-
mium is used.  Absorption rate via inhalation is probably higher,
than via ingestion. Depending on factors like particle size, ab-
sorption rates of  10-40 percent have been estimated (section Also absorption via inhalation is subject to consider-
able uncertainty.

When absorbed, cadmium will accumulate in liver and kidneys.
The larger the exposure, the more will be accumulated in the
liver relative to  other organs. Long-term exposure to fairly
small amounts of cadmium will give kidney values corresponding
to about one third of the total body burden. When kidney damage
occurs, the concentration of cadmium in  the kidneys will decrease
substantially. This probably explains why advanced cases of cad-
mium intoxication, as seen in the Itai-itai disease and sometimes
in industrial poisoning, will have low kidney levels in spite
of high liver levels of cadmium.

When renal tubular dysfunction appears,  the excretion of cadmium
via the urine will increase drastically. Animal experiments have

shown an increase of about 100 times. The fact that urinary
cadmium excretion is virtually non-existent before renal dys-
function appears, makes tho analysis of cadmium in urine use-
less as an indicator of total body burden. But if the purpose
only is to detect cadmium induced renal dysfunction,  it may be
used, since increased cadmium excretion would point very strong-
ly towards such an effect.

Cadmium levels in blood will increase with exposure.  During
exposure,  though, it is not a good indicator of the body burden
as blood levels also will reflect recent exposure to cadmium.

As was stated above, at long-term exposure to fairly low con-
centrations of cadmium, about one third of the cadmium will be
found in the kidneys. Animal data as well as data from autopsies
of workers with none or only a slight renal dysfunction, point
towards 200 ppm (wet weight) of cadmium in the renal cortex as
being the  critical level for renal dysfunction, diagnosed through
kidney function tests and occurrence of proteinuria.  Based on
this level and absorption and excretion data for cadmium, estimates
have been  made of exposures that are necessary to reach the cri-
tical concentration of cadmium in the kidneys. Table 6:2 gives
examples of exposures and exposure times necessary to reach
200 ppm in the renal cortex. As can be seen from the table, a
daily intake of about 100-150 ug of cadmium will result in about
200 ppm of cadmium in the renal cortex after 50 years of exposure
with an absorption rate of 5 percent. Based on an absorption of
25 percent of inhaled cadmium, a mean concentration in the ambient
air of about 1-1.5 ug/m  will give the same result. A worker ex-
posed to cadmium industrially could expect to reach the critical
level after an exposure to about 8 ug/m  after approximately 25
years of exposure. In these estimations simultaneous exposure

via food and air has not been taken into account.

At birth, the human body only contains a total of about 1 ug
of cadmium. At the age of about 50 years, a "normal" body bur-
den of cadmium for an American "standard man" is about 30 mg.
Concentrations in food and air, necessary to reach this body
burden can be seen from data in table 6:3.

Ths following can be said concerning the needs for further
research. There is an immediate and urgent need for research
on the dose-response relationships. Above all, absorption and
excretion rates should be further  investigated. Such studies
should include exposure via the peroral route as well as in-
halation. Different cadmium compounds should be studied with
reference to the influence of particle size at absorption via
inhalation. The information on absorption to date is very
inadequate and it goes without saying, that preventive measures,
that need to be taken, may be quite different for different ab-
sorption rates. Animal experiments can certainly provide a
substantial part of the necessary  information. On human beings
it should be possible to carry out metabolic studies where up-
take and excretion of cadmium is examined over prolonged periods.

There is a need for more detailed  studies on concentrations of
cadmium relative to total body burden at different exposure
levels in kidneys, but also in other organs.

A search for better indicators of  cadmium levels in critical
organs other than those of urine and blood concentrations should
be pursued. Of special interest in this connection is hair.

The critical level in kidneys should be studied further. It
should also be born in mind that effect levels used up until

now have included only fairly gross effects. Dysfunctions may
be found at considerably lower concentrations on a cellular

Epidemiological studios should be carried out on populations
exposed in different degrees to cadmium. Such populations may
be found within industries, but also in areas surrounding in-
dustries emitting cadmium. The unfortunate wide-scale contami-
nation with cadmium in Japan may give unique possibilities for
studies in that country on several aspects of dose-response re-
lationships. When embarking on epidemiological studies due atten-
tion must be paid to methodological questions in order to make
results from different studies comparable. Effects to be looked
for  should include renal dysfunction including proteinuria,
certain cardiovascular diseases, and malignancies. The accumu-
lation of cadmium in the body should be studied further in con-
nection with autopsies in cases of accidental death as well as
from other causes, particularly cancer and chronic renal, cardio-
vascular and pulmonary diseases.

High concentrations of cadmium have been found not only in the
kidneys. The significance of an accumulation of cadmium in liver,
pancreas and thyroid certainly merits further studies.

Virtually nothing is known about genetic and teratogenic effects
of cadmium. There is a great nee'd for studies in these areas.

Chelating agents found extensively in nature may have a dele-
terious effect in cadmium intoxication. There is an immediate
need to examine the combined effects of cadmium and such agents
(e.g. EDTA and NTA) in long-term studies.

It should be emphasized that there are severe gaps in the
understanding of the mechanisms behind the different manifes-
tations of cadmium intoxication. Much of our present know-
ledge of cadmium intoxication is based on studies on the meta-
bolism of the metal. By stimulating further basic research on
metal toxicology we can expect to get a better understanding of
the complex effects of cadmium on human health.

Finally, it should be stressed that vast research needs exist
concerning aspects of cadmium in the environment which indirectly
are important for toxicological and epiderniological appraisals
of cadmium. Although not directly within the scope of this review,
it should be mentioned that there is a need for more data on the
turnover of cadmium in nature, including the accumulation via air
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