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EC number: 231-845-5 | CAS number: 7758-95-4
The biota-to-soil accumulation factor (BSAF) for earthworms in soil is dependent on the effective cation exchange capacity (eCEC) of the soil:
log BSAF (kgdw/kgdw) = -0.89 * log eCEC (cmolc/kg) +0.55
For comparison with the PNECoral for birds and mammals, this BSAF must be expressed on a fresh weight basis. The conversion of dry weight to fresh weight is based on an average dry matter of 16% in earthworms (Jager 1998):
BSAF (kgdw/kgdw) = 0.16 * BSAF (kgdw/kgdw)
A generic BSAF factor of 0.048 (fresh weight) is derived for a soil with a median eCEC of 16 cmolc/kg soil. Fresh-weight based BSAF values for a soil with an eCEC of 8 and 30 cmolc/kg soil, corresponding to the 10thand 90thpercentile of eCEC in European arable soils are 0.089 and 0.028, respectively.
A wealth of data is available on biota-to-soil accumulation factors (BSAF) for Pb. A literature search has been performed in 2017 to assess the published BSAF. Data were considered reliable:
According to the REACH Guidance Document (Chapter R16), the food-chain soil, earthworms and earthworm eating predators is considered for risk characterisation purposes.
In total, 248 BSAF values for earthworms were identified that meet the reliability criteria, ranging from 0.01 to 22.05 kgdw/kgdw. The median BSAF for earthworms on a dry weight basis is 0.23 kgdw/kgdw(10-90thpercentiles are 0.06-1.19).
Results are available for several earthworm species, belonging to different ecological groups of earthworms: anecic, endogeic and epigeic earthworms. No distinct differences in BSAF values across these groups could be identified. Moreover, different species were sampled in different soils, which hampers a sound comparison of the data.
Soil properties were not reported for all BSAF values, but based on the reported data, it can be concluded that the BSAF values are derived in a wide range of soils and the data available can be considered as representative for soils in Europe:
Only CEC is significantly correlated with BSAF values. No significant correlation with Pb content, pH, Organic carbon content or clay content is observed. Because of the lack of any effect of Pb level in soil on the BSAF for Pb in earthworms, also data from Pb contaminated soils were included in the analysis.
Four field studies reported CEC data for the soils where earthworms have been sampled (Ma, 1982, Beyer et al., 1982, Ernst et al., 2008 and Nannoni et al., 2011). Correlations between BSAF and soil properties for individual studies are either non-significant or contradictory. The combined dataset shows a significant decrease of BSAF values with increasing eCEC (effective CEC) of the soil:
Log BSAF = -0.89 * log eCEC +0.55 R2= 0.16, P<0,01 (1)
The R2of this correlation is low, but the correlation is highly significant and one must notice that this regression is based on data from different studies, for 9 different earthworm species (anecic: Aporrectodea longa, Lumbricus terrestris; endogeic: Aporrectodea caliginosa, Aporrectodea rosea, Aporrectodea tuberculate, Octolasion cyaneum, Octolasion tyrtaeum; epigeic: Lumbricus rubellus, Dendrodrilus rubidus) and for a wide range of Pb levels and forms in soil (from natural and various anthropogenic sources). No clear distinction could be noticed between different ecological groups of earthworms.
In a recent laboratory study on the effects of soil type on the bioavailability and toxicity of lead salts to earthworms, the internal body concentrations and bioaccumulation factors for Pb were measured for Eisenia fetida exposed for 28 days to Pb in 6 different soils spiked with PbCl2(Lanno, 2012 and 2015,Table1). Bioaccumulation factors were determined forthe 2 test concentrations bracketing the EC10for reproduction of E. fetida in these soils.
Table1: Bioaccumulation factors for Eisenia fetida in different soils (expressed on a dry weight basis: kg dw/kg dw, each value is the average of 6 observations: 3 replicates for each of 2 test concentrations).
Total Pb (mg/kg)
Organic carbon (%)
pH in 0.01M CaCl2; eCEC= effective cation exchange capacity, i.e. CEC at pH of the soil; EC10 for reproduction of E. fetida.
The best regression between BSAF and soil properties for the dataset of Lanno (2015) was also found to be a linear regression of log-transformed BSAF values and log-transformed eCEC of the soils:
Log BSAF = -1.02 * log eCEC +0.23 R2= 0.70, P<0,05 (2)
Comparison of the regression based on the compiled field data (equation 1) and this regression for E. fetida exposed to Pb in soil under laboratory conditions (equation 2) yields the following observations:
The significant regression between log BSAF and log CEC is also consistent with the regression observed between toxicity of Pb toE. fetidareproduction and eCEC of the soil (see section 7.2 of the CSR).
Because of the significant effect of CEC of the soil on bioavailability and uptake of Pb by earthworms and because the relevance of the median BSAF value of 0.22 (dry weight basis) is not clear (unknown bias towards soils with high or low bioavailability as CEC is not reported for 134 out of 248 observations), it is concluded to implement the effect of soil properties by using the overall regression between log CEC and log BSAF (equation 1).
This yields a generic BSAF of 0.30 (dry weight basis) for the median eCEC value of 16 cmolc/kg soil for European natural soils (GEMAS, Geochemical Mapping of Agricultural and Grazing Land Soils;http://gemas.geolba.ac.at/; Reimann et al., 2014).
The conversion of dry weight to fresh weight is based on an average dry matter of 16% in earthworms (default value in EUSES, Jager 1998).
This yields a generic fresh-weight based BSAF of 0.048 for a soil with a median eCEC of 16 cmolc/kg soil and BSAF values of 0.089 and 0.028 for a soil with an eCEC of 8 and 30 cmolc/kg soil, respectively, corresponding to the 10thand 90thpercentile of eCEC in European arable soils.
A few literature data are available for bioaccumulation of Pb in isopods from soil or litter, 14 BSAFs were collected. Values range from 0.001-0.65 kgdw/kgdw. A median BSAF for isopods on a dry weight basis is 0.04 (median of 14 values).
Table: Bioaccumulation factors between soil or decomposed leaf litter and isopods. The Pb concentrations in the biota are the product of BAF and soil Pb concentration.
Soil/litter (mg Pb/kgdw)
15 adult specimen were exposed for 14 days to approximately 600 mL of air-dried experimental soil (polluted and remediated with 2.5, 10, 40 and 4 x 40 EDTA, respectively) in plastic vessels with plastic covers.
Udovic et al. 2009
polluted soil leached with 2.5 mmol kg-1EDTA
polluted soil leached with 10 mmol kg-1EDTA
polluted soil leached with 40 mmol kg-1EDTA
polluted soil leached with 4 x 40 mmol kg-1EDTA
Isopods were kept in plastic boxes on a moist gypsum base covered by decomposed leaf litter material, i.e. partly decomposed leaf litter material soaked in an aqueous solution of 100, 500 or 1000 mg l–1 Pb2+(as PbCl2).
Gräff et al. 1997
100 mg Pb/l
500 mg Pb/l
1000 mg Pb/l
Near a smelting complex a transect of 5 soil sampling sites was taken
0.3 km from the smelting complex
0.5 km from the smelting complex on the other side of the low hill
1 km from the smelting complex
2.5 km from the smelting complex
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