Soil Generic Assessment Criteria for Human Health Risk ... - ESdat

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Property Units Symbol Comment
Soil Water Partition
Coefficient
Dermal Absorption
Fraction
€
A coefficient relating to the partitioning of a substance between
the solid and aqueous phases used directly within the CLEA
cm 3 model. Literature values required for inorganic substances for
g K d
the plant uptake pathways, while the model estimates values
for organic substances based on K oc
and the soil organic matter
content.
A measure of the ability of a substance to desorb from soil adhered
to the skin and adsorb across the skin into the bloodstream.
- ABS d
In the absence of literature values SR3 recommends the use
of generic default ABS d
values; default values for organics and
inorganics are 0.1 and 0 respectively.
Selection of adopted values for each physico-chemical parameter was undertaken in general accordance with the
methodology set out in Section 1.2.2 (Review methodology), summarised in Table 1.4 of SR7. Ambiguities in the
Environment Agency of England and Wales method were interpreted by the Physico-Chemical Review Panel so that
a consistent approach has been used across all substances included in this report.
Proformas are available for each substance studied and are presented within Appendix B of this report. Each
proforma includes all of the individual data obtained for each property from each of the nine literature references
reviewed. Either the geomean or average of all values from each reference (in accordance with SR7) was also
calculated; these values are also included on the attached proformas. The adopted value for each property, along
with the selection rationale can also be found on the proforma.
Methodology
The aims of the physico-chemical data research were to follow the best available guidance on physico-chemical
selection as closely as possible while at the same time being transparent in the methods used. All of the values
found during the literature review process have been included on the attached substance specific proformas. The
adopted values, with included rationale for selection, are based on the Review Panel’s interpretation of the guidance
available in SR7. However, all of the data have been included on the proformas to enable the risk assessor using
these values to understand the range of values recorded for each individual parameter as well as choose a different
value that in their professional judgement is more appropriate for the specific circumstances of their assessment.
Where data were reported in the literature for a physico-chemical property at more than one reference temperature
(e.g. solubility), data reported at the temperature closest to the default ambient soil temperature used in the CLEA
model (i.e. 10°C) were recorded on the proforma.
Plant concentration factors for organic contaminants are estimated within the CLEA v1.06 model by the empirical
methods outlined within Chapter 7 of SR3, Updated Technical Background to the CLEA model (Environment Agency,
2009b). Due to limitations in volunteered time, it was considered beyond the scope of this project to undertake
appropriate research to derive plant concentration factors for the 3 inorganic substances covered (i.e. antimony,
barium and molybdenum). Where plant concentration factors were found for these inorganic substances they
have been recorded on their proformas for information purposes only. Plant concentration factors have not been
recommended for these substances and GAC have not been produced for the generic land uses that include the
plant uptake pathway (i.e. residential with consumption of homegrown produce or allotments).
The dermal absorption factors recommended in SR3, have been adopted in the derivation of GAC. A default value of
zero has been used for the metals and 0.1 has been used for the organics with the exception of 1-methylnaphthalene,
2-methylnaphthalene, 2,4-dinitrotoluene and 2,6-dinitrotoluene, which are listed in Table 8.2 of SR3 and have
values of 0.13, 0.13, 0.102 and 0.099, respectively.
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