Documents\Palladium-contents. Pdf

Summary
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1.4
Environmental levels and human exposure
In contrast to the large body of information concerning concen-
trations of metals  such as lead or nickel in the environment, there  is
little information on palladium. Concentrations of palladium in surface
water, where it is  detected, generally  range from 0.4 to 22 ng/litre (fresh
water) and from 19 to 70 pg/litre (salt water). Concentrations reported
in  soil  rang e  from  <0.7  to  47  µg/kg.  These  soil  samples   were   all
collected from areas near major roads.
Concentrations reported in sewage sludge range from 18 to
260 µg/kg, although a concentration of 4700 µg/kg has been reported
in  a  sludge  contaminated  by  discharges from the local jewellery
industry.  Drinking-water  samples   usually   contain   no  palladium  or
<24 ng palladium/litre. The few data available show that palladium can
be present in tissues of small aquatic invertebrates, different types of
meat, fish, bread and plants. 
The general population is primarily  exposed to palladium through
dental alloys, jewellery, food and emissions from automobile catalytic
converters. 
The human average dietary intake of palladium appears to be up
to 2 µg/day.
In  analogy  to  platinum, ambient air levels of palladium below
110 pg/m
3
 can be expected in urban areas  where  palladium catalysts  are
used. Therefore, the inhalative palladium uptake is very low. In road-
side dust, soil and grass samples, a slight accumulation of palladium
has  been detected, correlating with traffic  density and distance from
the road.
Oral exposure  in the general environment is very important and
may occur by daily direct contact of the gingiva with palladium dental
alloys. Skin exposure may occur by contact with jewellery containing
palladium.
Dental alloys are the most frequent cause of constant palladium
exposure. The corrosive behaviour of palladium-containing dental
alloys in the mouth can be influenced by the addition of other metals

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EHC 226: Palladium
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(such  as   copper, gallium and indium) and processing of the alloy.
Palladiu m–copper alloys with high copper content may be less
corrosion-resistant  than  palladium  alloys with low copper content.
Palladium release from palladium-containing dental restorations shows
substantial individual variation depending on the dental condition, the
material involved and personal habits  (e.g., gum chewing). Clinical data
for iatrogenic  exposure are of limited value, as the few case-studies
have methodological deficiencies, such as  limited numbers  of tissue
samples and poorly  matched control groups. It is, therefore, difficult to
make an accurate quantitative statement regarding daily  intake, and the
proposed value of 
#
1.5–15 µg palladium/day per person thus remains
a crude estimation.
There   is   some   informa tion on palladium levels in the general
population,  where   levels   in urine were in the range of 0.006–
<0.3 µg/litre in adults.
M o s t occupatio n al exposures  to palladium (salts) occur during
palladium refining and catalyst manufacture. There  are  few exposure
measurements, ranging from 0.4 to 11.6 µg/m³ as an 8-h time-weighted
average. No recent data are available for biological monitoring of
workers exposed to palladium and its salts.
Dental technicians may be exposed to peaks of palladium dust
during processing and polishing of dental casting alloys containing
palladium, especially if adequate protective measures (dust extraction
or aspiration techniques) are not taken.
1.5
Kinetics and metabolism in laboratory animals and
humans 
Only  few data are available on the kinetics of metallic or ionic
palladium.
Palladium(II)  chloride (PdCl
2
)  was   poorly   absorbed  from  the
digestive tract (<0.5% of the initial oral dose in adult rats or about 5%
in suckling rats after 3–4 days). Absorption/retention in adult  rats  was
higher following intratracheal or intravenous exposure, resulting in
total  body  burdens  of  5%  or  20%,  respectively, of the dose

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Summary
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administered, 40 days after dosing. Absorption after topical application
was observed but not quantified.
After  intravenous  administration  of  different palladium com-
pounds, palladium was  detected in several tissues of rats, rabbits  or
dogs. The highest concentrations were  found in kidney, liver, spleen,
lymph nodes, adrenal gland, lung and bone. For example, 8–21%  of the
administered  d o s e  of  palladium(II)  chloride  or  sodium  tetr a c h l o r o -
palladate(II) (Na
2
PdCl
4
) has  been found in the liver or kidney of rats
1  day  after  dosing. After a 4-week dietary administration of palla-
dium(II) oxide (PdO), measurable  levels  have been found only  in the
kidney of rats. 
Only  scarce data are  available  on the distribution of palladium
from dental restorations in human tissues or fluids (e.g., in serum and
saliva: about 1 µg/litre).
Transfer of small amounts of palladium to offspring via  placenta
a nd  milk  was   seen  with  single   intravenous  doses   of  palladiu m ( I I )
chloride in rats.
Information on the elimination and excretion of palladium is  scarce
and  refers   mostly   to  palladium(II) chloride and sodium tetra-
chloropalladate(II), which were  found to be eliminated in faeces  and
urine. Urinary excretion rates  of intravenously dosed rats and rabbits
ranged from 6.4 to 76% of the administered dose during 3 h to 7 days.
Elimination of palladium in faeces ranged in these studies from traces
to  13%  of  the  administered  dose.  Following  oral  administratio n   o f
palladium(II) chloride, >95% of palladium was  eliminated in faeces  of
rats  due to non-absorption. Subcutaneous or topical treatment with
palladium(II) sulfate (PdSO
4
) or other palladium compounds resulted in
detectable  concentrations of palladium in the urine of guinea-pigs and
rabbits.
Half-lives   calculated  for  the  elimination  of  palladium  from  rats
(whole body, liver, kidney) ranged from 5 to 12 days. 
Mean retention values  determined at three time intervals  (3 h, 24 h,
48 h) in rats injected intravenously with 
103
PdCl
2
 showed little change
with time for kidney, spleen, muscle, pancreas, thymus, brain  and bone.

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