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EC number: 244-168-5
CAS number: 21041-95-2
data – establishing the dataset
A significant amount of data is available on Cd toxicity to soil or
litter microflora, soil fauna and higher plants in the EU risk
assessment (RA; ECB 2008). The quality and relevancy of those data have
been reviewed in detail during the EU risk assessment process.
Reliability indices 1, 2 and 3 (RI 1, RI 2 and RI 3) data were used in
the PNEC derivation, while reliability 4 data were excluded. Because the
RI 1 and 2 data group has limited number of species, the RA has proposed
to include the reliability 3 data too as basis for deriving the PNEC.
This is mainly due toplant data that are excluded from the group
RI 1-2, whereas plants seem to be the most sensitive group.For
the present analysis, the same approach was followed, to be conform with
the EU RA. Moreover, studies assigned RI 3 are still quite well
documented and therefore be considered reliable.
In this assessment, an update of the literature was made and new
toxicity data for Cd in soil were found useful to be added to the
dataset. Reliability was reviewed based on the same reliability indices
as those in the RA and using the same criteria.For each test, a RI
was given according to the following criteria (RA, ECB 2008):
RI 1: standard test, including the OECD 207
acute toxicity test withEisenia fetidain OECD-soil and the ISO
1994: soil quality effects of soil pollutants on Collembolla (Folsomia
candida): method for the determination of effects on reproduction.
RI 2: no standard test but complete background information is
given, i.e. the following information is present:
organic matter or carbon content
(class or texture fractions)
Cd content of the soil at zero Cd application if the NOEC or LOEC value
is below 2mg/g
time after soil contamination and prior to the test
analysis of the dose-response relationship
varying metal contamination along with increasing Cd application
control soil must be tested along with at least two Cd concentrations
above the background concentration
soil must be homogeneously mixed with the metal prior to the test
no standard test and one or more of the following information from the
above-mentioned list is missing as background information: b), c), e) or
f). All other information from that list is present.
no standard test and one or more of the following information from the
above-mentioned list is missing as background information: a), d), g),
h) or i). The requirement d) is critical since some tests reporting LOEC
values < 2mg/g
are considered unreliable. Background Cd concentrations in soil
typically range between 0.1 and 0.5mg/g
and the lack of reporting the background concentration may underestimate
the total Cd concentration in soil at which the first toxic effects are
found. Unbounded NOECs were not used. Tests performed in substrates that
were judged as not representative for soils (e.g. pure quartz sand or
farmyard manure) were not included in this effects assessment.
toxicity literature for cadmium was also checked according to the
general criteria for data quality:
endpoints, which may affect the species at the population level, are
taken into account. In general, these endpoints are survival, growth and
for one species, several NOEC values on the same endpoint are available,
the geometric mean of the NOEC values was first calculated and the most
sensitive endpoint was taken forward in the SSD for PNEC derivation.
the results of tests in which the organisms were exposed to cadmium
alone were used, thus excluding tests with metal mixtures.
in the RA, unbounded NOEC values were not used in the assessment.
in the RA, only the results of tests with soluble Cd2+ salts were used.
NOECs used are reported as nominal values and were taken as such for the
PNEC derivation. No correction for natural background was thus applied.
From the present revision of the terrestrial dataset, four new species
of macro-organisms were found to respond to the criteria. Among them,
three additional arthropod species and one plant species were included,
allowing for a revision of the invertebrates + plants SSD. New data on
species already figuring in the RA – database were also considered and
species geometric mean NOEC values were recalculated based on new
information. A new HC5 “plants and invertebrates” could subsequently be
calculated (see Section 3).
data for Cd toxicity in soil
The available database of chronic terrestrial toxicity tests for
single-species with cadmium provides information on several species of
soil micro-organisms, invertebrates and plants. These species are
routinely utilized for assessing the toxicity of substances in spiked
soils and standard test protocols exist.
The microflora dataset of the RA contains 21 entries (12 tests on
respiration, 4 tests on N-cycle, 4 tests on soil enzymes and one test on
N2fixation). The individual NOEC values varied from 3.6 mg/kg
for the N2fixation endpoint up to 3000 mg/kg for respiration. No
new data on microflora was found in this update and the microflora
dataset from the RA remains thus unchanged. The microflora entries are
summarized in the table 1.
The invertebrates dataset now contains 9 species among which: four
species of annelids, one species of nematod and four species of
arthropods. The available data on macroinvertebrate organisms include
only long-term tests, from 21 to 294 days, which cover growth and
reproduction effects. Three new species of arthropods (Onychiurus
yodai, Sinella umesaoiandParonychiurus kimi) were added to
the RA-dataset with NOEC values for reproduction of 50, 25 and 25 mg
Cd/kg, respectively. A new NOEC value for growth of 12.5 mg Cd/kg was
also found for the annelidL. rubellusand two new NOEC values of
25 and 80 mg Cd/kg were found for the reproduction endpoint the collembolFolsomia
candida.Considering those new values, the endpoint reproduction
becomes the most sensitive endpoint forF. candida. Overall, the
individual NOEC values varied from 5 mg/kg for the annelidEisenia
foetidaup to 320 mg/kg forF. candida. The invertebrates
entries are summarized in the table 1.
The updated plants dataset provides information on 15 species, including
exposure times from 14 to 100 days and covering growth (length, weight,
biomass) and germination effects. As compared to the RA, one new species
was added to the dataset, i.e.Brassica campestrisL. cv.Chinensiswith
a NOEC for growth (biomass) and NOEC for germination of 25 and 100 mg
Cd/kg, respectively. New NOECs were found for the wheat seedling (Triticum
aestivum; NOEC root elongation of 20 mg Cd/kg), for the oat (Avena
sativa; NOEC biomass of 6.3 mg Cd/kg and NOEC germination of 25 mg
Cd/kg) and the lettuce (Lactuca sativa; NOEC biomass of 3.1 mg
Cd/kg and NOEC germination of 12.5 mg Cd/kg). The individual NOEC values
varied from 1.8 mg/kg for the speciesPicea sitchensisup to 100
mg/kg forB. campestris var. Chinensis. The plants entries are
summarized in the table 1.
The geometric mean NOEC values calculated for invertebrates and plants
on the most sensitive endpoint are reported in Table 1. NOECs of soil
microbial assays have not been averaged across soils because of the
intrinsic variability of the microbial population between soils.
Table 1: Summary table of species geometric mean NOECs for the most
sensitive endpoints of plants and invertebrates used in the SSD. New
species to the ones mentioned in the RA or species for which new
information was found are highlighted in bold. The newly added
individual NOECs are underlined in the last column.
Species geometric mean NOEC
Geometric mean of 10, 10
geometric mean of 150,12.5
Geometric mean of 10, 18
geometric mean of25, 80
geometric mean of6.3, 10, 10
geometric mean of 7.1, 20,20, 29
geometric mean of 2.5, 5, 10, 10, 10
geometric mean of 10 and 40
geometric mean of 2, 2.5,3.1, 3.2, 5, 5, 10, 10, 20, 20, 32, 40, 40
geometric mean of 32 and 80
Brassica campestris var. chinensis
geometric mean of 20, 20, 20, 40,‘40, 40, 40, 80
on the species sensitivity distribution (SSD)
As in the RA, the statistical extrapolation approach is proposed in the
PNEC derivation. We tested the lognormal distribution
in the statistical approach as default option using the RIVM program ETX
version 2.0. As in the RA (ECB, 2008), the HC5 is calculated for three
different scenarios of data selection. The first scenario is by using
microflora NOEC values only. The values were taken as such from the Cd
RA, as no new data were added to the dataset. The second scenario is
based on the use of the revised database for invertebrates and plants,
(going from 20 to 24 species). The third scenario is making use of the
whole terrestrial toxicity database, i.e. using data on microflora,
plants and invertebrate organisms, as applied to other RA on metals (Cu,
Ni) and recommended by the Scientific Committee for Health and
Environmental Risks (SCHER) for the zinc RA. The
statistics of the curve-fitting on the chronic NOEC data are summarized
in Table 02.
Table 02. Summary statistics for the SSD on chronic NOEC values for
cadmium in soil
HC5 at 50% (Lower estimate on HC5) mg Cd/kg
A-D test and significance level
K-S test and significance level
Using both the Anderson-Darling (A-D) and the Kolmogorov-Smirnov (K-S)
tests for normality, the lognormal distribution fits significantly at a
level of 1% for all tested scenarios.
The terrestrial data set is split in two groups: microbial
processes and soil invertebrates + higher plants. The endpoints for
microbial processes are relevant at the ecosystem functioning level,
while the endpoints for soil fauna and plants are relevant at the
species level. The principle of splitting the terrestrial data in two
groups is open to criticism: there is no scientific argument (e.g. field
validation) for either option. However, this approach was taken forward
in the Cd RA (ECB, 2008) and is therefore proposed in the present
assessment. As in the RA, the lowest NOEC selection approach was not
performed because such a selection would not yield a representative data
set for the terrestrial ecosystem (e.g. all clay soils would be
excluded). The HC5 for the microflora is lower than the HC5 for soil
fauna and plants. In conclusion, we propose to use the HC5 based on the
microflora data set for the PNEC derivation i.e.HC5microflora=
2.3 μg Cd/g d.w. This approach is in accordance with the Cd RA
(ECB, 2008) and results in the lowest of the three HC5 values following
from the three tested scenarios.
For the sake of comparison, if the assessment factor approach would be
applied, using the lowest NOEC divided by an assessment factor (AF) 10,
this would yield a PNEC soil of 1.8 µg g-1/AF10 or 0.18
µg/g. This value is within the range of cadmium background
concentrations in soils which typically range between 0.1 and 0.5 µg/g
(Cd RA, 2008).
the PNEC soil
The PNEC soil is set based on the lowest observed HC5 derived by
statistical extrapolation from the microflora data, i.e.2.3 µg Cd/kg
d.w. In the Cd RA, an AF 1 or 2 was considered.
The current analysis rather suggests using an AF1 on the HC5 to derive
the PNEC. It is noted that thePNECsoilbased on
secondary poisoning is of 0.9 µg Cd/g d;w., which is below
the proposed value. The latter value is therefore proposed and used for
PNECsoil in this analysis. This is in accordance with the Cd RA.
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