Documents\Palladium-contents. Pdf

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ACRONYMS AND ABBREVIATIONS
AAS
atomic absorption spectrometry
ATPase
adenosine triphosphatase
Bq
becquerel
Ci
curie (1 Ci = 3.7 × 10
10
 Bq)
DNA
deoxyribonucleic acid
EC
50
median effective concentration
EHC
Environmental Health Criteria monograph
FAO
Food and Agriculture Organization of the United
Nations
FEV
1
forced expiratory volume in 1 s
GF-AAS
graphite furnace atomic absorption spectrometry
IARC
International Agency for Research on Cancer
IC
50
median inhibitory concentration
ICP
inductively coupled plasma
ICP-AES
inductively coupled plasma atomic emission
spectrometry
ICP-MS
inductively coupled plasma mass spectrometry
ILO
International Labour Organization
IPCS
International Programme on Chemical Safety
JECFA
Joint FAO/WHO Expert Meeting on Food
Additives
JMPR
Joint FAO/WHO Meeting on Pesticide Residues
K
i
inhibition constant
LC
50
median lethal concentration
LD
50
median lethal dose
MELISA
memory lymphocyte immunostimulation assay
MMAD
mass median aerodynamic diameter
M S
mass spectrometry
MTT
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl
tetrazolium bromide
NBS
National Bureau of Standards (USA)

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NOAEL
no-observed-adverse-effect level
NOEC
no-observed-effect concentration
NOEL
no-observed-effect level
OECD
Organisation for Economic Co-operation and
Development
PGM
platinum group metal
PM
2.5
particulate matter with aerodynamic diameter
<2.5 µm
PM
10
particulate matter with aerodynamic diameter
<10 µm
RNA
ribonucleic acid
RO
Responsible Officer
SRM
Standard Reference Material
TC
50
concentration causing 50% toxicity
UN
United Nations
UNEP
United Nations Environment Programme
US
United States
UV
ultraviolet
WHO
World Health Organization

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1
1. SUMMARY
1.1 
Identity, physical and chemical properties and
analytical methods
Palladium is  a steel-white, ductile  metallic element resembling and
occurring with the other platinum group metals (PGMs) and nickel. It
exists in three states: Pd
0
 (metallic), Pd
2+
 and Pd
4+
. It can form organo-
metallic compounds, only  few of which have found industrial uses.
Palladium metal is stable in air and resistant to attack by most reagents
except aqua regia and nitric acid.
Currently, there are  no published measurement methods that dis-
tinguish between different species of soluble  or insoluble  palladium in
the environment. 
Commonly  used analytical methods for the quantification of palla-
dium compounds are  graphite furnace atomic  absorption spectrometry
and inductively coupled plasma  mass spectrometry, the latter having
the possibility of simultaneous multi-element analysis. 
1.2
Sources of human and environmental exposure
Palladium occurs together with the other PGMs at very  low con-
centrations (<1 µg/kg) in the Earth’s  crust. For industrial use, it is
recovered mostly  as  a by-product of nickel, platinum and other base
metal refining. Its separation from the PGMs depends upon the type of
ore in which it is found.
Economically  important sources exist in Russia, South Africa and
North America. The worldwide mining of palladium is  estimated to yield
about 260 tonnes/year.
Palladium and its  alloys are used as catalysts in the (petro)chemi-
cal and, above all, the automotive industries. Demand for palladium in
automobile  catalysts  rose from 24 tonnes  in 1993 to 139 tonnes  in 1998,
as  palladium-rich technology was  adopted in many gasoline-fuelled
cars. 

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EHC 226: Palladium
2
Applications for electronics  and electrical technology include u s e
in metallization processes (thick film paste), electrical contacts and
switching systems.
Palladium alloys are  also widely  used in dentistry  (e.g., for crowns
and bridges).
Quantitative data on emissions of palladium into the atmosphere,
hydrosphere  or geosphere  from natural or industrial sources  are  not
available.
Automobile  catalysts  are  mobile  sources  of palladium. Around
60% of European gasoline-fuelled cars sold in 1997 and also many
Japanese and US cars were equipped with palladium-containing cata-
lysts. Data on the exact palladium emission rate of cars equipped with
modern   monolithic   palladium/rhodium  three-way  catalysts   are   still
scarce.  The  particulate  palladium released from a new palladium-
containing catalyst ranged from 4 to 108 ng/km. These values  are  of the
same  order of magnitude as  previously  reported platinum emissions
from catalysts.
1.3
Environmental transport, distribution and
transformation
Most of the palladium in  the biosphere is in the form of the metal
or the metal oxides, which are  almost insoluble  in water, are  resistant to
most reactions in the biosphere (e.g., abiotic  degradation, ultraviolet
radiation, oxidation by hydroxyl radicals) and do not volatilize into air.
By  analogy to other PGMs, metallic palladium is  not expected to be
biologically transformable.
Under  appropriate  p H  and  redox  potential  condit ions, it is
assumed that peptides  or humic  or fulvic  acids bind palladium in the
aquatic  environment. Palladium has been found in  the ash of a number
of plants, leading to the suggestion that palladium is more environ-
mentally mobile and thus bioavailable to plants than is platinum.

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